Gastrointestinal Disorders Quiz

Gastrointestinal Tract

• The gastrointestinal tract includes the esophagus, stomach, small intestines (duodenum, jejunum, ileum), large intestines (cecum, colon, rectum), and anus.
• The introduction slide notes the key components of the gastrointestinal tract.
• The diagram on slide 3 illustrates the anatomical location of various gastrointestinal organs.
• Stomach inflammation is known as gastritis.
• Inflammation of the stomach and intestines is termed gastroenteritis.
• Enterocolitis is inflammation of both small and large intestines.

Terms

• Diarrhea is an abnormal increase in bowel movements, ranging from loose to liquid stool.
• Dysentery is diarrhea with abdominal cramping pain.
• Proctitis is inflammation of the rectal mucosa, potentially caused by certain bacteria such as N. gonorrhoeae, C. trachomatis, or T. pallidum.

Normal Flora

• Bacteria make up 80% of fecal dry weight.
• Normal flora prevents pathogenic colonization.
• Key bacterial types in the gut flora include anaerobic bacilli (Bacteroides spp.), Gram-negative enteric bacilli, enterococci, streptococci, S. aureus, and yeast (Candida).

Non-Inflammatory Diarrhea

• Caused by bacterial toxins or enterotoxins.
• Results in watery stool with electrolyte fluid loss.
• Patients are not feverish.
• The stool lacks white blood cells, blood, and mucous.

Non-Inflammatory Diarrhea - Causative Agents

• Vibrio cholerae
• Enterotoxigenic E. coli
• Bacteroides spp.
• Viruses (e.g., Giardia, Cyclospora, Cryptosporidium)

Inflammatory Diarrhea

• Organisms invade the intestinal mucosa.
• Cytotoxins destroy intestines cells.
• Patients experience fever and loose, small-volume stools.
• Stool samples contain white blood cells, blood, and mucous.

Inflammatory Diarrhea - Causative Agents

• Salmonella spp.
• Shigella spp.
• Yersinia enterocolitica
• Campylobacter spp.
• Enteroinvasive E. coli
• Clostridium difficile

Enterotoxin-Mediated Diarrhea

• Ingestion of food containing toxins.
• Rapid onset (<12 hours).
• Causative agents include Enterotoxigenic E. coli, Vibrio cholerae, Staphylococcus aureus, Clostridium perfringens, and Bacillus cereus.

Diarrheal Diseases

• Salmonella: gastroenteritis
• Shigella: bacillary dysentery
• Y. enterocolitica: enterocolitis (can mimic appendicitis)
• Campylobacter jejuni and Campylobacter coli: diarrhea
• Edwardsiella tarda: diarrhea (less common)
• Vibrio cholerae: cholera
• Vibrio parahaemolyticus: milder case of cholera
• Plesiomonas shigelloides: diarrhea
• Listeria monocytogenes: gastroenteritis
• Intestinal parasites (e.g., Giardia, Entamoeba, Cryptosporidium, Cyclospora, Microsporidia)
• Viruses (e.g., Rotavirus, Adenovirus, Calicivirus, Astrovirus)

Diseases

• H. pylori: chronic gastritis, peptic and duodenal ulcers
• C. difficile: antibiotic-associated diarrhea, pseudomembranous colitis
• C. perfringens: enterotoxin
• Mycobacterium avium: GI diseases in AIDS patients
• E. coli: enterohemorrhagic (O157:H7), cause of hemorrhagic colitis and hemolytic uremic syndrome (HUS); enteroinvasive; enterotoxigenic, enteropathogenic, enteroaaggregative (traveler's diarrhea); unusually in children

Routes of Transmission

• Primarily fecal-oral route (e.g, consumption of contaminated food/water)
• Direct person-to-person contact
• Animal contact
• Need to survive stomach acidity

Symptoms

• Nausea
• Vomiting
• Abdominal discomfort
• Diarrhea

Specimen Collection

• 2-3 fecal samples in clean, non-sterile, wide-mouth containers.
• Avoid contamination with urine.
• Use Cary-Blair transport medium.
• Process within 1-2 hours of collection.
• Other specimens: duodenal, colostomy, ileostomy material, diapers, food samples (in public health outbreaks)

Visual Examination

• Macroscopic examination (color, consistency).
• Check for blood, mucous.

