Evaluation of rifampicin resistance and 81-bp rifampicin resistant determinant region of rpoB gene mutations of Mycobacterium tuberculosis detected with XpertMTB/Rif in Cross River State, Nigeria

AbstractObjective/backgroundWorld Health Organization tuberculosis (TB) indices from 2014 to 2016 showed that Nigeria had the 6th highest prevalence, 4th highest incidence, and the highest mortality rate globally. In efforts to improve TB care, the XpertMTB/Rif (GeneXpert) technology, Cepheid, Sunnyvale, California, USA, which has revolutionized TB detection with concomitant rifampicin-resistance molecular detection, was introduced in Cross River State, South–South Nigeria, in 2014. The GeneXpert uses molecular beacons to detect five overlapping 81-bp regions in the rpoB gene known as the Rifampicin Resistant Determinant Region (RRDR). These probes are represented as Probe A (507–511), Probe B (512–518), Probe C (518–523), Probe D (523–529), and Probe E (529–533). Mutations in this region have been shown to account for about 93% of resistance to rifampicin, which is the most important drug in tuberculosis treatment. The objective of this study was to determine the frequency of rifampicin resistance and the commonly associated probes for various rpoB gene mutations within the 81-bp RRDR of Mycobacterium tuberculosis in Cross River State, Nigeria.MethodWe collated and analyzed data from the 10 Xpert MTB/Rif sites in Cross River State from June 2014 to June 2016 and determined the frequency of mutations associated with different probes designated A–E, which represent the RRDR of rpoB gene. All centers use XpertMTB/Rif version G4.ResultIn total, 973 tuberculosis cases were detected from 4671 cases tested. Rif resistance was detected in 6.0% (58/973) of cases. Probe E mutations were the most common, seen in 60.3% (35/58); followed by Probe D, 17.2% (10/58); and Probe B, 13.8% (8/58). Probe A occurred in 3.4% (2/58). No Probe C mutation was seen. Multiple mutation combinations involving probes B and D occurred in 3.4% (2/58), while one isolate had triple site mutations involving A, D, and E. One isolate that at initial testing showed a Probe A mutation displayed a Probe D mutation when tested in another site prior to treatment enrollment.ConclusionIn our setting, 6.0% of tuberculosis isolates are rifampicin resistant. Mutations associated with probe E commonly due to codon 531 are the most predominant cause of rifampicin resistance. Mutations at probe C (codons 518–523) were uncommon. A change in mutation may have occurred in one of the patients

Evaluation of pulmonary tuberculosis case detection improvement with the deployment of XpertMTB/Rif in the tuberculosis control program of cross River State, Nigeria

Objective/Background: Global indices show that Nigeria has the highest tuberculosis (TB)-related mortality rate. Overdependence on Ziehl–Neelsen (ZN) smear microscopy for diagnosis and human immunodeficiency virus (HIV)/AIDS has limited control efforts. The new polymerase chain reaction-based XpertMTB/Rif (Cepheid Inc., CA, USA), which detects Mycobacterium tuberculosis and rifampicin resistance, was introduced in Cross River State in 2014. We evaluated the increment in pulmonary TB case detection following introduction of XpertMTB/Rif into the Cross River State TB control program. Materials and Methods: Data from three XpertMTB/Rif centers in Cross River were prospectively collected from June 2014 to December 2015. One spot specimen and one early morning sputum specimen were collected from each patient and tested using microscopy while one specimen was used for XpertMTB/Rif. Results: A total of 2326 patients comprising 47.4.0% (1103) males and 52.6% (1223) females were evaluated. Their mean age was 38.8 years (range 4–89 years); 42.6% (991) were HIV positive and 50.9% (1183) HIV negative, and for 6.5% (158) HIV status was unknown. XpertMTB/Rif detected M. tuberculosis in 22.9% (534) of patients, while 16.8% (391) were ZN smear positive. Smear microscopy missed 24.5% (131/534) of cases (P < 0.0001). When patients where categorized according to HIV status, XpertMTB/Rif detected 23.7% (280/1183) and ZN smear microscopy detected 18.5% (219/1183) of HIV-negative patients. XpertMTB/Rif detected 21.5% (213/991) and ZN smear 14.1% (140/991) of HIV-positive patients. TB case detection was significantly higher in HIV-negative patients than in HIV-positive patients when either XpertMTB/Rif and/or ZN was used (P = 0.018 and 0.012, respectively). Conclusion: The use of XpertMTB/Rif has significantly increased TB case detection and data in Cross River State. Scale-up of additional strategies such as culture is still required to improve TB detection in HIV patients