RESUMEN
1. This study determined the antimicrobial resistance profile and the biofilm-forming ability of Salmonella enterica strains isolated from commercial broiler houses over a three-year period in southern Brazil.2. Of the 720 drag swabs analysed, 37 (5%) tested positive for non-typhoidal Salmonella spp. and S. Heidelberg was the most frequent serovar.3. Among the antimicrobial resistant strains (83.8%; 31/37), resistance was most common to tetracycline, ampicillin and nalidixic acid. Multidrug resistance was found in 65% (24/37) of the isolates, with a large proportion of multidrug resistant S. Heidelberg strains (81%; 13/16).4. In total, 65% (24/37) of the isolates showed the ability to produce biofilm and multiple antimicrobial resistance was negatively correlated with biofilm formation.5. Strains susceptible to all tested antimicrobials tended to form stronger biofilms than multidrug resistant ones. This suggested that Salmonella spp. with less antimicrobial resistance depend more on the protection provided by biofilm to survive in the farm environment.
Asunto(s)
Antibacterianos , Salmonella enterica , Animales , Antibacterianos/farmacología , Serogrupo , Granjas , Brasil , Farmacorresistencia Bacteriana , Farmacorresistencia Bacteriana Múltiple , Pollos , Salmonella , Biopelículas , Pruebas de Sensibilidad Microbiana/veterinariaRESUMEN
Data about phylogenetic classification of Escherichia coli colonizing calves, lambs and foals are routinely neglected and restricted to outdated methodologies, even in the context of antimicrobial susceptibility (AS) testing. Thus, the aim of this study was to determine the phylogenetic diversity and the AS profile of E. coli colony-forming units (CFUs) from faecal samples of healthy animals. Five CFUs of E. coli were randomly selected from each faecal culture of calves (n = 13), foals (n = 13) and lambs (n = 13), totalizing 195 CFUs phylo-typed by quadruplex PCR. The AS profile of five CFUs from 15 samples (five from each animal species; n = 75 isolates) against nine drugs was determined by agar diffusion test. We found E. coli belonging to all phylo-groups already described, except D group, with the predominance of B1 (65% CFUs; 126/195) in the three-animal species sampled. Most faecal samples of calves (77%; 10/13) and foals (69%; 9/13) harboured both pathogenic and nonpathogenic E. coli. All faecal samples showed CFUs with diverse AS profile, highlighting the ineffectiveness of tetracycline, sulphonamide and ampicillin. As a key point, our data reinforce the importance to select at least four E. coli CFUs for AS testing. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides relevant data about the high phylogenetic and antimicrobial susceptibility diversity observed in Escherichia coli colony-forming units (CFUs) from a bacteriological culture of faeces from healthy calves, foals and lambs. The selection pressure exerted by the herd treatment may directly impact the intestinal microflora of animals that have never been treated. Finally, we emphasize the importance of Clinical Laboratory Standards Institute guidelines and we recommended to analyse at least four E. coli CFUs to determine, in particular, the antimicrobial susceptibility profile of faecal isolates, independent of the animal's health status.
Asunto(s)
Enfermedades de los Bovinos/microbiología , Infecciones por Escherichia coli/veterinaria , Escherichia coli/clasificación , Escherichia coli/efectos de los fármacos , Heces/microbiología , Animales , Antibacterianos/farmacología , Bovinos , Enfermedades de los Bovinos/tratamiento farmacológico , Escherichia coli/genética , Infecciones por Escherichia coli/tratamiento farmacológico , Caballos , Filogenia , Reacción en Cadena de la Polimerasa/veterinaria , Ovinos , Células MadreRESUMEN
AIMS: This study investigated the antibacterial activity of five phytochemicals (carvacrol, citral, eugenol, linalool and thymol) alone or in combination with florfenicol or oxytetracycline against bacteria isolated from silver catfish (Rhamdia quelen). We also analysed the potential of these compounds to inhibit biofilm formation and haemolysis caused by the bacteria. METHODS AND RESULTS: Bacteria were tested with antimicrobials to calculate the multiple antibiotic resistances. The checkerboard assay was used to evaluate a putative synergy between five phytochemicals and antimicrobials against the strains isolated. The biofilm formation inhibition assay was performed with phytochemicals and antimicrobials, and the haemolysis inhibition assay was performed with the phytochemicals. Carvacrol, eugenol and thymol were the most effective phytochemicals. Three combinations (linalool with florfenicol or oxytetracycline against Aeromonas hydrophila and citral with oxytetracycline against Citrobacter freundii) demonstrated synergy in the checkerboard assay. All phytochemicals inhibited biofilm formation and haemolysis activity. CONCLUSION: The tested phytochemicals showed satisfactory activity against fish pathogenic bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: The phytochemicals did not present antagonistic interactions with the antimicrobials, allowing their combined use, which may contribute to a decrease in the use of conventional drugs and their residues in aquatic environment.