Predicting Antibiotic Resistance in Gram-negative Bacilli from Resistance Genes [Mechanisms of Resistance]

We developed a rapid high throughput polymerase chain reaction (PCR) test and evaluated highly antibiotic-resistant clinical isolates of Escherichia coli (n=2919), Klebsiella pneumoniae (1974), Proteus mirabilis (1150) and Pseudomonas aeruginosa (1484) for several antibiotic resistance genes for comparison with phenotypic resistance across penicillins, cephalosporins, carbapenems, aminoglycosides, trimethoprim-sulfamethoxazole, fluoroquinolones and macrolides. The isolates originated from hospitals in North America (34%), Europe (23%), Asia (13%), South America (12%), Africa (7%), Oceania (1%) or unknown (9%). We developed statistical methods to predict phenotypic resistance from resistance genes for 49 antibiotic/organism combinations, including gentamicin, tobramycin, ciprofloxacin, levofloxacin, trimethoprim/sulfamethoxazole, ertapenem, imipenem, cefazolin, cefepime, cefotaxime, ceftazidime, ceftriaxone, ampicillin and aztreonam. Average positive predictive values for genotypic prediction of phenotypic resistance was E. coli (91%), K. pneumoniae (93%), P. mirabilis (87%) and P. aeruginosa (92%) across the various antibiotics for this highly resistant cohort of bacterial isolates.

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