Microbiology Exam 2

What are sterilants?

Destroy all microbes, including endospores and viruses. Are also called sporocides. Used to treat heat-sensitive critical instruments.

What are intermediate-level disinfectants?

Destroys all vegetative bacteria (including mycobacteria), as well as fungi, and most viruses, but they do not kill endospores. Used to disinfect non-critical instruments.

What are high-level disinfectants?

Destroys all viruses and vegetative microorganisms, but do not reliably kill endospores. Used to treat semicritical instruments.

What are low-level disinfectants?

Destroys fungi, vegetative bacteria (except Mycobacteria), and enveloped viruses, but they do not kill endospores, nor do they always destroy non-enveloped viruses. Used for disinfecting furniture, floors, and walls.

What is immunodeficiency?

Develop when the body cannot initiate or sustain an immune response. Can lead to malnutrition or fatigue. An example of this is AIDS. Is often hereditary.

What antimicrobial medications are used to treat Mycobacterium tuberculosis infections?

A group of four medications serve as first-line antibiotics. They are the most effective and the least toxic. They are given in combination for the first 8 weeks of treatment and then two are continued for another 18 weeks. This combination therapy decreases the chance that resistant mutants will develop, as, if some cells in the infection population spontaneously develop resistance to one medication, another will eliminate them. The second-line drugs are used for strains resistant to the first line drugs, but they are either less effective or are more toxic.

What is the Kirby-Bauer disc diffusion test?

A test routinely used to determine the susceptibility of a given bacterial strain to a variety of antimicrobial medications. A standard sample of the strain is first uniformly spread on the surface of an agar plate. Then, discs containing a known amount of a different antimicrobial are placed on the surface of the medium. During incubation, the drugs diffuse outward, forming a concentration gradient around each disc. The resulting zone of inhibition is compared with specially prepared charts to determine whether the strain is susceptible, intermediate, or resistant.

What are the characteristics and roles of T cells?

A type of lymphocyte. They active B cells and kill infected host cells.

What are the characteristics and roles of B cells?

A type of lymphocyte. They produce antibiotics.

What are adverse effects?

ALLERGIC REACTIONS: May be life-threatening or cause life-threatening systemic anaphylaxis. TOXIC EFFECTS: Several antibiotics are toxic at high concentrations. Patients taking these medications must be monitored because of the low therapeutic index. Some side effects are so severe or toxic that they are only used for life-threatening conditions or when no other options are available. DYSBIOSIS: An imbalance in the microbiome. Taking an antimicrobial can lead to this. Pathogens that are normally unable to compete can grow to high numbers.

How does reducing the available water preserve perishable products?

Accomplished by salting, adding sugar, or drying food. Adding sugar or salt increases environmental solutes, drawing the water our of cells, dehydrating them. Some bacteria grow in high salt concentrations (Staphylococcus aureus). Dried foods often have added salt, sugar, or preservatives. Lyophilization (freeze-drying) is widely used for preserving foods such as coffee, milk, meats, and vegetables. Drying stops microbial growth but does not reliably kill bacteria and fungi in or on foods.

What antimicrobial medications interfere with protein synthesis?

All cells make protein, so they have ribosomes. They are generally bacteriostatic. Prokaryotes have a 70S ribosome and eukaryotes have 80S ribosomes. The structure of the bacterial 70S ribosome is different enough from the eukaryotic 80S ribosome to make it a suitable target for selective toxicity. The mitochondria of eukaryotic cells have ribosomes similar to bacterial ribosomes, and this may account for the toxicity of some drugs.

What are hypersensitivities?

An exaggerated immune response that injures tissue. It is an overreaction to foreign antigens. Allergens are antigens that cause allergic reactions.

What is the use of ozone as germicidal chemicals?

An unstable form of oxygen. A powerful oxidizing agent. Used as an alternative to chlorine for disinfecting drinking water and wastewater.

What are β-lactam antibiotics (and other antimicrobials)?

Antibiotics that have a β-lactam ring and a high therapeutic index. Includes penicillins, cephalosporins, carbapenems, and monobactams. They interfere with peptidoglycan synthesis by inhibiting a group of enzymes called penicillin-binding proteins (PBPs). They are only effective against actively growing cells and vary in activity.

What is antimicrobial action?

Antimicrobial medications can be divided into two groups: BACTERIOSTATIC: Chemicals that inhibit bacterial growth. The patient must rely on his or her body's defense systems to kill or eliminate the pathogen after its growth has been stopped. An example of this are sulfa drugs. BACTERICIDAL: Chemicals that kill bacteria. Useful when the hosts defense cannot be relied on to eliminate pathogens. They may only be inhibitory sometimes when used at low concentrations or during certain stages of bacterial growth.

What is selective toxicity?

Antimicrobial medications that exhibit selective toxicity means that they cause greater harm to microbes than to their human hosts. They do this by interfering with essential structures of properties in microbes, but not in human cells. It is difficult with respect to antiviral medications because viruses rely on human cells for their replication. Toxicity is relative and is represented as the therapeutic index, which is the lowest dose toxic to the patient divided by the does used for therapy. A therapeutic window is the range between the therapeutic dose and the toxic dose. Medications that are far too toxic for systemic use may be used topically (to a body surface).

What is spectrum of activity?

Antimicrobial medications vary with respect to the range of microbes they kill or inhibit. BROAD-SPECTRUM: Affect a wide range of bacteria. They are important for treating acute life-threatening diseases when immediate antimicrobial treatment is essential and there is no time to culture and identify the pathogen. It disrupts the microbiome that helps keep out other pathogens, which puts the patient at risk of developing other infections. NARROW-SPECTRUM: Affect a limited range of bacteria. It is less disruptive to the microbiome, but it requires the identification and susceptibility of the pathogen. A patient may be started on a broad-spectrum antimicrobial and later switched to a narrow-spectrum once more is known about the pathogen.

What is tissue distribution/metabolism/excretion?

Antimicrobials differ in how they are distributed in tissues, metabolized, and excreted by the body. Only some can access the brain and only some can withstand stomach acid (low pH). If they are poorly absorbed from the intestinal tract, they must be administered by injection. The half-life of medication, which is the time it takes for serum concentration to decrease by 50%, dictates the frequency of doses required to maintain an effective level in the body. For example, patients with kidney or liver disfunction excrete or metabolize medications more slowly, so they must adjust the dosage to avoid toxic levels.

