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65 Cards in this Set
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20 y/o white man presented with severe abdominal cramping and diarrhea. The pt. had lower abdominal discomfort and reported 8 loose bowel movements/day for the past 3 days. He recently noticed blood in the stool. He ate BBQ chicken 30 hours before onset of symptoms.
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Campylobacter jejuni
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what kind of bacteria is Campylobacter?
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gram negative curved rod
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most common bacterial cause of diarrhea
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Campylobacter jejuni
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pathogenesis of Campylobacter
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use flagella to invade the epithelium and release virulence factors
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causes an acute, nonspecific neutrophilic and monocytic inflammatory rxn causing tissue damage in the lamina propria & jejunal epithelium (similar to Crohn disease & UC)
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Campylobacter
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which organism has been associated with reactive arthritis in pts. with HLA-B27?
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C. jejuni
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treatment for C. jejuni
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rehydration b/c it's self-limiting
Erythromycin if antimicrobial therapy is required |
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6 family members presented with a 2 day history of low-grade fever, abdominal cramps, vomiting, and bloody diarrhea. They had eaten turkey 24 hours before the onset of symptoms.
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Salmonella typhimurium
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pathogenesis of Salmonella thyphimurium
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alter the brush border then use bacterial invasins to invade the intestinal epithelial cells causing an overwhelming influx of neutrophils
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treatment for Salmonella
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usually self-limting
for the immunocompromised, neonates, and elderly fluoroquinolone |
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A 41 y/o white man presented with a 3 day history of shaking chills, high fever, HA, abdominal pain, and generalized weakness. Mild diarrhea had started 2 days earlier and had been improving when the fever began. He also had erythematous maculopapular lesions ("rose spots") on his chest. He returned from India 10 d/a. CBC revealed ↑ % of monocytes and ↓ platelets.
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Salmonella typhi
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which organism carries a K or Vi antigen?
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Salmonella typhi
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what's the difference b/w transmission of Salmonella typhi and Salmonella typhimurium?
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Salmonella typhi only infects humans so it's transmitted via the fecal-oral route
Salmonella typhimurium is caused by ingesting poultry, eggs, and dairy products |
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pathogenesis of Salmonella typhi
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kill M CELLS and then invade the Peyer patch → migrate through terminal ileum into submucosal lymph nodes → invade mononuclear cells → infect the GB → reenter the intestine causing diarrhea
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treatment for Salmonella typhi
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nonfatal cases are eliminated in 3 weeks by humoral AB and activated macrophages
ciprofloxacin |
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71 y/o male returned from a 2 week stay in Mexico. The day after his return he experienced an acute onset of fever, crampy abdominal pain, and watery diarrhea. The next day he had tenesmus and mucus in the stool. The stools became grossly bloody and increased in number. Sigmoidoscopy showed ulcers and an erythematous friable mucosa.
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Shigella flexneri
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how can you differentiate b/w Shigella and E. histolytica since they both cause colonic ulcers?
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Amebic colitis has a gradual onset (1-2 week history of abdominal, pain, diarrhea, and tenesmus) & fever is uncommon
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how can you differentiate Shigella sonnei from the other strains?
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S. sonnei causes disease primarily among the elderly and young children & it causes less severe and watery diarrhea
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pathogenesis of Shigellae
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invade the M CELLS in the colon & are taken up by macrophages in the lamina propria → macrophages secrete inflammatory cytokines → infected intestinal epithelial cells produce attractants for neutrophils, which migrate b/w the epithelial cells, resulting in a BREAKDOWN of TIGHT JUNCTIONS
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what is essential for the cell-to-cell spread of Shigellae?
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the host protein, cadherin L-CAM
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mechanism of S. dysenteriae's Shiga toxin
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targets the 23S ribosomal RNA and inhibits protein synthesis; Stx kills intestinal epithelial cells and endothelial cells
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what organisms cause hemolytic-uremic syndrome & thrombotic thrombocytopenic purpura
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S. dysenteriae & E. coli
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treatment for Shigella
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Trimethoprim sulfamethoxazole
for resistant strains, use a quinolone such as ciprofloxacin |
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75 y/o man experienced the acute onset of severe abdominal cramps. Later in the morning, watery diarrhea occurring every 15-30 min. Diarrhea became markedly bloody. He was nauseated but not vomiting. He ate a hamburger 2 days ago.
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EHEC (enterohemorrhagic E. coli) aka E. coli O157:H7
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identification of E. coli O157:H7 is made on the basis of
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indole-positive
lactose-positive sorbitol-nonfermenting isolate that is positive for agglutination by O157-specific ABs |
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major vehicles of infection for EHEC
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ground beef and unpasteurized milk
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pathogenesis of EHEC
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in colonic mucosa, virulence factors efface the brush border; phage-encoded (Shiga) toxins kill colonic and renal endothelial cells
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treatment for EHEC
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fluid & electrolytes
most cases do NOT require antimicrobial therapy |
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which E. coli illness causes scant, purulent diarrhea with blood and WBCs?
