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Bact > FINAL General REVIEW > Flashcards

FINAL General REVIEW Flashcards

1
Q

Which of the following statements is false for Histophilius somenei?

a. It is an obligate pathogen
b. can cause neurological symptoms
c. colonizes urogential tract
d. causes intravasuclar cogaulation

A

A

Histophilius somenei is normally seen in the respiratory track of animals. THEREFORE, it is NOT an obligate pathogen. It’s an opporuntisitic pathogen

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2
Q

VTEC infections do NOT cause…

A

diarrhea.

VTECH causes edema disease

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3
Q

STa is a highly immunogenic toxin of ETEC. True or False

A

FALSE

You can use it in exams

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4
Q

A dog presents to your clinic with febrile illness and lameness. You are in an endemic area for Amblyomma americanum ticks and suspect a tick-borne disease. Examination of a blood smear reveals a small number of infected neutrophils that include a bacterial morulae. Which of the following etiologic agents may be the cause?

A. Anaplasma phagocytophilum

B. Ehrlichia canis

C. Ehrilicha ewingii

D. A or C

E. any of the above

A

C

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5
Q

Bacteria do not have

A

Nucleus, histones, membrane bound organelles(mitochrondia, lysomes, etc)

HAVE: complex cell wall, peptiodgylcan, chrosomes, ribosomes,

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6
Q

Choose the correct statements:

A. All bacteria have a cell membrane

B. Mycobacteria have lipopolysaccharide

C. Peptiodoglycan is present only in Gram positive Bacteria

D. Mycobacteria are the only acid fast positive bacteria

E. Teichoic acid is unique to gram positive bacteria

A

E.

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7
Q

What is present and what is absent in bacteria?

A

Prokaryotes (No nucleus)

Complex cell wall

A single circular chromosome (exceptions ?)

Asexual reproduction (binary fission)

Absent:

No sterol

Membrane bound organelles are absent

and no histones

Ribosomes (smaller) 70s

No cytoskeleton

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8
Q

Identify the mismatched pair

A. Flagella- motility

B. Fimbriae- adherence

C. Capsule- protect from phagocytosis

D. spores- survivial

E. Endoflagella- Campylobacter

A

E. because Camplyobacter is not a spirocte and only spirocytes have endoflagella

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9
Q

Size of the bacteria are critical to the virulence of a bacterial species

T/F

A

FALSE

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10
Q

Bacterial cell wall Summary

A

All bacteria contains peptidoglycan (exceptions?)

Gram positive bacteria have a thick peptidoglycan layer

Only Gram negative bacteria has an outer membrane which contain lipopolysaccharide(LPS)

Lipid A /endotoxin is harmful
Limulus amebocyte test is used to detect endotoxin(Lipid A) Gram Positive bacteria contain Teichoic acid on their cell walls

Mycobacteria contain mycolic acid and contribute to acid fast positive staining

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11
Q

Choose the incorrect statement:

A. All fungi are eukaryotes

B. Yeasts are unicellular

C. Hyphae are multicelluar

D. Dimorphic fungi exist in yeast and mold form

E. Fungal cell membrane contains sterols

F. Fungal cell wall contain petidogylcan

A

F- petidoglycan is only in bacteria

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12
Q

Which of the following is not a dimorphic yeast?

A. Blastomyces

B. Histoplasma

C. Coccidiodies

D. Cryptococcus

A

D- Cryptococcus is not a dimorphic yeast

The other dimorphic yeast is sporthrix

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13
Q

Animal A Brucella titer= 1:256

Animal B Brucella titer 1:16

who has the higher antibodies in the serum?

A

Animal A

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14
Q

Choose the incorrect statement regarding antibody titer:

A. A positive antibody titer is always diganostic

B. False positive repsonse can be due to previous exposure or vaccination

C. Flase negatives responses can occur ue to early infecgion

D. False negative result can occur due to anergy in the late stages of the disease

E. Four fold increase in the convalescent titer is suggestive of an active infectin.

A

A- you have to have a PAIRED titer to say that an animal is positive

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15
Q

Does Mycobacteria have lipopolysaccharide?

A

NO!!!

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16
Q

Bacterial structures can enhance the

A

Bacterial structures can enhance the virulence of bacteria

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17
Q

How do we identify bacteria?

A

Presence or absence of these structures are used in the

identification of bacteria

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18
Q

Flagella:

A

Locomotion or motility

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19
Q

Fimbriae or pili:

A

Fimbriae or pili: Adherence

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20
Q

Endoflagella/axial filaments

A

Endoflagella/axial filaments are present in spirochetes

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21
Q

What is the purpose of the capsule?

A

Capsule helps to evade phagocytosis

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22
Q

What is the purpose of the spores?

A

Spores helps in bacterial survival

23
Q

Pathogenicity

A

Pathogenicity is the ability of a pathogen to produce a disease by overcoming the defense mechanisms of the host.

24
Q

Virulence

A

Virulence is the degree of pathogenicity

25
Q

What is imporant for the pathogenitiy of a bacteria?

A
  1. Number of organisms
  2. Virulence factors
  3. Status of host immune response
26
Q

What are bacterical virulence factors?

