RESUMEN
Coastal water quality is facing increasing threats due to human activities. Their contamination by sewage discharges poses significant risks to the environment and public health. We aimed to investigate the presence of antibiotic-resistant Enterococcus in beach waters. Over a 10-month period, samples were collected from four beaches in the State of São Paulo (Brazil). Enterococcus isolates underwent matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) and molecular analysis for accurate genus and species identification. The antimicrobial susceptibility for 14 antibiotics was evaluated using the disc diffusion method followed by a multidrug-resistance (MDR) classification. PCR amplification method was used to detect antimicrobial resistance genes (ARGs). Our findings revealed the prevalence of Enterococcus faecalis, E. faecium and E. hirae. Out of 130 isolates, 118 were resistant to multiple antibiotics. The detection of resistance genes provided evidence of the potential transfer of antibiotic resistance within the environment. Our findings underscore the necessity for continuous research and surveillance to enhance understanding of the pathogenicity and antimicrobial resistance mechanisms of Enterococcus, which is crucial to implement effective measures to preserve the integrity of coastal ecosystems.
Asunto(s)
Antibacterianos , Enterococcus faecalis , Enterococcus faecium , Enterococcus hirae , Brasil , Enterococcus faecalis/efectos de los fármacos , Enterococcus faecalis/genética , Enterococcus faecalis/aislamiento & purificación , Enterococcus faecium/efectos de los fármacos , Enterococcus faecium/genética , Enterococcus faecium/aislamiento & purificación , Antibacterianos/farmacología , Enterococcus hirae/efectos de los fármacos , Enterococcus hirae/genética , Enterococcus hirae/aislamiento & purificación , Farmacorresistencia Bacteriana , Playas , Pruebas de Sensibilidad Microbiana , Agua de Mar/microbiologíaRESUMEN
The purpose of this study was to select the promising biopreservation bacteriocin producer strain from goat milk and characterize the expressed bacteriocin, related to its physiological and biochemical properties and specificity of operon encoding production and expression of antimicrobial peptide. Brazilian goat milk was used as the source for the selection of bacteriocin-producing lactic acid bacteria. One strain (DF105Mi) stood out for its strong activity against several Listeria monocytogenes strains. Selected strain was identified based on the biochemical and physiological characteristics and 16s rRNA analysis. The bacteriocin production and inhibitory spectrum of strain DF105Mi were studied, together with the evaluation of the effect of temperature, pH, and chemicals on bacteriocin stability and production, activity, and adsorption to target cells as well as to the cell surface of bacteriocin producers. Physiological and bio-molecular analyses based on targeting of different genes, parts of nisin operon were performed in order to investigate the hypothesis that the studied strain can produce and express nisin. Based on biochemical, physiological, and 16s rRNA analysis, the strain DF105Mi was classified as Enterococcus hirae. The selected strain produces a bacteriocin which is stable in a wide range of pH (2.0-12.0), temperature (up to 120 °C), presence of selected chemicals and presents adsorption affinity to different test organisms, process influenced by environmental conditions. Higher bacteriocin production by Ent. hirae DF105Mi was recorded during stationary growth phase, but only when the strain was cultured at 37 °C. The strain's genetic analysis indicated presence of the genes coding for the production of the bacteriocin nisin. This result was confirmed by cross-checking the sensitivity of the produced strain to commercial nisin A. The strong anti-Listeria activity, bacteriocin adsorption, and stability of produced bacteriocin indicate that Ent. hirae DF105Mi presents a differentiated potential application for biopreservation of fermented dairy products.
Asunto(s)
Enterococcus hirae/aislamiento & purificación , Enterococcus hirae/metabolismo , Leche/microbiología , Nisina/metabolismo , Animales , Brasil , Enterococcus hirae/clasificación , Enterococcus hirae/genética , Cabras , Concentración de Iones de Hidrógeno , Listeria monocytogenes/efectos de los fármacos , Listeria monocytogenes/crecimiento & desarrollo , Nisina/química , Nisina/farmacologíaRESUMEN
The bacteriocinogenic Enterococcus hirae ST57ACC recently isolated from a Brazilian artisanal cheese was subjected here to additional analyses in order to evaluate its bacteriocin production and the potential influence of ABC transporter system in its expression. Besides these physiological and molecular aspects, the bacteriocin was evaluated for its cytotoxicity against HT-29. Differences in the inoculum size had no impact on the growth of E. hirae ST57ACC; however, the bacteriocin was only produced after 9 h of growth when the strain was inoculated at 5% or 10% (v/v), with similar levels of bacteriocin production obtained by both conventional growth and batch fermentation. Furthermore, potential expression of ABC transporters corresponding to the bacteriocin transport and sugar metabolism was identified. In terms of adverse effects, when a semi-purified fraction of the bacteriocin and the cell-free supernatant were tested against HT-29, total cell viability was similar to observed on untreated cells, indicating the absence of cytotoxic effect. Based on the obtained results, E. hirae ST57ACC can produce its bacteriocin at industrial level by using bioreactors, its bacteriocin expression is potentially influenced by the ABC transporter system, and no cytotoxic effects were observed on HT-29 cells, indicating its potential use as a bio-preservative.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/metabolismo , Bacteriocinas/biosíntesis , Bacteriocinas/toxicidad , Queso/microbiología , Enterococcus hirae/metabolismo , Bacteriocinas/genética , Brasil , Metabolismo de los Hidratos de Carbono , Línea Celular , Enterococcus hirae/genética , Enterococcus hirae/aislamiento & purificación , Conservantes de Alimentos , Células HT29 , HumanosRESUMEN
Bacteriocinogenic Enterococcus hirae ST57ACC and Pediococcus pentosaceus ST65ACC strains, previously isolated from artisanal cheese, were evaluated for their safety with the aim to determine whether they could be used as beneficial strains, especially in the control of Listeria monocytogenes. Both isolates survived simulated gastrointestinal conditions and showed high levels of auto- and co-aggregation with L. monocytogenes, although the hydrophobicity of cells varied. Using the agar-spot test with 33 commercial drugs from different groups, only anti-inflammatory drugs and drugs containing loratadine and propranolol hydrochloride were able to affect the growth of the tested strains. Both strains were resistant to 3 out of 11 antibiotics tested by the disc diffusion method, and low frequencies of antibiotic resistance-encoding genes were observed by PCR analysis. Tested strains neither presented biogenic amine-related genes nor produced these substances. Aside from some antibiotic resistance characteristics, the tested strains were considered safe as they lack other virulence-related genes. E. hirae ST57ACC and P. pentosaceus ST65ACC both presented beneficial properties, particularly their ability to survive gastrointestinal conditions and to aggregate with L. monocytogenes, which can facilitate the elimination of this pathogen. Further studies should be conducted to better understand these interactions.