Background: To date, there is an increasing trend of prescribing antibiotics that cover -lactamase - producing
bacteria as the first line drug for sinusitis patients in Thailand. This practice dose not only increases the treatment cost but might also induce resistance to antimicrobial agents.
Objective: To determine the prevalence of the pathogenic bacteria in acute and chronic maxillary sinusitis as well as the prevalence of -lactamase - producing bacteria.
Material and Method: The maxillary aspiration fluid specimens of 52 acute and chronic sinusitis patients at Phramongkutklao Hospital, Bangkok, Thailand during May 2002-May 2003, were collected. Aerobic and anaerobic cultures were performed and the -lactamase activities of isolated bacteria were determined.
Results: Of 58 specimens, 44 (75.9%) and 14 (24.1%) specimens were collected from acute and chronic maxillary sinusitis patients, respectively. Of 44 specimens of acute maxillary sinusitis, the predominant isolates were Haemophilus influenzae (13, 29.5%), Streptococcus pneumoniae (4, 9%), Streptococcus viridan (4, 9%), and Klebsiella pneumoniae (4, 9%). 6 (13.6%) of them were β-lactamase - producing bacteria. Of 14 specimens of chronic maxillary sinusitis, the predominant isolates were Pseudomonas aeruginosa (3, 16.6%), Staphylococcus spp (3, 17.5%) and Streptococcus spp. (2, 11.6%). 1 (7.1%) Haemophilus influenza isolate from this group was β-lactamase - producing bacteria. The percentage of anaerobe was 8.9%, 23.3% for acute and chronic maxillary sinusitis, respectively.
Conclusion: The present study was indicated that the common organisms in acute maxillary sinusitis were Haemophilus influenzae and Streptococcus pneumoniae, Streptococcus viridians which were similar to a previous study. But the authors found an increased prevalence of anaerobe bacteria in acute maxillary sinusitis and also found -lactamase- producing bacteria, 21.4% Hemophilus influenzae less than the previous
studies (which found -lactamase - producing bacteria around 50% to 70%). The authors found 23.3% anaerobe bacteria in the chronic maxillary sinusitis, less than the previous studies, and the authors also found 8.9% anaerobe in acute maxillary sinusitis

Keywords: Acute and chronic maxillary sinusitis, -lactamase - producing bacteria