1
|
Shepherd MJ, Fu T, Harrington NE, Kottara A, Cagney K, Chalmers JD, Paterson S, Fothergill JL, Brockhurst MA. Ecological and evolutionary mechanisms driving within-patient emergence of antimicrobial resistance. Nat Rev Microbiol 2024:10.1038/s41579-024-01041-1. [PMID: 38689039 DOI: 10.1038/s41579-024-01041-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/13/2024] [Indexed: 05/02/2024]
Abstract
The ecological and evolutionary mechanisms of antimicrobial resistance (AMR) emergence within patients and how these vary across bacterial infections are poorly understood. Increasingly widespread use of pathogen genome sequencing in the clinic enables a deeper understanding of these processes. In this Review, we explore the clinical evidence to support four major mechanisms of within-patient AMR emergence in bacteria: spontaneous resistance mutations; in situ horizontal gene transfer of resistance genes; selection of pre-existing resistance; and immigration of resistant lineages. Within-patient AMR emergence occurs across a wide range of host niches and bacterial species, but the importance of each mechanism varies between bacterial species and infection sites within the body. We identify potential drivers of such differences and discuss how ecological and evolutionary analysis could be embedded within clinical trials of antimicrobials, which are powerful but underused tools for understanding why these mechanisms vary between pathogens, infections and individuals. Ultimately, improving understanding of how host niche, bacterial species and antibiotic mode of action combine to govern the ecological and evolutionary mechanism of AMR emergence in patients will enable more predictive and personalized diagnosis and antimicrobial therapies.
Collapse
Affiliation(s)
- Matthew J Shepherd
- Division of Evolution and Genomic Sciences, School of Biological Sciences, University of Manchester, Manchester, UK.
| | - Taoran Fu
- Division of Evolution and Genomic Sciences, School of Biological Sciences, University of Manchester, Manchester, UK
| | - Niamh E Harrington
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Anastasia Kottara
- Division of Evolution and Genomic Sciences, School of Biological Sciences, University of Manchester, Manchester, UK
| | - Kendall Cagney
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
| | - James D Chalmers
- Division of Molecular and Clinical Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - Steve Paterson
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Joanne L Fothergill
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Michael A Brockhurst
- Division of Evolution and Genomic Sciences, School of Biological Sciences, University of Manchester, Manchester, UK.
| |
Collapse
|
2
|
Hachani A, Giulieri SG, Guérillot R, Walsh CJ, Herisse M, Soe YM, Baines SL, Thomas DR, Cheung SD, Hayes AS, Cho E, Newton HJ, Pidot S, Massey RC, Howden BP, Stinear TP. A high-throughput cytotoxicity screening platform reveals agr-independent mutations in bacteraemia-associated Staphylococcus aureus that promote intracellular persistence. eLife 2023; 12:84778. [PMID: 37289634 DOI: 10.7554/elife.84778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 05/23/2023] [Indexed: 06/10/2023] Open
Abstract
Staphylococcus aureus infections are associated with high mortality rates. Often considered an extracellular pathogen, S. aureus can persist and replicate within host cells, evading immune responses, and causing host cell death. Classical methods for assessing S. aureus cytotoxicity are limited by testing culture supernatants and endpoint measurements that do not capture the phenotypic diversity of intracellular bacteria. Using a well-established epithelial cell line model, we have developed a platform called InToxSa (intracellular toxicity of S. aureus) to quantify intracellular cytotoxic S. aureus phenotypes. Studying a panel of 387 S. aureus bacteraemia isolates, and combined with comparative, statistical, and functional genomics, our platform identified mutations in S. aureus clinical isolates that reduced bacterial cytotoxicity and promoted intracellular persistence. In addition to numerous convergent mutations in the Agr quorum sensing system, our approach detected mutations in other loci that also impacted cytotoxicity and intracellular persistence. We discovered that clinical mutations in ausA, encoding the aureusimine non-ribosomal peptide synthetase, reduced S. aureus cytotoxicity, and increased intracellular persistence. InToxSa is a versatile, high-throughput cell-based phenomics platform and we showcase its utility by identifying clinically relevant S. aureus pathoadaptive mutations that promote intracellular residency.
