Principles of Infection

Can be bacterial

Lyme disease: tick bites Rocky Mountain spotted fever: tick bites Typhus: lice bites Bubonic plaque: flea bites

Can be Protozoan

Malaria: bite of Anopheles mosquito Toxoplasmosis: ingestion of contaminated meat, inhalation of pathogen, and direct contact

Candida infections such as those seen in vaginal yeast infections in women after prolonged antibiotic therapy are due to which scenario?

Mutations, or changes, of normal flora

Neisseria gonorrhoeae

N-Methylphenyl-alanine pili, Gonorrhea

Organism

Adhesion factor, disease

Increased Microbial Virulence

Adhesion:presence of bacterial capsule and pili Colonization: spore formation, reproduction/replication of microbes Invasion: entry of large number of organisms into body Evasion of host defenses: viral mutation and replication Toxogenesis: production of exotoxins, endotoxins, and destructive enzymes

Direct contact

Human:touching, kissing, sexual intercourse, fecal-oral route (poor hygeine) Zoonoses: touching, biting, scratching

Which statement best explains the transmission of infectious disease from one host to another?

a chain of events leading with the reservoir and ending in the susceptible host occurs via different modalities

symbiosis

a close relationship between two different types of organisms that live together in a community: mutualism, commensalism, parasitism, or amensalism

immunocompromised system

any factors that suppress or weaken the immune system can enable opportunistic pathogens to cause infections and disease: acute and chronic diseases, malnutrition, stress, age, radiation and chemotherapy, immunosuppressive drugs

hyaluronidase

attacks connective tissue structure through breaking down hyaluronic acid

Electrostatic attraction

attractive or repulsive interaction between organisms with an electric charge; adhesion increases through attraction

Infectants survive by

avoiding contact with cells defenses, inhibiting engulfment by phagocytes, surviving inside phagocytes, producing toxins to damage defenses

Which is a method of transmitting pathogens from one host to another by carrying microorganisms inside the body and hosting their survival until transmission has occurred?

biologic vector

fleas

bubonic plague, endemic typhus

Transient flora

can be found in the same locations as the resident flora but only for a few hours, days, or months Bacillus latersorus-found in the intestines-regulate fungal populations streptococcal pneumoniae-can be seen on the skin

oppurtunistic pathogens

capable of causing infection and disease in vulnerable population

endotoxins (lipopolysaccharides)

carry their toxicity on the lipid tail of the chain, released when bacteria is damaged or destroyed

houseflies, face-flies, blow-flies

cause foodborne illness, dysentery, intestinal worms

cockroaches

cause foodborne illness, typhoid fever, viral diseases, human enteric protozoa

dung beetles

cause toxoplama gondii (toxoplasmosis)

Streptococcus pneumoniae

cell-bound protein, pneumonia

blood-sucking bugs

chagus disease

A 37-year-old diabetic patient who has recently lost his job has now been diagnosed with Epstein-Barr virus. Which could be the reason why his resistance is decreased to allow for invasion of the virus?

chronic disease, severe emotional stress

Which form of symbiosis is beneficial to one organism and neither harms nor benefits the other?

commensalism

Droplet transmission infections

common cold, influenza, pneumonia, pertussis

phospholipsases

destroys phospholipids of the plasma membrane

host resistance

determinant on the health of the individual and is a primary factor in determining risk of infection after exposure as seen in some infections

zoonoses

diseases that are primarily seen in animal but can be transmitted to humans by; contact with infected animal or animal waste, dust from contaminated hides, fur, feathers, ingestion of infected animal products, or insect vectors

Which is the most effective mode of transmission that is responsible for the spread of the common cold and influenza?

droplet transmission

lice

epidemic typhus

invasion

extracellular proteins or enzymes that have the ability to damage or destroy host cells they disrupt the host cell membrane and break down primary and secondary defense barriers facilitating growth and proliferation of the pathogen

Which are considered specific adhesion virulence factors?

fimbriae, cell-bound proteins

Bordetella pertussis

fimbriae, whooping cough

Which are considered vehicles for transmission of diseases that affect the gastrointestinal tract?

foodborne, waterborne

Non-Specific Adhesion

forces or interactions the microorganism uses to move toward the eukaryotic host include:

Reasons for nosocomial infections

happens to 10-15% of patients in hospital setting, reasons: presence of varying types of microorganisms, patients considered to be "contagious", overcrowding, use of contaminated instruments, immunocompromised and weakened patients, chain of transmission through staff, diagnostic procedures and equipment, therapeutic aids, and food trays, growing number of micropes resistant to multiple drugs

toxins

have the ability to cause sepsis, necrosis, and cell death

Which are examples of invasins that work to disrupt the host cell membrane?

hemolysin, stretolysin, hyaluronidase

hydrophobic interactions(water repelling)

increases propensity of adhesion; the more hydrophobic, the stronger the surface is to adhesion

