Corynebacterium spp.

Question 1

Gram positive bacilli
Aerobic

Answer 1

Corynebacteria,
Bacillus

Question 2

Corynebacteria culture conditions

Answer 2

Aerobic 37C Blood agar

Question 3

Corynebacteria colony morphology on BA

Answer 3

1-2mm round, dry, grey/cream
weak b-haemolysis

Question 4

Corynebacteria basic characteristics

Answer 4

Gram positive bacilli
Chinese-lettering appearance (clusters)
KOH negative
Oxidase negative
Catalase positive

Question 5

Presumptive corynebacteria spp. tests

Answer 5

1. Trehalose fermentation
2. Urease Production
3. Tinsdale medium

Question 6

Gram positive bacilli
Chinese-lettering appearance (clusters)
KOH negative
Oxidase negative
Catalase positive

Answer 6

Corynebacterium spp.

Question 7

Corynebacterium spp. Trehalose fermentation + Urease Production test procedure

Answer 7

1. Label each tube appropriately + loosen the caps.
2. Label blood agar plate = purity plate check.
3. Inoculate trehalose peptone water sugar - tilt liquid media to the right an gently ‘rub’ inoculate loop on the left side of the tube just below meniscus. Turn upright + gently shake.
4. Immediately after inoculation of trehalose, without flaming, inoculate urea medium by zig-zagging over surface of the agar and ‘stabbing’ the slop with the loop.
5. Immediately after inoculating the urea slop, without flaming, inoculate the blood agar using quadrant streak method.
6. Incubate the inoculated trehalose, urea agar slope and blood agar purity plate at 37C overnight.

Question 8

Corynebacterium Trehalose + Urease biochemical test results

Answer 8

Trehalose
Positive = pink -> yellow + presence of bubble (indicates gas production).
Negative = remains pink.
Urease:
Positive = Yellow -> Pink
Negative = remains yellow.

Question 9

Corynebacterium Tinsdale medium test procedure

Answer 9

1. Streak inoculate Tinsdale selective media.
2. Let loop dig into agar in places with Tinsdale medium.
3. Incubate plate at 37C.
4. Read at 24hrs + 48hrs.

Question 10

Corynebacterium Tinsdale medium test - colonial characteristics

Answer 10

C. diphtheriae - gravis = small, shiny black.
C. diphtheriae - mitis/ulcerans = convex colonies with dark brown halos after 24hrs.
C. dipththeriae - intermedius = Pale brown colonies with form halos after 36hrs incubation.
Diphtheroids = dark brown colonies without halos - no discolouration of the medium.

Question 11

Tinsdale medium - C. diphtheriae - gravis

Answer 11

Small shiny black colonies

Question 12

Tinsdale medium = C- diptheriae - mitis
C. ulcerans

Answer 12

Convex colonies with dark brown halos after 24hrs incubation.

Question 13

Tinsdale medium = C. diphtheriae biotype intermedius

Answer 13

Pale brown colonies which form halos after 36hrs incubation.

Question 14

Tinsdale medium = Diphtheroids

Answer 14

Dark brown colonies without halos - minute colonies showing no discolouration of the medium

Question 15

Corynebacteria diphteria test results (1. Chinese lettering, 2. fermentation of trehalose, 3. urease production, 4. growth on tinsdale medium)

Answer 15

1. Chinese lettering positive
2. No fermentation of trehalose (remains pink)
3. No urease production (remains yellow).
4. Growth on tindsale medium positive.

Question 16

Corynebacteria ulcerans test results (1. Chinese lettering, 2. fermentation of trehalose, 3. urease production, 4. growth on tinsdale medium)

Answer 16

1. Chinese lettering positive
2. Fermentation of trehalose (turns yellow)
3. Urease production (turns pink).
4. Growth on tindsale medium positive.

Question 17

Corynebacteria pseudotuberculosis test results (1. Chinese lettering, 2. fermentation of trehalose, 3. urease production, 4. growth on tinsdale medium)

Answer 17

1. Chinese lettering positive
2. No fermentation of trehalose (remains pink)
3. Urease production (turns pink).
4. Growth on tindsale medium positive.

Question 18

Diphtheroids test results (1. Chinese lettering, 2. fermentation of trehalose, 3. urease production, 4. growth on tinsdale medium)

Answer 18

1. Chinese lettering positive
2. No fermentation of trehalose (remains pink)
3. Urease production (turns pink).
4. Growth on tindsale medium positive.

Question 19

Corynebacterium Trehalose + Urease test controls

Answer 19

Positive control = C.ulcerans
Negative control = E.coli

Question 20

Gram positive bacillus

Answer 20

Corynebacterium (aerobic)
Bacillus (aerobic)
Clostridioides (anaerobic)

Question 21

Corynebacterium spp. basic characteristics

Answer 21

Pleomorphic club shaped rods in chinese lettering arrangements
Gram positve
Non-endospore, non-motile, non encapsulated.
Aerobic + facultate anaerobes.

Question 22

Corynebacterium vs diptheroids

Answer 22

Diphtheroids are corynebacteria spp that are non-pathogenic

Question 23

Medically significant corynebacterium spp. (4)

Answer 23

C. diphtheria
C. ulcerans
C. pseudotuberculosis
C. jeikeium
+ others

Question 24

C. diphtheria infections

Answer 24

Life threatening acute respiratory or cutaneous infection
-Pharyngeal diphtheria = infection of mucous membranes of throat - inflammation + pseudomembrane over larynx/pharynx.
Can block airways - emergency tracheostomy.
-Cutaneous diphtheria

Question 25

Pharyngeal diphtheria symptoms

Answer 25

Low grade fever, malaise, weakness Sore throat, bull neck, pseudomembrane formation - grey adherent formation + difficulty breathing.

Question 26

Pharyngeal diphtheria sequalae

Answer 26

Myocarditis Acute tubular necrosis Nerve demyelination/polyneuropathy Paralysis

Question 27

C. diptheria specimens

Answer 27

Pharyngeal diphtheria - throat swabs, nasopharynx swabs, pseudomembrane swabs. Cutaneous - Swab from lesion.

Question 28

C. diphtheria treatment

Answer 28

Isolation of patient Administration of penicillin G. Anti-diphtheria toxin if it is toxigenic. Prevention is better - toxoid vaccine or 6-in-1 vaccine.