Bacterial GI Intoxications
Buxton Lecture 2/3 11 am
Foodborne intoxications
Foodborne intoxications
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- How can food borne infxns be prevented?
- Proper food handling; thoroughly cook; do not leave food at room temp for > 2 hours; refrigerate promptly
- Diagnosis of patient who developed nausea and vomiting 2 hours after eating rice at Chinese buffet:
- Bacillus cereus
- S/S and pathogenesis of Diarrheal form of B. cereus infxn:
- Due to heat-labile toxin; incubates 4-16 hours; causes abd pain and diarrhea; symptoms last 12-24 hours
- What organism causes only diarrhea when toxin is present in food?
- Clostridium perfringens
- What are the clinical manifestations of Staphylococcal food poisoning?
- Begin 1-6 hours after ingestion; N/V with abdominal pain; Diarrhea less frequent, but it would be watery (w/o blood); lasts less than 24 hours
- Pathogenesis of C. botulinum:
- Neurotoxin blocks release of ACh in NMJ
- Which type of C. perfringens causes necrotizing enteritis? What toxins does it produce?
- Type C -- very serious, but not extremely common; produces alpha and beta toxin
- What is alpha toxin and what does it do?
- phospholipase C (lecithinase), necrotizing activity, hemolysin, increases vascular permeability
- Characteristics of C. perfringens:
- Inhabitant of intestinal tract (humans and cattle); common in water and soil; spore-forming, anaerobic gram (+) rods
- What are the most common soft tissue infections caused by C. profringens?
- Cellulitis, Fasciitis, and Myonecrosis (gas gangrene)
- Most common foods in which Staph toxin grows in to cause food poisoning:
- Foods prepared by hand w/o cooking; high salt or sugar content, like ham, custards, macaroni or potato salad
- S/S and pathogenesis of Emetic form of B. cereus infxn:
- Heat stable toxin (similar to staph enterotoxin); incubates 1-5 hours; acute attack of nausea and vomiting
- Which type of C. perfringens is most common human disease causer? What toxins does it produce?
- Type A C. perfringens most commonly causes soft tissue infxns, food poisoning and septicemia; it produces alpha toxin and enterotoxin
- What organisms cause vomiting and diarrhea when toxins are in ingested food?
- Staphylococcus aureus and Bacillus cereus
- S/S of Clostridium botulinum:
- N/V and abd pain; later development of diplopia, dysarthria and respiratory impairment; may see abn CN, including extraocular motor palsy and diffuse flaccid paralysis
- What is enterotoxin and what does it do?
- heat-labile toxin; causes alteration of membrane permeability, loss of ions and water
- Characteristics of B cereus:
- Aerobic spore-forming rod; spores withstand heating; grows in foods that are prepared and left out for several hours w/o refrigeration
- What types of infxns can be caused by C. perfringens?
- Soft tissue infxn; food poisoning; necrotizing enteritis; septisemia
- Conditions that promote growth of C. botulinum spores:
- Absence of oxygen; low acidity (pH > 4.6); temp > 39F; high moisture content
- Presentation of Clostridium botulinum:
- Exposure to home-canned products (pickled-eggs); symptoms begin 12 hours after ingestion
- Where does S. aureus normally colonize in many people?
- Nasopharynx
- What are the two types of Bacillus cereus illnesses?
- Diarrheal form and Emetic form
- How does C. perfringens cause food poisoning? S/S?
- Intoxication by enterotoxin; incubates in 8-24 hours; causes watery diarrhea and abd cramps, usually W/O FEVER OR VOMITING
- What organism has a neurotoxin that produces flaccid paralysis when toxin is present in ingested food?
- Clostridium botulinum
- What is the treatment of food borne infxns?
- Supportive; NO ANTIBIOTICS -- b/c illness is toxin-mediated
- What agent is a "reportable disease" causing food poisoning?
- Staphylococcal food poisoning
- What is not necessary in foodborne intoxications?
- Infection is not necessary -- toxins in food lead to diarrhea/disease w/o fever or vomiting
- Causes of infantile botulism:
- Ingestion of spores in honey; infants lack normal flora in intestinal tract that inhibits spore germination
- What two agents that cause food poisoning are spore-formers?
- Bacillus and Clostridium
- Pathogenesis of Staphylococcal Food Poisoning:
- Food contaminated with enterotoxin (A-E are superantigens); after contamination, bacteria grow and produce toxin in food left at room temp for few hours; toxin is heat stable and resists cooking
- S/S of food poisoning from Clostridium perfringens infxn:
- Abd cramps and diarrhea; incubates in 12 hours (range 2-48 hours)