RESUMO
This study describes a new effort toward understanding the interaction mechanisms between antibiotic-resistant Salmonella Typhimurium and phages. The antibiotic susceptibility, ß-lactamase activity, bacterial motility, gene expression, and lytic activity were evaluated in ciprofloxacin-induced antibiotic-sensitive Salmonella Typhimurium (ASST(CIP)) and ciprofloxacin-induced antibiotic-resistant S. Typhimurium (ARST(CIP)), which were compared to the wild-type strains (ASST(WT) and ARST(WT)). The MIC values of ampicillin, norfloxacin, chloramphenicol, and tetracycline were significantly increased to > 512, 16, 16, and 256 µg/ml, respectively, in the ARST(CIP). The lowest and highest extracellular lactamase activities were observed in ASST(WT) (6.85 µmol/min/ml) and ARST(CIP) (48.83 µmol/min/ml), respectively. The acrA, lpfE, and hilA genes were significantly upregulated by more than tenfold in both ASST(CIP) and ARST(CIP). The induction of multiple antibiotic resistance resulted from the increased efflux pump activity (AcrAB-TolC). The highest phage adsorption rates were more than 95 % for ASST(WT), ASST(CIP), and ARST(WT), while the lowest adsorption rate was 52 % for ARST(CIP) at 15 min of infection. The least lytic activity of phage was 20 % against the ARST(CIP), followed by ASST(CIP) (30 %). The adsorption rate of phage against ARST(CIP) was 52 % at 15 min of infection, which resulted in the decrease in lytic activity (12 %). Understanding the interaction of phage and bacteria is essential for the practical application of phage to control and detect antibiotic-resistant bacteria. The results provide useful information for understanding the binding specificity of phages for multiple antibiotic-resistant pathogens.
Assuntos
Antibacterianos/farmacologia , Bacteriófagos/genética , Ciprofloxacina/farmacologia , Farmacorresistência Bacteriana Múltipla/genética , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/genética , Ampicilina/farmacologia , Proteínas de Bactérias/biossíntese , Proteínas de Bactérias/genética , Sítios de Ligação , Cloranfenicol/farmacologia , Proteínas de Membrana Transportadoras/biossíntese , Proteínas de Membrana Transportadoras/genética , Testes de Sensibilidade Microbiana , Norfloxacino/farmacologia , Salmonella typhimurium/virologia , Tetraciclina/farmacologia , Transativadores/biossíntese , Transativadores/genética , beta-Lactamases/genéticaRESUMO
To develop a practical and cost-effective medium for bioethanol production from the hydrolysate of seaweed Sargassum sagamianum, we investigated the feasibility and performance of bioethanol production in CSL (cornsteep liquor)-containing medium, where yeast Pichia stipitis was used and the repeated batch was carried out in a surface-aerated fermentor. The optimal medium replacement time during the repeated operation was determined to be 36 h, and the surface aeration rates were 30 and 100 ml/min. Under these conditions, the repeatedbatch operation was successfully carried out for 6 runs (216 h), in which the maximum bioethanol concentrations reached about 11-12 g/l at each batch operation. These results demonstrated that bioethanol production could be carried out repeatedly and steadily for 216 h. In these experiments, the total cumulative bioethanol production was 57.9 g and 58.0 g when the surface aeration rates were 30 ml/min and 100 ml/min, respectively. In addition, the bioethanol yields were 0.43 (about 84% of theoretical value) and 0.44 (about 86% of theoretical value) when the surface aeration rates were 30 ml/min and 100 ml/min, respectively. CSL was successfully used as a medium ingredient for the bioethanol production from the hydrolysate of seaweed Sargassum sagamianum, indicating that this medium may be practical and cost-effective for bioethanol production.