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Slaughterhouses produce huge volumes of effluents throughout the production chain that, when discharged untreated into bodies of water, can become a source of environmental contamination. This is particularly worrisome if these effluents are used for irrigation since they increase contamination levels and spread pathogens and resistance determinants to humans and animals. Therefore, in this study, we assessed antimicrobial resistance in bacteria isolated from inlet water, equalization wastewater tanks, treatment plant wastewater, and treated wastewater in slaughterhouse facilities in Rio de Janeiro, Brazil. Four samples were collected at each of the collection points, between June 2021 and July 2022. Following bacterial isolation and identification, the samples were analyzed for antimicrobial resistance using the disk diffusion method to test aminoglycoside, beta-lactam, and fluoroquinolone antimicrobials. A total of 229 bacteria were isolated, with 74 isolates selected from the genera Citrobacter (12), Enterobacter (14), Klebsiella (35), Serratia (5), and Pseudomonas (8). Inlet water had the lowest number of isolates and was the only point with gentamicin-resistant isolates. Raw effluent from the equalization tank showed the highest number of isolated bacteria and resistance levels, followed by treated wastewater and the treatment plant. Across all samples, a high rate of cefoxitin-resistance was observed among the isolated bacteria. Klebsiella pneumoniae stood out as the species that demonstrated the greatest resistance to a variety of antimicrobials. These results highlight the importance of water quality monitoring in mitigating public health and environmental risks and high antimicrobial resistance levels., (© 2024. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.)

Livestock waste is widely used in agriculture. Although they provide benefits to the soil, and consequently to plants, they have the potential to contaminate the environment, as they contain pathogenic microorganisms and determinants of antimicrobial resistance, if not properly managed. Therefore, this study aims to evaluate the effect of composting horse bedding and poultry litter in organic and conventional production systems on the occurrence of bacteria in the Enterobacteriales order and to identify their antimicrobial resistance profiles. Bacterial strains were isolated from Salmonella-Shigella and eosin methylene blue solid media from animal waste during the composting process that was conducted for 125 days. After isolation, the strains were identified by the MALDI-TOF technique; the disk diffusion test was then performed for phenotypic detection of antimicrobial resistance. A total of 158 bacterial strains were isolated during composting of three wastes. The Enterobacteriaceae family was the most abundant, whereas Proteus mirabilis and Escherichia coli were the species with the highest percentage in the wastes, which also exhibited a multi-resistance profile. Poultry litter showed a greater abundance of resistant bacteria than horse bedding did. Similarly, a greater number of resistant bacteria was detected in conventional poultry litter than in organic poultry litter. The results obtained reinforce that animal wastes are reservoirs of pathogenic bacteria that are resistant to antimicrobials and highlight the importance of developing management strategies that aim to reduce and/or eliminate these contaminants to guarantee their safe use in agriculture., (© 2023. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.)

AmpC is a type of β-lactamase enzyme produced by bacteria; these enzymes are classified in Class C and Group 1, and these confer resistance to cephamycin. Enterobacterales producing AmpC are reported worldwide and have great clinical importance due to therapeutic restriction and epidemiological importance once the easy dissemination by plasmidic genes to other bacteria is a real threat. These genes are naturally found in some enterobacteria as Enterobacter cloacae, Morganella morganii, and Citrobacter freundii, but other species have demonstrated similar resistance phenotype of AmpC production. Genes carried in plasmids have been described in these species conferring resistance to cefoxitin and causing therapeutic failure in some bacterial infections. This work detected and described five clinical strains of Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae that presented plasmid ampC (pAmpC) isolated from the north of Portugal collected in 2009. AmpC production was confirmed by inhibition of the enzyme by cloxacillin and boronic acid in agar diffusion tests. Also, PCR (polymerase chain reaction) was performed for the detection of gene universal to AmpC, bla ampC , and others to AmpC group: bla ACC , bla CIT , bla CMY , bla DHA , and bla EBC . The conjugation in liquid medium for 24 h was realized to determine if gene is localized in chromosome or plasmid. The isolates and their conjugants showed phenotypic characteristics and bla CMY and bla CIT were detected by PCR corroborating the AmpC characteristics observed in these bacteria. Confirmation of transfer of plasmid containing genes encoding AmpC is of high epidemiological relevance to the hospital studied and demonstrated the importance of AmpC surveillance and studies in hospital and community environments in order to choose the appropriate therapy for bacterial infections.