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Yi X, Feng M, He F, Xiao Z, Wang Y, Wang S, Yao H. Multi-omics analysis explores the impact of ofloxacin pressure on the metabolic state in Escherichia coli. J Glob Antimicrob Resist 2024:S2213-7165(24)00151-6. [PMID: 39168372 DOI: 10.1016/j.jgar.2024.07.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 05/17/2024] [Accepted: 07/20/2024] [Indexed: 08/23/2024] Open
Abstract
OBJECTIVES The rising threat of antibiotic resistance poses a significant challenge to public health. The research on the new direction of resistance mechanisms is crucial for overcoming this hurdle. This study examines metabolic changes by comparing sensitive and experimentally induced ofloxacin-resistant Escherichia coli (E. coli) strains using multi-omics analyses, aiming to provide novel insights into bacterial resistance. METHODS An ofloxacin-resistant E. coli strain was selected by being exposed to high concentration of ofloxacin. Comparative analyses involving transcriptomics, proteomics, and acetylomics were conducted between the wild-type (WT) and the ofloxacin-resistant (Re-OFL) strains. Enrichment pathways of differentially expressed genes, proteins and acetylated proteins between the two strains were analyzed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) method. In addition, the metabolic network of E. coli was mapped using integrated multi-omics analysis strategies. RESULTS We identified significant differences in 2775 mRNAs, 1062 proteins, and 1015 acetylated proteins between WT and Re-OFL strains. Integrated omics analyses revealed that the common alterations enriched in metabolic processes, particularly the glycolytic pathway. Further analyses demonstrated that 14 metabolic enzymes exhibited upregulated acetylation levels and downregulated transcription and protein levels. Moreover, seven of these metabolic enzymes (fba, tpi, gapA, pykA, sdhA, fumA, and mdh) were components related to the glycolytic pathway. CONCLUSION The changes of metabolic enzymes induced by antibiotics seem to be a key factor for E. coli to adapt to the pressure of antibiotics, which shed new light on understanding the adaptation mechanism when responding to ofloxacin pressure.
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Affiliation(s)
- Xiaoyu Yi
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China
| | - Miao Feng
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China
| | - Feng He
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China
| | - Zonghui Xiao
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China
| | - Yichuan Wang
- Beijing Friendship Hospital, Capital Medical University, Beijing, 100050, China
| | - Shuowen Wang
- Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Hailan Yao
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China.
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Feng M, Yi X, Feng Y, He F, Xiao Z, Yao H. Acetyl-proteome profiling revealed the role of lysine acetylation in erythromycin resistance of Staphylococcus aureus. Heliyon 2024; 10:e35326. [PMID: 39170456 PMCID: PMC11336636 DOI: 10.1016/j.heliyon.2024.e35326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 07/21/2024] [Accepted: 07/26/2024] [Indexed: 08/23/2024] Open
Abstract
Background Staphylococcus aureus (S. aureus), a prevalent human pathogen known for its propensity to cause severe infections, has exhibited a growing resistance to antibiotics. Lysine acetylation (Kac) is a dynamic and reversible protein post-translational modification (PTM), played important roles in various physiological functions. Recent studies have shed light on the involvement of Kac modification in bacterial antibiotic resistance. However, the precise relationship between Kac modification and antibiotic resistance in S. aureus remains inadequately comprehended. Methods We compared the differential expression of acetylated proteins between erythromycin-resistant (Ery-R) and erythromycin-susceptible (Ery-S) strains of S. aureus by 4D label-free quantitative proteomics technology. Additionally, we employed motif analysis, functional annotation and PPI network to investigate the acetylome landscape and heterogeneity of S. aureus. Furthermore, polysome profiling experiments were performed to assess the translational status of ribosome. Results 6791 Kac sites were identified on 1808 proteins in S. aureus, among which 1907 sites in 483 proteins were quantified. A total of 548 Kac sites on 316 acetylated proteins were differentially expressed by erythromycin pressure. The differentially acetylated proteins were primarily enriched in ribosome assembly, glycolysis and lysine biosynthesis. Bioinformatic analyses implied that Kac modification of ribosomal proteins may play an important role in erythromycin resistance of S. aureus. Western bolt and polysome profiling experiments indicated that the increased Kac levels of ribosomal proteins in the resistant strain may partially offset the inhibitory effect of erythromycin on ribosome function. Conclusions Our findings confirm that Kac modification is related to erythromycin resistance in S. aureus and emphasize the potential roles of ribosomal proteins. These results expand our current knowledge of antibiotic resistance mechanisms, potentially guiding future research on PTM-mediated antibiotic resistance.
