Heterogeneity among methicillin-resistant Staphylococcus aureus from Italian pig finishing holdings

A survey for methicillin-resistant Staphylococcus aureus (MRSA) in finishing pig holdings was carried out in Italy in 2008. MRSA isolates were characterised by spa-, MLST-, SCCmec- and antimicrobial susceptibility typing. A prevalence of 38% (45/118, 95% CI 29.4-46.9%) positive holdings was observed. Eleven different spa-types were found among 102 MRSA isolates, clustering in lineages associated with farm animals (ST398, ST9, ST(CC)97 in 36 holdings) and humans (ST1, 7 holdings). Nine (7.6%) holdings were positive for two, three or four different and unrelated spa-types in various combinations. ST398 was the most prevalent lineage (33 positive holdings). The most prevalent spa-type was t899 (ST398), detected in 22 positive holdings. Three novel spa-types (t4794 of ST9; t4795 of ST97; t4838 of ST398) were detected. Ten holdings were positive for spa-type t1730, that proved to be a new single-locus variant of ST97, within the CC97 (ST1476). The most prevalent SCCmec was Type V (79 isolates), while Type IVb was found in 10 isolates. None of the isolates was positive for Panton-Valentine Leukocidin, while most of the t127 and t1730 isolates, one t4794, one t4795, and one t2922 were positive for LukE-LukD genes. All 64 antimicrobial susceptibility tested isolates were resistant to tetracyclines, with high resistance rates to trimethoprim (68.8%), erythromycin (60.9%), and ciprofloxacin (35.4%). All t127, ST1 isolates were resistant to tetracycline-ciprofloxacin-erythromycin. This survey provides the first report of MRSA ST1 and ST(CC)97 among pigs and the first report of MRSA ST9 from pigs in Europe. The presence of human-associated CA-MRSA (t127, ST1, SCCmec type V) in 6% holdings surveyed can represent an additional MRSA reservoir for infections in humans.

Prevalence and concentration of Verotoxigenic Escherichia coli O157:H7 in adult sheep at slaughter from Italy

A 1-year study on the animal-level prevalence and concentration of Escherichia coli O157 in adult sheep at slaughter was performed, to collect qualitative and quantitative information on the diffusion of the pathogen in adult sheep from Italy. A total 533 samples were collected, with a similar distribution in the four seasons. For prevalence estimates, a simple random sampling technique was used. An immuno-magnetic separation technique was used for sample screening, with enumeration of the pathogen in positive samples, along with molecular and serological identification of isolates. An overall prevalence of 7.1% (38/ 533, 95% CI 4.9-9.3%) was observed for fully virulent E. coli O157. A wide interval of VTEC O157 per gram was observed (< 100 to 6 x 10(5) CFU g(-1)), with 28.9% (11/38) of positive samples > or = 1 x 10(3) CFU g(-1), set as the threshold for those animals defined 'active shedders' for the purpose of the study. Eight per cent (3/38) of animals shed > 1 x 10(4) g(-1) VTEC O157, which represents > 96% of the total VTEC O157 bacteria cultured from all animals tested. The prevalence estimate of active shedders was therefore 2.1% (95% CI 0.9-3.3%). Most (34/38, 89.5%) of the positive animals were found in summer (July-September). Prevalence and concentrations of virulent VTEC O157 obtained in this study contribute to the demonstration that adult sheep represent a relevant source of environmental contamination from virulent VTEC O157, as well as a source of VTEC O157 contamination for food of ovine origin (meat and dairy products), especially during warm months.