Collapse
Affiliation(s)
- Abderrahman Hachani
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Stefano G Giulieri
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Romain Guérillot
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Calum J Walsh
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Marion Herisse
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Ye Mon Soe
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Sarah L Baines
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - David R Thomas
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
- Infection and Immunity Program, Department of Microbiology and Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Shane Doris Cheung
- Biological Optical Microscopy Platform, University of Melbourne, Melbourne, Australia
| | - Ashleigh S Hayes
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Ellie Cho
- Biological Optical Microscopy Platform, University of Melbourne, Melbourne, Australia
| | - Hayley J Newton
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
- Infection and Immunity Program, Department of Microbiology and Biomedicine Discovery Institute, Monash University, Clayton, Australia
| | - Sacha Pidot
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Ruth C Massey
- School of Microbiology, University College Cork, Cork, Ireland
- School of Medicine, University College Cork, Cork, Ireland
- APC Microbiome Ireland, University College Cork, Cork, Ireland
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom
| | - Benjamin P Howden
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
- Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| | - Timothy P Stinear
- Department of Microbiology and Immunology, Doherty Institute, University of Melbourne, Melbourne, Australia
| |
Collapse
|
3
|
Antibiotics Limit Adaptation of Drug-Resistant Staphylococcus aureus to Hypoxia. Antimicrob Agents Chemother 2022; 66:e0092622. [PMID: 36409116 PMCID: PMC9765076 DOI: 10.1128/aac.00926-22] [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] [Indexed: 11/23/2022] Open
Abstract
Bacterial pathogens are confronted with a range of challenges at the site of infection, including exposure to antibiotic treatment and harsh physiological conditions, that can alter the fitness benefits and costs of acquiring antibiotic resistance. Here, we develop an experimental system to recapitulate resistance gene acquisition by Staphylococcus aureus and test how the subsequent evolution of the resistant bacterium is modulated by antibiotic treatment and oxygen levels, both of which are known to vary extensively at sites of infection. We show that acquiring tetracycline resistance was costly, reducing competitive growth against the isogenic strain without the resistance gene in the absence of the antibiotic, for S. aureus under hypoxic but not normoxic conditions. Treatment with tetracycline or doxycycline drove the emergence of enhanced resistance through mutations in an RluD-like protein-encoding gene and duplications of tetL, encoding the acquired tetracycline-specific efflux pump. In contrast, evolutionary adaptation by S. aureus to hypoxic conditions, which evolved in the absence of antibiotics through mutations affecting gyrB, was impeded by antibiotic treatment. Together, these data suggest that the horizontal acquisition of a new resistance mechanism is merely a starting point for the emergence of high-level resistance under antibiotic selection but that antibiotic treatment constrains pathogen adaptation to other important environmental selective forces such as hypoxia, which in turn could limit the survival of these highly resistant but poorly adapted genotypes after antibiotic treatment is ended.
Collapse
|
4
|
Giulieri SG, Guérillot R, Duchene S, Hachani A, Daniel D, Seemann T, Davis JS, Tong SYC, Young BC, Wilson DJ, Stinear TP, Howden BP. Niche-specific genome degradation and convergent evolution shaping Staphylococcus aureus adaptation during severe infections. eLife 2022; 11:77195. [PMID: 35699423 PMCID: PMC9270034 DOI: 10.7554/elife.77195] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 06/08/2022] [Indexed: 11/13/2022] Open
Abstract
During severe infections, Staphylococcus aureus moves from its colonising sites to blood and tissues and is exposed to new selective pressures, thus, potentially driving adaptive evolution. Previous studies have shown the key role of the agr locus in S. aureus pathoadaptation; however, a more comprehensive characterisation of genetic signatures of bacterial adaptation may enable prediction of clinical outcomes and reveal new targets for treatment and prevention of these infections. Here, we measured adaptation using within-host evolution analysis of 2590 S. aureus genomes from 396 independent episodes of infection. By capturing a comprehensive repertoire of single nucleotide and structural genome variations, we found evidence of a distinctive evolutionary pattern within the infecting populations compared to colonising bacteria. These invasive strains had up to 20-fold enrichments for genome degradation signatures and displayed significantly convergent mutations in a distinctive set of genes, linked to antibiotic response and pathogenesis. In addition to agr-mediated adaptation, we identified non-canonical, genome-wide significant loci including sucA-sucB and stp1. The prevalence of adaptive changes increased with infection extent, emphasising the clinical significance of these signatures. These findings provide a high-resolution picture of the molecular changes when S. aureus transitions from colonisation to severe infection and may inform correlation of infection outcomes with adaptation signatures. The bacterium Staphylococcus aureus lives harmlessly on our skin and noses. However, occasionally, it gets into our blood and internal organs, such as our bones and joints, where it causes severe, long-lasting infections that are difficult to treat. Over time, S. aureus acquire characteristics that help them to adapt to different locations, such as transitioning from the nose to the blood, and avoid being killed by antibiotics. Previous studies have identified changes, or ‘mutations’, in genes that are likely to play an important role in this evolutionary process. One of these genes, called accessory gene regulator (or agr for short), has been shown to control the mechanisms S. aureus use to infect cells and disseminate in the body. However, it is unclear if there are changes in other genes that also help S. aureus adapt to life inside the human body. To help resolve this mystery, Giulieri et al. collected 2,500 samples of S. aureus from almost 400 people. This included bacteria harmlessly living on the skin or in the nose, as well as strains that caused an infection. Gene sequencing revealed a small number of genes, referred to as ‘adaptive genes’, that often acquire mutations during infection. Of these, agr was the most commonly altered. However, mutations in less well-known genes were also identified: some of these genes are related to resistance to antibiotics, while others are involved in chemical processes that help the bacteria to process nutrients. Most mutations were caused by random errors being introduced in to the bacteria’s genetic code which stopped genes from working. However, in some cases, genes were turned off by small fragments of DNA moving around and inserting themselves into different parts of the genome. This study highlights a group of genes that help S. aureus to thrive inside the body and cause severe and prolonged infections. If these results can be confirmed, it may help to guide which antibiotics are used to treat different infections. Furthermore, understanding which genes are important for infection could lead to new strategies for eliminating this dangerous bacterium.
