Evaluation of GenoFlow DR-MTB Array Test for Detection of Rifampin and Isoniazid Resistance in Mycobacterium tuberculosis.

The aim of this study was to evaluate the GenoFlow DR-MTB array test (DiagCor Bioscience, Hong Kong) on 70 cultured isolates and 50 sputum specimens. The GenoFlow array test showed good sensitivity and specificity compared to the phenotypic Bactec 460TB. This array accurately detected mutations inrpoB,katG, andinhAassociated with resistance to rifampin and isoniazid.

GenoType MTBDRsl for molecular detection of second-line-drug and ethambutol resistance in Mycobacterium tuberculosis strains and clinical samples.

The purpose of this study was to evaluate the GenoType MTBDRsl assay (Hain Lifescience GmbH, Nehren, Germany) for its ability to detect resistance to fluoroquinolones (FLQ), injectable second-line antibiotics [kanamycin (KM) and capreomycin (CM)], and ethambutol (EMB) in Mycobacterium tuberculosis clinical strains and directly in clinical samples. A total of 34 clinical strains were characterized with the Bactec 460 TB system. Fifty-four clinical samples from 16 patients (5 were smear negative and 49 were smear positive) were also tested directly. The corresponding isolates of the clinical specimens were also analyzed with the Bactec 460TB. When there was a discrepancy between assays, pyrosequencing was performed. The overall rates of concordance of the MTBDRsl and the Bactec 460TB for the detection of FLQ, KM/CM, and EMB susceptibility in clinical strains were 72.4% (21/29), 88.8% (24/27), and 67.6% (23/34), whereas for clinical samples, rates were 86.5% (45/52), 92.3% (48/52), and 56% (28/50), respectively. In conclusion, the GenoType MTBDRsl assay may be a useful tool for making early decisions regarding KM/CM susceptibility and to a lesser extent regarding FLQ and EMB susceptibility. The test is able to detect mutations in both clinical strains and samples with a short turnaround time. However, for correct management of patients with extensively drug-resistant tuberculosis, results must be confirmed by a phenotypical method.

Pyrosequencing for rapid molecular detection of rifampin and isoniazid resistance in Mycobacterium tuberculosis strains and clinical specimens.

The aim of this study was to evaluate a pyrosequencing method for the detection of Mycobacterium tuberculosis isolates resistant to rifampin and isoniazid using both clinical strains and clinical samples, comparing the results with those of the Bactec 460TB and GenoType MTBDRplus assays. In comparison to Bactec 460TB as the gold standard, the sensitivity of pyrosequencing for detecting isoniazid and rifampin resistance was 76.9% and 97.2%, respectively, for clinical strains, and the specificity was 97.2 and 97.9%, respectively. For clinical specimens, the sensitivity and specificity for both drugs were 85.7% and 100%, respectively. The overall concordance between pyrosequencing and the GenoType MTBDRplus assay for clinical strains was 99.1%, and for clinical samples, it was 98.2%. Pyrosequencing is a valuable tool for rifampin and isoniazid resistance detection.

GenoType MTBDRplus assay for molecular detection of rifampin and isoniazid resistance in Mycobacterium tuberculosis strains and clinical samples.

The purpose of this study was to evaluate the GenoType MTBDRplus assay (Hain Lifescience GmbH, Nehren, Germany) for its ability to detect resistance to rifampin (RIF) and isoniazid (INH) in Mycobacterium tuberculosis clinical strains and directly in clinical samples. A total of 62 clinical strains characterized with the Bactec 460TB system were included. For the INH-resistant strains, the MIC was measured and sequencing was performed. Sixty-five clinical samples from 28 patients (39 smear-positive samples and 26 smear-negative samples) were also tested directly. The corresponding isolates of the clinical specimens were studied with the Bactec 460TB system. The overall rates of concordance of the MTBDRplus assay and the Bactec 460TB system for the detection of RIF and INH susceptibility in clinical strains were 98.3% (61/62) and 79% (49/62), respectively. The rate of concordance between the Bactec 460TB system and the MTBDRplus test for the detection of INH resistance in the group of 27 strains with low-level resistance was 62.9% (17/27), and that for the detection of INH resistance in the group of 21 strains with high-level resistance was 85.71% (18/21). Valid test results were obtained for 78.45% (51/65) of the clinical samples tested. The rates of concordance between both assays for the detection of drug resistance in these samples were 98% (50/51) for RIF and 96.2% (49/51) for INH. Taking into account only one sample per patient, the overall rate of concordance between both tests was 92.85% (26/28). The GenoType MTBDRplus assay is easy to perform and is a useful tool for the management of tuberculosis, as it allows the detection of resistance to RIF and INH in M. tuberculosis strains and also in clinical samples.

Evaluation of a Legionella urinary antigen enzyme immunoassay for rapid detection of Legionella pneumophila in water samples.

