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Mikhailovich V, Heydarov R, Zimenkov D, Chebotar I. Stenotrophomonas maltophilia virulence: a current view. Front Microbiol 2024; 15:1385631. [PMID: 38741741 PMCID: PMC11089167 DOI: 10.3389/fmicb.2024.1385631] [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: 02/14/2024] [Accepted: 04/15/2024] [Indexed: 05/16/2024] Open
Abstract
Stenotrophomonas maltophilia is an opportunistic pathogen intrinsically resistant to multiple and broad-spectrum antibiotics. Although the bacterium is considered a low-virulence pathogen, it can cause various severe diseases and contributes significantly to the pathogenesis of multibacterial infections. During the COVID-19 pandemic, S. maltophilia has been recognized as one of the most common causative agents of respiratory co-infections and bacteremia in critically ill COVID-19 patients. The high ability to adapt to unfavorable environments and new habitat niches, as well as the sophisticated switching of metabolic pathways, are unique mechanisms that attract the attention of clinical researchers and experts studying the fundamental basis of virulence. In this review, we have summarized the current knowledge on the molecular aspects of S. maltophilia virulence and putative virulence factors, partially touched on interspecific bacterial interactions and iron uptake systems in the context of virulence, and have not addressed antibiotic resistance.
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Affiliation(s)
- Vladimir Mikhailovich
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Rustam Heydarov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Danila Zimenkov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Igor Chebotar
- Pirogov Russian National Research Medical University, Moscow, Russia
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Liao CH, Lu HF, Yang CW, Yeh TY, Lin YT, Yang TC. HemU and TonB1 contribute to hemin acquisition in Stenotrophomonas maltophilia. Front Cell Infect Microbiol 2024; 14:1380976. [PMID: 38596648 PMCID: PMC11002078 DOI: 10.3389/fcimb.2024.1380976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 03/12/2024] [Indexed: 04/11/2024] Open
Abstract
Introduction The hemin acquisition system is composed of an outer membrane TonB-dependent transporter that internalizes hemin into the periplasm, periplasmic hemin-binding proteins to shuttle hemin, an inner membrane transporter that transports hemin into the cytoplasm, and cytoplasmic heme oxygenase to release iron. Fur and HemP are two known regulators involved in the regulation of hemin acquisition. The hemin acquisition system of Stenotrophomonas maltophilia is poorly understood, with the exception of HemA as a TonB-dependent transporter for hemin uptake. Methods Putative candidates responsible for hemin acquisition were selected via a homolog search and a whole-genome survey of S. maltophilia. Operon verification was performed by reverse transcription-polymerase chain reaction. The involvement of candidate genes in hemin acquisition was assessed using an in-frame deletion mutant construct and iron utilization assays. The transcript levels of candidate genes were determined using quantitative polymerase chain reaction. Results Smlt3896-hemU-exbB2-exbD2-tonB2 and tonB1-exbB1-exbD1a-exbD1b operons were selected as candidates for hemin acquisition. Compared with the parental strain, hemU and tonB1 mutants displayed a defect in their ability to use hemin as the sole iron source for growth. However, hemin utilization by the Smlt3896 and tonB2 mutants was comparable to that of the parental strain. HemA expression was repressed by Fur in iron-replete conditions and derepressed in iron-depleted conditions. HemP negatively regulated hemA expression. Like hemA, hemU was repressed by Fur in iron-replete conditions; however, hemU was moderately derepressed in response to iron-depleted stress and fully derepressed when hemin was present. Unlike hemA and hemU, the TonB1-exbB1-exbD1a-exbD1b operon was constitutively expressed, regardless of the iron level or the presence of hemin, and Fur and HemP had no influence on its expression. Conclusion HemA, HemU, and TonB1 contribute to hemin acquisition in S. maltophilia. Fur represses the expression of hemA and hemU in iron-replete conditions. HemA expression is regulated by low iron levels, and HemP acts as a negative regulator of this regulatory circuit. HemU expression is regulated by low iron and hemin levels in a hemP-dependent manner.