Collapse
Affiliation(s)
- Stefano G Giulieri
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia
| | - Romain Guérillot
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Sebastian Duchene
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Abderrahman Hachani
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Diane Daniel
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Torsten Seemann
- Microbiological Diagnostic Unit, University of Melbourne, Melbourne, Australia
| | - Joshua S Davis
- Department of Infectious Diseases, John Hunter Hospital, Newcastle, Australia
| | - Steven Y C Tong
- Victorian Infectious Diseases Service, University of Melbourne, Melbourne, Australia
| | | | | | - Timothy P Stinear
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Benjamin P Howden
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| |
Collapse
|
5
|
Wong Fok Lung T, Chan LC, Prince A, Yeaman MR, Archer NK, Aman MJ, Proctor RA. Staphylococcus aureus adaptive evolution: Recent insights on how immune evasion, immunometabolic subversion and host genetics impact vaccine development. Front Cell Infect Microbiol 2022; 12:1060810. [PMID: 36636720 PMCID: PMC9831658 DOI: 10.3389/fcimb.2022.1060810] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 11/16/2022] [Indexed: 12/28/2022] Open
Abstract
Despite meritorious attempts, a S. aureus vaccine that prevents infection or mitigates severity has not yet achieved efficacy endpoints in prospective, randomized clinical trials. This experience underscores the complexity of host-S. aureus interactions, which appear to be greater than many other bacterial pathogens against which successful vaccines have been developed. It is increasingly evident that S. aureus employs strategic countermeasures to evade or exploit human immune responses. From entering host cells to persist in stealthy intracellular reservoirs, to sensing the environmental milieu and leveraging bacterial or host metabolic products to reprogram host immune responses, S. aureus poses considerable challenges for the development of effective vaccines. The fact that this pathogen causes distinct types of infections and can undergo transient genetic, transcriptional or metabolic adaptations in vivo that do not occur in vitro compounds challenges in vaccine development. Notably, the metabolic versatility of both bacterial and host immune cells as they compete for available substrates within specific tissues inevitably impacts the variable repertoire of gene products that may or may not be vaccine antigens. In this respect, S. aureus has chameleon phenotypes that have alluded vaccine strategies thus far. Nonetheless, a number of recent studies have also revealed important new insights into pathogenesis vulnerabilities of S. aureus. A more detailed understanding of host protective immune defenses versus S. aureus adaptive immune evasion mechanisms may offer breakthroughs in the development of effective vaccines, but at present this goal remains a very high bar. Coupled with the recent advances in human genetics and epigenetics, newer vaccine technologies may enable such a goal. If so, future vaccines that protect against or mitigate the severity of S. aureus infections are likely to emerge at the intersection of precision and personalized medicine. For now, the development of S. aureus vaccines or alternative therapies that reduce mortality and morbidity must continue to be pursued.
