Sublethal vancomycin-induced ROS mediating antibiotic resistance in Staphylococcus aureus

Efficacy and clinical potential of phage therapy in treating methicillin-resistant Staphylococcus aureus (MRSA) infections: A review

Staphylococcus aureus infections have already presented a substantial public health challenge, encompassing different clinical manifestations, ranging from bacteremia to sepsis and multi-organ failures. Among these infections, methicillin-resistant S. aureus (MRSA) is particularly alarming due to its well-documented resistance to multiple classes of antibiotics, contributing significantly to global mortality rates. Consequently, the urgent need for effective treatment options has prompted a growing interest in exploring phage therapy as a potential non-antibiotic treatment against MRSA infections. Phages represent a class of highly specific bacterial viruses known for their ability to infect certain bacterial strains. This review paper explores the clinical potential of phages as a treatment for MRSA infections due to their low toxicity and auto-dosing capabilities. The paper also discusses the synergistic effect of phage-antibiotic combination (PAC) and the promising results from in vitro and animal model studies, which could lead to extensive human clinical trials. However, clinicians need to establish and adhere to standard protocols governing phage administration and implementation. Prominent clinical trials are needed to develop and advance phage therapy as a non-antibiotic therapy intervention, meeting regulatory guidelines, logistical requirements, and ethical considerations, potentially revolutionizing the treatment of MRSA infections.

Epigenetic-Based Regulation of Transcriptome in Escherichia coli Adaptive Antibiotic Resistance

Adaptive antibiotic resistance is a transient metabolic adaptation of bacteria limiting their sensitivity to low, progressively increased, concentrations of antibiotics. Unlike innate and acquired resistance, adaptive resistance is dependent on the presence of antibiotics, and it disappears when the triggering factor is removed. Low concentrations of antibiotics are largely diffused in natural environments, in the food industry or in certain body compartments of humans when used therapeutically, or in animals when used for growth promotion. However, molecular mechanisms underlying this phenomenon are still poorly characterized. Here, we present experiments suggesting that epigenetic modifications, triggered by low concentrations of ampicillin, gentamicin, and ciprofloxacin, may modulate the sensitivity of bacteria to antibiotics. The epigenetic modifications we observed were paralleled by modifications of the expression pattern of many genes, including some of those that have been found mutated in strains with permanent antibiotic resistance. As the use of low concentrations of antibiotics is spreading in different contexts, our findings may suggest new targets and strategies to avoid adaptive antibiotic resistance. This might be very important as, in the long run, this transient adaptation may increase the chance, allowing the survival and the flourishing of bacteria populations, of the onset of mutations leading to stable resistance. IMPORTANCE In this study, we characterized the modifications of epigenetic marks and of the whole transcriptome in the adaptive response of Escherichia coli cells to low concentrations of ampicillin, gentamicin, and ciprofloxacin. As the transient adaptation does increase the chance of permanent resistance, possibly allowing the survival and flourishing of bacteria populations where casual mutations providing resistance may give an immediate advantage, the importance of this study is not only in the identification of possible molecular mechanisms underlying adaptive resistance to antibiotics, but also in suggesting new strategies to avoid adaptation.

The development of variation-based rifampicin resistance in Staphylococcus aureus deciphered through genomic and transcriptomic study

Rifampicin (RIF) resistance imposes a challenge on the antimicrobial treatment of pathogen infections. Figuring out the development mechanism of RIF resistance is critical to improving antimicrobial therapy strategy in clinics and biological treatment strategy of RIF polluted sewage in environmental engineering. The RIF resistance development of Staphylococcus aureus (S. aureus) with exposure to RIF at sub-inhibitory concentrations was comprehensively investigated via genomic and transcriptomic approaches in this study. RIF minimal inhibitory concentration (MIC) for S. aureus rapidly increased from 0.032 to 256 mg/L. Membrane permeability decrease, biofilm formation enhancement, and ROS production increase associated with RIF resistance were observed in RIF-induced strains. Through comparative genomic analysis, mutations in rpoB and rpoC were considered to be associated with RIF resistance in S. aureus mutants. Pan-genome-wide single-nucleotide variant analysis indicated that mutations at rpoB-1412, rpoB-1451, and rpoB-1457 were prevalent in 13849 public genomes of S. aureus, while mutations at rpoB-2256, and rpoC-3092 were first discovered in this study. The panorama of adaptative alteration of cellular physiological processes was observed via transcriptomic analysis. The oxidation pressure responses, metabolism, transporters, virulence factors, and multiple steps of DNA and RNA machinery were found to be perturbed by RIF in S. aureus.