What is the role of TH cells in B-cell activation?

B cells are composed of four polypeptide chains - two duplicate copies of a heavy chain and two duplicate copies of a light chain. These chains are linked together by disulfide bonds and together create the characteristic Y-shaped structure with two identical arms and a stem. B cells receptors bind to an antigen, the B cell takes up the antigen and then degrades it into various peptide fragments. TH cells scan the peptides presented by B cells. If the TH cell's receptor binds to any of the presented peptides, the T cell then delivers cytokine to the B cell, activating it.

What are the two types of persistent infection?

CHRONIC: Characterized by the continuous low-level production of viral particles. Carriers may lack symptoms, but they can still transmit the virus. LATENT: The viral genome remains silent within a host cell, yet it can reactivate to cause a productive infection. The viral genome can be integrated into the host cell chromosome and is called a provirus. Other viruses replicate independently, much like a plasmid. The disease can recur even after an extended period without symptoms.

What are acute infections?

Characterized by the sudden onset of symptoms and a relatively short duration. It results in a burst of virions being released from infected host cells. The immune system gradually eliminates the virus over a period of days to months.

What is the chemical structure of viroids?

Consist solely of a small single-stranded RNA molecule that forms a closed ring. They are, thus far, only found in plants. Viroids only enter plants through wound sites rather than binding to specific receptors.

What are the effects of combinations?

Counteracting combinations are antagonistic, meaning they are medications that interfere with others.

What are the general characteristics of cell-mediated immunity?

Deals with invaders residing within a "self" cell, meaning within one of the body's own cells. The invaders include viruses and bacteria replicating within a self cell. It protects the host by killing cancerous cells or infected host cells, preventing the spread of infection. It protects against intracellular antigens. It involves TH and cytotoxic T cells (Tc cells). TH cells activate Tc cells to respond to antigens on infected host cells. Tc cells kill infected or altered host cells.

How do environmental conditions influence the selection of an antimicrobial procedure?

Dirt, grease, and body fluids interfere with heat penetration and chemical disinfectants. It is important to thoroughly clean items before disinfection or sterilization. Temperature and pH influence the effectiveness of disinfection techniques on microbial death rates.

What are the general characteristics of humoral immunity?

Eliminates microbial invaders and toxins that are not within a self cell, or, invaders in the blood or in tissue fluids. It protects against extracellular antigens. It involves B cells, which develop in the bone marrow in mammals. They are programmed to produce Y-shaped proteins called antibodies, which bind to specific antigens and mark them as an invader to be eliminated. TH cells activate B cells to yield antibody-producing plasma cells.

What is the process of clonal selection?

Explains how the adaptive immune system can respond to a seemingly unlimited range of antigens by using a pre-existing population of lymphocytes, each one already programmed to recognize a specific epitope on an antigen. When the immune system encounters a given antigen, only the lymphocytes that recognize it can multiply. Thus, the antigen determines which lymphocytes multiply. When antigen is introduced, only the B cells that have a B-cell receptor that binds the antigen have the possibility of becoming activated; other B cells remain inactive.

How does composition influence the selection of an antimicrobial procedure?

Heat treatment can damage many types of plastics and other materials. Irradiation also damages some plastics. Moist heat and liquid chemical disinfectants cannot be used to treat moisture-sensitive material.

What is resistance to antimicrobials?

INTRINSIC (INNATE) RESISTANCE: Certain organisms are inherently resistant to the effects of some antimicrobial medications. Ex. Mycoplasma species lack a cell wall, so they are intrinsically resistant to penicillin or other antimicrobials that interfere with peptidoglycan synthesis. Gram-negative bacteria are resistant to certain medications because their outer membrane prevents molecules from entering. ACQUIRED RESISTANCE: Refers tot the development of resistance in a previously sensitive organism. This occurs through spontaneous mutations or horizontal gene transfer.

What is naturally-acquired active immunity?

Immunity that results from an immune response in an individual after exposure to an infectious agent.

What is artificially-acquired active immunity?

Immunity that results from an immune response in an individual after vaccination.

What is artificially-acquired passive immunity?

Immunity that results when antibodies contained in the serum of other people or animals are injected into an individual.

What is naturally-acquired passive immunity?

Immunity that results when antibodies from a woman are transferred to her developing fetus during pregnancy or to an infant during breast feeding.

What are the key steps of inflammation?

Inflammation is triggered by basophils and mast cells. The damage to tissue causes basophils and mast cells to release histamine and other inflammatory mediators. Neutrophils are the first phagocytes recruited to the site. Phagocytic cells destroy and remove invaders. As the infection is brought under control, macrophages ingest dead cells and debris. Inflammatory mediators cause small blood vessels to dilate. The phagocytic cells tumble to a halt and then squeeze between the endothelial cells and enter the tissues.

Non-Enveloped Viruses

Lack a lipid envelope, meaning they are more resistant to disinfectants.

How are the minimum bacterial concentration (MBC) determined?

MBC is the lowest concentration of a specific antimicrobial medication that kills 99.9% of cells of a given bacterial strain in vitro. It is determined by finding out how many live bacterial cells remain in tubes from the MIC test that showed no growth. Specifically, it is determined from the plate count prepared from tubes with no growth in the MIC test.

What are the four general mechanisms of antimicrobial resistance?

MEDICATION-INACTIVATING ENZYMES: Bacteria that produce enzymes that interfere with the drug. One example is penicillinase, which is an enzyme that destroys penicillin. Other examples are extended-spectrum β-lactamases and carbapenemases, which inactivate many different β-lactam antibiotics. ALTERATION IN TARGET MOLECULE: Minor structural changes in the target can prevent the medication from binding, thereby protecting the organism from its effects. DECREASED UPTAKE OF THE MEDICATION: Changes in porin proteins can prevent certain antimicrobials from entering the cell's periplasm or cytoplasm. INCREASED ELIMINATION OF THE MEDICATION: Using efflux pumps to transport antimicrobials and other damaging compounds out of a cell. Structural changes in the pumps can influence the range of compounds that can be pumped out. Increased production or structural changes of pumps allow for faster removal. Sometimes, the organism can become resistant to several different antimicrobials simultaneously.

