Drug induced reversion of antibiotic resistance is a promising way to combat multidrug resistant infections. However, lacking knowledge of mechanisms of drug resistance reversion impedes employing this approach in medicinal therapies. Induction of antibiotic resistance reversion by a new anti-tuberculosis drug FS-1 has been reported. FS-1 was used in this work in combination with standard anti-tuberculosis antibiotics in an experiment on laboratory guinea pigs infected with an extensively drug resistant (XDR) strain Mycobacterium tuberculosis SCAID 187.0. During the experimental trial, genetic changes in the population were analyzed by sequencing of M. tuberculosis isolates followed by variant calling. In total 11 isolates obtained from different groups of infected animals at different stages of disease development and treatment were sequenced. It was found that despite the selective pressure of antibiotics, FS-1 caused a counter-selection of drug resistant variants that speeded up the recovery of the infected animals from XDR tuberculosis. Drug resistance mutations reported in the genome of the initial strain remained intact in more sensitive isolates obtained in this experiment. Variant calling in the sequenced genomes revealed that the drug resistance reversion could be associated with a general increase in genetic heterogeneity of the population of M. tuberculosis. Accumulation of mutations in PpsA and PpsE subunits of phenolpthiocerol polyketide synthase was observed in the isolates treated with FS-1 that may indicate an increase of persisting variants in the population. It was hypothesized that FS-1 caused an active counter-selection of drug resistant variants from the population by aggravating the cumulated fitness cost of the drug resistance mutations. Action of FS-1 on drug resistant bacteria exemplified the theoretically predicted induced synergy mechanism of drug resistance reversion. An experimental model to study the drug resistance reversion phenomenon is hereby introduced.

21 Recent studies have demonstrated that antibiotic resistance in pathogenic bacteria could be 22 reverted to the drug sensitive phenotype by the treatment with the newly introduced iodine 23 containing nanomolecular complex, FS-1. Antibiotic resistance reversion has been verified as a 24 promising therapeutic approach to combat multidrug resistant infections. The mechanisms of 25 action, however, remain unclear. A collection strain, Escherichia coli ATCC showing 26 an extended spectrum of resistance to beta-lactam and aminoglycoside antibiotics was used in 27 this study as a model organism. The FS-1 treated culture and the negative control variant were 28 sequenced by PacBio RS II System following the SMRTbell 20-kb library preparation protocol.29 Total RNA samples of these strains were sequenced by Ion Torrent. It was shown that the 30 treatment with FS-1 caused a profound gene expression alternation switching the bacterial 31 metabolism to anaerobic respiration, increased anabolism, oxidative/acidic stress response and an 32 inhibition of many nutrient uptake systems. All this leads to an increase in the susceptibility to 33 antibiotics even when FS-1 is removed from the medium. The later fact implies an involvement 34 of epigenetic mechanisms in gene regulation and antibiotic resistance reversion. This hypothesis 35 was investigated by base-call kinetic analysis in PacBio reads and DNA methylation profiling in 36 the sequenced genomes. Several DNA motifs of adenosine and cytosine methylation were 37 identified. While the numbers of methylated sites in chromosomes and plasmids of both 38 genomes, NC and FS, were similar, the distribution of the methylated sites was different. It may 39 explain the observed long lasting effect of the treatment of E. coli with FS-1 on antibiotic 40 susceptibility of this model microorganism.41 Author summary 42 The emergence of multidrug resistant bacteria is a great concern, since the misuse of antibiotics 43 have caused a strong selective pressure for these resistant bacteria and various treatment options 44 are becoming ineffective. Drug induced reversion of antibiotic resistant is considering a 45 promising approach to address this problem. This study was set out to investigate genetic 46 mechanisms of action of a new iodine-containing nano-micelle drug FS-1 that induces antibiotic 47 resistance reversion in bacteria. Escherichia coli ATCC BAA-196 was used as a model of 48 multidrug resistant microorganisms. With this purpose in mind, we have sequenced the genomic 49 DNA and total RNA samples of E. coli cultivated on medium containing FS-1, served as an 50 experimental (FS) variant, and bacteria cultivated on normal medium, served as negative control 51 (NC). RNA sequencing showed a differential gene expression in the FS-1 treated strain that may 52 explain the observed increase in susceptibility to gentamicin and ampicillin. Application of the 53 3 rd generation sequencing technology, SMRT PacBio, allowed an unambiguous whole genome 54 assembly of NC and FS variants, a...

Reva et al. FS-1 Effect on S. aureus the culture FS. The selection against the antibiotic resistance in bacterial populations caused by abnormal epigenetic modifications exemplifies possible mechanisms of antibiotic resistance reversion induced by iodine-containing compounds. These finding will facilitate development of therapeutic agents against multidrug-resistant infections.

Newcastle disease virus (NDV) infects domesticated and wild birds throughout the world, and infections with virulent NDV strains continue to cause disease outbreaks in poultry and wild birds. To assess the evolutionary characteristics of 28 NDV strains isolated from chickens in Kazakhstan and Kyrgyzstan during 1998, 2000, 2001, 2003, 2004, and 2005, we investigated the phylogenetic relationships among these viruses and viruses described previously. For genotyping, fusion (F) gene phylogenetic analysis (nucleotide number 47-421) was performed using sequences of Kazakhstanian and Kyrgyzstanian isolates as compared to sequences of selected NDV strains from GenBank. Phylogenetic analysis demonstrated that the 14 newly characterized strains from years 1998 to 2001 belong to the NDV genotype VIIb, whereas the 14 strains isolated during 2003-2005 were of genotype VIId. All strains possessed a virulent fusion protein cleavage site (R-R-Q-R/K-R-F) and had intracerebral pathogenicity indexes in day-old chickens that ranged from 1.05 to 1.87, both properties typical of NDV strains classified in the mesogenic or velogenic pathotype.

BackgroundMycobacterium tuberculosis is one of the most dangerous human pathogens, the causative agent of tuberculosis. While this pathogen is considered as extremely clonal and resistant to horizontal gene exchange, there are many facts supporting the hypothesis that on the early stages of evolution the development of pathogenicity of ancestral Mtb has started with a horizontal acquisition of virulence factors. Episodes of infections caused by non-tuberculosis Mycobacteria reported worldwide may suggest a potential for new pathogens to appear. If so, what is the role of horizontal gene transfer in this process?ResultsAvailing of accessibility of complete genomes sequences of multiple pathogenic, conditionally pathogenic and saprophytic Mycobacteria, a genome comparative study was performed to investigate the distribution of genomic islands among bacteria and identify ontological links between these mobile elements. It was shown that the ancient genomic islands from M. tuberculosis still may be rooted to the pool of mobile genetic vectors distributed among Mycobacteria. A frequent exchange of genes was observed between M. marinum and several saprophytic and conditionally pathogenic species. Among them M. avium was the most promiscuous species acquiring genetic materials from diverse origins.ConclusionsRecent activation of genetic vectors circulating among Mycobacteria potentially may lead to emergence of new pathogens from environmental and conditionally pathogenic Mycobacteria. The species which require monitoring are M. marinum and M. avium as they eagerly acquire genes from different sources and may become donors of virulence gene cassettes to other micro-organisms.