Understanding a defensive response of methicillin-resistant Staphylococcus aureus (MRSA) after exposure to multiple cycles of sub-lethal blue Light

Blue light (BL) has showed bactericidal effectiveness against methicillin-resistant Staphylococcus aureus (MRSA), one of the major clinical pathogens with antibiotic resistance. Bacteria likely respond to the oxidative stress induced by BL, however, the defensive response is still unclear. This study was to reveal the phenotypic change of MRSA after exposed to 15 cycles of sub-lethal blue light illumination. The comparative transcriptomic results showed that the expression of peptidoglycan (PG) synthesis gene glmS was significantly up-regulated in the cells after the multiple cycle light treatment, and the biochemical analysis determined that the content of PG synthesized was increased by 25.86% when compared to that in control cells. Furthermore, significant thickening of the cell wall was observed under transmission electron microscope (P < 0.05). The light sensitivity of the tested MRSA strain was reduced after the multiple cycles light treatment, indicating the possibility of MRSA being more adaptive to the BL stress. The present study suggested that the multiple cycles of sub-lethal BL could change the light susceptibility of MRSA through thickening cell wall.

Neglected resistance risks: Cooperative resistance of antibiotic resistant bacteria influenced by primary soil components

Various antibiotic resistant bacteria (ARB) can thrive in soil and resist such environmental pressures as antibiotics through cooperative resistance, thereby promoting ARB retention and antibiotic resistance genes transmission. However, there has been finite knowledge in regard to the mechanisms and potential ecological risks of cooperative resistance in soil microbiome. In this study, soil minerals and organic matters were designed to treat a mixture of two Escherichia coli strains with different antibiotic resistance (E. coli DH5α/pUC19 and E. coli XL2-Blue) to determine how soil components affected cooperative resistance, and Luria-Bertani plates containing two antibiotics were used to observe dual-drug resistant bacteria (DRB) developed via cooperative resistance. Results showed quartz, humic acid, and biochar promoted E. coli XL2-Blue with high fitness costs, whereas kaolin, montmorillonite, and soot inhibited both strains. Using fluorescence microscope and PCR, it was speculated DRB could resist the antibiotic pressure via E. coli XL2-Blue coating E. coli DH5α/pUC19. E. coli DH5α/pUC19 dominated cooperative resistance. Correlation analysis and scanning electron microscope images indicated soil components influenced cooperative resistance. Biochar promoted cooperative resistance by increasing intracellular reactive oxygen species, thereby reducing the dominant strain concentration required for DRB development. Kaolin inhibited cooperative resistance the most, followed by soot and montmorillonite.

Identification of a novel antifungal backbone of naphthalimide thiazoles with synergistic potential for chemical and dynamic treatment

Aim: The high incidence and prevalence of fungal infections call for new antifungal drugs. This work was to develop naphthalimide thiazoles as potential antifungal agents. Results & methodology: These compounds showed significant antifungal potency toward some tested fungi. Especially, naphthalimide thiazole 4h with excellent anti-Candida tropicalis efficacy possessed good hemolysis level, low toxicity and no obvious resistance. Deciphering the mechanism showed that 4h interacted with DNA and disrupted the antioxidant defense system of C. tropicalis. Compound 4h also triggered membrane depolarization, leakage of cytoplasmic contents and LDH inhibition. Simultaneously, 4h rendered metabolic inactivation and eradicated the formed biofilms of C. tropicalis. Conclusion: The multifaceted synergistic effect initiated by naphthalimide thiazoles is a reasonable treatment window for prospective development.

