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Delta toxin activity in coagulase-negative staphylococci from the bowels of neonates.

Department of Pediatrics, B.C.'s Children's Hospital, Vancouver, Canada.

ABSTRACT

Coagulase-negative staphylococci are prominent in stools of neonates in some intensive care units and have been associated with necrotizing enterocolitis. A plausible mediator of bowel damage is delta-like toxin, which is produced in vitro by most coagulase-negative staphylococci, but factors influencing the expression of toxin in the bowel are unknown. We examined 105 coagulase-negative staphylococcus isolates from stools of neonates by using an enzyme-linked immunosorbent assay and detected delta toxin production by 92 isolates (88%). The amount present in 18-h broth cultures varied over 100-fold, from 933 to 125,000 ng/ml. All broths positive by enzyme-linked immunosorbent assay except one caused hemolysis of human erythrocytes. The threshold concentration for consistent cytotoxicity to fibroblasts was greater than or equal to 24,000 ng/ml. Only 56% of Staphylococcus epidermidis isolates were capable of producing this much toxin, and these were more often obtained from premature infants in intensive care than from healthy full-term infants (P = 0.003) and were more often resistant to multiple antibiotics (P less than 0.001). Cultures grown anaerobically seldom caused hemolysis (4 positive of 29 tested; P less than 0.001) because potency of the toxin was decreased (at least ninefold for S. epidermidis isolates). We conclude that only a portion of the fecal coagulase-negative staphylococci tested produced enough delta toxin in vitro to be cytotoxic, that such isolates have accumulated in our intensive care nursery, and that development of toxin-mediated bowel injury may also require a favorable redox potential within the host bowel.

This article has been cited by other articles:

• Isaacs, D (2003). A ten year, multicentre study of coagulase negative staphylococcal infections in Australasian neonatal units. Arch. Dis. Child. Fetal Neonatal Ed. 88: F89-F93 [Abstract] [Full Text]