Presentation on theme: "Food poisoning; Enteric fever and Gastroenteritis"— Presentation transcript:
1 Food poisoning; Enteric fever and Gastroenteritis SalmonellaFood poisoning; Enteric fever and Gastroenteritis
2 Bacteriology Salmonella enterica one species, ~2000 serotypeS. enterica serotype typhimurium or S. typhimuriumRod-shaped, non-spore-forming Gram-negative bacteriumBelongs to the family Enterobacteriaceaeclose relative of E. coliMotile by peritrichous flagella (H antigen).Non motile exceptions: S. gallinarum and S. pullorum
3 Salmonella infections in humans Enteric feverTyphoid and paratyphoid feversS. typhimurium, S. paratyphimuriumSystemic infectionInfects only humansGastroenteritisNon-typhi serotypesZoonosis: predominantly food-borneCan be complicated by septicaemiamore common with some serotypes, e.g. S. dublin (15% mortality rate when septicaemia in the elderly)
4 Epidemiology of Enteric fever Person-to-person spreadNo animal reservoirContamination with human faecesUsual vehicle is contaminated water – major sourceOccasionally, contaminated food (usually handled by an individual who harbours S. typhimurium)
5 Epidemiology of Non-typhoidal serotypes Zoonosis with enormous animal reservoirCommon animal reservoirs are chickens, turkeys, pigs, and cowsContaminated food is major vehicle, usually:Meat, raw eggs, milk & dairy productsCan follow direct contact with infected animals
6 Salmonella in eggsVarious Salmonella serotypes have been isolated from the outside of egg shellsS. enteritidis present inside the egg, in the yolkVertical transmissionDeposition of the organism in the yolk by an infected layer hen prior to shell deposition.
7 Infectious dose Typically about 1,000,000 bacteria Much lower if the stomach pH is raisedMuch lower if the vehicle for infection is chocolateProtects the bacteria in their passage through the stomachAn infectious dose of about 100 bacteria
8 Clinical Features; Enteric Fever Incubation period 10 to 14 daysSepticaemic illnessMyalgia and headacheFeverSpleenomegalyLeukopeniaAbdominal painRose spots (macular rash on abdomen)10% fatalSequelae (secondary result ): intestinal haemorrhage and perforation
9 Clinical features; Gastroenteritis Incubation period depends on doseSymptoms usually begin within 6 to 48 hoursNausea and VomitingDiarrhoeaAbdominal painMyalgia and headacheFeverDuration varies, usually 2 to 7 daysSeldom fatal, except in elderly or immunocompromised
10 Laboratory diagnosis Specimens Blood, urine & feces for culture Blood – detected in 75-90% of the patients in the first 10 days of infection, and 30% of the patients in the 3rd weekFaeces – can be isolated from 40-50% of patients in the 2nd week of infection & from about 80% of patients in the 3rd weekUrine – isolated from about 20% of patients after the 2nd week of infection
11 Laboratory DiagnosisEnrichment and selective media for Salmonella in faeces is Selenite brothDifferential media is XLD and SSAXLD-pink colonies with black centersSSA- black colonies with silver metallic sheen.
12 Laboratory Diagnosis Biochemical tests and serological tests Some other bacteria, e.g. Citrobacter, may have similar serological profilesCommercial kits commonly used, e.g. API20O, H serum analysis kitsTyping done for epidemiological purposesTo find source of outbreak
16 Treatment Gastroenteritis Replace fluid loss by oral and intravenous routesAntibiotics are not recommended for uncomplicated gastroenteritisdo not shorten illnessprolong excretionAntibiotic therapy reserved for the septicaemiaTyphoid fever and enteric fevers should be treated with antibioticsUsually ciprofloxacin; however, the concern issue is resistance
18 Prevention Public awareness Remove source Interrupt transmission Salmonella free chicks/livestockInterrupt transmissionGood food hygieneCook food properlyKeep raw and cooked foods apartPublic Health: clean waterStrengthen hostVaccination
19 Salmonella vaccinesVaccination of travellers against typhoid recommended, but does not remove need for good hygieneThree licensed vaccinesTraditional heat-killedvery reactogenicVi subunit vaccinelive oral vaccine, S. typhi Ty21ANo vaccines for gastroenteritis