Lecture 5 Gastrointestinal Infections Flashcards
What is gastroenteritis? Name some of its generic symptoms.
Infection of the GIT; can be parasitic, viral, or bacterial. Mostly self-limiting.
Generic symptoms: cramps, vomiting, diarrhoea
What is diarrhoea?
Diarrhoea is a change in bowel habit, characterised by increased stool frequency and/or increased fluidity.
Define the categorical thresholds of diarrhoea.
Acute: 3 <= x < 14
Persistent: 14 <= x < 30
Chronic: x>=30
What are the common causes of diarrhoea?
Secretory: bacterial endotoxins disrupt regulation of water movement in intestinal cells
Osmotic: too sweet or too salty ingestions that cause water to be drawn into GIT from intestinal cells
Inflammatory/Exudative: blood/WBC, mucosal damage
What are some risk factors that increase the potential of diarrhoea?
Increased immigration and travel: greater exposure to bacteria, often novel bacteria that the body is not immune to. Bringing in bacteria from 3rd world countries with poor sanitation
Human - animal transmission: increased meat consumption growing industry more likely for transmission
Aqua culture: globalisation of food production
Changing food consumption habits
Greater proportion of immunocompromised individuals in the population: more elderly, more sick patients kept alive due to medical advancements.
Appreciate the differences between bacterial infection and bacterial intoxication.
Bacterial infection: ingestion of bacteria. Grows and establish in GIT but may not necessarily cause adverse symptoms
Bacterial intoxication: ingestion of toxin
Define the differences between endotoxin and exotoxin.
Exotoxin: pathogenic bacteria make proteins that can diffuse out of the bacteria. Both G+ and G- bacteria. Heat labile.
Endotoxin: lipid portions of LPS that are part of the cell wall of G-, only is released when their cell lysis. Heat stable.
What is Salmonella (non-typhoidal)?
Transmission: animals, food, faecal-oral
Symptoms (mostly self-limiting): diarrhoea, nausea, headache, cramps
Incubation period: 6-72hrs
What is Salmonella (typhoid)
S. type causes enteric fever. Bacteria invades intestinal epithelium via Peyer’s patches.
Transmission: food, faecal-oral
Symptoms: fever vomiting, ‘rose spots’ rash
Prevention: vaccination 2 weeks before travel
Treatment: antibiotics ceftriaxone, azithromycin
Complications: dissemination to lungs, gallbladder, CNS.
What is Clostridium difficile infection?
Clostridium difficile produces spores (resistant to disinfectants and desiccation)
Transmission: ingestion of spores via food, faecal-oral
Increased risk: antibiotic overuse (reduces normal flora)
Treatment: vancomycin, faecal transplant
What is Listeria monocytogenes infection?
Transmission: food with high numbers of bacteria
Spread within host: via macrophages to other host cells
Incubation period: 3 weeks
Complications: very invasive, can lead to septicaemia, meningitis
Treatment: ampicillin + gentamicin
What is Norovirus?
Extremely contagious!
Transmission: person-person, airborne, food, touching contaminated surfaces
Symptoms: vomiting, watery diarrhoea
Incubation period: 18-48hrs
Prevention: hand hygiene, clean surfaces, isolate sick patients, no vaccine
Treatment: no specific treatment can only do supportive therapy like fluid replacement