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Affiliation(s)
- Chun-Hsing Liao
- Division of Infectious Disease, Far Eastern Memorial Hospital, New Taipei City, Taiwan
- Department of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Hsu-Feng Lu
- Department of Medical Laboratory Science and Biotechnology, Asia University, Taichung, Taiwan
| | - Ching-Wei Yang
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Ting-Yu Yeh
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Yi-Tsung Lin
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
- School of Medicine, National Yang Chiao Tung University, Taipei, Taiwan
| | - Tsuey-Ching Yang
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
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Lee YL, Hsueh PR. Emerging infections in vulnerable hosts: Stenotrophomonas maltophilia and Elizabethkingia anophelis. Curr Opin Infect Dis 2023; 36:481-494. [PMID: 37548375 DOI: 10.1097/qco.0000000000000953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
PURPOSE OF REVIEW This systematic review aimed to explore the recent trends in the epidemiology, risk factors, and antimicrobial susceptibility of two emerging opportunistic pathogens, Stenotrophomonas maltophilia and Elizabethkingia anophelis . RECENT FINDINGS Since 2020, numerous outbreaks of S. maltophilia and E. anophelis have been reported worldwide. Most of these outbreaks have been associated with healthcare facilities, although one outbreak caused by E. anophelis in France was considered a community-associated infection. In terms of antimicrobial susceptibility, trimethoprim/sulfamethoxazole (TMP-SMZ), levofloxacin, and minocycline have exhibited good efficacy against S. maltophilia . Additionally, cefiderocol and a combination of aztreonam and avibactam have shown promising results in in vitro susceptibility testing. For E. anophelis , there is currently no consensus on the optimal treatment. Although some studies have reported good efficacy with rifampin, TMP-SMZ, piperacillin/tazobactam, and cefoperazone/sulbactam, minocycline had the most favourable in vitro susceptibility rates. Cefiderocol may serve as an alternative due to its low minimum inhibitory concentration (MIC) against E. anophelis . The role of vancomycin in treatment is still uncertain, although several successful cases with vancomycin treatment, even with high MIC values, have been reported. SUMMARY Immunocompromised patients are particularly vulnerable to infections caused by S. maltophilia and E. anophelis , but the optimal treatment strategy remains inconclusive. Further research is necessary to determine the most effective use of conventional and novel antimicrobial agents in combatting these multidrug-resistant pathogens.
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Affiliation(s)
- Yu-Lin Lee
- Department of Internal Medicine, Chung Shan Medical University Hospital
- School of Medicine, Chung Shan Medical University
- PhD Program in Medical Biotechnology, National Chung-Hsing University
| | - Po-Ren Hsueh
- Departments of Laboratory Medicine and Internal Medicine, China Medical University Hospital
- School of Medicine
- PhD Program for Aging, School of Medicine, China Medical University, Taichung
- Departments of Laboratory Medicine and Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan
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Wu CM, Li LH, Lin YL, Wu CJ, Lin YT, Yang TC. The sbiTRS Operon Contributes to Stenobactin-Mediated Iron Utilization in Stenotrophomonas maltophilia. Microbiol Spectr 2022; 10:e0267322. [PMID: 36453931 PMCID: PMC9769818 DOI: 10.1128/spectrum.02673-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 11/17/2022] [Indexed: 12/03/2022] Open
Abstract