How are the minimum inhibitory concentration (MIC) determined?

MIC is the lowest concentration of a specific antimicrobial medication needed to prevent the visible growth of a given microbial strain in vitro. To do this, serial dilutions are used to generate decreasing concentrations of the medication in tubes containing a suitable growth medium. Cultures are added to each tube, and the tubes are then incubated. The tubes are then examined for turbidity (cloudiness), which indicates growth.

What are two examples of emerging antimicrobial resistance?

MYCOBACTERIUM TUBERCULOSIS: Can easily become resistant to first-line drugs through spontaneous mutation. Large numbers of cells are found in an active infection, so it is likely that at least one cell has developed spontaneous resistance to a drug, which is why combination therapy is required. A treatment of 6 months or more is necessary due to the slow rate of growth, but many patients do not comply. STAPHYLOCOCCUS AUREUS: Are the common cause of healthcare-associated infections. Most are now resistant due to their acquisition of a gene encoding penicillinase.

How does risk of infection influence the selection of an antimicrobial procedure?

Medical instruments are categorized according to their risk for transmitting infectious agents.

What are the characteristics and roles of macrophages?

Monocytes develop into macrophages. Macrophages stimulate lymphocytes to yield the adaptive immune response. They also detect tissue invaders and alert other components of the host defenses.

What are the six protective outcomes of antibody-antigen binding?

Neutralization, Opsonization, Complement system activation, Immobilization and prevention of adherence, Cross-linking, and Antibody-dependent cellular cytotoxicity.

What are viruses?

Obligate intracellular agents. They are genetic information, either DNA or RNA, that is contained within a protective protein coat. They are inert; they have no metabolism, they do not replicate, they are not motile. They are inert outside of cells, but inside, they direct the activities of the cell. Viruses are infectious agents, not organisms. They require live organisms as hosts.

What are the principles of preservation?

PRESERVATION: The process of delaying spoilage of perishable products. One way to do this is to choose storage conditions that slow microbial growth. Chemical preservatives can be added to a product. They are bacteriostatic, meaning that they inhibit the growth of bacteria, but do not kill them.

What are the hosts of prions and viroids?

PRIONS: Animals and humans. VIROIDS: Plants.

What is the role that proto-oncogenes and tumor suppressors in controlling cell growth?

PROTO-ONCOGENES: Stimulate cell growth and division. An ONCOGENE is a proto-oncogene that has been changed to promote uncontrolled growth. Numerous events, including spontaneous and induced mutations, can lead to conversion into an oncogene. TUMOR SUPRESSOR: Genes that inhibit growth and division.

What are the key steps of phagocytosis?

Phagocytes are recruited to the site of infection or damage. Various receptors on phagocytes bind invading microbes either directly or indirectly, tagging the microbe for destruction (phagocytosis). Once the phagocyte has attached to a particle, it sends out pseudopods that surround and engulf the material. The enzymes contributed by lysosomes or granules degrade various bacterial cell components, including peptidoglycan.

What are the primary responses to T-dependent antigens?

Primary exposure means activation of native B cells. It requires TH cells, meaning that it takes time. The disease progresses during this time, then the immune system clears the pathogens. IgM is mainly produced, then IgG.

What is the process by which prions accumulate in tissues?

Prions accumulate in neural tissue. Neurons die and brain function deteriorates as the tissues develop holes. The characteristic appearance gives rise to the general term for all prion diseases transmissible spongiform encephalopathies.

What is the chemical structure of prions?

Prions are composed only of protein (proteinaceous infectious agent). They have no nucleic acid. They are linked to slow, fatal diseases in humans and animals. Cells produce the normal form of neuronal protein PrP^C. Infectious prion proteins are PrP^SC. Appears that PrP^SC changes the folding of PrP^C, converting it to PrP^SC.

What is autoimmunity?

Results when the immune system mistakenly attacks the body's normal tissues. They attack the "self" in the absence of foreign antigens.

How can antimicrobial resistance be acquired?

SPONTANEOUS MUTATION: Mutations happen at a low rate during replication, but can have a significant effect. A single base-pair change in gene coding a ribosomal protein yields resistance to streptomycin. Spontaneous resistance to antibiotics with several different targets or multiple binding sites is less likely. GENE TRANSFER: Genes encoding resistance to antimicrobial medications can spread to different strains, most commonly through conjugative transfer of R plasmids. These plasmids carry several different resistant genes, so when an organism requires an R plasmid, it may become resistant to several different medications simultaneously. Resistance genes on R plasmids originate from spontaneous mutations or from microbes that naturally produce the antibiotic.

What are the secondary responses to T-dependent antigens?

Secondary exposure yields a more rapid response. Memory B cells are activated independent of TH cells. These memory cells divide, quickly yielding plasma cells. The rapid production of IgG (mostly) yields protection against disease. IgM responds first to the infection, then IgG takes over. The secondary response is much stronger than the primary response.

What are physical barriers?

Skin and mucous membranes and the chemicals that they secrete. Mucous membranes line the digestive tract, respiratory tract, and genitourinary tract, and they are constantly bathed with mucous or other secretions that help wash microbe from the surface.

What are antimicrobial substances?

Skin and mucous membranes are protected by a variety of substances that inhibit or kill microorganisms. For example, the salty residue that accumulates on skin as perspiration evaporates is inhibitory to all but salt-tolerant microbes. Lysozyme is an enzyme that degrades peptidoglycan and is in tears, saliva, and mucus. It is also found in phagocytic cells, blood, and the fluid that bathes tissues.

What are the TC cells (antigen recognition and response to the antigen)?

TC cells induce apoptosis in infected or "corrupt" self cells.

What are TH cells (antigen recognition and response to the antigen)?

TH cells orchestrate the immune response by activating B cells and macrophages by producing cytokines that direct the activities of other cells involved in the immune response.

What antimicrobial medication interfere with metabolic pathways?

The most useful are folate inhibitors (sulfonamides and trimethoprim). They inhibit different steps in the pathway that leads initially to the synthesis of folate and ultimately to the synthesis of a coenzyme that is required for nucleotide biosynthesis. Animals lack the enzymes to synthesize folate, which is why folate is required in the diet. SULFANOMIDES (SULFA DRUGS): They inhibit the growth of many Gram-positive and Gram-negative bacteria and are structurally similar to PABA, so the enzyme binds sulfa drugs instead of PABA. This is an example of competitive inhibition. TRIMETHOPRIM: Inhibits enzyme in a later step. It has little effect on the enzyme's counterpart in human cells. A combination of trimethoprim and sulfonamide has a synergistic effect.