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Affiliation(s)
- Miao Feng
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China
| | - Xiaoyu Yi
- Capital Institute of Pediatrics, Beijing, 100020, China
| | - Yanling Feng
- Department of Bacteriology, Capital Institute of Pediatrics, Beijing, 100020, China
| | - Feng He
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China
| | - Zonghui Xiao
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China
| | - Hailan Yao
- Department of Biochemistry and Immunology, Capital Institute of Pediatrics, Beijing, 100020, China
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Boucherabine S, Giddey A, Nassar R, Al-Hroub HM, Mohamed L, Harb M, Soares NC, Senok A. Proteomic and metabolomic profiling of methicillin resistant versus methicillin sensitive Staphylococcus aureus using a simultaneous extraction protocol. Front Microbiol 2024; 15:1402796. [PMID: 38993491 PMCID: PMC11238212 DOI: 10.3389/fmicb.2024.1402796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Accepted: 05/13/2024] [Indexed: 07/13/2024] Open
Abstract
Background Understanding the biology of methicillin resistant Staphylococcus aureus (MRSA) is crucial to unlocking insights for new targets in our fight against this antimicrobial resistant priority pathogen. Although proteomics and metabolomic profiling offer the potential to elucidating such biological markers, reports of methodological approaches for carrying this out in S. aureus isolates remain limited. We describe the use of a dual-functionality methanol extraction method for the concurrent extraction of protein and metabolites from S. aureus and report on the comparative analysis of the proteomic and metabolomic profiles of MRSA versus methicillin sensitive S. aureus (MSSA). Methods Bacterial reference strains MRSA ATCC43300 and MSSA ATCC25923 were used. The conventional urea methodology was used for protein extraction and a methanol based method was used for concurrent proteins and metabolites extraction. Proteomic and metabolomic profiling was carried out using TimsTOF mass spectrometry. Data processing was carried out using the MaxQuant version 2.1.4.0. Results This study represents the first report on the utilization of the methanol extraction method for concurrent protein and metabolite extraction in Gram positive bacteria. Our findings demonstrate good performance of the method for the dual extraction of proteins and metabolites from S. aureus with demonstration of reproducibility. Comparison of MRSA and MSSA strains revealed 407 proteins with significantly different expression levels. Enrichment analysis of those proteins revealed distinct pathways involved in fatty acid degradation, metabolism and beta-lactam resistance. Penicillin-binding protein PBP2a, the key determinant of MRSA resistance, exhibited distinct expression patterns in MRSA isolates. Metabolomic analysis identified 146 metabolites with only one exclusive to the MRSA. The enriched pathways identified were related to arginine metabolism and biosynthesis. Conclusion Our findings demonstrate the effectiveness of the methanol-based dual-extraction method, providing simultaneous insights into the proteomic and metabolomic landscapes of S. aureus strains. These findings demonstrate the utility of proteomic and metabolomic profiling for elucidating the biological basis of antimicrobial resistance.
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Affiliation(s)
- Syrine Boucherabine
- College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
| | - Alexander Giddey
- Center for Applied and Translational Genomics, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
| | - Rania Nassar
- College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
- School of Dentistry, Cardiff University, Cardiff, United Kingdom
| | - Hamza M. Al-Hroub
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, United Arab Emirates
| | - Lobna Mohamed
- College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
| | - Mohammad Harb
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, United Arab Emirates
- Department of Medicinal Chemistry, College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates
| | - Nelson Cruz Soares
- Research Institute of Medical and Health Sciences, University of Sharjah, Sharjah, United Arab Emirates
- Department of Medicinal Chemistry, College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates
- Laboratory of Proteomics, Department of Human Genetics, National Institute of Health Doutor Ricardo Jorge (INSA), Lisbon, Portugal
- Centre for Toxicogenomics and Human Health (ToxOmics), NOVA School/Faculdade de Lisboa, Lisbon, Portugal
| | - Abiola Senok
- College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates
- School of Dentistry, Cardiff University, Cardiff, United Kingdom
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Alves J, Vrieling M, Ring N, Yebra G, Pickering A, Prajsnar TK, Renshaw SA, Fitzgerald JR. Experimental evolution of Staphylococcus aureus in macrophages: dissection of a conditional adaptive trait promoting intracellular survival. mBio 2024; 15:e0034624. [PMID: 38682911 PMCID: PMC11237485 DOI: 10.1128/mbio.00346-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Accepted: 03/26/2024] [Indexed: 05/01/2024] Open
Abstract
Staphylococcus aureus is a major pathogen associated with important diseases in humans and animals. Macrophages are a key component of the innate immune response to S. aureus infection and play a major role in disease outcomes. To investigate the adaptive evolution of S. aureus in response to macrophages, we developed an experimental infection assay. S. aureus strains representing major human epidemic clones were passaged many times in a macrophage cell line, accumulating mutations in an array of genomic loci. Phenotypic analysis revealed the emergence of a lineage exhibiting increased survival in macrophages and human blood, and resistance to vancomycin. The evolved lineage exhibited a previously undescribed small colony variant (SCV) phenotype characterized by hyper-pigmentation, which resulted from a missense mutation in rsbW. Notably, the novel SCV was a conditional adaptive trait that was unstable in nutrient-replete conditions in vitro, rapidly converting from hyper-pigmented SCV to a non-pigmented large colony