Bacterial isolation was performed both in effusionof the paranasal sinuses (PNS) obtained by a YAMIK sinus catheter and in the nasal cavity on the same side in cases with chronic sinusitis. These cases had not been treated by antibiotics at least for one week. The incidence of isolated bacteria was not remarkably different between in the effusion of PNS and in the middle nasal meatus. In 32.1% cases, the bacterial flora of the effusion of PNS coincided with that in the middle nasal meatus. The 54.5% of aerobic pathogenic bacteria detected in the effusion of PNS coincided with that detected in the middle nasal meatus.
We classified these cases into 2 groups dependingon the result of this bacteriological examination ; in Group 1 apparent pathogenic bacteria were isolated, in Group 2 nonpathogenic bacteria were isolated or no bacteria grew. While improved-case ratio in Group 1 was only about 54.5%, that in Group 2 was about 70.6%. It suggested that another recovery system exsist in upper air way disorder except for the effect by antibiotics. Drainage of effusion of PNS was shown to be one of the most important factors in the treatment of sinusitis in this study.