Activity of LCB01-0371, a Novel Oxazolidinone, against Mycobacterium abscessus.

Mycobacterium abscessus is a highly pathogenic drug-resistant rapidly growing mycobacterium. In this study, we evaluated the in vitro, intracellular, and in vivo activities of LCB01-0371, a novel and safe oxazolidinone derivative, for the treatment of M. abscessus infection and compared its resistance to that of other oxazolidinone drugs. LCB01-0371 was effective against several M. abscessus strains in vitro and in a macrophage model of infection. In the murine model, a similar efficacy to linezolid was achieved, especially in the lungs. We induced laboratory-generated resistance to LCB01-0371; sequencing analysis revealed mutations in rplC of T424C and G419A and a nucleotide insertion at the 503 position. Furthermore, LCB01-0371 inhibited the growth of amikacin-, cefoxitin-, and clarithromycin-resistant strains. Collectively, our data indicate that LCB01-0371 might represent a promising new class of oxazolidinones with improved safety, which may replace linezolid for the treatment of M. abscessus.

Molecular epidemiology and resistome analysis of multidrug-resistant ST11 Klebsiella pneumoniae strain containing multiple copies of extended-spectrum ß-lactamase genes using whole-genome sequencing.

The aim of this work was to investigate the mechanism responsible for multidrug resistance in ST11 Klebsiella pneumoniae YMC 2013/7/B3993 containing multiple copies of ESBL genes using multiple parallel sequencing technology. In-depth analysis of the strain revealed multiple copies of ESBL genes, 2 copies of blaSHV-12 and 1 copy of blaCTX-M-15. Furthermore, 1 copy of blaOXA-9 and 3 copies of blaTEM-1 were found. The insertion of Tn1331 was detected, which consisted of blaOXA-9, blaTEM-1, aac(6')-lb-cr, and aadA1 genes. The acquisition of multiple copies of resistance genes was due to the insertion of transposons in the bacterial genome and plasmid. The genotypic analysis revealed that the isolates belonging to ST11 showed severe resistance phenotypes and greater dissemination potential. To the best of our knowledge, this is the first report demonstrating multiple copies of same ESBL genes in K. pneumoniae ST11 isolate. Furthermore, massive parallel sequencing studies of genetic factors to enhance the fitness of this type strain would be warranted to determine whether ST11 K. pneumoniae can spread the KPC-type gene.

In Vitro Activities of LCB 01-0648, a Novel Oxazolidinone, against Gram-Positive Bacteria.

Oxazolidinones are a novel class of synthetic antibacterial agents that inhibit bacterial protein synthesis. Here, we synthesized and tested a series of oxazolidinone compounds containing cyclic amidrazone. Among these compounds, we further investigated the antibacterial activities of LCB01-0648 against drug-susceptible or resistant Gram-positive cocci in comparison with those of six reference compounds. LCB01-0648 showed the most potent antimicrobial activities against clinically isolated Gram-positive bacteria. Against the methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRCNS) isolates, LCB01-0648 showed the lowest MIC90s (0.5 mg/L) among the tested compounds. In addition, LCB01-0648 had the lowest minimum inhibitory concentrations (MICs) against the four linezolid-resistant S. aureus (LRSA) strains (range 2-4 mg/L). The results of the time-kill studies demonstrated that LCB01-0648 at a concentration 8× the (MIC) showed bactericidal activity against methicillin-susceptible Staphylococcus aureus MSSA or MRSA, but showed a bacteriostatic effect against LRSA. These results indicate that LCB01-0648 could be a good antibacterial candidate against multidrug-resistant (MDR) Gram-positive cocci.

Antibacterial Activity of LCB10-0200 against Klebsiella pneumoniae.

