Bact GI 1 Flashcards
Describe bacterial food poisoning
Two types:
1) toxins produced BY bacteria in food before the food is consumed
2) Large # of spores ingested, spores germinate in intestine and vegetative bacteria produce toxins
- Cause diarrhea, vomiting or both (NO FEVER)
Four bacterial causes:
Staph. Aureus, Clostridium botulinum, Clostridium perfringens, Bacillus cereus.
Describe characteristics of Staphylococcus Aureus
- Gram + cocci in clusters
- Not spore forming
BACTERIAL FOOD POISONING - Ingestion of a preformed toxin
- Severe vomiting, diarrhea and abdominal pain WITHIN 1-8 hours after consumption
–> HEAT-STABLE TOXIN
TREATMENT = Supportive therapy
Describe characteristics of Clostridium botulinum
- Gram + rod
- SPORE FORMING!!
BACTERIAL FOOD POISONING - Botulism mediated by botulism toxin
- Early symptoms = vomiting, diarrhea, abdominal pain 1-8h post ingestion
- Late symptoms = FLACCID PARALYSIS –> progressive muscle weakness and respiratory distress
TREATMENT = supportive therapy + IV anti-toxin administration
Describe the pathogensis of Clostridium botulinum
- ingestion of preformed toxin and large # of spores –> germinate in intestine –> produce toxin
- BOTULISM TOXIN = acts at Neuromuscular nerve jxns
- -> blocks acetylcholine release, thus muscle stimulation is blocked
Describe characteristics of Clostridium perfringens
- Gram + rod
- SPORE FORMING!!!
BACTERIAL FOOD POISONING - mediated by C. perfringens ENTEROTOXIN
- associated with contaminated MEAT PRODUCTS/GRAVIES
- SYMPTOMS = diarrhea and abdominal cramps 8-16h POST INGESTION and lasts 24h
TREATMENT = supportive therapy
Describe the pathogensis of Clostridium perfringens
1) C. Perfringens spores survive cooking of food
2) bacteria grow in food (not kept at proper heat)
3) ingestion of organism
4) organism sporulate in the intestine
5) sporulation leads to ENTEROXIN production
6) Toxin ALTERS enterocyte membrane permeability
7) DIARRHEA!!!!!!
Describe the characteristics of Bacillus cereus
- Gram +
- SPORE FORMING
BACTERIAL FOOD POISONING
TWO FORMS:
1) Emetic form: associated with improper storage of cooked rice
2) Diarrheal form: associated with Mean, vegitables
TREATMENT = supportive therapy
Describe the differences of Emetic vs Diarrheal form of bacillus cereus
EMETIC FORM:
- vomiting, nausea and abdominal craps 1-8h AFTER INGESTION
- Ingestion of PREFORMED heat-stable ENTEROTOXIN
- Associated with improper storage of cooked rice
DIARRHEAL FORM:
- DIARRHEA, nausea and abdominal cramps 8-16h AFTER INGESTION of contaminated food
- PRODUCTION of heat-liable ENTEROTOXIN in intestines
Describe characteristics of Helicobacter Pylori
- Gram - curved rod
- Microaerophilic (5% oxygen)
STOMACH - symptoms = ulcers, chronic gastritis
DIAGNOSIS via UREA BREATH TEST or BIOPSY
TREATMENT (after positive test for H. pylori) = combo of antibiotics + proton pump inhibitor
Describe the pathogenesis of Helicobacter Pylori
1) H. Pylori penetrate the mucous layer lining of the stomach’s epithelium (attrached to the chemotactic substances hemin and urea)
2) H. pylori recruit and activate inflammatory cells. It releases UREASE that cleaves urea, producing NH3 that neutralizes stomach acid in its vicinity
3) H. Pylori CYTOTOXIN and the AMMONIA produced by its UREASE, cause destruction of the mucus-producing cells, exposing the underlying CT to stomach acid and leads to ulcers
Describe the characteristics of Listeria monocytogenes
- Gram + facultative anaerobic
- short rods
- Intracellular pathogens
SURVIVAL TRAITS = wide growth range (cold loving), resistant high salt conc. and wide pH range - Contaminated food is primary source
- Human transmission from mother to fetus
Describe the Clinical manifestations of Listeria Monocytogenes
HEALTHY ADULTS = Asymptomatic, but may have fever, nausea, diarrhea
IMMUNOCOMPROMISED:
- Bacteremia = fever, malaise and chills with no obvious focus
- Meningitis and encephalitis = Fever, persistent headache, stiff neck, vomiting and/or confusion (20-50% mortality)
PREGNANT WOMEN = develop nausea, fever, diarrhea; risk of transmission to neonate
NEONATAL INFECTION = Granulomatosis infantiseptica (pyogenic granulomas distributed over the whole body), Meningitis, Encephalitis (2-3 weeks after birth)
Describe the Pathogenesis of Listeria Monocytogenes
1) Adherence and induced uptake mediated by: Internalin-A (IntA)
2) Internalized into an endocytic vacuole
3) Acidification of vacuole/phagosome activates LISTERIOLYSIS O (LLO) which causes disruption of vacuole membrane to allow for escape to the cytosol
4) Replication in the host cell cytosol
5) ActA mediated ACTIN POLYMERIZATION causes spreading to neighboring cells and blood stream causing:
* * DISSEMINATED INFECTION (Liver, spleen, CNS)**
Describe the diagnosis of Listeria monocytogenes
- Microscopy of clinical samples is Insensitive (too few bacteria, other Gram + bacteria cause bacteremia and infect the CNS)
- Culture of cerebral spinal fluid and blood
- -> cold enrichment selection (grows in cold temps.)
- -> weak Beta-hemolysis on blood agar
- -> Motility Test
Describe the treatment and prevention of Listeria monocytogenes
Treatment: Beta-lactams or Trimethoprim-sulfamethoxazole
Prevention: NO VACCINE
- properly cook animal products including ready-to-eat meats, wash raw vegetables (especially if immuno-compromised or pregnant
