GIT micro

Cards (69)

  • Gastroenteritis
    Characterized by GIT symptoms like nausea, vomiting, diarrhoea and abdominal discomfort
  • Diarrhoea
    Abnormal faecal discharge characterized by frequent and / or liquid stool, usually related to enterotoxin
  • Dysentery
    Inflammatory disorder of the GIT with blood and pus in the faeces, pain, fever, abdominal cramps, usually related to invasive infection with mucosal destruction
  • Damage resulting from GIT infection
    • Action of bacterial toxins, local or distant to site of infection
    • Local inflammation in response to superficial microbial invasion
    • Deep invasion to blood or lymphatics; dissemination to other body sites
    • Perforation of mucosal epithelium after infection, surgery or trauma
    • Gastric ulcers and cancer causing infections
  • Bacterial pathogens of the GIT
    • Salmonella non-Typhi
    • Enteric fever (Typhi & Paratyphi)
    • E.coli
    • Shigella
    • Vibrio cholerae
    • Campylobacter
    • Clostridioides difficile
    • Bacteria causing food poisoning
    • Helicobacter pylori
  • Viral pathogens of the GIT
    • Rotavirus
    • Norovirus
    • Hepatitis A and Hepatitis E
  • Salmonella
    Typhoidal Salmonella cause typhoid & paratyphoid fever (Enteric fever), non-typhoidal Salmonella cause acute but self-limiting diarrhoea
  • Salmonella
    • No animal reservoir for typhoidal Salmonella, large animal reservoirs for non-typhoidal Salmonella
    • Quite large infectious dose required: > 105 organisms
  • Treatment of Salmonella
    1. Diarrhoea is usually self-limiting and resolves without treatment
    2. Fluid and electrolyte replacement
    3. Antibiotics use is discouraged as it does not reduce symptoms/shorten the illness and may prolong excretion of salmonellae in the faeces
  • Enteric fevers: typhoid and paratyphoid

    Systemic infection initiated in the gastrointestinal tract, restricted to humans with no animal reservoir, spread from person to person, usually through contaminated food or water
  • Enteric fever
    • Incubation period: 10–14 days (7–21 days)
    • Fever, malaise, aches, diarrhoea & constipation, rose spots are characteristic but absent in half of the patients
  • Diagnosis of enteric fever

    Stool, blood culture, or culture from another body fluid/tissue
  • Treatment of enteric fever
    Antibiotic treatment with ciprofloxacin or ceftriaxone, cefixime
  • Prevention of enteric fever
    Public health measures, treating carriers, vaccination (injectable Typhim Vi or oral live-attenuated Ty21a)
  • Types of E. coli
    • Enteropathogenic E. coli (EPEC)
    • Enterotoxigenic E. coli (ETEC)
    • Enterohaemorrhagic E. coli (EHEC)
    • Enteroinvasive E. coli (EIEC)
    • Enteroaggregative E. coli (EAEC)
  • E. coli
    • Quite large infectious dose required: > 105 organisms
  • Shigellosis (AKA bacillary dysentery)

    Caused by Shigella species which are human pathogens with no animal reservoir, spread from person to person by the faecal–oral route, primarily a paediatric disease
  • Shigellosis
    • Symptoms range from mild to severe gastroenteritis, diarrhoea is usually watery at first, but later contains mucus and blood, with lower abdominal cramps
    • Invasion of the colonic mucosa causes inflammation & mucosal ulceration, S. dysenteriae produces shiga toxin which can damage the glomerular endothelial cells leading to kidney failure
  • Campylobacter
    Curved or S-shaped Gram-negative rods, microaerophilic and thermophilic, large animal reservoir, acquired by consumption of contaminated food (poultry, milk or water), highly infectious with a dose as low as 500 organisms
  • Campylobacter
    • Causes ulceration & inflamed bleeding mucosal surfaces in jejunum, ileum and colon due to invasion and cytotoxins, can lead to bacteraemia
  • Cholera
    Caused by Vibrio cholerae, a comma-shaped Gram-negative bacterium that is a free-living inhabitant of fresh water, causes infection only in humans with no animal reservoir, can cause epidemics and pandemics
  • Cholera
    • Classified into > 200 serogroups, only O1 and O139 serogroups cause epidemic cholera
    • Causes severe watery non-bloody diarrhoea known as rice water stool, leading to massive fluid loss & electrolyte imbalance, untreated mortality is 40-60%
  • Cholera
    Caused by V. cholerae, a comma-shaped Gram-negative bacterium
  • Cholera symptoms
    • Severe watery non-bloody diarrhoea is known as rice water stool
    • Massive fluid loss & electrolyte imbalance
    • Untreated- mortality is 40-60%
  • Antibiotic-associated diarrhoea
    Caused by Clostridioides difficile, antibiotics disrupt normal gut flora and allows C. difficile to multiply
  • C. difficile exotoxins
    Toxin A (enterotoxin) causes increased intestinal permeability & secretion of fluids, Toxin B (cytotoxin) -colonic inflammation, haemostasis and tissue necrosis in the colon
  • Antibiotic-associated C. difficile diarrhoea
    • Diarrhoea, abdominal pain, fever after antibiotic treatment
  • Staphylococcal Food Poisoning

    • Up to 50% Staph aureus produce enterotoxin, contaminated food, 50% people carry bacteria on skin & nose, heating kills bacteria but toxin is stable
  • Staphylococcal enterotoxin
    Short incubation period: 1-6 hours after consuming contaminated food, presents with vomiting (diarrhea is not a feature), usually self limiting <24 hours
  • Bacillus cereus
    • Spores survive cooking, germinate on cooling, present in soil, food
    Emetic form - rapid onset vomiting within 15min-4hrs due to the ingestion of enterotoxin in food (ingested preformed)
    Diarrhoeal form - watery diarrhoea within 8-12 hrs due to production of enterotoxin in the gut
  • Botulism
    Toxins are ingested in food (often canned food), absorbed from the gut into bloodstream & reaches site of action i.e. peripheral nerve synapses
  • Botulism
    • Characterized by a symmetrical descending flaccid muscle paralysis
  • Clostridium gastroenteritis
    Anaerobic gram-positive spore forming rod produces enterotoxin, spore-contaminated food, inadequately cooked food
  • Clostridium perfringens
    Abdominal pain & diarrhoea – usually self limiting, Necrotizing disease of small bowel, Enterotoxin
  • Helicobacter pylori
    Gram-negative spiral bacterium, Infections are commonly asymptomatic, Symptoms-dyspepsia, upper abdominal pain, nausea, frequent burping, bloating, Associated with gastric & duodenal ulcers, acute & chronic gastritis, gastric adenocarcinoma, mucosa-associated lymphoid tissue (MALT) lymphoma
  • Helicobacter pylori pathophysiology
    Urease breaks urea to ammonia and CO2, Increases pH and provides protection against gastric acid, Flagella
  • Helicobacter pylori treatment
    Multiple treatments with Proton pump inhibitors and antibiotics
  • Norovirus
    • Most common cause of diarrhoea worldwide (20% of all diarrhoea cases), > common in older children and adults, Highly infectious, spread rapidly, Nosocomial infection is common, Food- or water-borne routes, contaminated shellfish such as cockles or mussels, cruise ships outbreaks, aged care homes, barracks
  • Norovirus diarrhoea
    Incubation period: 12–72 h, Nausea, abdominal pain, vomiting and diarrhoea, Recovery usually within 24–48 h
  • Rotavirus
    • Infection is most common in children < 2 years of age, IgA antibodies in colostrum protects during the first 6 months of life, Outbreaks are sometimes seen in nurseries, Older children are less susceptible to infection