Persistence of clones of coagulase-negative staphylococci among premature neonates in neonatal intensive care units: two-center study of bacterial genotyping and patient risk factors
From 1 January 1995 until 1 January 1996, we studied the molecular
epidemiology of blood isolates of coagulase-negative staphylococci (CoNS)
in the Neonatal Intensive Care Units (NICUs) of the Sophia Children's
Hospital (SCH; Rotterdam, The Netherlands) and the Wilhelmina Children's
Hospital (WCH; Utrecht, The Netherlands). The main goal of the present
study was to detect putatively endemic clones of CoNS persisting in these
NICUs. Pulsed-field gel electrophoresis was used to detect the possible
presence of endemic clones of clinical significance. In addition, clinical
data of patients in the SCH were analyzed retrospectively to identify risk
factors for the acquisition of positive blood cultures. In both centers,
endemic CoNS clones were persistently present. Thirty-three percent of the
bacterial isolates derived from blood cultures in the SCH belonged to a
single genotype. In the WCH, 45% of all bacterial strains belonged to a
single clone. These clones were clearly different from each other, which
implies that site specificity is involved. Interestingly, we observe that
the clonal type in the SCH differed significantly from the incidentally
occurring strains with respect to both the average pH and partial CO2
pressure of the patient's blood at the time of bacterial culture. We found
that the use of intravascular catheters, low gestational age, and a long
hospital stay were important risk factors for the development of a
putative CoNS infection. When the antibiotic susceptibility of the
bacterial isolates was assessed, a clear correlation between the nature of
the antibiotics most frequently used as a first line of defense versus the
resistance profile was observed. We conclude that the intensive use of
antibiotics in an NICU setting with highly susceptible patients causes
selection of multiresistant clones of CoNS which subsequently become
endemic