A STUDY OF THE EPIDEMIOLOGY OF AN ENDEMIC STRAIN OF STAPHYLOCOCCUS-HAEMOLYTICUS (TOR-35) IN A NEONATAL INTENSIVE-CARE UNIT

Coagulase-negative staphylococci (CNS) are among the most prevalent mi croorganisms that colonize and cause sepsis in neonatal intensive care units (NICU). We had previously identified a strain of CNS, Staphyloc occus haemolyticus (TOR-35), in the NICU at Mount Sinai Hospital, that had been repeatedly isolated from blood cultures from neonates. We th erefore carried out a prospective study to determine the frequency and time of colonization and the frequency of bacteremia in neonates over a 3.5 month period. This was accomplished by obtaining surface swabs within 1 h of birth and on days 3, 5, and 7 and by characterizing all blood culture isolates of CNS. We also determined what percentage of n eonatal CNS bacteremias were due to this strain, between Janary 1, 198 7 and December 31, 1990, by retrieving and typing all stock cultures o f CNS from that period. All isolates were typed by species identificat ion and antimicrobial susceptibility profile code. There were 76 (38%) neonates that became colonized with the TOR-35 strain at some time du ring their NICU stay. Lower birth weight was associated with colonizat ion (p < 0.001), as was lower gestational age (p < 0.001). Only 1 neon ate had a positive blood culture isolate for the TOR-35 strain during the prospective study. Of the 4 years of neonatal bacteremias that wer e studied retrospectively, there were 252 episodes of CNS bacteremia, of which 27 (11%) were due to the TOR-35 strain. The TOR-35 strain has become endemic in our NICU and appears to selectively colonize premat ure, low birth weight newborn infants, but only infrequently causes ba cteremia.