Collapse
Affiliation(s)
| | - Liana C Chan
- Department of Medicine, David Geffen School of Medicine at University of California Loss Angeles (UCLA), Los Angeles, CA, United States.,Divisions of Molecular Medicine and Infectious Diseases, Harbor-University of California Loss Angeles (UCLA) Medical Center, Torrance, CA, United States.,Lundquist Institute for Biomedical Innovation at Harbor-University of California Loss Angeles (UCLA) Medical Center, Torrance, CA, United States
| | - Alice Prince
- Department of Pediatrics, Columbia University, New York, NY, United States
| | - Michael R Yeaman
- Department of Medicine, David Geffen School of Medicine at University of California Loss Angeles (UCLA), Los Angeles, CA, United States.,Divisions of Molecular Medicine and Infectious Diseases, Harbor-University of California Loss Angeles (UCLA) Medical Center, Torrance, CA, United States.,Lundquist Institute for Biomedical Innovation at Harbor-University of California Loss Angeles (UCLA) Medical Center, Torrance, CA, United States
| | - Nathan K Archer
- Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - M Javad Aman
- Integrated BioTherapeutics, Rockville, MD, United States
| | - Richard A Proctor
- Department of Medicine and Medical Microbiology/Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
| |
Collapse
|
6
|
Gatt YE, Margalit H. Common Adaptive Strategies Underlie Within-Host Evolution of Bacterial Pathogens. Mol Biol Evol 2021; 38:1101-1121. [PMID: 33118035 PMCID: PMC7947768 DOI: 10.1093/molbev/msaa278] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Within-host adaptation is a hallmark of chronic bacterial infections, involving substantial genomic changes. Recent large-scale genomic data from prolonged infections allow the examination of adaptive strategies employed by different pathogens and open the door to investigate whether they converge toward similar strategies. Here, we compiled extensive data of whole-genome sequences of bacterial isolates belonging to miscellaneous species sampled at sequential time points during clinical infections. Analysis of these data revealed that different species share some common adaptive strategies, achieved by mutating various genes. Although the same genes were often mutated in several strains within a species, different genes related to the same pathway, structure, or function were changed in other species utilizing the same adaptive strategy (e.g., mutating flagellar genes). Strategies exploited by various bacterial species were often predicted to be driven by the host immune system, a powerful selective pressure that is not species specific. Remarkably, we find adaptive strategies identified previously within single species to be ubiquitous. Two striking examples are shifts from siderophore-based to heme-based iron scavenging (previously shown for Pseudomonas aeruginosa) and changes in glycerol-phosphate metabolism (previously shown to decrease sensitivity to antibiotics in Mycobacterium tuberculosis). Virulence factors were often adaptively affected in different species, indicating shifts from acute to chronic virulence and virulence attenuation during infection. Our study presents a global view on common within-host adaptive strategies employed by different bacterial species and provides a rich resource for further studying these processes.
Collapse
Affiliation(s)
- Yair E Gatt
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Hanah Margalit
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| |
Collapse
|
7
|
Soe YM, Bedoui S, Stinear TP, Hachani A. Intracellular Staphylococcus aureus and host cell death pathways. Cell Microbiol 2021; 23:e13317. [PMID: 33550697 DOI: 10.1111/cmi.13317] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 01/22/2021] [Accepted: 01/23/2021] [Indexed: 12/13/2022]
Abstract
Staphylococcus aureus is a major opportunistic human pathogen that is globally prevalent. Although S. aureus and humans may have co-evolved to the point of commensalism, the bacterium is equipped with virulence factors causing devastating infections. The adoption of an intracellular lifestyle by S. aureus is an important facet of its pathogenesis. Occupying a privileged intracellular compartment permits evasion from the bactericidal actions of host immunity and antibiotics. However, this localization exposes S. aureus to cell-intrinsic processes comprising autophagy, metabolic challenges and clearance mechanisms orchestrated by host programmed cell death pathways (PCDs), including apoptosis, pyroptosis and necroptosis. Mounting evidence suggests that S. aureus deploys pathoadaptive mechanisms that modulate the expression of its virulence factors to prevent elimination through PCD pathways. In this review, we critically analyse the current literature on the interplay between S. aureus virulence factors with the key, intertwined nodes of PCD. We discuss how S. aureus adaptation to the human host plays an essential role in the evasion of PCD, and we consider future directions to study S. aureus-PCD interactions.
