title: Molecular and descriptive epidemiologyof multidrug-resistant Enterobacteriaceae in hospitalized infants.
abstract: OBJECTIVE
  To investigate the epidemiology of multidrug-resistant Enterobacteriaceae (MDRE) in hospitalized infants.
  
  
  METHODS
  From 2000 through 2005, active surveillance cultures for MDRE were performed for patients admitted to a 40-bed neonatal intensive care unit (NICU) that provides care for critically ill infants 6 months of age or younger. MDRE epidemiology and the genetic relatedness of MDRE strains determined by repetitive-sequence polymerase chain reaction were analyzed.
  
  
  RESULTS
  Active surveillance cultures revealed that 759 (23%) of 3,370 NICU infants (or approximately 1 in 5) developed MDRE colonization or infection and that 613 (72%) of the 853 isolates with epidemiologic data available were healthcare acquired. MDRE colonization occurred more frequently (in 653 infants [86%]) than did MDRE infection (in 106 [14%]). Of the 653 infants with MDRE colonization, 119 (18%) eventually became infected, with 29 (4%) acquiring sterile site infections. The most commonly isolated organisms were the Enterobacter species, accounting for 612 (71%) of the 862 isolates. Molecular epidemiologic analysis revealed that genetic-relatedness clustering (related clusters defined as having a genetic similarity coefficient greater than 95%) varied depending on microbial species. Clustering was detected for 36 (78%) of the 46 Enterobacter aerogenes isolates, 22 (45%) of the 49 Enterobacter cloacae isolates, and 13 (59%) of the 22 Klebsiella pneumoniae isolates.
  
  
  CONCLUSIONS
  Hospitalized infants are at significant risk of acquiring MDRE, specifically Enterobacter species, at the study institution. Active surveillance cultures identified colonized patients who likely contributed to the institutional reservoir of MDRE. Molecular epidemiologic studies suggest that both patient-to-patient transmission and de novo acquisition of resistance play a role in the acquisition of these organisms, and that the clinical significance of such acquisition varies by species. The high percentage of E. aerogenes isolates that demonstrated genetic clustering suggests that monitoring the prevalence of this organism could serve as a useful measure of compliance with infection control procedures.
authors.affiliation: George Washington University School of Medicine, Center for Health Services and Community Research, Washington, DC 20010, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Anderson
authors.forename: Sarah
authors.initials: S
authors.lastname: Nicholas
authors.forename: Bruce
authors.initials: B
authors.lastname: Sprague
authors.forename: Joseph
authors.initials: J
authors.lastname: Campos
authors.forename: Billie
authors.initials: B
authors.lastname: Short
authors.forename: Nalini
authors.initials: N
authors.lastname: Singh
mesh_terms: D003428:Cross Infection / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology; D004219:District of Columbia / Q000453:epidemiology; D024901:Drug Resistance, Multiple, Bacterial; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology; D006776:Hospitals, Pediatric; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D017053:Infection Control; D015931:Intensive Care, Neonatal; D017720:Molecular Epidemiology; D016133:Polymerase Chain Reaction; D015995:Prevalence; D018571:Sentinel Surveillance