variant via spontaneous sigB deletion events. Importantly, we identified similar deletions in the genome sequences of a limited number of clinical S. aureus isolates from public databases, indicating that related events may occur during clinical infection. Experimental infection of zebrafish did not reveal a difference in virulence between parent and novel SCV but demonstrated an in vivo fitness cost for the compensatory sigB deletion events. Taken together, we report an experimental evolutionary approach for investigating bacterial innate immune cell interactions, revealing a conditional adaptation that promotes S. aureus survival in macrophages and resistance to vancomycin. IMPORTANCE Staphylococcus aureus is an important human bacterial pathogen. The host response to S. aureus involves the production of innate immune cells such as macrophages which are important for fighting infection. Here we report a new model of experimental evolution for studying how S. aureus can evade killing by macrophages. We identified a novel adaptive phenotype that promotes survival in macrophages and blood and resistance to antibiotics. The phenotype is lost rapidly upon growth in nutrient-rich conditions via disruption of the alternative sigma factor sigB, revealing a conditional niche-specific fitness advantage. Genomic analysis of clinical isolates suggests similar adaptations may occur during human infections. Our model may be used broadly to identify adaptations of S. aureus to the innate immune response.
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Affiliation(s)
- Joana Alves
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, Edinburgh, United Kingdom
| | - Manouk Vrieling
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, Edinburgh, United Kingdom
| | - Natalie Ring
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, Edinburgh, United Kingdom
| | - Gonzalo Yebra
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, Edinburgh, United Kingdom
| | - Amy Pickering
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, Edinburgh, United Kingdom
| | - Tomasz K. Prajsnar
- Florey Institute, Bateson Centre and Division of Clinical Medicine, School of Medicine and Population Health, Sheffield, United Kingdom
| | - Stephen A. Renshaw
- Florey Institute, Bateson Centre and Division of Clinical Medicine, School of Medicine and Population Health, Sheffield, United Kingdom
| | - J. Ross Fitzgerald
- The Roslin Institute, University of Edinburgh, Easter Bush, Midlothian, Edinburgh, United Kingdom
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Cheng A, Zhang Y, Sun J, Huang D, Sulaiman JE, Huang X, Wu L, Ye W, Wu C, Lam H, Shi Y, Qian PY. Pterosin sesquiterpenoids from Pteris laeta Wall. ex Ettingsh. protect cells from glutamate excitotoxicity by modulating mitochondrial signals. JOURNAL OF ETHNOPHARMACOLOGY 2023; 308:116308. [PMID: 36822346 DOI: 10.1016/j.jep.2023.116308] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 02/09/2023] [Accepted: 02/19/2023] [Indexed: 06/18/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE The genus Pteris (Pteridaceae) has been used as a traditional herb for a long time. In particular, Pteris laeta Wall. ex Ettingsh. has been widely used in traditional Chinese medicine to treat nervous system diseases and some pterosin sesquiterpenes from Pteris show neuroprotective activity, but their underlying molecular mechanisms remain elusive. Therefore, to investigate the neuroprotective activity and working mechanism of pterosin sesquiterpenes from P. laeta Wall. ex Ettingsh. will provide a better understanding and guidance in using P. laeta Wall. ex Ettingsh. as a traditional Chinese medicine. AIM OF THE STUDY We aim to develop effective treatments for neurodegenerative diseases from pterosin sesquiterpenes by evaluating their neuroprotective activity and investigating their working mechanisms. MATERIALS AND METHODS Primary screening on the glutamate-induced excitotoxicity cell model was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. Fluorescent-activated cell sorting (FACS) was used to analyze the activation level of glutamate receptors and mitochondria membrane potential after treatment. Transcriptomics and proteomics analysis was performed to identify possible targets of pterosin B. The key pathways were enriched by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis through the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The core targets were visualized by a protein-protein interaction network using STRING. The mRNA and protein expressions were evaluated using real-time quantitative polymerase chain reaction (Q-PCR) and western blot, respectively. Immunocytochemistry was performed to monitor mitochondrial and apoptotic proteins. Cellular reactive oxygen species (ROS) were measured by ROS assay, and Ca2+ was stained with Fluo-4 AM to quantify intracellular Ca2+ levels. RESULTS We found pterosin B from Pteris laeta Wall. ex Ettingsh. showed significant neuroprotective activity against glutamate excitotoxicity, enhancing cell viability from 43.8% to 105% (p-value: <0.0001). We demonstrated that pterosin B worked on the downstream signaling pathways of glutamate excitotoxicity rather than directly blocking the activation of glutamate receptors. Pterosin B restored mitochondria membrane potentials, alleviated intracellular calcium overload from 107.4% to 95.47% (p-value: 0.0006), eliminated cellular ROS by 36.55% (p-value: 0.0143), and partially secured cells from LPS-induced inflammation by increasing cell survival from 46.75% to 58.5% (p-value: 0.0114). Notably, pterosin B enhanced the expression of nuclear factor-erythroid factor 2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1) by 2.86-fold (p-value: 0.0006) and 4.24-fold (p-value: 0.0012), and down-regulated Kelch-like ECH-associated protein 1 (KEAP1) expression by 2.5-fold (p-value: 0.0107), indicating that it possibly promotes mitochondrial biogenesis and mitophagy to maintain mitochondria quality control and homeostasis, and ultimately inhibits apoptotic cell death. CONCLUSIONS Our work revealed that pterosin B protected cells from glutamate excitotoxicity by targeting the downstream mitochondrial signals, making it a valuable candidate for developing potential therapeutic agents in treating neurodegenerative diseases.
