Role of RND efflux systems in the Brucella suis physiology

MARTÍN, F A; POSADAS, D. M.; O'CALLAGHAN, D; ZORREGUIETA, A

- Centro Cultural Parque de España - Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2006

SAIB

Drug effluxTransport processes by RND/MFP systems of the RND/MFP families are one of the main causes of antibiotic resistance and were also implicated in physiological process such as resistance to bile salts and steroid hormones or transport of N-acyl homoserine lactones.The roles of the RND-MFP systems in Brucella spp. remain unexplored. Genome analysis revealed the presence of two putative RND efflux pumps named bepE y bepG, with high homology to Escherichia coli AcrB (40%), each associated with genes encoding proteins from the MFP family (bepD and bepF). In order to understand the relevance of these transporters, both MFP/RND loci were amplified and cloned in a pBBR derivative vector and Brucella suis deletion mutants were constructed. Minimal inhibitory concentration using the agar dilution test showed that the B. suis ∆bepE mutant was significantly more sensitive to DOC, ethidium bromide and crystal violet. Furthermore, over expression of bepDE in B. suis increased resistance to the same drugs and also to SDS, ampicillin, tetracyclin, novobiocin and thiamphenicol. In contrast, resistance profiles remain unaltered when the bepFG locus was over expressed or deleted. Surprisingly, the B suis ∆bepG mutant was attenuated in the HeLa cells infection model while the B. suis ∆bepE remains virulent. These results show that both BepDE and BepFG efflux systems are functional and relevant in the  Brucella suis physiology.