Thymidine-Dependent
            <i>Staphylococcus aureus</i>
            Small-Colony Variants: Human Pathogens That Are Relevant Not Only in Cases of Cystic Fibrosis Lung Disease

Besier, Silke; Zander, Johannes; Siegel, Ekkehard; Saum, Stephan H.; Hunfeld, Klaus-Peter; Ehrhart, Annabelle; Brade, Volker; Wichelhaus, Thomas A.

doi:10.1128/jcm.01440-08

Cited by 34 publications

(32 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Of note, thymidine dependence seems to universally depend upon random mutations in the thymidylate synthaseencoding thyA gene (leading to an intracellular lack of dTMP). This was not specifically tested here, but these mutants are known to be frequent not only in SCVs isolated from cystic fibrosis patients (as was the strain used here) but also many other infection sites of patients with chronic infections (14). A second property of intracellular SCV that is documented by our data is the considerable decrease in maximal efficacy of most antibiotics, especially in the first 24-h period, not only in comparison with extracellular forms (as was already noted and largely documented for all S. aureus strains studied in our THP-1 macrophage model so far) (8,9,30,46) but also, and in THP-1 macrophages after a 24-h incubation at the extracellular concentrations (total drug) shown in the abscissa.…”

Section: Discussionmentioning

confidence: 99%

Intracellular Activity of Antibiotics in a Model of Human THP-1 Macrophages Infected by a Staphylococcus aureus Small-Colony Variant Strain Isolated from a Cystic Fibrosis Patient: Pharmacodynamic Evaluation and Comparison with Isogenic Normal-Phenotype and Revertant Strains

Nguyen

Denis

Vergison

et al. 2009

Antimicrob Agents Chemother

View full text Add to dashboard Cite

Small-colony variant (SCV) strains of Staphylococcus aureusshow reduced antibiotic susceptibility and intracellular persistence, potentially explaining therapeutic failures. The activities of oxacillin, fusidic acid, clindamycin, gentamicin, rifampin, vancomycin, linezolid, quinupristin-dalfopristin, daptomycin, tigecycline, moxifloxacin, telavancin, and oritavancin have been examined in THP-1 macrophages infected by a stable thymidine-dependent SCV strain in comparison with normal-phenotype and revertant isogenic strains isolated from the same cystic fibrosis patient. The SCV strain grew slowly extracellularly and intracellularly (1-and 0.2-log CFU increase in 24 h, respectively). In confocal and electron microscopy, SCV and the normalphenotype bacteria remain confined in acid vacuoles. All antibiotics tested, except tigecycline, caused a net reduction in bacterial counts that was both time and concentration dependent. At an extracellular concentration corresponding to the maximum concentration in human serum (total drug), oritavancin caused a 2-log CFU reduction at 24 h; rifampin, moxifloxacin, and quinupristin-dalfopristin caused a similar reduction at 72 h; and all other antibiotics had only a static effect at 24 h and a 1-log CFU reduction at 72 h. In concentration dependence experiments, response to oritavancin was bimodal (two successive plateaus of ؊0.4 and ؊3.1 log CFU); tigecycline, moxifloxacin, and rifampin showed maximal effects of ؊1.1 to ؊1.7 log CFU; and the other antibiotics produced results of ؊0.6 log CFU or less. Addition of thymidine restored intracellular growth of the SCV strain but did not modify the activity of antibiotics (except quinupristin-dalfopristin). All drugs (except tigecycline and oritavancin) showed higher intracellular activity against normal or revertant phenotypes than against SCV strains. The data may help rationalizing the design of further studies with intracellular SCV strains.Small-colony variant (SCV) strains are increasingly recognized as a major cause of the persistence and recurrence of Staphylococcus aureus infections, and specific therapeutic options remain so far ill explored (58). Microbiologically, SCV strains constitute a naturally occurring subpopulation of bacteria with a series of metabolic alterations that confer a particular phenotype characterized by slow growth, reduced hemolytic activity, and auxotrophy for hemin, menadione, or thymidine. SCVs easily revert to the normal phenotype and therefore often escape detection. Moreover, even if stable, they remain difficult to recognize in routine testing unless specifically looked for (42). Genetically, the expression of virulence regulators (agr and sarA) or the alternative stress regulator sigB and its dependent virulence genes (hla and spa) is downregulated in SCV strains compared with isogenic normal strains (26, 38). Clinically, SCV strains are preferentially isolated in chronic infections of skin, soft tissues, joint, and bone (41,59,62), as well as in the respiratory tract of cystic fibrosis (CF) pati...

