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Becker K. Detection, Identification and Diagnostic Characterization of the Staphylococcal Small Colony-Variant (SCV) Phenotype. Antibiotics (Basel) 2023; 12:1446. [PMID: 37760742 PMCID: PMC10525764 DOI: 10.3390/antibiotics12091446] [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: 08/23/2023] [Revised: 09/08/2023] [Accepted: 09/11/2023] [Indexed: 09/29/2023] Open
Abstract
While modern molecular methods have decisively accelerated and improved microbiological diagnostics, phenotypic variants still pose a challenge for their detection, identification and characterization. This particularly applies if they are unstable and hard to detect, which is the case for the small-colony-variant (SCV) phenotype formed by staphylococci. On solid agar media, staphylococcal SCVs are characterized by tiny colonies with deviant colony morphology. Their reduced growth rate and fundamental metabolic changes are the result of their adaptation to an intracellular lifestyle, regularly leading to specific auxotrophies, such as for menadione, hemin or thymidine. These alterations make SCVs difficult to recognize and render physiological, biochemical and other growth-based methods such as antimicrobial susceptibility testing unreliable or unusable. Therefore, diagnostic procedures require prolonged incubation times and, if possible, confirmation by molecular methods. A special approach is needed for auxotrophy testing. However, standardized protocols for SCV diagnostics are missing. If available, SCVs and their putative parental isolates should be genotyped to determine clonality. Since their detection has significant implications for the treatment of the infection, which is usually chronic and relapsing, SCV findings should be specifically reported, commented on, and managed in close collaboration with the microbiological laboratory and the involved clinicians.
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Affiliation(s)
- Karsten Becker
- Friedrich Loeffler-Institute of Medical Microbiology, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße 1, 17489 Greifswald, Germany
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Zhou S, Rao Y, Li J, Huang Q, Rao X. Staphylococcus aureus small-colony variants: Formation, infection, and treatment. Microbiol Res 2022; 260:127040. [DOI: 10.1016/j.micres.2022.127040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 04/10/2022] [Accepted: 04/11/2022] [Indexed: 10/18/2022]
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Abstract
Respiratory mutants, both naturally occurring and genetically constructed, have taught us about the importance of metabolism in influencing virulence factor production, persistence, and antibiotic resistance. As we learn more about small colony variants, we find that Staphylococcus aureus has many pathways to produce small colony variants, although the respiratory variants are the best described clinically and in the laboratory.
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MpsAB is important for Staphylococcus aureus virulence and growth at atmospheric CO 2 levels. Nat Commun 2019; 10:3627. [PMID: 31399577 PMCID: PMC6689103 DOI: 10.1038/s41467-019-11547-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 07/16/2019] [Indexed: 01/06/2023] Open
Abstract
The mechanisms behind carbon dioxide (CO2) dependency in non-autotrophic bacterial isolates are unclear. Here we show that the Staphylococcus aureus mpsAB operon, known to play a role in membrane potential generation, is crucial for growth at atmospheric CO2 levels. The genes mpsAB can complement an Escherichia coli carbonic anhydrase (CA) mutant, and CA from E. coli can complement the S. aureus delta-mpsABC mutant. In comparison with the wild type, S. aureus mps mutants produce less hemolytic toxin and are less virulent in animal models of infection. Homologs of mpsA and mpsB are widespread among bacteria and are often found adjacent to each other on the genome. We propose that MpsAB represents a dissolved inorganic carbon transporter, or bicarbonate concentrating system, possibly acting as a sodium bicarbonate cotransporter.
