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We investigated the 16S-23S rRNA intergenic spacer region (ISR)-PCR and the phylogenetic PCR analyses of 150 Escherichia coli isolates as tools to explore their diversity, according to their sampling origins, and their relative dominance in these sampling sources. These genetic markers are used to explore phylogenetic and genetic relationships of these 150 E. coli isolates recovered from different environmental sources (water, food, animal, human and vegetables). These isolates are tested for their biochemical pattern and later genotyped through the 16S-23S rRNA intergenic spacer PCR amplification and their polymorphism investigation of PCR-amplified 16S-23S rDNA ITS. The main results of the pattern band profile revealed one to four DNA fragments. Distributing 150 E. coli isolates according to their ITS and using RS-PCR, revealed four genotypes and four subtypes. The DNA fragment size ranged from 450 to 550 bp. DNA band patterns analysis revealed considerable genetic diversity in interspecies. Thus, the 450 and 550 bp sizes of the common bands in all E. coli isolates are highly diversified. Genotype I appeared as the most frequent with 77.3% (116 isolates), genotype II with 12% (18 isolates); genotype III with 9.7% (14 isolates), and the IV rarely occurred with 4% (2 isolates). Distributing the E. coli phylogroups showed 84 isolates (56%) of group A, 35 isolates (23.3%) of group B1, 28 isolates (18.7%) of group B2 and only three isolates (2%) of group D., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Livestock and food products of animal origin constitute important reservoirs of intestinal and extraintestinal pathogenic Escherichia coli including antibiotic-resistant E. coli isolates. To assess potential risks to public health related to E. coli strains of animal origin in Tunisia, 65 E. coli isolates recovered from healthy animals and food products of animal origin were studied. Antimicrobial susceptibility was determined according to CLSI guidelines and genes encoding antibiotic resistance as well as virulence factors were investigated by PCR. High rates of antibiotic resistance were observed to kanamycin (78.4%), gentamicin (75.3%) and streptomycin (75.3%, encoded by strA-strB (7 isolates)), amoxicillin (64.6%), amoxicillin/clavulanic acid (60%), tetracycline (44.6%; tetA (8 isolates) and tetB (7 isolates)), nalidixic acid (27.6%, qnrS (3 isolates), qnrB (2 isolates) and qnrA (one isolate)) and sulfonamides (36.9%; sul1 (1 isolate), sul2 (4 isolates), and sul3 (1 isolate)). Virulotypes classified some isolates as STEC (3%), MNEC (1.5%) and atypical EPEC (1.5%). This study demonstrated high rates of antimicrobial resistance and the presence of some pathogenic pathovars from animal origins that are a cause of concern for public health.