Microbes and disease chapter 15

Molecular Koch's Postulates(3)

(1) The phenotype (sign or symptom of disease) should be associated only with pathogenic strains of a species. (2) Inactivation of the suspected gene(s) associated with pathogenicity should result in a measurable loss of pathogenicity. (3) Reversion of the inactive gene should restore the disease phenotype.

Incubation period duration

1-2 days in acute diseases or months to years in chronic disease

Highly virulent and less virulent pathogens(3)

-Highly virulent pathogens lead to a disease state and some may even cause multi-organ and body system failure in healthy individuals. - Less virulent pathogens may cause an initial infection, but may not always cause severe illness. -Pathogens with low virulence would more likely result in mild signs and symptoms of disease, such as low-grade fever, headache, or muscle aches. Some individuals might even be asymptomatic.

How large are cells?

10 micrometers

Inherited non infectious disease

A genetic disease, sickle cell anemia

syndrome

A specific group of signs and symptoms characteristic of a particular disease

Example of a highly virulent microorganism(7)

Bacillus anthracis, the pathogen responsible for anthrax. B. anthracis can produce different forms of disease, depending on the route of transmission (e.g., cutaneous injection, inhalation, ingestion). The most serious form of anthrax is inhalation anthrax. After B. anthracis spores are inhaled, they germinate. An active infection develops and the bacteria release potent toxins that cause edema (fluid buildup in tissues), hypoxia (a condition preventing oxygen from reaching tissues), and necrosis (cell death and inflammation). Signs and symptoms of inhalation anthrax include high fever, difficulty breathing, vomiting and coughing up blood, and severe chest pains suggestive of a heart attack. With inhalation anthrax, the toxins and bacteria enter the bloodstream, which can lead to multi-organ failure and death of the patient. If a gene (or genes) involved in pathogenesis is inactivated, the bacteria become less virulent or nonpathogenic.

Idiopathic noninfectious diseases

Disease for which the cause is unknown

Congenital noninfectious disease

Disease that is present at birth or before, down syndrome

Which periods of disease are more likely to associated with transmissibility of an infection depends upon the

Disease, pathogen and the mechanisms by which the disease develops and progresses

The WHO and ICD is used in clinical fields to classify ...

Diseases and monitor morbidity, number or cases, and mortality, number of deaths.

asymptomatic or subclinical diseases

Do not present any noticeable signs or symptoms

Transmission of Disease(3)

For a pathogen to persist, it must put itself in a position to be transmitted to a new host, leaving the infected host through a portal of exit ( Figure 15.9). many pathogens are adapted to use a particular portal of exit. Similar to portals of entry, the most common portals of exit include the skin and the respiratory, urogenital, and gastrointestinal tracts. Coughing and sneezing can expel pathogens from the respiratory tract

nutritional deficiency noninfectious diseasw

Impaired body function due to lack of nutrients, scurvy

types of noninfectious diseases (7)

Inherited Congenital Degenerative Nutritional deficiency Endocrine Neoplastic Idiopathic

Molecular Koch's Postulates created by Stanley falkow

Premise is not in the ability to isolate a particular pathogen but rather to identify a gene that may cause the organism to be pathogenic

Second name of the pathogen stands for the

Species epithet

What is wrong with Koch's second postulate? (4)

Koch also assumed that all pathogens are microorganisms that can be grown in pure culture (postulate 2) and that animals could serve as reliable models for human disease. we now know that not all pathogens can be grown in pure culture, and many human diseases cannot be reliably replicated in animal hosts. Viruses and certain bacteria, including Rickettsia and Chlamydia, are obligate intracellular pathogens that can grow only when inside a host cell. If a microbe cannot be cultured, a researcher cannot move past postulate 2 Also ethical issues of having to infect a human host

What surfaces are the most important portals of entry for microbes? (2)

Mucosal surfaces;these include the mucous membranes of the respiratory tract, the gastrointestinal tract, and the genitourinary tract. Although most mucosal surfaces are in the interior of the body, some are contiguous with the external skin at various body openings, including the eyes, nose, mouth, urethra, and anus.

Adhesion

Pathogen adheres at the portal of entry, refers to the capability of pathogenic microbes to attach to the cells of the body using adhesion factors,

prodromal period(2)

Pathogen continues to multiply and the host experiences general signs and symptoms of illness - results from activation of the immune system such as fever and pain

The duration of the period of illness can vary greatly depending on the

Pathogen, effectiveness of the immune response in the host, and any medical treatment received

Microorganisms that can cause disease are

Pathogens

Paraenteral route

Pathogens can also enter through a breach in the protective barriers of the skin and mucous membranes. Ex)For example, the skin is a good natural barrier to pathogens, but breaks in the skin (e.g., wounds, insect bites, animal bites, needle pricks) can provide a parenteral portal of entry for microorganisms.

