NORMAL MICROBIAL FLORA OF GIT

1. NORMAL MICROBIAL FLORA OF GIT Assistant Professor Microbiology College of Medicine Majmaah University

2. OBJECTIVES OF LECTURE • Identify Normal Microbial Flora of GIT • Discuss Beneficial Role & Disease causing ability of Normal Flora of GIT • Discuss use of Antimicrobials & their influence on normal microbial flora of GIT

3. NORMAL MICROBIAL FLORA OF GIT A 26-years-young man underwent tooth extraction of first molar tooth right lower jaw from a dentist due to dental caries. Ten days later, he noticed pain and swelling right lower jaw and two days later pus discharge from lower jaw right side was noticed. Culture of the pus yielded growth of Actinomyceseisraeli that was sensitive to Penicillin. There is no risk of spread of this infection to other people because • The organism isolated is not very pathogenic • The infection arose as a result of implantation of endogenous mouth flora into wound of tooth extraction • The transmission of this organism is difficult as nobody else has tooth extraction • This organism is not a pathogen of systems outside oral cavity

4. NORMAL MICROBIAL FLORA OF GIT • GIT, Digestive system and Alimentary canal • GIT consist of oral cavity, esophagus, stomach, small and large intestine, rectum and anal canal

5. NORMAL MICROBIAL FLORA OF GIT • ORAL CAVITY • Sterile at birth • 4-12 hrs-Colonize by viridansStreptococci (Main bacteria) • Aerobic & Anaerobic Staphylococci • Gram Negative diplococci (Neisseria, Moraxella) • Diphtheriods, Lactobacilli • Adult- Anaerobic Spirochaetes, Prevotellaspp, • Actinomycese • Yeast (Candida)

6. NORMAL MICROBIAL FLORA OF GIT A 19-years-young man underwent dental treatment at a clinic. Four weeks later, patient reported with low grade fever, myalgias and fatigue. His temp is 100.2o C, spleen is palpable and systolic cardiac murmur is heard in precordium. Suspecting infective endocarditis, blood cultures were taken. Which organism is most likely to be isolated? • Salmonella typhi • Shigelladysentriae • Mycobacterium tuberculosis • Viridans streptococcus • Vibriocholerae

7. NORMAL MICROBIAL FLORA OF GIT • Esophagus • Bacteria from food • Transient and not permanent • Stomach • Acidity keeps bacterial growth low • 103 to 105 • ↓ pH prevents pathogens to cause disease • Antacids, PPI (Omeprazole etc) ↓ resistance

8. NORMAL MICROBIAL FLORA OF GIT • Muhammad is a known case of peptic ulcer and is taking omeprazole. He went out for dinner with his five friends. All of them drank unhygienic water from a local shop. Next day, Muhammad developed profuse diarrhea and vomiting and he was hospitalized. He was diagnosed as a case of cholera. Apart from Muhammad, none of his friend acquired the disease because • Muhammad has some immune deficiency • All his friends were healthy • Muhammad has peptic ulcer disease • PPI(omeprazole) ↓ acid in stomach and so less pathogens can cause disease • Vibriocholeraeis normal intestinal flora

9. NORMAL MICROBIAL FLORA OF GIT • Intestine • Duodenum, jejunum and upper ileum- Enterococci and lactobacilli • Lower ileum, ceacum and large intestine- Fecal flora • Approx 96-99% fecal flora are Anaerobes • Bacteroidesfragilis, Fusobacteriumspp, Clostridiumspp (C perferingens), Anaerobic lactobacilli, Anaerobic streptococci (Peptostreptococci) • 1-4% are Coliform (e.g. E. coli, Klebsiella), Enterococci, Pseudomonas • Candida in 10% population • Minor trauma e.g. sigmoidoscopy, enema etc-bacteremia in 10%

10. Beneficial Role & Disease causing ability of Normal Flora • Beneficial Role • Protective function • Indirect :- Physically covering the receptors for pathogens and competing for nutrition • Direct:- Production of antimicrobial factors e.g. bacteriocins, lactic acid etc • Development of local immune system • Induce secretion of IgA, modulate local T cells • Metabolic function • Vit K, Biotin, folate • Metabolize dietary carcinogens • Assist fermentation of non digestible food residue

11. Beneficial Role & Disease causing ability of Normal Flora • Disease causing ability • Microbes of normal flora are harmless at site • Outside these anatomical barriers, cause disease • These flora cause disease by • Breach in the anatomical barriers (By procedures like sigmoidoscopy, urinary catherization, dental procedures etc) • Suppression by antimicrobials with selecting out of drug resistant org

12. Antimicrobials effect on Normal Flora • Broad spectrum antimicrobials-suppress gut flora • Those microorgansism resistant to the drug-select out and proliferate • Clostridium difficileenterocolitis • This org overgrows, release toxin and causes ulceration and necrosis • Metronidazole or Vancomycin for treatment

13. MCQ • A 24-years-young man met a RTA. He sustained multiple injuries and was hospitalized. At laparotomy, it was found that there was a laceration in ascending colon 50 cm from caecum. The laceration was stitched but three days later, he experienced pain right side of abdomen and fever. USG revealed pus collection near stitched laceration of ascending colon. The most likely organisms to be isolated will be • Vibrio choleraeand Staph aureus • Strep pyogenes • Mycobacterium tuberculosis • Mixed normal gastrointestinal flora • Neisseriameningitidis

14. MCQ • Ahmed was admitted to the hospital due to lobar pneumonia affecting right lower lobe. He was prescribed Co-amoxiclav (Augmentin) 1 gm BD. At4th day post admission, Ahmed experienced diarrhea with blood and mucus and pain abdomen. There was distention of abdomen. Which of the following organisms is likely to overgrow and release toxin as a result of co-amoxiclav induced suppression of gut micro-flora? • Enterococcusspp • Staphylococcus epidermitidis • Pseudomonas aeruginosa • Candida albican • Clostridium difficile