2014 Update on infectious disease

This year I focus on four interesting and clinically relevant studies:

• an article by Huang and colleagues addressing the important issue of how best to reduce the frequency of methicillin-resistant Staphylococcus aureus (MRSA) infection in critically ill patients hospitalized in the intensive care unit (ICU)
• a study by Duggal and colleagues assessing the value of perioperative oxygen ­supplementation to reduce the frequency of postcesarean infection
• an investigation of diagnostic criteria for urinary tract infection (UTI) by Hooton and colleagues
• an exploration of the association between intra-amniotic inflammation, as distinct from bacterial colonization, and adverse fetal outcomes.

For ICU patients, universal decolonization reduces nosocomial infection more than targeted decolonization

Huang SS, Septimus E, Kleinman K, et al. Targeted versus universal decolonization to prevent ICU infection. N Engl J Med. 2013;368(24):2255–2265.

Infection in general, and nosocomial infection in particular, is common among patients hospitalized in the ICU. Such patients often are severely immunosuppressed and debilitated. They are likely to have multiple indwelling catheters and to require mechanical ventilation—interventions that predispose to life-threatening infection. The longer the duration of care in the ICU, the greater the risk of infection, especially infection caused by organisms that have acquired resistance to multiple antibiotics.

In this cluster-randomized trial, Huang and colleagues compared targeted and universal decolonization of patients treated in an ICU to determine which approach was more effective at preventing nosocomial infection, particularly MRSA infection. They found universal decolonization to be superior to targeted decolonization in reducing these infections.

Details of the studyInvestigators conducted their study in 74 ICUs in 43 hospitals. Each hospital was ­randomly assigned to one of three interventions:

• Group 1: MRSA screening followed by isolation of colonized patients
• Group 2: MRSA screening followed by isolation and decolonization of MRSA carriers
• Group 3: Universal decolonization (no screening).

The decolonization regimen consisted of twice-daily administration of intranasal mupirocin for 5 days and daily bathing with chlorhexidine-impregnated cloths for the duration of the ICU stay.

The study’s two endpoints were 1) the modeled hazard ratios for MRSA clinical isolates and 2) the hazard ratios for bloodstream infection with any pathogen.

During the intervention period, fewer MRSA isolates were found in the universal decolonization group, compared with the other two groups (P<.01). In addition, the number of bloodstream infections in the universal decolonization group was significantly lower than in the other two groups (P<.001). Fifty-four patients (number needed to treat) needed to undergo decolonization to prevent one bloodstream infection.

What this EVIDENCE means for practiceThe relevance of this investigation for those of us in the field of obstetrics and gynecology is simple and clear: If we have to transfer a patient to an ICU (such as an HIV-infected patient with a serious post­cesarean infection, or an oncology patient with a badly infected surgical wound), she should immediately be started on a regimen of twice-daily nasal mupirocin and daily bathing with chlorhexidine. This straightforward intervention will be of great value in reducing the incidence of bacteremia caused by a particularly dangerous pathogen.

Related article: Update on infectious disease. Patrick Duff, MD (July 2013)

The jury is still out on supplemental oxygen to reduce surgical site infection

Duggal N, Poddatorri V, Noroozkhani S, Siddik-Ahman RI, Caughey AB. Perioperative oxygen supplementation and surgical site infection after cesarean delivery. Obstet Gynecol. 2013;122(1):79–84.

In a widely read study published in 2000 in the New England Journal of Medicine, Greif and colleagues demonstrated that, in patients undergoing colorectal surgery, the rate of postoperative wound infection was significantly reduced from 11.2% in patients given 30% supplemental oxygen during surgery to 5.2% in those given 80% supplemental oxygen.¹ The oxygen was continued for 2 hours after surgery.

In a later study among general surgery patients, Pryor and colleagues were unable to replicate this finding.² It was in this setting that Duggal and colleagues undertook their investigation among women undergoing cesarean delivery. These investigators, too, were unable to replicate the 2000 finding of Greif and colleagues.

Related article: Update: Infectious Disease. Patrick Duff, MD (June 2012)

Details of the studyOver 4 years, from 2006 to 2010, Duggal and colleagues conducted a prospective, randomized, double-blinded controlled trial among patients undergoing scheduled, urgent, or emergent cesarean delivery. All patients were given prophylactic antibiotics, usually cefazolin 2 g intravenously after the infant’s umbilical cord was clamped. Surgical technique was reasonably well standardized and included closure of the deep subcutaneous layer of tissue using 2-0 plain gut sutures.

Patients were randomly assigned to receive supplemental oxygen via face mask, at 30% or 80% concentration, during surgery and for 1 hour postoperatively. They were evaluated postoperatively at 2 and 6 weeks. The primary outcome measure was a composite of surgical site infection, endometritis, or both.