Etiology and Pathogenesis of Bacterial Food Poisoning
The diseases develop upon ingestion of food containing accumulated toxins of opportunistic bacteria.
Main pathogens and their toxins:
- Staphylococcus aureus: produces exclusively heat-stable enterotoxins. Characterized by an ultra-short incubation period (sometimes 30–45 minutes, usually up to 12 hours).
- Clostridium perfringens: produces only a heat-labile enterotoxin.
- Bacillus cereus: can produce both types of enterotoxins (simultaneously or separately).
Important: Generalized forms do not develop in bacterial food poisoning. The clinical picture directly depends on the type of toxin: heat-stable toxins cause a gastritis-like picture, whereas heat-labile toxins cause enteritis. When a massive dose of heat-stable toxin enters the bloodstream, a superantigen effect is possible, leading to shock-like reactions with a sharp drop in blood pressure disproportionate to the dyspepsia.
Clinical variants
The symptom complex consists of gastrointestinal tract lesions, water-electrolyte disturbances, and mild intoxication. Two main clinical variants are distinguished:
- Gastritic Variant
Characterized by an acute onset against a background of complete health. Nausea and repeated vomiting predominate, bringing short-term relief. Diarrhea syndrome is absent, and body temperature usually remains normal. Dehydration does not exceed grade I–II; the course is predominantly mild.
- Gastroenteritic Variant
The most frequent form. Manifests as nausea, vomiting, and abdominal pain (epigastric and periumbilical regions). Copious, watery stool joins, which rapidly loses its fecal character (no admixture of blood or pus). Disease severity strictly correlates with the degree of dehydration (can reach grade III), which always predominates over the intoxication syndrome.
According to severity, mild courses are distinguished (single vomiting, stool up to 3 times, grade I dehydration), moderate (repeated vomiting, stool up to 10 times, tachycardia, grade II dehydration), and severe (shock, stool over 20 times, convulsions, oliguria).
Differential diagnosis
The diagnosis is established based on clinical and epidemiological data: a short incubation period, group nature of the outbreak, absence of prolonged fever. The disease must be differentiated from other infections:
- Viral Gastroenteritis (rotaviruses, noroviruses, intestinal adenoviruses): frequently occur as outbreaks in organized children's groups. Characterized by moderate, short-term intoxication, dominance of vomiting over diarrhea, and absence of marked abdominal pain. Confirmed by coprofiltrate latex agglutination assay.
- Cholera: begins strictly with diarrhea (without preceding nausea and abdominal pain); vomiting joins later. Stool is watery and non-fecal. Fever is absent, and dehydration rapidly develops up to grade IV.
- Botulism: dyspeptic syndrome is weak and short-lived. Progressive muscle weakness, dryness of mucous membranes without thirst, and ophthalmoplegic symptoms (mydriasis, diplopia, ptosis) rapidly come to the forefront.
Laboratory diagnostics and treatment principles
The basis of laboratory diagnosis is bacteriological examination of gastric lavage fluid, vomit, and feces. Serological tests are not performed because the pathogens lack invasive properties, antigenic stimulation is minimal, and the disease itself resolves faster than antibodies are produced. The hemogram has no diagnostic value.
Principles of treatment:
- Etiotropic therapy (antibiotics) is not performed.
- Gastric lavage: with sodium bicarbonate solution (2%) or potassium permanganate (0,1%) until clear water. Contraindicated in coronary artery disease, cerebral atherosclerosis, hypertension, and gastric ulcer.
- Enterosorption: for the elimination of unabsorbed toxins.
- Rehydration: exclusively with polyionic solutions (orally or parenterally). Colloidal solutions are not indicated.
- Diet: in the acute period, diet No. 4 is prescribed; as diarrhea subsides, diet No. 13.
- Probiotics during the convalescence period are not indicated, as the diarrhea is non-inflammatory in nature.
Briefly: answers to topical questions
Which specific polyionic crystalloid solutions are used for oral and parenteral rehydration in food poisoning?
Rehydration therapy for bacterial food poisoning is carried out exclusively with polyionic solutions, the choice of which depends on the route of administration.
- Oral rehydration — glucose-salt solutions are used (e.g., Regidron, Citraglucosolan, and other similar preparations).
- Parenteral rehydration — specialized solutions are used: Quatasol, Acesol, Lactasol, and Trisol.
It is important to note that colloidal solutions are not indicated for these purposes.
What is the transmission mechanism and main clinical periods of viral hepatitis A?
Viral hepatitis A belongs to viral hepatitis with an enteral, fecal-oral transmission mechanism.
The clinical course of acute viral hepatitis includes:
- Pre-icteric period — may manifest with flu-like, dyspeptic, arthralgic, or asthenovegetative syndromes.
- Icteric period — with the appearance of jaundice, the symptoms of the pre-icteric period disappear. For hepatitis B, unlike hepatitis A, it is noted that intoxication does not resolve with the appearance of jaundice, but persists or worsens.
Which serological markers are used to confirm the acute phase of viral hepatitis A?
To confirm the acute phase of viral hepatitis A as part of specific etiological diagnostics, the determination of class M immunoglobulins to the pathogen is used. The main serological marker is anti-HAV IgM. A negative test result for this marker reliably excludes the development of acute viral hepatitis A during the differential diagnosis of jaundice syndrome.
Heat-stable toxin = Gastritis (vomiting, short incubation). Heat-labile toxin = Enteritis (diarrhea).
Class and exam questions
Why are antibiotics not used in food poisoning?
Etiotropic therapy is not indicated, as the clinical presentation is due to the action of pre-formed bacterial exotoxins ingested with food, rather than systemic tissue invasion by the pathogen.
Which solutions are contraindicated for rehydration in food poisoning?
The use of colloidal solutions is strictly contraindicated. Rehydration must be carried out exclusively with polyionic glucose-salt solutions.
What is the main clinical difference between food poisoning and cholera?
In cholera, the disease begins with profuse diarrhea without abdominal pain, and vomiting joins later. In food poisoning, the onset is accompanied by nausea, vomiting, and epigastric pain.
What else to study on this topic
- Mechanism of action of Staphylococcus aureus superantigens and development of hypovolemic shock
- Assessment of acid-base balance (ABB) and blood electrolytes in severe dehydration
- Differential diagnosis of abdominal pain syndrome with acute surgical pathology
- Specific ophthalmoplegic symptoms in foodborne botulism
- Principles of calculating infusion therapy volume with polyionic solutions
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