Single-run, parallel detection of DNA from three pneumonia-producing bacteria by real-time polymerase chain reaction.

A molecular assay for parallel detection of three bacteria, Chlamydia (C.) pneumoniae, Legionella (L.) spp., and Mycoplasma (M.) pneumoniae, in clinical specimens by a set of real-time polymerase chain reactions (PCRs) in a single run was evaluated. Bacterial DNAs were extracted by an automated DNA extraction protocol on the MagNA Pure LC System. Amplification and detection were done by real-time PCR on the LightCycler (LC) instrument. For amplification, specific oligonucleotides derived from the 16s rRNA genes of C. pneumoniae, L. spp., and M. pneumoniae were used. The three assays were complemented with an internal control (IC), a specially designed DNA fragment which contains the specific primer binding sites for the three PCRs. The IC was added to the samples, co-extracted, and co-amplified. Primers and hybridization probes were designed to suit one LC PCR program. LC PCRs were established, detection limits were determined, and clinical samples were tested. The detection limits were found between 5.0 and 0.5 IFU/CFU per PCR reaction for each of the bacteria. A total number of 100 clinical specimens were tested for validation of the molecular assay. Tested samples included 63 bronchoalveolar lavages (BALs) and 37 induced sputa specimens. The internal control was detected in all negative and low-positive samples; no inhibition was found throughout the whole study. Additionally, samples underwent testing by culture for L. spp., and M. pneumoniae; for C. pneumoniae, the serological microimmunofluorescence (MIF) test was used. In conclusion, the developed set of LC PCR assays permits parallel detection of C. pneumoniae, L. spp., and M. pneumoniae in a single LC run. This molecular assay may lead to accurate and early diagnosis of pneumonia produced by these three types of bacteria. The assay proved to be suitable for the high-throughput routine diagnostic laboratory.

Rapid diagnosis of adenoviral keratoconjunctivitis by a fully automated molecular assay.

OBJECTIVE: To establish and evaluate a new test system for rapid detection and diagnosis of adenoviral keratoconjunctivitis. DESIGN: After establishment of the molecular assay, 52 conjunctival smears were studied. PARTICIPANTS: Samples were derived from patients with a clinical presentation compatible with keratoconjunctivitis. METHODS: A molecular assay for detection of human adenovirus (HAdV) based on automated nucleic acid extraction and real time polymerase chain reaction was established and evaluated. The new assay included a heterologous internal control. MAIN OUTCOME MEASURES: Statement about the presence or absence of adenoviral DNA in the specimen. RESULTS: The amplification efficiency was found to be 100%. The detection limit was calculated to be 116 copies per LightCycler capillary. When clinical specimens were tested, 15 of 52 conjunctival smears were found to be positive for HAdV DNA. The internal control was detected in all samples. CONCLUSIONS: The new molecular assay proved to be suitable for rapid diagnosis of adenoviral keratoconjunctivitis in the routine diagnostic laboratory.

Detection of transfusion transmitted virus DNA by real-time PCR.

BACKGROUND: Little is known about the pathogenic role and the endemic situation of transfusion transmitted virus (TTV). OBJECTIVES: In this study, a molecular assay for detection of TTV based on automated nucleic acid extraction and real-time PCR was developed and evaluated. The new assay includes an internal control. STUDY DESIGN: After optimization of the molecular assay, 103 clinical samples were studied retrospectively. All sera had been tested for anti-HCV and anti-HIV-1 antibodies earlier. RESULTS: The amplification efficiency was found to be 102%. When clinical specimens were tested, 79 of 103 serum samples were found to be positive for TTV. There was no significant difference between various groups of patients. The internal control was detected in all negative and weak positive samples. CONCLUSIONS: This molecular assay proved to be suitable for routine detection of TTV in clinical samples. Moreover, a relative statement on the TTV serum load can be done.

Rapid detection of enterovirus infection by automated RNA extraction and real-time fluorescence PCR.

BACKGROUND: Molecular detection has been shown to be superior to tissue culture for the detection of enteroviruses in cerebrospinal fluid (CSF) specimens. OBJECTIVES: In this study, a qualitative molecular assay based on automated RNA extraction with the MagNA Pure LC and real-time PCR on the LightCycler (LC) instrument was evaluated and compared with an in-house molecular assay. STUDY DESIGN: A total of 109 CSF specimens were investigated for the comparative study. The detection limit of the new molecular assay was determined with 10-fold dilutions of two enterovirus strains and with the Third European Union Concerted Action Enterovirus Proficiency Panel. RESULTS: With the enterovirus strains, the detection limit of the LC assay was found to be 0.1 TCID(50) (50% tissue culture infective dose). When samples of the Third European Union Concerted Action Enterovirus Proficiency Panel were tested, both molecular assays gave identical results to the expected results, which were based upon the results of three reference laboratories using a total of four different molecular methods before distribution of the panel. When clinical specimens were tested, there was a correlation between the LC assay and the in-house assay in 105 of 109 cerebrospinal fluids. CONCLUSIONS: The new molecular assay allows rapid detection of enterovirus RNA in CSF. It was found to be labor saving and showed sufficient sensitivity.

Detection of methicillin-resistant Staphylococcus aureus and simultaneous confirmation by automated nucleic acid extraction and real-time PCR.

A molecular assay for the simultaneous detection of a Staphylococcus aureus-specific gene and the mecA gene, responsible for the resistance to methicillin in staphylococci, was evaluated. The assay included an automated DNA extraction protocol conducted with a MagNA Pure instrument and real-time PCR conducted with a LightCycler instrument. The performance and robustness of the assay were evaluated for a suspension of methicillin-resistant S. aureus (MRSA) strain with a turbidity equivalent to a McFarland standard of 0.5, which was found to be the ideal working concentration. The specificity of the new molecular assay was tested with a panel of 30 gram-negative and gram-positive bacterial strains other than MRSA. No cross-reactivity was observed. In a clinical study, 109 isolates of MRSA were investigated. All clinical MRSA isolates gave positive results for the S. aureus-specific genomic target, and all but one were positive for the mecA gene. In conclusion, the new molecular assay was found to be quick, robust, and laborsaving, and it proved to be suitable for a routine molecular diagnostic laboratory.

Fully automated detection of hepatitis C virus RNA in serum and whole-blood samples.

In this study, we established a fully automated molecular assay for qualitative detection of hepatitis C virus (HCV) in serum and whole-blood samples and compared it with conventional molecular assays, including manual HCV RNA extraction protocols. Whole-blood samples were collected from patients with and without chronic HCV infection in EDTA tubes and nucleic acid stabilization tubes (NASTs). Prior to HCV RNA extraction, the HCV Internal Control (IC), derived from the COBAS AMPLICOR HCV test, version 2.0 (Roche Molecular Diagnostics), was added. The new assay was based on an automated extraction protocol on the MagNA Pure LC instrument (Roche Applied Science), followed by automated reverse transcription, amplification, hybridization, and detection on the Cobas Amplicor analyzer (Roche Molecular Diagnostics). The detection limit of the new assay was found to be similar to those of conventional molecular assays. In clinical samples, 100% agreement between the new assay and conventional methods was observed. The introduced amount of IC was detected in 45 of 45 serum samples, 41 of 45 EDTA tube whole-blood samples, and 43 of 45 NAST whole-blood samples. Retesting led to more frequent IC detection. The fully automated molecular assay was found to be suitable for detection of HCV RNA in different kinds of sample materials. It may be recommended for use in the high-throughput routine molecular diagnostic laboratory.