Genotypic versus phenotypic characterization, with respect to susceptibility and identification, of 17 clinical isolates of Staphylococcus lugdunensis

fbl-Typing of Staphylococcus lugdunensis: A Frontline Tool for Epidemiological Studies, but Not Predictive of Fibrinogen Binding Ability

Staphylococcus lugdunensis is increasingly recognized as a potent pathogen, responsible for severe infections with an outcome resembling that of Staphylococcus aureus. Here, we developed and evaluated a tool for S. lugdunensis typing, using DNA sequence analysis of the repeat-encoding region (R-domain) in the gene encoding the fibrinogen (Fg)-binding protein Fbl (fbl-typing). We typed 240 S. lugdunensis isolates from various clinical and geographical origins. The length of the R-domain ranged from 9 to 52 repeats. fbl-typing identified 54 unique 18-bp repeat sequences and 92 distinct fbl-types. The discriminatory power of fbl-typing was higher than that of multilocus sequence typing (MLST) and equivalent to that of tandem repeat sequence typing. fbl-types could assign isolates to MLST clonal complexes with excellent predictive power. The ability to promote adherence to immobilized human Fg was evaluated for 55 isolates chosen to reflect the genetic diversity of the fbl gene. We observed no direct correlation between Fg binding ability and fbl-types. However, the lowest percentage of Fg binding was observed for isolates carrying a 5'-end frameshift mutation of the fbl gene and for those harboring fewer than 43 repeats in the R-domain. qRT-PCR assays for some isolates revealed no correlation between fbl gene expression and Fg binding capacity. In conclusion, this study shows that fbl-typing is a useful tool in S. lugdunensis epidemiology, especially because it is an easy, cost-effective, rapid and portable method (http://fbl-typing.univ-rouen.fr/). The impact of fbl polymorphism on the structure of the protein, its expression on the cell surface and in virulence remains to be determined.

Staphylococcus aureus in Animals

Staphylococcus aureus is a mammalian commensal and opportunistic pathogen that colonizes niches such as skin, nares and diverse mucosal membranes of about 20-30% of the human population. S. aureus can cause a wide spectrum of diseases in humans and both methicillin-sensitive and methicillin-resistant strains are common causes of nosocomial- and community-acquired infections. Despite the prevalence of literature characterising staphylococcal pathogenesis in humans, S. aureus is a major cause of infection and disease in a plethora of animal hosts leading to a significant impact on public health and agriculture. Infections in animals are deleterious to animal health, and animals can act as a reservoir for staphylococcal transmission to humans.Host-switching events between humans and animals and amongst animals are frequent and have been accentuated with the domestication and/or commercialisation of specific animal species. Host-switching is typically followed by subsequent adaptation through acquisition and/or loss of mobile genetic elements such as phages, pathogenicity islands and plasmids as well as further host-specific mutations allowing it to expand into new host populations.In this chapter, we will be giving an overview of S. aureus in animals, how this bacterial species was, and is, being transferred to new host species and the key elements thought to be involved in its adaptation to new ecological host niches. We will also highlight animal hosts as a reservoir for the development and transfer of antimicrobial resistance determinants.

Automated Ribotyping to Distinguish the Different nonSau/ nonSep Staphylococcal Emerging Pathogens in Orthopedic Implant Infections

Several species belonging to Staphylococcus genus, other than Staphylococcus aureus and Staphylococcus epidermidis (nonSau/ nonSep species), exhibit increasing abilities as opportunistic pathogens in the colonisation of periprosthetic tissues. Consequently, the availability of means for accurate identification is crucial to assess the pathogenic characteristics and to clarify clinical relevance of the individual species. Here, 146 clinical staphylococcal isolates belonging to nonSau/ nonSep species from prosthesis-associated orthopedic infections were analyzed by conventional enzymatic galleries and by automated ribotyping. Twelve different species were recognised: S. capitis, S. caprae, S. cohnii, S. equorum, S. haemolyticus, S. hominis, S. lugdunensis, S. pasteuri, S. sciuri, S. simulans, S. warneri, S. xylosus. Ribotype identifications were compared with the phenotypes obtained by the Api 20 Staph system and/or ID 32 Staph system. ID 32 Staph profiles were more consistent with ribotyping results than Api Staph profiles. Across the different staphylococcal species investigated, correct identifications with Api Staph were 45%, while with ID 32 Staph they were 59%. It has, however, to be mentioned that ID 32 Staph was mostly applied to discriminate unmatched ribotyping and Api Staph identifications, thus to a subpopulation of strains with “atypical” metabolic profile. Automated ribotyping provided a correct identification for 91% of the isolates. These results confirm automated ribotyping as a convenient rapid technique, still subject to improvements, which will accurately and rapidly recognise the newly emerging staphylococcal pathogens in implant-related orthopedic infections.

