bacterial food poisoning
TRANSCRIPT
LECTURE ON FOOD POISONING
BY
DR . Hussain AliSr.LECTURER
DEPARTMENT OF FORENSIC MEDICINEDOW UNIVERSITY OF HEALTH SCIENCES
KARACHI
This is of two types:-1. Toxin Type (from staphylococcus, streptococcus and botulinism).
Infection organism)2. Infection Type (salmonella group of
organism)
Bacterial food poisoning
Food poisoning due to bacterial toxins is most commonly caused by the exotoxins produced by the staph. Phyogenes, which in the great majority of instances, is transferred by a food handler who has a septic lesion of the hands or who is a carrier of the organisms in his nose or throat.
Toxin Type
The exotoxin is very resistant to heat and is not destroyed by cooking. The toxin type of food poisoning is less common due to hemolytic and nonhaemolytic streptococci and very rarely due to anaerobic spore formatting organism , with minimal gastrointestinal disturbance. Symptoms appear in 1-3 days. Usually after taking infected sausages; tinned fish etc.
The organisms mainly responsible belong to the salmonella group which has its natural reservoir in certain birds, mammals and reptiles. Salmonella typhimurium has been found to be the organism causing majority of the cases of this type of food poisoning. Food may be contaminated with infected excreta of mice or rats etc., or infection may be transferred by flies or by human carriers employed in handling of food. The possibility that the infection is due to a virus should be remembered.
Infection Type
ORGANISMS CAUSING BACTERIAL FOOD POISONING
After bacterial contamination of the food, there is danger of bacterial multiplication at a warm temperature, as in a kitchen for many hours or even days. This type of food which is likely to be infected are twice cooked meat dishes, stews, gravie soups, custards, milk, cream, also tinned food though usually initially sterile may become infected, if not immediately consumed after the tin has been opened.
Duck’s eggs are quite commonly infected because the duck is a carrier of Salmonella organisms in its oviduct and alimentary tract. While hen’s eggs are rarely infected. Hence duck’s eggs are not suitable for preparation of lightly cooked foods such as custards, milk puddings etc., because boiling for 10-15 minutes is necessary if sterilization is to be secured.
Outbreaks of food poisoning are liable to occur when large amounts of food are prepared and when the remaining food is not consumed is kept for future meals. The danger of infection is greatly increased if such food is kept in a warm temperature instead of being stored in a refrigerator. Food poisoning is reported frequently from canteens, restaurants, and other institutions than from private houses .
In food poisoning; it is common to find other members of the household or institution affected simultaneously. The incubation period of different types is a useful pointer to their etiology. If vomiting starts after taking a poisonous food:-Within half hour, is likely to be a chemical
poison.Within six hours, it is probably bacterial toxins.12 to 48 hours later, it is probably due to
salmonella infection. There is toxaemia and gastroenteritis resulting from bacterial infection.
Symptoms
The symptoms in any single outbreak vary widely in severity depending on the type and the amount of poisonous substance ingested and the susceptibility (particularly in salmonella) of individuals. The principal symptoms are nausea, vomiting, diarrhea and abdominal pain. Sometimes chill and headache are initial symptoms in salmonella food poisoning. In severe cases there may be prostration, collapse and signs of dehydration.
In chemical and toxin type of food poisoning, the onset tends to be sudden and severe and the patient rapidly passes into a state of collapse and frequently has subnormal temperature. Recovery however usually occurs within 24 hours after treatment.
In chemical and Toxin type of food poisoning
In the infection type of food poisoning (due to salmonella), symptoms develop more slowly and there may be a rise in temperature. The patient may be ill for several days. The stools are watery and offensive, and there may be little blood and some mucus, in contrast to bacillary dysentery where there is in addition much pus.
This type is differentiated from staphylococcal enterotoxin by three characteristics: 1. Muscular weakness2. Fever Very foul smelling diarrhea.The most important point to decide, especially in children is whether a surgical condition (As. Appendicitis, intestinal obstruction etc.) is present
Collect patient’s faeces, vomit and suspected food and send to the pathological laboratory and the chemical examiner (for chemical poison) Isolation of bacteria (salmonella group) by culture and agglutination test, if positive Health Officer be informed. After death isolate bacteria from bowel.
Investigations
Most cases are mild and can be treated with rest in bed, warmth and plenty of fluid drinks. Moderately or severely ill showing signs of collapse and dehydration should be admitted in hospital for proper treatment and nursing; treat by:
Treatment
1. Wash out stomach2. Give saline purgative if necessary3. I.V. dextrose saline4. Stimulants if necessary5. Stop food by mouth until the acute symptoms
are over and give fluids fruit juices, tea etc. On improvement semisolid food is taken
6. For diarrhea give Kaolin 15g doses two hourly suspended in water
7. Antibiotic – Chloromphenical 2 g daily for about 5 to 7 days
8. Antitoxic (anti-botulinus) serum in Botulism.
• Coordinate with public health during initial threat assessment and investigation
• Contact and coordinate with Bureau of Investigation
• Conduct criminal investigation.• Ensure collection of evidence in manner
that is admissible in court.
Role of a forensic pathologist.
Investigators in both law enforcement and environment will also have to work together to find
the answers to the following questions:• How would perpetrators gain access to
food?• How could a pathogen be introduced?• How was the agent mixed or
distributed?• How might the pathogen spread in the
environment
The main objectives of laboratory analysis during outbreak investigations are (1) to confirm the
clinical diagnosis through identification of the causative agent from human specimens, (2) to
ensure proper identification of the disease, and (3) to determine if the causative agent is present
in the implicated environmental source, such as food.
collection of clinical specimens as early in the course of the
investigation as possible. Most foodborne infections are diagnosed through the identification of
the pathogen in stool collected from infected persons.
Vomitus has also been used to detectcertain organisms and confirm the etiology.
Serology and blood cultures are recommended for
the laboratory diagnosis of systemic infections.
Stool Specimens.Proper collection of stool specimens requires
having stool kits readily available, using theappropriate kit for the suspected disease, and
encouraging ill persons to submit a stool specimen.