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MBIO 360 > Module 3 > Flashcards

Module 3 Flashcards

1
Q

What are the common characteristics of Corynebacterium?

A

Gram pos rods

Non spore forming

Aerobic or facultative

Catalase pos

Motility neg

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2
Q

What is the major human pathogen in Corynebacterium?

A

C. diphtheriae

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3
Q

What are the what are the cellular characteristics of C. diphtheriae?

A

Gram pos rods, club like shape, volutin granules

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4
Q

How can volutin granules be better visualized?

A

Loeffler’s alkaline methylene blue or Albert’s stain

Deep blue purple colour

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5
Q

What are the growth requirements for C. diphtheriae?

A

Facultative anaerobes

CO2 not required

35°C optimum

Better growth with blood or serum enrichment

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6
Q

Where are most C. diphtheriae specimens isolated from?

A

Cutaneous or upper respiratory sources

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7
Q

What media is used to prevent the growth of normal flora when isolating C. diphtheriae?

A

Potassium tellurite agar- growth reduces tellurite, producing gun metal grey colonies, Staph may also grow

Cysteine tellurite agar- inhibitory to most other organisms

Modified tinsdale medium- differentiates dips from C. diphtheriae (black colonies with brown halo)

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8
Q

What special requirements does modified tinsdale medium require?

A

Halo formation is enhanced by reduced oxygen and stabbing the inoculum into the agar

Shouldn’t be incubated in increased CO2

May require 48hr incubation

Short shelf life, constant QC required

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9
Q

What is the colony morphology of C. diphtheriae?

A

BAP- white/grey, dull, may be granular (volutin), usually nonhemolytic

Tinsdale- grey/black with brown halos, garlic odour, may be able to differentiate bio types (intermechin, gracias, mitis)

Broth culture- brittle surface growth

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10
Q

What is the genus ID for Corynebacterium?

A

Gram pos rods

Opaque dull colonies on BAP

Growth on tellurite

Volutin granules

Cat pos

Nonmotile

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11
Q

What is the species ID for C. diphtheriae?

A

Biochem testing

Urease neg

Ferments glucose, maltose, sucrose

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12
Q

What is the urease reaction of C. ulcerans and psuedotuberculosis?

A

Positive

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13
Q

What is the Elek test?

A

Tests for toxin produced by C. diphtheriae

Gel precipitation where toxin combines with antitoxin

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14
Q

What is the pathogenicity of C diphtheriae?

A

Only infects humans

Droplet transmission

1-7 days of incubation

Pharynx is usual infection site- toxin causes necrosis, swollen cervical lymph nodes, pseudomembrane

Toxin action- myocardial degeneration, neurological systems, 20% of cases

Cutaneous infections

Most isolated from carriers

Prevention by immunization (DPT)

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15
Q

What is the treatment of C. diphtheriae?

A

Antimicrobial susceptibility testing on all isolates

No resistance

Antitoxin given ASAP

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16
Q

What are the characteristics of dips?

A

Normal flora of skin and mucous membranes

Short club shaped gram pos rods

BAP- full, opaque, grey/white, nonhemolytic

Tellurite- grey/black with no brown halos

Catalase pos

17
Q

What is the species ID for dips?

A

Normal flora so species ID is not usually required

Endocarditis is the most common infection

Biochem testing

18
Q

What is the most common isolated species from dips and what is its species ID?

A

C. xerosis

Nitrate pos

Urease neg

Ferments glucose, maltose, sucrose

19
Q

What is another common dip isolate and it’s species ID?

A

C. pseudodiphtheriticum

Nitrate pos

Urease pos

No fermentation

20
Q

What are the characteristics of C. jeikeium?

A

Nosocomial pathogen in immunosuppressed patients

Normal flora on skin

Slow growing, small grey/white glistening colonies in 48hrs

Resistant to most antimicrobials other than vancomycin

21
Q

What are the characteristics of Rhodococcus equi?

A

Serious infections in AIDS patients

Gram pos coccoid in young cultures, filamentous as they age

BAP and choc agar- 24hr tiny but large mucoid colonies at 48hrs

Catalase pos, no fermentation

Animal pathogen, survives a long time in soil

Pulmonary infections are most common

22
Q

How many species of Corynebacterium are isolated?

A

20

MBIO 360 (14 decks)

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