S. lugdunensisNative-Joint Septic Arthritis: Case Report and Review of the Literature

Staphylococcus lugdunensisis a skin commensal classified as a coagulase-negativeStaphylococcus(CoNS). Though CoNS is typically associated with less aggressive clinical disease thanStaphylococcus aureus, there is growing awareness thatS. lugdunensismay be as virulent asS. aureus. The association betweenS. lugdunensisand infective endocarditis is well known, but few reports of native-joint disease with this organism exist. We report a case a 28-year-old male with no prior medical problems presenting with native-joint septic arthritis. Cultures grewS. lugdunensis. To our knowledge, this is the fifth case reported in the literature.

Staphylococcus lugdunensis gluteal abscess in a patient with end stage renal disease on hemodialysis

A 57-year-old end stage renal disease patient on hemodialysis (HD) presented with sepsis secondary to right buttock abscess and overlying cellulitis. She was started on broad-spectrum antibiotic therapy and underwent incision and drainage with marked improvement. Her cultures grew methicillin-resistant Staphylococcus lugdunensis. This bacterium is more virulent than other coagulase negative staphylococci and has been implicated in causing a variety of serious infections but it has been underreported as a cause of skin infections in HD patients and possible other patient populations.

First record of isolation and characterization of methicillin resistant Staphylococcus lugdunensis from clinical samples in Iraq

This study was conducted to determine the frequency of Staphylococcus lugdunensis in different clinical samples. Out of 690 clinical samples, a total of 178 coagulase negative staphylococci (CoNS) isolates were recovered. CoNS were identified as 10 different species; 22 isolates belonged to Staphylococcus lugdunensis. Two specific genes for S. lugdunensis were used (tanA gene and fbl gene) to confirm identification. Both of these specific genes were detected in 15 (68.1%) of 22 isolates that were identified phenotypically. The results of oxacillin MIC showed that 7 of the 15 (46.6%) S. lugdunensis isolates were oxacillin resistant. The antibiotic susceptibility testing against 16 antibiotics showed that resistance rates were variable towards these antibiotics. Eight of fifteen S. lugdunensis isolates (53.3%) were β-lactamase producer. Results of molecular detection of mecA gene found that mecA gene was detected in 6 (40%) of 15 S. lugdunensis. All of these 6 isolates (S1, S2, S3, S4, S5, and S6) were resistant to oxacillin. One isolate (S7) was resistant to oxacillin but mecA was not detected in this isolate. This study is a first record of isolation and characterization of methicillin resistant S. lugdunensis (MRSL) from clinical samples in Iraq.

Prosthetic joint infection

Prosthetic joint infection (PJI) is a tremendous burden for individual patients as well as the global health care industry. While a small minority of joint arthroplasties will become infected, appropriate recognition and management are critical to preserve or restore adequate function and prevent excess morbidity. In this review, we describe the reported risk factors for and clinical manifestations of PJI. We discuss the pathogenesis of PJI and the numerous microorganisms that can cause this devastating infection. The recently proposed consensus definitions of PJI and approaches to accurate diagnosis are reviewed in detail. An overview of the treatment and prevention of this challenging condition is provided.

