MRSA Colonization and Infection

Methicillin-Resistant Staphylococcus aureus Colonization and Its Association with Infection among Infants Hospitalized in Neonatal Intensive Care Units. Huang Y-C, et al Pediatrics 2006; Aug: 118(2):469-474. [Full text] [PDF]

OBJECTIVE. To assess the rate of methicillin-resistantStaphylococcus aureus colonization and its association withinfection among infants hospitalized in methicillin-resistantS aureus–endemic NICUs.

METHODS. Between March 2003 and February 2004, surveillancesurface culture specimens were obtained weekly from multiple sites of infants admitted to the NICUs at a children’shospital in Taiwan for the detection ofmethicillin-resistant S aureus. All colonized and clinical isolatesfrom each study infant with methicillin-resistant S aureus infectionwere genotyped with pulsed-field gel electrophoresis, with Sma1digestion, and compared.

RESULTS. A total of 783 infants were included in this study.Methicillin-resistant S aureus colonization was detected for323 infants during their NICU stays, with detection with thefirst 2 samples for 89%. Nares and umbilicus were the 2 mostcommon sites of initial colonization. Methicillin-resistantS aureus colonization was associated significantly with prematurebirth (

28 weeks) and low birth weight (

1500 g), and infantswith colonization had a significantly higher rate of methicillin-resistantS aureus infection, compared with those without colonization(26% vs. 2%). Methicillin-resistant S aureus colonization wasnoted for 84 of 92 infants with methicillin-resistant S aureusinfections. Of the 68 episodes with previous colonization andisolates available for genotyping analysis, colonized and clinicalisolates were indistinguishable in 63 episodes, highly relatedin 2 episodes, and distinct in 3 episodes.

CONCLUSIONS. More than 40% of the hospitalized infants werecolonized with methicillin-resistant S aureus during their stayin methicillin-resistant S aureus–endemic NICUs; thiswas associated significantly with methicillin-resistant S aureus infection. Most infants with methicillin-resistant S aureus infections had previous colonization with an indistinguishable strain.

Commentary: With the rise in community colonization rates of MRSA (or ORSA, for oxacillin-resistant Staph aureus), this organism has now emerged as a vexing and morbid pathogen in the NICU. After a couple of index cases of severe systemic ORSA infection in one of our NICUs about 2 years ago, we instituted infection control procedures that included isolation of all outborn infants (until proven ORSA-negative), weekly surveillance cultures of all NICU patients with bactoban treatment and isolation of positive patients, and cohorting of nursing staff as best as we were able. We have consulted on multiple occasions with the CDC. The result: we have “controlled” but have not eradicated ORSA

(our colonization rate varies between 2.5 and 20%). Of note in this study is the approximate 25% risk of systemic infection among infants colonized with ORSA, with the risk greatest among the most vulnerable infants. Although the bloodstream infection is typically cleared rapidly with vancomycin, soft tissue and bone/joint infections are difficult to treat because vancomycin (in contrast to nafcillin) has relatively poor penetrance into those compartments. It is most unfortunate that prophylactic treatment with Veronate® (human IVIG with enhanced anti-staphylococcal activity) was shown so unambiguously to be ineffective. The prevalence and morbidity of this organism has worked against efforts not to employ vancomycin as a first-line therapy when nosocomial sepsis is suspected. Perhaps as a consequence, we have begun to see intermittent VRE (vancomycin-resistant Enterococcus) colonization in our infants. The bugs are smart. Will the era of antibiotics as wonder drugs be a short one hundred year footnote in history? - MLH

You may add your own comments to the discussion of this topic by selecting : Submit Comments.