Microbiology of surgical site infections complicating breast surgery

Surgical site infection (SSI) rates complicating breast surgery have ranged from 1-26%, but limited data have been provided regarding pathogen identification and in vitro susceptibility results. The aim of this study was to evaluate the results of bacterial cultures of breast SSI sites and antibiotic susceptibility testing to determine the clinical utility of these findings.

Medical records were reviewed for SSI in patients who had undergone breast/axillary surgical procedures between June 2003 and June 2006. An SSI was defined by the criteria of the U.S. Centers for Disease Control and Prevention. Clinical data were collected on perioperative prophylactic antibiotics, organisms isolated, and resistance profiles.

A total of 832 breast/axillary operations in 683 patients were included. Material was available for culture in 67/144 SSI (47%), but cultures were obtained from only 41 of these sites (61%). There were 25 sites with positive bacterial cultures from which 35 organisms were isolated. Staphylococci were the organisms isolated most commonly (n = 21; 60%); 14 other isolates (40%) included gram-negative bacilli and anaerobes. Susceptibility testing was performed on 16 (76%) of the staphylococcal isolates. Ten (63%) exhibited drug resistance; five were multi-drug resistant. Six of eight non-staphylococcal isolates tested (75%) exhibited antibiotic resistance; two were multi-drug resistant.

Although the usual empiric treatment of SSI after breast surgery targets staphylococci, cultures with susceptibility profiles should be obtained because non-staphylococcal bacteria were commonly identified, and drug resistance was seen in more than one-half of the isolates. Further study is needed to define the optimal empiric antibiotic therapy for SSI after breast surgery.