Abstract
Escherichia coli is considered one of the most common agents associated with neonatal diarrhea in piglets. The aim of this work was to characterize the pathogenic and antimicrobial resistance (AMR) profiles of 122 E. coli strains isolated from pigs suffering diarrhea (n = 94) and pigs without diarrhea (n = 28) of 24 farms in Spain. Virulence factors, toxins and AMR (ESBL and colistin) genes and AMR phenotypes of E. coli isolates were analyzed. Low prevalence of pathogenic E. coli strains (26%) was found in both groups. However, ETEC and VTEC strains were more frequently isolated from diarrheic piglets. Irrespectively of diarrhea occurrence, 97.5% of the strains showed a multidrug-resistance (MDR) profile to aminopenicillins, sulfonamides and tetracyclines. It was found that 22% of E. coli was CTX-M+, with CTX-M-14 being the principal allelic variant. Remarkably, 81.5% of CTX-M+ strains were isolated from diarrheic animals and presented an extended MDR profile to aminopenicillins, quinolones and aminoglycosides. Finally, low frequencies of colistin resistance genes mcr-1 (4/122) and mcr-4 (1/122) were found. MDR E. coli strains are circulating in pig farms of Spain, representing a serious threat to animal and public health. More appropriate diagnostic approaches (genetic and AMR phenotypic analysis) should be implemented in animal health to optimize antibiotic treatments.
Highlights
Escherichia coli has historically been considered as one of the most common agents associated with diarrhea in suckling and post-weaned piglets [1]
The characterization of pathogenic E. coli strains is usually based on the presence of virulence factors [3]
E. coli pathogenic strains can be classified into different pathotypes: enterotoxigenic (ETEC) strains releasing heat-labile (LT) and heat-stable Sta and Stb exotoxins, intimin-producing enteropathogenic (EPEC) strains and verotoxigenic (VTEC) strains producing VT1/VT2 verotoxins [4]
Summary
Escherichia coli has historically been considered as one of the most common agents associated with diarrhea in suckling and post-weaned piglets [1]. There is high diversity and variants of E. coli strains integrating the normal gut microbiota, with most of them being considered not pathogenic [2]. The characterization of pathogenic E. coli strains is usually based on the presence of virulence factors [3]. E. coli pathogenic strains can be classified into different pathotypes: enterotoxigenic (ETEC) strains releasing heat-labile (LT) and heat-stable Sta and Stb exotoxins, intimin (eae)-producing enteropathogenic (EPEC) strains and verotoxigenic (VTEC) strains producing VT1/VT2 verotoxins [4]. The routine use of antimicrobials in livestock, especially in the pig industry, for either ‘prophylaxis’. ‘metaphylaxis’ represents a serious hazard for the selection of multidrug-resistant (MDR).
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