Caracterização dos mecanismos de resistência à polimixina B em isolados clínicos de A. baumannii após a exposição in vitro à mesma e sua implicação na adesão e produção de biofilme

• Ano de defesa: 2016
• Autor(a) principal: Carneiro, Talita Barone [UNIFESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo (UNIFESP)
• Palavras-chave em Português: Resistência às polimixinas; Acinetobacter baumannii; Biofilme; Virulência
• Link de acesso: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=4987353; http://repositorio.unifesp.br/handle/11600/47713

Acinetobacter baumannii is one of the most common pathogens causing serious infections in hospitalized patients. These microorganisms have high ability to adapt to the hospital environmental, and acquire resistance to almost all available antimicrobials. The polymyxins are the last therapeutic options for treatment of these infections. We evaluated the mechanism of resistance and biofilm production among A. baumannii clinical isolates after in vitro exposition to polymyxin B, after 10 consecutive days, using increased concentrations of polymyxin B sulfate. pmrCAB and lpxACD genes, related with polymyxins resistance and ompA, csuE and pgaC genes, involved with the biofilm production were analyzed by nucleotide sequencing and qRT-PCR. Potential Zeta of bacterials membrane and biofilm quantification in microtiter plates were also evaluated. The exposition of A. baumannii clinical isolates to polymyxin B resulted in polymyxin B resistance in all tested isolates, and led to the reduction of MICs to other tested antimicrobials, except for minociclin. Five isolates had mutations in the pmrB and 3 isolates in the lpxC genes, after polymyxin B exposition. One isolate had pmrB and lpxC mutations concomitantly. The relative transcription rates were reduced for pmrB, while they were increased for lpxC after most isolates after polymyxin B exposition. In contrast, no significant differences in the membrane zeta potencial and biofilm quantification were noticed. All isolates had the ompA and most isolates (12) had csuE transcriptional levels increased. In addition, 11 isolates had elevation in the pgaC transcription rates after polymyxin B exposition. Our study illustrates the complexity of mechanisms leading to polymyxin resistance because in most isolates the mechanism remained undetermined. Although changes in the outer membrane permeability might have occurred after polymyxin B exposure, they were not significant enough to reduce the negative electric charge of the outer membrane or biofilm production by A. baumannii resistant to polymyxin B.