A co-worker cannot determine how she contracted MRSA. The only thing she can think of is washing her son's wrestling uniform and towels after his practice. Which is the most likely mode of transmission?

indirect contact

Staphylococcus aureus (MRSA)

infections that are difficult to treat due to growing resistance to multiple antibiotic medications

Transmission

infectious organisms from one individual to another: reservoir has no obvious active infection in the acute stage or is asymptomatic, infectious agent is transferred directly or indirectly

Host resistance examples

intact skin and mucous membrane, body secretions--stomach acid, tears, nonspecific phagocytosis, effective inflammatory response, absence of disease, interferon production(virus)

Which is a group of signaling proteins produced by human host cells in an effort to boost immunity during a pathogenic invasion?

interferons

C. difficile

interrupts the distribution of normal flora allowing the bacteria to multiply causing severe diarrhea and ultimately death in some cases

Foodborne transmission

involves pathogens in or on foods that are improperly prepared: can occur due to parasitic worms, viruses hep A are also transmitted this way

Airborne Transmission

involves the spread of pathogens by droplet nuclei, and dust from reservoir to host: aerosols-coughing, sneezing, air conditioner, other cooling systems, pathogens attached to dust particles being stirred when cleaning

vectors

living organisms that carry disease in or on their bodies for transmission from one host to another

ticks

lyme disease, Rocky Mountain spotted fever

mosquitoes

malaria, yellow fever, elephantiasis, dengue, viral encephalitis, west nile virus

Which are considered factors that decrease host resistance?

malnutrition, immune senescene, severe emotional stress

Which concept describes how normal flora acts to protect the body against pathogens, because it occupies the same space, utilizes the same nutrients, and releases toxic waste products?

microbial antagonism

Recruitment and trapping by biofilms

microbial biofilms are complex bacterial communities often seen on implanted medical devices; they attract or recruit organisms for proliferation by altering the texture of the surface to meet the needs of the pathogen

Adhesion

most crucial virulence factor: bacterial occurs via pili, fimbriae, or specific membrane receptor sites----Viral occurs by using capsid or envelope proteins

colonization is caused by

motility ability as well as other means of contact with the host cell, adherence capability to host cell with resistance to physical removal, ability to invade the host cell and survive, ability to compete for iron and nutrients

Which factors affect pathogens' ability to colonize?

motility, adherence, ability to invade

chemotaxis

movement toward or away from a chemical stimulus

microbiota

normal flora intended to be there and are mostly beneficial to the body

Hospital-acquired infections (HAIs) or nosocomial infections

occur in health care facilities and are direct contact

Bodily Fluid Transmission

occur when contaminated bodily fluids are handled (mostly in health care setting): blood, urine, saliva

waterborne transmission

occurs due to untreated or poorly treated sewage: GI diseases--giardiases, amebic dysenter, cholera, shigellosis, leptospirosis, Fecal-oral infections--"Schistosoma" worms and enteroviruses

Colonization

occurs in human tissue that is exposed to the environment, such as the digestive, respiratory, and genitourinary tracts, as well as the conjunctiva of the eye

invasion into non-microbiota areas

often injury or displacement of normal flora into other areas of the body present vulnerability for opportunistic pathogens to cause infection or disease

Parasitism

one organism benefits and the other is harmed, either slightly or to such an extreme that the host is killed tuberculosis bacterium tapeworms

Which term describes an organism that causes disease or destruction of cells when the immune system is compromised?

opportunistic

Mechanical vectors

passively carry pathogens on their body (typically feet/legs) from one host to another

Which statement best explains why someone would be considered a germaphobe and not want to shake hands with others?

pathogens can be transmitted directly through handshaking

hemolysins

phospholipases destroy erythrocytes and other cells by lysis

E. coli, uropathogenic

pili, pyelonephritis

Brownian movement

random movement of microscopic particles suspended in a liquid or gas aids adhesion

Mutualism

relationship between two organisms in which both members benefit from the interaction Escherichia coli in human large intestine Probiotics

streptolysin

repels phagocytes while altering the membrane causing release of lysosomal granules

mites

scrub typhus

exotoxins

secreted by living bacteria act to damage cell membranes, inhibit protein synthesis, interfere with cell signaling, inhibit neurotransmitters, and alter immune response are secreted either directly through the cell membrane or with the help of an autotransporter

nonliving reservoirs

soil: provides optimal environment for survival and growth of pathogens such as fungi, helminths, and bacteria; due to fecal material can contain Clostridium botulinum, and C. tetani Water: can be contaminated with feces and urine may contain worm eggs, pathogenic protozoans, bacteria, and viruses Food: due to improper preparing and storing of foods

Which statement best defines virulence?

the ability of a microorganism to cause disease

pathogenicity

the ability of a microorganism to cause disease directly related to the number of infecting organisms, the portal of entry, host resistance, and the intrinsic characteristics along with their virulence factors

antigenicity

the ability to cause the production of antibodies

An older adult has recently been discharged from the hospital and has developed pneumonia, which has been attributed to her stay as an inpatient. Which statement would explain this?

