Breast abscess bacteriologic features in the era of community-acquired methicillin-resistant Staphylococcus aureus epidemics

Abstract

Hypothesis: Increasing rates of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections have also affected the microbial profile of breast abscesses.

Objective: To update the decade-old bacteriologic description of breast abscesses to improve the choice of initial antibacterial drug therapy.

Design: Retrospective case series.

Setting: County hospital emergency department.

Patients: Forty-four women (mean age, 41 years; age range, 20-63 years) with breast abscesses.

Methods: All cultures from the breast abscesses of patients were reviewed.

Main outcome measures: The microbiologic features and sensitivities of breast abscesses.

Results: Of 46 specimens only 28 showed bacterial yield (61%). Of these, 11 (39%) were polymicrobial, for an average of 1.4 isolates per specimen. The most common organism was S aureus, present in 12 of 37 aerobic cultures (32%), with MRSA in 7 (58%). The remaining organisms included coagulase-negative Staphylococcus (16%), diphtheroids (16%), Pseudomonas aeruginosa (8%), Proteus mirabilis (5%), and other isolates (22%). All MRSA was sensitive to clindamycin, trimethoprim-sulfamethoxazole, and linezolid. Only 2 patients (29%) were sensitive to levofloxacin. Two anaerobic cultures were positive for Propionibacterium acnes and Peptostreptococcus anaerobius.

Conclusions: Staphylococcus aureus is the most common pathogenic organism in modern breast abscesses. Many breast abscesses have community-acquired MRSA, with more than 50% of all S aureus and 19% of all cultures being MRSA. This finding parallels the local and national increases in MRSA reported in other soft-tissue infections. With increasing bacterial resistance and more minimally invasive management of breast abscesses, understanding the current bacteriologic profile of these abscesses is essential to determining the correct empirical antibiotic drug therapy.