What are normal microbiota?

The population of microorganisms that routinely grow on the body surfaces of healthy humans. They provide considerably protection. For example, they prevent pathogens from adhering to host cells by covering binding sites that might otherwise be used for attachment. The population also consumes available nutrients that could otherwise support the growth of less desirable organisms. Some members of the normal microbiota produce compounds toxic to other bacteria.

Decimal Reduction Time (D-Value)

The time in minutes required to kill 90% of a microbial population under specific conditions.

Mycobacterium Species

The waxy cell wall makes them resistant to many chemical treatments. Stronger, more toxic chemicals must be used to disinfect environments.

Why are T-independent antigens important medically?

These antigens do not require the assistance of TH cells to activate. T-independent antigens are not very immunogenic in young children, so children less than 2 years of age are more susceptible to pathogens.

What are the characteristics and roles of basophils?

They are involved in allergic reactions and inflammation and contain histamine and other chemicals involved with inflammation. They produce histamine to promote inflammation and stimulate the migration of phagocytes. They are important players in Type I hypersensitivities (allergic reactions).

What are the characteristics and roles of neutrophils?

They are phagocytes. They contain many destructive enzymes and antimicrobial substances. When a neutrophil engulfs microbes, the granule contents help destroy the microbes as part of the usual phagocytic process. They can also degranulate to kill nearby microbes, bursting in an area of infection to release not only the contents of their granules, but also cellular DNA. They are the most numerous and important granulocytes of the innate response, normally accounting for over half of the circulating leukocytes.

What are the characteristics and roles of mast cells?

They are similar in appearance and function to basophils. They are involved in allergic reactions and inflammation and contain histamine and other chemicals involved with inflammation. However, they are found in tissues instead of blood. They detect tissue damage and degranulates in response - an action that induces an inflammatory response.

What is the general features of a viral structure?

VIRION: A viral particle that is a nucleic acid that is surrounded by a protein coat, which is also called a capsid. They are either DNA or RNA, but not both, circular or linear, or single-stranded or double-stranded. A capsid is composed of simple identical subunits called capsomeres, and a capsid plus nucleic acids are called nucleocapsids. Enveloped viruses are surrounded by a lipid bilayer obtained from the host cell, and a matrix protein exists between the nucleocapsid and the envelope. A non-enveloped (naked) virus, is more resistant to disinfectants.

What is the importance of vaccination?

Vaccines not only protect an individual against disease, they may also prevent diseases from spreading in a population.

What is oncogenic viruses?

Viruses that can cause cancer in humans. They may arise as a direct result of viral infection, such as when a viral gene functions as an oncogene, or when the viral genome inserts into the host cell chromosome in such a way that a proto-oncogene is converted to an oncogene. Most virus-induced tumors are associated with certain DNA viruses, but some RNA viruses are also oncogenic. Cancers caused by the viruses do not develop immediately. A small percentage of oncovirus-infected people develop the associated cancer.

What are phages?

Viruses that infect bacteria. They are also called bacteriophages. They are easy to grow in the lab as a good model for how animal viruses interact with their hosts and are a vehicle for horizontal gene transfer.

What are oncolytic viruses?

Viruses that specifically target and kill cancer cells. They destroy the cancer cells directly by multiplying within them and causing lysis, while others act indirectly by stimulating the host's cancer-fighting immune cells.

How can the emergence and spread of antimicrobial resistance be slowed?

Will require cooperation from everyone globally. PHYSICIANS: Increase efforts to identify the cause of a given infection and prescribe suitable antimicrobials. PATIENTS: Carefully follow instructions even when it is inconvenient. Failure to complete treatment means that the least-sensitive organisms may not be killed, allowing for the subsequent spread of resistance. PUBLIC: People need to understand that antibiotics are not effective against viruses. This misuse only selects for antibiotic-resistant bacteria in the normal microbiota and they can eventually transfer R plasmids to pathogens.

Which of the following statements is true? a.) Acute infections of viruses are a result of productive infection. b.) Latent infections result from integration of viral nucleic acid into the host. c.) Latent infections are caused by repetitive infection of the same viruses. d.) Chronic infections of viruses generally lead to long-lasting immunity. e.) Acute infections usually followed by chronic infections.

a.) Acute infections of viruses are a result of productive infection.

The first antibiotic, penicillin, was discovered by: a.) Alexander Fleming. b.) Louise Pasteur. c.) Edward Jenner. d.) Joseph Lister. e.) Robert Koch.

a.) Alexander Fleming.

The hematopoietic stem cells in the bone marrow can develop into which of the following cell types? a.) Red blood cell. b.) All of these. c.) B cell. d.) Macrophage. e.) T cell.

b.) All of these.

Which concentration of alcohol is the most effective germicide? a.) 25%. b.) 5%. c.) 50%. d.) 75%. e.) 100%.

d.) 75%.

How does the overuse of antibiotic contribute to increasing numbers of antibiotic resistant bacteria? a.) None of these. b.) Antibiotic resistant bacteria are attracted to antibiotics for food. c.) Antibiotics accelerate bacterial mutations. d.) Antibiotics destroy or inhibit susceptible microbes, leaving the resistant microbes able to multiply without competition. e.) Antibiotic resistant bacteria produce antibiotics.

d.) Antibiotics destroy or inhibit susceptible microbes, leaving the resistant microbes able to multiply without competition.

All of the following are routinely used to preserve foods except: a.) High concentrations of sugar. b.) High concentrations of salt. c.) Desiccation. d.) Freezing. e.) Aldehydes.

e.) Aldehydes.

What are the five important factors to consider when selecting an appropriate germicidal chemical?

- TOXICITY: Benefits must be weighted against the risks of using the chemical. - Activity in the Presence of Organic Matter - Compatibility with a material being treated - RESIDUE: Some can be toxic or corrosive. - Cost and Availability - Storage and Stability - Environmental Risk

What is the use of alcohols as germicidal chemicals?