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EIEC
enteroinvasive |
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fever is common in which E. coli illness?
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EIEC
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serious dehydration occurs in which E. coli illness?
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ETEC
enterotoxigenic |
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which E. coli illness affects the large intestine?
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EIEC & EHEC
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31 y/o man presented with sudden, severe, profuse rice-water diarrhea. He vomited several times and became slightly sweaty. He complained of muscle cramps and dizziness. He was on an H2-blocker for ulcer disease.
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vibrio cholerae
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significant risk factor for cholera
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hypochlorhydria
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transmission of cholera
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consumption of raw shellfish
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pathogenesis of cholera
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V. cholerae multiply and colonize the small intestine via long filamentous pili. Cholera toxin ↑ cAMP, which inhibits the absorptive Na transport system in villus cells and activates the excretory Cl transport system in crypt cells, causing accumulation of NaCl in the lumen
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treatment for cholera
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fluid & electrolytes
drug of choice is doxycycline |
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cause food poisoning within 1-6 hours
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S. aureus and B. cereus
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Pt. became ill 3 hours after eating ham at an office party. He had N/V and crampy abdominal pain. Sample of ham was positive for enterotoxin A.
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S. aureus
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How is S. aureus identified on blood agar?
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coagulase positive
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origin of S. aureus
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human - purulent discharges of an infected finger or eye, abscesses, acneiform facial eruptions, or nasopharyngeal secretions from the food preparers
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treatment of food poisoning caused by S. aureus
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self-limiting within 12-24 hours
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transmission of S. aureus food poisoning
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ham (meats)
mayo custard |
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transmission of B. cereus food poisoning
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reheated fried rice - N/V
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transmission of Clostridium perfringens food poisoning
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reheated meat dishes, gravy
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presentation of C. perfringens food poisoning
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watery diarrhea
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67 y/o man presented with fever, abdominal cramping, a frequent diarrhea (6-9 BMs/day) for 4 days. 3 w/a he had a hip replacement. He developed nosocomial pneumonia and was treated with cefuroxime and clindamycin.
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Clostridium difficile-associated diarrhea
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what kind of bacteria is C. difficile?
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anaerobic, gram (+), spore-forming rod
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what toxins does C. difficile produce and how can you detect them?
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exotoxins: toxin A and B
ELISA |
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most commonly incriminated antimicrobial agents in C. difficile associated diarrhea (CDAD)?
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clindamycin
cephalosporins ampicillin |
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where is C. difficile found?
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normal flora of large intestine
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pathogenesis of CDAD
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toxins A and B inactivate GTP-binding proteins by glycosylation, dysregulating the action of cytoskeleton in epithelial cells of the colonic mucosa & causing depolymerization of actin
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toxins cause erythematous and friable colonic mucosa, ulceration, and hemorrhagic necrosis
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C. difficile
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treatment of CDAD
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metronidazole or vancomycin
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what is pseudomembranous colitis?
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complication of CDAD characterized by multiple elevated, yellowish white plaques (pseudomembranes) within the colon
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diarrhea in infants is often due to ____. what is very common in winter months?
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viruses
Rotavirus |
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9 m/o baby girl presented with a 2 day history of vomiting, watery diarrhea, and fever. The pt. had been well until 24 hours before presentation. She is in a day care 3 days/week.
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Rotavirus (infantile gastroenteritis)
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what kind of virus is Rotavirus?
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non-enveloped RNA virus in the family of Reoviridae
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most widely used method of diagnosis for enteric viral agents
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assays that detect viral antigen in stool specimens b/c they grow poorly in cell culture
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pathogenesis of Rotavirus
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damaged cells on villi of small intestine are replaced by immature crypt cells that cannot absorb carbohydrates or other nutrients efficiently, resulting in osmotic diarrhea
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which immune factors are important in protection against rotavirus infection
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IgA and interferon
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158 students presented with N/V, diarrhea, HA, fever, and myalgias. Pt. had mild abdominal tenderness. Rectal exam was hemoccult negative.
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Norovirus (epidemic nonbacterial gastroenteritis)
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what kind of virus is Norovirus?
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single-stranded RNA virus in the Caliciviridae family
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clustered illnesses occur in families, communities, cruise ships, nursing homes, and other institutions
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Norovirus
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pathogenic changes in Norovirus infections
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shortening and atrophy of the villi, crypt hyperplasia, and infiltration of the lamina propria by PMNs and mononuculear cells
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