Objective: To examine: 1) types of bacteria and antimicrobial sensitivity of commonly used antibiotics for acute bacterial
rhinosinusitis (ABRS) in Thailand, 2) the effectiveness of using antibiotics according to antimicrobial sensitivity, and 3) the
effectiveness of using antibiotics according to the Thai clinical practice guidelines (CPG) of ABRS.
Material and Method: Descriptive & experimental studies were conducted in seven tertiary hospitals in Thailand. The specimens from maxillary sinuses were taken for bacterial cultures either by maxillary sinus tap or endoscopically directed middle meatus swabs in patients with clinically diagnosed ABRS. Antimicrobial sensitivity was performed and antibiotics were prescribed according to the results of antimicrobial sensitivity or the Thai CPG of ABRS.
Results: A total of 113 patients were enrolled between August 2006 and April 2007, 104 cases of which were performed for
bacteriological study. The incidence of bacterial growth was 60.6% (95% CI 51.0-69.4%). The most common bacteria was
H. influenzae (25.0%, 95% CI 16.9-35.3%), followed by S. pneumoniae (14.3%, 95% CI 8.2-23.5%) and S. aureus (9.5%,
95% CI 4.7-17.9%), respectively, whilst M. catarrhalis was found only in 2.4% (95% CI 0.5-7.3%). Eight in 12 S. pneumoniae isolates were tested for the minimal inhibitory concentration of penicillin and found to be penicillin resistant strain in five specimens. Beta-lactamase producing H. influenzae was found in eight out of 20 isolates. H. influenzae had a tendency to be sensitive to amoxicillin/clavulanate, cefuroxime, cefpodoxime, azithromycin, clarithromycin, ofloxacin, levofloxacin and gatifloxacin, whilst S. pneumoniae had a tendency to be sensitive to amoxicillin/clavulanate, cefaclor, ampicillin/sulbactam, cefuroxime, ofloxacin, levofloxacin, gatifloxacin, cefpodoxime, cefixime and cefdinir. The effectiveness of antibiotics prescription according to the Thai CPG of ABRS and antimicrobial sensitivity were comparable, 88.5% (95% CI 69.8-97.6%) and 82.2% (95% CI 67.9-92%), respectively.
Conclusion: H. influenzae is found to be the most common bacteria in Thai ABRS, followed by S. pneumoniae and S. aureus. There is a high incidence of beta-lactamase producing H. influenzae and penicillin non-susceptible S. pneumoniae.

Keywords: Acute bacterial rhinosinusitis, Bacteriology, Microbiology, Streptococcus pneumoniae, Hemophilus influenzae