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Schleimer N, Kaspar U, Knaack D, von Eiff C, Molinaro S, Grallert H, Idelevich EA, Becker K. In Vitro Activity of the Bacteriophage Endolysin HY-133 against Staphylococcus aureus Small-Colony Variants and Their Corresponding Wild Types. Int J Mol Sci 2019; 20:E716. [PMID: 30736446 PMCID: PMC6387228 DOI: 10.3390/ijms20030716] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/01/2019] [Accepted: 02/02/2019] [Indexed: 01/06/2023] Open
Abstract
Nasal carriage of methicillin-susceptible (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) represents both a source and a risk factor for subsequent infections. However, existing MRSA decolonization strategies and antibiotic treatment options are hampered by the duration of administration and particularly by the emergence of resistance. Moreover, beyond classical resistance mechanisms, functional resistance as the formation of the small-colony variant (SCV) phenotype may also impair the course and treatment of S. aureus infections. For the recombinant bacteriophage endolysin HY-133, rapid bactericidal and highly selective in vitro activities against MSSA and MRSA has been shown. In order to assess the in vitro efficacy of HY-133 against the SCV phenotype, minimal inhibitory (MIC) and minimal bactericidal concentrations (MBC) were evaluated on clinical SCVs, their isogenic wild types, as well as on genetically derived and gentamicin-selected SCVs. For all strains and growth phases, HY-133 MIC and MBC ranged between 0.12 and 1 mg/L. Time-kill studies revealed a fast-acting bactericidal activity of HY-133 resulting in a ≥3 - log10 decrease in CFU/mL within 1 h compared to oxacillin, which required 4⁻24 h. Since the mode of action of HY-133 was independent of growth phase, resistance pattern, and phenotype, it is a promising candidate for future S. aureus decolonization strategies comprising rapid activity against phenotypic variants exhibiting functional resistance.
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Affiliation(s)
- Nina Schleimer
- Institute of Medical Microbiology, University Hospital Münster (UKM), 48149 Münster, Germany.
| | - Ursula Kaspar
- Institute of Medical Microbiology, University Hospital Münster (UKM), 48149 Münster, Germany.
| | - Dennis Knaack
- Institute of Medical Microbiology, University Hospital Münster (UKM), 48149 Münster, Germany.
| | - Christof von Eiff
- Institute of Medical Microbiology, University Hospital Münster (UKM), 48149 Münster, Germany.
| | | | | | - Evgeny A Idelevich
- Institute of Medical Microbiology, University Hospital Münster (UKM), 48149 Münster, Germany.
| | - Karsten Becker
- Institute of Medical Microbiology, University Hospital Münster (UKM), 48149 Münster, Germany.
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Durham ME, Elfenbein JR. Evaluation of vaporized hydrogen peroxide sterilization on the in vitro efficacy of meropenem-impregnated polymethyl methacrylate beads. Am J Vet Res 2019; 80:45-50. [PMID: 30605028 DOI: 10.2460/ajvr.80.1.45] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate the effects of vaporized hydrogen peroxide (VHP) sterilization on the in vitro antimicrobial efficacy of meropenem-impregnated polymethyl methacrylate (M-PMMA) beads. SAMPLE 6-mm-diameter polymethyl methacrylate beads that were or were not impregnated with meropenem. PROCEDURES Meropenem-free polymethyl methacrylate and M-PMMA beads were sterilized by use of an autoclave or VHP or remained unsterilized. To determine the antimicrobial efficacy of each bead-sterilization combination (treatment), Mueller-Hinton agar plates were inoculated with 1 of 6 common equine pathogens, and 1 bead from each treatment was applied to a sixth of each plate. The zone of bacterial inhibition for each treatment was measured after 24 hours. To estimate the duration of antimicrobial elution into a solid or liquid medium, 1 bead from each treatment was transferred every 24 hours to a new Staphylococcus aureus-inoculated agar plate or a tube with PBS solution, and an aliquot of the eluent from each tube was then applied to a paper disc on an S aureus-inoculated agar plate. All agar plates were incubated for 24 hours, and the zone of bacterial inhibition was measured for each treatment. RESULTS In vitro antimicrobial efficacy of M-PMMA beads was retained following VHP sterilization. The duration of antimicrobial elution in solid and liquid media did not differ significantly between unsterilized and VHP-sterilized M-PMMA beads. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that M-PMMA beads retained in vitro antimicrobial activity and eluted the drug for up to 2 weeks after VHP sterilization.
