Pre-Extensively Drug Resistant Tuberculosis (Pre-XDR-TB) among Pulmonary Multidrug Resistant Tuberculosis (MDR-TB) Patients in Bangladesh

Background & Objectives: Emergence of drug resistant Tuberculosis (TB) is a major obstacle in the TB control programme of Bangladesh. This study was carried out to detect pre-extensively drug resistant TB (pre-XDR-TB) cases among the multidrug resistant TB (MDR-TB) patients in Bangladesh, as the early detection of pre-XDR-TB can guide clinicians in the appropriate modification of MDR-TB treatment regimen with effective drugs to prevent treatment failure. Methodology: A total of 68 MDR-TB cases were enrolled in this study. Multiplex Real-time PCR was done to detect pre-XDR-TB cases directly from sputum samples of MDR-TB patients. Results: Out of 68 MDR-TB cases 11 (16.18%) cases were detected as pre-XDR-TB. The resistant profile of the 11 pre-XDR-TB revealed 9 (81.82%) cases of fluoroquinolone (FLQ) resistant pre-XDR-TB and 2 (18.18%) cases of injectable second line (ISL) agent resistant pre-XDR-TB. Out of 11 pre-XDR-TB cases 7 (63.64%) cases had history of taking treatment for MDR-TB regularly, 1 (9.09%) case had history of taking treatment for MDR-TB irregularly and 3 (27.27%) cases had no history of taking treatment for MDR-TB. Conclusion: This study encountered a high rate of pre-XDR-TB cases along with a significant number of primarily resistant bacilli which is of concern in the management of MDR-TB. It is evident that Bangladesh is in urgent need to device strategies for rapid and early detection of pre-XDR-TB in order to prevent treatment failure of MDR-TB cases and also to halt the progression of MDR-TB cases to extensively drug resistant TB (XDR-TB), which is not only difficult but also very expensive to treat.

<i>gyrA</i>Gene Mutation Conferring Phenotypic Cross-Resistance among Fluoroquinolones (Ofloxacin, Levofloxacin and Gatifloxacin) in Multidrug Resistant <i>Mycobacterium tuberculosis</i>Strains Isolated from Pulmonary MDR-TB Patients in Bangladesh

Background and objectives: Fluoroquinolones (FLQs) are an essential component of multidrug resistant-tuberculosis (MDR-TB) treatment regimen but unfortunately the emergence of FLQ resistant MDR-TB cases is challenging the current MDR-TB treatment regimen. FLQ resistance is mainly caused by gyrA gene mutation and phenotypic cross-resistance may occur among the different FLQs. A limited number of data exists regarding the cross-resistance phenomenon among FLQs and it appears that resistance to the present class representative FLQ, ofloxacin (OFX), may or may not correlate with complete cross-resistance to other FLQs. So the study was designed to observe if gyrA gene mutations confer to the phenotypic cross-resistance among FLQs [OFX, Levofloxacin (LFX) and Gatifloxacin (GFX)] tested. Methodology: Sputum samples from 68 diagnosed pulmonary MDR-TB cases were collected. All samples were subjected to Multiplex Real-time PCR for the detection of gyrA gene mutations and conventional culture on Lowenstein-Jensen (L-J) media followed by drug sensitivity testing (DST) of culture isolates (MDR-TB strains) by indirect proportion method for the detection of phenotypic resistance pattern to OFX, LFX and GFX. Results: Out of the 68 MDR-TB sputum samples 13 (19.11%) had MDR-TB bacilli with mutations in the gyrA gene and 11(16.18%) of the MDR-TB culture isolates were found to have resistance to FLQs by DST. The study observed that 11 MDR-TB samples with gyrA gene mutations showed complete phenotypic cross-resistance among OFX, LFX and GFX. Conclusion: This study found that mutation in the gyrA gene of the MDR-TB bacilli results in the complete cross-resistance among the FLQs (OFX, LFX and GFX) tested. It is therefore of utmost importance to carry out the base line resistance and cross-resistance tests for the individual FLQs prior to initiating the treatment of MDR-TB cases in Bangladesh for successful clinical outcomes.

A Numerical Approach to Design the Kretschmann Configuration Based Refractive Index Graphene-MoS_(2) Hybrid Layers With TiO_(2)-SiO_(2) Nano for Formalin Detection

In this paper,a Kretschmann configuration based surface plasmon resonance(SPR)sensor is numerically designed using graphene-MoS_(2) hybrid structure TiO_(2)-SiO_(2) nano particles for formalin detection.In this design,the observations of SPR angle versus minimum reflectance and SPR frequency(FSPR)versus maximum transmittance(Tmax)are considered.The chitosan is used as probe legend to perform reaction with the formalin(40%formaldehyde)which acts as target legend.In this paper,both graphene and MoS_(2) are used as biomolecular acknowledgment element(BAE)and TiO_(2) as well as SiO_(2) bilayers is used to improve the sensitivity of the sensor.The numerical results show that the variation of FSPR and SPR angles for inappropriate sensing of formalin is quite insignificant which confirms the absence of formalin.On the other hand,these variations for appropriate sensing are considerably significant that confirm the presence of formalin.At the end of this article,the variation of sensitivity of the proposed biosensor is measured in corresponding to the increment of a refractive index with a refractive index step 0.01 refractive index unit(RIU).In inclusion of TiO_(2)-SiO_(2) bilayers with graphene-MoS_(2),a maximum sensitivity of 85.375%is numerically calculated.