Despite advances in medium formulations and pretreatment techniques, recovery of Legionella from water samples can still be quite low, difficult and time consuming. The aim of this study was to evaluate the utility of a Legionella urinary antigen enzyme immunoassay (Bartels ELISA, Trinity Biotech, Ireland) for the detection of Legionella in water samples. Reference ATCC Legionella strains were used to spike water samples to a final concentration of 10(4)-10(5)cfu/ml. The lower detection limit of the test for all Legionella pneumophila serogroups was assessed by serial dilutions of spiked water samples. Legionella antigen was detected in all filtered samples except for those spiked with L. bozemanii and L. longbeachae. The lower detection limit for soluble L. pneumophila serogroup 1 antigen was 780cfu/ml. Bartels ELISA could be a useful method for antigen detection in water samples when a high recovery of L. pneumophila is suspected. The test could be used as a rapid screening method for the detection of Legionella in a large number of samples. However, the low sensitivity of the test requires to keep on performing conventional culture for isolation and for further studies on isolated bacteria.

PyroTyping, a novel pyrosequencing-based assay for Mycobacterium tuberculosis genotyping.

We developed a novel method, PyroTyping, for discrimination of Mycobacterium tuberculosis isolates combining pyrosequencing and IS6110 polymorphism. A total of 100 isolates were analysed with IS6110-restriction fragment length polymorphism (RFLP), spoligotyping, mycobacterial interspersed repetitive units - variable number tandem repeats (MIRU-VNTR), and PyroTyping. PyroTyping results regarding clustering or discrimination of the isolates were highly concordant with the other typing methods performed. PyroTyping is more rapid than RFLP and presents the same discriminatory power, thus, it may be useful for taking timely decisions for tuberculosis control.

AID TB resistance line probe assay for rapid detection of resistant Mycobacterium tuberculosis in clinical samples.

OBJECTIVES: To determine the sensitivity and specificity of AID TB Resistance line probe assay (AID Diagnostika, Germany) to detect Mycobacterium tuberculosis and its resistance to first- and second-line drugs in clinical samples using BACTEC 460TB as the reference standard. METHODS: The test consists on three strips to detect resistance to isoniazid/rifampicin, fluoroquinolones/ethambutol, and kanamycin/amikacin/capreomycin/streptomycin, respectively. This test was performed on 65 retrospectively selected clinical samples corresponding to 32 patients. RESULTS: A valid result was obtained for 92.3% (60/65), 90.8% (59/65) and 78.5% (51/65) of the samples tested, considering the three strips, respectively. Global concordance rates between AID and BACTEC for detecting resistance to isoniazid, rifampicin, fluoroquinolones, ethambutol, kanamycin/capreomycin and streptomycin were 98.3% (59/60), 100% (60/60), 91.5% (54/59), 72.9% (43/59), 100% (51/51) and 98.0% (50/51), respectively. Regarding the discordant results obtained between AID and BACTEC, the alternative molecular methods performed (GenoType MTBDRplus, GenoType MTBDRsl [Hain Lifescience, Germany] and/or pyrosequencing) confirmed the genotypic result in 90.9% (20/22) of the cases. CONCLUSIONS: AID line probe assay is a useful tool for the rapid detection of drug resistance in clinical samples enabling an initial therapeutic approach. Nevertheless, for a correct management of drug resistant tuberculosis patients, molecular results should be confirmed by a phenotypic method.

Diagnostic accuracy study of multiplex PCR for detecting tuberculosis drug resistance.

OBJECTIVE: To study the diagnostic accuracy of a multiplex real-time PCR (Anyplex II MTB/MDR/XDR, Seegene, Corea) that detects Mycobacterium tuberculosis resistant to isoniazid (INH), rifampicin (RIF), fluoroquinolones (FLQ) and injectable drugs (kanamycin [KAN], amikacin [AMK] and capreomycin [CAP]) in isolates and specimens. METHODS: One hundred fourteen cultured isolates and 73 sputum specimens were retrospectively selected. Results obtained with multiplex PCR were compared with those obtained with BACTEC. Discordant results between multiplex PCR and BACTEC were tested by alternative molecular methods. RESULTS: Sensitivity and specificity of multiplex PCR for detecting drug resistance in isolates were 76.5% and 100%, respectively, for INH; 97.2% and 96.0%, respectively, for RIF; 70.4% and 87.9%, respectively, for FLQ; 81.5% and 84.8%, respectively, for KAN; 100% and 60%, respectively, for AMK, and 100% and 72.3%, respectively, for CAP. Sensitivity and specificity of Anyplex for detecting drug resistance in specimens were 93.3% and 100%, respectively, for INH; 100% and 100%, respectively, for RIF; 50.0% and 100%, respectively, for FLQ; and 100% and 94.4%, respectively, for both KAN and CAP. Among the discordant results, 87.7% (71/81) of results obtained with the multiplex PCR were concordant with at least one of the alternative molecular methods. CONCLUSIONS: This multiplex PCR may be a useful tool for the rapid identification of drug resistant tuberculosis in isolates and specimens, thus allowing an initial therapeutic approach. Nevertheless, for a correct management of patients, results should be confirmed by a phenotypic method.