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Idelevich EA, Kriegeskorte A, Schleimer N, Peters G, von Eiff C, Becker K. In Vitro Susceptibility of Clinical Staphylococcus aureus Small-Colony Variants to β-Lactam and Non-β-Lactam Antibiotics. Antimicrob Agents Chemother 2018; 62:e02532-17. [PMID: 29378720 PMCID: PMC5913952 DOI: 10.1128/aac.02532-17] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 01/19/2018] [Indexed: 02/08/2023] Open
Abstract
The Staphylococcus aureus small-colony variant (SCV) phenotype has been associated with relapsing and antibiotic-refractory infections. However, little is known about the activities of antibiotics on clinical SCVs. Here, we demonstrated that SCVs without detectable auxotrophies were at least as susceptible to most β-lactam and non-β-lactam antibiotics in vitro as their corresponding clonally identical strains with a normal phenotype. After prolonged incubation, a regrowth phenomenon has been observed in gradient diffusion inhibition zones irrespective of the strains' phenotype.
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Affiliation(s)
- Evgeny A Idelevich
- Institute of Medical Microbiology, University Hospital Münster, Münster, Germany
| | - André Kriegeskorte
- Institute of Medical Microbiology, University Hospital Münster, Münster, Germany
| | - Nina Schleimer
- Institute of Medical Microbiology, University Hospital Münster, Münster, Germany
| | - Georg Peters
- Institute of Medical Microbiology, University Hospital Münster, Münster, Germany
| | - Christof von Eiff
- Institute of Medical Microbiology, University Hospital Münster, Münster, Germany
| | - Karsten Becker
- Institute of Medical Microbiology, University Hospital Münster, Münster, Germany
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Richter K, Thomas N, Zhang G, Prestidge CA, Coenye T, Wormald PJ, Vreugde S. Deferiprone and Gallium-Protoporphyrin Have the Capacity to Potentiate the Activity of Antibiotics in Staphylococcus aureus Small Colony Variants. Front Cell Infect Microbiol 2017; 7:280. [PMID: 28690982 PMCID: PMC5479885 DOI: 10.3389/fcimb.2017.00280] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 06/08/2017] [Indexed: 11/13/2022] Open
Abstract
Small colony variants (SCVs) of bacteria like Staphylococcus aureus are characterized by a reduced colony size and are linked to increased antibiotic tolerance and resistance. Their altered expression of virulence factors, slow growing properties and their ability to form biofilms make the eradication of SCVs challenging. In the context of biofilm-related infectious diseases involving S. aureus SCVs, a therapy targeting bacterial iron metabolism was evaluated. The combination of the iron-chelator deferiprone (Def) and the heme-analog gallium-protoporphyrin (GaPP), in solution and incorporated in a surgical wound gel, was tested for activity against planktonic and sessile SCVs. To this end, the activity of Def-GaPP was assessed against planktonic S. aureus SCVs, as well as against in vitro and in vivo biofilms in the colony biofilm model, an artificial wound model and a Caenorhabditis elegans infection model. While Def alone failed to show substantial antibacterial activity, GaPP and the combination of Def-GaPP demonstrated concentration- and strain-dependent antibacterial properties. Specifically, the Def-GaPP combination significantly reduced the bacterial load in an artificial wound model and increased the survival of S. aureus SCV infected C. elegans. When Def-GaPP were combined with gentamicin or ciprofloxacin, the triple combinations exceeded the antibiofilm activity of the individual compounds in the colony biofilm model. In targeting bacterial iron metabolism, Def-GaPP showed significant activity against planktonic and sessile SCVs. Moreover, Def-GaPP could potentiate the activity of gentamicin and ciprofloxacin. Delivered in a wound healing gel, Def-GaPP showed promise as a new topical strategy against infections with S. aureus SCVs.
