Prevalence of mutations at codon 463 of katG gene in MDR and XDR clinical isolates of Mycobacterium tuberculosis in Belarus and application of the method in rapid diagnosis

Progressing nanotechnology to improve targeted cancer treatment: overcoming hurdles in its clinical implementation

The use of nanotechnology has the potential to revolutionize the detection and treatment of cancer. Developments in protein engineering and materials science have led to the emergence of new nanoscale targeting techniques, which offer renewed hope for cancer patients. While several nanocarriers for medicinal purposes have been approved for human trials, only a few have been authorized for clinical use in targeting cancer cells. In this review, we analyze some of the authorized formulations and discuss the challenges of translating findings from the lab to the clinic. This study highlights the various nanocarriers and compounds that can be used for selective tumor targeting and the inherent difficulties in cancer therapy. Nanotechnology provides a promising platform for improving cancer detection and treatment in the future, but further research is needed to overcome the current limitations in clinical translation.

Antibiotic resistance, virulence factors and genotyping of Uropathogenic Escherichia coli strains

Background

The way of treating different types of infectious diseases is really important. Using genotyping method, we can determine the genetic relatedness between the organisms with different resistance profile from different sources. The aim of this study was to determine antibiotic resistance and genotyping of uropathogenic Escherichia coli (UPEC) strains using pulsed field gel electrophoresis (PFGE).

Method

Escherichia coli (E. coli) strains were recovered from the patients with urinary tract infections (UTI) whom admitted in several major hospitals in Tehran. Antibiotic susceptibility testing was done according to CLSI guideline. The present of some virulence factor have been detected using PCR assay. Genotyping of the strains was performed by PFGE and all PFGE profiles were subjected to data processing.

Result

In total, 60 E. coli strains were subjected to the study. Most of E. coli isolates were resistant to cefepime (100%) and cephalothin (74%) and susceptible to imipenem (100%), vancomycin (100%) and doxycycline (100%). Among the UPEC isolates the prevalence of fimbriae type I (fimH), hemolysin (hlyA) and aerobactin (aer) genes were 89%, 60% and 90%, respectively. The PFGE differentiated E. coli strains into 33 different genetic clusters. Majority (30%) of them including PFGE type 11 generated 15 bands, while PFGE type 2 was the lowest (2%) prevalent group with 9 bands.

Conclusion

The result showed that the antibiotic resistance is escalating rapidly. UPEC strains causing infections are more likely to harbor certain virulence genes. Our finding also showed E. coli strains isolated under the study were belonged to the diverse clones.

Evaluation of Genotype MTBDRplus and MTBDRsl Assays for Rapid Detection of Drug Resistance in Extensively Drug-Resistant Mycobacterium tuberculosis Isolates in Pakistan

Pakistan ranks 5th among the world's highest tuberculosis (TB) burden countries alongside the 6th among countries with the highest burden of drug-resistant TB, including multi-drug resistant (MDR)-TB. Methods for rapid and reliable drug susceptibility testing (DST) are prerequisite for the prompt institution of effective anti-TB treatment. The aim of this study was to evaluate the efficiency of Genotype MTBDRplus and MTBDRsl assays for the detection of MDR and (pre-) extensively drug-resistant (XDR-TB) isolates in Pakistan. The study included 47 pre-XDR and 6 XDR-TB isolates, recovered from 53 patients from Pakistan. Conventional DST was performed using the standard 1% proportion method on the Löwenstein-Jensen medium. For molecular determination of drug resistance, GenoType MTBDRplus and GenoType MTBDRsl assays (Hain Lifescience, Germany) were used. To evaluate discrepancies between conventional and molecular DST results, mutation profiling was performed by amplifying and sequencing seven genetic loci, i.e., katG, inhA, and mabA-inhA promoter, rpoB, gyrA, embB, rrs. The sensitivity of Genotype MTBDRplus was 71.7% for isoniazid (INH) and 79.2% for rifampicin (RIF). Sequence analysis revealed non-synonymous mutations in 93.3 and 27.3% of isolates phenotypically resistant to INH and RIF, respectively, albeit susceptible when tested by GenoType MTBDRplus. GenoType MTBDRsl had a sensitivity of 73.6, 64.7, 20, 25, and 100% for the detection of fluoroquinolones, ethambutol, kanamycin, amikacin, and capreomycin resistance, respectively. Upon sequencing, mutations were detected in 20, 77.8%, and all isolates phenotypically resistant to aminoglycosides, ethambutol, and fluoroquinolones, respectively, yet declared as susceptible with GenoType MTBDRsl. Low sensitivities seriously impede the large-scale application of the Genotype MTBDRplus and MTBDRsl assays. Unless further optimized, the currently available line-probe assays should rather be auxiliary to the conventional, phenotype-based methods in the detection of MDR- and XDR-TB in Pakistan.

