Multidrug-resistant organisms (MDROs) present substantial clinical and financial burdens to patients and hospitals. In pediatric patients undergoing cancer or hematopoietic stem cell treatment, information is needed to characterize the frequency and type of MDRO colonization and clinical relevance. The objectives of this study were (1) to determine MDRO prevalence in a pediatric cancer and hematopoietic stem cell patient population and (2) to assess the performance of a rapid molecular MDRO detection system compared with standard culture and susceptibility testing.

This study was conducted among patients admitted to the oncology and blood and marrow transplant unit at Children’s National Medical Center in Washington, DC, from September 1 through November 30, 2013. A point prevalence study was conducted among patients in the unit on November 23, 2013. Patients were subsequently monitored through February 28, 2014, for presence of an invasive infection.

MDROs in this study included methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), extended-spectrum beta-lactamase–producing gram negatives (ESBLs), ¹ and carbapenem-resistant Enterobacteriaceae (CRE). ² The presence of MDROs was detected using both molecular analysis and traditional culture analysis. The molecular analysis included OpGen MRSA DNA Screening Test (OpGen) and Xpert MRSA assay (Cepheid) for MRSA and Acuitas MDRO Gene Test (OpGen) for VRE, ESBL, and CRE.

Twenty-eight patients, including 7 patients undergoing hematopoietic stem cell transplant, had consent to participate. Both the molecular analysis and culture analyses confirmed that none of the 28 patients had MRSA, VRE, ESBL, or CRE.

Twenty-two patients in the prevalence study provided 22 perianal specimens that underwent culture analysis first. If the growth occurred, isolates were identified to the species level and characterized by antimicrobial susceptibility testing and molecular analysis. The tests confirmed the presence of 3 VRE and 1 ESBL. CRE was not detected.

Combining the patients with a perianal specimen in the 2 populations, the VRE prevalence rate was 6.8% (3 of 44 patients; 95% CI, 1.4%–19.9%) and the ESBL prevalence rate was 2.3% (1 of 44 patients; 95% CI, 0.1%–12.7%). Colonization of MRSA or CRE was not found in this population. At the end of the follow-up period in February 2014, none of the 44 patients had developed an infection caused by a MDRO.

Children with cancer or hematopoietic stem cell transplant represent a population at high risk for drug-resistant organisms because they often have prolonged hospital stays and frequent exposure to empirical broad-spectrum antimicrobial therapy (eg, in the setting of fever with neutropenia or systemic sepsis). Despite great concern for resistant pathogens in this special population, to our knowledge, ours is the first study that describes the prevalence of the 4 most common MDROs in a single study.

We were encouraged by finding no patient colonized with MRSA. A small cohort of patients was colonized with VRE (n=3) or ESBL (n=1) organisms. These colonization rates were much lower than the rates previously reported in pediatricReference Ford, Lopansri and Haydoura ³ and adultReference Almyroudis, Lesse and Hahn ⁴ patients with malignant tumors in the United States and in international settings.Reference Vehreschild, Hamprecht and Peterson ^{5 ,} Reference Arnan, Gudiol and Calatayud ⁶

This study illustrated that the molecular screening tool Acuitas was accurate in excluding the presence of MDROs directly from perianal swabs or isolates. It holds great promise, particularly for detecting CRE genes. CRE remains uncommon; however, it has become an increasingly recognized cause of infection. ⁷ Detection of CRE in a healthcare institution often leads to immediate institution of heightened infection control measures. Hence, molecular tools for rapid detection of MDRO must be evaluated carefully to ensure they perform well in comparison with the existing gold standard of culture and susceptibility.

We found no correlation between MDRO colonization and subsequent likelihood of developing invasive infection with the colonizing organism. This highlights the fact that detection of MDRO colonization may impact isolation precautions while hospitalized but may not necessarily warrant changes in empirical clinical therapy in the setting of suspected infection.

This was a single-center study with a relative small sample size; we recognize that the low MDRO colonization rate in this study should be explored further in a larger study population. Colonization with MDRO pathogens did not predict likelihood or etiology of subsequent invasive infection.