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

2. Vibrios  Gram (-ve) curved bacilli motile with a single polar flagellum aerobic grow in alkaline pH  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

3. 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

4. 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

5. 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

6. 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 CO2 is evolved and detected in breath  The presence of IgG Abs in patient’s serum  Detection of H. pylori Ag in stool  Treatment: Combined therapy with metronidazole, amoxicillin or tetracycline and bismuth salts

7. 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