A

Fimbriae, flagella, Capsule, Toxins: (exotoxins and endotoxins) Superantigens.

Transfer of virulence factors can be mediated through Plasmids, and bacteriophages by processes such as conjugation, transformation, and transduction

Quorum sensing
Biofilms

27
Q

quorum sensing

A

Quorum sensing is a system of stimulae and response correlated to population density. Many species of bacteria use quorum sensing to coordinate gene expression according to the density of their local population.

28
Q

Biofilm

A

A biofilm is any group of microorganisms in which cells stick to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS)

29
Q

Exotoxins are seen in

A

gram positive

30
Q

Endotoxins are in

A

gram negative

31
Q

Damage caused by bacteria

A

Damage caused by bacteria
Using the host’s nutrients
Direct damage to the host cell (Toxins) Hypersensitivity reactions
(Type IV Hypersensitivity- Tuberculosis)

32
Q

Obligate pathogen means that

A

if the pathogen is present, then there is a disease present

33
Q

What is the morphology of Rhodococcus?

A

It’s a rod!

34
Q

Are gram negative cocci common?

A

NO!!! They are very, very rare.

35
Q

Fungus summary

A

Fungus: Summary

Eukaryotes

Eukaryotic

Sterols present (ergosterol)in the cell membrane

Contains glucans, mannans, chitin (No peptidoglycan)

Unicellular-Yeast

Multicellular –Molds (hyphae)

Dimorphic Fungus

Sexual and asexual reproduction

Polyphasic approach is necessary for accurate identification(morphology and DNA sequencing)

36
Q

Seroconversion

A

Antibody development after exposure to a pathogen or an antigen

37
Q

Antibody Titer

A

Antibody Titer

Measurement of antibody level (quantity),usually expressed as the reciprocal of the highest dilution of serum that positively reacts in a specific test

eg. a titer of 256 in a test means that the serum sample remains positive when diluted 1:256.

It is the highest dilution of the serum sample which give a positive result in a particular test

38
Q

Interpretation of tests that measure immune response to an agent

A
  1. Generation of an immune response requires time 2. Immune response may persist

“Compare acute and convalescent phase samples”-
Paired serology titers: Four fold increase in serum titers are indicative of infection

(IgM to IgG conversion for T cell dependent responses)

False positives:
prior antigen exposure, vaccination, cross-reactions

False negatives:
Early stages of infection,Late in infection due to anergy, immunosuppression

39
Q

Can any bacteria can opportunistically infect any of the body systems?

A

YES!

40
Q

When can false positives occur?

A

Understand that False positive and False negative results can occur due to sampling, transport, storage issues, antimicrobial therapy, presence of fastidious organisms or when specific procedures are needed

41
Q

What is a Susceptibility break point?

A

A drug concentration above which an organism is considered resistant and at or below this value organism is susceptible to that drug.

Generally for AST testing purposes, three break point values are set at Susceptible, Intermediate, or Resistant

42
Q

What is Minimum inhibitory concentration (MIC)?

A

Minimum amount of drug required to inhibit bacterial growth Drugs with lower MIC values are better choices

43
Q

Disk Diffusion (‘Kirby Bauer’)

A

Must use a bacterial isolate in pure culture

QUALATATIVE TEST- THEREFORE NO MIC VALUES

Standardized bacterial inoculum spread on an agar

plate

Single-concentration antimicrobial disks are used

Growth inhibition zone diameter measured

Published reference breakpoints (zone size) to interpret results

Different drugs will have different zone sizes based on the published data

44
Q

Broth Dilution

A

• Multiple dilutions of antimicrobial agents (usually 2-fold serial dilutions)

Use published reference breakpoints to interpret

• Measure AND report growth inhibition

endpoint (MIC) (MIC reported in micrograms per milliliter)

45
Q

Will you get full range or partial range(breakpoint) from a normal diagnostic laboratory?

A

partial range

46
Q

Gradient diffusion test

A

E-Test (Diffusion and Dilution)

strip test

gives MIC

47
Q

Example of a Broad spectrum antibiotics

A

Broad spectrum antibiotics are active against a wide variety of bacteria Eg. Tetracycline

48
Q

Example of a narrow spectrum antibiotic

A

Narrow spectrum antibiotics affect only a narrow range of bacteria
Eg. Penicillin

49
Q

Time dependant killing:

A

Length of time bacteria are exposed to these antibiotic at a concentration above MIC

( Need frequent dosing or constant infusions)

Beta-lactams, macrolides, tetracyclines, lincosamides, chloramphenicol potentiated sulfonmides(Cefovecin exception protein binding above MIC for 7 days)

50
Q

Concentration dependant killing

A

Rate of killing increases as the drug concentration in plasma increases above MIC High dosing at long intervals (once daily dose)
Prolonged post antibiotic effect

Fluoroquinolones, Aminoglycosides, Metronidazole

51
Q

Antifungal drugs act at the

A

cell membrance/sterols

52
Q

Innate resistance

A

(preexisting genomic property)

53
Q

Acquired resistance

A

(by mutation or horizontal gene transfer)

Bact (34 decks)

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