[Bacteriology of infectious disease in otorhinolaryngology (1). Bacteriological study of paranasal cyst]

The bacteriology of chronic sinusitis has been reported in several studies, but there have been few bacteriological studies on paranasal cyst. Also, details of the techniques of transportation and processing of clinical specimens have only rarely been described. Therefore, this study was undertaken with attention to the above, and to obtain information on appropriate antimicrobial therapy, we conducted a dilution antimicrobial susceptibility test of isolates. Fifteen patients with paranasal cyst participated in this study. Their lesions were frontal sinus (3), ethmoid sinus (2), sphenoid sinus (2) and maxillary sinus (8). We punctured the cyst using an 18-gauge needle attached to a syringe at the time of operation, and paranasal cyst effusions were promptly transported to the laboratory. The specimen was immediately inoculated under a set of aerobic and prereduced anaerobic plates, which were incubated in appropriate conditions. Most specimens were completely processed within one hour. Antimicrobial susceptibility testing of isolates was done with MIC panel by the Sceptor system. Positive results of bacterial cultures were found in 60% of all cases (all of the frontal sinus specimens and half of those with other lesions). A total of 38 bacteria, including 24 anaerobic and 14 aerobic species, were isolated from 9 paranasal cysts, yielding an average of 4.2 species per positive case (2.9 anaerobes and 1.3 aerobes). Monomicrobial flora were found, anaerobes only in 2 cases and aerobes only in 2 others. Mixed flora were found in 5 cases in which both anaerobes and aerobes were isolated. The bacterial concentration in the maximal case was 4.9 x 10(4) CFU/ml. The organisms most frequently isolated were Propionibacterium spp. (7), Peptostreptococcus spp. (7), Staphylococcus spp. (7), Prevotella spp. (5) and Streptococcus spp. (4). On the basis of the results of antimicrobial susceptibility testing of isolates in vitro, the use of Cephems, Clavulanic acid/Amoxicillin, Norfloxacin and Chloramphenicol proved to be clinically effective.