Gastrointestinal infections Notes


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This Osmosis High-Yield Note provides an overview of Gastrointestinal infections essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Gastrointestinal infections:


Entamoeba histolytica (Amebiasis)

Giardia lamblia

NOTES NOTES GASTROINTESTINAL INFECTIONS GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Gastrointestinal tract (GIT) inflammation caused by virus, bacteria, other parasites ▪ GIT mucosa inflammation → ulceration → epithelial disruption → edema, bleeding → fluid, electrolyte loss (diarrhea) → dehydration, electrolyte imbalance, anemia (bloody diarrhea) ▪ Mainly fecal-oral transmission RISK FACTORS ▪ Living/traveling to endemic areas, youth, immunosuppression (e.g. corticosteroid treatment, HIV co-infection), malnutrition, poor hygiene DIAGNOSIS ▪ Pathogen-dependent LAB RESULTS ▪ Stool culture TREATMENT ▪ Rehydration ▪ Antimicrobial therapy (pathogendependent) SIGNS & SYMPTOMS ▪ Fever, diarrhea, abdominal pain (cramps) ▪ Dehydration ▫ Sunken eyes, dry mouth, decreased urination, dark yellow urine (deep amber—severe), dry skin, syncope OSMOSIS.ORG 399
CRYPTOSPORIDIUM PATHOLOGY & CAUSES ▪ Cryptosporidiosis: diarrheal disease caused by Cryptosporidium (intestinal intracellular protozoan parasite) ▪ Life-cycle can be completed in one host ▫ Immunocompetent hosts: self-limited diarrhea ▫ Immunocompromised hosts: lifethreatening complications CAUSES ▪ Cryptosporidium oocysts (infective form) transmitted via fecal → oral route ▫ Infected individual/animal feces contaminates food; drinking, swimming water → fecally-contaminated food/ water ingestion ▪ Parasites → intestinal epithelial inflammation → villi structure distortion → ↓ absorption, ↑ secretion → watery diarrhea ▫ Sclerosing cholangitis/acalculous cholecystitis, respiratory cryptosporidiosis, pancreatitis RISK FACTORS ▪ Endemic-area exposure (tropical countries, Kuwait), immune deficiencies, poor hygiene ▪ Interpersonal transmission: sexual partners, daycare centers, household members COMPLICATIONS ▪ Dehydration, fluid and electrolyte imbalance SIGNS & SYMPTOMS ▪ Host’s immune status-dependant 400 OSMOSIS.ORG DIAGNOSIS LAB RESULTS Microscopic oocyte identification ▪ Stool; bile secretion, affected GIT aspirates; affected GIT tissue biopsy; respiratory secretion Polymerase chain reaction (PCR) ▪ More sensitive, specific ▪ Differentiates between Cryptosporidium genotypes Monoclonal antibodies and enzyme immunoassays (EIA) ▪ Monoclonal antibody test against oocyst wall ▪ More sensitive, specific than light microscope TREATMENT MEDICATIONS ▪ Immunocompetent host: antidiarrheal, antimicrobial agents ▪ Immunocompromised host: antiretroviral therapy (HIV-infected individuals), antimicrobial agents, azithromycin (severe diarrhea) OTHER INTERVENTIONS ▪ Immunocompetent host: oral/IV fluid/ electrolyte-loss replacement
Chapter 74 Gastrointestinal Infections Figure 74.1 Cryptosporidium organisms lining the crypt epithelium in an infected individual. OSMOSIS.ORG 401
