Najran University College of Medicine Enterobacteriaecae 2 BY

Najran University College of Medicine Enterobacteriaecae 2 BY Dr. Ahmed Morad Asaad Professor of Microbiology

Vibrios §Gram (-ve) curved bacilli motile with a single polar flagellum aerobic grow in alkaline p. H §Biochemical reactions: Ferment glucose, maltose, mannite and sucrose with acid only Indole (+ve) and reduce nitrate On nitrate-peptone media: nitros-indole is produced giving a red color with strong acids (cholera red reaction) On TCBS media: pale yellow colonies §Antigenic structure of V. cholerae: §According to the O Ag there are 6 groups: 1 - Group O type-1 (classic and El-Tor biotypes): differentiated by B. R. 2 - Other 5 groups (2 to 6) named non O-1 or non-agglutinable vibrios (NAG) Group O type-1: Classical Cholera NAG: Cholera-like disease §H Ag is shared by all groups

Cholera §Infectious disease with sever vomiting and watery diarrhea (rice water stool) – rapid dehydration – collapse and shock §Endemic – epidemic - pandemic §Pathogenesis: §Highly infectious disease §By oral route §Water-borne epidemic §Incubation period is 2 -5 days §Source of infection: case or carrier §Not invasive disease §Localized to intestine §Heat labile enterotoxin (choleragen) By V. cholera O-1 2 subunits A and B Subunit B for cell binding promoting entry of subunit A

Subunit A: stimulate adenylate cyclase enzyme (stimulate water and electrolytes hypersecretions into lumen) §Laboratory diagnosis Diagnosis of suspected (first) case in a non-endemic area: Full identification of the organism is essential before reporting a case of cholera • Stool: rice water stool • Culture on alkaline peptone water for 6 -8 hours (surface pellicle) • Subculture on TCBS • Biochemical identification • Serological identification of V. cholera O-1 type Diagnosis of a case during an epidemic (secondary case): Direct microscopic examination (Hanging drop) for detecting motile vibrios

Diagnosis of a carrier: Rectal swab Full identification (important in endemic areas) §Treatment: • I. V. fluids (correct dehydration) • Tetracycline (secondary line) §Prophylaxis: • Community and personal hygiene • Chemoprophylaxis by tetracycline to exposed persons • Vaccination by Koll’s vaccine: Heat killed vaccine – 2 S. C. injection – limited role (why) • Oral cholera vaccine by DNA recombinent technique

Helicobacter pylori §Gram (-ve) spiral-shaped (helical) bacilli, microaerophilic, urease (+ve) §Normal inhabitant of stomach (by ingestion) §Can cause gastritis, peptic ulcer and risk factor for gastric carcinoma §Laboratory diagnosis: §Biopsy of gastric mucosa: Gram stained film §Culture on Skirrow’s medium §Urease breath test: radiolabelled urea is ingested. If the organism is present radiolabelled CO 2 is evolved and detected in breath §The presence of Ig. G Abs in patient’s serum §Detection of H. pylori Ag in stool §Treatment: Combined therapy with metronidazole, amoxicillin or tetracycline and bismuth salts

Cambylobacter §Have long been known as animal pathogens §C. jejuni and C. coli: enterocolitiis (in children) §Morphology: §Gram (-ve) curved or S-shaped bacilli §Motile (cork-screw motility) §Microaerophilic §Growth on Skirrow’s medium at 42⁰ C §Treatment: Erythromycin and nalidixic acid