Chronic disease (2)

Pathologic changes can occur over longer time spans: months years or a lifetime - ex: chronic gastritis caused by gram- negative bacterium helicobacter pylori h pylori

Acute disease (2)

Pathologic changes occur over relatively short time hours days or weeks and involve a rapid onset of disease conditions -ex) influenza caused by influenzavirus, incubation period is 1-2 days, transmit to other host in 5 days, 1 week before symptoms decline

outbreak(2)

The occurrence of more cases of disease or health condition than expected in a given area or amoung a group of people during a specific period - cases have common causes and are related in some way.

What are Koch's postulates? (4)

The suspected pathogen must be found in every case of disease and not be found in healthy inidividuals The suspected pathogen can be isolated and grown in pure culture A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease as seen in postulate 1. The pathogen must be re-isolated from the new host and must be identical to the pathogen from postulate 2.

Pathogenicity

ability of a microbial agent to cause disease

Nosocomial disease (4)

acquired in hospital settings Several factors contribute to the prevalence of it: 1: sick patient brings it into hospital and pathogens are transmitted easily via sterilized medical equipment 2: hospital patients have weakened immune systems

Commensalism

one organism benefits and the other is not affected Ex) staphylococcus epidermis is of the skin

Other members of the normal micro bats can also cause ____(2)

opportunistic infections when microbes that reside harmlessly in one body location end up in a different body system, where they cause disease. For example, E. coli normally found in the large intestine can cause a urinary tract infection if it enters the bladder. This is the leading cause of urinary tract infections among women.

Periods of disease

incubation, prodromal, illness, decline, convalescence

systemic infection(2)

infection becomes disseminated throughout the body, For example, infection by the varicella-zoster virus typically gains entry through a mucous membrane of the upper respiratory system. It then spreads throughout the body, resulting in the classic red skin lesions associated with chickenpox. Since these lesions are not sites of initial infection, they are signs of a systemic infection.

Zoonotic diseases (zoonoses) (2)

infectious diseases that humans acquire from animal sources or by all animals - ex: rabies is a viral zoonotic disease spread through bites and contact with infected saliva

Virulence of a pathogen can be quantified using controlled experiments with laboratory animals. What are two important indicators of virulence? (4)

median infectious dose (ID50) and the median lethal dose (LD50), both of which are typically determined experimentally using animal models. The ID50 is the number of pathogen cells or virions required to cause active infection in 50% of inoculated animals. The LD50 is the number of pathogenic cells, virions, or amount of toxin required to kill 50% of infected animals.

Period of illness

most severe and obvious signs and symptoms

Local infection(2)

confined to a small area of the body, typically near the portal of entry. -For example, a hair follicle infected by Staphylococcus aureus infection may result in a boil around the site of infection, but the bacterium is largely contained to this small location

iatrogenic disease(2)

contracted as the result of a medical procedure - skin patient treated for a skin wound might acquire necrotizing fasciitis

noncommunicable infectious disease(2)

not spread from person to person, Ex: tetanus caused by clostridium tetani transmitted through contact with a skin wound

Infectious diseases are caused by

pathogenic microorganisms, such as bacteria viruses parasites or fungi- the disease can be spread directly or indirectly from one person to another

Most pathogens are suited to a particular (3)

portal of entry. A pathogen's portal specificity is determined by the organism's environmental adaptions and by the enzymes and toxins they secrete. The respiratory and gastrointestinal tracts are particularly vulnerable portals of entry because particles that include microorganisms are constantly inhaled or ingested, respectively.

The actual infective dose for an individual can vary depending on which factors? (2)

route of entry; the age, health, and immune status of the host; and environmental and pathogen-specific factors such as susceptibility to the acidic pH of the stomach. It is also important to note that a pathogen's infective dose does not necessarily correlate with disease severity.

Infection (2)

successful multiplication of the pathogen leads to infection. Infections can be described as local, focal, or systemic, depending on the extent of the infection

During phagocytosis some pathogens have the ability to (2)

survive and multiply within phagocytes. -Examples include Listeria monocytogenes and Shigella; these bacteria produce proteins that lyse the phagosome before it fuses with the lysosome, allowing the bacteria to escape into the phagocyte's cytoplasm where they can multiply.

primary infection(3)

the initial infection caused by one pathogen, can lead to a secondary infection by another pathogen For example, the immune system of a patient with a primary infection by HIV becomes compromised, making the patient more susceptible to secondary diseases like oral thrush and others caused by opportunistic pathogens. Some secondary infections can even develop as a result of treatment for a primary infection. Antibiotic therapy targeting the primary pathogen can cause collateral damage to the normal microbiota, creating an opening for opportunistic pathogens

Period of decline (2)

the number of pathogen particles begins to decrease, and the signs and symptoms of illness begin to decline Patient may become susceptible to developing secondary infections because their immune systems have been weakened

Which individuals are susceptible to opportunistic infections?

the very young, the elderly, women who are pregnant, patients undergoing chemotherapy, people with immunodeficiencies (such as acquired immunodeficiency syndrome [AIDS]), patients who are recovering from surgery, and those who have had a breach of protective barriers (such as a severe wound or burn).

Some host cells such as (2)

white blood cells and other phagocytes of the immune system, actively endocytose pathogens in a process called phagocytosis. the host cell kills and degrades the pathogen by using digestive enzymes. Normally, when a pathogen is ingested by a phagocyte, it is enclosed within a phagosome in the cytoplasm; the phagosome fuses with a lysosome to form a phagolysosome, where digestive enzymes kill the pathogen

Infectious disease

A disease caused by a direct effect of a pathogen

what can not cause a disease?

Physical injuries or disability are not classified as disease

Stages of Pathogenesis( to successfully cause disease) 4

1. Exposure 2. Adhesion 3. Invasion 4. Infection

Exposure

An encounter with a potential pathogen is known as exposure or contact. The food we eat and the objects we handle are all ways that we can come into contact with potential pathogens.

Neoplastic noninfectious disease

Abnormal growth, some forms of cancer

Infectious diseases can be contagious during which stages of disease?

All of them

Disease

Any conditions in which the normal structure or functions of the body are damaged or impaired

Symptoms

Are subjective and cannot be clinically confirmed or objectivity measured

Why don't algae infect us?

Because they are photogenic

What growth can act as an adhesion factor? (3)

Biofilm growth- community of bacteria that produce a glycocalyx, known as extrapolymeric substance (EPS), that allows the biofilm to attach to a surface. The EPS allows the bacteria to adhere to the host cells and makes it harder for the host to physically remove the pathogen. - also protection against the immune system and antibiotic treatments, preventing antibiotics from reaching the bacterial cells within the biofilm

Vital signs include what?(5)

Body temperature Respiratory rate Heart rate Blood pressure Measure the body's basic functions

communicable infectious disease(3)

Capable of being spread from person to person through either direct or indirect mechanisms Some may be considered contagious diseases - easily spread from person to person

Latent diseases

Causal pathogen goes dormant for extended periods of time with no active replications - herpes, chickenpox

A pathogen may be either: (2)

Cellular: bacteria, protists and fungi , archaea Acellular: viruses, viroids and prion, virusoids

What did Robert Koch do?

Created a systematic approach for confirming causative relationships between diseases and specific pathogens

Portal of entry involved in exposure (3)

For a pathogen to cause disease, it needs to be able to gain access into host tissue. An anatomic site through which pathogens can pass into host tissue is called a portal of entry. These are locations where the host cells are in direct contact with the external environment. Major portals of entry are identified in Figure 15.6 and include the skin, mucous membranes, and parenteral routes.

What are some vehicles for pathogens to leave the body (2)

Feces, urine, semen, vaginal secretions, tears, sweat, and shed skin cells Pathogens that rely on insect vectors for transmission exit the body in the blood extracted by a biting insect. Similarly, some pathogens exit the body in blood extracted by needles

First word of pathogen stands for the

Genus

Faulty assumption of Koch's postulate? (6)

He believed all healthy test subjects are equally susceptible to disease- not true. The makeup of the resident microbiota can influence an individual's susceptibility to an infection. Members of the normal microbiota play an important role in immunity by inhibiting the growth of transient pathogens. the microbiota may prevent a pathogen from establishing an infection; in others, it may not prevent an infection altogether but may influence the severity or type of signs and symptoms. As a result, two individuals with the same disease may not always present with the same signs and symptoms. In addition, some individuals have stronger immune systems than others.

The degree to which a disease is contagious usually depends on

How the pathogen is transmitted

Invasion (4)

I the dissemination of a pathogen throughout local tissues or the body. -Pathogens may produce exoenzymes or toxins, which serve as virulence factors that allow them to colonize and damage host tissues as they spread deeper into the body. -Pathogens may also produce virulence factors that protect them against immune system defenses. -A pathogen's specific virulence factors determine the degree of tissue damage that occurs.

For most infectious diseases what is the critical step in finding effective treatment?

