Utilizzo di Etest nell’antibiogramma diretto da emocoltura su bacilli Gram negativi a crescita rapida e Staphylococcus spp.

The objective of this study was to compare E test antibiotic gradient performed directly from positive blood coltures with Vitek 2 System for rapid susceptibility testing.A total of 47 strains of Gram negative rapid growers and 37 strains of Staphylococcus spp. (10 strains S. aureus and 27 coagulase negative) were investigated. Direct testing of susceptibility to amikacin, imipenem, piperacillin-tazobactam, and ciprofloxacin was evaluated for Gram negative strains, and to oxacillin,ofloxacin, and imipenem for Gram positive. The rate of correlation resulted 99.4% for Gram negative strains (187/188) and 97% for Gram positive strains (144/148).Major errors (i.e. reported as resistant by the Etest but shown to be sensible by the Vitek) were observed and regarding one strain of P. aeruginosa for imipenem and two strains of Staphylococcus coagulase negative for oxacillin and imipenem. Etest resulted useful for direct testing susceptibility from blood and may lead to cost reducttion.