Coagulase-negative staphylococcal bacteremia in the changing neonatal intensive care unit population. Is there an epidemic?

A fivefold increase in the number of cases of nosocomial coagulase-negative staphylococcal bacteremia was investigated in a neonatal intensive care unit between 1975 and 1982. This apparent outbreak was not the result of increased isolation of coagulase-negative staphylococci from blood cultures nor an increased frequency with which blood cultures were obtained. Rather, it was attributable to a dramatic increase in the overall probability that a positive blood culture would be interpreted as "bacteremia" as opposed to a contaminant by both physicians and infection control staff. Specifically, there had been a 62.3% increase in neonatal intensive care unit bed use by very-low-birth-weight (less than 1000-g) infants between 1975 and 1982, and in both years, positive blood cultures were 3.8 times as likely to be perceived as clinically significant if obtained from such tiny infants. The growing number of very-low-birth-weight babies occupying neonatal intensive care unit beds, coupled with the observation that blood cultures positive for coagulase-negative staphylococci are almost four times as likely to be perceived as clinically significant if obtained from extremely premature infants, may account for the reported increase in nosocomial coagulase-negative staphylococcal bacteremia.