Microscopic Examination

• Fecal white blood cells (PMN).
• Microbial motility of Campylobacter.
• Gram stain, morphology, and microscopic examination of causative microorganisms.

Stool WBC

• Crucial for distinguishing between inflammatory and non-inflammatory diarrhea.

Culture

• Not practical to culture all isolates.
• Targeted culturing for suspected pathogens, considering patient history and symptoms.
• Special cultures for specific pathogens may be needed on the physician's request.
• Culturing methods vary for different media, including anaerobic or aerobic.

Media Inoculation

• Use non-sterile pipettes or swabs to inoculate media.
• streak the plates to separate organisms for isolation.
• Use enrichment broths for increasing organism concentration.

Media

• BAP/EMB/MAC: media options for isolating various bacteria, depending on the expected causative agent.
• XLD/HE/SS: differential and selective media for specific bacterial identification (e.g., Salmonella, Shigella).
• Campy-BAP: selective media for isolation of Campylobacter.
• TCBS: selective and differential media used for Vibrio.
• CIN: selective media for Yersinia enterocolitica.
• Sorbitol MAC: allows for differentiation between E. coli and E. coli O157:H7.
• CCFA: used to culture Clostridium difficile.

Incubation Conditions

• Ambient air at 35°C for routine cultures
• 42°C (microaerophilic) for Campylobacter.

Workup

• Screening for suspected organisms/pathogens.
• Use biochemical tests.
• Complete identification panels can be used for complete identification.

Reporting Results

• Identification and susceptibility panel.
• Alert public health officials when Salmonella or Shigella is found.
• Reports on overgrowth.
• Report negative results if no Salmonella, Shigella, Vibrio, E. coli O157:H7, or Campylobacter is isolated

Respiratory Tract - Introduction

• Upper Respiratory Tract (URT) infects oral cavity, nose, mouth, throat, epiglottis, and larynx, often containing normal flora.
• Lower Respiratory Tract (LRT) includes trachea, bronchi, bronchioles, and lung alveoli (normally sterile below larynx).

Normal Flora of the URT

• Staphylococcus spp. (including S. aureus)
• Streptococcus spp. (including viridans streptococci and pneumococci)
• Micrococcus spp.
• Diptheroids
• Neisseria spp.
• Haemophilus
• Anaerobes
• Spirochetes
• Candida spp.

URT Infections

• Thrush
• Laryngitis
• Epiglottitis
• Pharyngitis
• Tonsillitis
• Sinusitis
• Otitis media
• Diphtheria
• Pertussis

URT Pathogens

• Viruses (influenza, parainfluenzae, RSV, adenovirus, rhinovirus, coronavirus, coxsackie, EBV, CMV).
• Bacteria (S. pyogenes, B-hemolytic strep group C, F and G, Arcanobacterium haemolyticum, C. diphtheriae, N. gonorrhoeae, Corynebacterium diphtheriae, Bordetella pertussis and parapertussis)
• Yeast

Specimen Collection (URT)

• Specimens: swabs, syringes, biopsies.
• Diphtheria cultured on BAP, Loeffler, tellurite media.
• Pertussis cultured on Bordet-Gengou blood agar.
• Routine collection (posterior pharynx & tonsils): transport media.
• Rapid strep testing.

Microscopic Examination (URT)

• Gram stain is usually not appropriate or diagnostic.
• Many normal flora organisms are present.

Culture (URT)

• Primarily for group A strep.
• Other pathogens (e.g., N. gonorrhoeae, Arcanobacterium haemolyticum, C. diphtheriae) may be cultured upon request or are based on clinical judgment or test results in certain cases.

Throat Culture

• Culture images are included.

