In this article we will discuss about Bacterial Food Poisoning:- 1. Meaning of Bacterial Food Poisoning 2. Classification of Bacterial Food Poisoning 3. Food Borne Botulism 4. Source of Infection 5. Pathogenesis 6. Clinical Features 7. Diagnosis 8. Non-Bacterial Infective Diarrhoea 9. Laboratory Diagnosis.
- Meaning of Bacterial Food Poisoning
- Classification of Bacterial Food Poisoning
- Food Borne Botulism
- Source of Infection
- Pathogenesis of Bacterial Food Poisoning
- Clinical Features of Bacterial Food Poisoning
- Non-Bacterial Infective Diarrhoea
- Laboratory Diagnosis of Bacterial Food Poisoning
1. Meaning of Bacterial Food Poisoning:
The term “Bacterial food poisoning” is referred to acute gastroenteritis that results from the presence of bacteria, usually in large numbers, or the products (toxin) in food. Contamination of food occurs either at source or during preparation of food.
2. Classification of Bacterial Food Poisoning:
It may be divided into three types:
A. Infection type in which multiplication of the organism occurs in vivo, e.g Salmonella;
B. Toxin type in which the disease follows ingestion of food with preformed toxin, e.g. staphylococcal entero-toxin, and
C. Intermediate type in which bacteria release the toxin in the bowel, e.g. CI. perfringens.
A. Infection Type:
1. Salmonella sp. (S. typhimurium, S. enteritidis, S. Thompson)
2. Campylobacter jejuni
3. Vibrio parahaemolyticus
4. Vibrio mimicus.
B. Toxin type:
1. Staphylococcus aureus
2. Bacillus cereus.
C. Intermediate type:
1. CI. perfringens type A
2. E. coli verocytotoxigenic (neurocytotoxin producing)
3. Clostridium botulinum.
3. Food Borne Botulism:
It is a severe, often fatal/form of food poisoning which is due to the ingestion of preformed toxin in food contaminated with CI. botulinum. It is characterised by pronounced neurotoxic effects. Incubation period ranges from 1-2 days. There may be initial nausea, vomiting and abdominal pain but no diarrhoea.
4. Source of Infection:
CI. botulinum is widespread in nature and its spores can withstand boiling in water (100°C) for several hours. This illness has been associated with home canned food ingestion.
5. Pathogenesis of Bacterial Food Poisoning:
Antigenically there are seven types of CI. botulinum (A-G) which produce antigenically distinct toxins with pharmacologically identical actions. Toxin types A, B, E are mostly associated with human disease and, rarely, F is responsible.
Botulinum toxin (neurotoxin), whether ingested or produced in the intestine, is absorbed from the intestinal tract and enters the vascular system and is transported to peripheral cholinergic nerve terminals and blocks the release of acetylcholine.
6. Clinical Features of Bacterial Food Poisoning:
Cranial nerve involvement is an indication of the onset of symptoms and affects the oculomotor muscles leading to diplopia and drooping eyelids with a squint. There may be vertigo, blurred vision and dry mouth. There is progressive symmetric descending flaccid paralysis that may lead to respiratory failure and death.
Food, vomitus, faeces, and blood.
Toxin in the specimen may be detected by toxin-anti-toxin neutralisation test in mice.
8. Non-Bacterial Infective Diarrhoea:
In addition to bacterial diarrhoea, viral, fungal, and protozoal diarrheas are also encountered in human beings.
9. Laboratory Diagnosis of Bacterial Food Poisoning:
(a) Saline Preparation:
1. Amoebic dysentery-cyst and motile trophozoites of E.histolytica .
2. Giardiasis. G. lamblia cysts in formed stool or trophozoites in fresh stools, duodenal, secretions or jejunal biopsies.
(b) Iodine Mount:
1. Amoebiasis and giardiasis-cysts take up iodine and appear distinct.
2. Balantidium coli-cysts in formed or trophozoites in fresh stool.
3. Cryptosporidium-Oocyst excretion maximum during first 3-5 days of illness, 5 µm diam , oocytes fail to take up iodine stain.
(c) Acid fast Staining:
It shows acid fast oocyst of Cryptosporidium in stained faecal smear.
(d) Electron Microscopy of Faeces:
Morphology of virus particles can be demonstrated.
B. Serological Tests:
1. Amoebiasis—Significant antibody titre persists for months after cure. Indirect haemagglutination and ELISA are most sensitive.
2. Viruses in stool can be detected by fluorescent antibody and ELISA test.