E. Padilla

Evaluation of a rapid immunochromatographic assay for the detection of Legionella antigen in urine samples.

Abstract A new immunochromatographic membrane assay for detecting Legionella pneumophila serogroup 1 antigen in urine samples (Binax Now Legionella Urinary Antigen Test; Binax, USA) was evaluated. Its sensitivity, specificity and level of agreement with the Binax enzyme immunoassay were compared using nonconcentrated and concentrated urine samples. The overall agreement between the two tests was 98.1%; the specificity of both was 100%. The sensitivity of the immunochromatographic assay was 55.5% in nonconcentrated urine and 97.2% in concentrated urine in comparison with the enzyme immunoassay, using concentrated urine as the reference test. This immunochromatographic assay screens successfully for Legionella pneumophila serogroup 1 soluble antigen in concentrated urine samples.

Comparative Evaluation of the New Version of the INNO-LiPA Mycobacteria and GenoType Mycobacterium Assays for Identification of Mycobacterium Species from MB/BacT Liquid Cultures Artificially Inoculated with Mycobacterial Strains

ABSTRACT The performance of two DNA line probe assays, a new version of INNO-LiPA Mycobacteria (Innogenetics, Ghent, Belgium) and the GenoType Mycobacterium (Hain Diagnostika, Nehren, Germany), were evaluated for identification of mycobacterial species isolated from liquid cultures. Both tests are based on a PCR technique and designed for simultaneous identification of different mycobacterial species by reverse hybridization and line probe technology. The INNO-LiPA Mycobacteria v2 targeting the 16S-23S rRNA gene spacer region was developed for the simultaneous identification of 16 different mycobacterial species. The GenoType Mycobacterium, which targets the 23S rRNA gene, allows simultaneous identification of 13 mycobacterial species. Both tests were evaluated on 110 mycobacterial strains belonging to 22 different mycobacterial species (20 reference strains, 83 clinical strains, and 4 Mycobacterium kansasii strains isolated from tap water) that were previously inoculated into MB/BacT bottles. The sensitivity of both methods, defined as the number of positive results obtained with the Mycobacterium genus probe together with an interpretable result on the number of samples tested was 110 of 110 (100%) for INNO-LiPA and 102 of 110 (92.7%) for GenoType. For samples with interpretable results, INNO-LiPA was able to correctly identify 109 of 110 samples (99.1%), whereas the GenoType correctly identified 100 of 102 samples (98.0%). Both tests were easy to perform, rapid, and reliable when applied to mycobacterial identification directly from MB/BacT bottles.

Role of immunosuppression in the evolution of Legionnaires' disease.

The clinical course of legionella pneumonia in immunosuppressed patients is uncertain. This study was undertaken to determine the clinical evolution of legionellosis on the basis of the immune state and to establish the variables associated with death directly related to legionellosis. The study included 78 patients: 28 with chronic disease who had received immunosuppressive treatment (group 1), 24 with chronic disease without immunosuppressive treatment (group 2), and 26 controls. Inclusion criteria were the occurrence of nosocomially acquired pneumonia, Legionella pneumophila infection, and erythromycin therapy that was initiated within 72 hours following diagnosis. Respiratory and extrarespiratory complications were observed more frequently in groups 1 and 2. Bilateral radiological involvement was most frequent in group 1, and recurrence of legionella pneumonia was observed exclusively in group 1. None of these variables achieved statistical significance. The global mortality of the series was 11.5% (17.9%, 12.5%, and 3.8% in groups 1, 2, and 3, respectively). Variables statistically related to mortality were acute renal failure, shock, and need for mechanical ventilation. Although many of the variables analyzed lacked statistical significance, a trend was seen between complications and basal immunosuppression, as previously suggested.

