Resistance phenotypes and genotypes of methicillin-resistant Staphylococcus aureus isolates from broiler chickens at slaughter and abattoir workers

Objectives: To comparatively investigate the resistance phenotypes and genotypes of various methicillin-resistant Staphylococcus aureus (MRSA) isolates from broilers at slaughter and workers at the respective poultry slaughterhouses. Methods: Forty-six MRSA isolates (28 from broilers and 18 from humans) obtained at four different slaughterhouses were included. In addition to previously determined sequence types (STs) and spa types, the isolates were characterized by dru typing, SCCmec typing and PFGE. Resistance phenotypes were determined by broth microdilution. Resistance genes and clonal complexes (CCs) were detected by DNA microarray or specific PCR assays. Results: MRSA of CC398, spa type t011 and varying dru types represented 23/28 broiler isolates and 12/18 human isolates. Three ST9/t1430/dt10a isolates were each seen among the isolates from the abattoir workers and the broilers. In addition, two human CC398/ST1453/t4652/dt3c isolates, a single human CC398/t034/dt6j isolate and two chicken CC398/t108/dt11a isolates were detected. All CC398 isolates (including ST1453) and some of the ST9 isolates from chickens and humans showed resistance to four to nine classes of antimicrobial agents and carried a wide range of resistance genes. While the resistance phenotypes and genotypes of the chicken isolates of the same flock were closely related, they usually differed from the resistance phenotypes and genotypes of the isolates from the workers at the respective slaughterhouse. Conclusions: The apparent homogeneity of MRSA isolates from the same flock suggests exchange of isolates between the respective animals. The apparent heterogeneity of MRSA isolates from abattoir workers might reflect their occupational contact with animals from numerous chicken flocks.