Diffusion based methods versus automated mic in detecting drug resistance among nosocomial pathogens

ABSTRACT

The incidences ofnosocomial infections are varied in different studies, and the crude mortality is high, particularly for intensive-care unit [ICU] patients. The rates of antimicrobial resistance among pathogens causing health care-associated infections are increasing, and the main mechanisms that must be submitted to surveillance and accurate diagnosis are ESBL, AmpC and carbapenem resistance in gram negative bacilli, and MRSA and VRE in gram positive cocci. The aim of this study was to determine the incidence of the gram negative and gram positive resistance among nosocomial pathogens, to assess the abilities of diffusion based methods to detect different resistant patterns in relation to MIC profiles tested by the Sensititre automated system and to guide antimicrobial therapy policy in Benha locality. The study included total of 205 nosocomial specimens that were cultured and yielded 89 gram negative and 35 gram positive isolates. In our study we only included the nosocomial gram negative isolates resistant to 3rd generation cephalosporins [54] and the gram positive isolates resistant to vancomycin +/- methicillin [20] to be tested by Sensititre for identification and susceptibility testing. Diffusion based techniques used for confirmation of resistance of gram negative bacilli included ESBL screening by double disc diffusion test, imipenem [IMP]-EDTA combined disc test and ESBL and AmpC Detection Set [D68C system]