The Osmetech Microbial Analyzer (OMA) is an automated headspace analyzer fitted with a novel detector system consisting of an array of polymer sensors, each of which responds to different volatile organic compounds. The system can be used for screening clinical urine specimens for significant bacteriuria by sampling urine headspace and subjecting the output of the multiple-detector response to principal component analysis. The OMA readily distinguished artificially infected urine samples from sterile controls. The OMA was then used to analyze 534 unselected clinical urine specimens, of which 21.5% had significant bacteriuria (containing >10 5 CFU of bacteria/ml). The sensitivity and specificity of the OMA compared with conventional culture were 83.5 and 87.6%, respectively. The OMA is a promising automated system for the rapid routine screening of urine specimens, and further clinical trials are in progress.
We investigated the prevalence and role of efflux pump activity and possible drug influx resistance in ciprofloxacin susceptibility amongst 26 distinct clinical isolates of Klebsiella pneumoniae of varying ciprofloxacin susceptibilities and known quinolone resistance-determining region (QRDR) genotypes. Cellular [(14)C]ciprofloxacin accumulation patterns and the amount of cell-associated [(14)C]ciprofloxacin of mid-logarithmic phase cells were determined before and after challenging with the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Most isolates (24/26), and all with ciprofloxacin minimum inhibitory concentrations (MICs) >1 µg/ml, had efflux activity that could extrude up to 90% of cell-associated [(14)C]ciprofloxacin; none had significant influx resistance. In isolates with no QRDR mutations, efflux alone reduced ciprofloxacin susceptibility. In isolates with QRDR mutations, the efflux activity varied: in one isolate with no efflux activity, the most common fluoroquinolone resistance-causing QRDR mutation did not bring about clinically significant ciprofloxacin resistance; isolates with multiple mutations had high MICs and, usually, high levels of efflux activity. Fluoroquinolone efflux activity is much more common in clinical isolates of K. pneumoniae than previously reported and it can contribute to decreased ciprofloxacin susceptibility.
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