Detecting the presence of bacterial DNA by PCR can be useful in diagnosing culture-negative cases of infection, especially in patients with suspected infection and antibiotic therapy

Failing in bacteria isolation in a significant number of infections might be due to the involvement of microorganisms non-recoverable in culture media. The presence cannot be ruled out of non-dividing cells or even bacterial products still capable of promoting a host immunological response. Antibiotic therapy, for example, might induce a block of bacterial division and the impossibility of recovering cells in culture media. In these cases, a molecular method targeting DNA should be used. In this study, 230 clinical samples with a culture-negative report obtained from 182 patients were examined with a protocol of PCR targeting the bacterial 16S rDNA gene to evaluate the usefulness of molecular methods in differencing culture-negative infections from other pathologies. Amplicons were obtained in 14% of the samples although this percentage increased (27%) in a subgroup of patients with presumptive diagnosis of infection and ongoing antibiotic therapy. By multiplex PCR it was shown that detected DNA belonged mostly to Enterobacteriaceae and enterococcal species. Multiple culture-negative, PCR-positive samples and isolation of the same bacterial species in culture in additional samples from the same patient support the clinical significance of the data obtained and highlight the complementary role and usefulness of applying molecular methods in diagnostic microbiology. This article is protected by copyright. All rights reserved.