A medical technician is trying to isolate a pathogen from the sputum sample of a patient. The sample is heat fixed to a slide then covered with carbol fuchsin stain and heated again. After washing off the stain with clean water, the slide is covered with 1% sulfuric acid for decolorization. The sample is rinsed again and stained with methylene blue. Microscopic examination shows numerous red, branching filamentous organisms. Which of the following is the most likely isolated pathogen?
ACryptococcus neoformans
BTropheryma whipplei
CNocardia asteroides
DRickettsia rickettsii
EStaphylococcus aureus
An investigator is studying the growth of an organism in different media. The organism is inoculated on a petri dish that contains heated sheep blood, vancomycin, nystatin, trimethoprim, and colistin. The resulting growth medium is incubated at 37°C. Numerous small, white colonies are seen after incubation for 48 hours. This organism is most likely to cause which of the following conditions?
APontiac fever
BPseudomembranous colitis
CHemolytic uremic syndrome
DOral thrush
EGonorrhea
Blood cultures are sent to the laboratory and empiric treatment with intravenous vancomycin is started. Blood cultures grow gram-negative bacilli identified as Cardiobacterium hominis. Which of the following is the most appropriate next step in management?
ASwitch to intravenous gentamicin
BSwitch to intravenous ampicillin
CSwitch to intravenous ceftriaxone
DSwitch to intravenous cefazolin
EAdd intravenous rifampin
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