60 to 80% aqueous solutions of ethyl or isopropyl alcohol. Destroys vegetative bacteria, enveloped viruses, and fungi, but is not reliable against endospores and non-enveloped viruses. Denatures essential proteins and damages lipid membranes. Aqueous solutions are more effective than pure alcohol. Commonly used as antiseptics to clean skin before procedures and as disinfectants for treating instruments and surfaces. Are relatively non-toxic, inexpensive, and do not leave residue. Limitations include: Evaporate quickly, limiting contact time and effectiveness, and can damage rubber, some plastics, and other material. TINCTURE: Antimicrobial chemical dissolved in alcohol.

What are the principles of pasteurization?

A brief heat treatment usually applied to food items that reduces the number of spoilage organisms and destroys pathogens without changing the characteristics of the product.

What is the use of ethylene oxide gas as germicidal chemicals?

A gaseous sterilizing agent that destroys microorganisms and viruses by chemically modifying proteins and nucleic acids. It penetrates well into fabrics, equipment, and implantable devices. Useful for sterilizing heat or moisture sensitive items (plastic Petri dishes and pipettes). Applied in a special chamber that resembles an autoclave and can be sterilized in 3-12 hours. Limitations: Toxic, explosive, and potentially carcinogenic. It must be eliminated from the treated material using heated forced air.

What are the methods used to control microbial growth in microbiology laboratories?

All media and instruments that contact the culture must be sterilized to avoid contaminating the culture with environmental microbes. Materials must again be treated before disposal to avoid contaminating workers and the environment. This set of procedures is called aseptic technique.

What is the use of quaternary ammonium compounds as germicidal chemicals?

Are cationic (positively charged) detergents. Low toxicity and are used to disinfect food preparation surfaces. Pseudomonas resists the effects of quats and can even grow in solutions preserved with them.

What is the use of peroxygens as germicidal chemicals?

Are readily biodegradable and less toxic than traditional alternatives. HYDROGEN PEROXIDE: The effectiveness depends on the surface. Aerobic cells produce catalase, which inactivates hydrogen peroxide. Most effective on inanimate objects, doesn't damage most materials, and does not relieve residue. PERACETIC ACID: More potent than hydrogen peroxide. Used to sterilize items in less than an hour. Effective in the presence of organic compounds, leaves no residue, and can be used on a wide range of materials.

What is the use of biguanides as germicidal chemicals?

Chlorhexidine is the most effective. Reacts with the cell membrane to disrupt its integrity. Stays on the skin and mucous membrane, is of relatively low toxicity, and destroys vegetative bacteria, fungi, and some enveloped viruses.

What are the methods used to control microbial growth in water treatment facilities?

Chlorine has traditionally been used to disinfect water, preventing the spread of waterborne illnesses such as cholera. Some disinfectants, however, can react with naturally occurring chemicals to produce disinfection by-products (DBPs), some of which can be linked to long-term health risks. Facilities are required to minimize the level of DBPs and Cryptosporidium hominis in treated water.

Non-Critical Instruments and Surfaces

Come into contact only with unbroken skin, so they pose a low risk of transmission. Includes countertops, stethoscopes, and blood pressure cuffs.

Semicritical Instruments

Come into contact with mucous membranes but do not penetrate body tissue. Includes endoscopes and endotracheal tubes. Must be free of all microorganisms and viruses. Some endospores (low number and common ones), pose little risk because they can be blocked by mucous membranes.

Critical Instruments

Come into direct contact with body tissues. Includes needles and scalpels. These instruments must be sterile.

What are the principles of decontamination?

DECONTAMINATION: Reduces the number of pathogens to a safe level. The treatment can be as simple as thorough washing, or it may involve the use of heat or disinfectants.

What are the principles of disinfection?

DISINFECTION: The elimination of most or all pathogens on or in a material. Some viable microbes may remain. Disinfectants are chemicals used for disinfecting inanimate objects. They are toxic to many forms of life and are therefore biocides. Since they typically target harmful microbes, they are often called germicides. Antiseptics are antimicrobial chemicals that are non-toxic enough to be used on the skin or other body tissue.

What are the methods and outcomes of pasteurization?

Destroys heat-sensitive spoilage organisms in foods and beverages. Most pasteurization is by High-Temperature-Short-Time Method. This is for milk and ice cream. Shelf-stable boxed juice, single-serving containers of half-cream, and milk are pasteurized using Ultra-High-Temperature method. It destroys microorganisms that can grow under normal storage conditions.

What is the use of ultraviolet radiation in destroying microorganisms?

Destroys microbes directly by damaging their DNA. Used to destroy microbes in the air, water, and on surfaces. Has poor penetrating power (thin films or coverings can limit its effect, it cannot be used to destroy microbes in solid substances or turbid liquids, and most glass and plastic block out rays). Can also damage the skin and eyes and promote the development of skin cancers.

What is the use of microwaves in destroying microorganisms?

Do not effect microorganisms directly, but the heat they generate can be lethal. Heats unevenly, so even heat-sensitive cells can sometimes survive the process.

What are the methods and outcomes of boiling?

Easily destroys most microorganisms and viruses. It is not a method of sterilization because endospores can survive the process.

What is the use of gamma radiation for destroying microorganisms?

Harms cells directly by destroying DNA and damaging cytoplasmic membranes. Also reacts with O2 to produce Reactive Oxygen Species (ROS). Used extensively to sterilize heat-sensitive materials, including medical equipment, disposable surgical supplies, and drugs such as penicillin. Can generally be carried out after packaging.

What are the methods used to control microbial growth in food and food production facilities?

Heat treatment is the most common and reliable method to kill microbes, but it can alter flavor and appearance. Irradiation and high pressure can also be used without altering it. Chemical additives prevent growth, but risks toxicity (which must always be a concern). Food-processing facilities must always keep surfaces relatively free of microorganisms to avoid contamination.

How are HEPA filters used to remove microbes?

High-Efficiency Particulate Air filters. Removes nearly all airborne particles 0.3 micrometers or larger. Used for keeping microorganisms out of specialized hospital rooms designed for patients extremely susceptible to infection and in biological safety cabinets in which personnel work with airborne pathogens.

What are the methods and outcomes of dry heat?

