Genus Corynebacterium

8/13/2019 Genus Corynebacterium

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Genus Corynebacterium



Corynebacterium diptheriae

• Diphtheria Bacteria

• Kleb Loeffler’s Bacillus

• Causes DIPTHERIA

• Pathognomonic sign of

diptheria :

PSEUDOMEMBRANE



Biochemical Characteristics

• Nitrate Red (+), except var. mitis

• Urease (-)

•

Catalase (+)• Ferements glucose and maltose but not

sucrose



Cultural Characteristics• Narrow zone of hemolysis on BAP

• CULTURE MEDIA FOR C. diptheriae

Potassium Tellurite Agar – for primary isolation; coloniesare gray black

Cystine Tellurite Blood Agar(CTBA) – preferred isolation

medium; gunmetal gray coloniesLoeffler’s Coagulated Serum –stimulates production of

metachromatic granules

PAI’s Coagulated Egg Medium – enhances pleomorphism

and granule formationTinsdale Medium



Three Varieties of C. diptheriae

• GRAVIS – large, flat, dark gray colonies withirregular edges and radial striations

- ferments starch and glycogen

• MITIS - “fried egg appearance” on BAP

- on CTBA, colonies are black, convex, andmoist with bleach-like odor

- does not ferment starch and glycogen• INTERMEDIUS – small & black

- does not ferment glycogen and starch



Toxigenecity Test

• In-vitro animal Inoculation test – uses guinea

pig

• ELEK Test – in vitro test

(+) result : line of precipitation

• SCHICK Test- susceptibility test to diptheria

- involves subcutaneous injection of C.diptheriae toxin



Corynebacterium ulcerans

• Highly pleomorphic;

• More pleomorphic and with fewer

metachromatic granules than C. diptheriae

• Growth similar with that of C. diptheriae on

Tellurite agar

•

Grows well on Loeffler’s and PAI’s media • Diseases: mastitis in cattle, diptheria-like

infection in man



Corynebacterium pseudotuberculosis

• Formerly known as C. ovix

• Disease : rare cause of lymphadenitis

following contact with infected livestock



FAMILY ENTEROBACTERIOCEAE

• Lactose Fermenters

Escherichia coli

Klebsiella pneumoniaeEnterobacter aerogenes



• Non-Lactose Fermenter

Salmonella

ShigellaProteus

Yersinea

• Late Lactose FermenterArizona

Citrobacter



• Enterotoxigenic Escherichia coli (ETEC) - an

important cause of diarrhea in infants and

travelers in underdeveloped countries or

regions of poor sanitation

TWO TYPES OF ETEC Toxins

1. heat-labile enterotoxin (LT) -similar in

molecular size, sequence, antigenicity, and

function to the cholera toxin (Ctx)

2. heat stable toxin (ST) – of low molecular size

and resistant to boiling for 30 minutes



• Enteropathogenic Escherichia coli (EPEC)

infection of the human small intestine induces

severe watery diarrhoea linked to a rather

weak inflammatory response

• EPEC's in vivo causes disruption of the

epithelial barrier function



• Enterohemorrhagic Escherichia coli (E. coli

O157:H7 – causes hemorrhagic diarrhea, and

occasionally to kidney failure, especially inyoung children and elderly persons.

Transmission is via the fecal-oral route, and

most illness has been associated with eatingundercooked, contaminated ground beef or

ground pork

•

Produces verotoxin• Associated with HEMOLYTIC UREMIC

SYNDROME (HUS)



Culture of OH157: H7

• Stool culture using SORBITOL McCONKEY

AGAR (SMAC)

• OH157 produces colorless colonies



Enteroinvasive E. coli

• Toxin is similar to Shigella toxin

• Produces bloody diarrhea

•

There are no known animal reservoirs of EIEC.Hence the primary source for EIEC appears to

be infected humans.

• infective dose of Shigella is low (in the range

of 10 to few hundred cells), volunteer feeding

studies showed that at least 106 EIEC

organisms are required to cause illness in

healthy adults.



• Unlike typical E. coli, EIEC are non-motile, do

not decarboxylate lysine and do not ferment

lactose. Pathogenicity of EIEC is primarily due

to its ability to invade and destroy colonic

tissue.



• Enteroaggregative E. coli (EAEC)

The distinguishing feature of EAEC strains is

their ability to attach to tissue culture cells in

an aggregative manner. These strains are

associated with persistent diarrhea in young

children similar to ETEC



• Uropathogenic E. coli (UPEC) cause 90% of the

urinary tract infections (UTI) in anatomically-

normal, unobstructed urinary tracts.

• P fimbria (or pyelonephritis-associated pili

[PAP])- The adhesin that has been most

closely associated with UPEC

• P fimbriae bind with D-galactose-D galactose

residue on RBC surface and on uroepithelial

cell surface



Escherichia coli colonies on EMB (Left) and

McConkey Agar (Right)



Enterobacter aerogenes on EMB (Left) and

McConkey (Right)



Flagellar stain of a Salmonella Typhi. Salmonella can be

differentiated from Shigella on the bais of a motility test or a

flagellar stain. (CDC)



Salmonella on EMB (Left)

and McConkey (Right)



Table 1. Characteristics shared by most Salmonella

strains belonging to subspecies I

Lactose negative; acid and gas from glucose,

mannitol, maltose, and sorbitol; no Acid from

adonitol, sucrose, salicin, lactose

ONPG test negative (lactose negative)

IMVIC - + - + Gelatin hydrolysis negative



• Lysine decarboxylase positive

Urease negative

Ornithine decarboxylase positive

H2S produced from thiosulfate Do not grow with KCN

Phenylalanine and tryptophan deaminase

negative Gelatin Hydrolysis negative



• Salmonella sp. after 24

hours growth on XLD

agar. Xylose Lysine (XL)

agar supplementedwith sodium

thiosulfate, ferric

ammonium citrate, and

sodium deoxycholate,it is then termed XLD

agar (CDC)



Colonial growth pattern displayed by Salmonella

Typhimurium cultured on a Hektoen enteric (HEA) (CDC)



Shigella

•S. dysenteriae – Shiga’s bacillus

• S. flexneri – Strong’s bacillus

• S. boydi

• S. sonnei – Sonne Duval’s bacillus

Cultural Characteristics:

XLD- pink to red colonies

HEA – green to blue green colonies

SSA – colorless colonies



Photomicrograph of Shigella from a stool sample

( phototaken from wikipedia)

http://upload.wikimedia.org/wikipedia/commons/2/29/Shigella_stool.jpg



Swarming colonies of Proteus

on EMB

Genus Corynebacterium

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