Iron is an essential micronutrient for various bacterial cellular processes. Fur is a global transcriptional regulator participating in iron homeostasis. Stenotrophomonas maltophilia is a ubiquitous environmental bacterium that has emerged as an opportunistic pathogen. To elucidate the novel regulatory mechanism behind iron homeostasis in S. maltophilia, wild-type KJ and KJΔFur, a fur mutant, were subjected to transcriptome assay. A five-gene cluster, sbiBA-sbiTRS, was significantly upregulated in KJΔFur. SbiAB is an ATP type efflux pump, SbiT is an inner membrane protein, and SbiSR is a two-component regulatory system (TCS). The sbiTRS operon organization was verified by reverse transcription-PCR (RT-PCR). Localization prediction and bacterial two-hybrid studies revealed that SbiT resided in the inner membrane and had an intramembrane interaction with SbiS. In iron-replete conditions, SbiT interacted with SbiS and maintained SbiSR TCS in a resting state. In response to iron depletion stress, SbiT no longer interacted with SbiS, leading to SbiSR TCS activation. The iron source utilization assay demonstrated the contribution of SbiSR TCS to stenobactin-mediated ferric iron utilization but notto the utilization of hemin and ferric citrate. Furthermore, SmeDEF and SbiAB pumps, known stenobactin secretion outlets, were members of the SbiSR regulon. Collectively, in an iron-depleted condition, SbiSR activation is regulated by Fur at the transcriptional level and by SbiT at the posttranslational level. Activated SbiSR contributes to stenobactin-mediated ferric iron utilization by upregulating the smeDEF and sbiAB operons. SbiSR is the first TCS found to be involved in iron homeostasis in S. maltophilia. IMPORTANCE Therapeutic options for Stenotrophomonas maltophilia infections are limited because S. maltophilia is intrinsically resistant to several antibiotics. Iron is an essential element for viability, but iron overload is a lethal threat to bacteria. Therefore, disruption of iron homeostasis can be an alternative strategy to cope with S. maltophilia infection. The intricate regulatory networks involved in iron hemostasis have been reported in various pathogens; however, little is known about S. maltophilia. Herein, a novel sbiTRS operon, a member of Fur regulon, was characterized. SbiT, an inner membrane protein, negatively modulated the SbiSR two-component regulatory system by intramembrane protein-protein interaction with SbiS. In response to iron-depleted stress, SbiSR was activated via the regulation of Fur and SbiT. Activated SbiSR upregulated smeDEF and sbiAB, which contributed to stenobactin-mediated ferric iron utilization. A novel fur-sbiT-sbiSR-smeDEF/sbiAB regulatory circuit in S. maltophilia was revealed.
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Affiliation(s)
- Cheng-Mu Wu
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Li-Hua Li
- Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Yen-Ling Lin
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Chao-Jung Wu
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Yi-Tsung Lin
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
- Department of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Tsuey-Ching Yang
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
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Liao C, Huang X, Wang Q, Yao D, Lu W. Virulence Factors of Pseudomonas Aeruginosa and Antivirulence Strategies to Combat Its Drug Resistance. Front Cell Infect Microbiol 2022; 12:926758. [PMID: 35873152 PMCID: PMC9299443 DOI: 10.3389/fcimb.2022.926758] [Citation(s) in RCA: 86] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 06/09/2022] [Indexed: 11/24/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen causing nosocomial infections in severely ill and immunocompromised patients. Ubiquitously disseminated in the environment, especially in hospitals, it has become a major threat to human health due to the constant emergence of drug-resistant strains. Multiple resistance mechanisms are exploited by P. aeruginosa, which usually result in chronic infections difficult to eradicate. Diverse virulence factors responsible for bacterial adhesion and colonization, host immune suppression, and immune escape, play important roles in the pathogenic process of P. aeruginosa. As such, antivirulence treatment that aims at reducing virulence while sparing the bacterium for its eventual elimination by the immune system, or combination therapies, has significant advantages over traditional antibiotic therapy, as the former imposes minimal selective pressure on P. aeruginosa, thus less likely to induce drug resistance. In this review, we will discuss the virulence factors of P. aeruginosa, their pathogenic roles, and recent advances in antivirulence drug discovery for the treatment of P. aeruginosa infections.