Evaluation of a Commercial Probe Assay for Detection of Rifampin Resistance in Mycobacterium tuberculosis Directly from Respiratory and Nonrespiratory Clinical Samples

A commercial assay (Inno-Line Probe Assay; Innogenetics, Belgium) was evaluated to determine its ability to detect rifampin resistance inMycobacterium tuberculosis directly from clinical specimens. Fifty-nine selected specimens (42 respiratory and 17 nonrespiratory) culture positive forMycobacterium tuberculosis were tested along with their corresponding isolates in culture. The results were compared with those obtained by in vitro susceptibility testing. The results of the line probe assay to detect rifampin resistance inMycobacterium tuberculosis present in clinical specimens and in cultured isolates were concordant for 58 of 59 (98.3%) isolates (95% confidence limits = 90.9–99.9%). The line probe assay failed only once, when a fecal specimen was tested; no amplification was observed due to the presence of inhibitory compounds. The most frequently observed mutation was His526→Asp (58.7%), followed by the His526→Tyr (23.9%); together, they represented 82.6% of rifampin-resistant samples. In conclusion, the Inno-Line Probe Assay is a rapid, useful method for detecting the presence ofMycobacterium tuberculosis complex and its resistance to rifampin directly from clinical specimens and culture. Moreover, since rifampin resistance is a potential marker for multidrug resistance inMycobacterium tuberculosis, this assay may constitute an important tool for the control of tuberculosis.

Evaluation of a Fluorescence Hybridisation Assay Using Peptide Nucleic Acid Probes for Identification and Differentiation of Tuberculous and Non-Tuberculous Mycobacteria in Liquid Cultures

Abstract The performance was evaluated of a fluorescence in situ hybridisation assay using peptide nucleic acid probes (Dako Probe MTB Culture Confirmation Test; Dako, Denmark) for identification of Mycobacterium tuberculosis complex (MTC) organisms and differentiation between tuberculous and non-tuberculous mycobacteria (NTM) in material taken directly from Bactec 12B (Becton Dickinson, USA) and MB/BacT (Organon Teknika, USA) bottles. The test was applied to 129 smear-positive (Ziehl-Neelsen stain) clinical specimens, 48 previously identified clinical strains of mycobacteria (12 MTC and 36 NTM), and 51 reference strains (7 MTC and 44 NTM) which were all previously inoculated into Bactec 12B and MB/BacT bottles. The sensitivity and specificity of the assay for MTC-positive cultures was 87.6% and 100%, respectively, for Bactec 12B, and 100%, respectively, for MB/BacT. The sensitivity and specificity of the assay for NTM-positive cultures was 100% for both media.

Comparative evaluation of two commercial assays for direct detection of Mycobacterium tuberculosis in respiratory specimens.

Two commercial systems for the amplification and detection ofMycobacterium tuberculosis directly from respiratory samples were compared. The Roche Cobas Amplicor MTB Test and the Roche manual Amplicor MTB Test (Roche Diagnostic Systems, USA) were applied to 755 decontaminated respiratory specimens collected from 470 patients. Results were compared with those of acid-fast staining and culture. A total of 251 specimens were collected from 156 patients diagnosed with pulmonary tuberculosis, including 28 specimens corresponding to 13 patients that were receiving antituberculous treatment. Given the overall positivity rate of 33.2% (251/755), the sensitivity, specificity, and positive and negative predictive values were 92.4, 100, 100, and 96.5%, respectively, for the Cobas Amplicor MTB Test and 90.8, 100, 100, and 95.8%, respectively, for the Amplicor MTB Test. For 204 (81.3%) smear positive specimens and 47 (19.7%) smear negative specimens, the sensitivity values were 100 and 59.6%, respectively, for the Cobas Amplicor MTB Test and 100 and 51%, respectively, for the Amplicor MTB Test. There were no statistically significant differences in sensitivity or specificity between the two assays and culture (p>0.05). The overall results of both assays were concordant for 99.5% of the samples. It is concluded that although both nucleic acid amplification methods are rapid and specific for the detection ofMycobacterium tuberculosis complex in respiratory specimens, the Cobas Amplicor MTB Test appears to be slightly more sensitive than the Amplicor MTB Test when smear negative specimens are investigated.

