Preoperative, intraoperative, and postoperative results of bacterial culture from patients with chronic suppurative otitis media.

BACKGROUND: Cultures obtained from preoperative middle ear swabs from patients with chronic suppurative otitis media (CSOM) have traditionally been used to guide antibiotic selection. However, little is known about changes in the bacterial flora during surgery.
OBJECTIVE: To analyze preoperative, intraoperative, and postoperative bacterial cultures of CSOM patients who underwent tympanomastoidectomy.
METHODS: We retrospectively reviewed the medical records of 244 patients (113 male and 131 female subjects; 252 ears) diagnosed with CSOM between January 2006 and December 2008. Middle ear swabs and mastoid granulation tissue were collected preoperatively and intraoperatively, respectively. We also cultured middle ear swabs from patients with postoperative otorrhea.
RESULTS: The most commonly identified preoperative pathogenic bacterial species was methicillin-resistant Staphylococcus aureus (MRSA). There were no statistical differences in prevalence of preoperative bacterial pathogens between patients with and without cholesteatoma. No bacteria were observed in 34.1% of preoperative or 76.6% of intraoperative cultures. Patients preoperatively positive for coagulase-negative Staphylococcus, S. aureus, or Pseudomonas aeruginosa remained positive intraoperatively. Of the patients preoperatively negative for bacteria and those positive for fungi, 6.9% and 20.0%, respectively, were positive for bacteria, including MRSA, intraoperatively. Of the patients that were preoperatively positive for bacteria, 16.7% to 50.0% was intraoperatively positive for different pathogens from previous results. Patients with postoperative otorrhea yielded the highest culture rates of MRSA, preoperatively, intraoperatively, and postoperatively.
CONCLUSION: Although the similarities between preoperative and intraoperative culture results were relatively high, remaining or different pathogens also may have been present from intraoperative mastoid granulation tissue culture. Patients with preoperative MRSA were at high risk of postoperative otorrhea.