A novel chemogenomic discovery platform identifies bioactive hits with rapid bactericidal activity against Mycobacteroides Abscessus.

Mycobacteroides abscessus (M. ab) infections are innately resistant to most currently available antibiotics and present a growing, poorly addressed medical need. The existing treatment regimens are lengthy and produce inadequate outcomes for many patients. Importantly, most clinically used drugs and drug candidates against M. ab are either bacteriostatic, or only weakly bactericidal. New strategies exploring a broader chemical space are urgently needed, as innovative agents in development are scarce and hit rates in large unbiased screens against the mycobacterium have been discouragingly low. Here we present a computational chemogenomics-driven approach to discovery of novel antibacterials that effectively reveals drug-like compounds active against M. ab, paired with small sets of predicted molecular targets for the compounds. Several of the bioactive hits identified exhibited rapid bactericidal, including sterilizing, activity against the mycobacterium, indicating that there are currently unexploited chemically tractable molecular mechanisms for rapid sterilization of M. ab. Interestingly, starvation, which typically induces drug tolerance, sensitized M. ab to some of the compounds, resulting in potencies similar to those of drugs in clinical use. The presented drug discovery platform has potential to identify highly differentiated prototype anti-infective molecules and thereby contribute to development of regimens for shorter treatment and improved outcomes for non-tuberculous mycobacterial infections.

An ultrasensitive and specific point-of-care CRISPR/Cas12 based lateral flow biosensor for the rapid detection of nucleic acids.

CRISPR/Cas systems have displayed remarkable potential in developing novel biosensing applications for nucleic acid detection owing to the collateral cleavage activity of Cas effector proteins (Cas12, Cas13, etc.). Despite tremendous progress in recent years, the existing CRISPR/Cas based biosensing platforms have several limitations, including reliance on proper amplification methods, expensive fluorescence detection equipment, or lateral flow biosensor (LFB). Herein, we report a simple, inexpensive, and ultrasensitive DNA probe based LFB with CRISPR/Cas and loop-mediated Isothermal Amplification (namely CIA). The concept behind this approach is a non-detectable test line on the LFB when the Cas effector protein collaterally cleaves the cognate target and an ssDNA reporter sequence. The CIA based LFB can detect as low as a single copy cloned Pseudomonas aeruginosa acyltransferase gene, 1 cfu/ml plasmid containing E. coli DH5α pure cultures, as well as clinical samples without DNA extraction/purification or advanced apparatuses. No cross-reactivity with other non-target bacteria was observed. The naked eye result readout was obtained in 15 min of LAMP amplification, 30 min of Cas12 reaction, and 5 min of LFB readout. This platform is robust and of low cost for on-site testing.

Role of the Cys154Arg Substitution in Ribosomal Protein L3 in Oxazolidinone Resistance in Mycobacterium tuberculosis.

We expressed the wild-type rplC and mutated rplC (Cys154Arg) genes, respectively, in Mycobacterium tuberculosis H37Ra and H37Rv in an attempt to delineate the role of rplC (Cys154Arg) regarding oxazolidinone resistance. An increase of the MICs of linezolid (LZD) and sutezolid (PNU-100480, PNU) against the recombinant mycobacteria with overexpressed rplC mutation (Cys154Arg) was found, suggesting the rplC gene is a determinant of bacillary susceptibilities to LZD and PNU.

Sequence analysis for detection of drug resistance in Mycobacterium tuberculosis complex isolates from the Central Region of Cameroon.

BACKGROUND: The potential of genetic testing to rapidly diagnose drug resistance has lead to the development of new diagnostic assays. However, prior to implementation in a given setting, the association of specific mutations with specific drug resistance phenotypes should be evaluated. The purpose of this study was to evaluate molecular markers in predicting drug resistance in the Central Region of Cameroon. RESULTS: From April 2010 and March 2011, 725 smear positive pulmonary tuberculosis patients were enrolled and all positive cultures were tested for drug susceptibility. A total of 63 drug resistant and 100 drug sensitive Mycobacterium tuberculosis complex clinical isolates were screened for genetic mutations in katG, inhA, ahpC, rpoB, rpsL, rrs, gidB and embCAB loci using DNA sequencing. Of the 44 isoniazid resistant (INHR) isolates (24 high level, 1 µg/ml and 20 low level, 0.2 µg/ml), 73% (32/44) carried the katG315 and/or the -15 inhA promoter mutations. Of the 24 high level INHR, 17 (70.8%) harbored katG315 mutation, 1 a point mutation (-15C → T) in the inhA promoter and 6 were (25.0%) wild types. Thus, for INHR high level detection, katG315 mutation had a specificity and a sensitivity of 100% and 70.8% respectively. Of the 20 low level INHR, 10 (50.0%) had a -15C → T mutation in the inhA promoter region, and 1 (2.2%) a -32G → A mutation in the ahpC promoter region. All of the 7 rifampicin resistant (RIFR) isolates carried mutations in the rpoB gene (at codons Ser531Leu (71.4%), His526Asp (14.3%), and Asp516Val (14.3%)). Of the 27 streptomycin resistant (SMR) isolates, 7 carried mutations at the rpsL and the gidB genes. 1 of the 2 ethambutol resistant (EMBR) isolates displayed a mutation in embB gene. CONCLUSION: This study provided the first molecular investigation assessing the correlation of phenotypic to genotypic characteristics on MTB isolates from the Central Region of Cameroon using DNA sequencing. Mutations on rpoB, katG315 and -15 point mutations in inhA promoter loci could be used as markers for RIF and INH -resistance detection respectively.