Collapse
Affiliation(s)
- Ye Mon Soe
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Sammy Bedoui
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Timothy P Stinear
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Abderrahman Hachani
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| |
Collapse
|
8
|
Comprehensive Genomic Investigation of Adaptive Mutations Driving the Low-Level Oxacillin Resistance Phenotype in Staphylococcus aureus. mBio 2020; 11:mBio.02882-20. [PMID: 33293382 PMCID: PMC7733948 DOI: 10.1128/mbio.02882-20] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Antistaphylococcal penicillins such as oxacillin are the key antibiotics in the treatment of invasive methicillin-susceptible Staphylococcus aureus (MSSA) infections; however, mec gene-independent resistance adaptation can cause treatment failure. Despite its clinical relevance, the basis of this phenomenon remains poorly understood. Here, we investigated the genomic adaptation to oxacillin at an unprecedented scale using a large collection of 503 clinical mec-negative isolates and 30 in vitro-adapted isolates from independent oxacillin exposures. By combining comparative genomics, evolutionary convergence, and genome-wide association analysis, we found 21 genetic loci associated with low-level oxacillin resistance, underscoring the polygenic nature of this phenotype. Evidence of adaptation was particularly strong for the c-di-AMP signal transduction pathways (gdpP and dacA) and in the clpXP chaperone-protease complex. The role of mutations in gdpP in conferring low-level oxacillin resistance was confirmed by allele-swapping experiments. We found that resistance to oxacillin emerges at high frequency in vitro (median, 2.9 × 10-6; interquartile range [IQR], 1.9 × 10-6 to 3.9 × 10-6), which is consistent with a recurrent minimum inhibitory concentration (MIC) increase across the global phylogeny of clinical isolates. Nevertheless, adaptation in clinical isolates appears sporadically, with no stably adapted lineages, suggesting a high fitness cost of resistance, confirmed by growth assessment of mutants in rich media. Our data provide a broader understanding of the emergence and dynamics of oxacillin resistance adaptation in S. aureus and a framework for future surveillance of this clinically important phenomenon.IMPORTANCE The majority of Staphylococcus aureus strains causing human disease are methicillin-susceptible (MSSA) and can be treated with antistaphylococcal penicillins (such as oxacillin). While acquisition of the mec gene represents the main resistance mechanism to oxacillin, S. aureus can acquire low-level resistance through adaptive mutations in other genes. In this study, we used genomic approaches to understand the basis of S. aureus adaption to oxacillin and its dynamic at the population level. By combining a genome analysis of clinical isolates from persistent MSSA infections, in vitro selection of oxacillin resistance, and genome-wide association analysis on a large collection of isolates, we identified 21 genes linked to secondary oxacillin resistance. Adaptive mutations in these genes were easy to select when S. aureus was exposed to oxacillin, but they also came at a substantial cost in terms of bacterial fitness, suggesting that this phenotype emerges preferentially in the setting of sustained antibiotic exposure.
Collapse
|
9
|
Tuchscherr L, Löffler B, Proctor RA. Persistence of Staphylococcus aureus: Multiple Metabolic Pathways Impact the Expression of Virulence Factors in Small-Colony Variants (SCVs). Front Microbiol 2020; 11:1028. [PMID: 32508801 PMCID: PMC7253646 DOI: 10.3389/fmicb.2020.01028] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 04/27/2020] [Indexed: 12/30/2022] Open
Abstract
Staphylococcus aureus is able to survive within host cells by switching its phenotype to the small-colony variant (SCV) phenotype. The emergence of SCVs is associated with the development of persistent infections, which may be both chronic and recurrent. This slow-growing subpopulation of S. aureus forms small colonies on solid-medium agar, is induced within host cells, presents a non-homogenous genetic background, has reduced expression of virulence factors and presents a variable phenotype (stable or unstable). While virtually all SCVs isolated from clinical specimens can revert to the parental state with rapid growth, the stable SCVs recovered in clinical specimens have been found to contain specific mutations in metabolic pathways. In contrast, other non-stable SCVs are originated from regulatory mechanisms involving global regulators (e.g., sigB, sarA, and agr) or other non-defined mutations. One major characteristic of SCVs was the observation that SCVs were recovered from five patients with infections that could persist for decades. In these five cases, the SCVs had defects in electron transport. This linked persistent infections with SCVs. The term "persistent infection" is a clinical term wherein bacteria remain in the host for prolonged periods of time, sometimes with recurrent infection, despite apparently active antibiotics. These terms were described in vitro where bacteria remain viable in liquid culture medium in the presence of antibiotics. These bacteria are called "persisters". While SCVs can be persisters in liquid culture, not all persisters are SCVs. One mechanism associated with the metabolically variant SCVs is the reduced production of virulence factors. SCVs have consistently shown reduced levels of RNAIII, a product of the accessory gene regulatory (agrBDCA) locus that controls a quorum-sensing system and regulates the expression of a large number of virulence genes. Reduced Agr acitivity is associated with enhanced survival of SCVs within host cells. In this review, we examine the impact of the SCVs with altered metabolic pathways on agr, and we draw distinctions with other types of SCVs that emerge within mammalian cells with prolonged infection.
