Gram Negative GI Infections Flashcards
List 7 gram negative bacteria which cause GI infection.
Campylobacter Salmonella Shigella Vibrio cholera E. coli Yersinia enteroclitica H. pylori
Describe the microbiological features and epidemiology of campylobacter. Consider:
MICROBIOLOGY:
Structure
Growth conditions
Types of campylobacter
EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs
MICROBIOLOGY Curved gram negative bacilli Growth conditions: -Microaerophilic -Thermophilic (42C) Types of campylobacter: -C. jejuni
EPIDEMIOLOGY Seasonal peaks in May/September Transmission: -Contaminated food (esp poultry) -Contaminated milk/water Outbreaks: rare Animal reservoirs: numerous (e.g. poultry, cattle, sheep)
Describe the pathogenesis of campylobacter infections. (2)
- Inflammation, ulceration and bleeding in small/large intestines
- May cause bacteraemia, e.g. in
a. Extremes of age
b. Immunocompromised patients
Describe the clinical features of campylobacter infection. Consider:
a) Incubation period
b) Duration
c) Symptoms
d) Complications
Incubation period: 2-5 days
Duration: 2-10 days
Symptoms:
- Bloody diarrhoea
- Abdominal cramps
- Fever
Complications:
-Guillain-Barré syndrome
How is campylobacter infection treated? Consider:
a) Severe/prolonged infection
b) Invasive infection
SEVERE INFECTION:
Clarithromycin
INVASIVE INFECTION:
Quinolones
Aminoglycosides (e.g. gentamicin)
List the 6 types of E. coli which cause diarrhoea.
Enteropathogenic (EPEC) Enterotoxigenic (ETEC) Enterohaemorrhagic (EHEC) Enteroinvasive (EIEC) Entero-aggregative (EAEC) Diffuse-aggregative (DAEC)
Describe the epidemiology of:
a) Enteropathogenic E coli
b) Enterotoxigenic E coli
c) Enterohaemorrhagic E coli
EPEC:
Sporadic
ETEC:
Major cause bacterial diarrhoea
EHEC:
Quite rare
Describe the pathogenesis of diarrhoea in enteropathogenic E coli infections. (3)
- Bacteria adhere to gut mucosal cells via pilli
- This forms an “attaching and effacing” lesions
a. Mediated by intimin and Tir (translocated intimin receptor)
b. Tir is produced by EPEC, then injected into gut cells - This causes disruption of intestinal microvilli
List the clinical features of enteropathogenic E coli (EPEC). Include:
a) Incubation period
b) Duration
c) Symptoms (4)
Incubation period: 1-2 days
Duration: 1-several weeks
Symptoms: Watery diarrhoea Abdominal pain Vomiting Fever
Describe the pathogenesis of enterotoxigenic E coli (ETEC). (2)
- Heat labile toxin (LT)
a. Analogue of cholera toxin; similar symptoms
b. Destroyed by heat - Heat stable toxin (ST)
a. Similar mode of action to LT
b. NOT destroyed by heat
Describe the clinical features of enterotoxigenic E coli (ETEC). Include:
a) Incubation period
b) Duration
c) Symptoms (3)
Incubation period: 1-7 days
Duration: 2-6 days
Symptoms:
Watery diarrhoea
Abdominal pain
Vomiting
Describe the pathogenesis of enterohaemorrhagic E coli (EHEC). (4)
- Bacteria adhere to gut mucosal cells via pili
- This forms an attaching and effacing lesion
a. Mediated by: intimin and Tir (translocated intimin receptor) - EHEC produce shiga-like toxins, which damage the intestinal epithelium
a. May also damage glomerulus, causing renal failure - EHEC produce other toxins:
a. Shiga toxin (STEC)
b. Verotoxin (VTEC)
Describe the clinical features of enterohaemorrhagic E coli (EHEC). Include:
a) Incubation period
b) Duration
c) Symptoms
d) Complications
Incubation period: 1-7 days
Duration: 5-10 days
Symptoms:
Blood diarrhoea
Vomiting
Abdominal pain
Complications:
Haemolytic uraemic syndrome
Describe the microbiological features and epidemiology of salmonella. Consider:
MICROBIOLOGY:
Structure
Types of salmonella
EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs
MICROBIOLOGY Structure: -gram negative bacilli -non-lactose fermenters Types of salmonella: -S. enterica -S. typhi -S. paratyphi
EPIDEMIOLOGY Transmission: -Contaminated food -Person-person Outbreaks: -Frequent (bc CAN multiply in food) Animal reservoirs: -Multiple
Describe the pathogenesis of salmonella infection. (3)
- Bacteria invade epithelial cells in the distal small intestine, causing inflammation and diarrhoea
- Bacteraemia may occur in vulnerable patients
- Metastatic infection may occur, causing:
- Osteomyelitis
- Septic arthritis
- Meningitis
Describe the clinical features of salmonella infection. Consider:
a) Incubation period
b) Duration
c) Symptoms (3)
d) Complications (3)
Incubation period: 12-72 hours
Duration: 2-7 days
Symptoms:
Watery diarrhoea
Vomiting
Fever
Complications:
Osteomyelitis
Septic arthritis
Meningitis
Describe the microbiological features and epidemiology of shigella. Consider:
MICROBIOLOGY:
Structure
Growth conditions
Types of shigella
EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs
MICROBIOLOGY Structure: -Gram negative bacilli -Non-lactose fermenter Types of shigella: -S. sonnei -S. boydii -S. flexneri -S. dysenteriae
EPIDEMIOLOGY Transmission: -Person-person -Faeco-oral Outbreaks: -Frequent (bc person-person transmission) Animal reservoirs: -None except humans
Describe the pathogenesis of shigella infection.
- Organisms attach to and colonise the mucosal epithelium of the terminal ileum/colon
- Produce Shiga toxin, which damages the intestinal epithelium
a. Also targets glomerular endothelium
b. Therefore can cause renal failure and HUS
Describe the clinical features of shigella infection. Consider:
a) Incubation period
b) Duration
c) Symptoms (3)
d) Complications (2)
Incubation period: 1-3 days
Duration: 2-7 days
Symptoms:
- Initial watery diarrhoea (then becomes bloody)
- Cramping abdominal pain
- Fever
Complications:
- Renal failure
- Haemolytic uraemic syndrome (HUS)
Describe the microbiological features and epidemiology of vibrio cholerae. Consider:
MICROBIOLOGY:
Structure
Growth conditions
Types of v. cholerae
EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs
MICROBIOLOGY Structure: -Comma shaped gram negative bacilli -Sucrose fermenter Types of v. cholerae: -Serotype O1 (El Tor) -Serotype O139 -Vibrio parahaemolyticus
EPIDEMIOLOGY Transmission: -Contaminated food/water Outbreaks: -Endemic in SE Asia, Africa, S America Animal reservoirs: -None except humans
Describe the pathogenesis of cholera. (3)
- Bacteria penetrate the intestinal mucous (via flagella and mucinase enzymes)
- Bacteria attach to mucosa via specific receptors
- Bacteria produce cholera toxin (CTX)
a. This causes diarrhoea
Describe the clinical features of cholera. Consider:
a) Incubation period
b) Symptoms (2)
c) Complications (4)
Incubation period: 12 hours - 5 days
Symptoms:
- Severe and profuse watery diarrhoea (rice water stool)
- Dehydration
Complications:
- Hypokalaemia
- Metabolic acidosis
- Hypovolaemic shock
- Cardiac failure
How is cholera treated? (2)
State administration for any drugs given.
Rehydration therapy (oral or IV)
Tetracycline antibiotics (oral or IV)
Describe the microbiological features and epidemiology of campylobacter. Consider:
MICROBIOLOGY:
Structure
EPIDEMIOLOGY:
Transmission
Outbreaks
Animal reservoirs
MICROBIOLOGY
Structure:
-Gram negative bacilli
EPIDEMIOLOGY Transmission: -Raw/undercooked pork -Pasteurised milk (can survive/multiple in fridge temperatures) Animal reservoirs: -Include pets