Impact factors of the accumulation, migration and spread of antibiotic resistance in the environment

Antibiotic resistance is a great concern, which leads to global public health risks and ecological and environmental risks. The presence of antibiotic-resistant genes and antibiotic-resistant bacteria in the environment exacerbates the risk of spreading antibiotic resistance. Among them, horizontal gene transfer is an important mode in the spread of antibiotic resistance genes, and it is one of the reasons that the antibiotic resistance pollution has become increasingly serious. At the same time, free antibiotic resistance genes and resistance gene host bacterial also exist in the natural environment. They can not only affect horizontal gene transfer, but can also migrate and aggregate among environmental media in many ways and then continue to affect the proliferate and transfer of antibiotic resistance genes. All this shows the seriousness of antibiotic resistance pollution. Therefore, in this review, we reveal the sensitive factors affecting the distribution and spread of antibiotic resistance through three aspects: the influencing factors of horizontal gene transfer, the host bacteria of resistance genes and the migration of antibiotic resistance between environmental media. This review reveals the huge role of environmental migration in the spread of antibiotic resistance, and the environmental behavior of antibiotic resistance deserves wider attention. Meanwhile, extracellular antibiotic resistance genes and intracellular antibiotic resistance genes play different roles, so they should be studied separately.

Protective Functions of Group 3 Late Embryogenesis Abundant (G3LEA) Proteins in Enterococcus faecium During Vancomycin Treatment

Late embryogenesis abundant (LEA) proteins protect organisms from various environmental stresses; however, the underlying mechanism of LEA mediated therapeutic evasion is still unclear in both eukaryotes and prokaryotes. In this study, group 3 LEA protein (G3LEA) of vancomycin-resistant Enterococcus faecium under sublethal concentration of vancomycin stress was evaluated and shown to have two functions: the first is the reduction of reactive oxygen species (ROS) content, preventing apoptosis by suppressing apoptotic proteins Cas3 and MAOB, and the second is activating specific drug efflux pumps. Sublethal vancomycin model was established with using Propidium Iodide (PI) stain. Real-time PCR was conducted to evaluate the expression of G3lea. Flow cytometry and confocal microscope using Anti- G3LEA, anti- MAOB, and anti- Cas3 were performed to assess the expression of G3LEA. Under sublethal vancomycin stress, G3LEA is upregulated, suppressing the expression of apoptotic markers and increasing specific efflux markers. These results suggest that G3LEA protein suppresses antibiotic mediated apoptosis in prokaryotic cells and plays a key role in understanding and preventing antibiotic resistance.

Tylosin exposure reduces the susceptibility of Salmonella Typhimurium to florfenicol and tetracycline

BACKGROUND

Antibiotics exposure has been implicated in the emergence of bacterial strains that are resistant to structurally related or unrelated antibiotics. Tylosin is a macrolide antibiotic that has been administered to treat respiratory pathogenic bacteria in swine. Thus, this study was undertaken to evaluate the impact of exposure to a constant (3 μg/mL) and decreasing concentrations of tylosin on the susceptibility of Salmonella enterica serovar Typhimurium to various antibiotics.

RESULTS

S. Typhimurium strains exposed to tylosin for 12 and 24 h in the in vitro dynamic model demonstrated at least an eight-fold increase in the minimum inhibitory concentrations (MICs) of florfenicol and tetracycline. Exposure to tylosin extended the lag-time of the growth curve and enhanced the generation of reactive oxygen species. Gene expression analysis demonstrated up-regulation of the acrAB and tolC Salmonella efflux pump genes and its global regulators (marA and soxS). Besides, the expression of ompC gene was down-regulated in tylosin exposed S. Typhimurium.

