Infectious Diseases I

gram-negative bacilli and yeast (Answer A is incorrect).

Empiric antimicrobial therapy is indicated for suspected

infected pancreatitis. Extended-spectrum carbapenems,

which achieve relevant pancreatic fluid concentrations,

are effective in the management of infected pancreatitis.

Addition of anti-candidal therapy is indicated, given the

presence of yeast on the Gram stain (Answer D is cor-

rect; Answers B and C are incorrect).

This patient is thought to have fulminant (IDSA 2017)

CDI, given his recent exposure to broad-spectrum

antibiotic therapy, signs of infection, CT findings, and

the presence of hypotension. Combination therapy with

metronidazole and enteral vancomycin is indicated

(Answers A and D are incorrect). The presence of

ileus requires consideration of adding intracolonic

vancomycin because of possible impaired delivery to

the colon through enteral routes (Answer B is correct;

Answer C is incorrect).

The patient in this case presents with what is likely an

initial-episode, severe CDI, as supported by new-onset

diarrhea and clinical signs and symptoms of infection.

Of note, the patient is not hypotensive and has a lactate

below 2–4 mmol/L, suggesting the absence of shock or

other defining features of fulminant CDI; thus, mono-

therapy with enteral vancomycin is the best available

answer (Answer D is correct). Although the 2021 IDSA/

SHEA focused guideline update recommends fidaxomi-

cin for non-fulminant, first-episode CDI, oral/enteral

vancomycin is an acceptable alternative, especially if

fidaxomicin is unavailable. Combination therapy with

oral/enteral vancomycin and intravenous metronidazole

should be reserved for a complicated CDI (Answer C

is incorrect), and intravenous metronidazole is not rec-

ommended (Answer B is incorrect). The combination

of metronidazole and intracolonic is recommended for

patients with a complicated CDI and concern for ileus or

inability to deliver oral/enteral vancomycin to the colon

(Answer A is incorrect).

For an initial severe episode of CDI, the guidelines

recommend that the patient receive either fidaxomi-

cin or vancomycin for 10 days (Answer B is correct).

A duration of 14 days could be considered for patients

receiving metronidazole when vancomycin or fidaxomi-

cin is unavailable (Answer C is incorrect). Duration of 5

days or 4 weeks is not supported for the initial treatment

of CDI (Answers A and D are incorrect).

Necrotizing fasciitis is a severe, life-threatening

infection that is often polymicrobial. Prompt surgical

debridement of necrotic tissue and broad-spectrum

antibiotic therapy are the mainstays of initial therapy.

Agents active against S. pyogenes, MRSA, and aerobic

and anaerobic gram-negative bacilli should be initiated

empirically, together with adjunctive clindamycin

added, which may decrease bacterial toxin production.

The empiric regimen of piperacillin/tazobactam,

vancomycin, and clindamycin is most appropriate, given

the severity of infection despite the absence of traditional

multidrug-resistant organism risk factors (Answer C

is correct). Penicillin G is not broad enough (Answer

B is incorrect), and the combination of ceftaroline and

vancomycin does not contain clindamycin (Answer A is

incorrect). Combination of clindamycin and linezolid do

not include empiric gram-negative coverage. (Answer D

is incorrect).

The intraoperative cultures of this patient’s necrotizing

infection are of concern for S. pyogenes. S. pyogenes

produces exotoxin, which is associated with tissue

necrosis. Although bactericidal antibiotic therapy

is necessary for eradicating S. pyogenes, adjunctive

clindamycin may decrease toxin production, which could

limit the extent of tissue necrosis (Answer B is correct).

Vancomycin should be reserved for patients with an S.

pyogenes infection who have a β-lactam allergy because

β-lactam resistance is rare (Answer C is incorrect).

Moreover, synergistic antibiotic therapy with gentamicin

is not needed, given the effectiveness of gram-positive

β-lactams against S. pyogenes (Answer A is incorrect).

The role of IVIG in streptococcal necrotizing fasciitis is

controversial. A small randomized, placebo-controlled

trial – stratified on the basis of need for surgery and

clindamycin treatment – showed no improvement in

survival or reduction in the time to no further progression

of necrotizing fasciitis or cellulitis in 21 patients with

streptococcal toxic shock syndrome. As such, the

guidelines do not recommend IVIG until additional

studies are available (Answer D is incorrect).