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Medical Microbiology > Lecture 4: Normal Flora > Flashcards

Lecture 4: Normal Flora Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Normal vs. transient flora?

A

Normal Flora: Organisms regularly found at any anatomical site

Transient Flora: Inhabit for relatively short period of time

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2
Q

True or False: You can be a carrier of transient flora and, as such, spread it to others

A

True
- many pathogens are transient flora

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3
Q

Anatomic distribution is determined by ______, which is the specific adherence between host’s receptor and microorganism’s ligand/adhesion

A

tissue specificity

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4
Q

Organ or tissue _____ reflects the ability of a given pathogen to infect a specific organ or sets of organs.

A

tropism

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5
Q

Which five environmental conditions shape the micro-environment of the anatomical site

A

pH
O2 tension
competition
inhibitory factors
substrate availability

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6
Q

___ is the key for maintaining Natural Flora in a good relationship with the host

A

Homeostasis

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7
Q

List a few host-specific factors that contribute to the composition of one’s natural flora:

A

1) Gender
2) Lifestyle
3) Genetics
4) Nutrients/Diet
5) Age
6) Health

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8
Q

True or False: Different natural flora at the SAME anatomical site in different people could have different effects and outcome

A

True

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9
Q

Which five sites of the human body are normally sterile?
(Hint: BLUCS)

A
  1. Uterus + internal organs
  2. Synovial fluid
  3. CSF
  4. Blood
  5. Lower respiratory tract
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10
Q

True or False: One of the benefits of normal flora is that it can stimulate the innate immune system, without stimulating the adaptive immune system

A

False - one of the benefits of normal flora is that it can stimulate BOTH innate and adaptive immune system

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11
Q

Lactobacilli in the vaginal mucosa produce ___, which reacts with the host cell myeloperoxidase to make ____, which inhibits or kills other bacteria

A

H2O2; HOCl- (hypochlorous acid)

Note: this is an example of NF stimulating innate immune system

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12
Q

Production of ___ acid by lactobacilli and ___ acid by proprionibacteria inhibits bacterial growth in vagina and on skin, respectively

A

lactic acid; propionic acid

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13
Q

Normal flora (NF) can induce the production of _____ antibodies, which can be protective against pathogens.
A. cross-reacting
B. several
C. AFB

A

A. cross-reacting

  • this is an ex. of NF stimulating adaptive immune response
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14
Q

One example of NF stimulating adaptive immune response is: antibodies induced by the capsular polysaccharide of a given strain of E. coli found in the gut protects against infection with ________

A

H. influenzae

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15
Q

Which gut microbe induces a protective antibody against H. Infuenzae, type b capsule?

A

E. coli

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16
Q

True or False: Transient flora-induced antibodies are thought to be responsible for induction of isohemagluttinin (ABO blood groups)

A

False - NF-induced antibodies are thought to be responsible for induction of isohemagluttinin

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17
Q

What are three ways that NF prevent colonization by pathogenic organisms?

A

1) Occupy and compete for receptor sites on host cells
2) Complete with pathogens for limited nutrients
3) Make substances that are inhibitory or cidal to pathogens (e.g lactobacilli in vagina makes H2O2)

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18
Q

Which two nutrients (that are essential for the host) are made by the natural flora?

A

Vit B complex and Vit K

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19
Q

True or False: If a patient is on a broad spectrum abx for extended period, they may develop nutritional deficiency

A

True

20
Q

How does hospitalization (e.g debilitation) change the NF of the oropharynx and upper air ways?

A

Shifts from Gram (+) to Gram (-) bacteria

21
Q

How does hospitalization (e.g debilitation) change the NF of the skin?

A

Skin becomes more colonized by enterococci and enteric Gram (-) rods

22
Q

True or False: Certain meds can SPEED UP peristalsis and, thereby, increase transition of gut flora across normal intestinal epithelial barriers, which can lead to sepsis

A

False - certain meds can SLOW peristalsis and, thereby, INCREASE transition of gut flora across normal intestinal epithelial barriers, which can lead to sepsis

23
Q

Which three conditions can allow retrograde colonization of the upper GI tract and oropharyngel cavity by lower GI flora?

Note: If aspirated, can cause pneumonia

A

1) Immobile
2) Prolonged supine position
3) Hypoacidic stomach

24
Q

Catherizations in urinary tract and intubation in respiratory tract can lead to ____ infections

A

nosocomial

25
Q

Use of ____ can change balance of natural flora. For instance, organisms that were present in small numbers prior to abx could emerge as DOMINANT membrane of community and initiate infectious disease (super infection)

A

antibiotics

26
Q

Overgrowth of toxin-producing strains of C.diff in colon can result in antibiotic-associated _____ ____

A

pseudomembranous colitis

27
Q

Alterations in oral or vaginal flora lead to increased susceptibility to which two conditions?

A

1) Oral thrush
2) Vagina candidiasis

28
Q

True or False: Immune compromises related to medical intervention, neoplasia, or infection allow for overgrowth of NF or new colonization with different flora

(note: either can be causes of opportunistic or nosocomial infections)

A

True

29
Q

___: use of living microoragnisms to establish or re-establish NF homeostasis with human host, therefore, preventing, treating, or curing some infectious diseases

A

Probiotics

30
Q

Which four disorder have probiotics been shown to be effective at treating?

A

1) Chronic/recurrent C dif
2) IBS
3) Crohn’s
4) Food allergies

31
Q

True or False: Probiotics prevent side effects of abx tx and reduce chances of developing necrotizing enterocolitis in the neonatal ICU

A

True

32
Q

What are three other uses of probiotics?

A

1) Reduce crying and sx in colic babies
2) Reduce eczema in infants
3) Help prevent cold and flu-like sx

33
Q

Probiotics may contain a mix of which two beneficial bacteria?

A

Bifidobacterium and Lactobacillus

34
Q

____: when both microbe and host benefit
____: when microbe benefits but host is not harmed
___: when microbe benefits and host suffers

A

Mutualism
Commensalism
Parasitism

35
Q

Which type of parasitism occurs when normal flora becomes opportunist, typically when virulence is low?
A. Endogenous
B. Exogenous

A

A. Endogenous

36
Q

True or False: An exogenous pathogen, which is not part of the normal flora, can cause a “classical infectious disease” and damages the healthy host

A

True

37
Q

What is an example of an exogenous infection that can be considered an opportunistic infection, since it does NOT cause infection in immunocompetent people, but only becomes pathogen to immunocompromised or immunosuppressed people?

A

Pneumocystis pneumonia in people with cancer, HIV/AIDS

38
Q

____: a microbial life form that is a harmful symbiont. The etiological agent of an infectious disease
A. Opportunistic pathogen
B. Frank pathogen
C. Pathogen
D. Non-pathogen

A

C. Pathogen

39
Q

____: a pathogen that essentially always causes infection/disease in specific host
A. Opportunistic pathogen
B. Frank pathogen
C. Pathogen
D. Non-pathogen

A

B. Frank pathogen

40
Q

___: infect or cause disease ONLY in compromised host (e.g those who are immune-suppressed, malnourished, have cancer)
A. Opportunistic pathogen
B. Frank pathogen
C. Pathogen
D. Non-pathogen

A

A. Opportunistic pathogen

41
Q

True or False: Lactobacillus is an example of a non-pathogen (essentially never causes disease, even if host is severely compromised)

A

True

42
Q

True or False: Pathogenicity and Virulence are essentially interchangeable terms that describe the degree to which a pathogen causes disease

A

True

43
Q

Microbes pathogenicity (ability to cause disease) is described in terms of their ____(degree of pathogenicity)

A

virulence

44
Q

The ____ factors (determinants of virulence) of a pathogen are any of the genetic, biochemical, or structural features that enable it to produce disease in a host

A

virulence

45
Q

True or False: Pathogenicity varies from host to host, even in the same host species, and varies from pathogen to pathogen, even in the same species

A

True

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