Study on the dissemination of the cluster in spp. reveals that the BcrAB transporter is sufficient to confer high-level bacitracin resistance

Renata Matos (1) , Vera Valadão Pinto (1) , Marta Ruivo (1) , Maria de Fátima Silva Lopes (1)

1 ITQB - Instituto de Tecnologia Química e Biológica António Xavier

Bacitracin is used both in clinical practice and as an animal growth promoter in some countries. Recent reports revealed the dissemination of high-level bacitracin resistance (HLBR) in the genus . The operon confers HLBR in an strain, and the presence of the regulator BcrR was stated as essential for this phenotype. Our objectives were to investigate the spread of the genes in the genus and to evaluate the role of this genotype in the HLBR phenotype. Fifty-eight enterococcal isolates from different environments and species were screened for the presence of the genes, and minimum inhibitory concentrations for bacitracin were determined. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to study the expression of bacitracin resistance genes in strains with HLBR following growth in the presence and absence of the antibiotic. The genotype was found associated with strains from clinical settings bearing a HLBR phenotype. The most disseminated mechanism of bacitracin resistance was the BcrAB ABC transporter, encoded by the genes. This transporter, which is constitutively expressed in the absence of , was sufficient to confer HLBR. Our findings stress the need for further evaluation of bacitracin resistance in this genus.

Mots clés: Enterococcus; Bacitracin; bcrABD operon; bcrR

Renata Matos, Vera Valadão Pinto, Marta Ruivo, Maria de Fátima Silva Lopes. Study on the dissemination of the cluster in spp. reveals that the BcrAB transporter is sufficient to confer high-level bacitracin resistance. International Journal of Antimicrobial Agents, 2009, 34 (2), pp.142. ⟨10.1016/j.ijantimicag.2009.02.008⟩. ⟨hal-00556333⟩