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Affiliation(s)
- Katharina Richter
- Department of Surgery, Otolaryngology Head and Neck Surgery, Basil Hetzel Institute for Translational Health Research, The Queen Elizabeth Hospital, University of AdelaideAdelaide, SA, Australia
| | - Nicky Thomas
- School of Pharmacy and Medical Sciences, University of South AustraliaAdelaide, SA, Australia.,Adelaide Biofilm Test Facility, Sansom Institute for Health Research, University of South AustraliaAdelaide, SA, Australia
| | - Guimin Zhang
- Department of Otolaryngology Head and Neck Surgery, Tianjin First Center HospitalTianjin, China
| | - Clive A Prestidge
- School of Pharmacy and Medical Sciences, University of South AustraliaAdelaide, SA, Australia.,ARC Centre of Excellence in Convergent Bio-Nano Science and TechnologyAdelaide, SA, Australia
| | - Tom Coenye
- Laboratory of Pharmaceutical Microbiology, Ghent UniversityGhent, Belgium
| | - Peter-John Wormald
- Department of Surgery, Otolaryngology Head and Neck Surgery, Basil Hetzel Institute for Translational Health Research, The Queen Elizabeth Hospital, University of AdelaideAdelaide, SA, Australia
| | - Sarah Vreugde
- Department of Surgery, Otolaryngology Head and Neck Surgery, Basil Hetzel Institute for Translational Health Research, The Queen Elizabeth Hospital, University of AdelaideAdelaide, SA, Australia
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Clinical Significance and Pathogenesis of Staphylococcal Small Colony Variants in Persistent Infections. Clin Microbiol Rev 2016; 29:401-27. [PMID: 26960941 DOI: 10.1128/cmr.00069-15] [Citation(s) in RCA: 205] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Small colony variants (SCVs) were first described more than 100 years ago for Staphylococcus aureus and various coagulase-negative staphylococci. Two decades ago, an association between chronic staphylococcal infections and the presence of SCVs was observed. Since then, many clinical studies and observations have been published which tie recurrent, persistent staphylococcal infections, including device-associated infections, bone and tissue infections, and airway infections of cystic fibrosis patients, to this special phenotype. By their intracellular lifestyle, SCVs exhibit so-called phenotypic (or functional) resistance beyond the classical resistance mechanisms, and they can often be retrieved from therapy-refractory courses of infection. In this review, the various clinical infections where SCVs can be expected and isolated, diagnostic procedures for optimized species confirmation, and the pathogenesis of SCVs, including defined underlying molecular mechanisms and the phenotype switch phenomenon, are presented. Moreover, relevant animal models and suggested treatment regimens, as well as the requirements for future research areas, are highlighted.
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Matarlo JS, Lu Y, Daryaee F, Daryaee T, Ruzsicska B, Walker SG, Tonge PJ. A Methyl 4-Oxo-4-phenylbut-2-enoate with in Vivo Activity against MRSA that Inhibits MenB in the Bacterial Menaquinone Biosynthesis Pathway. ACS Infect Dis 2016; 2:329-340. [PMID: 27294200 DOI: 10.1021/acsinfecdis.6b00023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
4-Oxo-4-phenyl-but-2-enoates inhibit MenB, the 1,4-dihydroxyl-2-naphthoyl-CoA synthase in the bacterial menaquinone (MK) biosynthesis pathway, through the formation of an adduct with coenzyme A (CoA). Here, we show that the corresponding methyl butenoates have MIC values as low as 0.35-0.75 µg/mL against drug sensitive and resistant strains of Staphylococcus aureus. Mode of action studies on the most potent compound, methyl 4-(4-chlorophenyl)-4-oxobut-2-enoate (1), reveal that 1 is converted into the corresponding CoA adduct in S. aureus cells, and that this adduct binds to the S. aureus MenB (saMenB) with a Kd value of 2 µM. The antibacterial spectrum of 1 is limited to bacteria that utilize MK for respiration, and the activity of 1 can be complemented with exogenous MK or menadione. Finally, treatment of methicillin-resistant S. aureus (MRSA) with 1 results in the small colony variant phenotype and thus 1 phenocopies knockout of the menB gene. Taken together the data indicate that the antibacterial activity of 1 results from a specific effect on MK biosynthesis. We also evaluated the in vivo efficacy of 1 using two mouse models of MRSA infection. Notably, compound 1 increased survival in a systemic infection model and resulted in a dose-dependent decrease in bacterial load in a thigh infection model, validating MenB as a target for the development of new anti-MRSA candidates.
