Antimicrobial susceptibility of environmental Staphylococcus aureus strains isolated from a pigeon slaughterhouse in Italy

No information is available concerning the antimicrobial susceptibility of Staphylococcus aureus isolated from pigeon slaughterhouses. In the present study, 59 staphylococcal strains isolated from a pigeon slaughterhouse in central Italy were compared according to their antibiotic resistance. On the basis of cultural and biochemical properties, all isolates could be identified as S. aureus. The strains were checked for the productions of enterotoxins A, B, C, D by reversed passive latex agglutination. Resistance to 26 antibiotics was also determined paying particular attention to resistance to those antimicrobial agents frequently used in human medicine and in poultry breeding. Only one strain was positive for the production of enterotoxins type C and D. It was isolated from the evisceration tube after slaughtering. Enterotoxin B was produced by 2 strains isolated from the eyebrows and conjunctivas of the worker operating the crop rinsing tube. As to the susceptibility to antibiotics, all strains were sensitive to amoxicillin/clavulanic acid, bacitracin, cephalothin, fusidic acid, gentamicin, kanamycin, linezolid, oxacillin, quinupristin/dalfopristin, rifampicin, tobramycin, trimethoprim-sulfamethoxazole, vancomycin. Some (15.2%) of the strains were resistant to ampicillin and to penicillin G; 6.8% were resistant to chloramphenicol, 20.3% to enrofloxacin, 16.9% to erythromycin and to ciprofloxacin, 8.5% to clindamycin, and 11.9% to lincomycin. The highest percentages of strains were resistant to tetracycline and oleandomicin (37.3 and 25.4% respectively). Methicillin-resistant staphylococci were also found (3.4%). Only one strain had a multiple antibiotic resistance index >0.30. The results were statistically analyzed and clustered in 6 groups. This work provides the antibiotic resistance pattern of S. aureus strains isolated from a pigeon slaughtering plant and represents a study on a quite unknown field in meat production.