After mastectomy, breast reconstructive surgeries using breast tissue expander (BTE) placement have a particularly high risk of infection. Whereas previous studies showed these infections to consist of primarily gram-positive organisms, gram-negative rods consist of up to 26% of the microorganisms isolated in some studies. Here we highlight the prevalence of gram-negative rods, particularly Pseudomonas aeruginosa, in BTE infections.
We used a retrospective chart review at a comprehensive cancer center to identify BTE infections caused by gram-negative rods over a 2-yearperiod. We collected data on the organism from wound cultures and antimicrobial susceptibilities.
During this period, we isolated 38 gram-negative rod infections from BTE surgeries from a sample size of 215 organisms. The most common gram-negative rod was P. aeruginosa (44.7%), followed by Serratia marcescens (15.7%) and Klebsiella pneumoniae (7.9%). All Pseudomonas and Klebsiella isolates were susceptible to all antibiotics tested; Serratia isolates were resistant to cefazolin and cefoxitin. Significant resistance to ampicillin, cefazolin, cefoxitin, and ceftazidime was found in the organisms tested. Antipseudomonal antimicrobials, notably cefepime, piperacillin/tazobactam, ciprofloxacin, tobramycin, and gentamicin, had activity against all organisms tested.
Perioperative antimicrobial prophylaxis consisting of cefazolin often does not have activity against gram-negative rods. In addition, postoperative antibiotics often do not have activity against Pseudomonas. In our study sample, all antibiotics tested had activity against Pseudomonas. Empiric antibiotics used to treat postsurgical BTE infections should include activity against Pseudomonas.