CONCLUSION

Exposure to decreasing concentrations of tylosin could reduce the susceptibility of S. Typhimurium to florfenicol and tetracycline.

Antibacterial Activity of Colloidal Silver against Gram-Negative and Gram-Positive Bacteria

Due to the emergence of antimicrobial resistance, new alternative therapies are needed. Silver was used to treat bacterial infections since antiquity due to its known antimicrobial properties. Here, we aimed to evaluate the in vitro activity of colloidal silver (CS) against multidrug-resistant (MDR) Gram-negative and Gram-positive bacteria. A total of 270 strains (Acinetobacter baumannii (n = 45), Pseudomonas aeruginosa (n = 25), Escherichia coli (n = 79), Klebsiella pneumoniae (n = 58)], Staphylococcus aureus (n = 34), Staphylococcus epidermidis (n = 14), and Enterococcus species (n = 15)) were used. The minimal inhibitory concentration (MIC) of CS was determined for all strains by using microdilution assay, and time-kill curve assays of representative reference and MDR strains of these bacteria were performed. Membrane permeation and bacterial reactive oxygen species (ROS) production were determined in presence of CS. CS MIC₉₀ was 4-8 mg/L for all strains. CS was bactericidal, during 24 h, at 1× and 2× MIC against Gram-negative bacteria, and at 2× MIC against Gram-positive bacteria, and it did not affect their membrane permeabilization. Furthermore, we found that CS significantly increased the ROS production in Gram-negative with respect to Gram-positive bacteria at 24 h of incubation. Altogether, these results suggest that CS could be an effective treatment for infections caused by MDR Gram-negative and Gram-positive bacteria.

Metformin protects Escherichia coli from bleomycin-induced bactericide via enhanced generation of hydrogen peroxide

Bleomycin is a glycopeptide antibiotic that is widely employed in the therapy of a range of lymphomas and germ cell tumours. But the therapeutic efficacy of bleomycin is limited by development of lung fibrosis. The cytotoxicity of bleomycin is mostly ascribed to mitochondrial DNA (mtDNA) damage, while a protective effect of metformin against bleomycin-induced lung fibrosis results from the inhibition of mitochondrial complex I. Since mitochondria and bacteria have certain similarities in structure and function, we used Escherichia coli for simplification in the present work to investigate the relationship between metformin and bleomycin with apparently opposite effects on mitochondrial DNA damage. Bleomycin lethality to E. coli was ameliorated by metformin treatment accompanying further increase of the level of reactive oxygen species. Catalase but not superoxide dismutases attenuated the protective effect of metformin. Meanwhile, treatment with hydrogen peroxide enhanced the protection, indicating that metformin may protect E. coli from bleomycin-induced bactericide via enhanced generation of hydrogen peroxide. Moreover, silibinin, a hepatoprotective polyphenolic flavonoid attenuates the cytotoxicity of bleomycin to E. coli via enhanced generation of hydrogen peroxide as well. This bacterial model in place of mitochondria can provide us with easier screening for the molecules with capability of reducing the bleomycin side effect.

A Minor Subpopulation of Mycobacteria Inherently Produces High Levels of Reactive Oxygen Species That Generate Antibiotic Resisters at High Frequency From Itself and Enhance Resister Generation From Its Major Kin Subpopulation