Reprint of "Identification of staphylococcal species based on variations in protein sequences (mass spectrometry) and DNA sequence (sodA microarray)"

This report is among the first using sequence variation in newly discovered protein markers for staphylococcal (or indeed any other bacterial) speciation. Variation, at the DNA sequence level, in the sodA gene (commonly used for staphylococcal speciation) provided excellent correlation. Relatedness among strains was also assessed using protein profiling using microcapillary electrophoresis and pulsed field electrophoresis. A total of 64 strains were analyzed including reference strains representing the 11 staphylococcal species most commonly isolated from man (Staphylococcus aureus and 10 coagulase negative species [CoNS]). Matrix assisted time of flight ionization/ionization mass spectrometry (MALDI TOF MS) and liquid chromatography-electrospray ionization tandem mass spectrometry (LC ESI MS/MS) were used for peptide analysis of proteins isolated from gel bands. Comparison of experimental spectra of unknowns versus spectra of peptides derived from reference strains allowed bacterial identification after MALDI TOF MS analysis. After LC-MS/MS analysis of gel bands bacterial speciation was performed by comparing experimental spectra versus virtual spectra using the software X!Tandem. Finally LC-MS/MS was performed on whole proteomes and data analysis also employing X!tandem. Aconitate hydratase and oxoglutarate dehydrogenase served as marker proteins on focused analysis after gel separation. Alternatively on full proteomics analysis elongation factor Tu generally provided the highest confidence in staphylococcal speciation.

Identification of staphylococcal species based on variations in protein sequences (mass spectrometry) and DNA sequence (sodA microarray)

This report is among the first using sequence variation in newly discovered protein markers for staphylococcal (or indeed any other bacterial) speciation. Variation, at the DNA sequence level, in the sodA gene (commonly used for staphylococcal speciation) provided excellent correlation. Relatedness among strains was also assessed using protein profiling using microcapillary electrophoresis and pulsed field electrophoresis. A total of 64 strains were analyzed including reference strains representing the 11 staphylococcal species most commonly isolated from man (Staphylococcus aureus and 10 coagulase negative species [CoNS]). Matrix assisted time of flight ionization/ionization mass spectrometry (MALDI TOF MS) and liquid chromatography-electrospray ionization tandem mass spectrometry (LC ESI MS/MS) were used for peptide analysis of proteins isolated from gel bands. Comparison of experimental spectra of unknowns versus spectra of peptides derived from reference strains allowed bacterial identification after MALDI TOF MS analysis. After LC-MS/MS analysis of gel bands bacterial speciation was performed by comparing experimental spectra versus virtual spectra using the software X!Tandem. Finally LC-MS/MS was performed on whole proteomes and data analysis also employing X!tandem. Aconitate hydratase and oxoglutarate dehydrogenase served as marker proteins on focused analysis after gel separation. Alternatively on full proteomics analysis elongation factor Tu generally provided the highest confidence in staphylococcal speciation.

Staphylococcus Lugdunensis, An Aggressive Coagulase-Negative Pathogen not to be Underestimated

The new emerging coagulase-negative pathogen Staphylococcus lugdunensis is responsible for severe cardiac and joint infections. Since the biochemical phenotypic systems designed for the identification of CoNS do not appear to be species specific and are hardly reliable for the discrimination of S. lugdunensis from other staphylococci, its precise identification requires fine molecular methods. The pathogenic mechanisms by which S. lugdunensis causes severe infections are not yet completely elucidated and in this review its virulence and toxic determinants are surveyed as well as its adhesins and biofilm production.

Staphylococcus lugdunensis: the coagulase-negative staphylococcus you don't want to ignore

Staphylococcus lugdunensis is a virulent coagulase-negative staphylococcus (CoNS) that behaves like Staphylococcus aureus. Toxic shock syndrome, osteomyelitis, septic arthritis and postoperative endopthalmitis have been observed. Endocarditis complicated by heart failure, periannular abscess formation and embolic phenomenon have brought particular attention to this CoNS. Mortality rates for endocarditis appear higher when compared with other CoNS. Owing to the laboratory methods used, identification may be misleading. β-lactam antimicrobials are recommended pending sensitivities. Evaluation for endocarditis should be pursued in bacteremic patients due to its pathogenic potential.

Successful treatment of sepsis caused by Staphylococcus lugdunensis in an adult with 22q11.2 deletion syndrome

A 27-year-old woman visited our hospital because of high fever. She had been diagnosed as 22q11.2 deletion syndrome (22q11.2DS) due to her cardiac history (tetralogy of Fallot), thymic hypoplasia and 22q11.2 deletion. She had a normal CD4/CD8 ratio, a slightly decreased lymphocyte count and normal serum immunoglobulin levels. Blood cultures were positive for Staphylococcus lugdunensis (S. lugdunensis). Infection route of S. lugdunensis in this case was unclear. The patient was successfully treated with several intravenous antibiotics. Infection should be considered when managing patients with 22q.11.2DS. regardless of whether their immune system is impaired.

