MRSA Causing Infections in Hospitals in Greater Metropolitan New York: Major Shift in the Dominant Clonal Type between 1996 and 2014

Abstract

A surveillance study in 1996 identified the USA100 clone (ST5/SCCmecII)-also known as the "New York/Japan" clone-as the most prevalent MRSA causing infections in 12 New York City hospitals. Here we update the epidemiology of MRSA in seven of the same hospitals eighteen years later in 2013/14. Most of the current MRSA isolates (78 of 121) belonged to the MRSA clone USA300 (CC8/SCCmecIV) but the USA100 clone-dominant in the 1996 survey-still remained the second most frequent MRSA (25 of the 121 isolates) causing 32% of blood stream infections. The USA300 clone was most common in skin and soft tissue infections (SSTIs) and was associated with 84.5% of SSTIs compared to 5% caused by the USA100 clone. Our data indicate that by 2013/14, the USA300 clone replaced the New York/Japan clone as the most frequent cause of MRSA infections in hospitals in Metropolitan New York. In parallel with this shift in the clonal type of MRSA, there was also a striking change in the types of MRSA infections from 1996 to 2014.

Fig 1. Geographic location of hospitals that participated in the two surveillance studies.

Numbers from I to XII represent the 12 hospitals that collaborated with the Rockefeller University in the 1996 surveillance study and circled in gray are the 8 hospitals that collaborated again in 2013/14. Hospital XIII was added to the participating hospitals in 2013/14.

Fig 2. Change in the clinical sources of MRSA from 1996 to 2014.

‘Respiratory tract’: lower respiratory tract (including sputum and bronch-alveolar lavage) and sinusitis and pleural fluid. ‘Other’: any other biological specimen from which MRSA was isolated at any of the hospitals including the urinary tract, cerebro-spinal fluid, synovial fluid, placental biopsy and unlisted specimens.

Fig 3

PFGE profiles of hospital isolates representing the major clonal types of MRSA identified in the 1996 (A) and the 2013/14 study (B). (A) PFGE of USA100 isolates in 1996 [2]. (B) PFGE of USA300 isolates in 2013/14. Migration on TBE-agarose gel after digestion with SmaI restriction enzyme. USA100 (‘New York/Japan’) was the predominant clone in 1996, and the second most frequent clone in 2013–14. The roman numbers on each strain indicate the hospital in which they were isolated.