ENTAMOEBA HISTOLYTICA (AMOEBIASIS) PATHOLOGY & CAUSES SIGNS & SYMPTOMS ▪ Amebiasis ▫ Caused by Entamoeba histolytica (anaerobic parasitic protozoan) ▪ Trophozoites bind to intestinal epithelial cells in colon, release lytic enzymes (e.g. cysteine proteinases) → epithelial cell lysis → trophozoites lyse inflamed/attracted immune cells → immune cell’s lytic enzymes ↑ release ▫ Intestinal mucosa ulcers → colitis → bowel necrosis → perforation → sepsis ▫ Tissue destruction → mucosa blood vessel injury, malabsorption, ↑ intestinal secretion → bloody diarrhea, amebic dysentery ▫ Blood vessel injury → trophozoites in blood stream → extraintestinal amebiasis (liver, pulmonary, cardiac, brain) ▪ Mostly asymptomatic; bloody diarrhea, mucus in stool (severe dysentery); abdominal pain; fever; weight loss; right upper-quadrant pain, jaundice (liver); cough (pulmonary); dehydration RISK FACTORS ▪ Endemic-area exposure (Africa, Southern Asia, Central America) ▪ Intimate partner transmission possible ▪ Youth ▪ Malnutrition ▪ Immunodeficiency (e.g. malignancy, corticosteroid treatment, HIV) ▪ Poor hygiene COMPLICATIONS ▪ Amebic liver abscess rupture ▫ Pericarditis, peritonitis ▪ Toxic megacolon ▪ Cerebral amebiasis → brain abscess → ↑ intracranial pressure ▪ Cutaneous amebiasis ▪ Dehydration 402 OSMOSIS.ORG DIAGNOSIS DIAGNOSTIC IMAGING X-ray ▪ Liver CT scan, MRI, ultrasound ▪ Cystic intrahepatic cavity detection LAB RESULTS Microscopic identification ▪ Cysts/trophozoites in stool/pus (e.g. liver abscess) Antigen detection ▪ Enzyme-linked immunosorbent assay (ELISA), radioimmunoassay, immunofluorescence PCR ▪ Entamoeba DNA detection Serology ▪ Entamoeba antibodies detection Sigmoidoscopy/colonoscopy ▪ Histological examination biopsies
Chapter 74 Gastrointestinal Infections TREATMENT MEDICATIONS ▪ Antibacterial agents ▫ Invasive amoebic colitis ▪ Luminal agents ▫ Intraluminal cysts, trophozoites ▪ Metronidazole ▫ Amebic liver abscess ≤ 10cm/3.94in ▪ Broad-spectrum antibiotics ▫ Suspected perforation, bacterial superinfection SURGERY ▪ ▪ ▪ ▪ ▪ Figure 74.2 Trophozoites of Entamoeba histolytica in a colonic biopsy. The trophozoites have ingested red blood cells. Massive GIT bleeding Amebic liver abscess > 10 cm/3.94 in Ruptured amebic liver abscess Perforated amebic colitis Toxic megacolon OTHER INTERVENTIONS ▪ Rehydration GIARDIA LAMBLIA PATHOLOGY & CAUSES ▪ Giardiasis ▫ Diarrheal disease caused by Giardia intestinalis/Giardia duodenalis (flagellated protozoan parasite, colonizes small intestine) ▪ Pathogenesis not well understood ▪ Infection causes microvilli shortening → intestinal malabsorption, hypersecretion → diarrhea CAUSES ▪ Contaminated/untreated water ingestion ▪ Contaminated food (uncommon) RISK FACTORS ▪ Endemic-area exposure (tropical countries), immunosuppression, comorbidities (e.g. cystic fibrosis), poor sanitation COMPLICATIONS ▪ Weight loss; dehydration; zinc, disaccharidase deficiency; malabsorption syndrome (adult); growth delay (children) OSMOSIS.ORG 403
SIGNS & SYMPTOMS ▪ Usually asymptomatic Acute giardiasis ▪ 7–14 days after infection exposure ▪ Diarrhea, malaise, abdominal pain, flatulence, nausea/vomiting, malodorous stool, steatorrhea, fever (uncommon) Chronic giardiasis ▪ > 18 days after infection exposure ▪ Loose stools (not typical diarrhea), profound weight loss (occasionally), abdominal pain, borborygmus (moving gas/fluid → GIT gurgling sound), flatulence, burping, malaise, fatigue, depression Figure 74.3 Giardia lamblia in a cytology specimen. DIAGNOSIS LAB RESULTS Antigen detection assays ▪ Trophozoite antigen (stool) detection Nucleic acid amplification assays (NAAT) ▪ Giardia DNA detection Stool microscopy ▪ Giardia cyst detection TREATMENT MEDICATIONS ▪ Antimicrobial therapy ▫ Paromomycin (pregnant/lactating individuals) 404 OSMOSIS.ORG Figure 74.4 A duodenal biopsy demonstrating giardia organisms in the duodenal crypt.

Osmosis High-Yield Notes

This Osmosis High-Yield Note provides an overview of Gastrointestinal infections essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Gastrointestinal infections by visiting the associated Learn Page.