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Abstract
A single point study was conducted to determine which surface sites best represent the density and composition of the coagulase-negative staphylococcal (CNS) colonizing flora in premature neonates. Five different surface sites of six randomly selected neonates hospitalized in a neonatal intensive care unit (NICU) for a month were examined. The individual strains and their clonal organization within CNS species were identified using restriction endonuclease fingerprinting of whole chromosomal DNA and ribosomal RNA genes. Cultures of the scalp, umbilicus, foot, nose and rectum were collected and quantitatively processed. Ten colonies were typed per surface culture. The most dense CNS colonization was noted on the umbilicus (mean 1·2 × 104 c.f.u. cm−2), foot (mean 1·6 × 103 c.f.u. cm−2) and nose (mean 1·7 × 103 c.f.u. cm−2) of NICU neonates. Scalp and rectum were scarcely colonized. Of all the CNS surface isolates, S. epidermidis accounted for 77·7% (219/282) and S. haemolyticus, S. warneri and S. capitis accounted for 20·6% (58/282), 1·4% (4/282) and 0·4% (1/282), respectively. Colonization of each surface site comprised a maximum of five different strains representing four CNS species. Overall, five clones of S. epidermidis, two of S. haemolyticus, one of S. warneri and one of S. capitis were noted among the 282 isolates. The most predominant were two clones of S. epidermidis and one of S. haemolyticus; they accounted for 94% (265/282). Cultures from the foot and scalp represented the most heterogeneous CNS colonization of the five sites examined. Based on our findings of the existence of multiple strains of CNS at individual surface sites of NICU patients, we concluded that a minimum of five isolates be examined per surface culture to provide a comprehensive overview of the CNS colonizing flora.
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