Ocorrência e caracterização de Estafilococos coagulase negativos isolados de recémnascidos com bacteremias em unidade de terapia intensiva neonatal no HUPE-UERJ

Abstract

Coagulase-negative staphylococci (CNS) are often involved in nosocomial infections associated with catheters and other invasive medical procedures. The ability to adhere to abiotic surfaces and produce biofilms has been recognized among the major virulence factors of the SCN, especially Staphylococcus epidermidis, the main species responsible for infections related to health care - IRASs.Among the other species capable of producing biofilm, Staphylococcus haemolyticus has been associated with cases of infections in neonates.Here in, we investigated the microbiological and epidemiological aspects of invasive infections related to CNS in the neonatal intensive care unit (NICU) of a university hospital located at Rio de Janeiro metropolitan area (2008-2010).PCR multiplex-mPCR was used in the determination of the species of 40 CNS strains isolated from blood cultures of neonates making use of intravenous catheters and subjected to empirical antimicrobial therapy with vancomycin and / or gentamicin.Phenotyping was performed by three different methods: Simplified scheme in microplates, Vitek 2 and API-Staph. Antimicrobial resistance profiles were verified by the disk diffusion test, oxacillin MIC determinationand PCR for mecA gene. Evaluation of biofilm production was performed by PCR for genes icaAB, atlE and aap and the tests on Congo Red Agar plates and abiotic surfaces (polystyrene and glass).Clonality was determined by PFGE technique. Data revealed the isolation of S. haemolyticus (77%), S. epidermidis (15%), S. captis (5%) and S. warneri (3%).The comparative analysis of the results obtained by mPCR and phenotypic methods showed 97.5% concordance with the simplified scheme and ~40% with the Vitek 2 and API Staph systems. Different multidrug resistance profiles to 16 antimicrobials, including resistance to oxacillin was observed for 82.5% of the CNS isolates, although the mecA gene was not detected in 25% of these strains.Although most of the CNS isolates showed the ability to produce slime and/or biofilm, a complete correlation with the presence of mecA, icaAB, aap, atlE genes was not observed, emphasizing the multifactorial nature of biofilm production of SCN.Different from other CNS species, some strains of S. haemolyticus were unable to adhere to glass and polystyrene surfaces and/or to exhibit aap (38.7%), atlE (42%), icaAB (71%) genes. PFGE analysis revealed the presence of six different clonal types of the prevalent species, indicating the dissemination in this hospital and endemicity in our community of S. haemolyticus.