RESUMO
Multiple strains of Acinetobacter baumannii have developed multidrug resistance (MDR), leaving colistin as the only effective treatment. The cecropin-α-melittin hybrid BP100 (KKLFKKILKYL-NH2) and its analogs have previously shown activity against a wide array of plant and human pathogens. In this study, we investigated the in vitro antibacterial activities of 18 BP100 analogs (four known and 14 new) against the MDR A. baumannii strain ATCC BAA-1605, as well as against a number of other clinically relevant human pathogens. Selected peptides were further evaluated against strains of A. baumannii that acquired resistance to colistin due to mutations of the lpxC, lpxD, pmrA, and pmrB genes. The novel analogue BP214 showed antimicrobial activity at 1 to 2 µM and a hemolytic 50% effective concentration (EC50) of >150 µM. The lower activity of its enantiomer suggests a dual, specific and nonspecific mode of action. Interestingly, colistin behaved antagonistically to BP214 when pmrAB and lpxC mutants were challenged.
Assuntos
Acinetobacter baumannii/efeitos dos fármacos , Antibacterianos/farmacologia , Farmacorresistência Bacteriana/efeitos dos fármacos , Oligopeptídeos/farmacologia , Acinetobacter baumannii/genética , Acinetobacter baumannii/metabolismo , Aciltransferases/genética , Aciltransferases/metabolismo , Amidoidrolases/genética , Amidoidrolases/metabolismo , Sequência de Aminoácidos , Antibacterianos/síntese química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Colistina/farmacologia , Farmacorresistência Bacteriana/genética , Eritrócitos/efeitos dos fármacos , Expressão Gênica , Hemólise/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Dados de Sequência Molecular , Mutação , Oligopeptídeos/síntese química , Técnicas de Síntese em Fase Sólida , Relação Estrutura-Atividade , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Interaction between pairs of Staphylococcus aureus replication proteins was detected in an Escherichia coli based two-hybrid analysis. A reverse two-hybrid system was constructed for selection of compounds that hindered interaction between interacting protein pairs. A number of cyclic peptides, from a library generated by the split intein-mediated circular ligation of peptides and proteins technology, were found to interfere with dimerization of the ß-sliding clamp of the replisome. Two 8-mer peptides were analyzed in more detail. Both inhibited DNA replication, led to SOS induction, altered cell morphology and cell death. The peptides were active when added to bacterial cultures indicating that they could traverse the bacterial membrane to find their intracellular target. Peptide specificity was confirmed by overproduction of the putative target (DnaN) which resulted in resistance. The minimum inhibitory concentration was â¼50 µg/ml for S. aureus cells. These compounds may serve as lead candidates for future development into novel classes of antibiotics as well as provide information on the function of the S. aureus replication process.
