GI bugs 1 - Parasites

• 1. Ingestion of embryonated eggs; Direct contact; autoinfection
• 2. embryonated eggs
• 3. Eggs collected in perianal area "Scotch test" (egg flat on one side)

1. Gravid female migrates to perianal region to lay eggs

• 1. Enterobiasis
• 2. Perianal pruritus especially at night
• 3. Pyrantel pamoate (treat the entire family)

• 1. Ingestion of contaminated food or water
• 2. Egg
• 3. Eggs in stool (bile-stained, thick shell, round/oval knobby eggs); Occasionally adult worms in stool or coming out from mouth & nose

1. In small intestine: egg --> larvae --> invade intestinal mucosa --> blood --> lungs --> alveoli --> up to throat --> swallowed --> back to small intestine --> adults worms multiplication

• 1. Ascariasis
• 2. Abdominal pain and intestinal obstruction when high worm burden; peritonitis; Cough, pneumonitis during lung phase of larval migration
• 3. Albendazole or Mebendazole

• 1. Ingestion of soil-contaminated food
• 2. Embryonated egg
• 3. Eggs in stool (bile-stained, barrel-shaped with bipolar plugs)

1. Multiplication in large intestine; possible penetration of intestinal mucosa

• 1. Trichuriasis
• 2. Depend on worm burden; Heavy infections --> abdominal pain, bloody diarrhea, appendicitis and rectal prolapse
• 3. Mebendazole

• 1. Larva penetrates intact skin; Direct contact with contaminated soil
• 2. Filariform larva
• 3. Eggs in stool (ellipsoidal shade, thin shell, non-bile stained)

1. Larvae --> invade intestinal mucosa --> blood --> lung --> alveoli --> up to throat --> swallowed --> back to small intestine --> adults worms mouthparts designed for sucking blood

• 1. -
• 2. Skin manifestations at site of entry; Pneumonitis during lung phase; Gastrointestinal symptom: nausea, vomiting, diarrhea; iron deficiency anemia
• 3. Albendazole or Mebendazole

• 1. Larva penetrates intact skin; autoinfection
• 2. Filariform larva; autoinfection
• 3. Rhabditiform larvae in stool

1. Larvae --> invade intestinal mucosa --> blood --> lungs --> alveoli --> up to throat --> swallowed --> back to small intestine --> adults worms

• 1. Strongyloidiasis
• 2. Skin manifestations at site of entry; Pneumonitis during lung phase; Gastrointestinal symptom: nausea, vomiting, diarrhea
• 3. Ivermectin

• 1. Ingestion of raw beef containing cysticerci
• 2. Cysticerci
• 3. Proglottids and/or eggs in stools

1. Intermediate host = cattle; Definitive host = humans

• 1. Taeniasis
• 2. Asymptomatic or mild abdominal pains
• 3. Praziquantel

• 1. Ingestion of water or food contaminated with eggs
• 2. Egg
• 3. Cysticercus in the tissue; antibody detection

1. Eggs hatch in stomach, release oncosphere --> penetrate intestinal wall --> circulation --> different tissues to develops into cysticercus

• 1. Cysticercosis
• 2. Cysticerci in the muscles: No symptoms; Cysticerci in the eyes: blurry or disturbed vision; Neurocysticercosis: seizures, and headaches
• 3. Albendazole; surgery

• 1. Ingestion of raw fish containing sparganum (plerocercoid)
• 2. Plerocercoid
• 3. Eggs in stool

1. two intermediate hosts = crustaceans then fish; definitive host = humans

• 1. Diphyllobothriasis
• 2. Asymptomatic to abdominal pain, diarrhea, vomiting, Vit B12 deficiency
• 3. Praziquantel + Vit B12

• 1. Traveler's Diarrhea
• 2. Culture, Immunassays (toxin detection)
• 3. High
• 4. Watery diarrhea, abdominal cramps
• 5. Fluoroquinolones (ciprofloxacin)

• 1. Enterobacteriaceae: gram (-) motile rods, facultative anaerobes, oxidase(-), lactose (+)
• 2. Human's intestine
• 3. Fecal-oral; ingestion of contaminated food or water

• Cfa (colonization factor antigen) - adherence
• ST (heat stable toxin) - guanylate cyclase activation --> ↑cGMP
• LT (heat labiletoxin, AB toxin) - ADP ribosylates G-protein --> constant activation of adenylate cyclase --> ↑cAMP
• High cGMP or cAMP --> hypersecretionof H2O and Cl, decrease in Na reabsorption

• 1. Watery diarrhea
• 2. Culture, Immunassays (toxin detection)
• 3. Low in infants (person-to-person); high in adults
• 4. Watery diarrhea, abdominal cramps
• 5. Fluoroquinolones (ciprofloxacin)

• Bfp (Bundle-forming pilus) - adherence
• TypeIII secretion system --> cytoskeleton proteins modification
• in host cell
• Attaching and effacing lesions --> changes in microvilluðmalabsorption