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Affiliation(s)
- Chongbing Liao
- Key Laboratory of Medical Molecular Virology (Ministry of Education (MOE)/National Health Commission (NHC)/Chinese Academy of Medical Sciences (CAMS)), School of Basic Medical Science, Fudan University, Shanghai, China
| | - Xin Huang
- Key Laboratory of Medical Molecular Virology (Ministry of Education (MOE)/National Health Commission (NHC)/Chinese Academy of Medical Sciences (CAMS)), School of Basic Medical Science, Fudan University, Shanghai, China
| | - Qingxia Wang
- Key Laboratory of Medical Molecular Virology (Ministry of Education (MOE)/National Health Commission (NHC)/Chinese Academy of Medical Sciences (CAMS)), School of Basic Medical Science, Fudan University, Shanghai, China
| | - Dan Yao
- Key Laboratory of Medical Molecular Virology (Ministry of Education (MOE)/National Health Commission (NHC)/Chinese Academy of Medical Sciences (CAMS)), School of Basic Medical Science, Fudan University, Shanghai, China
| | - Wuyuan Lu
- Key Laboratory of Medical Molecular Virology (Ministry of Education (MOE)/National Health Commission (NHC)/Chinese Academy of Medical Sciences (CAMS)), School of Basic Medical Science, Fudan University, Shanghai, China
- Shanghai Institute of Infectious Disease and Biosecurity, School of Public Health, Fudan University, Shanghai, China
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Wu CJ, Chen Y, Li LH, Wu CM, Lin YT, Ma CH, Yang TC. Roles of SmeYZ, SbiAB, and SmeDEF Efflux Systems in Iron Homeostasis of Stenotrophomonas maltophilia. Microbiol Spectr 2022; 10:e0244821. [PMID: 35647692 PMCID: PMC9241820 DOI: 10.1128/spectrum.02448-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 04/30/2022] [Indexed: 11/28/2022] Open
Abstract
Stenotrophomonas maltophilia, a nonfermenting Gram-negative rod, is frequently isolated from the environment and is emerging as a multidrug-resistant global opportunistic pathogen. S. maltophilia harbors eight RND-type efflux pumps that contribute to multidrug resistance and physiological functions. Among the eight efflux pumps, SmeYZ pump is constitutively highly expressed. In our previous study, we demonstrated that loss-of-function of the SmeYZ pump results in pleiotropic phenotypes, including abolished swimming motility, decreased secreted protease activity, and compromised tolerance to oxidative stress and antibiotics. In this study, we attempted to elucidate the underlying mechanisms responsible for ΔsmeYZ-mediated pleiotropic phenotypes. RNA-seq transcriptome analysis and subsequent confirmation with qRT-PCR revealed that smeYZ mutant experienced an iron starvation response because the genes involved in the synthesis and uptake of stenobactin, the sole siderophore of S. maltophilia, were significantly upregulated. We further verified that smeYZ mutant had low intracellular iron levels via inductively coupled plasma mass spectrometry (ICP-MS). Also, KJΔYZ was more sensitive to 2,2'-dipyridyl (DIP), a ferrous iron chelator, in comparison with the wild type. The contribution of SmeYZ, SmeDEF, and SbiAB pumps to stenobactin secretion was suggested by qRT-PCR and further verified by Chrome Azurol S (CAS) activity, iron source utilization, and cell viability assays. We also demonstrated that loss-of-function of SmeYZ led to the compensatory upregulation of SbiAB and SmeDEF pumps for stenobactin secretion. The overexpression of the SbiAB pump resulted in a reduction in intracellular iron levels, which may be the key factor responsible for the ΔsmeYZ-mediated pleiotropic phenotypes, except for antibiotic extrusion. IMPORTANCE Efflux pumps display high efficiency of drug extrusion, which underlies their roles in multidrug resistance. In addition, efflux pumps have physiological functions, and their expression is tightly regulated by various environmental and physiological signals. Functional redundancy of efflux pumps is commonly observed, and mutual regulation occurs among these functionally redundant pumps in a bacterium. Stenotrophomonas maltophilia is an opportunistic pathogen that shows intrinsic multi-drug resistance. In this study, we demonstrated that SmeYZ, SbiAB, and SmeDEF efflux pumps of S. maltophilia display functional redundancy in siderophore secretion. Inactivation of smeYZ led to the upregulation of smeDEF and sbiAB. Unexpectedly, sbiAB overexpression resulted in the reduction of intracellular iron levels, which led to pleiotropic defects in smeYZ mutant. This study demonstrates a previously unidentified connection between efflux pumps, siderophore secretion, and intracellular iron levels in S. maltophilia.