Collapse
Affiliation(s)
- Lorena Tuchscherr
- Institute of Medical Microbiology, Jena University Hospital, Jena, Germany.,Center for Sepsis Control and Care, Jena University Hospital, Jena, Germany
| | - Bettina Löffler
- Institute of Medical Microbiology, Jena University Hospital, Jena, Germany.,Center for Sepsis Control and Care, Jena University Hospital, Jena, Germany
| | - Richard A Proctor
- Departments of Medical Microbiology/Immunology and Medicine, University of Wisconsin Medical School, Madison, WI, United States
| |
Collapse
|
10
|
Unstable chromosome rearrangements in Staphylococcus aureus cause phenotype switching associated with persistent infections. Proc Natl Acad Sci U S A 2019; 116:20135-20140. [PMID: 31527262 PMCID: PMC6778178 DOI: 10.1073/pnas.1904861116] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Staphylococcus aureus is a major human pathogen known to exhibit subpopulations of small-colony variants (SCVs) that cause persistent or recurrent infections. The underlying mechanisms promoting the SCV phenotypic switching and adaptation to persistent infection are poorly understood. Moreover, the instability of this frequently reverting phenotype hampers diagnosis and study. Here we show that SCVs with reduced virulence but increased immune evasion and persistence properties can arise from reversible chromosomal instability. This mechanism of SCV generation implies an asymmetric chromosome inversion and the activation of prophage-encoding genes used for immune evasion. Assessment of major S. aureus lineages indicates this genomic plasticity is a common but previously unrecognized mechanism used by S. aureus to cause persistent and relapsing infections. Staphylococcus aureus small-colony variants (SCVs) are associated with unusually chronic and persistent infections despite active antibiotic treatment. The molecular basis for this clinically important phenomenon is poorly understood, hampered by the instability of the SCV phenotype. Here we investigated the genetic basis for an unstable S. aureus SCV that arose spontaneously while studying rifampicin resistance. This SCV showed no nucleotide differences across its genome compared with a normal-colony variant (NCV) revertant, yet the SCV presented the hallmarks of S. aureus linked to persistent infection: down-regulation of virulence genes and reduced hemolysis and neutrophil chemotaxis, while exhibiting increased survival in blood and ability to invade host cells. Further genome analysis revealed chromosome structural variation uniquely associated with the SCV. These variations included an asymmetric inversion across half of the S. aureus chromosome via recombination between type I restriction modification system (T1RMS) genes, and the activation of a conserved prophage harboring the immune evasion cluster (IEC). Phenotypic reversion to the wild-type–like NCV state correlated with reversal of the chromosomal inversion (CI) and with prophage stabilization. Further analysis of 29 complete S. aureus genomes showed strong signatures of recombination between hsdMS genes, suggesting that analogous CI has repeatedly occurred during S. aureus evolution. Using qPCR and long-read amplicon deep sequencing, we detected subpopulations with T1RMS rearrangements causing CIs and prophage activation across major S. aureus lineages. Here, we have discovered a previously unrecognized and widespread mechanism of reversible genomic instability in S. aureus associated with SCV generation and persistent infections.
Collapse
|
11
|
Giulieri SG, Baines SL, Guerillot R, Seemann T, Gonçalves da Silva A, Schultz M, Massey RC, Holmes NE, Stinear TP, Howden BP. Genomic exploration of sequential clinical isolates reveals a distinctive molecular signature of persistent Staphylococcus aureus bacteraemia. Genome Med 2018; 10:65. [PMID: 30103826 PMCID: PMC6090636 DOI: 10.1186/s13073-018-0574-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 07/27/2018] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Large-scale genomic studies of within-host diversity in Staphylococcus aureus bacteraemia (SAB) are needed to understanding bacterial adaptation underlying persistence and thus refining the role of genomics in management of SAB. However, available comparative genomic studies of sequential SAB isolates have tended to focus on selected cases of unusually prolonged bacteraemia, where secondary antimicrobial resistance has developed. METHODS To understand bacterial genetic diversity during SAB more broadly, we applied whole genome sequencing to a large collection of sequential isolates obtained from patients with persistent or relapsing bacteraemia. After excluding genetically unrelated isolates, we performed an in-depth genomic analysis of point mutations and chromosome structural variants arising within individual SAB episodes. RESULTS We show that, while adaptation pathways are heterogenous and episode-specific, isolates from persistent bacteraemia have a distinctive molecular signature, characterised by a low mutation frequency and high proportion of non-silent mutations. Analysis of structural genomic variants revealed that these often overlooked genetic events are commonly acquired during SAB. We discovered that IS256 insertion may represent the most effective driver of within-host microevolution in selected lineages, with up to three new insertion events per isolate even in the absence of other mutations. Genetic mechanisms resulting in significant phenotypic changes, such as increases in vancomycin resistance, development of small colony phenotypes, and decreases in cytotoxicity, included mutations in key genes (rpoB, stp, agrA) and an IS256 insertion upstream of the walKR operon. CONCLUSIONS This study provides for the first time a large-scale analysis of within-host genomic changes during invasive S. aureus infection and describes specific patterns of adaptation that will be informative for both understanding S. aureus pathoadaptation and utilising genomics for management of complicated S. aureus infections.
