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Acute Intestinal Infection

Gastroenteritis Infection of gut Signs & Symptoms • Nausea • Vomiting • Diarrhoea

rectal swab Faeces

§ If there is delay it is advised to transport specimen in glycerol saline because this prevent the overgrowth of commensal bacteria. § Rectal tube: tube used in cases of cholera for collection of stool from inside the colon.

§ Bile is collected in cases of cholycystitis by duodenal drainage. § Vomitus may be taken in cases of poisoning.

ENTEROBACTERIA CEAE

ENTEROBACTERIACEAE Habitat: intestine Morphology & motility: - Gram negative bacilli - Non spore forming - Motile ‘peritrichate flagella / non - Capsulated / non Growth characters: Aerobe or F. anaerobe 37°C Atmospheric Co 2 Grow easily on ordinary media

FAMILY ENTEROBACTERIACEAE Enterobacteriaceae, are faculatively anaerobic Gram-negative rods.

LF Classification Coliform group: • Escherichia coli • Klebsiella • Citrobacter • Enterobacter NLF • Salmonella • Shigella • Serratia • Proteus • pseudomonas Providencia • Yersinia

Coliform bacilli(LF) 1 -E. coli 2 -Klebsiella 3 -CITRO BACTER

Escherichia, Klebsiella, Citrobacter Gram negative bacilli, non spore forming § Escherichia, Citrobacter: motile § ‘peritrichate flagella, most are noncapsulated

Lab diagnosis of (E. coli) caused disease Commensal ‘intestine’. 1 - Sample: Urine, pus, sputum, blood, CSF, stool, . . 2 - Direct Gram stained film:

Direct smear: stained by Gram: • �Gram negative bacilli, �non spore forming, �motile, �some strains are capsulated.

3 - Culture: - Culture characters: O 2 – CO 2 – Temp. - Media: - Ordinary media: grow easily - Differential media: Mac Conkey’s rose pink colonies(LF) - Colony identification - Characters: - Gram st. film: - B. Rs (I, M, V, C), sugar f. ‘A, G’ - Litmus milk: 4 - Serology: Slide agglutination ‘enteropathogenic antisera’ in case of acute gastroenteritis

Culture: Facultative anaerobes, grow on Mac. Conkey’s agar and produce rose pink colonies.

Mucoid colonies = capsule

�Biochemical reaction: �Ferment glucose, maltose, mannite, lactose and sucrose with acid and gas production. �IMVC (+, +, -, -).

Differentiation: - B. Rs: (IMVC) Indole MR VP Citrate Escherichia + + - - Klebsiella Citrobacter - + + Coliform group - Sugar fermentation: Glucose, lactose, maltose, mannite.

Indole: Demonstrates the ability of certain bacteria to decompose the amino acid ‘tryptophane’ present in peptone to (indole). MR: Demonstrates the ability of some bacteria to produce large amounts of [acid] from fermentation of ‘glucose’, thus lowering the p. H of the medium below 4.

VP: Demonstrates the ability of some bacteria to ferment glucose with production of acetyl methyl carbinol. Citrate: Demonstrates the ability of some bacteria to utilise Na citrate as the only carbon source.

Biochemical differentiation of coliform bacilli Coliform group Indole MR VP Citrate Escherichia + + - - Klebsiella - - + + Citrobacter - +

5 - Typing: - Antibiotic sensitivity strain - Serotyping: O, H, K antigens - Ejkmann test: Use: To differentiate fecal from non-fecal E. coli Principle: Fecal strains of E. coli can grow on fluid Mac. Conkey’s medium at 44°C producing ‘acid & gas’ (Ejkmann positive).

Non Lactose fermenters (NLF)

Shigella § Gram negative bacilli, non spore forming § non motile, non-capsulated

Laboratory diagnosis of shigellosis Diagnosis depends upon the isolation and identification of Shigella from the feces. Specimens: stool which contains mucus and blood.

Culture : Mac. Conkey agar, DCA, salmonella shigella agar (SS agar). enrichment medium may be inoculated with the stool specimen and subcultured into the selective agar media after a short growth period. Shigella is facultative anaerobe, produce pale non lactose fermenting colonies on Mac. Conkey agar and DCA and salmonella shigella agar.

Identification of obtained colonies by: Film stained by Gram: Shigellae are Gramnegative, non motile, non-sporulated, non capsulated rod-shaped bacteria. Biochemical reactions: All fement glucose, all ferment mannite except S dysenteriae all are non lactose fermenter except S sonnei which is late lactose fermenter.

Shigella Lactose Mannite Glucose Sh. dyenteriae - - A Sh. flexneri - A A Sh. boydi - A A Late A A Sh. sonnei