Non-spore-forming Gram-positive Bacilli

Question 1

Specimen for Corynebacterium diphtheriae

Swabs from the

Answer 1

oropharynx

nasopharynx

cutaneous lesions

Question 2

If a pseudomembrane is present, swab specimens from [?] the membrane should be collected.

Answer 2

beneath

Question 3

Gram staining: [?] that occur in angular arrangements (commonly referred to as Chinese letters or palisades) and whose ends may be swollen, producing a club shape.

Answer 3

Pleomorphic gram-positive rods

Question 4

Pleomorphic beaded rods, reddish purple metachromatic granules or bars of polyphosphates are apparent.

Answer 4

Loeffler’s alkaline methylene blue (LAMB), e.g., Albert’s staining:

Question 5

C. ulcerans and C. pseudotuberculosis resemble C. diphtheriae, producing [?] cells containing metachromatic granules.

Answer 5

distinctive, clubshaped, diphtheroidal

Question 6

Used to screen and rule out group A β-hemolytic streptococci from throat specimen.

Answer 6

5% sheep BAM, Columbia CNA agar

Question 7

AKA Cystine-sodium thiosulfate-tellurite

medium

Answer 7

Tinsdale agar (TIN)

Question 8

High concentration of potassium tellurite is inhibitory to most [?] (other than Corynebacterium species) and majority of [?]

Answer 8

upper respiratory tract normal flora

gram-negative bacteria

Question 9

organisms capable of growing on the

medium are differentiated based on the [?], resulting in the reduction to tellurium, thus will grow as [?].

Answer 9

tellurite reductase activity

black colonies

Question 10

[?] and [?] provide essential growth factors.

Answer 10

Bovine serum and horse serum

Question 11

provide sulfur for H2S production; and cystine detects cystinase activity producing brown halos around the colonies.

Answer 11

Sodium thiosulfate

Question 12

A heart infusion agar supplemented with [?].

Answer 12

5% rabbit blood, tellurite, and Lcystine

Question 13

A selective and differential medium for Corynebacterium species similar
to TIN.

Answer 13

Cystine-tellurite blood agar (CTBA)

Question 14

Contains [?] and [?], rather than agar, to coagulate to produce a solid medium.

Answer 14

eggs and beef serum

Question 15

Stimulates the growth of distinctive, [?] cells of C. diphtheriae and the production of metachromatic granules in the cells.

Answer 15

club-shaped, diphtheroidal

Question 16

colonies show no characteristic differential features to distinguish from other gram-positive bacilli.

Answer 16

“Poached egg”

Question 17

Contains coagulated egg in distilled water and glycerin.

Answer 17

Pai medium

Question 18

Specimens should be inoculated to a [?] and a selective medium such as a [?] (eg, CTBA or TIN)

Answer 18

blood agar

tellurite plate

Question 19

Incubate at either in ambient air or in

Answer 19

5% to 10% CO2 for 24 - 48 h

Question 20

C. diphtheriae may appear as four distinct colony types (biotypes) designated [?]

These biotypes also differ slightly in Gram’s stain morphology, certain biochemical reactions, and historically, in the severity of the disease processes they produce.

Answer 20

gravis, mitis, intermedius, and belfanti

Question 21

On

C. diphtheriae produce colonies ranging from

small, gray, and translucent - [?]

to medium, white, and opaque

C. diphtheriae [?] may be βhemolytic.

Answer 21

BAM

• biotype intermedius
• biotypes mitis, belfanti, and gravis
• biotype mitis

Question 22

On

Colonies of C. diphtheriae appear

Answer 22

CTBA

black or gray.

Question 23

Large (2-4 mm), flatter, dark gray with radial striations and irregular edges.

“DAISY HEAD” colonies.

Short, coccoid, or pyriform.

Answer 23

C. diphtheriae biotype gravis

Question 24

Small (0.5 mm), sometime pinpoint, flat, and gray.

“FROG’S EGGS” colonies.

Highly pleomorphic, from very long to very short rods.

