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MLSCI 242 > LAB - Gram Positive Bacilli & Candida > Flashcards

LAB - Gram Positive Bacilli & Candida Flashcards

1
Q

majority of Corynebacterium species are found in normal flora here

A

skin and mucous membranes

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2
Q

Corynebacterium diphtheriae is the major human pathogen in the genus and causes these two disease forms:

A

respiratory & cutaneous diphtheria

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3
Q

3 biotypes of Corynebacterium diphtheriae

A

gravis
mitis
intermedius

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4
Q

T or F. C. diphtheriae is only found in humans

A

T

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5
Q

C. diptheriae infects the URT to cause diphtheria in which…

A

a pseudomembrane forms in the oropharynx and obstructs the airway

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6
Q

T or F. just bc C. diphtheriae is present, does not mean the patient has diphtheria

A

T! some strains do not produce the toxin

diagnosis depends in isolate producing DT (Elek test)

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7
Q

C. diphtheriae is isolated most commonly from the following swabs:

A 
throat swabs (pharyngeal)
also from skin lesions, nasal swabs, or ear swabs
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8
Q

T or F. C. diphtheriae can grow on BAP as a facultative organism

A

T! but better growth on:
Tellurite media (cystine tellurite, Hoyle’s or Tinsdale’s agar)
Loeffler’s Blood Seum (LBS)

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9
Q

Tellurite media

A
  • potassium tellurite, a colorless salt = inhibits most normal flora bacteria from the respiratory tract
  • also reduced by Corynebacterium to metallic tellurium which stains colonies brown-black
  • some g+c may present with black colonies
  • selective and differential by H2S production (from Na2S2O3 and L-cysteine) so presumptive C. diptheriae are seen by the brown-black halo
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10
Q

Loeffler’s Blood Serum

A
  • enriched w serum and egg to enhance growth C. diphtheria
  • formation of metachromatic granules
  • used more frequently for secondary isolation of diphtheria from telluride media in order to obtain organisms in pure culture + to enhance granule morphology when stained w methylene blue
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11
Q

dips

A
  • resemble C. diphtheriae morphologically but NO toxin
  • no halo on Tinsdale
  • normal human skin and mucous membrane flora and are invariably found in many specimens
  • palisades
  • facultative, small, dry wh colonies that are
  • strongly cat pos
  • can be opportunistic in compromised hosts
  • exhibit resistance to antimicrobial agents
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12
Q

Bacillus

A
  • aerobic, gram pos
  • endospores
  • spores do not stain on gram stain
  • often a lab contaminant
  • grows well on BAP; large colonies, raised, beta-hemolytic with frosted green-grayish glassy appearance
  • majority of species are not pathogenic
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13
Q

primary pathogen of Bacillus

A

B. anthracis

  • common disease of livestock worldwide
  • most cases associated with imported animal hair or wool = skin necrotic lesions = BLACK ESCHAR
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14
Q

Bacillus cereus

A

food poisoning

- opportunistic

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15
Q

B. anthracis and B. cereus common characteristics

A
  • catalse, lectithinase postiive
  • oxidase negative
  • produce acid from glucose
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16
Q

B. cereus vs. B. anthraci

A
  • cereus = beta-hemolytic and motile; anthracis is NOT
  • B. anthracis = large and filamentous colonies = medusa head
  • B. anthracis is susceptible to penicillin disc test while other species are resistant
17
Q

Listeria monocytogenes

A
  • facilitate anaerobe with beta hemolysis
  • catalase pos
  • bile esculin, bile hydrolysis pos
  • CAMP positive
  • tumbling motility at 25 C but not at 37 C
  • semi-solid motility media = umbrella-like growth
  • neonatal sepsis/meningitis puerperal sepsis/ sepsis
  • meningitis in immunocompromised patients and pregnant women
18
Q

specimens for isolation of Listeria

A
  • blood
  • CSF
  • amniotic fluid
19
Q

Gardnerella vaaginalis

A
  • cell wall = gram pos characteristics but stains gram variable to gram neg (bc of pleomorphic nature of CB)
  • nonmotile, facultative bacteria that is present in vagina of up to 70% of women
  • BV infections
  • 5-10% CO2 for a minimum of 48 hours
  • positive for Hippurate hydrolysis
20
Q

what is bacterial vaginosis?

A
  • vaginal inflammation
  • vag discharge with a fishy odor, vag pH over 4.5
  • smears w decreased lactobacillus
  • “clue cells” = epithelial cells covered with gram variable bacilli
    > normal = epi ells with many Lactobacilli
21
Q

T or F. G. vaginalis is beta-hemolytic on sheep BAP

A

F! only shows hemolysiss on HUMAN BAP

22
Q

T or F. Culturing is not necessary for G. vaginalis diagnosis

A

T

23
Q

Lactobacillus

A
  • normal vaginal flora
  • g + b in chains
  • nonhemolytic
  • catalase negative
24
Q

what is the “whiff” test

A
  • used for presumptive diagnosis of BV
  • 1 drop of 10% KOH
    = fish-like odor?
25
Q

Actinomycetes

A
  • may be aerobic or anaerobic
  • aerobic = soil and water; gram pos branching filaments that often fragment into gram variable cb
  • slowly grow (4 weeks in CO2)
  • Nocardia and Streptomyces (main pathogens)
    > chronic tissue disease, systemic infections in immunocompromised patients
26
Q

Candida albicans normal flora

A
  • various body sites
  • endogenous to alimentary or digestive tract + mucocutaneous areas of body
  • most common cause of serious fungal disease or candidiasis
  • most often opportunistic
27
Q

this organism has characteristic sugar fermentation and assimilation

A

C. albicans
- assimilation = ability to grow in the presence of the specific carbohydrate; growth or turbidity is looked for in the presence of O2
BUT since any organism that can ferment a carb can also assimilate it, most labs use only assimilation tests

28
Q

Candida is approximately equivalent in size to

A

RBCs

29
Q

germ tube test

A
  • 2 hrs incubation or else pseudohyphae will develop
  • slide examination at 10X and 40X
  • germ tube pos = bike seats; albicans
  • germ tube neg = pseudohyphae (constriction); Candida sp.
30
Q

a feathery filamentous fringe that may develop around Candida colonies as they age

A

feet

31
Q

this can prevent germ tube formation

A

too heavy if an inoculum

32
Q

these must always be set up when doing a germ tube test

A

positive and negarive controls

to make sure that there are no inhibitory factors present in the high protein media

MLSCI 242 (39 decks)

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