INCINERATION: Destruction by burning. Oxidizes cell components to ashes. The wire loops used to transfer bacterial cultures are sterilized by flaming. They are also used to destroy medical wastes and contaminated animal carcasses. HOT AIR OVENS: Kill microbes by destroying cell components and denaturing proteins. Requires higher temperature and longer time than for moist heat because dry heat takes longer to penetrate and is less efficient at killing microbes.

How were antibiotics discovered?

In 1928, Alexander Fleming discovered the first antibiotic. He was working with cultures of Staphylococcus aureus when he noticed colonies growing near a contaminating mold looked as if they were dissolving. He recognized that the mold might be secreting a substance that killed the bacteria. He identified this mold as a species of Penicillium and found that it did secrete a bacteria killing substance, which he called penicillin. During World War II, several different penicillin's were found. Penicillin and its derivatives became important drugs.

What is the use of aldehydes as germicidal chemicals?

Includes glutaraldehyde and formaldehyde. Destroys microorganisms and viruses by forming chemical bonds that inactivate proteins and nucleic acids. 2% glutaraldehyde can be used as a common chemical sterilant. Immersion in this for 10-12 hours destroys all microorganisms and viruses. It is toxic so treated items must be thoroughly rinsed with sterile water. Formaldehyde is used as a gas or as formalin. Kills most microbes quickly and is used to kill bacteria and inactive viruses for use as vaccines. They are used to preserve biological specimens, but it is a probable carcinogen.

What is the use of metals as germicidal chemicals?

Kills by combining with sulfhydryl groups (-SH) of proteins, interfering with their function. High concentrations are too toxic to be used medically. Silver is used in creams and bandages.

How are new antimicrobial medications developed?

Most antimicrobial medications come from microorganisms that normally live in the soil, including species of Streptomyces and Bacillus (bacteria) and Penicillium and Cephalosporium (fungi). To commercially produce an antibiotic, a carefully selected strain of the appropriate species is grown in a vat of broth medium, and the antibiotic is extracted from the medium and purified. Altering the structure of antibiotics yields new medications. The development of new antimicrobial drugs is financially risky because the FDA demands strict and expensive testing. Pathogens are likely to develop resistance, and this lessens the return on investment. The use of new antimicrobial medications is sometimes limited because they are reserved as a last resort for treating certain severe infections, and this helps to lessen the development and spread of resistance, but it also lessens the financial rewards for companies to develop them.

What are the methods and outcomes of sterilization using pressurized steam?

Objects, such as surgical instruments, most microbiological media, and reusable glassware, are sterilized using an autoclave. These objects are heat and moisture tolerant. Higher pressure increases the temperature at which steam forms. It can kill endospores. Typical sterilization is 121 degrees Celsius (15 pounds per square inch in 15 minutes). Longer treatment is necessary for large volumes. To destroy prions, immersion in 1 molar NaOH during or before autoclaving. Steam must enter the item to displace air, so thin containers should be placed on either side and should not be closed tightly. Tape with a heat-sensitive indicator can confirm heating and turns black when at a high temperature. Biological indicators are used to ensure that an autoclave is working properly.

What is the use of halogens as germicidal chemicals?

Oxidizing agents which react and damage proteins and other essential cellular components. CHLORINE: Destroys all microorganisms, endospores, and viruses. Irritating to mucous membranes and skin, and is both corrosive and toxic. At low concentrations, it can be used to disinfect drinking water (does not kill Cryptosporidium oocysts, etc.). A 1:100 dilution of household bleach effective. Readily reacts with organic compounds and other impurities in water, disrupting its germicidal activity. IODINE: Kills vegetative cells, but does not reliably kill endospores. Used as a tincture in alcohol. Pseudomonas species survive in concentrated stock solution.

How are membrane filters used to remove microbes?

Paper thin. They have microscopic pores that allow liquid to flow through while trapping microbes and other particles too large to pass. A vacuum is commonly used to help pull the liquid through the filter. Has a small pore size (0.2 micrometer) that is commonly used to remove bacteria.

What are the methods used to control microbial growth in healthcare settings?

Patients in healthcare facilities, particularly hospitals, are often more susceptible to infectious agents because of their weakened condition. Pathogens are also more likely to be found in these settings because of the high concentration of patients with infectious diseases. Instruments and operating rooms must be sterile to avoid introducing microbes into deep body tissues where they could cause infection. Practices called Standard Precautions are used in patient care as a means to prevent infection of both patients and personnel. If a patient is, or might be, infected with a highly transmissible or epidemiologically important pathogen, Transmission-Based Precautions are used in addition.

What are the methods used to control the growth of microbes in other industries?

Pharmaceuticals, cosmetics, deodorants must avoid microbial contamination that could affect the product's quality or safety.

What is the use of phenolic compounds as germicidal chemicals?

Phenol (carbolic acid) was one of the earliest disinfectants. Has an unpleasant odor and irritates the skin. Destroys cytoplasmic membranes and denatures proteins. Kills most vegetative bacteria and, in high concentrations, can kill Mycobacterium species. Has a wide range of activity, reasonable cost, and ability to remain effective in presence of detergents and organic compounds.

How do chemical preservatives preserve perishable products?

Prevent or slow microbial growth and extend shelf life. Weak organic acids (benzoic, sorbic, and propionic acids) affect cell membrane function and inhibits mold. Nitrate and nitrite is used to inhibit the germination of endospores and subsequent growth of Clostridium botulinum. Can be carcinogenic.

BSL-4

Procedures for work with easily transmitted deadly pathogens.

BSL-1

Procedures for work with microbes not known to cause disease in healthy people.

BSL-2

Procedures for work with moderate-risk microbes that cause disease but have limited potential for transmission.

BSL-3

Procedures for work with pathogens that cause serious or potentially fatal disease through inhalation.

How does low-temperature storage preserve perishable products?

REFRIGERATION: Inhibits the growth of many pathogens and spoilage microorganisms by slowing or stopping critical enzyme reactions. Psychrotrophic and some psychrophilic organisms can grow. FREEZING: Preserves by stopping all microbial growth. Some microbial cells are killed by ice formation, but may survive and can grow once thawed.

Protozoan Cysts and Oocysts

Resistant to disinfectants. Appear in the feces of infected animals and can cause diarrheal disease if ingested. They are easily destroyed by boiling.

Pseudomonas Species

Resistant to some disinfectants and can actually grow in some of them.

How were antimicrobial medications discovered?