• 1. Chronic diarrhea
• 2. Culture, Immunassays (toxin detection)
• 3. Chronic watery diarrhea (in AIDS patients), abdominal cramps
• 4. Fluoroquinolones (ciprofloxacin)

AAF (Aggregative Adherence Fimbriae) --> autoagglutination in “stacked-brick” arrangement + biofilm --> malabsorption

• 1. Curved gram(-) rods; facultative anerobes, oxidase(+), motile (polar flagella)
• 2. High

• 1. Cholera
• 2. Warm costal water
• 3. Ingestion of contaminated water or shellfish
• 4. Profuse watery diarrhea; "rice-water" stools; severe dehydration
• 5. TCBS (Thiosulfate citrate bile salts sucrose agar) - yellow colonies
• 6. Azithromycin

• 1. Watery diarrhea
• 2. Warm costal water (marine life)
• 3. Ingestion of contaminated seafood
• 4. Watery diarrhea, abdonimal cramps, nausea
• 5. TCBS - blue-green colonies; Halophilic
• 6. Self-limiting

• Tcp (toxin coregulated pilus) - adherence
• Ctx (cholera toxin, AB-toxin, on lysogenic CTX phage) - ADP ribosylates G protein--> constant activation of adenylate cyclase --> ↑cAMP --> hypersecretion of H2O and Cl; decrease in Na reabsorption

Enterotoxin - chloride & water secretion

• 1. Watery diarrhea
• Necrotizing enteritis in New Guinea natives
• 2. Soil and human colon
• 3. Ingestion of contaminated meat
• 4. High

• 1. Watery diarrhea, abdominal cramps
• Abdominal pain, vomiting, bloody diarrhea in New Guinea natives
• 2. Culture; Immunoassay (enterotoxin detection)
• 3. Self-limiting or Penicillin in New Guinea

• Enterotoxin or
• Beta-toxin (lethal toxin): necrotizing destruction of jejunum (NG natives)

• 1. Gram(+) rods, motile; spore forming
• 2. Ubiquitous
• 3. Emetic Gastroenteritis - Ingestion of preformed toxin (rice) or Diarrheal Gastroenteritis - Ingestion of food contaminated with spore
• 4. High

• 1. Emetic gastroenteritis and
• Diarrheal gastroenteritis
• 2. Onset <6h after ingestion - Vomiting, nausea, abdominal cramps and
• Incubation time >6h - Watery diarrhea, nausea, abdominal cramps
• 3. Isolation of organism from implicated food
• 4. Self-limiting

• Emetic gastroenteritis: Heat-stable enterotoxin (if spore survive cooking --> germination + toxin production in non-refrigerated food)
• Diarrheal gastroenteritis: Heat-labile enterotoxin (germination of spore + toxin production in intestinal tract)

• 1. Gram(+) cocci in cluster, catalase(+); coagulase(+)
• 2. Normal human flora
• 3. Ingestion of preformed toxin (potato salad, custard…)

• 1. Staphylococcal food poisoning
• 2. Onset <6h after ingestion - Vomiting, nausea, abdominal cramps and watery diarrhea
• 3. Isolation of toxin producing bacteria (mannitol salt agar)
• 4. Self-limiting

Heat stable enterotoxin

• 1. Enterobacteriaceae: gram(-) rods, facultative anaerobes, oxidase(-) and Motile; lactose(+), sorbitol(-)
• 2. Intestine of cattle
• 3. Fecal-oral; ingestion of contaminated food or water
• 4. Low --> person-to-person transmission

• 1. Hemorrhagic Colitis; Hemolytic Uremic Syndrome (HUS)
• 2. Bloody diarrhea (no leucocytes), abdominal cramps, vomiting; oliguria+renal failure (HUS)
• 3. Culture on Sorbitol containind MacConkey agar (sorbitol(-)); Immunassays
• 4. Antibiotic therapy not recommended; dialysis in HUS cases

• Attaching & Effacing lesions (no invasion)
• Shiga toxin (AB toxin) - cleaves rRNA --> blocks protein synthesis --> cell death; circulating shiga toxin can bind to renal tissue --> renal failure (HUS)

• 1. Enterobacteriaceae: gram(-) rods, facultative anaerobes, oxidase(-) and Motile; lactose(+)
• 2. Human's intestine
• 3. Fecal-oral; ingestion of contaminated food or water
• 4. High

• 1. Dysentery
• 2. Bloody diarrhea with pus, fever, abdominal cramps, nausea
• 3. Immunassays
• 4. Fluoroquinolones (ciprofloxacin), TMP/SMX

Invasion (Ipa: invasion plasmid antigen) and destruction of colonic epithelium

• 1. Enterobacteriaceae: gram(-) rods, facultative anaerobes, oxidase(-) and Non-motile; lactose(-)
• 2. Human's intestine
• 3. Fecal-oral; ingestion of contaminated food or water
• 4. Low --> person-to-person transmission

