Staphylococcus aureus Infections in Pediatric Oncology Patients

High Rates of Antimicrobial Resistance, Antiseptic Tolerance and Complications

J. Chase McNeil, MD; Kristina G. Hulten, PhD; Sheldon L. Kaplan, MD; Donald H. Mahoney, MD; Edward O. Mason, PhD

Disclosures

Pediatr Infect Dis J. 2013;32(2):124-128. 

In This Article

Introduction

Background: Patients with malignancies represent a population at high risk for drug-resistant infections. We sought to determine the clinical spectrum and molecular epidemiology of Staphylococcus aureus infections in pediatric oncology patients followed at Texas Children's Hospital (Houston, TX). Furthermore, we determined the prevalence of the chlorhexidine resistance gene qacA/B from isolates in this unique population.

Methods: Patients with a history of malignancy and a culture-proven S. aureus infection were identified from 2001 to 2011. Antibiotic susceptibility, pulsed-field gel electrophoresis and detection of qacA/B by polymerase chain reaction were performed on all isolates. Medical records for all patients were reviewed.

Results: During the study period, 213 isolates were identified from 179 patients with malignancies. Thirty-one percent of the isolates were methicillin-resistant S. aureus. The most common infectious diagnosis was bacteremia (85/213 [39.9%], with 72/85 [84.7%] being catheter-associated). Thirteen patients with bacteremia were found to have pulmonary nodules at the time of presentation; only S. aureus was found in tissue in 5 of the 6 patients who underwent lung biopsy. After 2007, 18.2% of isolates were qacA/B positive with a steady increase in prevalence every year (χ2 for trend P = 0.04).

Conclusions: S. aureus is a significant cause of morbidity and mortality in pediatric oncology patients at Texas Children's Hospital. In addition to the more well-known clinical manifestations, this pathogen can also be associated with pulmonary nodules. Furthermore, the prevalence of S. aureus isolates carrying antiseptic resistance genes increased in this population. Additional clinical and molecular studies and surveillance among pediatric oncology patients are warranted to further explore these findings.

Children with malignancies represent a population at high risk for drug-resistant infections due to immune dysfunction, high rates of empiric antimicrobial prescription and exposure to antiseptic agents. Staphylococcus aureus represents one of the most common causes of bacteremia and febrile neutropenia in this patient population accounting for 9–13% of all cases.[1–4] Moreover, S. aureus was the most common cause of infectious death among children with febrile neutropenia in 1 series.[5]

Rates of colonization and infection with methicillin-resistant S. aureus (MRSA) have increased among pediatric oncology patients. The rates of colonization with MRSA have increased from <1% to 3.8% over a 7-year period at 1 center.[6] This is concerning in that many strains of MRSA, in particular the USA300 pulsotype, are associated with increased rates of complications in otherwise healthy individuals.[7,8] Although it is known that S. aureus infections are prevalent among children with cancer, there are little specific data regarding the epidemiology, risk factors and morbidity of S. aureus infections in this very vulnerable population.

Oncology patients frequently have exposure to the antiseptic chlorhexidine, an agent used in the care of central venous lines,[9] oral hygiene,[10,11] decolonization protocols[12] and decontamination of hospital surfaces. The use of chlorhexidine has been associated with decreased incidence of hospital-acquired infections among adult patients.[13–16] Despite this potential benefit, a number of genes encoding efflux pumps have been described in S. aureus conferring elevated minimum inhibitory concentrations and minimum bactericidal concentrations to chlorhexidine and other antiseptics, greatly diminishing their bactericidal activity.[17,18] Among the most prominent in this group is the qacA/B gene complex.[17,19] To date, there are only 2 studies of qacA/B-positive S. aureus isolates from adults in the United States[20,21] revealing a prevalence of approximately 1%; there are no studies in a pediatric population.

We sought to determine the clinical and molecular epidemiology of S. aureus infections among pediatric oncology patients followed at the Texas Children's Hospital Cancer Center (TCCC; Houston, TX) as well as focus on the outcomes and potential complications of these infections. In addition, we screened all identified isolates for the presence of qacA/B.

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