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Affiliation(s)
- Aifang Cheng
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458, China; Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Hong Kong, 999077, China
| | - Yan Zhang
- School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, 510515, China; Institute for Advancing Translational Medicine in Bone and Joint Diseases (TMBJ), School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, 999077, China
| | - Jin Sun
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Duli Huang
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458, China; Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Hong Kong, 999077, China
| | - Jordy Evan Sulaiman
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, 999077, China
| | - Xin Huang
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458, China; Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Hong Kong, 999077, China
| | - Long Wu
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, 999077, China
| | - Wenkang Ye
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458, China; Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Hong Kong, 999077, China; SZU-HKUST Joint Ph.D. Program in Marine Environmental Science, Shenzhen University, Shenzhen, 518060, China
| | - Chuanhai Wu
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458, China; Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Hong Kong, 999077, China
| | - Henry Lam
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong, 999077, China
| | - Yusheng Shi
- National-Local Joint Engineering Research Center for Drug-Research and Development (R&D) of Neurodegenerative Diseases, Dalian Medical University, Dalian, 116044, China; Academy of Integrative Medicine, Dalian Medical University, Dalian, 116044, China.
| | - Pei-Yuan Qian
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, 511458, China; Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Hong Kong, 999077, China.
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Comparison of Phenotype and Genotype Virulence and Antimicrobial Factors of Salmonella Typhimurium Isolated from Human Milk. Int J Mol Sci 2023; 24:ijms24065135. [PMID: 36982209 PMCID: PMC10048834 DOI: 10.3390/ijms24065135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 03/03/2023] [Accepted: 03/04/2023] [Indexed: 03/11/2023] Open
Abstract
Salmonella is a common foodborne infection. Many serovars belonging to Salmonella enterica subsp. enterica are present in the gut of various animal species. They can cause infection in human infants via breast milk or cross-contamination with powdered milk. In the present study, Salmonella BO was isolated from human milk in accordance with ISO 6579-1:2017 standards and sequenced using whole-genome sequencing (WGS), followed by serosequencing and genotyping. The results also allowed its pathogenicity to be predicted. The WGS results were compared with the bacterial phenotype. The isolated strain was found to be Salmonella enterica subsp. enterica serovar Typhimurium 4:i:1,2_69M (S. Typhimurium 69M); it showed a very close similarity to S. enterica subsp. enterica serovar Typhimurium LT2. Bioinformatics sequence analysis detected eleven SPIs (SPI-1, SPI-2, SPI-3, SPI-4, SPI-5, SPI-9, SPI-12, SPI-13, SPI-14, C63PI, CS54_island). Significant changes in gene sequences were noted, causing frameshift mutations in yeiG, rfbP, fumA, yeaL, ybeU (insertion) and lpfD, avrA, ratB, yacH (deletion). The sequences of several proteins were significantly different from those coded in the reference genome; their three-dimensional structure was predicted and compared with reference proteins. Our findings indicate the presence of a number of antimicrobial resistance genes that do not directly imply an antibiotic resistance phenotype.
