No abstract

It is generally believed that drug resistance among treated tuberculosis (TB) patients is as a result of acquired drug resistance due to inappropriate treatment. Previous studies have shown that primary drug resistance caused by transmission also plays a role among treated cases. Differentiating the two types of drug resistance will help in developing appropriate strategies for control of drug resistant tuberculosis. In this study, we tested the hypothesis that drug resistance among treated TB patients is mainly caused by primary resistance rather than acquired resistance. Defining resistance profiles by molecular drug susceptibility test, we used Unit Variable Number Tandem Repeats (VNTR) to genotype and Whole Genome Sequencing (WGS) to confirm the accordance of the first and last Mycobacterium tuberculosis isolates from treated pulmonary TB patients in Shanghai from 2009–2015. Among 81 patients with increasing drug resistance, out of 390 patients enrolled, paired isolates from 59.3% (48/81) had different VNTR patterns indicating primary drug resistance. Our results have demonstrated that primary resistance due to exogenous reinfection is the major cause of drug resistance among treated TB patients in Shanghai; thus, strategies aimed at preventing and interrupting transmission are urgently needed to effectively reduce the epidemic of drug resistant tuberculosis.

Molecular epidemiology of human and animal ecovariants of Escherichia coli from different regions of Nigeria were studied using their antibiotic susceptibility patterns, plasmid profile and pulsed-field gel electrophoresis (PFGE). E. coli was isolated using eosin methylene blue agar (EMB) and identified by conventional microbiological technique. The isolates were tested against 14 antibiotics using the disc diffusion method. PFGE was performed using XbaI as restriction enzyme according to pulse net protocol. Overall, 42 different antibiotics resistance clusters were observed, with each isolate showing resistance to at least four or more drugs tested. Fingerprinting of 140 isolates by PFGE technique and subsequent cluster analysis revealed a diverse E. coli population belonging to 47 distinct subtypes. Cluster analysis of the 120 KB plasmid bearing isolates indicated that these isolates belonged to one unique clonal group with ≥80% genetic similarity to each other, their animal or human origin, geographical distribution and clinical or non-clinical source notwithstanding. The sharing of drug resistant strains between human and animal population has shown that identical clones are circulating among human and animal population in the study area.

SUMMARY Pyrazinamide (PZA) is an important first-line anti-tuberculosis drug, however, there are relatively few available data on PZA resistant (PZA-R) rate in China. From June 2009 to June 2012, we selected 493 isolates from five field settings in China to investigate PZA-R by pncA gene sequencing. The result showed that PZA-R rate was 1.0% (2/196) among pan-susceptible isolates, 3.1% (4/130) among isoniazid (INH) mono-resistant isolates, 14.0% (6/43) among rifampin (RIF) mono-resistant isolates and 43.5% (54/124) among multidrug resistant (MDR) isolates. MDR tuberculosis (TB), RIF mono-resistance, and retreatment were found to be risk factors for PZA-R. Newly diagnosed PZA-R TB patients and clustered isolates with identical pncA mutations indicate that transmission of PZA-R isolates plays an important role in emergence of PZA-R TB. The results suggest that, it is necessary to conduct PZA susceptibility test among MDR isolates and modify the treatment regimens accordingly.

Rapid diagnosis and treatment of disease is often based on the identification and characterization of causative agents derived from phenotypic characteristics. This can be laborious and time consuming, often requiring many skilled personnel and a large amount of lab space. However, the introduction of nucleic acid amplification techniques into molecular biology has transformed the laboratory detection of pathogens. The progression of the molecular diagnostic revolution currently relies on the ability to efficiently and accurately offer multiplex detection and characterization for a variety of infectious disease pathogens. DNA microarray analysis has the capability to offer robust multiplex detection. Multiple microarray platforms exist, including printed double-stranded DNA and oligonucleotide arrays, in situ-synthesized arrays, high-density bead arrays, electronic microarrays, and suspension bead arrays. The aim of this paper was to review DNA microarray technology, highlighting two major types: the oligonucleotide-based array and the PCR product-based array. Although, the use of microarrays to generate gene expression data has become routine, applications pertinent to microbiology continue to rapidly expand. This review highlights uses of microarray technology that impact diagnostic microbiology, including the detection and identification of pathogens, determination of antimicrobial resistance, epidemiological strain typing, and determination of virulence factors.