Detection of bacterial DNA in serial synovial samples obtained during antibiotic treatment from patients with septic arthritis

Objective. The management of septic arthritis could benefit from sensitive tests that detect the persistence of microorganisms in the joint. The aim o f this study was to determine the feasibility of monitoring the presence of bacterial DNA in synovial samples from septic arthritis patients during an tibiotic treatment. Methods. Synovial fluid (SF) and synovial tissue (ST) samples were collecte d serially from 6 patients with septic arthritis before and during antibiot ic therapy. In addition, peripheral blood (PB) samples were available for p olymerase chain reaction (PCR) analysis from 5 of the 6 patients before tre atment. All samples were analyzed for the presence of bacterial DNA with th e use of a PCR with universal 16S ribosomal RNA primers, Automated sequenci ng and comparative data analysis were performed to identify the species. Th ese data were compared with Gram staining and culture results, Results. The bacterial species cultured from the synovium could be identifi ed in all 6 patients using PCR and subsequent sequence analysis of the ampl icons. In virtually all cases, positive Gram stain and culture findings in the synovial samples became negative after 2-3 days of antibiotic treatment . Bacterial DNA persisted in the SF and/or ST after culture conversion; in 2 patients, bacterial DNA was still detected at day 10, in 1 patient, at da y 20, and in another patient, at day 22 after the initiation of treatment. Synovial samples were available for PCR analysis from 2 patients at day 26. At this time point, bacterial DNA could not be detected anymore. All PB sa mples were negative by both culture and PCR analysis. Conclusion. PCR analysis can be used to monitor the presence of bacterial D NA in synovial samples from patients with septic arthritis during antibioti c treatment. The absence of bacterial DNA could help in the decision to dis continue antibiotic treatment.