Comparative molecular analysis of veterinary, dairy, and clinical Staphylococcus aureus isolates by spa typing and amplification of the mecA and the PVL genes

Abstract number: 1733_798

Stöger A., Gonano M., Pietzka A., Allerberger F., Wagner M., Ruppitsch W.

Objectives: The aim of this study was to compare Staphylococcus aureus isolates of veterinary, dairy and human origin to evaluate a possible animal-to-food, human-to-animal, and/or human-to-food transmission or vice versa.

Methods: 1,058 isolates were collected by screening cows suspected of having mastitis, from vat milk and fresh cheese, from wounds of ambulant patients and from hospitalised patients. Sequencing of the variable X-region of the protein A gene (spa typing), detection of the methicillin resistance gene (mecA), and detection of the Panton-Valentine leukocidin gene (PVL) were used for molecular comparison of these isolates.

Results: All tested veterinary isolates (n = 60), dairy isolates (n = 64), and 11 isolates from the ambulant patients, and 57 isolates from hospitalised patients were negative for mecA (MSSA). The remaining 860 clinical isolates were positive for mecA (MRSA). The PVL gene as a marker for CA-MRSA was detected in a single veterinary isolate of spa type t042, which is closely related to CA-MRSA t044. Typing yielded 152 spa types. Thirty-four spa types were identified for the 60 veterinary isolates, 35 for the 64 dairy isolates, 28 for the 59 human MSSA isolates, and 134 for the 860 clinical MRSA isolates. 24 new spa types were found among the veterinary and dairy isolates that were not described in the spa database (RIDOM). In contrast to the clinical MRSA isolates, where the majority belonged to spa complexes SC I and SC II the majority of veterinary, dairy and also the MSSA isolates belonged mainly to spa complexes SC VI and SC VII. 11 spa types of the human population including t190 and t008 were also found in the veterinary or in the dairy isolates. Spa type t529 was the only one that was detectable in all populations. Approximately 50% of veterinary and dairy isolates belonged to nine common spa types which were different from that found in the human isolates.

Conclusion: Typical and very frequent human spa types i.e. t190 or t008 rarely occurred in veterinary and dairy isolates. However, the occurrence of typical human isolates on cow udders and in milk and fresh cheese might reflect a possible transmission from human to animals and food. No MRSA was detected among the veterinary and dairy isolates. The high number of identical spa types in veterinary and dairy isolates indicated a transmission of Staphylococci from animal reservoirs into the dairy chain.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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