Gastrointestinal Infections

• What is the definition of gastrointestinal tract infection?

  Infection characterized by gastroenteritis, diarrhea, and/or vomiting
• What are the typical bacterial pathogens associated with gastrointestinal infections?

  Campylobacter, Salmonella, Shigella, E. coli pathotypes
• How does stomach acid contribute to host defence mechanisms?

  It destroys over 99.9% of ingested Enterobacteriaceae within 30 minutes
• Why are patients with achlorhydria or those taking antacids more vulnerable to infections?

  They have reduced stomach acid, which decreases pathogen destruction
• What role do bile salts play in host defence mechanisms?

  Bile salts disrupt some bacterial cell surfaces but enteric organisms can survive
• What are the mucosal defences in the gastrointestinal tract?

  IgA, phagocytes, and digestive enzymes create a hostile environment
• How does gut motility contribute to host defence?

  Peristalsis impedes attachment and helps clear pathogens
• What is the role of commensal flora in the gastrointestinal tract?

  It confers colonization resistance and competes with pathogens
• What is the estimated number of cases of gastrointestinal infections in England per year?

  Approximately 9.5 million cases
• What is the typical duration for recovery from gastrointestinal infections?

  Infections generally resolve over a few days and are self-limiting
• What factors contribute to more severe gastrointestinal infections in developing countries?

  Poor sanitation and limited access to clean water
• What is acute gastroenteritis caused by?

  Ingestion of food contaminated by bacteria or bacterial toxins
• What are the common sources of infection for gastroenteritis?

  Contaminated food or water, recreational contact, and direct contact with animals
• What is the usual incubation period for Salmonella spp. (excluding enteric fever)?

  12 hours to 3 days
• Which bacterial pathogens are typically associated with food-borne illness in the UK?

  Escherichia coli, Campylobacter, Salmonella, Clostridium perfringens
• What is the main clinical feature of Shigella spp. infections?

  Severe diarrhea with blood and mucus in the feces
• What is the incubation period for Campylobacter infections?

  1. 5 days
• What is the significance of the Gram stain in stool sample analysis?

  Gram stain of stool sample is of no value for diagnosis
• What is the role of selective/differential media in pathogen recovery?

  It helps isolate specific pathogens from stool samples
• What are the symptoms associated with diarrhea?

  Loose, watery, unformed feces, abdominal pain, cramps, nausea, malaise, vomiting, fever, dehydration
• How is dysentery characterized?

  Severe diarrhea with blood and mucus in the feces
• What type of agar is used for the cultivation of lactose fermenters?

  MacConkey agar
• What is the incubation temperature for Campylobacter species?

  37-43 °C
• What is the characteristic appearance of Campylobacter colonies on culture media?

  Grey, moist, metallic sheen
• What is the significance of the 'gull wing' appearance in Gram staining?

  It is a confirmatory feature for Campylobacter species
• What is the primary species of Salmonella associated with infections?

  Salmonella enterica
• How many serotypes are there within the Salmonella enterica species?

  Many serotypes exist within the species
• What are the key components of host defence mechanisms in the gastrointestinal tract?

  • Stomach acid (pH < 4)
  • Bile salts
  • Mucosal defences (IgA, phagocytes, digestive enzymes)
  • Gut motility (peristalsis)
  • Commensal flora
• What are the common clinical features of Campylobacter infections?

  • Incubation: 2-5 days
  • Symptoms: Severe diarrhea, fever, abdominal pain
  • Duration: 2-7 days
  • Possible complications: Arthritis, Guillain-Barré Syndrome
• What are the main bacterial pathogens associated with gastrointestinal infections in the UK?

  • Escherichia coli
  • Campylobacter species
  • Salmonella enterica
  • Clostridium perfringens
• What are the typical sources of gastrointestinal infections?

  • Contaminated food or water
  • Recreational contact with contaminated water
  • Direct contact with infected animals
• What are the methods for recovering pathogens from stool culture?

  • Use of selective/differential media
  • Microscopy and immunofluorescence
  • Inoculation and culture techniques
• What are the symptoms of diarrhea and dysentery?

  Diarrhea:

  • Loose, watery feces
  • Abdominal pain, cramps, nausea, malaise, vomiting, fever, dehydration

  
  

  Dysentery:

  • Severe diarrhea with blood and mucus
  • Abdominal cramps and constitutional disturbance
• What are the characteristics of the main bacterial pathogens causing gastrointestinal infections?

  • Campylobacter: S-shaped cells, thermophilic
  • Salmonella: Multiple serotypes, enterica species
  • Shigella: Severe diarrhea, blood in feces
  • Clostridium: Associated with antibiotic therapy
• What are the types of agars used for cultivating GIT pathogens?

  • MacConkey agar for lactose fermenters
  • XLD agar for Salmonella and Shigella
  • CCDA for Campylobacter
• When do levels of Campylobacter infections peak?

  Between May and September
• What is the commonest cause of gastroenteritis in the developed world, particularly in the UK?

  Campylobacter
• What are common sources of Campylobacter infections?

  BBQs, undercooked chicken, and cross-contaminated foods
• Is Campylobacter normally transmitted person-to-person?

  No, it is not normally person-to-person transmission
• What percentage of Campylobacter cases are caused by C. jejuni?

  90%