show abstract

Section: Discussionmentioning

confidence: 99%

Intracellular Activity of Antibiotics in a Model of Human THP-1 Macrophages Infected by a Staphylococcus aureus Small-Colony Variant Strain Isolated from a Cystic Fibrosis Patient: Pharmacodynamic Evaluation and Comparison with Isogenic Normal-Phenotype and Revertant Strains

Nguyen

Denis

Vergison

et al. 2009

Antimicrob Agents Chemother

View full text Add to dashboard Cite

show abstract

“…Thymidine auxotrophs are thought to arise due to antibiotic pressure after prolonged exposure to TMP-SMX (6,7). This has been best described in isolates from the airways of cystic fibrosis patients on chronic TMP-SMX therapy (15,17), but long-term TMP-SMX has also been associated with thymidine auxotrophy in S. aureus isolates from patients without cystic fibrosis (7).…”

mentioning

confidence: 99%

“…Thymidine auxotrophs are generally considered resistant to TMP-SMX due to utilization of extracellular deoxythymidine monophosphate, bypassing the pathway targeted by TMP-SMX (7,15,28). The ideal approach to assessing the antimicrobial susceptibility of thymidine-dependent S. aureus SCVs is unclear.…”

mentioning

confidence: 99%

“…To complicate matters, reversion of thymidine-dependent S. aureus SCVs has been previously described in association with loss of both thymidine auxotrophy and TMP-SMX resistance (7). "False" TMP-SMX susceptibility due to reversion of thyA mutations in the laboratory or the copresence of isolates with and without such mutations and the inability to perform routine susceptibility testing on thymidine-dependent isolates when using automated instruments or following Clinical and Laboratory Standards Institutes guidelines along with a false assumption that S. aureus is generally TMP-SMX susceptible could potentially drive inappropriate TMP-SMX therapy of thymidine-dependent S. aureus.…”

mentioning

confidence: 99%

“…Best described for S. aureus, the purported mechanisms behind their persistence include antimicrobial resistance (4), enhanced biofilm formation (24,25), and the ability to exist for prolonged periods in the intracellular milieu (2,26,28). Conceivably, purulent secretions containing deteriorating cells, the DNA of which can be degraded by S. aureus DNase, present around the LVAD could result in a supply of thymidine, supporting growth of thymidine-dependent S. aureus (7,15,28). Thymidine auxotrophic S. aureus SCVs have been frequently isolated from the lungs of cystic fibrosis patients and (less frequently) from patients with chronic soft tissue infection, tympanitis, bronchitis, peritonitis, and bacteremia (7) but have not been previously reported in association with endocarditis, pacemaker infection, or LVAD infection.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Thymidine Auxotrophic Staphylococcus aureus Small-Colony Variant Endocarditis and Left Ventricular Assist Device Infection

