Rapid Detection of Extended-Spectrum- -Lactamase-Producing Enterobacteriaceae from Urine Samples by Use of the ESBL NDP Test

From June to September 2012, 500 urine samples were recovered from patients with urinary tract infections (UTI) due to Gramnegative bacilli (>10 leukocytes/ml and >10 Gram-negative isolates/ml) who visited the University hospital Bicêtre (France). They were challenged with extended-spectrum-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E) using the rapid diagnostic ESBL NDP test. Results of the ESBL NDP test were compared to the results of the double-disc susceptibility test (DDST) performed on solid-agar plates and molecular identification of the -lactamase genes. Among the 450 nonduplicate urine samples, 11.3% were positive for ESBL-E by using the DDST, the ESBL determinants being mostly of the CTX-M type (CTX-M-15) according to molecular testing. Results of the ESBL NDP test were obtained within 15 min. The sensitivity and specificity of the ESBL NDP test were 98% and 99.8%, respectively, whereas the positive and negative predictive values of this test were 98% and 99.8%, respectively. A perfect correlation between cefotaxime resistance and positivity of the ESBL NDP test was observed. Therefore, the ESBL NDP test offers a powerful tool for a rapid identification of ESBL-E and associated resistance to expandedspectrum cephalosporins. It may be useful in particular for guiding first-line antibiotic therapy.