Comparison of Meropenem MIC by E Test and VITEK 2 in Resistant Pseudomonas and Acinetobacter Isolates

P.aruginosa and A.baumannii have evolved causing serious infections especially in health care institutions. Most of them are multidrug resistant and even resistant to meropenem which is a broad spectrum beta lactam antimicrobial used for treatment of critical infections. Minimum inhibitory concentration (MIC) of an antibiotic is determined to decide on the specific treatment and several methods of detecting MIC are adopted. Routing conduction of such methods is cumbersome for clinical laboratories and currently introduced VITEK 2 automated method is an alternative. The aims of the study were,

-To compare the E test and VITEK 2 system for the susceptibility testing of resistant Pseudomonas aeruginosa and Acinetobacter baumannii for meropenem  and,

-To compare the effect of four carbapenem antibiotics on Pseudomonas aeruginosa and Acinetobacter baumannii. For that 75 P. aeruginosa and 25 A. baumanii were collected randomly from the collection of isolates at Princess Alexandra Hospital, Australia. E test and VITEK 2 MIC done for the each isolate according to the manufacturer’s instructions and the latest CLSI guidelines (June, 2010). VITEK-2 MICs corresponded closely with those obtained with the E test method. Categorical Agreement testing for both the organisms was 92% with no major errors and 08% minor error. We conclude that VITEK 2 is a reliable method to detect MIC in P. aeruginosa and A. baumanii. Meropenem MICs for A. baumannii with the VITEK 2 system usually follow pattern a very similar to P. aeruginosa. Doripenem sensitivity results can be extrapolated from meropenem. And ertapenem resistance to  P. aeruginosa and A. baumanii is confirmed.

DOI: http://dx.doi.org/10.4038/sljid.v2i1.3667

Sri Lankan Journal of Infectious Diseases Vol.2(1) 2012: 28-35