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Affiliation(s)
- Chao-Jung Wu
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Yu Chen
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Li-Hua Li
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
- Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Cheng-Mu Wu
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Yi-Tsung Lin
- Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
- School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Cheng-Hua Ma
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
| | - Tsuey-Ching Yang
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
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Involvement of the hemP-hemA-smlt0796-smlt0797 Operon in Hemin Acquisition by Stenotrophomonas maltophilia. Microbiol Spectr 2022; 10:e0032122. [PMID: 35658602 PMCID: PMC9241770 DOI: 10.1128/spectrum.00321-22] [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: 11/25/2022] Open
Abstract
The hemin acquisition system of Stenotrophomonas maltophilia was elucidated in this study. To identify the TonB-dependent outer membrane receptor for hemin in S. maltophilia, the hemin acquisition systems of Pseudomonas aeruginosa were referenced. PhuR, HasA, and HxuA are three known TonB-dependent outer membrane receptors involved in hemin acquisition by P. aeruginosa. Thus, HemA (Smlt0795) and Smlt2937, the orthologs of PhuR and HasA/HxuA in S. maltophilia, were first considered. KJΔEnt, a stenobactin-null strain, was used as the parental strain for the hemin utilization assay. Deletion of hemA, but not Smlt2937, of KJΔEnt impaired hemin acquisition under iron-depleted conditions, indicating that HemA is the TonB-dependent receptor for hemin uptake. The hemA gene is a member of the hemP-hemA-smlt0796-smlt0797 operon, whose expression was upregulated in a fur mutant and under iron-depleted conditions. The contribution of the hemP-hemA-smlt0796-smlt0797 operon to hemin acquisition was investigated by in-frame deletion mutant construction and hemin utilization assays. Inactivation of hemP, smlt0796, and smlt0797 of KJΔEnt insignificantly affected hemin acquisition under iron-depleted conditions. However, hemP deletion in a fur mutant increased hemin acquisition under iron-depleted conditions. Collectively, we revealed that (i) HemA likely functions as the outer membrane receptor for hemin uptake; (ii) HemP, a predicted transcriptional factor, apparently functions as a repressor of the expression of the hemA transcript; and (iii) in a fur mutant, HemP has a negative impact on hemin acquisition under iron-depleted conditions. IMPORTANCEStenotrophomonas maltophilia is an emerging multidrug-resistant opportunistic pathogen, increasing the difficulty of treatment of this infection. Iron is a critical element for bacterial viability. Heme is the most abundant iron source in the human host; thus, heme is the major iron source for a pathogen in the infection niche. Blocking iron acquisition from heme can be an alternative strategy to control S. maltophilia infection. Although several hemin acquisition systems have been reported in various pathogens, very little is known about the hemin acquisition systems of S. maltophilia. By in-frame deletion mutant construction and hemin utilization assays, we demonstrated that HemA (Smlt0795) is the TonB-dependent outer membrane receptor for hemin uptake and that HemP (Smlt0794), a predicted transcriptional factor, had a negative impact on hemin acquisition in a fur mutant. The negative regulatory role of HemP in hemin acquisition is first reported.
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