Microbes -Steinauer Flashcards
Your patient is a 30-year-old woman with non-bloody diarrhea for the past 14 hours. Which of the following organisms is LEAST likely to cause this illness? A. Clostridium difficile B. Streptococcus pyogenes C. Shigella dysenteriae D. Salmonella enteritidis
B. Streptococcus pyogenes
gram + coccus, catalase -, beta hemolytic, bacitracin sensitive
Which of the following is most likely to cause bloody diarrhea? A. Vibrio cholerae B. Shigella flexneri C. Giardia lamblia D. Staphylococcus aureus
B. Shigella flexneri
low inoculum size
Your patient is a 53-year-old woman who returned from Peru yesterday where there is an epidemic of cholera. Which is likely to be her chief complaint? A. Fever and malaise B. Dysentery C. Watery diarrhea D. Upper right quadrant pain
C. Watery diarrhea
cholera common in travelers
What pathogen leads to “rice water stools”? What are the features of this? What are the enterotoxins associated with this?
V. cholerae (gram -, curves rods, oxidase +)
- CT: classic cholera toxin (A-B toxin that ribosylates G protein and over produces cAMP–> activate CFTR –> Cl- and HCO3- secretion –> water efflux)
- VCC –>makes anion permeable holes in cell surface–> Loss of Cl-
- ACE (accessory toxin) –> Decrease absorption of Na+
What are the different types of E. coli and what are the features of each ?
- ETEC=enterotoxigenic
- Travellers
- Heat labile toxin (inc cAMP) (LT)
- Heat stabile toxin (ST): activates CFTR
- EPEC=enteropathogenic
- peds
- type III secretion, destroys microvilli
- A and E lesions
- EAEC=aggregate
- aggregate and from bricks (by pili)–> persistent and resistant to antibiotics (>14 days)
- biofilm
- EHEC=hemorrhagic
- shiga like toxin (verotoxin) –> binds to intestinal and kidney cells –>can cause HUS
- low inoculum
- food/cattle reservoir
*Which form of E. coli should not be treated with antibiotics?
EHEC*
Which E. coli can lead to hemorrhagic colitis (HUS)? Is this inflammatory?
EHEC
noninflammatory but bloody
What are some key features of Shigella? How is it spread?
- Humans and primates
- Low inoculum (spreads easily)
- Invasive –>inflammatory
- spread cell to cell with actin tails
- day care center risk factor
What are some key features of Salmonella? What can Salmonella cause? How is it spread?
gram - bacilli, lactose -, motile, H2S gas production
- Enteric disease
- Typhoid fever
-Animal reservoirs and food borne illness
What is the major cause of bloody diarrhea in kids? How is it transmitted?
Campylobacter (gram -, motile, curved rods)
food (poultry, meat, milk)
Several 4-year-old children who attend the same preschool are hospitalized for severe, bloody diarrhea. All of the children ate at the same fast-food restaurant during class field trip. In the second week of the illness, one of the children additionally develops thrombocytopenia, hemolytic anemia, and acute renal insufficiency. The most likely causative agent is: A. EAEC B. EHEC C. EIEC D. EPEC E. ETEC F. Campylobacter jejuni
B. EHEC
this kid got HUS
Your patient is a 56-year-old woman who was treated with ampicillin for cellulitis caused by Streptococcus pyogenes. Several days later she developed bloody diarrhea and a colonoscopy indicated pseudomembranous plaques. Which of the following describes the most likely pathogen?
A. It is an anaerobic Gram-positive rod that produces exotoxins
B. It is a comma shaped Gram-negative rod that grows best at 41C
C. It is a facultative Gram-negative rod that forms spores
D. It is an obligate intracellular parasite that grows in cell culture but not blood agar
E. It is a parasite that produces cysts with four nuclei
A. It is an anaerobic Gram-positive rod that produces exotoxins
(c. diff)
What color would Salmonella appear on MacConkey Agar? What color will EHEC appear?
Salmonella =clear
(does not ferment lactose)
EHEC=pink
What color will EHEC appear on a Macconkey sorbitol agar?
Clear
What is Hektoen’s agar used to differentiate? What colors will these turn?
Shigella (blue/green)
Salmonella =black (produces H2S)
How should Vibrio cholera be tested for?
culture is the gold standard (TCBS agar)
A 20-year-old man presents with watery diarrhea that has lasted 3 days. He just returned from a trip to Kenya 2 days ago. He has no fever and no fecal leukocytes are detected in a stool sample. The pathogen is an oxidase negative, Gram-negative rod that grows pink colonies on Mac Conkey Agar. Which of the following is most likely? A. Vibrio cholerae B. Shigella sonnei C. Campylobacter jejuni D. ETEC E. EHEC F. EPEC
D. ETEC
What complications can Entamoeba histolytic produce?
Liver abscess
eyes, genital problems
A 43-year-old man with history of polysubstance abuse and bipolar disorder is involuntarily admitted to the hospital because of persistent bloody diarrhea for the past 1 week. Quantitative analysis of stool shows spherical, quadrinucleate, thin walled cysts measuring 10-20um in diameter. Which is the most likely pathogen? A. Cryptosporidium parvum B. Dientamoeba fragilis C. Entamoeba histolytica D. Giardia lamblia E. Shigella sonnei
C. Entamoeba histolytica
A 24-year-old man comes to the physician because of prolonged diarrhea. He undergoes esophagogastroduodenoscopy with biopsy of the small intestine. Microscopic examination of the biopsy specimen shows numerous crescent-shaped protozoa adjacent to the epithelial brush border. Which is the most likely etiologic agent? A. Cryptosporidium parvum B. Dientamoeba fragilis C. Entamoeba histolytica D. Giardia lamblia E. Shigella sonnei
D. Giardia lamblia
Which of the following host defense mechanisms is the MOST important for preventing dysentery caused by Salmonella? A. Gastric acid B. Salivary enzymes C. Normal flora of the mouth D. Alpha interferon
A. Gastric acid
Which one of the following pathogens has the LOWEST 50% infectious dose (ID50)? A. Shigella sonnei B. Vibrio cholerae C. Salmonella typhi D. Campylobacter jejuni
A. Shigella sonnei
Which one of the following pathogens that infects the GI tract is most likely to cause bacteremia? A. Shigella sonnei B. Vibrio cholerae C. Salmonella typhi D. Campylobacter jejuni
C. Salmonella typhi
A 3-year-old boy who attends a large daycare facility suddenly develops a fever, vomiting, diarrhea, and abdominal pain. When he is brought to the ED three days later, he has more than 10 bowel movements in a day, and mucus, blood, and pus are seen in the stool. He has developed weight loss and severe dehydration. His temperature is 38C, blood pressure is 90/60 mm Hg, pulse is 130 min, and respirations are 20/min. O2 saturation is 98%. No rash is observed. Which is most likely?
A. Norovirus B. Rotavirus C. Salmonella enterica typhi D. Shigella sonnei E. Vibrio cholerae
D. Shigella sonnei
The pathogenesis of which of the following organisms is MOST likely to invade the intestinal mucosa? A. V. cholerae B. Entamoeba histolytica C. Giardia Lamblia D. ETEC E. EPEC
B. Entamoeba histolytica
A 10-year-old male has become pale and seems to have lost his normal energy. On examination, the child’s skin is somewhat pale and clammy, and a complete blood count detects a microcytic, hypochromic anemia. A fecal sample from this child will most likely show:
A. Brown, rough shelled ova B. Golden, football shaped ova with bipolar plugs C. Living larvae D. Oval, golden, clear, shelled ova E. Spined eggs
D. Oval, golden, clear, shelled ova
