Gram Positive GI Infections Flashcards
Describe the epidemiology of staph. aureus GI infection. Consider:
EPIDEMIOLOGY:
Transmission
Transmission:
-Contaminated food
Describe the pathogenesis of staph. aureus GI infection. (1)
- Staph. aureus produces enterotoxins (types A-E) which are heat stable and acid resistant
Describe the clinical features of staph. aureus GI infection. Consider:
a) Incubation period
b) Duration
c) Symptoms (2)
Incubation period: 30 mins - 6 hours
Duration: 12-24 hours
Symptoms:
- Profuse vomiting
- Abdominal cramps
Describe the microbiology and epidemiology of bacillus cereus infection. Consider:
MICROBIOLOGY
Structure
Growth conditions
EPIDEMIOLOGY:
Transmission
Types of B. cereus disease
MICROBIOLOGY Structure: gram positive bacilli Growth conditions: -Aerobic -Spore forming
EPIDEMIOLOGY Transmission: -Contaminated food Types of disease: -Emetic disease -Diarrhoeal disease
Describe the pathogenesis of emetic disease caused by bacillus cereus infection. Consider:
a) Which toxin causes this?
b) Which food is this commonly associated with?
c) Pathogenesis of disease?
Caused by: heat stabile toxin
Associated with: fried rice
Process:
- Spores survive intial boiling of rice
- Spores germinate, multiply and re-sporulate
- Sporulation produces heat stable enterotoxin (which survives frying)
Describe the pathogenesis of diarrhoeal disease caused by bacillus cereus infection. Consider:
a) Which toxin causes this?
b) Which food is this commonly associated with?
c) Pathogenesis of disease?
Caused by: heat labile toxin
Associated with: improperly heated food
Process:
- Spores survive cooking of food
- Spores germinate and multiply
- B. cereus is then ingested, and then produces heat labile toxin
Describe the clinical features of emetic disease caused by bacillus cereus infection. Consider:
a) Incubation period
b) Duration
c) Symptoms (3)
Incubation period: 30 mins - 6 hours
Duration: 12-24 hours
Symptoms:
- Profuse vomiting
- Abdominal cramps
- Watery diarrhoea
Describe the clinical features of diarrhoeal disease caused by bacillus cereus infection. Consider:
a) Incubation period
b) Duration
c) Symptoms (2)
Incubation period: 8-12 hours
Duration: 12-24 hours
Symptoms:
- Watery diarrhoea
- Cramping abdominal pain
Describe the microbiology and epidemiology of clostridium perfringens infection. Consider:
MICROBIOLOGY
Structure
Growth conditions
EPIDEMIOLOGY:
Transmission
MICROBIOLOGY Structure: -Spore forming -Gram positive bacilli Growth conditions: -Anaerobic
EPIDEMIOLOGY
Transmission:
-Contaminated food
Describe the pathogenesis of clostridium perfringens infection. (4)
- Spores survive cooking, then germinate and multiply in cooling food
- Food is inadequately reheated, so that organisms aren’t killed
- Ingested organisms sporulate in the large intestines
- Bacteria then produce enterotoxins
Describe the clinical features of clostridium perfringens infection. Consider:
a) Incubation period
b) Duration
c) Symptoms (2)
Incubation period: 6-24 hours
Duration: 12-24 hours
Symptoms:
- Watery diarrhoea
- Abdominal cramps
Describe the microbiology and epidemiology of clostridium botulinum infection. Consider:
MICROBIOLOGY
Structure
Growth conditions
EPIDEMIOLOGY:
Transmission
MICROBIOLOGY Structure: -Spore forming -Gram positive bacilli Growth conditions: -Anaerobic
EPIDEMIOLOGY
Transmission:
-Contaminated soil/animal bites
List the 3 types of botulism.
Describe the pathogenesis of botulism.
Foodborne botulism
Infant botulism
Wound botulism
- Bacteria produce heat labile neurotoxins (types A, B, E)
- Origin of toxin depends on type of botulism:
- Foodborne: preformed toxins in food
- Infant: germinating organisms in baby’s gut
- Wound: organisms enter wound (e.g. through soil)
Describe the clinical features of botulism. Consider:
a) Incubation period
b) Symptoms (2)
Incubation period: 12-36 hours
Symptoms:
- Neuromuscular blockade (flaccid paralysis; muscle weakness)
- Respiratory failure
Describe the diagnosis of clostridium difficile infection. (2)
Initial test:
- GDH test
- Toxin B gene PCR
Confirmation test:
- Toxin immunoassay
- Cell-culture cytotoxicity assay
Describe the pathogenesis of clostridium difficile infection. (2)
- Infection requires prior disruption of normal gut microflora, e.g. due to antibiotic therapy/cytotoxic therapy/PPIs
- Bacteria produce potent toxins (types A and B)
Describe the clinical features of C. diff infection. Consider:
a) Incubation period
b) Duration
c) Symptoms
d) Complications of severe C. diff infection
Incubation period: 0-7 days
Duration: up to weeks
Symptoms:
-Abdominal pain
Complications:
- Pseudomembranous colitis
- Bowel perforation
What are the 5 severity criteria which indicate severe C. diff infection?
Colonic dilatation: 6+ cm WCC: 15+ Creatinine: 1.5x increase Temp: 38.5C Immunosuppression
Describe the treatment of C. diff infection. Consider:
a) Mild-moderate C. diff
b) Severe C. diff
MILD-MODERATE C. DIFF:
- Strop precipitating antibiotics
- Oral metronidazole (5 days)
SEVERE C. DIFFF:
- Stop precipitating antibiotics
- Oral vancomycin
- Faecal transplant
What are the 4 high risk antibiotics which may cause C. diff infection?
Cephalosporins
Ciprofloxacin
Clindamycin
Co-amoxiclav
Describe the microbiology and epidemiology of listeria monocytogenes infection. Consider:
MICROBIOLOGY
Structure
EPIDEMIOLOGY:
Transmission
At risk populations
MICROBIOLOGY
Structure: gram positive coccobacilli
EPIDEMIOLOGY Transmission: -Contaminated food At risk populations: -Pregnant women -Elderly -Immunocompromised
Describe the pathogenesis of listeria monocytogenes infection. (1)
- Can cause invasive and metastatic infection
Describe the clinical features of listeria monocytogenes infection. Consider:
a) Incubation period
b) Duration
c) Symptoms (3)
d) Complications (2)
Incubation period: 3 weeks
Duration: 1-2 weeks
Symptoms:
- Flu-like illness
- With/without diarrhoea
- Severe systemic infection
Complications:
- Septicaemia
- Meningitis
