Distribution of methicillin-resistant Staphylococcus aureus clones among health care facilities in Connecticut, New Jersey, and Pennsylvania. .

A previous surveillance study conducted in 12 hospitals in New York City in 1996 identified a unique multidrug-resistant genetic lineage of methicillin-resistant Staphylococcus aureus (MRSA) that was widespread and accounted for as much as 42% of all the MRSA isolates. The purpose of the study described here was to determine possible geographic spread of this New York clone of MRSA to neighboring states. Single-patient MRSA isolates (258) from 29 health care facilities in Connecticut (CT), New Jersey (NJ), and Pennsylvania (PA) were collected during the calendar year 1998. DNA typing, consisting of fingerprinting of chromosomal macrorestriction patterns generated by SmaI digestion followed by pulsed-field gel electrophoresis (PFGE), identified 22 patterns. PFGE type A, closely related to the PFGE type of the previously identified New York clone, accounted for 154 (60%) of 258 isolates. The clone was detected in all facilities, was predominant in 19 of the 29 health care centers, and accounted for 92% of the MRSA isolates collected in PA. The overwhelming majority of MRSA with PFGE type A was also resistant to erythromycin, ciprofloxacin, and clindamycin. One of the two most common PFGE subtypes detected in the three states sampled (PFGE subtype A1) had an identical PFGE pattern to that of the previously described vancomycin-resistant strain of S. aureus (VISA) recently detected in a hospital in Westchester, NY. The second most frequent MRSA clone with PFGE type E and accounting for 26% (68/258 isolates), also described earlier in the 12 New York City hospitals, was resistant not only to erythromycin, ciprofloxacin, and clindamycin, but also to gentamicin and sulfamethoxazole-trimethoprim as well. The unique multidrug resistance pattern of this second clone and its geographic distribution accounted for the differences observed in the frequency of multidrug resistance among MRSA isolates recovered in the three states. The pandemic Iberian clone recently detected in New York City was not detected among the 258 MRSA isolates recovered in CT, NJ, and PA.