Antibiotic-exposed bacteria produce elevated levels of reactive oxygen species (ROS), to which either they succumb or get mutated genome-wide to generate antibiotic resisters. We recently showed that mycobacterial cultures contained two subpopulations, short-sized cells (SCs; ∼10%) and normal/long-sized cells (NCs; ∼90%). The SCs were significantly more antibiotic-susceptible than the NCs. It implied that the SCs might naturally be predisposed to generate significantly higher levels of ROS than the NCs. This in turn could make the SCs more susceptible to antibiotics or generate more resisters as compared to the NCs. Investigation into this possibility showed that the SCs in the actively growing mid-log phase culture naturally generated significantly high levels of superoxide, as compared to the equivalent NCs, due to the naturally high expression of a specific NADH oxidase in the SCs. This caused labile Fe²⁺ leaching from 4Fe-4S proteins and elevated H₂O₂ formation through superoxide dismutation. Thus, the SCs of both Mycobacterium smegmatis and Mycobacterium tuberculosis inherently contained significantly higher levels of H₂O₂ and labile Fe²⁺ than the NCs. This in turn produced significantly higher levels of hydroxyl radical through Fenton reaction, promoting enhanced antibiotic resister generation from the SCs than from the NCs. The SCs, when mixed back with the NCs, at their natural proportion in the actively growing mid-log phase culture, enhanced antibiotic resister generation from the NCs, to a level equivalent to that from the unfractionated whole culture. The enhanced antibiotic resister generation from the NCs in the reconstituted SCs-NCs natural mixture was found to be due to the high levels of H₂O₂ secreted by the SCs. Thus, the present work unveils and documents the metabolic designs of two mycobacterial subpopulations where one subpopulation produces high ROS levels, despite higher susceptibility, to generate significantly higher number of antibiotic resisters from itself and to enhance resister generation from its kin subpopulation. These findings show the existence of an inherent natural mechanism in both the non-pathogenic and pathogenic mycobacteria to generate antibiotic resisters. The presence of the SCs and the NCs in the pulmonary tuberculosis patients’ sputum, reported by us earlier, alludes to the clinical significance of the study.

Non-antibiotic antimicrobial triclosan induces multiple antibiotic resistance through genetic mutation

Antibiotic resistance poses a major threat to public health. Overuse and misuse of antibiotics are generally recognized as the key factors contributing to antibiotic resistance. However, whether non-antibiotic, anti-microbial (NAAM) chemicals can directly induce antibiotic resistance is unclear. We aim to investigate whether the exposure to a NAAM chemical triclosan (TCS) has an impact on inducing antibiotic resistance on Escherichia coli. Here, we report that at a concentration of 0.2 mg/L TCS induces multi-drug resistance in wild-type Escherichia coli after 30-day TCS exposure. The oxidative stress induced by TCS caused genetic mutations in genes such as fabI, frdD, marR, acrR and soxR, and subsequent up-regulation of the transcription of genes encoding beta-lactamases and multi-drug efflux pumps, together with down-regulation of genes related to membrane permeability. The findings advance our understanding of the potential role of NAAM chemicals in the dissemination of antibiotic resistance in microbes, and highlight the need for controlling biocide applications.

Cyclic di-adenosine monophosphate (c-di-AMP) is required for osmotic regulation in Staphylococcus aureus but dispensable for viability in anaerobic conditions

Cyclic di-adenosine monophosphate (c-di-AMP) is a recently discovered signaling molecule important for the survival of Firmicutes, a large bacterial group that includes notable pathogens such as Staphylococcus aureus However, the exact role of this molecule has not been identified. dacA, the S. aureus gene encoding the diadenylate cyclase enzyme required for c-di-AMP production, cannot be deleted when bacterial cells are grown in rich medium, indicating that c-di-AMP is required for growth in this condition. Here, we report that an S. aureus dacA mutant can be generated in chemically defined medium. Consistent with previous findings, this mutant had a severe growth defect when cultured in rich medium. Using this growth defect in rich medium, we selected for suppressor strains with improved growth to identify c-di-AMP-requiring pathways. Mutations bypassing the essentiality of dacA were identified in alsT and opuD, encoding a predicted amino acid and osmolyte transporter, the latter of which we show here to be the main glycine betaine-uptake system in S. aureus. Inactivation of these transporters likely prevents the excessive osmolyte and amino acid accumulation in the cell, providing further evidence for a key role of c-di-AMP in osmotic regulation. Suppressor mutations were also obtained in hepS, hemB, ctaA, and qoxB, coding proteins required for respiration. Furthermore, we show that dacA is dispensable for growth in anaerobic conditions. Together, these findings reveal an essential role for the c-di-AMP signaling network in aerobic, but not anaerobic, respiration in S. aureus.

