Trends and antibiotic susceptibility patterns of methicillin-resistant and methicillin-sensitive Staphylococcus aureus in an outpatient dermatology facility.

OBJECTIVES To determine whether the relative proportions of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) were changing or stable in an outpatient dermatology clinic and to examine the antibiotic susceptibility profiles of S aureus isolates. DESIGN Retrospective observational data were collected from skin culture isolates annually between January 1, 2005, and December 31, 2010, and monthly during the 6-month period of January 1, 2011, to June 30, 2011. SETTING The University of Miami Hospital outpatient dermatology clinic. PARTICIPANTS A total of 387 S aureus isolates were analyzed between January 1, 2005, and June 30, 2011, from adult and pediatric patients. MAIN OUTCOME MEASURES The relative proportions of MRSA and MSSA skin culture isolates were measured, along with antibiotic sensitivity profiles. RESULTS The overall relative proportion of MRSA was 35.7%. The overall relative proportion of MSSA was 64.3%. During the last 6 months of the study, the relative proportion of MRSA was 33.3%, while the relative proportion of MSSA was 66.7%. The relative proportion of MRSA from January 1, 2008, through December 31, 2010, was significantly higher than the relative proportion from January 1, 2005, through December 31, 2007 (45.3% vs 28.3%, P = .001). MRSA became more sensitive to ciprofloxacin, while MSSA became more resistant to ciprofloxacin, clindamycin, gentamicin sulfate, and trimethoprim-sulfamethoxazole. CONCLUSIONS The relative proportion of MRSA in the S aureus isolates increased by 17.0% during the last 3 years of our study. Despite this increase, MRSA became more sensitive to ciprofloxacin, while MSSA demonstrated increased antibiotic resistance to ciprofloxacin, clindamycin, gentamicin, and trimethoprim-sulfamethoxazole.