Coagulase-negative staphylococci as nosocomial pathogens in neonates. The role of host defense, artificial devices, and bacterial hydrophobicity.

In contrast to the well-established pathogen Staphylococcus aureus, the coagulase-negative staphylococci--formerly collectively called Staphylococcus epidermidis--were until recently regarded as harmless commensals. During the last two decades, however, the coagulase-negative staphylococci have clearly emerged as pathogens in patients who have artificial devices implanted, such as prosthetic heart valves, hip prostheses, and cerebrospinal fluid shunts, and in those with compromised host defenses such as premature neonates, cancer patients, and transplant recipients. Recently, an increasing incidence of septicemia due to coagulase-negative staphylococci was detected in our neonatal intensive care unit. More than 90 percent of cases occurred in premature infants of low birth weight (less than 2,500 g). All septicemic infants were receiving intravenous therapy, and total parenteral nutrition solutions had been administered to nearly 80 percent just before or during the septic episode. This led us to examine the role of host defense factors in neonates and the possible significance of bacterial surface characteristics in the pathogenesis of catheter-associated infections.