Exposure to sub-inhibitory concentrations of gentamicin, ciprofloxacin and cefotaxime induces multidrug resistance and reactive oxygen species generation in meticillin-sensitive Staphylococcus aureus

PURPOSE

The role of antibiotics below their MIC in the development of bacterial drug resistance is becoming increasingly important. We investigated the effect of sub-MICs of bactericidal antibiotics on the susceptibility pattern of Staphylococcus aureus and evaluated the role of free radicals.

METHODOLOGY

A total of 12 S. aureus strains were recovered from pus samples and their antibiograms determined. The test isolates were treated with sub-MIC levels of tetracycline, gentamicin, ciprofloxacin and cefotaxime. Alterations in their respective breakpoints were observed along with measurements of free radical generation by nitro blue tetrazolium test.Results/Key findings. Gentamicin, ciprofloxacin and cefotaxime exposure significantly altered the breakpoints of exposed isolates against several tested antibiotics and higher levels of free radicals were generated after antibiotic exposure.

CONCLUSIONS

Our study demonstrates that sub-MIC levels of antimicrobials can lead to resistance and cross-resistance across several classes of antibiotics in wild strains of S. aureus, possibly by free radical production. The molecular mechanisms behind the acquisition of drug resistance at low antibiotic concentrations and the specific target genes of reactive oxygen speciesneed to be explored further.

De Novo Emergence of Genetically Resistant Mutants of Mycobacterium tuberculosis from the Persistence Phase Cells Formed against Antituberculosis Drugs In Vitro

Bacterial persisters are a subpopulation of cells that can tolerate lethal concentrations of antibiotics. However, the possibility of the emergence of genetically resistant mutants from antibiotic persister cell populations, upon continued exposure to lethal concentrations of antibiotics, remained unexplored. In the present study, we found that Mycobacterium tuberculosis cells exposed continuously to lethal concentrations of rifampin (RIF) or moxifloxacin (MXF) for prolonged durations showed killing, RIF/MXF persistence, and regrowth phases. RIF-resistant or MXF-resistant mutants carrying clinically relevant mutations in the rpoB or gyrA gene, respectively, were found to emerge at high frequency from the RIF persistence phase population. A Luria-Delbruck fluctuation experiment using RIF-exposed M. tuberculosis cells showed that the rpoB mutants were not preexistent in the population but were formed de novo from the RIF persistence phase population. The RIF persistence phase M. tuberculosis cells carried elevated levels of hydroxyl radical that inflicted extensive genome-wide mutations, generating RIF-resistant mutants. Consistent with the elevated levels of hydroxyl radical-mediated genome-wide random mutagenesis, MXF-resistant M. tuberculosis gyrA de novo mutants could be selected from the RIF persistence phase cells. Thus, unlike previous studies, which showed emergence of genetically resistant mutants upon exposure of bacteria for short durations to sublethal concentrations of antibiotics, our study demonstrates that continuous prolonged exposure of M. tuberculosis cells to lethal concentrations of an antibiotic generates antibiotic persistence phase cells that form a reservoir for the generation of genetically resistant mutants to the same antibiotic or another antibiotic. These findings may have clinical significance in the emergence of drug-resistant tubercle bacilli.

The Role of Reactive Oxygen Species in Antibiotic-Mediated Killing of Bacteria

Recently, it was proposed that there is a common mechanism behind the activity of bactericidal antibiotics, involving the production of reactive oxygen species (ROS). However, the involvement of ROS in antibiotic-mediated killing has become the subject of much debate. In the present review, we provide an overview of the data supporting the ROS hypothesis; we also present data that explain the contradictory results often obtained when studying antibiotic-induced ROS production. For this latter aspect we will focus on the importance of taking the experimental setup into consideration and on the importance of some technical aspects of the assays typically used. Finally, we discuss the link between ROS production and toxin-antitoxin modules, and present an overview of implications for treatment.