Clinical and microbiological characteristics of community-acquired Staphylococcus lugdunensis infections in Southern Taiwan

Most Staphylococcus lugdunensis strains (49/59, 83%) were related to clinical infections, were susceptible to most antimicrobial agents with an overall oxacillin-resistant rate of 5% (3/58), and carried relatively great genetic diversity. Community-acquired infections (41/49, 84%) were dominant, often developed in patients with comorbidity, and had rather benign clinical courses without mortality.

Occurrence of genes of putative fibrinogen binding proteins and hemolysins, as well as of their phenotypic correlates in isolates of S. lugdunensis of different origins

Background

Staphylococcus lugdunensis is an important human pathogen that causes potentially fatal endocarditis, osteomyelitis and skin and soft tissue infections similar to diseases caused by Staphylococcus aureus. Nevertheless, in contrast to S. aureus, data on pathogenicity factors of S. lugdunensis is scarce. Two adhesins, a fibrinogen and a von Willebrand factor binding protein, and a S. lugdunensis synergistic hemolysin (SLUSH) have been previously described. Moreover, the newly sequenced genome of S. lugdunensis revealed genes of other putative fibrinogen binding adhesins and hemolysins. The aim of this study was to gain more insight into the occurrence of genes likely coding for fibrinogen binding adhesins and hemolysins using clinical strains of S. lugdunensis.

Findings

Most of the putative adhesin genes and hemolysin genes investigated in this study were highly prevalent, except for the SLUSH gene cluster. In contrast to previous reports, binding to fibrinogen was detected in 29.3% of the S. lugdunensis strains. In most strains, hemolysis on blood agar plates was weak after 24 h and distinct after 48 h of incubation. The fibrinogen binding and hemolysis phenotypes were also independent of the type of clinical specimen, from which the isolates were obtained.

Conclusion

In this study we described a pyrrolidonyl arylamidase negative S. lugdunensis isolate. Our data indicate that a matrix-assisted laser desorption ionisation time-of-flight MS-based identification of S. lugdunensis or species-specific PCR's should be performed in favour of pyrrolidonyl arylamidase testing. In contrast to the high occurrence of putative fibrinogen binding protein genes, 29.3% of the S. lugdunensis strains bound to fibrinogen. Putative hemolysin genes were also prevalent in most of the S. lugdunensis strains, irrespective of their hemolysis activity on Columbia blood agar plates. Similar to a previous report, hemolysis after 48 h of incubation is also indicative for S. lugdunensis. The SLUSH gene cluster was detected in an estimated 50% of the strains, indicating that this locus is different or non-prevalent in many strains.

fbl gene as a species-specific target for Staphylococcus lugdunensis identification

Staphylococcus lugdunensis is an unusually virulent coagulase-negative species, associated with severe infections. The present report describes the development of a single-step, species-specific PCR protocol for S. lugdunensis identification. fbl gene, encoding a fibrinogen-binding adhesin, was exploited and assessed as a suitable nucleic acid target. The gene was detected in all 17 S. lugdunensis isolates examined, while no amplification product was obtained from 98 isolates representing 11 staphylococcal and 17 nonstaphylococcal species. Forty-seven percent of the S. lugdunensis strains produced a positive slide coagulase reaction, which is consistent with varying levels of Fbl protein expression within the species.

[Evaluation of methods for studying susceptibility to oxacillin and penicillin in 60 Staphylococcus lugdunensis isolates]

INTRODUCTION

Staphylococcus lugdunensis is a coagulase-negative staphylococcus associated with a variety of clinical infections. In this paper we present the results of a comparative study using 4 methods to determine antimicrobial susceptibility to oxacillin and penicillin in 60 S. lugdunensis isolates.

MATERIAL AND METHODS

We studied 60 S. lugdunensis isolates obtained from clinical specimens sent to our laboratory over an 8-year period. All isolates were free coagulase-negative and DNase-negative, and biochemically identified by API ID 32 STAPH (bioMérieux). Presence of mecA and ss-lactamase production were studied in all cases. Antimicrobial susceptibility was determined by the Vitek 2 System (bioMérieux) and broth microdilution (Wider) (Soria Melguizo) for penicillin and oxacillin, and the E-test (AB Biodisk) and cefoxitin disk diffusion test (BD BBLTM) for oxacillin.