• 1. Dysentery
• 2. Bloody diarrhea with pus, fever, abdominal cramps, nausea
• 3. Hektoen enteric agar: lac(-), H2S(-)ð green colonies
• 4. Fluoroquinolones (ciprofloxacin), TMP/SMX

• Invasion (Ipa) of colonic mucosa through M cells
• Invade basal surface of enterocytes --> cell death + inflammation; shiga-toxin

• 1. Enterobacteriaceae: gram(-) rods, facultative anaerobes, oxidase(-) and Motile; lactose(-)
• 2. Intestinal tracts of animals and humans
• 3. Fecal-oral; ingestion of comtaminated food (eggs, poultry) or water; direct contact with reptiles
• 4. High

• 1. Dysentery-like diarrhea; possible bacteremia
• 2. Bloody diarrhea with pus, fever, abdominal cramps, nausea
• 3. Hektoen enteric agar: lac(-), H2S(+)ð blue colonies with dark center
• 4. Fluoroquinolones (ciprofloxacin), TMP/SMX

Ruffles, invasion, inflammation

• 1. Enterobacteriaceae: gram(-) rods, facultative anaerobes, oxidase(-) and Bipolar staining; lactose (-)
• 2. Animal's intestine
• 3. Fecal-oral; ingestion of contaminated food or water
• 4. High

• 1. Dysentery-like diarrhea
• 2. Bloody diarrhea, abdonimal cramps, fever; mesenteric lymphadenitis (mimics acute appendicitis)
• 3. lac(-), H2S(-); Stool culture at 25°C
• 4. Gentamycin (alt: fluoroquinolones...)

Invade M cells: Yops and Type III secretion system; spread --> microabscesses in lymph nodes

• 1. Thin gram(-) rods; gull-wing shaped; microaerophile; oxydase(+)
• 2. Animal's intestine
• 3. Fecal-oral; ingestion of contaminated food (poultry), milk or water; direct contact with pets
• 4. Moderate to Low (but person-to-person transmission unusual)

• 1. Dysentery-like diarrhea
• 2. Bloddy diarrhea with pus, fever, abdominal pain; Complications: Guillain-Barre syndrome, Reactive arthritis
• 3. Culture (microaerophilic conditions)
• 4. Erythromycin (alt:ciprofloxacin)

Damage to intestinal mucosa (toxin production, translocation, invasion); virulence factors poorly defined

• 1. Protozoa
• 2. ?
• 3. Fecal-oral;Ingestion of contaminated food or water; Direct contact
• 4. Low

• 1. Amebiasis
• 2. Amoebic dysentery; Liver abscess, lung abscess, brain infection…
• 3. diagnostic form: Cysts and trophozoites in stool
• 4. Tinidazole (asymptomatic infec.); Metronidazole then iodoquinol (symptomatic intestinal or extraintestinal infec.)

Infecive form: cyst --> excystation in small intestine --> trophozoites multiply and produce cysts in large intestine; possible invasion to extraintestinal sites via bloodstream

• 1. Enterobacteriaceae; Non-motile; lactose(-), H2S(+)
• 2. Humans only
• 3. Fecal-oral; ingestion of contaminated food or water
• 4. Moderate-low (possible person-to-person transmission)

• 1. Typhoid fever
• 2. Sustained fever and headache; possible rash and/or diarrhea, dark stool; persistent bacteremiað myocarditis, encephalopathy
• 3. Culture from blood or feces
• 4. Fluoroquinolones (ciprofloxacin)

Invasion of M cells; Multiply in macrophages; bacteremia and invasion of RES (mesenteric lymph node, liver, spleen); infection of gallbladder (carrier state); Capsule (Vi polysaccharide); endotoxin

• 1. Gram(-) rods; bacillary or spiral shape; microaerophile; oxydase(+); urease (+)
• 2. Stomach of humans and animals
• 3. Fecal-oral; oral-oral

• 1. Gastritis, peptic ulcer, gastric adenocarcinoma, lymphomas
• 2. ?
• 3. Biopsy=> microscopy, culture, urease test; Stool antigen test; Urea breath test; PCR
• 4. Proton pump inhibitor + clarithromycin + amoxicillin

Mucous layer invasion (Mucinase, flagella) + Alteration of gastric acid production (urease --> ammonium production) ðInflammation of gastric mucosa --> Tissue destruction

• 1. Large gram(+) rods; Spore forming; Strict anaerobes
• 2. Vegetative form: human carrier; Spore in environment (hospital rooms)
• 3. Often endogenous infection

• 1. Antibiotic-associated diarrhea or Antibiotic-associated pseudomembranous colitis
• 2. Watery diarrhea or Profuse diarrhea, abdominal cramps, fever
• 3. Immunoassays (toxins detection); colonoscopy (pseudomembrane)
• 4. Discontinue implicated antibiotic; Vancomycin or Metronidazole

Exposure to antibiotics --> overgrowth of C.difficile or

• Toxin A - Enterotoxin: disrupts tigh junctions between enterocytes + induces inflammation --> watery diarrhea
• Toxin B - cytotoxin: modification of enterocyte cytoskeleton --> cell death