Contemporary trends in microbiology and antibiotic resistance in otolaryngology

Objective: to determine current microbiologic yields and characterize antibiotic resistance patterns for organisms cultured from head and neck infections. Methods: results of out-patient cultures submitted from an academic otolaryngology practice over the period 1994–1998 were reviewed. A database was constructed, and culture results were analyzed for sites of infection, organism recovery rate, infecting microbiological agent, antibiotic resistance patterns, and 5-year trends. χ2 analysis was used to determine associations between site of infection, infecting agent and antibiotic resistance over the years of the study. Results: a total of 986 aerobic cultures were reviewed. The most common sites cultured were the nose/paranasal sinuses (469), throat (377), and ear (23). In 465 (47.2%) cultures, normal flora or no growth occurred. Of the throat culture subset, 69.7% were negative, whereas 69.1% of sinonasal cultures recovered organisms. Gram positive cocci were the most commonly recovered organism type (30.9%), followed by Gram negative rods (GNR, 17.2%). These rates remained relatively constant over the years of the study. GNR were found in 39.1 and 25.2% of ear and sinus cultures, respectively. Antibiotic sensitivities were conducted on 257 specimens (49.3% of positive cultures). The average number of antibiotic resistances per bacteria remained stable at approximately 1.59 over the years (P=0.086, analysis of variance (ANOVA)). Antibiotic resistance rates increased for clindamycin, cefazolin, and erythromycin over the years of the study (P<0.05, χ2). Ciprofloxacin, gentamicin and trimethoprim-sulfamethoxazole resistance rates did not increase over the years of the study. Vancomycin resistance did not occur. Conclusions: as a significant proportion of head and neck cultures will be negative, their utility should be re-examined. GNR infections are more common in the head and neck than earlier thought. There is a trend towards increasing antibiotic resistance in head and neck infections, urging careful and appropriate use of antibiotics.