title: Methicillin-resistant Staphylococcus capitis with reduced vancomycin susceptibility causes late-onset sepsis in intensive care neonates.
abstract: BACKGROUND
  Coagulase-negative staphylococci, mainly Staphylococcus epidermidis, are the most frequent cause of late-onset sepsis (LOS) in the neonatal intensive care unit (NICU) setting. However, recent reports indicate that methicillin-resistant, vancomycin-heteroresistant Staphylococcus capitis could emerge as a significant pathogen in the NICU. We investigated the prevalence, clonality and vancomycin susceptibility of S. capitis isolated from the blood of NICU infants and compared these data to adult patients.
  
  
  RESULTS
  We conducted a retrospective laboratory-based survey of positive blood cultures in NICU infants ≥ 3 days of age (n = 527) and in adult ICU patients ≥ 18 years of age (n = 1473) who were hospitalized from 2004 to 2009 in two hospital centers in Lyon, France. S. capitis was the most frequent pathogen in NICU infants, ahead of S. epidermidis (39.1% vs. 23.5% of positive blood cultures, respectively). Conversely, S. capitis was rarely found in adult ICU patients (1.0%) compared to S. epidermidis (15.3%). S. capitis bloodstream isolates were more frequently resistant to methicillin when collected from NICU infants than from adult patients (95.6% vs. 53.3%, respectively). Furthermore, we collected and characterized 53 S. capitis bloodstream isolates from NICU infants and adult patients from six distant cities. All methicillin-resistant S. capitis isolates from NICU infants were clonally related as determined by pulsed-field gel electrophoresis. These isolates harbored a type V-related staphylococcal chromosomal cassette mec element, and constantly showed either vancomycin resistance (37.5%) or heteroresistance (62.5%). Conversely, the isolates that were collected outside of the NICU were genetically diverse and displayed much lower rates of vancomycin resistance and heteroresistance (7.7% and 23.1%, respectively).
  
  
  CONCLUSIONS
  A clonal population of methicillin-resistant S. capitis strains has spread into several French NICUs. These isolates exhibit reduced susceptibility to vancomycin, which is the most widely used antimicrobial agent in the NICU setting.
authors.affiliation: INSERM U851, National Reference Center for Staphylococci, University of Lyon, Lyon, France. jean-philippe.rasigade@chu-lyon.fr
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Rasigade
authors.forename: Olivia
authors.initials: O
authors.lastname: Raulin
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Picaud
authors.forename: Charlotte
authors.initials: C
authors.lastname: Tellini
authors.forename: Michele
authors.initials: M
authors.lastname: Bes
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Grando
authors.forename: Mohamed
authors.initials: M
authors.lastname: Ben Saïd
authors.forename: Olivier
authors.initials: O
authors.lastname: Claris
authors.forename: Jerome
authors.initials: J
authors.lastname: Etienne
authors.forename: Sylvestre
authors.initials: S
authors.lastname: Tigaud
authors.forename: Frederic
authors.initials: F
authors.lastname: Laurent
mesh_terms: D006801:Humans; D007231:Infant, Newborn; D015931:Intensive Care, Neonatal; D016106:Methicillin Resistance; D012189:Retrospective Studies; D018805:Sepsis / Q000209:etiology / Q000382:microbiology*; D013210:Staphylococcus / Q000187:drug effects* / Q000302:isolation & purification / Q000472:pathogenicity*; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D014640:Vancomycin