Novel approach for rapid detection of extended spectrum β-lactamase and metalloid-β-lactamase using drug susceptibility testing microfluidic device (DSTM)

Abstract

Background/purpose: Rapid detection of β-lactamases is important in a recent situation where resistant bacteria are increasing. By using the drug susceptibility testing microfluidic device (DSTM), rapid screening of extended spectrum β-lactamases (ESBLs) and metallo-β-lactamases (MBLs) has become possible.

Methods: β-lactams and β-lactamase inhibitors were pre-fixed in the DSTM for use. A bacterial suspension in Mueller-Hinton broth (McF 0.25) was introduced into the device, and the effects of β-lactamase inhibitor on morphological changes caused by β-lactam were evaluated after 3 h incubation.

Results: Clinical isolates genetically confirmed to produce β-lactamase were used. Of the 84 ESBL-producing strains, 80 strains (95%) turned to be ESBL positive, and five strains (6%) of them MBL were positive as well as ESBL. Four strains (5%) were negative for both ESBL and MBL. Of the 24 MBL-producing strains, 23 strains (96%) were positive for MBL. All the 43 AmpC-producing strains were negative for both ESBL and MBL. Of the 156 ESBL- and MBL-nonproducing strains, 155 strains (99%) were negative for both ESBL and MBL, and one strain was positive for ESBL. With this method, the detection sensitivity was 95% and the specificity was 100% for ESBL, whereas the detection sensitivity was 96% and the specificity was 98% for MBL. These results were not significantly different from the results of the disc diffusion method.

Conclusion: The DSTM method allows rapid detection of β-lactamases in 3 h and may be a useful replacement for the disc diffusion method.

Keywords: Drug susceptibility testing microfluidic device; Extended spectrum β-lactamase; Metallo-β-lactamase; Screening rapid test.