Infectious diseases caused by clinically important Mycobacteria continue to be an important public health problem worldwide primarily due to emergence of drug resistance crisis. In recent years, the control of tuberculosis (TB), the disease caused by Mycobacterium tuberculosis (MTB), is hampered by the emergence of multidrug resistance (MDR), defined as resistance to at least isoniazid (INH) and rifampicin (RIF), two key drugs in the treatment of the disease. Despite the availability of curative anti-TB therapy, inappropriate and inadequate treatment has allowed MTB to acquire resistance to the most important anti-TB drugs. Likewise, for most mycobacteria other than MTB, the outcome of drug treatment is poor and is likely related to the high levels of antibiotic resistance. Thus, a better knowledge of the underlying mechanisms of drug resistance in mycobacteria could aid not only to select the best therapeutic options but also to develop novel drugs that can overwhelm the existing resistance mechanisms. In this article, we review the distinctive mechanisms of antibiotic resistance in mycobacteria.

New Delhi metallo-beta-lactamase (NDM-1) is a novel metallo-beta-lactamase (MBL). Sporadic cases of NDM-1 positive strains have been reported from different countries, suggesting a widespread dissemination. The aim of this study was the detection of MBLs in Enterobacteriaceae isolated from patients in Tehran hospitals. After identification tests, the susceptibility to the antibiotics was done by Kirby-Bauer method and broth microdilution. Carbapenem-resistant isolates were tested for carbapenemase production using the modified Hodge test (MHT). Carbapenem-resistant strains screened for bla(KPC) gene and genes encoding MBLs. Twenty-three isolates (6.3%) were resistant to meropenem, eleven isolates (3%) were resistant to ertapenem, and four isolates (1.1%) were resistant to imipenem. MHT was positive in 11 (47.8%) of the carbapenem-resistant isolates. In March 2011, we detected a multiple drug-resistant Klebsiella pneumoniae isolate that was resistant to all tested antibiotics except colistin. PCR confirmed that this isolate contained bla(NDM-1), bla(TEM), bla(SHV), and bla(CTX-M). This is the first report on the detection of MBL NDM-1 in Iran. The rapid spread of NDM-1-positive bacteria proved to be a major challenge for the treatment and control of infectious diseases.

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The prevalence of drug resistance in this study area underscoring the need for further enforcement of TB control strategies in the Iran. Drug susceptibility testing for all TB cases to provide optimal treatment, establishing advanced diagnostic facilities for rapid detection of MDR-TB and continuous monitoring of drug resistance are recommended for prevention and control of drug-resistant TB.

Peripheral nerves are exposed to physical injuries usually caused by trauma that may lead to a significant loss of sensory or motor functions and is considered as a serious health problem for societies today. This study was designed to develop a novel nano bioglass/gelatin conduit (BGGC) for the peripheral nerve regeneration. The bioglass nanoparticles were prepared by sol-gel technique and characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis. The interfacial bonding interaction between the nano-bioglass and gelatin in the developed conduits was assessed by FTIR. The surface morphology and pore size of the nanocomposite were investigated through scanning electron microscopy with the pore size of the conduits being 10-40 μm. Biocompatibility was assessed by MTT assay which indicated the BGGC to have good cytocompatibility. The guidance channel was examined and used to regenerate a 10 mm gap in the right sciatic nerve of a male Wistar rat. Twenty rats were randomly divided into two experimental groups, one with the BGGC and the other being normal rats. The gastrocnemius muscle contractility was also examined at one, two and three months post-surgery in all groups using electromyography (EMAP). Histological and functional evaluation and the results obtained from electromyography indicated that at three months, nerve regeneration of the BGGC group was statistically equivalent to the normal group (p > 0.05). Our result suggests that the BGGC can be a suitable candidate for peripheral nerve repair.

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An exosome is a nano vesicle that buds from the endosomal compartment; it is produced and released by all kinds of mammalian cells. This vesicle contains a variety of proteins, lipids, mRNAs and miRNAs. These components are specific to the origin of the exosomes and contribute to cell-cell communications. Recently, it has been reported that a few single cell eukaryotic pathogens such as Cryptoccoccus neoformance and Leishmania major and donovanican secrete an exosome and influence the host immune system. In addition, it has been observed that cells infected by intracellular pathogens are capable of secreting an exosome which is involved in the fate of the infection. Furthermore, retroviruses recruit the host`s endosomal compartments in order to generate viral vesicles which are similar to the exosome. Most of the exosomes involved in infectious biology can either spread or limit an infection based on the type of pathogen and its target cells. Hence, an exosome may be an appropriate candidate for a vaccine therapy in prophylaxis and treatment.

Nontuberculous mycobacteria (NTM) can cause disease which can be indistinguishable from tuberculosis (TB), posing a diagnostic and therapeutic challenge, particularly in low- and middle-income settings. We aimed to investigate the mycobacterial agents associated with presumptive clinical pulmonary TB in Iran. A total of 410 mycobacterial isolates, obtained between March 2014 and January 2016, from 7600 clinical samples taken from consecutive cases of presumptive diagnosis of TB were identified. Phenotypic and molecular tests were used to identify the isolated organisms to the species level. Single-locus and multilocus sequence analysis based on 16S rRNA, rpoB, hsp65 and ITS locus were used to confirm the results. Of 410 consecutive strains isolated from suspected TB subjects, 62 isolates (15.1%) were identified as NTM. Patients with positive NTM cultures met American Thoracic Society diagnostic criteria for NTM disease. Mycobacterium simiae was the most frequently encountered (38.7%), followed by Mycobacterium fortuitum (19.3%), M. kansasii (17.7%) and M. avium complex (8.0%). Isolation of NTM, including M. simiae, from suspected TB cases is a serious public health problem and merits further attention by health authorities, physicians and microbiologists