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Acute Intestinal Infection

Gastroenteritis Infection of gut Signs & Symptoms Nausea Vomiting Diarrhoea

Faeces rectal swab

 If there is delay it is advised to transport specimen in glycerol saline because this prevent the overgrowth of commensal bacteria.  Rectal tube  Rectal 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.

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 Co2 - Grow easily on ordinary media

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

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

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

Escherichia, Klebsiella, Citrobacter  Gram negative bacilli, non spore forming  Escherichia, Citrobacter: motile ‘peritrichate flagella, most are non- capsulated

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

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

3- Culture: - Culture characters: O2 – CO2 – 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 MacConkey’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 (+,+,-,-).

Coliform groupIndoleMRVP C itrate Escherichia ++-- Klebsiella --++ C itrobacter -+-+ Differentiation: - B.Rs: (IMVC) - 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 pH 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

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 MacConkey’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 feces Diagnosis depends upon the isolation and identification of Shigella from the feces. Specimens: stool which contains mucus and blood.

Culture : MacConkey 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 MacConkey agar and DCA and salmonella shigella agar.

Identification of obtained colonies by: Film stained by Gram: Shigellae are Gram- negative, 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.

LactoseManniteGlucose Sh.dyenteriae--A Sh.flexneri-AA Sh.boydi-AA Sh. sonneiLateAA Shigella

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings