The Prospective Evaluation of Four
Convenient Methods for Detecting
MBLs in the Clinical Isolates
Dr. Veena. M,
Associate Professor, Department of Microbiology,
J.J.M. Medical College, Davangere,
Karnataka 577004 India.
Background: The emergence and the spread of metallo-beta-lactamases (MBLs) in non fermenters like Pseudomonas aeruginosa and the Acinetobacter spp has become a therapeutic challenge. In this study, the phenotypic confirmation of the MBL production was done by different methods.
Method: The isolates were screened for metallo-beta-lactamase production by using imipenem. All the imipenem resistant isolates were further subjected to a phenotypic confirmation by the combined disk method, the double disk synergy test and the modified Hodge test. The results were analyzed and tabulated.
Results: Of the total 200 isolates, 124(62%) were of P. aeruginosa and 76(38%) were of the Acinetobacter spp. Out of the 200 isolates, 28 (19(68%)- P. aeruginosa and 9(32%)- Acinetobacter isolates were found to be MBL producers by the combined disk test which used imipenem and EDTA , by the double disk synergy test and by the modified Hodge test. But the combined disk test which used ceftazidime detected only 25 out of the 28 MBLs.
Conclusion: The results of our study showed that the combined disk test which used imipenem, the double disk synergy test and the modified Hodge test, all had equal sensitivity. But when the ease of the performance and the interpretation of the results were considered cost effectively, the combined disk test was found to be a more feasible option than the other tests. Overall, these tests can be done easily as they are less laborious and are cost â€“ effective. Hence, the routine testing of the metallo beta-lactamase producers is of great value, in order to take measures to advocate a proper antibiotic policy and also to take effective steps for controlling their spread worldwide.