In vitro and in silico screening of Klebsiella pneumoniae new Delhi metallo-β-lactamase-1 inhibitors from endophytic Streptomyces spp

The increase in drug resistance over the last two decades is a big threat in health care settings. More importantly, the dissemination of carbapenem-resistant Enterobacteriaceae is the major threat to public health with an increase in morbidity and mortality. β-lactamase is known to confer enteric bacteria with nearly complete resistance to all β-lactam antibiotics including the late-generation carbapenems. The commercially available β-lactamase inhibitors, clavulanic acid, sulbactam, and tazobactam are being met with an increasing number of resistant phenotypes and are ineffective against pathogens harbouring New Delhi metallo-β-lactamase (NDM-1). Inhibition of New Delhi metallo-β-lactamase-1 activity is one potential way to treat metallo β-lactamase (MBL) producing multi drug resistant (MDR) pathogen. The present study focused on screening of Klebsiella pneumoniae New Delhi metallo-β-lactamase-1 (BLIs) from endophytic Streptomyces spp. using in vitro and in silico methods. The study identified three potential inhibitors of New Delhi metallo-β-lactamase-1, namely dodecanoic acid, dl-alanyl-l-leucine and phenyl propanedioic acid. These molecules were found to bind to other MBLs namely, IMP-1 and VIM-2. To the best of our knowledge, this is the first kind of study reporting the binding mode of these molecules with New Delhi metallo-β-lactamase-1.Communicated by Ramaswamy H. Sarma.

Current Status and Applications of Adaptive Laboratory Evolution in Industrial Microorganisms

Adaptive laboratory evolution (ALE) is an evolutionary engineering approach in artificial conditions that improves organisms through the imitation of natural evolution. Due to the development of multi-level omics technologies in recent decades, ALE can be performed for various purposes at the laboratory level. This review delineates the basics of the experimental design of ALE based on several ALE studies of industrial microbial strains and updates current strategies combined with progressed metabolic engineering, in silico modeling and automation to maximize the evolution efficiency. Moreover, the review sheds light on the applicability of ALE as a strain development approach that complies with non-recombinant preferences in various food industries. Overall, recent progress in the utilization of ALE for strain development leading to successful industrialization is discussed.

Secondary Metabolites of Actinomycetes and their Antibacterial, Antifungal and Antiviral Properties

The growing resistance of microorganisms towards antibiotics has become a serious global problem. Therapeutics with novel chemical scaffolds and/or mechanisms of action are urgently needed to combat infections caused by multidrug resistant pathogens, including bacteria, fungi and viruses. Development of novel antimicrobial agents is still highly dependent on the discovery of new natural products. At present, most antimicrobial drugs used in medicine are of natural origin. Among the natural producers of bioactive substances, Actinobacteria continue to be an important source of novel secondary metabolites for drug application. In this review, the authors report on the bioactive antimicrobial secondary metabolites of Actinobacteria that were described between 2011 and April 2018. Special attention is paid to the chemical scaffolds, biological activities and origin of these novel antibacterial, antifungal and antiviral compounds. Arenimycin C, chromopeptide lactone RSP 01, kocurin, macrolactins A1 and B1, chaxamycin D as well as anthracimycin are regarded as the most effective compounds with antibacterial activity. In turn, the highest potency among selected antifungal compounds is exhibited by enduspeptide B, neomaclafungins A-I and kribelloside D, while ahmpatinin i Bu, antimycin A1a, and pentapeptide 4862F are recognized as the strongest antiviral agents.

Exploration of Antifungal and Immunomodulatory Potentials of a Furanone Derivative to Rescue Disseminated Cryptococosis in Mice

Cryptococcus neoformans infection is quite complex with both host-pathogen interaction and host immune profile determining disease progress and therapeutic outcome. Hence in the present study, the potential utility of (E)-5-benzylidenedihydrofuran-2(3 H)-one (compound-6) was explored as an effective anticryptococcal compound with immunomodulatory potential. The efficacy of compound-6 in pulmonary cryptococosis model using H99 strain was investigated. The effective dose was found to provide 100% survival, with a significant reduction of yeast burden in lungs and brain. The biodistribution analysis provided evidence for the presence of higher concentration of compound-6 in major organs including lungs and brain. In addition, compound-6 treated mice had significantly higher expression of IL-6, IL-4 and IFN-γ in lung and brain. Similarly, elevated expression of TNF-α, IL-β1 and IL-12 were observed in lungs, suggesting the protective host response against C. neoformans. The reduction and clearance of fungal load in systemic organs and mouse survival are notable results to confirm the ability of compound-6 to treat cryptococcosis. In conclusion, the low molecular weight (174 Da), lipophilicity, its ability to cross blood brain barrier, and facilitating modulation of cytokine expression are the added advantages of compound-6 to combat against disseminated cryptococosis.