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Poshvina DV, Dilbaryan DS, Kasyanov SP, Sadykova VS, Lapchinskaya OA, Rogozhin EA, Vasilchenko AS. Staphylococcus aureus is able to generate resistance to novel lipoglycopeptide antibiotic gausemycin A. Front Microbiol 2022; 13:963979. [PMID: 36246291 PMCID: PMC9558223 DOI: 10.3389/fmicb.2022.963979] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 09/14/2022] [Indexed: 11/13/2022] Open
Abstract
Gausemycin A is the first member of the novel lipoglycopeptides family produced by Streptomyces roseoflavus INA-Ac-5812. Gausemycin A has a pronounced bactericidal activity against methicillin-resistant Staphylococcus aureus. However, the ability of S. aureus to be resistant to gausemycin A has not been investigated yet. Using serial passaging, we have obtained the resistant variant S. aureus 5812R, which is 80 times more resistant compared to the parent strain. Susceptibility testing of S. aureus 5812R revealed the acquisition of cross-resistance to daptomycin, cefazolin, tetracycline, and gentamicin, while the resistance to vancomycin, nisin, and ramoplanin was absent. Whole genome sequencing revealed single nucleotide polymorphism (SNP) and deletions in S. aureus 5812R, among which are genes encoding efflux pump (sepA), the two-component Kdp system (kdpE), and the component of isoprenoid biosynthesis pathway (hepT). Phenotypically, S. aureus 5812R resembles a small-colony variant, as it is slow-growing, forms small colonies, and is deficient in pigments. Profiling of fatty acids (FA) composition constituting the cytoplasmic membrane of S. aureus 5812R revealed the prevalence of anteiso-branched FA, while straight FA was slightly less present. The evidence also showed that the gausemycin A-resistant strain has increased expression of the cls2 gene of the cardiolipin synthase. The performed checkerboard assay pointed out that the combination of gausemycin A and ciprofloxacin showed a synergistic effect against S. aureus 5812R.
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Affiliation(s)
- Darya V. Poshvina
- Laboratory of Antimicrobial Resistance, Institute of Environmental and Agricultural Biology (X-BIO), Tyumen State University, Tyumen, Russia
| | - Diana S. Dilbaryan
- Laboratory of Antimicrobial Resistance, Institute of Environmental and Agricultural Biology (X-BIO), Tyumen State University, Tyumen, Russia
| | - Sergey P. Kasyanov
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Vladivostok, Russia
| | | | | | - Eugene A. Rogozhin
- Gause Institute of New Antibiotics, Moscow, Russia
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry Russian Academy of Sciences, Moscow, Russia
| | - Alexey S. Vasilchenko
- Laboratory of Antimicrobial Resistance, Institute of Environmental and Agricultural Biology (X-BIO), Tyumen State University, Tyumen, Russia
- *Correspondence: Alexey S. Vasilchenko
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Long L, Sulaiman JE, Xiao Y, Cheng A, Wang R, Malit JJ, Wong WC, Liu W, Li YX, Chen F, Lam H, Qian PY. Mode of action of elasnin as biofilm formation eradicator of methicillin-resistant Staphylococcus aureus. Front Microbiol 2022; 13:967845. [PMID: 36003935 PMCID: PMC9393526 DOI: 10.3389/fmicb.2022.967845] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 07/20/2022] [Indexed: 11/13/2022] Open
Abstract
Biofilm is made up of microbes and their extracellular matrix, making microorganisms highly tolerant, resistant, and resilient to a wide range of antimicrobials. Biofilm treatment with conventional antimicrobial agents can accelerate the evolution and spread of resistance due to the reduced efficacy and increased gene transfer and differentiation within biofilms. Therefore, effective biofilm-targeting compounds are currently highly sought after. In the present study, we identified elasnin as a potent biofilm-targeting compound against methicillin-resistant Staphylococcus aureus (MRSA). Elasnin effectively inhibited biofilm formation and especially eradicated the pre-formed biofilms of MRSA with low cytotoxicity and low risk of resistance development and retains its activity in a chronic wound biofilms model. A comprehensive mechanistic study using multi-omics and confocal and scanning electron microscopy revealed that elasnin induced the biofilm matrix destruction in a time-dependent manner and interfered with the cell division during the exponential phase, primarily by repressing the expression of virulence factors. Cells released from the elasnin-treated biofilms exhibited a defective appearance and became more sensitive to beta-lactam antibiotic penicillin G. Through gene overexpression and deletion assay, we discovered the key role of sarZ during elasnin-induced biofilm eradication. Overall, the present study identified elasnin as a potent biofilm eradicator against MRSA that harbors potential to be developed for biofilm removal and chronic wound treatment, and provided new insights into the molecular targets for biofilm eradication in MRSA.