et al. 2012

View full text Add to dashboard Cite

We describe a thymidine-dependent small-colony variant of Staphylococcus aureus associated with left ventricular assist device infection and prosthetic valve and pacemaker endocarditis. CASE REPORTT he patient was a 34-year-old woman who 3 years prior had suffered an anterior wall myocardial infarction resulting in ischemic cardiomyopathy, which necessitated placement of a pacemaker biventricular defibrillator. Subsequently, there was progressive deterioration of cardiac function. A left ventricular assist device (LVAD) was placed as a bridge to heart transplantation. During the same surgery, her native tricuspid valve was replaced with a pericardial tissue valve on account of tricuspid regurgitation. One month after surgery, she developed fever and chills, and blood cultures grew methicillin-resistant Staphylococcus aureus (MRSA) which was susceptible to gentamicin, rifampin, linezolid, trimethoprim-sulfamethoxazole (TMP-SMX), and vancomycin (MIC, 2 g/ml) and resistant to erythromycin and levofloxacin. Trans-esophageal echocardiography (TEE) showed no evidence of endocarditis. She was treated with 6 weeks of vancomycin and rifampin, with gentamicin administered during the first 2 weeks of therapy. Five days after completing antimicrobial therapy, she developed recurrent fevers, and blood cultures again grew MRSA which was susceptible to gentamicin, linezolid, TMP-SMX, vancomycin (MIC, 1 g/ml), and daptomycin and resistant to rifampin, erythromycin, and levofloxacin. A TEE demonstrated vegetations on the pacemaker leads and the prosthetic tricuspid valve. She was treated with daptomycin, gentamicin, and (until the isolate was known to be resistant to rifampin) rifampin. A follow-up TEE after 2 months of antimicrobial therapy showed reduction in the size of the vegetations. She received 5 months of daptomycin and gentamicin; TEE at the end of therapy showed old and healed vegetations. However, over the ensuing year, she had recurrent MRSA bacteremia and soft tissue infection surrounding her LVAD generator site. As a result, from December 2008 through March 2010, she received continuous antimicrobial therapy with various combinations of vancomycin, rifampin, daptomycin, gentamicin, quinupristin-dalfopristin, and TMP-SMX (Fig. 1). During this time, only one isolate (of several) was identifiable, and susceptibility testing was reportable using the BD Phoenix automated microbiology system (BD Diagnostic Systems, Franklin Lakes, NJ). That isolate, recovered from an umbilical driveline aspirate, was reported as susceptible to gentamicin, linezolid, TMP-SMX, and vancomycin (MIC, 2 g/ml), resistant to rifampin, erythromycin, and levofloxacin, and nonsusceptible to daptomycin (MIC, 4 g/ml). Because of inadequate growth in the test medium, other isolates, including bloodstream isolates and another umbilical driveline aspirate, were not identifiable, and susceptibility testing was not reportable using the BD Phoenix automated microbiology system.Despite ongoing combination antimicrobial therapy and incision and drainage of ...

show abstract

Multistep Virtual Screening for Rapid and Efficient Identification of Non‐Nucleoside Bacterial Thymidine Kinase Inhibitors

Zander

Hartenfeller²,

Hähnke³

et al. 2010

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

Antimicrobial activity of trimethoprim/sulfamethoxazole (SXT) against Staphylococcus aureus (S. aureus) is antagonized by thymidine, which is abundant in infected or inflamed human tissue. To restore the antimicrobial activity of SXT in the presence of thymidine, we screened for small-molecule inhibitors of S. aureus thymidine kinase with non-nucleoside scaffolds. We present the successful application of an adaptive virtual screening protocol for novel antibiotics using a combination of ligand- and structure-based approaches. Two consecutive rounds of virtual screening and in vitro testing were performed that resulted in several non-nucleoside hits. The most potent compound exhibits substantial antimicrobial activity against both methicillin-resistant S. aureus strain ATCC 700699 and nonresistant strain ATCC 29213, when combined with SXT in the presence of thymidine. This study demonstrates how virtual screening can be used to guide hit finding in antibacterial screening campaigns with minimal experimental effort.

show abstract

Thymidine-Dependent Staphylococcus aureus Small-Colony Variants: Human Pathogens That Are Relevant Not Only in Cases of Cystic Fibrosis Lung Disease

Cited by 34 publications

References 24 publications

Intracellular Activity of Antibiotics in a Model of Human THP-1 Macrophages Infected by a Staphylococcus aureus Small-Colony Variant Strain Isolated from a Cystic Fibrosis Patient: Pharmacodynamic Evaluation and Comparison with Isogenic Normal-Phenotype and Revertant Strains

Intracellular Activity of Antibiotics in a Model of Human THP-1 Macrophages Infected by a Staphylococcus aureus Small-Colony Variant Strain Isolated from a Cystic Fibrosis Patient: Pharmacodynamic Evaluation and Comparison with Isogenic Normal-Phenotype and Revertant Strains

Thymidine Auxotrophic Staphylococcus aureus Small-Colony Variant Endocarditis and Left Ventricular Assist Device Infection

Multistep Virtual Screening for Rapid and Efficient Identification of Non‐Nucleoside Bacterial Thymidine Kinase Inhibitors

Contact Info

Product

Resources

About