Heteroresistance to rifampicin & isoniazid in clinical samples of patients with presumptive drug-resistant tuberculosis in Central India

Background & objectives: A combination of resistant and susceptible Mycobacterium tuberculosis (MTB) isolated from clinical specimens is referred to as heteroresistance. Heteroresistance leads to difficulties in drug resistance testing and may adversely affect treatment outcomes. The present study estimated the proportion of heteroresistance among MTB in clinical samples of presumptive drug-resistant tuberculosis (TB) patients in Central India. Methods: A retrospective analysis of data generated from line probe assay (LPA) at a tertiary care hospital in Central India between January 2013 and December 2018 was carried out. A heteroresistant MTB in a sample was indicated by the presence of both wild-type and mutant-type patterns on an LPA strip. Results: Data analysis was carried out on interpretable 11,788 LPA results. Heteroresistance in MTB was detected in 637 (5.4%) samples. Of these, heteroresistance in MTB was detected in 413 (64.8%), 163 (25.5%) and 61 (9.5%) samples with respect to rpoB, katG and inhA genes, respectively. Interpretation & conclusions: Heteroresistance is considered a preliminary step in the development of drug resistance. Delayed or suboptimal anti-tubercular therapy in patients with heteroresistance of MTB may elicit full clinical resistance and negatively impact the National TB Elimination Programme. Further studies are, however, needed to determine the impact of heteroresistance on treatment outcomes in individual patients.

NDM-beta-lactamase-1: Where do we stand?

Multidrug-resistant (MDR) Gram-negative bacilli (GNB) have been playing havoc in the field of nosocomial as well as community-acquired infections. Of particular concern are the carbapenem-resistant GNBs, belonging to Enterobacteriaceae and encoding for New Delhi metallo-beta-lactamase-1 (NDM-1) gene. These strains spread rapidly and horizontally in the population, thus exhibiting MDR traits as these can harbour several resistance encoding genes to almost all antimicrobial groups. Several predisposing factors are responsible towards its spread, viz. excessive antibiotic usage, improper aseptic conditions by healthcare workers, lack of awareness, abruptly discontinuing medication course, alternative medications and vector-borne factors contributing to the unchecked harbouring of these super bugs in India. Thus, a bugle call has already been sounded worldwide especially in India, where the country has taken serious cognizance to build up strategy via implementation of several national programs to combat antimicrobial resistance covering human, animal, agriculture and environmental aspects. As there is an exponential rise in variants of NDM-1 harbouring strains, molecular epidemiological investigations of these strains using genotyping techniques are of paramount importance for a better understanding of this rampant spread and curbing resistance thereafter. This review explores the urgent need to develop a cost-effective, rapid molecular assay, viz. the loop-mediated isothermal amplification method for field detection of MBL harbouring bacterial strains, especially NDM-1 and its variants, thus targeting specific carbapenemase genes at a grass root level even to the remote and rural regions of the country.

Genetic diversity of Mycobacterium tuberculosis isolates from central India.

Background & objectives: There is a paucity of data available on genetic biodiversity of Mycobacterium tuberculosis isolates from central India. The present study was carried out on isolates of M. tuberculosis cultured from diagnostic clinical samples of patients from Bhopal, central India, using spoligotyping as a method of molecular typing. Methods: DNA was extracted from 340 isolates of M. tuberculosis from culture, confirmed as M. tuberculosis by molecular and biochemical methods and subjected to spoligotyping. The results were compared with the international SITVIT2 database. Results: Sixty five different spoligo international type (SIT) patterns were observed. A total of 239 (70.3%) isolates could be clustered into 25 SITs. The Central Asian (CAS) and East African Indian (EAI) families were found to be the two major circulating families in this region. SIT26/CAS1_DEL was identified as the most predominant type, followed by SIT11/EAI3_IND and SIT288/CAS2. Forty (11.8%) unique (non-clustered) and 61 (17.9%) orphan isolates were identified in the study. There was no significant association of clustering with clinical and demographic characteristics of patients. Interpretation & conclusions: Well established SITs were found to be predominant in our study. SIT26/CAS1_DEL was the most predominant type. However, the occurrence of a substantial number of orphan isolates may indicate the presence of active spatial and temporal evolutionary dynamics within the isolates of M. tuberculosis.

Cytoskeletal changes during poliovirus infection in an intestinal cell line.

BACKGROUND & OBJECTIVES: Although polioviral replication has been extensively studied, cytoskeletal changes in the host cell during poliovirus replication have not been extensively investigated. We studied the ultrastructural and cytoskeletal changes in host cells during poliovirus infection. METHODS: Fluorescence staining of filamentous actin with a fluorescein-isothiocynate labelled mycotoxin, in the absence and presence of microfilament inhibitors cytochalasins B and D, and electron microscopy were used to investigate the role and fate of actin microfilaments during poliovirus infection, morphogenesis and release in an intestinal cell line, HRT-18. RESULTS: At 10 h post-infection, fluorescence staining of actin showed focal areas of fluorescence in the cytoplasm. By 16 h, these became more prominent and increased in number, and by 18-22 h they coalesced to enclose areas of the cytoplasm. These changes in the actin profile were confirmed by electron microscopy, where small actin bundles appeared in association with vesicles, increased in size, number and thickness, enclosed areas of cytoplasm with numerous vesicles and were finally seen in association with crystalline arrays of virus near the periphery of the cells. The addition of microfilament inhibitors cytochalasins B and D, after the initial period of adsorption resulted in complete inhibition of changes in the actin profile and of viral release, indicating that microfilament inhibitors prevented both polymerization of actin and movement of the virus within the cell. INTERPRETATION & CONCLUSION: In poliovirus infection, both intracellular movement and release of virus appear to be related to cytoskeletal changes, particularly involving actin microfilaments.