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Affiliation(s)
- Lexin Long
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- SZU-HKUST Joint PhD Program in Marine Environmental Science, Shenzhen University, Shenzhen, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Jordy Evan Sulaiman
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Yao Xiao
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Aifang Cheng
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Ruojun Wang
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Jessie James Malit
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Wai Chuen Wong
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Wenchao Liu
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Yong-Xin Li
- Department of Chemistry, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
- The Swire Institute of Marine Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Feng Chen
- Institute for Advanced Study, Shenzhen University, Shenzhen, China
| | - Henry Lam
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
- Henry Lam,
| | - Pei-Yuan Qian
- Department of Ocean Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- *Correspondence: Pei-Yuan Qian,
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Sulaiman JE, Long L, Qian PY, Lam H. Proteome profiling of evolved methicillin-resistant Staphylococcus aureus strains with distinct daptomycin tolerance and resistance phenotypes. Front Microbiol 2022; 13:970146. [PMID: 35992709 PMCID: PMC9386379 DOI: 10.3389/fmicb.2022.970146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 07/13/2022] [Indexed: 12/04/2022] Open
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is a highly dangerous pathogen, and daptomycin has been increasingly used to treat its infections in clinics. Recently, several groups have shown that tolerance and resistance of microbes can evolve rapidly under cyclic antibiotic exposure. We have previously shown that the same tolerance and resistance development occurs in MRSA treated with daptomycin in an adaptive laboratory evolution (ALE) experiment. In the present study, we performed proteomic analysis to compare six daptomycin-tolerant and resistant MRSA strains that were evolved from the same ancestral strain. The strain with a higher tolerance level than the others had the most different proteome and response to antibiotic treatment, resembling those observed in persister cells, which are small subpopulations of bacteria that survive lethal antibiotics treatment. By comparing the proteome changes across strains with similar phenotypes, we identified the key proteins that play important roles in daptomycin tolerance and resistance in MRSA. We selected two candidates to be confirmed by gene overexpression analysis. Overexpression of EcsA1 and FabG, which were up-regulated in all of the tolerant evolved strains, led to increased daptomycin tolerance in wild-type MRSA. The proteomics data also suggested that cell wall modulations were implicated in both resistance and tolerance, but in different ways. While the resistant strains had peptidoglycan changes and a more positive surface charge to directly repel daptomycin, the tolerant strains possessed different cell wall changes that do not involve the peptidoglycan nor alterations of the surface charge. Overall, our study showed the differential proteome profiles among multiple tolerant and resistant strains, pinpointed the key proteins for the two phenotypes and revealed the differences in cell wall modulations between the daptomycin-tolerant/resistant strains.
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Affiliation(s)
- Jordy Evan Sulaiman
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Lexin Long
- Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
| | - Pei-Yuan Qian
- Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
- Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, China
| | - Henry Lam
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China
- *Correspondence: Henry Lam,
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Mutation in the Two-Component System Regulator YycH Leads to Daptomycin Tolerance in Methicillin-Resistant Staphylococcus aureus upon Evolution with a Population Bottleneck. Microbiol Spectr 2022; 10:e0168722. [PMID: 35913149 PMCID: PMC9431245 DOI: 10.1128/spectrum.01687-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adaptive laboratory evolution (ALE) is a useful tool to study the evolution of antibiotic tolerance in bacterial populations under diverse environmental conditions. The role of population bottlenecks in the evolution of tolerance has been investigated in Escherichia coli, but not in a more clinically relevant pathogen, methicillin-resistant Staphylococcus aureus (MRSA). In this study, we used ALE to evolve MRSA under repetitive daptomycin treatment and incorporated population bottlenecks following antibiotic exposure. We observed that the populations finally attained a tolerance mutation in the yycH gene after 2 weeks of evolution with population bottlenecks, and additional mutations in yycI and several other genes further increased the tolerance level. The tolerant populations also became resistant to another glycopeptide antibiotic, vancomycin. Through proteomics, we showed that yycH and yycI mutations led to the loss of function of the proteins and downregulated the WalKR two-component system and the downstream players, including the autolysin Atl and amidase Sle1, which are important for cell wall metabolism. Overall, our study offers new insights into the evolution of daptomycin tolerance under population bottlenecking conditions, which are commonly faced by pathogens during infection; the study also identified new mutations conferring daptomycin tolerance and revealed the proteome alterations in the evolved tolerant populations. IMPORTANCE Although population bottlenecks are known to influence the evolutionary dynamics of microbial populations, how such bottlenecks affect the evolution of tolerance to antibiotics in a clinically relevant methicillin-resistant S. aureus (MRSA) pathogen are still unclear. Here, we performed in vitro evolution of MRSA under cyclic daptomycin treatment and applied population bottlenecks following the treatment. We showed that under these experimental conditions, MRSA populations finally attained mutations in yycH, yycI, and several other genes that led to daptomycin tolerance. The discovered yycH and yycI mutations caused early termination of the genes and loss of function of the proteins, and they subsequently downregulated the expression of proteins controlled by the WalKR two-component system, such as Atl and Sle1. In addition, we compared our proteomics data with multiple studies on distinct daptomycin-tolerant MRSA mutants to identify proteins with a consistent expression pattern that could serve as biological markers for daptomycin tolerance in MRSA.