Klebsiella pneumoniae is one of the important clinical organisms that causes various infectious diseases, including urinary tract infections, necrotizing pneumonia, and surgical wound infections. The increase in the incidence of multidrug-resistance K. pneumoniae is a major problem in public healthcare. Therefore, a novel antibacterial agent is needed to treat this pathogen. Here, we studied the in vitro and in vivo activities of a novel antibiotic LCB10-0200, a siderophore-conjugated cephalosporin, against clinical isolates of K. pneumoniae. In vitro susceptibility study found that LCB10-0200 showed potent antibacterial activity against K. pneumoniae, including the beta-lactamase producing strains. The in vivo efficacy of LCB10-0200 was examined in three different mouse infection models, including systemic, thigh, and urinary tract infections. LCB10-0200 showed more potent in vivo activity than ceftazidime in the three in vivo models against the drug-susceptible and drug-resistant K. pneumoniae strains. Taken together, these results show that LCB10-0200 is a potential antibacterial agent to treat infection caused by K. pneumoniae.

In vitro and in vivo activities of LCB01-0371, a new oxazolidinone.

LCB01-0371 is a new oxazolidinone with cyclic amidrazone. In vitro activity of LCB01-0371 against 624 clinical isolates was evaluated and compared with those of linezolid, vancomycin, and other antibiotics. LCB01-0371 showed good activity against Gram-positive pathogens. In vivo activity of LCB01-0371 against systemic infections in mice was also evaluated. LCB01-0371 was more active than linezolid against these systemic infections. LCB01-0371 showed bacteriostatic activity against Staphylococcus aureus.

Panel strain of Klebsiella pneumoniae for beta-lactam antibiotic evaluation: their phenotypic and genotypic characterization.

Klebsiella pneumoniae is responsible for numerous infections caused in hospitals, leading to mortality and morbidity. It has been evolving as a multi-drug resistant pathogen, acquiring multiple resistances such as such as horizontal gene transfer, transposon-mediated insertions or change in outer membrane permeability. Therefore, constant efforts are being carried out to control the infections using various antibiotic therapies. Considering the severity of the acquired resistance, we developed a panel of strains of K. pneumoniae expressing different resistance profiles such as high-level penicillinase and AmpC production, extended spectrum beta-lactamases and carbapenemases. Bacterial strains expressing different resistance phenotypes were collected and examined for resistance genes, mutations and porin alterations contributing to the detected phenotypes. Using the Massive parallel sequencing (MPS) technology we have constructed and genotypically characterized the panel strains to elucidate the multidrug resistance. These panel strains can be used in the clinical laboratory as standard reference strains. In addition, these strains could be significant in the field of pharmaceuticals for the antibiotic drug testing to verify its efficiency on pathogens expressing various  resistances.

Antimicrobial activities of LCB10-0200, a novel siderophore cephalosporin, against the clinical isolates of Pseudomonas aeruginosa and other pathogens.

Infections caused by multidrug-resistant bacteria, including Pseudomonas aeruginosa, are threatening public health worldwide. Therefore, a novel antibacterial agent is needed to treat these infections. Here, we investigated the in vitro and in vivo activities of a novel siderophore-conjugated cephalosporin, LCB10-0200, against the clinical isolates of Gram-negative bacteria, including multidrug-resistant P. aeruginosa. In vitro susceptibility to LCB10-0200 was assessed by performing a two-fold agar dilution method, as described by the Clinical and Laboratory Standards Institute. LCB10-0200 showed the most potent antibacterial activity against P. aeruginosa clinical isolates, including ß-lactamase-producing strains. Moreover, LCB10-0200 showed better antibacterial activity against recently isolated clinical isolates than its comparators, except colistin. The in vivo activity of LCB10-0200 was examined using four mouse models of systemic, thigh, respiratory tract, and urinary tract infections. LCB10-0200 was more effective than ceftazidime in treating systemic, thigh, respiratory tract, and urinary tract infections caused by drug-susceptible and drug-resistant P. aeruginosa strains in these mouse models. Thus, the potent in vitro and in vivo activities of LCB10-0200 observed in the present study indicate that it has the potential for treating infections caused by Gram-negative bacteria, including P. aeruginosa.