Gastrointestinal Disorders Quiz

Gastrointestinal Tract

• The gastrointestinal tract includes the esophagus, stomach, small intestines (duodenum, jejunum, ileum), large intestines (cecum, colon, rectum), and anus.
• Inflammation of the stomach is called gastritis.
• Inflammation of the stomach and intestines is called gastroenteritis.
• Inflammation of the small and large intestines is called enterocolitis.
• An abnormal increase in bowel movements, from loose to liquid stool is called diarrhea.
• Diarrhea with cramping abdominal pain is called dysentery.
• Inflammation of the rectal mucosa is called proctitis.
• 80% of the dry weight of feces is bacteria.
• Normal flora prevents colonization of pathogens.
• Common bacteria in normal flora include anaerobic bacilli (Bacteroides spp.), GN enteric bacilli, and Enterococci, Streptococci, and Staphylococcus aureus.
• Yeast (Candida) is also present in normal flora.
• Non-inflammatory diarrhea is caused by bacterial toxins (enterotoxins).
• Symptoms include watery, large-volume stool, and no visible PMN, blood, or mucous.
• Common causes include Vibrio cholerae and Enterotoxigenic E. coli.
• Viral infections can also cause non-inflammatory diarrhea.
• Examples include Giardia lamblia, Cyclospora, and Cryptosporidium.
• Inflammatory diarrhea is caused by organisms invading the intestinal mucosa.
• Cytotoxins destroy intestinal cells.
• Symptoms include fever, loose, small-volume stool, and fecal specimens containing PMN, blood, or mucous.
• Common causes include Salmonella spp., Shigella spp., Yersinia enterocolitica, Campylobacter spp., Enteroinvasive E. coli, and Clostridium difficile.
• There are also enterotoxin-mediated diarrheas.
• Causes include ingestion of food containing toxin, rapid onset (less than 12 hours).
• Common culprits include Enterotoxigenic E. coli, V. cholera, S. aureus, C. perfringens, and B. cereus.
• The diseases associated with diarrhea include Salmonella, Shigella, Yersinia enterocolitica, and Campylobacter jejuni.
• Other diseases such as Edwardsiella tarda, Vibrio cholerae, V. parahaemolyticus, Plesiomonas shigelloides, and Listeria monocytogenes are also associated with diarrhea.
• Other diarrheal diseases involve intestinal parasites, such as Giardia, Entamoeba, Cryptosporidium, Cyclospora, and Microsporidia.
• Diseases like H. pylori cause chronic gastritis and peptic/duodenal ulcers.
• C. difficile is associated with antibiotic-associated diarrhea and pseudomembranous colitis.
• C. perfringens is linked with enterotoxin.
• Mycobacterium avium is associated with GI diseases in AIDS patients,
• Diseases associated with E. coli include enterohemorrhagic E. coli (O157:H7), and enteroinvasive E. coli.

Routes of Transmission

• Most infections follow the fecal-oral route.
• Certain organisms or toxins (as in S. aureus) are ingested from contaminated water or food.
• Other routes include direct contact (like Shigella) or contact with animals (Y. enterocolitica).
• Some pathogens need to survive the stomach's acidic environment.

Symptoms

• Common gastrointestinal symptoms include nausea, vomiting, abdominal discomfort, and diarrhea.

Specimen Collection

• For the gastrointestinal tract, collect 2-3 fecal specimens in clean, non-sterile, wide-mouth containers.
• Do not contaminate with urine.
• Use transport medium like Cary-Blair medium.
• Process within 1-2 hours of collection.
• Other specimens can include duodenal, colostomy, or ileostomy material, and diapers.
• Collecting food samples may be necessary (for public health investigations)

Visual Examination

• Macroscopic examination includes checking for blood, mucous, consistency (watery, formed, loose), and color.

Microscopic Examination

• Inspect fecal specimens for WBC (PMN).
• Use methylene blue for a wet mount.
• Check for motility in Campylobacter.
• Perform Gram staining for morphology.
• Look for curved GNR (Vibrio) or GPR (Clostridium).

