Microbial Mechanisms of Pathogenicity (BE #1) Flashcards
Describe 3 cases of symbiosis.
- commensalism: one organism benefits, the other is unaffected.
- mutualism: both organisms benefit. Ex. E. coli live in the large intestine of humans. They produce Vit. K that we use to make blood clotting factors.
- parasitism: host is harmed, microbe benefits.
What benefit do we gain from E. coli in the gut?
They produce Vit K which we use to make blood clotting agents.
Define parasite
Host is harmed, microbe benefits.
Does hand washing rid the body of its normal flora?
no, reduces it
Does hand washing rid the body of transient flora?
yes
Differentiate between contamination, infection & disease.
Contamination - microbes are present
Infections - multiplication of any parasitic organism; infection does not always cause disease
Disease - disturbance in the state of health; interferes with normal function
Name internal & external body surfaces that are inhabited by normal flora.
eyes, nose, mouth, pharynx, esophagus, trachea, colon, lower urethra, vagina
What is a nosocomial infection?
hospital-acquired infection
Name a common bacterial cause of nosocomial infections.
Staphylococcus aureus
Name 3 opportunities for infection by opportunistic bacteria.
- Disrupt normal flora w/antibiotics (ex. vaginal yeast infection)
- Improper hygiene (ex. colon flora causing a UTI from improper wiping)
- Neisseria meningitides from respiratory tract, causing meningitis
Why is it import for moms to breast feed (from a microbiologist’s perspective)?
Breast milk keeps the flora of the baby’s intestinal tract at a protective level. Bifidobacterium metabolizes milk sugars into acetic and lactic acid. This keeps the pH of the intestine inhospitable to many disease-causing microbes, most importantly those causing diarrhea.
Why would a prepubertal girl be at risk for STD’s? Why would a postmenopausal woman be at risk for increased vaginal yeast infections?
They are not (yet) producing estrogen which increases the growth of lactobacilli. Lacto keeps the vagina at an acidic level, which is inhospitable to disease-causing microbes.
A place where a pathogenic microorganism is maintained between infections -
reservoirs
A healthy person who is a reservoir can be called:
a carrier
Give 3 examples of environmental reservoirs.
soil - Clostridium tetani
water - Vibrio cholera
food - Clostridium botulinum
house dust
Differentiate between an incubatory carrier & a chronic carrier.
Incubatory - a person is contagious during the early symptomless period of the disease
chronic - person who harbors a pathogen for an extended period of time w/o becoming ill
Give example of pathogen that uses soil as a reservoir. What enables it to survive?
Clostridium tetani
endospore former
Give example of pathogen that uses dust as a reservoir. How can it survive in such dry conditions?
Mycobacterium tuberculosis
waxy envelope
Pathogen that uses water as a reservoir.
Vibrio cholerae
Pathogen that uses food as a reservoir.
Clostridium botulinum
Define zoonosis and give 3 examples of diseases that use animals as reservoirs.
Human disease caused by pathogens that maintain an animal reservoir.
Rabies, Lyme disease, West Nile virus, Hantavirus
Differentiate between ID50 and LD50.
ID50 is the infection dose. The # of microbes that must enter the body to establish infection in 50% of test animals
LD50 is the lethal dose. The # of microbes that must enter the body to cause death in 50% of test animals.
Which is more pathogenic? Bacterium A = ID50 of 200. Bacterium B = ID 50 of 100
Bacterium B - takes fewer bacterial cells to establish infection.
What is the microbe that causes a specific disease?
etiologic agent
