cornyebacterium dip

Question 1

Bacillus and Clostridium form spores where as Corynebacterium, Erysipelothrix and Listeria do not

Question 2

Bacillus and Clostridium species are longer and more deeply staining than Corynebacterium and Listeria species.

Question 3

Corynebacteria
general character

Answer 3

Gram positive

Non motile, non spore forming straight or slightly curved rods

Pleomorphic, tend to be clubbed or irregularly shaped

Have metachromatic granules

Aerobic, facultative anaerobic and catalase positive

Question 4

The major disease caused by C. diphtheriae is

Answer 4

diphtheria
An infection of the local tissue of the upper respiratory

Question 5

Medically important species

Answer 5

C. diphtheriae
C. ulcerans
C. pseudotuberculosis

Question 6

Individual corynebacteria in stained smears tend to lie

Answer 6

parallel or at acute angles to one another

Question 7

True branching is rarely observed in cultures
Arranged in angular fashion like

Answer 7

Chinese lettering or cuneiform arrangement

Question 8

The “barred” appearance is due to the presence of

Answer 8

polyphosphate inclusions called metachromatic granules

Question 9

On blood agar, colonies are

Answer 9

small, granular, and gray with irregular edges and may have small zones of hemolysis

Question 10

There are four biovars (biotypes): on basis of growth characteristics such as colony morphology, biochemical reactions, and severity of disease

Answer 10

gravis, intermedius, mitis, and belfanti.

Question 11

Virulence factor
Corynebacterium diphtheriae

Answer 11

Diphtheria toxin an exotoxin

Question 12

Diphtheria toxin an exotoxin
characters

Answer 12

Is a heat-labile polypeptide produced during lysogeny of a  phage that carries the “tox” gene.

Alkaline pH of 7.8- 8.0, aerobic conditions
A low environmental iron level

Question 13

The toxin inhibits protein synthesis

Answer 13

by ADP-ribosylating elongation factor 2

Question 14

The diphtheria toxin is a heat-labile polypeptide, composed of two fragments

Answer 14

A (active) and B (binding).

Question 15

Human are the only known reservoir with the carriage in

Answer 15

Oropharynx
Gastrointestinal tract
Urogenital tract and on the skin surface

Question 16

Clinical feature

Answer 16

Respiratory Diphtheria
Diphtheria - pseudomembrane

Cutaneous Diphtheria

Question 17

Complication in patients with sever disease include

Answer 17

Breathing obstruction,

The more dangerous effects occur when the toxin becomes systemic and attacks the heart

Cardiac arrhythmia, coma and ultimately death
Nerve weakness or paralysis, especially of the cranial nerves

Question 18

C. diphtheriae does not actively invade deep tissues and practically never enters the bloodstream

Question 19

cultures of C. dip

Answer 19

loeffler
Tellurite blood agar:
Tinsdale medium:

Question 20

each culture character

Answer 20

It is not advisable to use either Dorset egg or Loeffler serum medium as a primary medium for isolating
C. diphtheriae because commensal diphtheroids may overgrow the diphtheria bacteria.

This medium is widely used as a primary medium for isolating C. diphtheriae from throat and nasopharyngeal swabs

The brown colour is due to the hydrogen sulphide produced from the cystine interacting with the tellurite
commensals But the colonies are not surrounded by a brown halo like those of C. diphtheriae.

Question 21

Biochemical tests

Answer 21

reduces nitrate to nitrites
Catalase Positive
Oxidase negative.
Urease negative.

ferments
glucose and maltose
gravis and mitis sucrose
gravis starch

Question 22

Toxigenicity of C. diphtheriae can be tested by

Answer 22

the Elek gel precipitation test.

Question 23

Toxin-producing C. diphtheriae is identified by

Answer 23

the presence of precipitin lines and arcs of identity