Stool WBC

• Differentiate inflammatory from non-inflammatory diarrhea based on WBC presence.

Culture

• General culture is not practical for all isolates.
• Look for specific agents like Salmonella, Shigella, Campylobacter, E. coli O157:H7, and Vibrio.
• Consider patient history and symptoms.
• Rely on physician for special culture requests.

Media Inoculation

• Use non-sterile pipettes or swabs for inoculating culture media.
• Streak plates for isolation.
• Use enrichment broth containing large amounts of specimen.

Media

• BAP (Blood Agar Plate) is used to identify S. aureus and yeast.
• MAC (MacConkey Agar) or EMB (Eosin Methylene Blue Agar) is a differential and selective medium.
• NLF (Non-lactose fermenting) media is used to isolate non-lactose fermenters.
• XLD (Xylose-lysine-desoxycholate) or HE (Hektoen Enteric) or SS agar is used for Salmonella and Shigella.
• Campy-BAP is a selective medium used in the isolation of Campylobacter species.
• Enrichment broth (GN) is helpful for Salmonella and Shigella.
• Selenite F is a selective agent for Salmonella and some Shigella species.
• Special media for Y. enterocolitica include CIN (Cefsulodin-irgasan-novobiocin) agar and SS agar (Salmonella-Shigella).
• TCBS (Thiosulfate-Citrate Bile Salts Sucrose) agar is helpful in identifying Vibrio.
• CCFA (Cycloserine Cefoxitin Fructose Agar) is helpful in identifying Clostridium difficile.
• Sorbitol MAC is used to distinguish between E. coli and E. coli O157:H7.

Respiratory Tract

• Upper Respiratory Tract (URT) infections involve the oral cavity, nose, mouth, throat, epiglottis, and larynx.
• Lower Respiratory Tract (LRT) infections include the trachea, bronchi, bronchioles, and lung alveoli.
• The lower portion of the larynx is sterile under normal circumstances.
• Normal URT flora includes Staphylococci, Streptococci, Neisseria, Diptheroids, Haemophilus, Anaerobes, Spirochetes, and various yeast species.
• Common URT infections include thrush, laryngitis, epiglottitis, pharyngitis, tonsillitis, sinusitis, otitis media, and diphtheria.
• The common microbial pathogens in URT infections include respiratory viruses (e.g., Influenza, parainfluenza, RSV, adenovirus, rhinovirus, coronavirus, coxsackie A, EBV, CMV), S. pyogenes, and various β-hemolytic streptococci
• Arcanobacterium haemolyticum is another pathogen.
• Other pathogens in URT infections include H. influenzae, N. gonorrhoeae, C. diphtheriae, Bordetella pertussis and parapertussis, and various yeasts.

Specimen Collection (Respiratory)

• Specimens for upper respiratory tract infections include swabs, syringes and needles, and biopsies.
• For C. diphtheriae, use BAP, Loeffler, and tellurite media.
• Bordetella pertussis specimens are cultured on Bordet-Gengou blood agar.
• Posterior pharynx and tonsil swabs are common; these are often placed into transport media.
• Prioritizing group A Streptococcus testing frequently involves rapid antigen detection tests.
• Confirmation cultures are performed if the rapid tests are negative; gram staining is usually not performed or helpful.

Microscopic Examination (Respiratory)

• Gram stain is not normally a primary diagnostic tool.
• There's a large number of normal flora.

Culture (Respiratory)

• Primarily group A Streptococcus is cultured.
• Other pathogens like N. gonorrhoeae, Arcanobacterium haemolyticum and C. diphtheriae are considered if required.

Epiglottitis

• Primarily seen between 2 and 6 years of age.
• Related to H. influenzae type B.
• Airway obstruction is a serious clinical concern.
• The Hib vaccine has greatly reduced its incidence.