Answer 24

C. diphtheriae biotype intermedius

Question 25

Medium-sized (1-2 mm), convex, very black with regular edges.

“COOLIE HAT” colonies.

May be weakly βhemolytic

Long, pleomorphic, rigid clubshaped rods.

Answer 25

C. diphtheriae biotype mitis

C. diphtheriae biotype belfanti

Question 26

On

All four biotypes of C. diphtheriae grow as [?] surrounded by [?].

Answer 26

TIN

• black colonies
• dark brown halos

Question 27

C. ulcerans and C. pseudotuberculosis resemble C. diphtheriae, producing [?] that are surrounded by brown halos on TIN.

Answer 27

black colonies

Question 28

Other diphtheroids, S. aureus and some streptococci which can also grow in the presence of tellurite will develop black colonies due to tellurite reduction although [?] around the colonies are NOT present.

Answer 28

brown halos

Question 29

is based on the production by the organism of phospholipase C or D that inhibits the staphylococcal β-hemolysin.

Answer 29

The reverse CAMP reaction

Question 30

An arrowhead zone of [?] is formed at the junction of the organism being tested with the staphylococci.

Answer 30

NO hemolysis

Question 31

Once an organism is biochemically identified as a possible C. diphtheriae, the isolate must be tested for the ability to produce diphtheria toxin.

Answer 31

Toxigenicity test

Question 32

For demonstration of toxin production by C. diphtheriae.

Answer 32

Elek Test

Question 33

A filter paper strip impregnated with [?] is buried just beneath the surface of a [?] before the agar hardens.

Strains to be tested and known positive and negative toxigenic strains are streaked on the agar’s surface in a line across the plate and at a right angle to the antitoxin paper strip.

After 24 hours of incubation at 37°C, the plates are examined with transmitted light for the presence of fine [?] at a 45-degree angle to the streaks.

The presence of precipitin lines indicates that the strain produced toxin that reacted with the [?].

Line 1 is the negative control.
Line 2 is the positive control.
Line 3 is a test organism that is a nontoxigenic strain.
Line 4 is a test organism that is a toxigenic strain.

Answer 33

diphtheria antitoxin
rabbit serum agar plate
precipitin lines
homologous antitoxin

Question 34

Specimens for Listeria monocytogenes

Answer 34

CSF, blood, amniotic fluid/placenta

Question 35

Gram staining: Short, gram-positive bacilli (coccobacilli) may occur intracellularly or extracellularly, at times, may occur in pairs and be mistaken for pneumococci; it tends to appear gram-negative when overdecolorized.

Answer 35

Listeria monocytogenes

Question 36

In wet mounts observed at 25oC, it exhibits “tumbling” or “head over heels” motility.

Answer 36

Listeria monocytogenes

Question 37

Recovery of the organism from clinical samples is enhanced by inoculation in broth medium and incubation at 4°C for 4 \ hours prior to incubation on primary culture plates.

Answer 37

Cold enrichment technique: Listeria monocytogenes

Question 38

Requires 5% to 10% CO2 for growth.

Answer 38

Listeria monocytogenes

Question 39

L. monocytogenes has a narrow zone of beta-hemolysis on

Answer 39

5% sheep BAM

Question 40

can be used as a plating medium with or without supplementation of blood

Answer 40

McBride Agar

Question 41

Partial selectivity is provided by [?], which aid in suppressing both G+ and G-bacteria other than Listeria

Answer 41

lithium chloride, glycine and phenylethanol

Question 42

develops into small, blue-green colonies, with small zone of hemolysis around and under colonies.

Answer 42

L. monocytogenes on McBride Agar

Question 43

In semi-solid medium, the identification can be made by observing for a thin, umbrella-like growth from the stab line.

Answer 43

Motility test

Question 44

This is a pathogenicity test that differentiates pathogenic from non-pathogenic strains of L. moncytogenes.

It Involves instillation of a 24hr broth culture of L. monocytogenes in the conjunctiva of a lab animal.

Development of purulent conjunctivitis within 24 to 36 hours constitutes a positive result.

Answer 44

Anton Test