​biomerieux-diagnostics.​com). For all of these tests, based on the results obtained, the bacteria are classified

as susceptible, intermediate or resistant to the www.selleckchem.com/products/verubecestat.html tested antimicrobial agent using breakpoints, i.e. threshold values put forth by the Clinical and Laboratory Standards Institute (CLSI) or other regulatory authorities [41, 42]. These methods rely on growth of bacteria, hence are time-consuming and unable to provide information to guide antibiotic administration until about 24 h after a pathogen has been isolated. They may also prove to be imprecise in antibiotic susceptibility prediction in case of selleck products resistant bacteria, especially in context of β-lactamase producers [44, 45]. This is because even if the presence of a resistance factor results in altered MICs or BI 2536 in vivo disk diffusion diameters, interpretation can remain unaffected, as breakpoints may not be reached [46, 47]. To address this issue, the CLSI regularly puts forth revised breakpoints and updates and often recommends additional testing, such as determination of specific resistance mechanisms (e.g. β-lactamase production) [41, 42]. Also at times repeated testing may be needed, such as in cases of serious infections

requiring penicillin therapy, the CLSI guidelines recommend repeated MIC and β-lactamase testing on all subsequent isolates from patients [41, 48]. Given these challenges, new methodologies Thalidomide that can provide timely bacterial resistance and/or antibiotic susceptibility information, such as that developed in our study, would be valuable. In this study we describe a rapid optical method (~60 min) for β-lactamase detection and assessing activity of β-lactam antibiotics in presence of respective β-lactamase (β-lactamase based antibiotic activity). The antibiotic activity may also be interpreted more broadly as antibiotic susceptibility (β-lactamase based antibiotic susceptibility). We have developed a fluorescent molecular probe β-LEAF [β-Lactamase Enzyme Activated

Fluorophore (described as β-LEAP in earlier publications)], based on fluorophore quenching-dequenching, for rapid detection and characterization of β-lactamases [49, 50]. Although β-lactamase is widely employed as a reporter system for gene expression using fluorescent probes ([51–54] and (http://​http:​/​www.​invitrogen.​com)), this approach is novel in that it also incorporates assessment to predict the most active β-lactam antibiotic among tested antibiotics, against given bacteria. In a previous report we demonstrated the principle using ATCC strains with known β-lactamase production for rapid functional definition of Extended Spectrum β-Lactamases [50]. In the current study we tested the approach with a panel of MSSA clinical isolates, to determine β-lactamase production and predict the activity of tested β-lactam antibiotic(s), in a rapid assay.