CRISPR-Cas system and its use in the diagnosis of infectious diseases.

Rapid and accurate diagnostic methods for detecting pathogens are needed for effective management and treatment of infectious diseases. The conventional pathogen detection approach based on culture is considered the gold standard method, but needs several days to corroborate its results. Using nucleic acids from pathogens as detection targets has a considerable advantage in overcoming these time-consuming issues. The development of several molecular techniques has started to change the landscape of infectious disease diagnosis. However, these require expensive reagents, equipment, and sophisticated infrastructure, as well as highly trained workers. In this context, it is necessary to identify new diagnostic strategies to overcome these issues. Recently, CRISPR/Cas based diagnosis has revolutionized the area of molecular diagnostics of pathogenic diseases. In this review, we have discussed the different classes of CRISPR-Cas systems and their functions, and then focused on recent advances in CRISPR-based diagnosis technologies and the perspective of using this as a potential biosensing platform to detect infectious disease.

Epidemiological investigation of the COVID-19 outbreak in Vellore district in South India using Geographic Information Surveillance (GIS)

ObjectivesGeographical Information Surveillance (GIS) is an advanced digital technology tool that maps location-based data and helps in epidemiological modeling. We applied GIS to analyze patterns of spread and hotspots of COVID-19 cases in Vellore district in South India. MethodsLaboratory-confirmed COVID-19 cases from the Vellore district and neighboring taluks from March 2020 to June 2021 were geo-coded and spatial maps were generated. Time trends exploring urban-rural burden with an age-sex distribution of cases and other variables were correlated with outcomes. ResultsA total of 45,401 cases of COVID-19 were detected with 20730 cases during the first wave and 24671 cases during the second wave. The overall incidence rates of COVID-19 were 462.8 and 588.6 per 100,000 populations during the first and second waves respectively. The pattern of spread revealed epicenters in densely populated urban areas with radial spread sparing rural areas in the first wave. The case fatality rate was 1.89% and 1.6% during the first and second waves that increased with advancing age. ConclusionsModern surveillance systems like GIS can accurately predict the trends and pattern of spread during future pandemics. A real-time mapping can help design risk mitigation strategies thereby preventing the spread to rural areas.

The recent trend in mycobacterial strain diversity among extra pulmonary lymph node tuberculosis and their association with drug resistance and the host immunological response in South India.

BACKGROUND: Tuberculosis (TB) though primarily affects the lungs it may also affect the other parts of the body and referred as extra pulmonary (EPTB). This study is focused on understanding the genetic diversity and molecular epidemiology of Mycobacterium tuberculosis (M.tb) among tuberculous lymphadenitis (TBL), a form of EPTB patients identified in Chennai, Tamil Nadu. METHODS: The genetic diversity was identified by performing spoligotyping on the M.tb clinical isolates that were recovered from lymph node samples. A total of 71 M.tb isolates were recovered from extra pulmonary lymph node samples and subjected to Drug susceptibility testing and spoligotyping was carried out. In addition, immunological characterization from blood of same individuals from whom M.tb was isolated was carried out between the two major lineages groups East African Indian 3 (EAI3) and non-EAI3 strains by ELISA. The results of spoligotyping patterns were compared with the world Spoligotyping Database of Institute Pasteur de Guadeloupe (SpolDB4). RESULTS: We found 41 spoligotype patterns and their associated lineages. Out of 41 spoligotype pattern, only 22 patterns are available in the spoldB4 database with Spoligotype international Type (SIT) number and remaining patterns were orphan strains without SIT number. The most predominant spoligotype lineage that was found in lymph node sample in this region of India was EAI (36), followed by central Asian strain (CAS) (6), T1 (5), Beijing (3), Latin American & Mediterranean (LAM) (2), U (1), X2 (1) and orphan (22). In addition to EAI, CAS and Beijing, our study identified the presence of orphan and unique spoligotyping patterns in Chennai region. We observed six drug resistant isolates. Out of six drug resistant isolates, four were resistant to isoniazid drug and associated with EAI family. Moreover, we observed increased levels of type 2 and type 17 cytokine profiles between EAI3 and non-EAI family, infected individuals. CONCLUSIONS: The study confirms that EAI lineage to be the most predominant lineages in EPTB patients with lymphadenitis and were found to have increased type 1 and type 17 proinflammatory cytokine profiles.

National and state wise estimate of time varying reproduction number for COVID-19 in India during the nationwide lockdown.

To understand the effect of nationwide lockdown on transmissibilty of SARS-CoV-2 in India, time varying reproduction number during the first weeks of April, 2020 was estimated. The time varying reproduction number was estimated using EpiEstim package in R programming language. The reproduction number has come down significantly during the lockdown period both at national level and in most states but it wasnt reduced to less than 1. This calls for urgent need for more effective control measures in addition to lockdown to stop the epidemic spread of the virus.

Estimate of COVID-19 case prevalence in India based on surveillance data of patients with severe acute respiratory illness

In absence of extensive testing for SARS-CoV-2, true prevalence of COVID-19 cases in India remain unknown. In this study, a conservative estimate of prevalence of COVID-19 is calculated based on the age wise COVID-19 positivity rate among patients with severe respiratory illness as reported by Indian Council of Medical Research. Calculations in the study estimates a cumulative number of 17151 COVID-19 positive cases by the end of April 2, 2020.

In vitro interaction profiles of the new antitubercular drugs bedaquiline and delamanid with moxifloxacin against clinical Mycobacterium tuberculosis isolates.

OBJECTIVES: The emergence of drug-resistant tuberculosis (TB) poses a serious challenge to existing anti-TB therapies. Hence, there is a direct need for identification of new drugs and effective combination regimens. METHODS: In this study, minimum inhibitory concentrations (MICs) of the anti-TB drugs bedaquiline (BDQ), delamanid (DEL) and moxifloxacin (MFX) were evaluated using a resazurin microtiter assay (REMA) against five drug-resistant clinicalMycobacterium tuberculosis (MTB) isolates as well as the drug-susceptible reference strain H37Rv. In addition, their fractional inhibitory concentration indices (FICIs) were evaluated using a REMA-based calorimetric chequerboard assay to assess their interaction profiles against the MTB isolates. RESULTS: The FICI indicated that BDQ acted synergistically with DEL against isoniazid (INH)-monoresistant, rifampicin (RIF)-monoresistant and extensively drug-resistant (XDR) clinical MTB isolates. In addition, the combination of DEL acted synergistically with MFX against INH-monoresistant, RIF-monoresistant and XDR clinical MTB isolates. Moreover, the combination of BDQ and MFX showed a synergistic effect against RIF-monoresistant and pre-XDR clinical MTB isolates. DEL at 0.125×MIC (i.e. 0.015µg/mL) used in combination with BDQ at 0.25×MIC (i.e. 0.015µg/mL) had a stronger bactericidal effect against the XDR-TB clinical isolate than DEL alone at 1×MIC (i.e. 0.125µg/mL). CONCLUSION: Synergistic and additive effects between these two-drug combinations offer an attractive chemotherapeutic regimen against drug-resistant clinical MTB isolates.