Bacterial CRISPR Regions: General Features and their Potential for Epidemiological Molecular Typing Studies

Introduction

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) loci as novel and applicable regions in prokaryotic genomes have gained great attraction in the post genomics era.

Methods

These unique regions are diverse in number and sequence composition in different pathogenic bacteria and thereby can be a suitable candidate for molecular epidemiology and genotyping studies. Results:Furthermore, the arrayed structure of CRISPR loci (several unique repeats spaced with the variable sequence) and associated cas genes act as an active prokaryotic immune system against viral replication and conjugative elements. This property can be used as a tool for RNA editing in bioengineering studies.

Conclusion

The aim of this review was to survey some details about the history, nature, and potential applications of CRISPR arrays in both genetic engineering and bacterial genotyping studies.

Novel Mutations in pncA Gene of Pyrazinamide Resistant Clinical Isolates of Mycobacterium tuberculosis

In clinical isolates of Mycobacterium tuberculosis (MTB), resistance to pyrazinamide occurs by mutations in any positions of the pncA gene (NC_000962.3) especially in nucleotides 359 and 374. In this study we examined the pncA gene sequence in clinical isolates of MTB. Genomic DNA of 33 clinical isolates of MTB was extracted by the Chelex100 method. The polymerase chain reactions (PCR) were performed using specific primers for amplification of 744 bp amplicon comprising the coding sequences (CDS) of the pncA gene. PCR products were sequenced by an automated sequencing Bioscience system. Additionally, semi Nested-allele specific (sNASP) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods were carried out for verification of probable mutations in nucleotides 359 and 374. Sequencing results showed that from 33 MTB clinical isolates, nine pyrazinamide-resistant isolates have mutations. Furthermore, no mutation was detected in 24 susceptible strains in the entire 561 bp of the pncA gene. Moreover, new mutations of G→A at position 3 of the pncA gene were identified in some of the resistant isolates. Results showed that the sNASP method could detect mutations in nucleotide 359 and 374 of the pncA gene, but the PCR-RFLP method by the SacII enzyme could not detect these mutations. In conclusion, the identification of new mutations in the pncA gene confirmed the probable occurrence of mutations in any nucleotides of the pncA gene sequence in resistant isolates of MTB.

Low rates of synonymous mutations in sequences of Mycobacterium tuberculosis GyrA and KatG genes

Partial sequences of KatG and GyrA genes have been obtained from multi and extensively drug-resistant (MDR and XDR) clinical isolates of Mycobacterium tuberculosis. Nonsynonymous (DN) and synonymous (DS) distances between those sequences have been calculated by Kumar method. Results revealed that DN is significantly higher than DS between some pairs of partial GyrA sequences. We found out that DN is higher than DS in many other partial and complete sequences of KatG and GyrA coding regions deposited in GenBank. The cause of the DN > DS situation is in several nonsynonymous substitutions occurrence (which may be associated with drug-resistance or not) in the absence of synonymous substitutions. Low rates of synonymous mutations occurrence is a consequence of the strong mutational GC-pressure. Due to the high saturation of third codon positions by guanine and cytosine (78.81 ± 0.17% for all the genes from M. tuberculosis H37Rv genome), the probability to be synonymous for the nucleotide mutation of preferable (AT to GC) direction is low. Fixation of a single nonsynonymous mutation leading to drug-resistance is a consequence of Darwinian selection. This clear example of Darwinian selection on the molecular level can be confirmed by selection test (DN > DS) only in case of DN and DS calculation in pairs of sequences possessing at least two additional nonsynonymous mutations which may be neutral or excessive.