Comparison of a Nonradiometric System with Bactec 12B and Culture on Egg-Based Media for Recovery of Mycobacteria from Clinical Specimens

Abstract The MB/BacT (Organon-Teknika, USA) is a fully automated, rapid, nonradiometric system for the culture of mycobacteria from clinical samples. The rate of recovery of mycobacteria and the time to detection obtained with the MB/BacT were compared with those obtained with Löwenstein-Jensen and Coletsos solid media and Bactec 7H12 (12B) (Becton-Dickinson, USA) broth when 600 processed specimens were inoculated into all media in parallel. Specimens included 383 respiratory samples, 20 urine samples, 23 purulent exudates, 13 stool samples, 103 blood samples, 14 bone marrow aspirates, and 44 body fluid samples or aspirates. Overall, 106 mycobacterial isolates comprising six species were recovered, of which 100 (94.3%) were detected with MB/BacT, 98 (92.5%) with egg-based media, and 96 (90.2%) with Bactec 12B. The recovery rates of Mycobacteriumtuberculosis complex with MB/BacT, egg-based media, and Bactec 12B were 98.7%, 93.7, and 89.9%, respectively. The average number of days to detection of single mycobacterial isolates was 14.2 days for MB/BacT, 26.1 days for egg-based media, and 11.7 days for Bactec 12B. The contamination rates were higher in MB/BacT (5%) than in Bactec 12B (1.8%) or egg-based media (1.5%). MB/BacT is a reliable, nonradiometric, less labor-intensive alternative to Bactec 12B for recovery of mycobacteria, but, as with other liquid culture methods, MB/BacT should be used in combination with a solid medium, not on its own.

Clinical usefulness of total hepatitis C virus core antigen quantification to monitor the response to treatment with peginterferon alpha-2a plus ribavirin*.

Summary.  Early virological response may predict outcome following treatment with peginterferon alpha‐2a and ribavirin in patients chronically infected with hepatitis C virus (HCV). As total HCV core antigen may constitute an alternative direct marker to HCV RNA for assessing the levels of viraemia in such patients, we evaluated the correlation between HCV core antigen and HCV RNA, and whether HCV core antigen at baseline, 4 and 12 weeks after treatment could predict sustained virological response (SVR) to combined therapy, in comparison with HCV RNA.

Comparison of the sodium dodecyl sulfate-sodium hydroxide specimen processing method with the C18-carboxypropylbetaine specimen processing method using the MB/BacT liquid culture system.

The ability of physicians to diagnose tuberculosis is impacted by the use of smear and culture techniques combined with specimen processing methods. The objective of this study was to evaluate the effects of specimen processing on smear and culture sensitivity by comparing the specimen processing method that uses C18-carboxypropylbetaine with the method that combines sodium dodecyl sulfate and sodium hydroxide. A total of 1,201 specimens were entered into this study. Specimens were split approximately equally such that one-half of each specimen was processed with sodium dodecyl sulfate-sodium hydroxide, while the other half was processed with C18-carboxypropylbetaine. All sediments were subjected to acid-fast staining and then analyzed using the MB/BacT liquid culture system (bioMérieux, France) and solid media. The sensitivity of smear following processing with sodium dodecyl sulfate-sodium hydroxide and C18-carboxypropylbetaine was 61.2% and 58.6% (P>0.05), respectively, while the specificities were identical (99.7%). The sensitivity of culture was 84.2% and 96.1% (P<0.05), respectively. The time to detection in the MB/BacT liquid culture system was 13.2±5.6 and 15.0±8.8 days (P>0.05), respectively, and 20.0±7.6 and 15.7±8.9 days (P<0.05), respectively, on solid media. The contamination rates in the MB/BacT system were 0.8% and 8.7%, respectively, whereas the contamination rates on solid media were 2.6% and 4.3%, respectively. C18-carboxypropylbetaine specimen processing was less labor-intensive than sodium dodecyl sulfate-sodium hydroxide processing and improved the ability of laboratory staff to detect the presence of mycobacteria by culture.

Rapid Detection of Several Mycobacterial Species Using a Polymerase Chain Reaction Reverse Hybridisation Assay

Abstract. The ability of a polymerase-chain-reaction-based technique combined with a reverse hybridisation line-probe assay to detect and identify eight of the most clinically significant mycobacterial species directly from cultures in liquid medium was evaluated. The line-probe assay allows simultaneous identification of eight different mycobacterial species. Ninety-seven mycobacterial strains belonging to 22 different species were evaluated. All strains were previously inoculated into MB/BacT bottles (Organon Teknika, USA). The sensitivity and specificity of the test when applied on positive MB/BacT liquid cultures containing isolates from mycobacterial species included as specific probes on the line-probe assay strip was 100% and 100%, respectively. These results further support the potential clinical usefulness of this technique in the diagnosis of mycobacterial infections.