Sphygmomanometers and thermometers as potential fomites of Staphylococcus haemolyticus: biofilm formation in the presence of antibiotics

BACKGROUND The association between Staphylococcus haemolyticus and severe nosocomial infections is increasing. However, the extent to which fomites contribute to the dissemination of this pathogen through patients and hospital wards remains unknown. OBJECTIVES In the present study, sphygmomanometers and thermometers were evaluated as potential fomites of oxacillin-resistant S. haemolyticus (ORSH). The influence of oxacillin and vancomycin on biofilm formation by ORSH strains isolated from fomites was also investigated. METHODS The presence of ORSH on swabs taken from fomite surfaces in a Brazilian hospital was assessed using standard microbiological procedures. Antibiotic susceptibility profiles were determined by the disk diffusion method, and clonal distribution was assessed in pulsed-field gel electrophoresis (PFGE) assays. Minimum inhibitory concentrations (MICs) of oxacillin and vancomycin were evaluated via the broth microdilution method. Polymerase chain reaction (PCR) assays were performed to detect the mecA and icaAD genes. ORSH strains grown in media containing 1/4 MIC of vancomycin or oxacillin were investigated for slime production and biofilm formation on glass, polystyrene and polyurethane catheter surfaces. FINDINGS ORSH strains comprising five distinct PFGE types were isolated from sphygmomanometers (n = 5) and a thermometer (n = 1) used in intensive care units and surgical wards. ORSH strains isolated from fomites showed susceptibility to only linezolid and vancomycin and were characterised as multi-drug resistant (MDR). Slime production, biofilm formation and the survival of sessile bacteria differed and were independent of the presence of the icaAD and mecA genes, PFGE type and subtype. Vancomycin and oxacillin did not inhibit biofilm formation by vancomycin-susceptible ORSH strains on abiotic surfaces, including on the catheter surface. Enhanced biofilm formation was observed in some situations. Moreover, a sub-lethal dose of vancomycin induced biofilm formation by an ORSH strain on polystyrene. MAIN CONCLUSIONS Sphygmomanometers and thermometers are fomites for the transmission of ORSH. A sub-lethal dose of vancomycin may favor biofilm formation by ORSH on fomites and catheter surfaces.

Resistência aos antimicrobianos em estafilococos coagulase-negativa isolados de hemocultura / Antimicrobial resistance in coagulase-negative staphylococci isolated of hemocultura

Os estafilococos coagulase-negativa (ECNs) estão entre os microganismos que constituem a microbiota nor al da pele. O seu significado clínico como agente causal de várias infecções em pacientes com materiais implantados e outras infecções hospitalares tem aumentado nas últimas décadas. No presente estudo avaliou-se a resistência de 36 amostras de ECNs, isoladas de hemoculturas de pacientes internados em hospital público da cidade do Rio de Janeiro. As amostras revelaram um perfil de alta resistência às drogas do grupo betalactâmico, e o emprego da cefoxitina, em substituição à oxacilina, para indicação da presença do gene mecA e detecção da resistência a estas drogas, mostrou-se adequado. O perfil de alta resistência observado entre as amostras recomenda maior rigor e critério na seleção de drogas para o tratamento das infecções po ECNs.