the infection is a hospital-acquired infection

An article reads "tetanus due to injury involving soil infected with Clostridium tetani." Which statement about transmission of this pathogen can be considered to be true?

the pathogen was residing in a non-living reservoir

"case fatality rate"

the proportion of deaths in designated population of cases

human carriers

there are obvious infectious diseases that are easily identified and precaustions are put in place others are simply carriers and are asymptomatic but never become sick infect others without knowing they carry an infectious disease because they are immune to it

Atomic and molecular vibrations

this creates a force of attraction for pathogens

Indirect Contact

tissues and handkerchiefs, towels and linens, wrestling mats, toys, clothes, diapers, money, eating utensils and drinkware, medical equipment and devices, contaminated needles (HIV, Hep B and C)

Which type of virulence factor is secreted by living bacteria and acts to damage cell membranes and prevent protein synthesis?

toxin

Which are accurate statements regarding toxogenic virulence factors?

toxins can be secreted either directly or through the cell membrane, endotoxins carry toxicity on a lipid tail released when bacteria is damaged

An individual is experiencing issues related to a candida infection. Which describes the bacteria Bacillus laterosporus that can be given to this person to regulate the fungal population?

transient flora

Biological vectors

transmit pathogens but also serve as a host for part of the pathogens life cycle

common nosocomial infections include

urinary tract infections(most common), pneumonia, diarrhea, surgical wound infection

biologic therapy

used in cancer treatment the immune system is stimulated by interferons

Which are the correct modes of transmission for airborne, foodborne, and waterborne transmission?

vehicle

Droplet transmission

when infectious agents are transmitted through respiratory droplets released into the air traveling less than 1 meter: normal exhaling, laughing, coughing, sneezing (most common)

fomites

an inanimate object that came in contact with a pathogen that then infected a person/animal

Amensalism

an interaction between two species in which one organism can hamper to prevent the growth and/or survival of another, without being positively or negatively affected by the other organism penicillium

Which are considered reservoirs for zoonoses?

animals

Foodborne transmitted infections

Cholera: transmitted via ingestion of contaminated water, raw or partially cooked fish, or shellfish Gastroenteritis(Norwalk virus): transmits via ingestion of contaminated seafood and handling of contaminated food Salmonella: transmits via contaminated poultry, eggs, and meat

Specific water-borne infections

E. Coli: transmit via uncooked meat, food contaminated by fecal material; swimming in contaminated water Hepatitis A: transmit via contaminated food, water contaminated with human feces Samonellosis: transmit via contaminated poultry, eggs, and meat; fecal-oral route

Streptococcus mutans

Glycosyltransferase, Dental caries

Bodily Fluid transmitted infections

HIV/AIDS, hepatitis, and herpes

Treponema pallidum

Peptide in outer membrane, syphilis

Streptococcus pyogenes

Protein F, sore throat

These can be viral

Rabies:direct contact, bite, scratch Hantavirus pulmonary syndrome: inhalation of viruses from dried feces and urine or direct contact with rodent saliva, feces, or urine yellow fever: bite of Aedes mosquito

Can be Fungal

Ringworm: direct contact

Can be helminthic

Tapeworm infestation: ingestion of larvae transmitted in dog saliva Trichinellosis: ingestion of undercooked contaminated pork meat

interferons

a group of signaling proteins produced by human host cells in an effort to boost immunity in response to pathogenic invasion

specific adhesion

a lock-and-key interaction between complementary molecules on each cell surface is permanent and irreversible

reservoir

a place for a causative agent of infection to survive, can be animal, human, or nonliving agent

resident flora

a resident flora lives symbiotically in the body throughout the life of a person Staphylococcus epidermidis-resident of the skin E.coli--resident intestinal flora

Commensalism

a term used for a symbiotic relationship in which one of the organisms benefits and the other is neither harmed nor helped Saprophytic and mycobacteria Staphylococcus aureus

changes in normal flora

act to protect the body against pathogens as it occupies the same space, utilizes the same nutrients, and releases toxic waste products in "microbial antagonism": mutation of normal flora, hormonal changes, stress, changes in the diet, exposure to an excessive number of pathogenic organsims

Also relates to the ability of the microorganism to

adhere to host cells or tissues, colonize host cells, invade host cells, evade host defenses, produce toxins

Bordetella pertussis uses fimbriae in which type of virulence factor?

adhesion

Which virulence factor involves hydrophobic interactions and atomic and molecular vibrations?

adhesion

blood-sucking flies

african sleeping sickness, river blindness

Factors decrease host resistance

age, genetic susceptibility, immunodeficiency of any type, malnutrition, chronic disease, stress, compromised skin integrity, impaired inflammatory response, severe or multiple infections

Direct contact infections

agents causing respiratory tract infections, staphylococcal infections, measles, scarlet fever, sexually transmitted diseases