Análise de tolerância e persitência de Staphylococcus aureus induzidos por vancomicina
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Data
2019-08-26
Autores
Birro, Jessica de Cassia Teixeira
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Universidade Federal do Espírito Santo
Resumo
Introduction: Staphylococcus aureus lineages with reduced susceptibility to vancomycin (VAN) gained attention researchers due to it relation between therapeutic fails and recalcitrance. Microbial survival strategies are denominated tolerance and persistence, they are able to change transiently the metabolism of a sub population exposes to bactericidal antibiotics. So, in this study we investigated if different concentrations of vancomycin are able to induced tolerance or persistence in S. aureus. Materials and methods: Five lineages of S. aureus were intermittently exposed to 10 µg/mL of VAN by 6 h. They were selected derivative lineages of ATCC 29213 (parental), E10.6 and E100, to continue the assays. They were confirmed the purity of derivative lineages by MALDI-TOF MS and similarity genetic by PFGE. After, they were characterized tolerance/persistence from susceptibility by minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) for VAN and modified disk difusion test with VAN, oxacillin (OXA) and ciprofloxacin (CIP). Those assays were confirmed by time-kill curve with 50 µg/mL of VAN and, in the end, they analysed the phenotypic changes in growth taxa, autolysis percentual in Triton X-100, TBARS levels and Zeta potential. Results: All lineages did not change the viable cells quantitative when exposes to 10 µg/mL of VAN. For ATCC 29213, even though 100 µg/mL of VAN were sufficient to erradicate the population. No one derivative lineage changes in the susceptibility, but MBC/MIC ratio was smaller than 32 for all lineages. The parental lineage and it derivatives E10.6 and E100 showed high level to tolerance/persistence for OXA and CIP (p > 0,05), although this assay was not viable to VAN. In 6 h, E10.6 lineage showed the same MDK99 than parental lineage, being equal to 3 h in exponential phase and to 6 h in stacionary phase. In contrast, for both lineages the MDK99,99 was 6 h in exponential phase and bigger than 6 h in stacionary phase. Little changes in adpatative phase were observed only in 0,25 µg/mL and 0,5 µg/mL of VAN. From of 1 µg/mL of VAN it was not observed growth. TBARS levels were increased for the treated group with VAN, as well as the autolysis percentuals, while the membrane superficial charge has became more negative (p > 0,05 for all). Conclusions: The treatment with diferentes concentrations of VAN do not change viable counting, as well as do not change the tolerance/persistence levels for VAN, OXA and CIP. Although, it is able to increase the lipidic peroxidation levels and autolysis percentual, while reduce the surface charge in parental and derivative lineages.
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Microbiologia , Agentes antiinfecciosos , Testes de sensibilidade bacteriana , Bactérias gram-positivas , Staphylococcus aureus , Vancomicina , Persistência a
antimicrobianos , Vancomycin , Microbial survival , Antibiotic persistence