Resident Microbial Flora in Infants
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Resident Microbial Flora in Infants

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Questions and Answers

What type of bacteria are predominant in the adult large bowel (colon)?

  • Gram-positive organisms
  • Anaerobes (correct)
  • Gram-negative organisms
  • Aerobes

    • What is the ratio of anaerobes to aerobes in the large bowel (colon)?

  • 100:1
  • 10000:1
  • 10:1
  • 1000:1 (correct)

    • What is the approximate number of bacteria present in 1 gram of stool from a healthy human?

  • 10^13-10^14 CFU/g
  • 10^11-10^12 CFU/g (correct)
  • 10^6-10^8 CFU/g
  • 10^9-10^11 CFU/g

    • What is the term for the inflammation of the stomach and the intestines?

    <p>Gastroenteritis</p> Signup and view all the answers

    What is the term for an abnormal increase in the number and frequency of bowel movements?

    <p>Diarrhea</p> Signup and view all the answers

    What is the term for an inflammatory disorder of the GI tract often associated with blood and pus in the faeces?

    <p>Dysentery</p> Signup and view all the answers

    What is the term for the inflammation of the mucosa of small and large intestines?

    <p>Enterocolitis</p> Signup and view all the answers

    What type of bacteria are typically present in infants within hours of birth?

    <p>Normal human epithelial flora</p> Signup and view all the answers

    What is proctitis?

    <p>Inflammation of the rectal mucosa</p> Signup and view all the answers

    What is food-associated infection (FAI) usually caused by?

    <p>Toxins produced by the organisms</p> Signup and view all the answers

    Which bacteria causes bacillary dysentery?

    <p>Shigella spp.</p> Signup and view all the answers

    What is the most important enterohemorrhagic E. coli strain?

    <p>O157:H7</p> Signup and view all the answers

    Which bacteria causes acute gastroduodenal ulcers?

    <p>Helicobacter pylori</p> Signup and view all the answers

    What is the most common cause of antibiotic-associated diarrhea?

    <p>Clostridium difficile</p> Signup and view all the answers

    Which bacteria causes food poisoning?

    <p>Bacillus cereus</p> Signup and view all the answers

    Which bacteria can cause diarrhea by overgrowing the intestinal flora in patients treated with antibiotics?

    <p>Pseudomonas aeruginosa</p> Signup and view all the answers

    What is the recommended time frame for transporting stool samples to the lab for viral culture?

    <p>Within 2 hours at room temperature</p> Signup and view all the answers

    What is the purpose of adding sodium bicarbonate to gastric aspirate specimens?

    <p>To neutralize the specimen within 1 hour of collection</p> Signup and view all the answers

    What type of agar is used for selective culture of Campylobacter?

    <p>Selective Campylobacter agar (Campy)</p> Signup and view all the answers

    What is the recommended method for transporting rectal swabs for viral recovery?

    <p>In modified Stuart's medium or another viral transport medium</p> Signup and view all the answers

    Why are gastric aspirate specimens mostly taken from infants?

    <p>For AFB detection</p> Signup and view all the answers

    What is not suitable for the detection of parasites, toxins, or viral antigens?

    <p>Swabs are not acceptable for the detection</p> Signup and view all the answers

    Which of the following parasites is known to attach to intestinal cells by suckers?

    <p>Giardia lamblia</p> Signup and view all the answers

    What is the primary effect of aflatoxins on the human body?

    <p>Carcinogenesis</p> Signup and view all the answers

    Which of the following fungal toxins is primarily produced by Amanita mushrooms?

    <p>Mushroom toxins</p> Signup and view all the answers

    What is the primary advantage of invasion for microorganisms?

    <p>Both A and B</p> Signup and view all the answers

    Which of the following microorganisms causes minimal invasion?

    <p>Norwalk virus</p> Signup and view all the answers

    Which of the following routes of infection involves the transmission of bacterial toxins through contaminated food or water?

    <p>Ingestion of bacterial toxin-contaminated food or water</p> Signup and view all the answers

    What is the primary characteristic of inflammatory diarrhea?

    <p>Fever and loose stools</p> Signup and view all the answers

    Which of the following microorganisms causes a severe invasion of the intestine?

    <p>Entamoeba histolytica</p> Signup and view all the answers

    What type of media is used to detect S.aureus or yeast outgrowth?

    <p>BAP</p> Signup and view all the answers

    What type of medium is used to isolate Campylobacter jejuni subspecies?

    <p>Campylobacter Selective Media</p> Signup and view all the answers

    What type of examination can help visualize the darting motility of campylobacter spp.?

    <p>Unstained saline preps</p> Signup and view all the answers

    What is the purpose of enrichment broth in culturing fecal specimens?

    <p>To enrich for Salmonella and Shigella</p> Signup and view all the answers

    What is the incubation condition for Campylobacter selective media?

    <p>Microaerobic conditions at 42°C</p> Signup and view all the answers

    What type of media is used to isolate Yersinia entercolitica?

    <p>Cefsulodin-irgasan-novobiocin (CIN) agar</p> Signup and view all the answers

    What is the purpose of Sorbitol MacConkey (SMAC) agar?