RESULTS

All isolates lacked the mecA gene and were susceptible to oxacillin by broth microdilution, E-test, and cefoxitin disk diffusion test. Only two isolates were oxacillin-resistant by the Vitek 2 System. Twenty-four isolates (40%) were ss-lactamase-positive, 4 after induction. Susceptibility testing to penicillin determined that 48 isolates showed concordance between the results obtained by broth microdilution and Vitek 2, but 12 isolates (20%), showed divergent results.

CONCLUSIONS

We detected no resistance to oxacillin in S. lugdunensis. All the methods evaluated were adequate for determining oxacillin resistance. The Vitek 2 System is useful for detecting penicillin resistance, but the ss-lactamase test should be applied to isolates with a MIC=0.25microg/ml to avoid the interpretation of false resistance to this antibiotic.

[Detection of mecA in strains with oxacillin and cefoxitin disk tests for detection of methicillin-resistant Staphylococcus]

BACKGROUND

Cinical and Laboratory Standards Institute (CLSI) recommends the use of cefoxitin disks instead of long-used oxacillin disks for screening methicillin-resistant isolates of staphylococci. The frequency of discrepant results and accuracy of the tests were evaluated by detecting mecA gene.

METHODS

A total of 3,123 Stapylococci isolates from patients in Severance Hospital were tested during September 2005 to August 2006 by the CLSI-recommended test using both cefoxitin and oxacillin disks. The mecA gene was detected by PCR and the oxacillin minimum inhibitory concentration (MIC) was determined by using agar dilution method for the isolates with discrepant tests.

RESULTS

Among 1,915 S. aureus islolates tested, one isolate was resistant to oxacillin disk but susceptible to cefoxitin disk; the isolate did not have mecA gene. Another isolate susceptible to oxacillin but resistant to cefoxitin had mecA gene. Among 1,208 coagulase-negative staphylococcal isolates, 15 isolates were resistant to oxacillin disk but susceptible to cefoxitin disk; the isolates did not have mecA genes. Two isolates susceptible to oxacillin disk but resistant to cefoxitin disk had mecA genes. Among the 16 Staphylococcus isolates that did not have mecA gene, 15 isolates had the oxacillin MICs of </= 2 microg/mL and were considered as methicillin-susceptible, while 1 isolate with the MIC of 4 microg/mL was considered as methicillin-resistant.

CONCLUSIONS

Overall, 1.9% of staphylococcal isolates showed discrepant results when the screening tests were performed by using oxacillin and cefoxitin disks. None of the isolates resistant to oxacillin disk but susceptible to cefoxitin disk had mecA gene. In conclusion, the cefoxitin disk test is more reliable than oxacillin disk test in screening methicillin-resistant staphylococcal isolates.

Significance of Staphylococcus lugdunensis bacteremia: report of 28 cases and review of the literature

BACKGROUND

Staphylococcus lugdunensis endocarditis has been associated with an aggressive course. The aim of this study was to determine factors associated with the development of endocarditis in patients with S. lugdunensis bacteremia.

METHODS

A retrospective analysis of all patients with S. lugdunensis bacteremia in three tertiary care centers in Switzerland was performed. Data regarding medical history, symptoms, and susceptibility of S. lugdunensis isolates were collected. Our results were reviewed in the context of the current literature.

RESULTS

A total of 28 patients with S. lugdunensis bacteremia were identified. Of the 13 patients with endocarditis, all were community acquired. Cardiac surgery was performed in 85% of these patients; mortality was 23%, reflecting the aggressive course of this disease. In contrast, in the 15 patients without endocarditis, no complications associated with S. lugdunensis bacteremia were observed. In 73%, a probable source was identified in the form of a venous catheter or other foreign device. Only three of these episodes were community acquired. No difference was observed in susceptibility of the S. lugdunensis isolates to penicillin, which was 77% in endocarditis isolates, and 87% in isolates of bacteremia without endocarditis, respectively.

CONCLUSION

S. lugdunensis bacteremia is associated with endocarditis in up to 50% of patients. Every patient with community-acquired S. lugdunensis bacteremia should be carefully examined for signs of endocarditis. Once S. lugdunensis endocarditis is diagnosed, close monitoring is essential and surgical treatment should be considered early. In the nosocomial setting, endocarditis is far less frequent, and S. lugdunensis bacteremia is usually associated with a catheter or other foreign materials.

