Coagulase-negative staphylococcal sepsis in neonates. Association between antibiotic resistance, biofilm formation and the host inflammatory response.

Background: Coagulase-negative staphylococci (CoNS) are the most prevalent pathogens causing late onset sepsis in neonates. They are often multiresistant to antibiotics, and the ability to form biofilm is considered their main virulence determinant.

Methods: During a 12-year period, we identified 150 neonates having 164 suspected septic episodes with growth of CoNS in blood culture. We examined the relationship between antibiotic resistance, phenotypic biofilm production and genetic determinants for biofilm formation in different CoNS species and their correlation with neonatal inflammatory response.

Results: Eighty-five episodes were classified as true sepsis, and 79 episodes of CoNS growth in blood culture were considered contaminations. Sixty-one percent of Staphylococcus epidermidis isolates produced biofilm compared with 26% of CoNS non-epidermidis (P < 0.001). We observed no difference in phenotypic biofilm production or genetic determinants for biofilm formation between invasive isolates and contaminants. C-reactive protein levels as a marker of inflammatory response were higher in CoNS sepsis caused by methicillin and aminoglycoside resistant versus susceptible isolates (P = 0.031). In contrast, there was a significant association between a lower C-reactive protein response and biofilm-positive isolates (P = 0.018). Antibiotic resistance was significantly correlated with biofilm production in S. epidermidis, but not in other CoNS species.

Conclusions: CoNS sepsis with biofilm-forming strains was associated with a decreased host inflammatory response, potentially limiting the immune system to counteract the infection. The impact of antibiotic resistance and virulence determinants on clinical outcome of neonatal CoNS sepsis warrants additional clinical studies.