Identifying the causative pathogen

What causes a disease? (4)

Infection by a pathogen Genetics Noninfectious environmental causes Inappropriate immune response

Like noncommunicable infectious diseases, non infectious disease are an important cause of (3)

Morbidity and mortality worldwide - NID can be caused by genetics, the environment, and immune system dysfunction —-ex) sickle cell anemia

Endocrine noninfectious disease

Malfunction of glands Hypothyroidism

Adhesions (4)

Molecules (either proteins or carbohydrates) found on the surface of certain pathogens and bind to specific receptors (glycoproteins) on host cells. Adhesins are present on the fimbriae and flagella of bacteria, the cilia of protozoa, and the capsids or membranes of viruses. Protozoans can also use hooks and barbs for adhesion; spike proteins on viruses also enhance viral adhesion. The production of glycocalyces (slime layers and capsules) with their high sugar and protein content, can also allow certain bacterial pathogens to attach to cells.

Acellular means? And cellular means?

No cells, made of cells

What is uncertain about Koch's first postulate? (2)

Not true as found in modern microbiology, Ex:H. Pylori causes chronic gastritis and is apart of the normal microbiota in a healthy persons stomach

Signs of a disease

Objective and measurable and can be directly observed by a clinician

incubation period(3)

Occurs in an acute disease after the initial entry of the pathogen into the host - pathogen begins to multiply in the host - insufficient numbers of pathogen particles to cause signs and symptoms

Parasitism

One organism benefits and the other is harmed H1N1 virus particles on a host cell

How are pathogens classified? (2)

Primary pathogen: can cause disease in a host regardless of the hosts resident microbiota or immune system opportunistic pathogen: can only cause disease in situations that compromise the host's defenses, such as the body's protective barriers, immune system, or normal microbiota

Degenerative noninfectious disease

Progressive irreversible loss of function, Parkinson's disease

Factors involved in determining the length of the incubation period are

Strength of the pathogen, strength of host immune defenses, site of infection, type of infection and size infectious dose Patient is unaware that a disease is present

Virulence (3)

The degree to which an organism is pathogenic -a continuum - On one end of the spectrum are organisms that are avirulent (not harmful) and on the other are organisms that are highly virulent.

Infection(2)

The successful colonization of a host by a microorganism Can lead to disease which causes signs and symptoms resulting in deviation from normal structure

What can also be other observable conditions that may be considered signs of disease?

The presence of antibodies in a patients serum which can be measured through blood tests

Bacterial pathogens associated with diarrheal disease include (4)

Vibrio cholerae Listeria monocytogenes Campylobacter jejuni EPEC

focal infection(2)

a localized pathogen, or the toxins it produces, can spread to a secondary location. -For example, a dental hygienist nicking the gum with a sharp tool can lead to a local infection in the gum by Streptococcus bacteria of the normal oral microbiota. These Streptococcus spp. may then gain access to the bloodstream and make their way to other locations in the body, resulting in a secondary infection.

Members of the normal microbiota may also cause disease when (3)

a shift in the environment of the body leads to overgrowth of a particular microorganism. For example, the yeast Candida is part of the normal microbiota of the skin, mouth, intestine, and vagina, but its population is kept in check by other organisms of the microbiota. If an individual is taking antibacterial medications, however, bacteria that would normally inhibit the growth of Candida can be killed off, leading to a sudden growth in the population of Candida,

period of convalescence

body systems return to normal, some disease may inflict permanent damage

Mutualism

both organisms benefit E. coli bacteria in the large intestine

How can an intracellular pathogen enter a hosts cell? (5)

endocytosis. two different mechanisms for endocytosis and entry. -One mechanism relies on effector proteins secreted by the pathogen; these effector proteins trigger entry into the host cell. ——This process is called membrane ruffling. -The second mechanism relies on surface proteins expressed on the pathogen that bind to receptors on the host cell, resulting in entry

How to intracellular pathogens achieve invasion? (3)

entering the host's cells and reproducing. able to evade some mechanisms of the immune system while also exploiting the nutrients in the host cell. obligate intracellular pathogens (meaning they can only reproduce inside of host cells) facultative intracellular pathogens (meaning they can reproduce either inside or outside of host cells).

Example of a primary pathogen and opportunistic pathogen (5)

enterohemorrhagic E. coli ( EHEC), which produces a virulence factor known as Shiga toxin. This toxin inhibits protein synthesis, leading to severe and bloody diarrhea, inflammation, and renal failure, even in patients with healthy immune systems. Staphylococcus epidermidis, on the other hand, is an opportunistic pathogen that is among the most frequent causes of nosocomial disease.5 S. epidermidis is a member of the normal microbiota of the skin, where it is generally avirulent. However, in hospitals, it can also grow in biofilms that form on catheters, implants, or other devices that are inserted into the body during surgical procedures. Once inside the body, S. epidermidis can cause serious infections such as endocarditis, and it produces virulence factors that promote the persistence of such infections.