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Sulaiman JE, Long L, Qian PY, Lam H. Elasnin Effectively Eradicates Daptomycin-Resistant Methicillin-Resistant Staphylococcus aureus Biofilms. Microbiol Spectr 2022; 10:e0232021. [PMID: 35196789 PMCID: PMC8865424 DOI: 10.1128/spectrum.02320-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 01/30/2022] [Indexed: 12/22/2022] Open
Abstract
Elasnin is a recently reported antibiofilm agent that is effective against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA). Remarkably, we observed that elasnin has a superior activity in eradicating daptomycin-resistant MRSA strain biofilm, with a lower minimum biofilm eradication concentration (MBEC) value of 0.625 μg/mL, compared to 2.5 μg/mL for the wild type. Confocal microscopy further confirmed the higher biofilm eradication on the daptomycin-resistant strain, displaying ∼53% decrease in cell density upon elasnin treatment, while the wild-type strain was only decreased by ∼15%. Quantitative proteomics revealed that the daptomycin-resistant strain has a lower expression of the membrane, cell wall, and extracellular proteins, and also proteins involved in the arginine biosynthesis, pathogenesis, and cell adhesion compared to the wild type, which may result in weaker biofilm development. This study highlights the potential clinical application of elasnin through its superior biofilm eradication activity against a daptomycin-resistant MRSA strain, and revealed the associated processes governing this superior activity through proteomics analysis. IMPORTANCE Due to the increased use of daptomycin for the treatment of MRSA infections, the emergence of daptomycin-resistant strains has become prevalent in recent years. In this study, we discovered that elasnin, a newly reported antibiofilm compound, has a superior activity in eradicating daptomycin-resistant MRSA strain biofilms compared to the wild type. Follow-up analysis revealed the reason behind this superior activity, which is the lower expression of key proteins that play a role in pathogenesis and cell adhesion in the daptomycin-resistant strain, leading to weaker biofilm development. This showcases the potential use of elasnin in clinical settings where daptomycin-resistant strains and biofilm formation are prevalent. Altogether, our study provides new insights into the mechanism of elasnin in MRSA biofilm cells and identified its superior biofilm eradicating activity in the daptomycin-resistant strain.
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Affiliation(s)
- Jordy Evan Sulaiman
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, People’s Republic of China
| | - Lexin Long
- Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, People’s Republic of China
| | - Pei-Yuan Qian
- Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, People’s Republic of China
- Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, Guangdong, People’s Republic of China
| | - Henry Lam
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, People’s Republic of China
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Sulaiman JE, Long L, Qian PY, Lam H. Proteomics and Transcriptomics Uncover Key Processes for Elasnin Tolerance in Methicillin-Resistant Staphylococcus aureus. mSystems 2022; 7:e0139321. [PMID: 35076266 PMCID: PMC8788329 DOI: 10.1128/msystems.01393-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 01/03/2022] [Indexed: 01/21/2023] Open
Abstract
Elasnin is a new antibiofilm compound that was recently reported to have excellent activity against methicillin-resistant Staphylococcus aureus (MRSA) biofilms. In this study, we established that elasnin also has antibacterial activity against growing S. aureus planktonic cells. To explore elasnin's potential as an antibiotic, we applied adaptive laboratory evolution (ALE) and produced evolved strains with elevated elasnin tolerance. Interestingly, they were more sensitive toward daptomycin and lysostaphin. Whole-genome sequencing revealed that all of the evolved strains possessed a single point mutation in a putative phosphate transport regulator. Subsequently, they exhibited increased intracellular phosphate (Pi) and polyphosphate levels. Inhibition of the phosphate transport regulator gene changed the phenotype of the wild type to one resembling those observed in the evolved strains. Proteomics and transcriptomics analyses showed that elasnin treatment resulted in the downregulation of many proteins related to cell division and cell wall synthesis, which is important for the survival of growing exponential-phase cells. Other downregulated processes and factors were fatty acid metabolism, glycolysis, the two-component system, RNA degradation, and ribosomal proteins. Most importantly, transport proteins and proteins involved in oxidative phosphorylation and the phosphotransferase system were more upregulated in the evolved strain than in the ancestral strain, indicating that they are important for elasnin tolerance. Overall, this study showed that elasnin has antibacterial activity against growing S. aureus cells and revealed the altered processes due to elasnin treatment and those associated with its tolerance. IMPORTANCE Besides the excellent antibiofilm properties of elasnin, we discovered that it can also kill growing methicillin-resistant Staphylococcus aureus (MRSA) planktonic cells. We subjected MRSA cells to an in vitro evolution experiment, and the resulting evolved strains exhibited increased elasnin tolerance, reduced growth rate, loss of pigmentation, and an increased proportion of small-colony formation, and they became more sensitive toward daptomycin and lysostaphin. Through multiomics analysis, we uncovered the affected processes in growing S. aureus planktonic cells following elasnin treatment, including the downregulation of cell wall synthesis, cell division, and some genes/proteins for the two-component system. These findings suggest that elasnin suppressed processes important for the cells' survival and adaptation to environmental stresses, making it an ideal drug adjuvant candidate. Overall, our study provides new insights into the mechanism of elasnin in S. aureus planktonic cells and pointed out the potential application of elasnin in clinics.
