The Multidrug-Resistant Pseudomonas aeruginosa Clinical Isolates from Dogs and Cats Expressed Three Multidrug Efflux Systems Simultaneously

The objective of this study was to examine the expression of 4 clinically-important Mex systems including MexAB-OprM, MexCD-OprJ, MexEF-OprN and MexXY in the Pseudomonas aeruginosa clinical isolates from dogs and cats. The isolates exhibited high level of resistance to multiple antibiotics clinically important. All of them simultaneously overexpressed up to three different Mex systems, including MexAB-OprM, MexEF-OprN and MexXY as determined by RT-PCR. None of the isolates overexpressed MexCD-OprJ. Expression of mexF was measured by using quantitative real-time RT-PCR. Transcription level of mexF varied (i.e. 4-219 fold) but was at least 4 fold higher than that of PAO1. DNA sequence analysis of mexT suggested the existence of uncharacterized regulatory mechanism (s) of MexEF-OprN expression besides MexT. The results underscored the contribution of Mex systems in multidrug resistance phenotype of the P. aeruginosa clinical isolates from dogs and cats.