Multidrug-resistant Escherichia coli harbouring mcr-1 and blaCTX-M genes isolated from swine in Argentina.

OBJECTIVES: Multidrug-resistant Escherichia coli isolates recovered from food-producing animals are a global public-health concern, especially those with transferable mechanisms of antimicrobial resistance such as extended-spectrum ß-lactamase (ESBL) and mcr-1 genes. Here we report for the first time E. coli recovered from diarrhoeic and healthy pigs harbouring blaCTX-M and/or mcr-1 from Argentinean farms. METHODS: During 2017, a total of 34 E. coli were recovered from 31 faecal samples from diarrhoeic piglets and healthy fattening pigs from five pig farms in three Argentinean provinces. Antimicrobial susceptibility was evaluated by agar diffusion and resistance genes were identified by PCR. Multiplex PCR was applied to screen for ST69, ST73, ST95 and ST131 clones. Genetic relationships were evaluated by XbaI-PFGE. RESULTS: A high diversity of resistance profiles was observed (20 profiles among 34 isolates), and 71% of isolates were multidrug-resistant. Resistance to third-generation cephalosporins (3GCs) was observed in 28 isolates and was associated with blaCTX-M (24), blaCMY (3) and blaPER-2 (1) genes. blaCTX-M alleles were grouped by specific PCR as follow: 17 blaCTX-M-8/25; 4 blaCTX-M-1/15; 2 blaCTX-M-2; and 1 blaCTX-M-9/14. Twelve isolates were positive for mcr-1, of which six were also resistant to 3GCs and were positive for blaCTX-M-8/25 (4), blaCTX-M-1/15 (1) or blaCMY (1). High genetic diversity was observed, discriminating 29 profiles. One ST131 and two ST95 human-associated clones were detected. CONCLUSION: Here we describe E. coli isolates recovered from diarrhoeic piglets and healthy fattening pigs harbouring ESBL and/or mcr-1 genes. 3GC resistance was mainly associated with CTX-M, in particular with blaCTX-M-8/25 alleles.

Wild-type minimal inhibitory concentration distributions in bacteria of animal origin in Argentina.

The aim of this study was to determine the antimicrobial resistance profiles of indicator bacteria isolated from domestic animal feces. Minimal inhibitory concentration (MIC) was determined by agar dilution. Interpretative criteria on the basis of wild-type MIC distributions and epidemiological cutoff values (ECOFF or ECV) were used according to the 'European Committee on Antimicrobial Susceptibility Testing' (EUCAST) data. Results from 237 isolates of Escherichia coli showed reduced susceptibility for ampicillin, streptomycin and tetracycline, the antimicrobials commonly used in intensive breeding of pigs and hens. Regarding all the species of the genus Enterococcus spp., there are only ECOFF or ECV for vancomycin. Of the 173 Enterococcus spp. isolated, only one showed reduced susceptibility to vancomycin and was classified as 'non-wild-type' (NWT) population. This is the first report in Argentina showing data of epidemiological cutoff values in animal bacteria.

Distribución de la concentración inhibitoria mínima y puntos de corte "wild-type" en bacterias de origen animal en Argentina / Wild-typeminimal inhibitory concentration distributions in bacteria of animal origin in Argentina

El objetivo de este estudio fue determinar los patrones de resistencia antimicrobiana en bacterias indicadoras aisladas de muestras fecales de animales domésticos. La concentración inhibitoria mínima (CIM) fue determinada por el método de dilución en agar. El criterio de interpretación usado se basó en la distribución de la CIM y el punto de corte epidemiológico (ECOFF o ECV) de acuerdo con los datos del European Committee on Antimicrobial Susceptibility Testing (EUCAST). Los resultados obtenidos de 237 aislamientos de Escherichia coli mostraron sensibilidad reducida a ampicilina, estreptomicina y tetraciclina, antimicrobianos comúnmente usados en porcinos y aves de explotación intensiva. Con respecto a todas las especies del género Enterococcus spp., solo existe ECOFF o ECV para la vancomicina. De los 173 Enterococcus spp. aislados, sólo uno presentó sensibilidad reducida a dicho agente y fue categorizado como población 'non-wild-type' (NWT). Este es el primer informe en Argentina que presenta datos de puntos de corte epidemiológico en bacterias animales

The aim of this study was to determine the antimicrobial resistance profiles of indicator bacteria isolated from domestic animal feces. Minimal inhibitory concentration (MIC) was determined by agar dilution. Interpretative criteria on the basis of wild-type MIC distributions and epidemiological cutoff values (ECOFF or ECV) were used according to the 'European Committee on Antimicrobial Susceptibility Testing' (EUCAST) data. Results from 237 isolates of Escherichia coli showed reduced susceptibility for ampicillin, streptomycin and tetracycline, the antimicrobials commonly used in intensive breeding of pigs and hens. Regarding all the species of the genus Enterococcus spp., there are only ECOFF or ECV for vancomycin. Of the 173 Enterococcus spp. isolated, only one showed reduced susceptibility to vancomycin and was classifi ed as 'non-wild-type' (NWT) population. This is the fi rst report in Argentina showing data of epidemiological cutoff values in animal bacteria