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Affiliation(s)
- Jordy Evan Sulaiman
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, People’s Republic of China
| | - Lexin Long
- Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, People’s Republic of China
| | - Pei-Yuan Qian
- Department of Ocean Science and Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, People’s Republic of China
- Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, Guangdong, People’s Republic of China
| | - Henry Lam
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, People’s Republic of China
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13
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Sulaima JE, Lam H. Proteomics in antibiotic resistance and tolerance research: Mapping the resistome and the tolerome of bacterial pathogens. Proteomics 2022; 22:e2100409. [PMID: 35143120 DOI: 10.1002/pmic.202100409] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/31/2022] [Accepted: 01/31/2022] [Indexed: 11/12/2022]
Abstract
Antibiotic resistance, the ability of a microbial pathogen to evade the effects of antibiotics thereby allowing them to grow under elevated drug concentrations, is an alarming health problem worldwide and has attracted the attention of scientists for decades. On the other hand, the clinical importance of persistence and tolerance as alternative mechanisms for pathogens to survive prolonged lethal antibiotic doses has recently become increasingly appreciated. Persisters and high-tolerance populations are thought to cause the relapse of infectious diseases, and provide opportunities for the pathogens to evolve resistance during the course of antibiotic therapy. Although proteomics and other omics methodology have long been employed to study resistance, its applications in studying persistence and tolerance are still limited. However, due to the growing interest in the topic and recent progress in method developments to study them, there have been some proteomic studies that yield fresh insights into the phenomenon of persistence and tolerance. Combined with the studies on resistance, these collectively guide us to novel molecular targets for the potential drugs for the control of these dangerous pathogens. In this review, we surveyed previous proteomic studies to investigate resistance, persistence, and tolerance mechanisms, and discussed emerging experimental strategies for studying these phenotypes with a combination of adaptive laboratory evolution and high-throughput proteomics. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Jordy Evan Sulaima
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Henry Lam
- Department of Chemical and Biological Engineering, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong
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Novel Daptomycin Tolerance and Resistance Mutations in Methicillin-Resistant Staphylococcus aureus from Adaptive Laboratory Evolution. mSphere 2021; 6:e0069221. [PMID: 34585959 PMCID: PMC8550074 DOI: 10.1128/msphere.00692-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
It has been shown recently in a number of in vitro laboratory evolution experiments that under repetitive antibiotic exposure, bacterial populations can adapt quickly to the treatment condition by becoming tolerant and/or resistant to the drug. The repeated killing and regrowth cycles hasten the selection for tolerant/resistant mutants with survival advantages. Due to the random nature of mutagenesis and the large target size of tolerance mutations, this dynamic evolutionary process appears to be highly unpredictable, generating distinct mutants even under identical, well-controlled laboratory conditions. Here, we utilized an adaptive laboratory evolution (ALE) experiment to hunt for novel tolerance and resistance mutations by subjecting multiple lineages of methicillin-resistant Staphylococcus aureus (MRSA) to repetitive daptomycin treatment. By sequencing multiple isolates along the course of evolution, we obtained three tolerant mutants that have different tolerance levels and identified novel daptomycin resistance mutations in the mprF gene. In addition, we found that tolerance/resistance development is more rapid if the population is treated in the exponential phase than if it is treated in the stationary phase, which is likely attributable to the more effective killing of growing cells by the antibiotic. Through competition assays, we found that whether or not the resistant mutants can take over the population heavily depends on the relative survival advantages conferred by the tolerance and resistance mutations. This study reports novel daptomycin resistance and tolerance mutations and offers new insights into the dynamics of the development of tolerance and resistance in bacterial populations under antibiotic exposure. IMPORTANCE Although the phenotype of increased tolerance and/or resistance was commonly observed in evolved populations from typical adaptive laboratory evolution (ALE) experiments, a wide variety of mutations that underlie those phenotypes have been discovered. Therefore, performing ALE experiments in multiple populations in parallel would serve the purpose of mining for different tolerant/resistant mutants and would be useful to explore the diverse population dynamics of evolution. In this study, we performed in vitro evolution in a clinically relevant methicillin-resistant Staphylococcus aureus (MRSA) pathogen, using a lethal concentration of a drug that is frequently used in the clinic, daptomycin. Using this strategy, we obtained three distinct daptomycin-tolerant mutants and identified six daptomycin resistance mutations in different locations on the mprF gene, collectively adding to our current knowledge of this important pathogen. In addition, we found out that in most cases, the daptomycin-resistant mutant outcompetes other susceptible and tolerant mutants and becomes established in the final population. Follow-up competition experiments offered an explanation; the resistant mutant cannot invade populations of tolerant mutants that confer higher survival advantages than itself. In summary, we demonstrated an experimental strategy to explore the landscape and dynamics of the evolution of tolerance and resistance in MRSA toward daptomycin and made observations that will guide future ALE experiments.
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