J. Clin. Microb.40:2520-2525, 2002
Department of Medical Microbiology and Infection Control,
VU University Medical Center, Amsterdam, The Netherlands.
A premature infant in a neonatal intensive care unit (NICU)
developed a bloodstream infection caused by coagulase-negative
staphylococci (CoNS) sensitive to vancomycin.
The infection persisted for 3 weeks, despite therapy with vancomycin
and replacement of all intravenous catheters.
The neonate died due to necrotizing enterocolitis which developed
during the ongoing sepsis. We screened this strain and 216 other strains
of CoNS from cultures of blood obtained from neonates between 1997 and
2000 for heteroresistance to vancomycin. Forty-eight isolates, including
the strain that caused ongoing sepsis, proved heteroresistant. All isolates
were identified as Staphylococcus capitis and were identical, just as their resistant stable subcolonies were, when they were genetically fingerprinted by amplified-fragment length polymorphism analysis. The heteroresistant phenotype of this endemic strain was confirmed by population analysis. We conclude that heteroresistance to vancomycin occurs in S. capitis and might be the cause of therapeutic failures in NICUs. Moreover, heteroresistant strains can become endemic in such units.