Identifying and Tackling Emergent Vulnerability in Drug-Resistant Mycobacteria

The global mechanisms and associated molecular alterations that occur in drug-resistant mycobacteria are poorly understood. To address this, we obtain genomics data and then construct a genome-scale response network in isoniazid-resistant Mycobacterium smegmatis and apply a network-mining algorithm. Through this, we decipher global alterations in an unbiased manner and identify emergent vulnerabilities in resistant bacilli, of which redox response was prominent. Using phenotypic profiling, we find that resistant bacilli exhibit collateral sensitivity to several compounds that block antioxidant responses. We find that nanogram/milliliter concentrations of ebselen, vancomycin, and phenylarsine oxide, in combination with isoniazid, are highly effective against Mycobacterium tuberculosis H37Rv and three clinical drug-resistant strains. Dynamic measurements of cytoplasmic redox potential revealed a surprisingly diminished capacity of clinical drug-resistant strains to counteract oxidative stress, providing a mechanistic basis for efficient and synergistic mycobactericidal activity of the drug combinations. Ebselen and vancomycin appear to be promising repurposable drugs.

Mycobacteriophage SWU1 gp39 can potentiate multiple antibiotics against Mycobacterium via altering the cell wall permeability

M. tuberculosis is intrinsically tolerant to many antibiotics largely due to the imperviousness of its unusual mycolic acid-containing cell wall to most antimicrobials. The emergence and increasingly widespread of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) revitalized keen interest in phage-inspired therapy. SWU1gp39 is a novel gene from mycobacteriophage SWU1 with unknown function. SWU1gp39 expressed in M. smegmatis conferred the host cell increased susceptibility to multiple antibiotics, including isoniazid, erythromycin, norfloxacin, ampicillin, ciprofloxacin, ofloxacin, rifampicin and vancomycin, and multiple environment stresses such as H2O2, heat shock, low pH and SDS. By using EtBr/Nile red uptake assays, WT-pAL-gp39 strain showed higher cell wall permeability than control strain WT-pAL. Moreover, the WT-pAL-gp39 strain produced more reactive oxygen species and reduced NAD(+)/NADH ratio. RNA-Seq transcriptomes of the WT-pAL-gp39 and WT-pAL revealed that the transcription of 867 genes was differentially regulated, including genes associated with lipid metabolism. Taken together, our results implicated that SWU1gp39, a novel gene from mycobacteriophage, disrupted the lipid metabolism of host and increased cell wall permeability, ultimately potentiated the efficacy of multiple antibiotics and stresses against mycobacteria.

Mycobacteriophage SWU1 gp39 can potentiate multiple antibiotics against Mycobacterium via altering the cell wall permeability

M. tuberculosis is intrinsically tolerant to many antibiotics largely due to the imperviousness of its unusual mycolic acid-containing cell wall to most antimicrobials. The emergence and increasingly widespread of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) revitalized keen interest in phage-inspired therapy. SWU1gp39 is a novel gene from mycobacteriophage SWU1 with unknown function. SWU1gp39 expressed in M. smegmatis conferred the host cell increased susceptibility to multiple antibiotics, including isoniazid, erythromycin, norfloxacin, ampicillin, ciprofloxacin, ofloxacin, rifampicin and vancomycin, and multiple environment stresses such as H2O2, heat shock, low pH and SDS. By using EtBr/Nile red uptake assays, WT-pAL-gp39 strain showed higher cell wall permeability than control strain WT-pAL. Moreover, the WT-pAL-gp39 strain produced more reactive oxygen species and reduced NAD(+)/NADH ratio. RNA-Seq transcriptomes of the WT-pAL-gp39 and WT-pAL revealed that the transcription of 867 genes was differentially regulated, including genes associated with lipid metabolism. Taken together, our results implicated that SWU1gp39, a novel gene from mycobacteriophage, disrupted the lipid metabolism of host and increased cell wall permeability, ultimately potentiated the efficacy of multiple antibiotics and stresses against mycobacteria.