SALVARSAN: Discovered by Paul Ehrlich in 1910. It was the first documented case of a chemical used successfully as an antimicrobial medication. PRONTOSIL: Discovered 25 years later by German chemist Gerhard Domagk in 1932. It was used to treat streptococcal infections in animals. Prontosil had no effect on the growth of streptococci growing in test tubes. It was later discovered that the enzymes in an animals blood split the Prontosil molecule, which produces a molecule called sulfanilamide, which acted against streptococci. Sulfanilamide was the first sulfa drug discovered. BOTH: Both of these drugs are chemotherapeutic agents, which are chemicals that are used to treat diseases. Since they are used to treat microbial infections, they can also be referred to as antimicrobial medications, antimicrobial drugs, or antimicrobials.

What are the principles of sanitization?

SANITIZATION: Implies a process that substantially reduces the microbial population to meet accepted health standards that minimize the spread of disease. Sanitization does not indicate any specific level of control.

What are the principles of sterilization?

STERILIZATION: The removal or destruction of all microorganisms and viruses on or in a product. A sterile object is free of all viable microbes, including endospores. However, the term sterile does not consider prions, as they are not destroyed by standard sterilization procedures.

How does the type of microbe influence the selection of an antimicrobial procedure?

Some microbes are highly resistant to certain types of procedure. As such, they require more rigorous treatment.

What are the BSL levels for microbiology labs?

The U.S. Centers for Disease Control and Prevention (CDC) ahs established precaution guidelines known as biosafety levels (BSLs) for laboratories working with microorganisms.

How does the number of microbes influence the selection of an antimicrobial procedure?

The larger the population the more time it takes to destroy a microbial population. This is because only a fraction of cells or viral particles are destroyed during a given time interval. Removing most of the microbes by washing or scrubbing can minimize the time necessary to sterilize or disinfect a product. Scrubbing also helps to remove biofilms, which is important because organisms in a biofilm are more resistant to chemical disinfectants.

Bacterial Endospores

The most resistant forms of life. Only extreme heat or chemical treatment destroys them.

How are depth filters used to remove microbes?

Trap material within thick, porous filtration material such as cellulose fibers. The diameter of the passages is often much larger than that of microbes, but the electrical charges on the walls help to hold the microbial cells.

What is the use of high pressure in destroying microorganisms?

Used to decrease the number of microbes in some commercial food products like fruit juice an guacamole, without using high temperatures. Uses pressure up to 120,000 psi and is thought to destroy microbes by denaturing proteins and altering cell permeability. Keeps the color and flavor associated with fresh food.

What are the methods and outcomes of the commercial canning process?

Uses an industrial-sized autoclave called a retort. Designed to destroy all Clostridium botulinum endospores. If those endospores survived in a low-acid food, they can germinate and the resulting vegetative ells grow and produce botulinum toxin. Canned foods are commercially sterile, meaning that endospores of some thermophiles may survive, but they are usually not a concern because they only grow at temperatures well above those of normal storage. The higher the temperature, the shorter the time needed to kill all organisms. The higher the concentration of organisms, the longer the heat treatment required to kill them all.

What are the methods used to control microbial growth in daily life?

Washing and scrubbing with soaps and detergents achieves routine control. Soap does not destroy many microbes, but it aids in the mechanical removal of organisms. Regular handwashing does not harm the beneficial normal skin microbiota, as they reside more deeply on underlying layers of skin cells and hair follicles. Other ex. include: cooking foods, cleaning surfaces, and refrigeration.

Which of the following statements about antibodies is FALSE? a.) If you removed the Fc portion, antibodies would no longer be capable of binding antigens. b.) They participate in adaptive immunity. c.) They are Y-shaped proteins. d.) They are also called immunoglobulins (Igs). e.) They only bind to antigens that stimulated the production of such antibodies.

a.) If you removed the Fc portion, antibodies would no longer be capable of binding antigens.

Which of the following is false? a.) Quaternary ammonium compounds can be used to sterilize surgical instruments. b.) Standard sterilization procedures do not destroy prions. c.) Preservation inhibits the growth of microorganisms. d.) Pasteurization significantly decreases the number of spoilage microbes. e.) All of these are true.

a.) Quaternary ammonium compounds can be used to sterilize surgical instruments.

Why is it necessary to develop new generations of antimicrobial medications? a.) Scientists modify existing medication to extend their spectrum of activity. b.) All of these. c.) Microbes continually evolve, and in doing so they develop resistance to antimicrobial medications. d.) Scientists modify existing medication to make them stable to stomach acid. e.) Scientists modify existing medication to increase their half-life.

b.) All of these.

All of the following statements about autoimmune diseases are true EXCEPT: a.) May or may not involve infections. b.) Are caused by allergens. c.) Some are organ-specific and some are widespread in the body. d.) Some seem to have a genetic component. e.) Attack self-tissues.

b.) Are caused by allergens.

Lysozyme does which of the following? a.) Waterproofs skin. b.) Hydrolyzes bacterial peptidoglycan. c.) Propels the cilia of the respiratory tract. d.) Disrupts bacterial cell membranes. e.) Propels gastrointestinal contents.

b.) Hydrolyzes bacterial peptidoglycan.

Which class of antibody are found in sweat and mucus? a.) IgM. b.) IgA. c.) IgG. d.) IgD. e.) IgE.

b.) IgA.

Which of the following statements about inflammation is FALSE? a.) The process can damage host tissue. b.) Inflammation is an adaptive immunity response. c.) Vasodilation results in leakage of blood components. d.) The signs of inflammation are redness, swelling, heat, and pain. e.) Neutrophils are the first to migrate to a site of inflammation.

b.) Inflammation is an adaptive immunity response.

Many scientists have criticized the use of low-dosage antibiotics and other antimicrobial agents to enhance the growth of cattle and chickens. They against this practice for the following reasons except___________. a.) The practice will allow antibiotic genes enter surrounding soils and waters. b.) The practice allows producers to raise animals in a cost-effective manner. c.) Scientists are concerned that antibiotic-resistant strains of bacteria will show up in these animals as a result of the practice. d.) The practice will make it very difficult to control bacterial diseases spread through meat and poultry products.

b.) The practice allows producers to raise animals in a cost-effective manner.

