Studio dei fattori di virulenza e profilo di antimicrobico-resistenza in ceppi di Escherichia coli isolati da galline ovaiole da consumo.

Colibacillosis is the most frequent bacterial disease in avian species: it induces significant economic losses on industrial poultry breeding, especially if characterized by a long production cycles like those of laying hens, in which the disease tends to become endemic and it is difficult to eradicate. Management strategies and the use of antibiotic treatments are essential for the control of the infection. However, over the years, there has been an increase in the isolation of Escherichia coli strains with multiple resistance to various classes of antimicrobials, which turns out to be a serious problem for the breeders but also for the public health. In this study antimicrobial resistance feature, the serogroup and the presence of APEC virulence genes have been investigated in E. coli strains isolated during outbreaks of colibacillosis in laying hens from intensive farming located in Emilia Romagna and in other Italian regions. The relationship of the results of each parameters was evaluated. A total of 71 E. coli strains were, therefore, subjected to serotyping for the identification of serogroup (based on somatic antigen “O”), to PCR to detect the presence of virulence genes and to Kirby Bauer antimicrobial susceptibility test. A statistical study was also carried out to evaluate a correlation between these parameters. The most frequently isolated serogroups were O2 (21%) and O88 (13%). Resistance was most frequently detected against nalidixic acid (49%) and ampicillin (38%) and all strains were sensitive to ceftiofur and florfenicol. Overall, 25% of the isolates showed resistance to at least three or more antimicrobials (MDR) and 56% of the isolates were defined APEC strains (presence of at least 5 virulence genes). The most frequently encountered virulence gene was iss(90% of cases), followed by iucD (85%), cvi/cva (70%), irp2 (70%) and tsh (63%).On the other hand, virulence gene astA was detected in only 6% of the strains analyzed, followed by papC(14%) and vat (35%). The correlation between the different parameters (resistance genes, serotype and antimicrobial resistance) did not highlight particular associations. The comparison of the obtained results with those of similar studies highlights the importance of the continuous monitoring in order to have a real evaluation of the national epidemiological situation and, especially with regard to antimicrobial resistance, to be adopted the preventive measures with a view to a One Health approach towards APEC infections.