PURPOSE: To test the utility of DNA Taq polymerase (Taq) treated with 8-methoxypsoralen with ultraviolet irradiation and Taq treated with restriction endonuclease in a nested polymerase chain reaction test for the diagnosis of bacterial endophthalmitis.

METHODS: Prospective, comparative study. Vitreous biopsy fluid from 32 cases of clinically diagnosed bacterial endophthalmitis and 10 noninfective controls were cultured for aerobic/anaerobic bacteria and tested by nested polymerase chain reaction using two sets of universal eubacterial primers in triplicate with untreated Taq, Taq treated with 8-methoxypsoralen with ultraviolet irradiation, and Taq treated with Sau 3A1.

RESULTS: Using untreated Taq, false-positive results were obtained in nested polymerase chain reaction with all 10 control samples, which were not seen with the other two methods of nested polymerase chain reaction. However, the senstivity of nested polymerase chain reaction using Sau 3A1 was the same sensitivity as the conventional culture (34.4%), whereas the sensitivity of the nested polymerase chain reaction using 8-methoxypsoralen was 46.9% higher than in the conventional culture.

CONCLUSION: To eliminate the problem of false positives in bacterial nested polymerase chain reaction, we recommend the routine utilization of Taq treated with 8- methoxypsoralen and ultraviolet irradiation.