Antimicrobials may lead to: a.) Reactions with foods and other medications. b.) Toxic effects. c.) All of these. d.) Allergic reactions. e.) Suppression of normal flora.

c.) All of these.

Which of the following statements about phagocytes is FALSE? a.) Phagocytes are special types of white blood cells. b.) Phagocytes are attracted to an area of infection by inflammatory mediators. c.) All phagocytes are macrophages. d.) Phagocytes routinely engulf and digest microbes and cell debris. e.) Phagocytes have receptors that recognize antibodies bound to bacteria.

c.) All phagocytes are macrophages.

Prions: a.) Contain only nucleic acid without a protein coat. b.) Replicate like HIV. c.) Cause diseases of humans. d.) Integrate their nucleic acid into the host genome. e.) Cause diseases of plants.

c.) Cause diseases of humans.

Ultraviolet light kills bacteria by: a.) Inhibiting protein synthesis. b.) Damaging cell walls. c.) Damaging DNA. d.) Generating heat. e.) Damaging cytoplasmic membranes.

c.) Damaging DNA.

Which of the following statements is TRUE? a.) An effector B cell can induce apoptosis in infected host cells. b.) In response to antigen, the B cells located close to the antigen begin dividing. c.) Each plasma cell is programmed to make a single specificity of antibody. d.) The cell type that makes and secretes antibody is called a cytotoxic cell. e.) A memory B cell has the potential to make more than one class of antibody.

c.) Each plasma cell is programmed to make a single specificity of antibody.

The target of the sulfonamides is: a.) Cytoplasmic membrane proteins. b.) Gyrase. c.) Folate synthesis. d.) RNA polymerase. e.) Peptidoglycan biosynthesis.

c.) Folate synthesis.

Which of the following targets would you expect to be the most selective with respect to toxicity? a.) 70S ribosome. b.) DNA synthesis. c.) Peptidoglycan synthesis. d.) Glycolysis. e.) Cytoplasmic membrane function.

c.) Peptidoglycan synthesis.

Select the FALSE statement regarding viruses and cancer. a.) The most common viral causes of tumors are certain DNA viruses such as hepatitis B virus. b.) Viruses that lead to cancer formation are called oncogenic viruses. c.) The majority of tumors are caused by oncogenic viruses but some may be caused by mutations in host genes that regulate cell growth. d.) Some viruses carry an oncogene—infection with these viruses interferes with the host cell's own growth-control mechanisms. e.) Viruses that insert their genome into the host cell's chromosome may cause changes at the insertion site, converting a proto-oncogene into an oncogene.

c.) The majority of tumors are caused by oncogenic viruses but some may be caused by mutations in host genes that regulate cell growth.

Why is Mycoplasma pneumoniae intrinsically resistant to β-lactam antibiotics? a.) The organism always carries β-lactamase. b.) None of these. c.) The organism does not have a cell wall, and therefore does not synthesize peptidoglycan. d.) The organism can effectively block the entrance of these drugs. e.) The organism has a specific efflux system to rapidly pump out the drugs.

c.) The organism does not have a cell wall, and therefore does not synthesize peptidoglycan.

Why would a hospital require a more stringent level of microbial control than daily home life? a.) Daily home life typically deals with healthy people. b.) Patients with infectious diseases can shed pathogens into the environment. c.) Patients are more susceptible to infectious agents because of their weakened condition. d.) All of these are true. e.) Patients are more susceptible to infectious agents because they may undergo surgery or other invasive procedures.

d.) All of these are true.

Which of the following statements is false? a.) A bacteriostatic chemical stops the growth of a microorganism. b.) A bactericidal agent kills bacteria. c.) Antimicrobial resistance may emerge through mutations. d.) Antimicrobial resistance may be induced by the use of an antimicrobial drug. e.) Antimicrobial resistance may emerge from acquisition of new genes.

d.) Antimicrobial resistance may be induced by the use of an antimicrobial drug.

Which of the following is the most resistant to destruction by chemicals and heat? a.) E. coli. b.) HIV virus. c.) Mycobacterium tuberculosis. d.) Bacterial endospores. e.) Fungal spores.

d.) Bacterial endospores.

Which antibody class is the first produced during a primary response? a.) IgD. b.) IgE. c.) IgG. d.) IgM. e.) IgA.

d.) IgM.

Capsids are composed of: a.) Lipids. b.) RNA. c.) DNA. d.) Proteins. e.) Polysaccharides.

d.) Proteins.

Aseptically boxed juices and cream containers are processed using which of the following heating methods? a.) High-temperature-short-time (HTST) method. b.) Commercial canning. c.) Autoclaving. d.) Ultra-high-temperature (UHT) method. e.) Boiling.

d.) Ultra-high-temperature (UHT) method.

Which of the following statements about autoclaving is false? a.) Cannot be used for items that must stay dry. b.) None of these is true. c.) Uses pressurized steam. d.) Can achieve temperatures above that of boiling water. e.) Allows survival of non-pathogenic bacteria.

e.) Allows survival of non-pathogenic bacteria.

All of the following could be used to sterilize an item except: a.) Irradiation. b.) All of them can sterilize. c.) Autoclaving. d.) Incineration. e.) Boiling.

e.) Boiling.

Why are non-enveloped viruses generally more resistant to disinfectants than are enveloped viruses? a.) Non-enveloped viruses have no proteins. b.) Enveloped viruses have its DNA directly surrounded by lipids. c.) Enveloped viruses have double capsids. d.) Non-enveloped viruses infect only plants. e.) Disinfectants damage the lipid bilayer of the envelope.

e.) Disinfectants damage the lipid bilayer of the envelope.

An antiseptic: a.) Sanitizes inanimate objects rather than sterilizes them. b.) Requires heat to be effective. c.) Destroys all microorganisms. d.) Can be used in food products. e.) Is non-toxic enough to be used on human skin.

e.) Is non-toxic enough to be used on human skin.

Vaccines ideally should be all of the following, EXCEPT: a.) Easily administered. b.) Inexpensive. c.) Effective in protecting against the disease. d.) Safe. e.) Living.

e.) Living.

Which of the following is the target of β-lactam antibiotics? a.) Protein synthesis. b.) DNA synthesis. c.) Folic acid synthesis. d.) RNA synthesis. e.) Peptidoglycan synthesis.

e.) Peptidoglycan synthesis.