The outer membrane factor of Brucella suis is involved in resistance to antimicrobial compounds and virulence

DIANA POSADAS, FERNANDO MARTIN, JULIA SABIO GARCÍA, JUAN M. SPERA, SILVI CRAVERO, ANGELES ZORREGUIETA

Congreso; Tercer Congreso Argentino de Microbiología General (SAMIGE); 2006

Brucella spp., like other pathogens, must cope with the environment of diverse host niches during the infection process. In doing this, pathogens evolved different type of transport systems to help them survive and disseminate within the host. Members of the Outer Memrane Factor (OMF) in association with two inner-membrane proteins were shown to be involved in the export of chemically diverse molecules ranging from large protein toxins to small toxic compounds. The role of this family in Brucella and other alphaproteobacteria was little explored. The gene encoding the unique Brucella suis OMF protein (Bep) was cloned and expressed in a mutant of E.coli disrupted in the gene encoding the OMF component TolC that has a peculiarity to be involved in diverse transport functions. Bep fully complemented the resistance to drugs such as chloramphenicol and acriflavine but was incapable to restore hemolysin secretion in the tolC mutant of E.coli. An insertional mutation in the bep gene strongly affected the resistance phenotype of B.suis to bile salts and toxic compounds like ethidium bromide and rhodamine and significantly decreased the resistance to antibiotics such as erythromycin, ampicilin, tetracyclin and norfloxacin. Moreover, the bep mutant of B.suis was attenuated in the mice model. Taking together, these results suggest that in B.suis, effllux processes of toxic compounds that are Bep dependent contribute to survival inside the host.