Epiglottitis

• Primarily affects children aged 2-6 years.
• Most cases are caused by H. influenzae type b.
• Can be life-threatening due to airway obstruction.
• Rare due to vaccination.
• Epiglottitis should be clinically diagnosed, and specimens collected (blood cultures indicated for bacteremia).

Sinusitis

• Often preceded by a viral URTI.
• S. pneumoniae, H. influenzae, other bacteria (e.g, M. catarrhalis, group A strep, anaerobes, S. aureus, GNR)
• Chronic sinusitis includes similar bacterial pathogens, but S. aureus is more prominent in adults.
• Specimens: via clinical or radiographic diagnosis, collected via sinus aspirate or sinus opening.
• Specimens should be in anaerobic transport media.
• Specimens are cultured aerobically and anaerobically (e.g., using BAP, CHOC, MAC).

Otitis Media

• Middle ear infection common in children under 10.
• Typically follows a viral URTI.
• Pathogens: S. pneumoniae, H. influenzae, other bacteria, and GNR.
• Specimens: Tympanocentesis fluid (TF) aseptically collected and placed in anaerobic transport medium.

Processing TF

• Gram stain and culture, aerobically and anaerobically (using BAP, CHOC, MAC ).
• Identification/susceptibility testing.
• Rupture ear drum fluid should be cultured aerobically.

LRT Infections

• Bronchitis
• Influenza
• Pneumonia
• Empyema (purulent fluid in pleural space)
• Tuberculosis

LRT Pathogens

• Respiratory viruses (influenza A & B)
• S. pneumoniae
• H. influenzae
• M. catarrhalis
• M. pneumoniae
• Chlamydia spp.
• GNR, S. aureus, Legionella spp., anaerobes, mycobacteria , and fungi

Community-Acquired Pneumonia

• S. pneumoniae (most common in adults).
• Mycoplasma pneumoniae (common in young adults).
• H. influenzae (common in children).
• M. catarrhalis.

Hospital-Acquired Pneumonia

• Enterobacteriaceae, K. pneumoniae, S. marcescens, S. aureus, NFGNR, P. aeruginosa, Burkholderia cepacia, nosocomial S. pneumoniae, and anaerobic bacteria.

Miscellaneous Causative Agents

• Mycobacteria (tuberculosis)
• Legionella spp.
• Chlamydia C. trachomatis, C. pneumoniae, mostly in immunocompromised patients.

Emerging Viral Infections of the Respiratory Tract

• Avian influenza (H5N1)
• H1N1 influenza A
• Severe Acute Respiratory Syndrome (SARS) coronavirus

Bioterrorism Agents

• B. anthracis (anthrax)
• Y. pestis (plague)
• Coxiella burnetii (Q fever)
• F. tularensis (tularemia)

Routes of Infection

• Primarily opportunistic pathogens, waiting for the host's defenses to weaken.
• Transmission via inhaled aerosols, hematogenously (bloodstream), or aspiration of oral/gastric contents.

Specimen Collection (Respiratory Tract)

• Sputum (expectorated or induced).
• Washing.
• Brushing.
• Biopsy.
• Pleural fluid aspirate.
• Specimens should be placed in sterile screw-cap tubes or bottles.
• Specimens must be cultured within 2 hours.

Sputum Gram Stain Analysis

• Low power field (LPF) evaluation (10x):
• Number of epithelial and PMNs.
• High power field (HPF) evaluation (100x):
• Microbial organisms quantity (rare, moderate, many) & type
• Helps to determine if the sample is adequate for culture.

Routine Cultures (Respiratory Tract)

• BAP, CHOC, MAC (35°C in CO2).
• Cystic fibrosis patients may require specialized media (e.g., for B. cepacia, MRSA,and Pseudomonas)
• Anaerobic cultures for specific samples (e.g, lung biopsies, pleural fluids).

Test your knowledge on gastrointestinal disorders with this quiz. You will explore symptoms, associated organisms, and the roles of normal flora. Challenge yourself and deepen your understanding of gastrointestinal health.