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

Abstract

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.