Infectious Diseases II

Answer: D

The CDC definitions for CAUTIs, which are used by the

CMS reporting system, were recently updated. Because

this patient had his urinary catheter removed for more

than 24 hours before developing UTI symptoms, this

case does not satisfy the definition of CAUTI (Answer

D is correct; Answers A and C are incorrect). The cur-

rent CDC CAUTI definitions do not consider the results

of a urinalysis (Answer B is incorrect).

This patient presents with community-acquired men-

ingitis. The high opening pressure is suggestive of a

bacterial etiology, of which the most prevalent pathogen

for this patient’s risk factors and age is S. pneumoniae.

Administering dexamethasone before initiating anti-

biotic therapy decreases mortality in patients with S.

pneumoniae meningitis. (Answer A is correct) Awaiting

laboratory and microbiologic test results analysis may

cause inappropriate delays in therapy (Answer B is

incorrect). In addition, although administering antimi-

crobials is a good idea, the beneficial effects associated

with dexamethasone are diminished if administered

after antimicrobials have been initiated. At the very

least, corticosteroids should be administered con-

comitantly with antimicrobials (Answer C and D are

incorrect).

Answer: D

The PNA FISH technology is designed to identify

pathogens earlier. It performs well, with good sensitivity

and specificity; hence, identification of C. parapsilosis

should not require verification from culture (Answer

A is incorrect). The drug of choice for the treatment of

C. parapsilosis is fluconazole (Answer D is correct).

Although echinocandin, voriconazole, and ampho-

tericin would all cover C. parapsilosis, they all have a

broader spectrum than is necessary, making them not

the ideal choice (Answers A–C are incorrect).

Answer: A

Although PCT is a promising biomarker for the detec-

tion of bacterial infections, it must be interpreted within

the context of the patient’s clinical course. In this case,

the patient has clear signs and symptoms of infec-

tion, together with signs of hypoperfusion. A low PCT

should not be used to guide therapy discontinuation in

this case, and antibiotics should be continued to cover

the most likely pathogens (Answer A is correct; Answer

B is incorrect). Because the patient is admitted with

presumed community-acquired pneumonia, the com-

bination of ceftriaxone and azithromycin is appropriate

right now (Answers C and D are incorrect).

Answer: B

This patient is being treated for an ESBL E. coli UTI,

in which the source of the infection (urinary catheter)

is removed. The patient also has signs of response to

piperacillin/tazobactam with resolution of leukocyto-

sis and fever. In this case, given the low inoculum of

the infection, initial response, removal of source, and

low MIC, continuing piperacillin/tazobactam is the best

choice (Answer B is correct). This choice may only be

the case for UTIs, not other sources of infection (e.g.,

bacteremias). Traditionally, it was widely believed

that ESBL infections had to be treated with carbapen-

ems. However, recent evidence suggests that β-lactam/

β-lactamase inhibitor combinations are a suitable

option. In the era of antimicrobial stewardship, the pres-

ervation of carbapenem therapy should be regarded with

high importance (Answer A is incorrect). This current

culture has an MIC of 4 mcg/mL to cefepime, which,

according to the updated CLSI guidelines, would be

considered resistant (Answer C is incorrect). Because

the patient is responding to the current therapy, combi-

nation therapy is unnecessary (Answer D is incorrect).

Answer: D

This patient is being treated for MRSA right-sided

endocarditis, with the presumed source from her

tunneled dialysis catheter. According to the IDSA

guidelines for the treatment of MRSA, treatment

with vancomycin of an isolate with an MIC of 2 mcg/

mL or less should be determined by the patient’s

response to therapy, regardless of the actual MIC. This

patient has responded to therapy with the presumed

clearance of blood cultures and resolution of signs and

symptoms of infection. Hence, continuing vancomycin

and targeting a trough of 15–20 mcg/mL is the most

appropriate choice (Answer D is correct). Linezolid is

not indicated for the treatment of endocarditis (Answer

A is incorrect). Adding gentamicin and rifampin is