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MBChB3 > Bacterial GI Infections > Flashcards

Bacterial GI Infections Flashcards

1
Q

Define gastroenteritis

A

A syndrome characterised by GI symptoms including nausea, vomiting, diarrhoea, and abdominal discomfort

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2
Q

Define diarrhoea

A

Frequent and/or fluid stool, at least 3 episodes a day

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3
Q

Define dysentery

A

Blood and pus in the stool, usually with abdominal pain and fever. More common in infection from abroad.

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4
Q

Define enterocolitis

A

Inflammation involving mucosa of both small and large intestine

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5
Q

What is used to monitor diarrhoea in hospital?

A

Bristol stool chart

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6
Q

How can GI infections manifest?

A

Within GI: toxin effects (eg. Cholera), and inflammation due to microbial invasion (eg. Shigellosis)

Outwith GI: systemic effects of toxins (eg. Shiga toxin produced by E.coli), and invasive infection of GIT with wider spread (eg. Metastatic salmonella infection)

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7
Q

What are the barriers to GI infection in the mouth?

A

Lysozyme

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8
Q

What are the barriers to GI infection in the stomach?

A

Acid PH

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9
Q

What are the barriers to GI infection in the small intestine?

A
  • mucous
  • bile
  • secretory IgA
  • lymphoid patches (Peyer)
  • high epithelial turnover
  • normal flora
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10
Q

What are the barriers to GI infection in the large intestine?

A
  • high epithelial turnover
  • normal flora
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11
Q

What organisms are part of the normal GIT flora?

A
  • majority are anaerobes
  • enterobacteriales eg. E. Coli, Proteus etc.
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12
Q

What are the possible sources of GI infection?

A
  • zoonotic (symptomatic animals/asymptomatic shedders) eg. Salmonella
  • human carriers eg. Typhoid
  • environmental sources (contamination of soil and produce) eg. Listeria, E. coli
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13
Q

Describe the different modes of transmission of GI infection

A
  • faecal-oral: any means that an infectious organism from human/animal faeces can gain access to the GIT of another host
  • 3Fs: food (farm to fork/cross contamination), fluid (contaminated water), fingers (importance of hand hygiene
  • person to person: depends on infectious dose and ability to contaminate and persist in environment
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14
Q

Describe the laboratory diagnosis of GI infection

A
  • picking out the infectious pathogen from the normal flora
  • enrichment broth: contains nutrients that promote preferential growth of the pathogen
  • selective media: suppresses growth of background flora while allowing growth of pathogen
  • differential media: distinguishes mixed organisms on the same plate. Uses biochemical characteristics of microorganisms growing in the presence of specific nutrients with a colour indicator
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15
Q

What are important points to note about antibiotic prescribing in GI infections?

A
  • antibiotics are reserved for severe/prolonged symptoms
  • they can prolong symptom duration, exacerbate symptoms, promote resistance and can attribute to harmful infection
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16
Q

What are some ways of controlling GI infections?

A
  • adequate public health measures (provision of safe, clean drinking water; proper sewage disposal)
  • education in food preparation (hand hygiene; avoid cross contamination; cook foods properly)
  • pasteurisation of milk and dairy products
  • sensible travel food practices
17
Q

Describe the microbiology of salmonella

A
  • gram-negative bacilli
  • part of enterobacteriales
  • non-lactose fermenters
  • XLD plates used in labs
18
Q

Describe the transmission of salmonella

A
  • acquired by contaminated food (esp pork, poultry and other meat/dairy products)
  • secondary spread from person to person
  • seasonal peaks in summer and autumn
19
Q

Describe disease features of salmonella

A
  • diarrhoea (due to invasion of epithelial cells in the distal small intestine causing inflammation)
  • bacteraemia
  • distant organs can become seeded (metastasis)
20
Q

Clinical features of salmonella

A
  • incubation 12-72
  • watery diarrhoea
  • vomiting
  • fever (usually associated with more invasive disease)
  • duration 2-7 days
21
Q

What is the treatment for salmonella?

A
  • fluid replacement
  • antibiotics for severe cases + bacteraemia (beta-lactams, quinolones, or aminoglycosides)
22
Q

Describe the microbiology of campylobacter

A
  • curved gram-negative bacilli (sea-gull shaped)
  • microaerophilic + thermopholic
  • culture on campylobacter selective agar
  • C. Jejuni most common
23
Q

Describe the transmission of campylobacter

A
  • large animal reservoir (cattle, poultry, sheep, rodents and birds)
  • infection transmitted via contaminated food, milk or water
  • person to person spread is rare
  • seasonal peaks in May and September
24
Q

Describe the disease features of campylobacter

A
  • inflammation, ulceration and bleeding in small and large bowel due to bacterial invasion
  • bacteraemia
  • post infectious Gullain Barre (ascending paralysis - rare)
25
Q

Describe the clinical features of campylobacter

A
  • incubation 2-5 days
  • bloody diarrhoea
  • cramping abdominal pain
  • usually no vomiting
  • fever
  • 2-10 days
26
Q

What is the treatment of campylobacter?

A
  • fluid replacement
  • clarithromycin/erythromycin in severe/persistent disease
  • quinolone/aminoglycoside in invasive disease
27
Q

How can salmonella be prevented?

A

immunisation of poultry flocks leading to reduction of S. enteritidis

28
Q

How can campylobacter be prevented?

A
  • reduction of contamination in raw, retail poultry meat
  • adequate cooking
29
Q

Describe the microbiology of E. coli

A
  • gram-negative bacilli
  • part of enterobacteriales (important in gut flora in humans and animals, virulence factors enable infection)
  • 6 diarrhoeagenic groups
30
Q

Describe the disease features of Enteropathogenic E. Coli

A
  • initial adherence via pili
  • formation of characteristic attaching and effacing lesion mediated by intimin protein and TiR (translocated intimin receptor)
  • disruption of intestinal microvilli
31
Q

Describe the clinical features of Enteropathogenic E. Coli

A
  • incubation 1-2 days
  • duration 1-several weeks
  • watery diarrhoea with abdo pain and vomiting
  • fever
32
Q

Describe the disease features of enterotoxigenic E. Coli

A
  • diarrhoea due to action of 1/2 plasmid-encoded toxins
  • Heat labile = structural and functional analogue of cholera toxin
  • Heat stable = produced in addition to or instead of LT with similar mode of action
33
Q

What are the clinical features of Enterotoxigenic E. Coli?

A
  • incubation 1-7 days
  • duration 2-6 days
  • watery diarrhoea with abdo pain + vomiting
  • no fever
34
Q

Describe the transmission of enterohaemorrhagic E. Coli

A
  • large animal reservoirs
  • persistent in environment
  • spread through consumption of contaminated food, water, dairy products
  • direct environmental contact with animals
  • secondary person to person spread
35
Q

Describe the disease features of enterohaemorrhagic E. Coli

A
  • attaching and effacing lesions (similar to EPEC)
  • production of shiga-like toxins, structural and functional analogue of shigella dysenteriae toxin
36
Q

Describe the clinical features of enterohaemorrhagic E. Coli

A
  • incubation 1-7 days
  • duration 5-10 days
  • bloody diarrhoea with abdo pain + vomiting
  • no fever
  • haemolytic uraemic syndrome (10% - thrombocytopenia + acute renal failure)
37
Q

What is the treatment of E. Coli infections?

A
  • adequate rehydration
  • no antibiotics or anti-motilities (can increase risk of haemolytic uraemic syndrome in EHEC)

MBChB3 (100 decks)

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