MEMBERS OF THE FAMILY ENTEROBACTERIACEAE

Citrobacter Resembles Salmonella but are ONPG (+)

& LDC (-) Citrobacter species

freundii (UTI, pneumonia, intraabdominal abscess)

diversus (neonatal meningitis)amalonaticus (extraintestinal infections)

C. freundiiS. diversusH2S+-

Indole-+KCN+-

KlebsiellaKlebsiella -Enterobacter-Serratia-Hafnia

K. pneumoniae>Friedlander’s bacilli (encapsulated and

mucoid)> (+) String test

Klebsiella aerogenes is associated with hospital acquired infections of wounds and of the urinary tract

K. rhinoschleromatis – rhinoscleromatis (granulomatous disease of the nose and pharynx

with intense swelling and malformation of the entire face and neck)

The patient's K. pneumoniae isolate was string test positive (>5 mm

string length).

LABORATORY DIAGNOSES Specimens: Depending on the site of infection, specimens include urine, pus, sputum and infected tissue. Morphology Klebsiellae are Gram negative, non-motile, usually capsulated rods. Culture Klebsiellae are aerobes and facultative anaerobes. Blood agar: Klebsiellae produce large grey white usually mucoid

colonies. MacConkey agar and CLED medium: Most klebsiellae are lactose-

fermenting, producing mucoid pink colonies on MacConkey agar and yellow mucoid colonies on CLED medium

K. rhinoscleromatis is non-lactose fermenting. Biochemical tests Klebsiellae are indole negative, ornithine decarboxylase negative and do

not produce H2S.

Klebsiella on Macconkey medium show large mucoid pink lactose fermenting colony

Klebsiella on CLED medium show yellow lactose fermenting colony

Enterobacter

LDCADHODCUreaseYellowpigment

E. cloacae-++ V-E. aerogenes+-+- -

E. gergoviae+-++ -E. sakazakii-++- +E. taylorae-+- + -

-species: habitat: soil, water, dairy products-normal flora of the gut of animals & humans-motile, ODC & ONPG (+)

Enterobacter

Edwardsiella

Edwardsiellatarda (human pathogen –

bacteremia and wound infection)hoshinae (snakes, birds and

water)ictaluri (enteric septicemia in

fish)

Serratiaopportunistic pathogensDNAse, lipase, gelatinase

○S. marcescens○S. liquefaciens○S. rubidaea○S. oderifera

Serratia

Proteus

Tow important species , P. mirabilis and P. vulgaris

Morphology Proteus is actively motile with peritricous

flagella , non capsulate, Gram negative pleomorphic rods.

Rapid urease producers Swarming, burned chocolate odor

Proteus with peritricous flagella

PathogenicityP. mirabilis causes: 1- Urinary infections. in the elderly and young males and often following catheterization or cystoscopy..2- Abdominal and wound infections 3- secondary invader of ulcers, burns and damaged tissues. 4- Septicaemia 5- Meningitis and Chest infections.

Cultureaerobically, most Proteus cultures have a characteristic ‘fishy’ Odour and Swarming on the medium

MacConkey, CLED, XLD media: non-lactose fermenting colonies after overnight incubation at 35–37 ºCSwarming is prevented on MacConkey agar and XLD agar because these media contain bile salts.Swarming is inhibited on CLED agar because it

is electrolyte deficientBiochemical testsDo not ferment lactose. Rapidly hydrolyze urea (within 4 hours), early screening test in differentiating enteric pathogens, e.g. salmonellae and shigellae from Proteus.Phenylalanine deaminase (PDA), positive.Indole negative (P. vulgaris is indole positive).

Proteus P. mirabilis P. vulgaris

Indole-+ODC+-

Fermentation Maltose - + Xylose + + Salicin - +

ChloramphenicolSR

Proteus P. mirabilis P. vulgaris

Indole……….…… Maltose……….……Xylose..…….……Salicin ..…….……

Chloramphenicol..…………

Proteus Proteus McConkey Urease test

Swarming on Blood agar

Swarming pehomenon

Morganella Formerl known as Proteus M. morganii – only specie UTI’s and wound infections

Providencia Providencia ( 4 species – P. alcalifaciens,

P. Rustigianii, P. rettgeri, P. stuartii)P. rettgeri P. stuartii

Urease + - Citrate + +

Yersinia 11 species

Y. pestis (plague) – bipolar staining (wayson) Agent of bubonic plague, pneumonic and septicemic plagues

○ Bubonic – bite of infected flea○ Pneumonic○ Prefered growth at 25 deg C

Y. enterocolitica (acute enteritis – appendictis like)○ Pig, cats and dogs ○ Cold enrichment○ Motile at RT

Y. pseudotuberculosis○ Pathogen in animals (turkey, geese, doves, farm and

domestic animals)

YERSINIA

Safety pin appearance

Yersinia pestis

Revision Question 1- Characteristic of enterobacterceae all of the following

except : a- Gram negative rod b- Facultative anaerobic c- Ferment glucose d- Oxidase positive 2-Sworming is special characteristic of: a. Pseudomonades b- Proteus c- E. coli d- Klebsiella 3- Mucoid colony is special characteristic of: a. Pseudomonades b- Proteus c- E. coli d- Klebsiella  

4- Bacteria which give green metallic sheen on EMB medium is:

a. Pseudomonades b- Proteus c- E. coli d- Klebsiella 5- Polysaccharide capsule present on which of the following

bacteria: a. Pseudomonades b- Proteus c- Shigella d- Klebsiella 6- Which of the following bacteria is urease positive : a. Pseudomonades b- Proteus c- E. coli d- Klebsiella 7- Which of the following bacteria is lactose fermenter: a. Pseudomonades b- Proteus c- E. coli

When we inoculate members of enterobacterceae on MacConkey agar, mention which organism grow producing lactose fermentor colony and which grow producing lactose fermentor colony

klebsiella and e.coli

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