Sinusitis

• Often follows a viral URTI.
• Acute sinusitis agents: S. pneumoniae, H. influenzae, and others (M. catarrhalis, group A strep, anaerobes, S.aureus, GN).
• Chronic sinusitis agents: anaerobes, S. aureus (adults), and S. pneumoniae, S. aureus, viridans streptococci (children).
• Specimen collection involves diagnosis, radiological imaging, and therapeutic failure.
• Specimens are collected through sinus aspirates or sinus openings (sinus ostium).
• Use anaerobic transport media.
• Processing typically involves Gram stain, and anaerobic and aerobic cultures on BAP, CHOC, MAC, and anaBAP.
• Identification and susceptibility tests follow.

Otitis Media

• Most frequently occurs in children younger than 10 years old.
• Usually follows a viral upper respiratory infection.
• Common agents include S. pneumoniae, H. influenzae, group A Streptococcus, S. aureus, M. catarrhalis, and anaerobes.
• Specimen collection (tympanocentesis) involves aseptic puncturing and fluid aspiration.
• Collect in anaerobic transport media.
• Gram stain and culture are performed aerobically and anaerobically, usually on BAP, CHOC, and MAC.

Lower Respiratory Tract (LRT) Infections

• The LRT includes bronchitis, influenza, pneumonia, empyema, and tuberculosis.
• Important pathogens for LRT include respiratory viruses (including influenza A and B), pneumococcus (S. pneumoniae), H. influenzae, M. catarrhalis, M. pneumoniae, and Chlamydia species.
• Pathogens like S. aureus, Legionella, anaerobes, and mycobacteria can also cause LRT infections.
• Unusual community-acquired or nosocomial Mycobacteria infections may occur; C. trachomatis and C. pneumoniae may be seen.
• Specific agents involved in community-acquired pneumonia include Pneumococcal (S. pneumoniae) pneumonia, Mycoplasma pneumoniae, H. influenzae, and M. catarrhalis.

Bioterrorism Agents

• Potential bioterrorism agents include B. anthracis (anthrax), Y. pestis (plague), Coxiella burnetii (Q fever), and F. tularensis (tularemia).

Routes of Infection (Respiratory)

• Inhalation of aerosolized infectious material is common.
• Hematogenous spread (via bloodstream) can occur.
• Aspiration of oropharyngeal secretions is also a transmission route.
• Sputum is often collected, but it can be contaminated with normal flora.

Sputum Collection

• Expectorated sputum is collected in sterile containers.
• Induced sputum is often used to collect specimens from individuals who cannot expectorate or produce sputum.
• Bronchoscopy, bronchial lavage, bronchial brushings, and biopsies can provide specimens for analysis.
• Pleural fluid aspirates are also collected, and should be cultured anaerobically.

Sputum Gram Stain

• Gram staining of sputum helps determine the quality of the specimen for culture, and looks for contamination with normal flora.
• Low-power field (LPF) 10X examination identifies epithelial cells and polymorphonuclear leukocytes (PMNs).
• Quantities (e.g., rare, moderate, many) and types of bacteria are reported if visible under oil immersion (100X)

Routine Cultures (Respiratory)

• Common media used for sputum, tracheal aspirates, bronchial washings and brushings include BAP, CHOC, and MAC.
• For Cystic Fibrosis patients, special media may be required for Burkholderia cepacia, MRSA, and Pseudomonas.
• Cultures should be incubated in 35°C and CO2.

Anaerobic Cultures (Respiratory)

• Some LRT specimens specifically benefit from anaerobic environments, including pleural fluid aspirates, and lung biopsies.

Work-up (Respiratory)

• The work-up will vary based on the specific indication and quality of the specimens.
• Gram stain findings are important in determining downstream testing strategies.

Test your knowledge on gastrointestinal disorders with this quiz. It covers topics like gastritis, diarrhea characteristics, and the organisms that can cause these conditions. See how well you understand the complex interactions in the digestive system.