Collapse
Affiliation(s)
- Stefano G Giulieri
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection & Immunity, Melbourne, Australia.,Infectious Disease Department, Austin Health, Melbourne, Australia.,Infectious Diseases Service, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland
| | - Sarah L Baines
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection & Immunity, Melbourne, Australia
| | - Romain Guerillot
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection & Immunity, Melbourne, Australia
| | - Torsten Seemann
- Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne at The Doherty Institute of Infection and Immunity, Melbourne, Australia.,Melbourne Bioinformatics, The University of Melbourne, Melbourne, Australia
| | - Anders Gonçalves da Silva
- Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne at The Doherty Institute of Infection and Immunity, Melbourne, Australia
| | - Mark Schultz
- Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne at The Doherty Institute of Infection and Immunity, Melbourne, Australia
| | - Ruth C Massey
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Natasha E Holmes
- Infectious Disease Department, Austin Health, Melbourne, Australia
| | - Timothy P Stinear
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection & Immunity, Melbourne, Australia
| | - Benjamin P Howden
- Department of Microbiology and Immunology, The University of Melbourne at the Doherty Institute for Infection & Immunity, Melbourne, Australia. .,Infectious Disease Department, Austin Health, Melbourne, Australia. .,Microbiological Diagnostic Unit Public Health Laboratory, The University of Melbourne at The Doherty Institute of Infection and Immunity, Melbourne, Australia.
| |
Collapse
|
12
|
Tandem Amplification of the Staphylococcal Cassette Chromosome mec Element Can Drive High-Level Methicillin Resistance in Methicillin-Resistant Staphylococcus aureus. Antimicrob Agents Chemother 2017; 61:AAC.00869-17. [PMID: 28717043 DOI: 10.1128/aac.00869-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 07/08/2017] [Indexed: 11/20/2022] Open
Abstract
Hospital-associated methicillin-resistant Staphylococcus aureus (MRSA) strains typically express high-level, homogeneous (HoR) β-lactam resistance, whereas community-associated MRSA (CA-MRSA) more commonly express low-level heterogeneous (HeR) resistance. Expression of the HoR phenotype typically requires both increased expression of the mecA gene, carried on the staphylococcal cassette chromosome mec element (SCCmec), and additional mutational event(s) elsewhere on the chromosome. Here the oxacillin concentration in a chemostat culture of the CA-MRSA strain USA300 was increased from 8 μg/ml to 130 μg/ml over 13 days to isolate highly oxacillin-resistant derivatives. A stable, small-colony variant, designated HoR34, which had become established in the chemostat culture was found to have acquired mutations in gdpP, clpX, guaA, and camS Closer inspection of the genome sequence data further revealed that reads covering SCCmec were ∼10 times overrepresented compared to other parts of the chromosome. Quantitative PCR (qPCR) confirmed >10-fold-higher levels of mecA DNA on the HoR34 chromosome, and MinION genome sequencing verified the presence of 10 tandem repeats of the SCCmec element. qPCR further demonstrated that subculture of HoR34 in various concentrations of oxacillin (0 to 100 μg/ml) was accompanied by accordion-like contraction and amplification of the SCCmec element. Although slower growing than strain USA300, HoR34 outcompeted the parent strain in the presence of subinhibitory oxacillin. These data identify tandem amplification of the SCCmec element as a new mechanism of high-level methicillin resistance in MRSA, which may provide a competitive advantage for MRSA under antibiotic selection.
Collapse
|
13
|
Lee JYH, Monk IR, Pidot SJ, Singh S, Chua KYL, Seemann T, Stinear TP, Howden BP. Functional analysis of the first complete genome sequence of a multidrug resistant sequence type 2 Staphylococcus epidermidis. Microb Genom 2016; 2:e000077. [PMID: 28785416 PMCID: PMC5537629 DOI: 10.1099/mgen.0.000077] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 07/05/2016] [Indexed: 12/31/2022] Open
Abstract
Staphylococcus epidermidis is a significant opportunistic pathogen of humans. The ST2 lineage is frequently multidrug-resistant and accounts for most of the clinical disease worldwide. However, there are no publically available, closed ST2 genomes and pathogenesis studies have not focused on these strains. We report the complete genome and methylome of BPH0662, a multidrug-resistant, hospital-adapted, ST2 S. epidermidis, and describe the correlation between resistome and phenotype, as well as demonstrate its relationship to publically available, international ST2 isolates. Furthermore, we delineate the methylome determined by the two type I restriction modification systems present in BPH0662 through heterologous expression in Escherichia coli, allowing the assignment of each system to its corresponding target recognition motif. As the first, to our knowledge, complete ST2 S. epidermidis genome, BPH0662 provides a valuable reference for future genomic studies of this clinically relevant lineage. Defining the methylome and the construction of these E. coli hosts provides the foundation for the development of molecular tools to bypass restriction modification systems in this lineage that has hitherto proven intractable.
