Limited value of routine spa typing: a cross-sectional study of methicillin-resistant Staphylococcus aureus-positive patients in an Austrian hospital.

BACKGROUND

We investigated whether spa typing is useful for indicating the setting of methicillin-resistant Staphylococcus aureus (MRSA) acquisition (community or health care acquired), the clinical relevance (colonization or infection), the type of infection (invasive or noninvasive), and the clinical outcome.

METHODS

Between August 2006 and December 2009, 381 routinely diagnosed culture-confirmed MRSA-positive patients were included into a cross-sectional study at an 800-bed hospital.

RESULTS

Out of 159 patients with colonization, 27 (17%) acquired MRSA in the community (CA-MRSA) and 123 (77.4%) in health care settings (HA-MRSA), and, of the 222 patients with infections, 119 (53.6%) had HA-MRSA and 103 (46.4%) had CA-MRSA. The 10 most frequent spa types accounted for 68.2% of the 346 typed MRSA isolates: t190 (28.3%), t032 (16.5%), t041 (9.4%), t008 (8.4%), t001 (3.4%), t002 (2.9%), t044 (3.1%), t223 (2.1%), t015 (2.1%), t127 (1.3%).

CONCLUSION

Spa typing of routinely identified MRSA isolates is unsuitable to predict the likeliness of an infection, of an invasive infection, and the clinical outcome. Molecular criteria such as spa type or Panton-Valentine leukocidin positivity used for classifying MRSA as either belonging to a community or hospital clone are of limited value to indicate the setting, where the MRSA strain was actually acquired according to epidemiologic criteria.