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Affiliation(s)
- Joe S. Matarlo
- Institute of Chemical Biology & Drug Discovery, Department of Chemistry, and ‡Department of Oral Biology and Pathology, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Yang Lu
- Institute of Chemical Biology & Drug Discovery, Department of Chemistry, and ‡Department of Oral Biology and Pathology, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Fereidoon Daryaee
- Institute of Chemical Biology & Drug Discovery, Department of Chemistry, and ‡Department of Oral Biology and Pathology, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Taraneh Daryaee
- Institute of Chemical Biology & Drug Discovery, Department of Chemistry, and ‡Department of Oral Biology and Pathology, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Bela Ruzsicska
- Institute of Chemical Biology & Drug Discovery, Department of Chemistry, and ‡Department of Oral Biology and Pathology, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Stephen G. Walker
- Institute of Chemical Biology & Drug Discovery, Department of Chemistry, and ‡Department of Oral Biology and Pathology, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Peter J. Tonge
- Institute of Chemical Biology & Drug Discovery, Department of Chemistry, and ‡Department of Oral Biology and Pathology, Stony Brook University, Stony Brook, New York 11794-3400, United States
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Yagci S, Sancak B, Hascelik G. Detection of Small Colony Variants Among Methicillin-Resistant Staphylococcus aureus Blood Isolates. Microb Drug Resist 2016; 22:712-716. [PMID: 27058213 DOI: 10.1089/mdr.2015.0176] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Staphylococcus aureus small colony variants (SCVs) are associated with chronic and persistent infections. Methicillin-resistant S. aureus (MRSA) SCVs cause more severe infections and mortality rates are higher in comparison with infections caused by MRSA. Our objective was to document the prevalence and phenotypical characteristics of SCVs among MRSA blood isolates. MRSA strains isolated from blood during 1999-2009 were evaluated retrospectively. Among 299 MRSA isolates, suspected colonies were inoculated onto Columbia blood agar and Schaedler agar. Columbia blood agar was incubated in normal atmosphere and Schaedler agar in 5-10% CO2, both at 35°C. If the small, nonpigmented, nonhemolytic colonies on Columbia blood agar were seen as normal-sized, hemolytic, and pigmented colonies on Schaedler agar, they were considered as MRSA SCVs. Six MRSA SCVs were detected. When subcultures were made, four of them reversed to phenotypically normal S. aureus, but two isolates were stable as SCV phenotype. The prevalence of SCVs among MRSA blood isolates was found as 6/299 (2%) with 2 (0.67%) stable. The detection of SCVs among MRSA blood isolates was reported from Turkey for the first time in this study. As the clinical significance of MRSA infections is well documented, evaluation of MRSA SCVs in clinical samples, especially from intensive care patients and those who have chronic and persistent infections are important to consider.
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Affiliation(s)
- Server Yagci
- 1 Department of Microbiology and Clinical Microbiology, Pamukkale University , Denizli, Turkey
| | - Banu Sancak
- 2 Department of Microbiology and Clinical Microbiology, Hacettepe University , Ankara, Turkey
| | - Gulsen Hascelik
- 2 Department of Microbiology and Clinical Microbiology, Hacettepe University , Ankara, Turkey
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Evolution of Staphylococcus aureus under vancomycin selective pressure: the role of the small-colony variant phenotype. Antimicrob Agents Chemother 2014; 59:1347-51. [PMID: 25451045 DOI: 10.1128/aac.04508-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Staphylococcus aureus small-colony variants (SCVs) often persist despite antibiotic therapy. Against a 10(8)-CFU/ml methicillin-resistant S. aureus (MRSA) (strain COL) population of which 0%, 1%, 10%, 50%, or 100% was an isogenic hemB knockout (Ia48) subpopulation displaying the SCV phenotype, vancomycin achieved maximal reductions of 4.99, 5.39, 4.50, 3.28, and 1.66 log10 CFU/ml over 48 h. Vancomycin at ≥16 mg/liter shifted a population from 50% SCV cells at 0 h to 100% SCV cells at 48 h, which was well characterized by a Hill-type model (R2>0.90).
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Garcia LG, Lemaire S, Kahl BC, Becker K, Proctor RA, Denis O, Tulkens PM, Van Bambeke F. Antibiotic activity against small-colony variants of Staphylococcus aureus: review of in vitro, animal and clinical data. J Antimicrob Chemother 2013; 68:1455-64. [DOI: 10.1093/jac/dkt072] [Citation(s) in RCA: 133] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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