GenoType MTBDRslperformance on clinical samples with diverse genetic background

Abstract

We evaluate the performance of the GenoType1 MTBDRsl (Hain Lifescience Nehren, Germany) for the detection of second-line resistant tuberculosis and we correlate the frequency of mutations to different Mycobacterium tuberculosis genotypes.We tested 175 strains and 59 clinical specimens interpreting the results according to the Standards for Reporting of Diagnostic Accuracy recommendations. All the strains were also investigated by spoligotyping and Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats typing.The performances of the MTBDRsl in detecting resistance to fluoroquinolones (FQ), second-line injectable drugs (SLID), and ethambutol (EMB) on clinical isolates were similar (specificity ,99%, sensitivity ,70%, and positive predictive value (PPV) ,99%).Of the 59 respiratory specimens, three samples were classified as ''indeterminate''. The specificity in detecting resistances was similar for FQs and EMB 100% (95% CI 92.7-100%) and 100% (95% CI 83.9-100%), respectively with a PPV of 100% (95% CI 64.6-100%) and 100% (95% CI 87.9-100%), respectively. Detection of SLID showed a specificity of 89.1% (95% CI 77.0-95.3%) and a PPV of 58.3% (95% CI 32.0-80.7%). Sensitivity for FQ-resistance detection was 100% (95% CI 64.6-100%), whereas for SLID and EMB it was 89.1% (95% CI 77.0-95.3%) and 86.1% (95% CI 71.3-93.9%), respectively. We detected a significant association between mutations in the rrs gene and Beijing lineage.The MTBDRsl can be used to ''rule in'' extensively drug-resistant strains of tuberculosis in a high risk group; the low sensitivity and negative predicted value (NPV) make confirmation by conventional drug susceptibility testing mandatory when mutations are not identified. NPV for SLID is higher in Beijing strains, showing that the predictive values of the molecular tests are related to the genetic background.

Diagnostic Accuracy of the GenoType MTBDR sl Assay for Rapid Diagnosis of Extensively Drug-Resistant Tuberculosis in HIV-Coinfected Patients

“…Controversies regarding sensitivity rates of the assay reported in previous studies, especially for AGs and CPs and for KAN in particular (15,16,(21)(22)(23), could be attributed to the diverse genetic background of strains and different distribution of mutations conferring drug resistance in different geographic settings. In recent studies conducted on clinical strains isolated in Estonia, Vietnam, and South Africa, the sensitivity of the assay for the detection of resistance to KAN was very low (reaching 43% at its maximum) (16,22,23), probably due to the high prevalence of Beijing strains harboring mutations in eis genes not recognized by the assay and responsible for conferring resistance to KAN only, as was shown in Vietnam (23).…”

“…The assay has been evaluated in two low-incidence TBand HIV settings, predominantly on cultures as well as patient specimens, and demonstrated good sensitivity and specificity (13,14). Assay performance varied significantly depending on the genetic background of the strains and tended to be lower with Eastern European strains (15,16). Currently, only limited systematic data are available on the performance of molecular assays for the direct diagnosis of resistance to RIF and INH in specimens from patients in settings of high TB burden and high HIV prevalence (17,18); the sensitivity and specificity of LPAs for the detection of resistance to SLD in specimens from HIV-infected TB patients are unknown.…”

Potential antimicrobial agents for the treatment of multidrug-resistant tuberculosis

“…Most of the drug resistance is caused by mutations in genes of M. tuberculosis coding for drug targets, but there is also evidence for mutations resulting in upregulation of bacterial efflux pumps, potentially reducing susceptibility to several drug groups [12,13]. An important feature of M. tuberculosis is that under stress conditions, including hypoxia and host factors like nitric oxide, the organism is able to change its genetic programme by, for example, inducing a 48-gene regulon via the response regulator DosR; this leads to inhibited aerobic respiration, thereby suppressing M. tuberculosis replication [14].…”

Molecular Characterization of the Resistance of <i>Mycobacterium tuberculosis</i> to Second Line Drugs in Côte d’Ivoire

“…This finding can be explained by a fairly low negative predictive value of Genotype ® MTBDRsl for the detection of resistance in fluoroquinolones [6]. To this must be added the fact that only gyrA is targeted by the test, although it is known that mutations in other genes such as gyrB are rarely observed [7].…”