Comparison of double disk synergy test, VITEK 2 and Check-MDR CT102 for detection of ESBL producing isolates

Abstract

Objective. This study is to define the statistical significance for detection of ESBL producers by the double disk synergy test and molecular test (Check-MDR CT102), microdilution test (VITEK 2 with AES) and double disk synergy test (DDST), as well as the microdilution test and molecular test. Materials and methods. Phenotypic testing of 55 isolates Enterobacteriaceae (Escherichia coli (14/55), Klebsiella pneumoniae (34/55), Klebsiella oxytoca (3/55) and Proteus mirabilis (4/55) was performed by VITEK 2 Compact/AES. When this test showed positive results for the ESBL phenotype, then DDST with amoxicillin/clavulanate, ceftazidime, cefpodoxime, aztreonam, ceftriaxone and cefoxitin disks was performed along with Check-MDR CT102 which identified CTX-M, TEM and SHV β-lactamases. Results. Applying the McNemar test, we determined that there was a statistically significant difference in the results of detection of ESBLs bacteria using DDST compared to molecular methods (95% CI=41.92 to 54.55; p<0.0001), as well as a DDST and VITEK 2/AES (95% CI=40.13 to 52.73; p<0.0001). We did not find any statistically significant difference in the results of detection of ESBL producers using molecular techniques and VITEK 2/AES (CI=-4,43 to 5,36; p=1). Also we did not find any statistical.. difference between the resistance to cefpodoxime and ceftriaxone (50/50) compared to the results of molecular tests. Conclusion. In routine daily testing, good detection of ESBLs bacteria, especially CTX-M can be obtained with phenotypic methods with VITEK 2/AES and by DDST with cefpodoxime, and ceftriaksone disks.