Laboratory detection of Pseudomonas spp., particularly Pseudomonas aeruginosa, is an important assay in the nosocomial control. The study was designed firstly to establish a new assay-applied LightCycler polymerase chain reaction (PCR) technology with melting curve analysis (MCA). A total of 224 Gram-negative isolates were used to verify the assay system. The PCR with MCA method using the P. aeruginosa-specific gyrase B gene primers was rapid and accurate; the total run is approximately 3 h, and the sensitivity and specificity relative to the Vitek (bioMerieux, Hazelwood, MO) results were 98.1% and 100%, respectively. Vitek identification system was not able to identify the isolates from the new Pseudomonas otitidis spp. opposite to the real-time PCR. This assay was validated to be accurate with an overall sensitivity and specificity of 98.7% and 98.9%, respectively. Conclusively, this rapid and accurate PCR assay with MCA will help to manage and control infections with P. aeruginosa.
Rapid identification of the causative bacteria of sepsis in patients can contribute to the selection of appropriate antibiotics and improvement of patients' prognosis. Genotypic identification is an emerging technology that may provide an alternative method to, or complement, established phenotypic identification procedures. We evaluated a rapid protocol for bacterial identification based on PCR and pyrosequencing of the V1 and V3 regions of the 16S rRNA gene using DNA extracted directly from positive blood culture samples. One hundred and two positive blood culture bottles from 68 patients were randomly selected and the bacteria were identified by phenotyping and pyrosequencing. The results of pyrosequencing identification displayed 84.3 and 64.7 % concordance with the results of phenotypic identification at the genus and species levels, respectively. In the monomicrobial samples, the concordance between the results of pyrosequencing and phenotypic identification at the genus level was 87.0 %. Pyrosequencing identified one isolate in 60 % of polymicrobial samples, which were confirmed by culture analysis. Of the samples identified by pyrosequencing, 55.7 % showed consistent results in V1 and V3 targeted sequencing; other samples were identified based on the results of V1 (12.5 %) or V3 (31.8 %) sequencing alone. One isolate was erroneously identified by pyrosequencing due to high sequence similarity with another isolate. Pyrosequencing identified one isolate that was not detected by phenotypic identification. The process of pyrosequencing identification can be completed within~4 h. The information provided by DNA-pyrosequencing for the identification of micro-organisms in positive blood culture bottles is accurate and could prove to be a rapid and useful tool in standard laboratory practice.
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