Collapse
Affiliation(s)
- Jean Y. H. Lee
- Department of Microbiology & Immunology at The Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, Australia
| | - Ian R. Monk
- Department of Microbiology & Immunology at The Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, Australia
| | - Sacha J. Pidot
- Department of Microbiology & Immunology at The Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, Australia
| | | | - Kyra Y. L. Chua
- Microbiology Department, Austin Health, Melbourne, Australia
| | - Torsten Seemann
- Doherty Applied Microbial Genomics, Department of Microbiology & Immunology at The Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, Australia
- Victorian Life Sciences Computation Inititative, University of Melbourne, Melbourne, Victoria, Australia
| | - Timothy P. Stinear
- Department of Microbiology & Immunology at The Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, Australia
- Doherty Applied Microbial Genomics, Department of Microbiology & Immunology at The Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, Australia
| | - Benjamin P. Howden
- Doherty Applied Microbial Genomics, Department of Microbiology & Immunology at The Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, Australia
- Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology & Immunology at The Doherty Institute for Infection & Immunity, University of Melbourne, Melbourne, Australia
- Infectious Diseases Department, Austin Health, Melbourne, Australia
| |
Collapse
|
14
|
Heilbronner S, Monk IR, Brozyna JR, Heinrichs DE, Skaar EP, Peschel A, Foster TJ. Competing for Iron: Duplication and Amplification of the isd Locus in Staphylococcus lugdunensis HKU09-01 Provides a Competitive Advantage to Overcome Nutritional Limitation. PLoS Genet 2016; 12:e1006246. [PMID: 27575058 PMCID: PMC5004866 DOI: 10.1371/journal.pgen.1006246] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 07/15/2016] [Indexed: 01/10/2023] Open
Abstract
Staphylococcus lugdunensis is a coagulase negative bacterial pathogen that is particularly associated with severe cases of infectious endocarditis. Unique amongst the coagulase-negative staphylococci, S. lugdunensis harbors an iron regulated surface determinant locus (isd). This locus facilitates the acquisition of heme as a source of nutrient iron during infection and allows iron limitation caused by “nutritional immunity” to be overcome. The isd locus is duplicated in S. lugdunensis HKU09-01 and we show here that the duplication is intrinsically unstable and undergoes accordion-like amplification and segregation leading to extensive isd copy number variation. Amplification of the locus increased the level of expression of Isd proteins and improved binding of hemoglobin to the cell surface of S. lugdunensis. Furthermore, Isd overexpression provided an advantage when strains were competing for a limited amount of hemoglobin as the sole source of iron. Gene duplications and amplifications (GDA) are events of fundamental importance for bacterial evolution and are frequently associated with antibiotic resistance in many species. As such, GDAs are regarded as evolutionary adaptions to novel selective pressures in hostile environments pointing towards a special importance of isd for S. lugdunensis. For the first time we show an example of a GDA that involves a virulence factor of a Gram-positive pathogen and link the GDA directly to a competitive advantage when the bacteria were struggling with selective pressures mimicking “nutritional immunity”. Sometimes changing environmental conditions force bacteria to boost protein expression above the level that can be achieved by transcriptional or translational control. Gene duplication and amplification (GDA) represents a simple and effective means to augment protein expression and is frequently associated with the development of resistance against antibacterial agents. As such GDAs can be seen as recent evolutionary adaptions towards novel selective pressures within the environment. We describe herein the GDA of the isd locus in a clinical isolate of Staphylococcus lugdunensis a bacterial species frequently associated with infectious endocarditis. This amplification made individual lineages significantly more successful when competing for the trace element iron supplied in the form of hemoglobin (hb). Human body fluids are actively depleted of iron to prevent bacterial proliferation and hb represents the most abundant iron source during infection. This deepens our understanding about adaption processes of pathogens and demonstrates how selective pressures drive the evolution of pathogens to become more successful. This study suggests that investigating GDAs in clinical isolates can help to identify chromosomal regions that are of special importance for bacterial fitness under changing environmental conditions. The gene products can therefore represent attractive targets for novel antibiotics supporting the natural immune defenses by targeting the vulnerable spots of the bacterial anti-immunity strategies.
Collapse
Affiliation(s)
- Simon Heilbronner
- Microbiology Department, Trinity College, Dublin, Ireland
- Infection Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
- * E-mail:
| | - Ian R. Monk
- Microbiology Department, Trinity College, Dublin, Ireland
- Department of Microbiology and Immunology, University of Melbourne, Doherty Institute for Infection and Immunity, Parkville, Victoria, Australia
| | - Jeremy R. Brozyna
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - David E. Heinrichs
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Eric P. Skaar
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University School of Medicine and Tennessee Valley Healthcare Systems, US Department of Veterans Affairs, Nashville, Tennessee, United States of America
| | - Andreas Peschel
- Infection Biology, Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Tübingen, Germany
| | | |
Collapse
|