97 - Gastrointestinal Infections Flashcards
Reasons why diarrhoea kills
1
2
1) Immediate: fluid and electrolyte imbalance
2) Delayed: malnutrition
Reasons why diarrhoea kills
1) Immediate: fluid and electrolyte imbalance
2) Delayed: malnutrition
Fluid moving through GIT in 24 hours
~10L
Amount of fluid absorbed per day through GIT
~9.9L of 10L taken in (excrete ~100mL)
Two ways in which diarrhoea can come about
1
2
1) Small intestine origin - Too much fluid for intestine to absorb.
2) Diarrhoea of large intestinal origin - Large intestine becomes inflamed, stops retaining gut contents (can’t operate properly)
What characterises diarrhoea of small intestine origin
More volume, watery, frequent
What characterises diarrhoea of large intestine origin
Less volume, can be bloody or purulent
Dysentery
Presence of blood, pus, mucus in the faeces
Predominant aetiological agents of infective diarrhoea in developed vs developing countries
More bacteria in developing countries, more viral in developed countries
Aetiological agents of non-specific gastro
Bacteria, viruses, protozoa
Aetiological agents of dysentaery
Shigella/EIEC, protozoa
Typical protozoal cause of dysentary
Entamoeba histolytica
Aetiological agents of foodborne infections/intoxications
Salmonella, Virbio, Listeria, Yersinia, Campylobacter, EHEC, Staph, Clostridium, Bacillus, ciguatoxin, viruses.
Aetiological agents of foodborne infections/intoxications
Salmonella, Virbio, Listeria, Yersinia, Campylobacter, EHEC, Staph, Clostridium, Bacillus cereus, ciguatoxin, viruses.
Where is ciguatoxin found?
Some species of fish
Aetiological agents of travellers’ diarrhoea
ETEC, viruses, protozoa
Most common cause of travellers’ diarrhoea
ETEC (~50% of cases)
Aetiological agent of pseudomembranous colitis
Clostridium difficile
Most serious cause of antibiotic diarrhoea
Clostridium difficile
Aetiological agent of haemorrhagic colitis
EHEC
Most severe Shigella species
Shigella dysenteriae
Only infectious cause of haemolytic uremic syndrome
Shigatoxin (EHEC or S. dysentariae)
Only infectious cause of haemolytic uremic syndrome
Shigatoxin (EHEC or S. dysentariae)
Only Shigella species that releases shigatoxin
S. dysenteriae
Difference between dysentery and haemorrhagic colitis
Dysentery has blood, pus, mucus in faeces.
Haemorrhagic colitis only has blood
Aetiological agents of cholera-like diarrhoea
Vibrio cholerae, ETEC
Only serotypes of V cholerae that cause epidemic cholera
O1 and O139
Aetiological causes of enteric fever
Salmonella typhi, Salmonella paratyphi
Aetiological causes of enteric fever
Salmonella enterica serotype Typhi, Salmonella enterica serotype Paratyphi
Aetiological causes of enteric fever
Salmonella enterica serotype Typhi, Salmonella enterica serotype Paratyphi
ETEC virulence factors
CFA adhesin, enterotoxin
EPEC virulence factors
Intimin and bfp adhesins, type III secretion system effectors
EHEC virulence factors
Intimin and Efa adhesins, shigatoxins
EIEC virulence factors
IpaC adhesin, ShET toxin
Same as Shigella (as they are pretty much Shigella)
Symptoms of ETEC
Watery diarrhoea
Epidemiology of ETEC
Infants in LDCs, travellers
Symptoms of EPEC
Non-specific gastro
Epidemiology of EPEC
Children in LDCs
Symptoms of EIEC
Dysentery
Epidemiology of EIEC
Any age, mainly in LDCs
EHEC symptoms
Bloody diarrhoea
EHEC epidemiology
Any age, developed countries
EAEC symptoms
Watery diarrhoea
Adhesive enterotoxigenic bacteria
ETEC
Bacteria that are adhesive with brush border damage
Cholera, EPEC
Enterobacteria that invade, restricted to mucosa
Shigella
Enterobacteria that invade submucosa
Salmonella, Campylobacter
Enterobacteria that invade systemically
Salmonella
Enterobacteria that invade systemically
Salmonella
What do ETEC adhere to?
Microvili
Lesions caused by EPEC
Attaching-effacing lesions
How do EPEC adhere to gut wall?
1
2
Stage 1 (plasmid mediated) - Bundle-forming pili attach to intact microvili Step 2 (chromosomal) - Late adherence, forming attaching, effacing lesions
Only Shigella species that releases shigatoxin
S. dysenteriae type 1
Pathogenicity island
Collection of genes that are found in a pathogen, that are involved in pathogenesis. Are chromosomally-encoded
ETEC toxins
LT and ST
Enteric Yersinia species
Yersinia enterocolitica, Yersinia pseudotuberculosis.
Use Invasin to invade cells.
Can LPS be neutralised by antibodies?
No, because LPS acts as an enterotoxin by being recognised by the innate immune system, which still happens if LPS is bound by antibodies.
