ANTIMICROBIAL RESISTANCE OF ESCHERICHIA COLI F4+ STRAINS ISOLATED FROM SWINE IN THE PERIOD 2008-2011

Objectives - The aim of this study was to evaluate the antimicrobial trend in resistance of F4+ Escherichia coli isolated from pigs with E. coli diarrhea. Materials and methods - One hundred-nineteen F4+ pathogenic Escherichia coli isolated from diseased pigs in Northern Italy from 2008 to 2011 were analyzed for their susceptibility to 14 antimicrobials by disk diffusion method. The trend of resistance was determined using the χ2 test grouping the strains into two groups (isolates 2008-2009 and 2010-2011). Results - Isolates showed a statistically significant increasing trend of resistance to cefquinome (from 11% to 24%), danofloxacin (from 14% to 35%), enrofloxacin (from 27% to 32%) and florfenicol (from 21% to 32%). Resistance to the remaining 10 antimicrobial agents tested (aminosidine 33%-35%, gentamicin 27%-31%, flumequine 32%-34%, marbofloxacin 22%-28%, apramycin 45%-46%, colistin 9%-11%, trimethoprim-sulphonamide 48%-42%, thiamphenicol 82%-84%, tetracycline 95%-96%, erythromycin 90%-92% did not change significantly over the study period. On the basis of antimicrobial multi-resistance the strains were collected into three groups: 1. strains resistant to 1-5 antimicrobials (23/119); 2. to 6-10 antimicrobials (73/119); 3. > 10 antimicrobials (23/119). Over the study period, the number of isolates belonging to the first, second and third group showed a significant decreasing trend (P<0.05; R -0.89), no significant change and an increasing trend (P<0.05; R 0.84) respectively. Conclusions - The results of this study indicate an increasing trend to cefquinome, danofloxacin, enrofloxacin and florfenicol in E. coli F4+ isolates. A significant increasing of multi-resistant strains was observed from 2008 to 2011. This indicates the need for continued surveillance studies so that appropriate strategies can be developed to contrast the development of resistance in these and other pathogens.