Search

The global spread of multidrug-resistant strains has prompted the scientific community to explore novel sources of chemicals with antimicrobial activity. The aim of the study was to examine the antimicrobial activity in vitro of 28 extracts against carbapenem-producing Klebsiella pneumoniae, individually and in combination with antibiotics and in vivo toxicological assessment of the most active product. The multi-resistant K. pneumoniae strain was submitted for phenotypic and molecular characterization. The antibacterial activity of 28 plant extracts was evaluated alone and in combination with antibiotics against this strain through the agar disk diffusion. Of these, 16 extracts showed synergism against carbapenem-producing K. pneumoniae, being that B. crassifolia extract exhibited synergism with three antibiotics. Based on this assessment, B. crassifolia-extract-induced toxicity on Swiss male mice was evaluated by administering this extract and subsequently determining apoptosis and splenic phagocytosis using the comet and micronucleus assays. The results of this study showed that B. crassifolia extract had synergistic activity promising and groups treated with B. crassifolia exhibited no genotoxic or mutagenic activity, indicating that B. crassifolia extract exerted beneficial effects and appeared safe to use at the studied concentrations.

Submitted by Alison Souza (alisonsouza@ufgd.edu.br) on 2019-03-28T22:09:12Z No. of bitstreams: 1 NathalieGaeblerVasconcelos.pdf: 3217011 bytes, checksum: fdb74bd01fd7a41ff39b89979b3a05cc (MD5) Made available in DSpace on 2019-03-28T22:09:12Z (GMT). No. of bitstreams: 1 NathalieGaeblerVasconcelos.pdf: 3217011 bytes, checksum: fdb74bd01fd7a41ff39b89979b3a05cc (MD5) Previous issue date: 2018-09-11 Introdução: O surgimento da multirresistência bacteriana é um problema de saúde pública que resulta na necessidade de explorar novas opções terapêuticas. Há uma grande variedade de alvos antibacterianos não utilizados pelos fármacos atuais para serem explorados. O objetivo do presente estudo foi investigar a atividade antibacteriana do óleo essencial de Cinnamomum cassia L. (CCeo) sozinho e em combinação com polimixina B (POL) contra bactérias Gramnegativas produtoras de carbapenemase: Enterobacter cloacae, Klebsiella pneumoniae e Serratia marcescens. Metodologia: A identificação bacteriana foi realizada por Vitek ® 2, BD Phoenix TM 100 e MALDI-ToF ToF. A susceptibilidade antibacteriana foi determinada por microdiluição em caldo e MALDI-ToF ToF. A presença de genes que codificam betalactamases foi avaliada por PCR. A atividade antibacteriana foi avaliada utilizando discodifusão em ágar, microdiluição em caldo, time kill e checkboard. O possível mecanismo de ação da CCeo foi avaliado por PCR, RT-PCR, RT-qPCR e ensaio de extravasamento de proteínas. Resultados: A produção de carbapenemase foi confirmada por MALDI-ToF ToF e a PCR mostrou a presença dos genes blaKPC-2 para todas as cepas e também blaIMP-10 para S. marcescens. CCeo apresentou efeito inibitório contra E. cloacae (MIC, 17,57 μg.mL -1 ), K. pneumoniae (MIC, 281,25 μg.mL -1 ) e S. marcescens (MIC, 281,25 μg.mL -1 ). As curvas de sobrevivência das cepas mostraram uma diminuição na contagem de células viáveis ao longo do tempo e quando CCeo foi testado em associação com a POL contra K. pneumoniae e S. marcescens, foi confirmado o sinergismo. Foi observado vazamento de proteínas quando S. marcescens foi tratada com concentrações crescentes de CCeo e CCeo combinada com POL. Conclusões: CCeo apresentou atividade antibacteriana contra as cepas estudadas e quando associado à POL apresentou um efeito sinérgico capaz de inibir o crescimento bacteriano de forma rápida e consistente. CCeo desestabiliza a membrana externa da bactéria, o que leva à morte celular devido à entrada da POL no espaço periplasmático permitindo sua ação. Introduction: The emergence of bacterial multidrug resistance is an important public health problem that has resulted in the need to explore novel therapeutic options. There is a wide variety of antibacterial targets not used by the current drugs to be exploited. The objective of the present study was the investigation of the antibacterial activity of Cinnamomum cassia L. essential oil (CCeo) alone and in combination with polymyxin B (POL) against carbapenemaseproducing Gram-negative bacteria: Enterobacter cloacae, Klebsiella pneumoniae and Serratia marcescens. Methodology: Bacterial identification was performed by Vitek ® 2, BD Phoenix TM 100 and MALDI-ToF ToF . Antibacterial susceptibility was determined by broth microdilution and MALDI-ToF ToF . The presence of beta-lactamase-encoding genes was assessed by PCR. The antibacterial activity of CCeo was evaluated using the agar disk diffusion, broth microdilution, time-kill and checkboard methods. Possible CCeo mechanism of action was assessed by PCR, RT -PCR, RT -qPCR, and protein leakage assay . Results: The carbapenemase production was confirmed by MALDI-ToF ToF and PCR showed the presence of blaKPC-2 for all the studied strains and also blaIMP-10 for S. marcescens. CCeo exhibited a inhibitory effect against carbapenem-resistant E. cloacae (MIC, 17,57 μg.mL -1 ), K. pneumoniae (MIC, 281.25 μg.mL -1 ) and S. marcescens (MIC, 281.25 μg.mL -1 ). The survival curves of the strains showed a decrease in viable cell counts over time and when CCeo was tested in association with POL against K. pneumoniae and S. marcescens, synergism was confirmed. It was observed protein leakage when S. marcescens was treated with increasing concentrations of CCeo and CCeo + POL. Conclusions: CCeo presents antibacterial activity against the studied strains and when CCeo is associated with POL, a synergistic effect is able to inhibit bacterial growth rapidly and consistently, making it an interesting candidate for development of alternative treatment for carbapenemase-producing strains. CCeo destabilizes the outer membrane of the bacterium, making possible the cell entrance of the POL in the periplasmic space allowing its action and leading to cell death.