    <p>To isolate E.coli O157:H7</p> Signup and view all the answers

    What type of examination is used to check for the presence of blood and mucus in a specimen?

    <p>Macroscopic examination</p> Signup and view all the answers

    Study Notes

    Resident Microbial Flora

    • Infants are colonized by normal human epithelial flora, including Staphylococcus, Corynebacterium spp., and other gram-positive organisms, within a few hours of birth.
    • The normal flora of the adult large bowel (colon) is established relatively early in life and consists predominantly of anaerobic species, including Bacteroides, Clostridium, Peptotreptococcus, Bifidobacterium, and Eubactrium.
    • Aerobes, including E. coli, other Enterobacteriaceae, Enterococci, and streptococci, are outnumbered by anaerobes (1000:1).
    • The number of bacteria/gram of stool within the bowel lumen increases steadily as material approaches the sigmoid colon.
    • 80% of the dry weight of feces from healthy humans consists of bacteria, which can be present in numbers as high as 10^11-10^12 CFU/g of stool.

    Terms to Know

    • Gastritis: inflammation of the stomach
    • Gastroenteritis: inflammation of the stomach and intestines, characterized by GI symptoms including nausea, vomiting, diarrhea, and abdominal discomfort
    • Enterocolitis: inflammation of the mucosa of small and large intestines
    • Diarrhea: abnormal increase in the number and frequency of bowel movements, with fecal material often having a loose to liquid consistency
    • Dysentery: inflammatory disorder of the GI tract, often associated with blood and pus in the feces, and accompanied by pain, fever, and abdominal cramps
    • Proctitis: inflammation of the rectal mucosa
    • Food-Associated Infection (FAI): usually caused by toxins produced by organisms, rather than the direct actions of the organism itself

    Diseases

    • Causative agents: bacteria, viruses, and parasites
    • Bacterial infections:
      • Salmonella spp.: common cause of gastroenteritis
      • Shigella spp.: cause bacillary dysentery and common cause of diarrhea
      • Campylobacter spp.: frequently cause diarrhea in the US
      • E. coli: pathogenic E. coli may be enterohemorrhagic, enteroinvasive, enterotoxigenic, or enteropathogenic
      • Yersinia enterocolitica: causes enterocolitis, some infections resemble acute appendicitis
      • Edwardsiella tarda: relatively uncommon cause of diarrhea
      • Vibrio: V. cholerae causes cholera, V. parahaemolyticus causes watery diarrhea
      • Helicobacter pylori: causes chronic gastritis and the most common cause of peptic and duodenal ulcers
      • Clostridium: C. difficile is an important cause of antibiotic-associated diarrhea and pseudomembranous colitis, C. perfringens produces enterotoxin and is a common cause of food-poisoning
      • Staphylococcus aureus: can cause GI disease in two different ways, including Staph. food poisoning and staphylococcal overgrowth
      • Pseudomonas aeruginosa: can cause diarrhea by overgrowing the intestinal flora in patients treated with antibiotics
      • Bacillus cereus: causes food poisoning

    Adherence to Intestinal Cells

    • Cryptosporidiosis (Cryptosporidium parvum) and Isospora spp.: disrupt mucosal function, seen in diarrhea of patients with AIDS and in travelers' diarrhea
    • Helminths: Flukes, tapeworms (cestodes), and roundworms (nematodes)
    • Protozoans: Giardiasis (Giardia lamblia) attaches by suckers, no invasion or toxin production

    Fungal Toxins

    • Ergot (rye, wheat): can cause hallucinations, can be medicinal
    • Aflatoxins (moldy grain, peanuts): strong carcinogens
    • Mushroom toxins: mainly produced by Amanita, toxic to liver

    Invasion

    • Invasion allows the microorganism to reach deeper tissues, access nutrients for growth, and possibly avoid host immune response
    • Minimal invasion: Norwalk virus, Rotavirus
    • Variable invasion: Aeromonas sp., Campylobacter sp., Salmonella sp., Vibrio parahemolyticus
    • Severe invasion: Entamoeba histolytica, enteroinvasive E. coli, Shigella species

    Routes of Infection

    • Transmission through fecal-oral route
    • Ingestion of bacterial toxin-contaminated food or water
    • Direct person-to-person contact
    • Through animal contact

    Symptoms

    • Nausea, vomiting, abdominal discomfort, and diarrhea

    Diagnostic Procedures

    • Visual Examination: macroscopic examination for presence of blood and mucus, microscopic examination for presence of blood, PMNs, bacteria in gram-stained smears
    • Cultures: most labs routinely culture fecal specimens for Salmonella, Shigella, Campylobacter, and E. coli O157:H7
    • Media used: BAP, MacConkey agar, XLD agar, Campylobacter Selective Media, Enrichment broth, CIN agar, SS agar, SMAC agar
    • Incubation conditions: ambient air at 35°C, microaerobic conditions for Campylobacter spp.

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    Description

    Learn about the normal human epithelial flora that colonize infants, including Staphylococcus and other gram-positive organisms, and how the content of intestinal flora changes over time.

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