Microbiological characteristics, presumptive identification, and antibiotic susceptibilities of Staphylococcus lugdunensis

This study validated abbreviated methods for the presumptive identification of Staphylococcus lugdunensis and studied the antibiotic susceptibilities of 106 isolates. The combination of positive responses to ornithine and pyrrolidonyl arylamidase identified all S. lugdunensis isolates. Resistance to penicillin and methicillin was detected in 27 and 5% of isolates, respectively.

From clinical microbiology to infection pathogenesis: how daring to be different works for Staphylococcus lugdunensis

Staphylococcus lugdunensis has gained recognition as an atypically virulent pathogen with a unique microbiological and clinical profile. S. lugdunensis is coagulase negative due to the lack of production of secreted coagulase, but a membrane-bound form of the enzyme present in some isolates can result in misidentification of the organism as Staphylococcus aureus in the clinical microbiology laboratory. S. lugdunensis is a skin commensal and an infrequent pathogen compared to S. aureus and S. epidermidis, but clinically, infections caused by this organism resemble those caused by S. aureus rather than those caused by other coagulase-negative staphylococci. S. lugdunensis can cause acute and highly destructive cases of native valve endocarditis that often require surgical treatment in addition to antimicrobial therapy. Other types of S. lugdunensis infections include abscess and wound infection, urinary tract infection, and infection of intravascular catheters and other implanted medical devices. S. lugdunensis is generally susceptible to antimicrobial agents and shares CLSI antimicrobial susceptibility breakpoints with S. aureus. Virulence factors contributing to this organism's heightened pathogenicity remain largely unknown. Those characterized to date suggest that the organism has the ability to bind to and interact with host cells and to form biofilms on host tissues or prosthetic surfaces.

Comparison of two commercial methods with PCR restriction fragment length polymorphism of the tuf gene in the identification of coagulase-negative staphylococci

AIMS

Two commercial methods for the identification of coagulase-negative staphylococci (CNS) were compared with the restriction fragment length polymorphism (RFLP) of the amplified tuf gene, which served as the reference method.

METHODS AND RESULTS

One hundred and forty-five CNS were evaluated using the API 32 Staph ID and the Crystal GP/ID BBL systems. The PCR-RFLP of the tuf gene served as the reference method. The APIStaph and the GP/ID BBL had an overall rate of agreement with the molecular method of 58.6% and 46.2% respectively, with the inability of the GP/ID BBL to characterize 11.7% of the isolates. The APIStaph showed higher sensitivity and better agreement than the GP/ID BBL with the PCR-RFLP, except for Staphylococcus hominis and Staphylococcus capitis.

CONCLUSIONS

Neither of the commercial systems was as reliable as the PCR-RFLP method for identifying isolates of CNS. Overall the APIStaph had better agreement with the PCR-RFLP than the GP/ID system.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results indicate that the PCR-RFLP method is more reliable than the two commercial systems tested, suggesting that it is more reliable for routinely identifying CNS.

In vitro effects of antimicrobial agents on planktonic and biofilm forms of Staphylococcus lugdunensis clinical isolates

Staphylococcus lugdunensis is an atypically virulent coagulase-negative staphylococcal species associated with acute and destructive infections that often resemble Staphylococcus aureus infections. Several types of infection caused by S. lugdunensis (e.g., native valve endocarditis, prosthetic joint infection, and intravascular catheter infection) are associated with biofilm formation, which may lead to an inability to eradicate the infection due to the intrinsic nature of biofilms to resist high levels of antibiotics. In this study, planktonic MICs and MBCs and biofilm bactericidal concentrations of 10 antistaphylococcal antimicrobial agents were measured for 15 S. lugdunensis isolates collected from patients with endocarditis, medical device infections, or skin and soft tissue infections. Planktonic isolates were susceptible to all agents studied, but biofilms were resistant to high concentrations of most of the drugs. However, moxifloxacin was able to kill 73% of isolates growing in biofilms at </=0.5 mug/ml. Relative to the effect on cell density, subinhibitory concentrations of nafcillin substantially stimulated biofilm formation of most isolates, whereas tetracycline and linezolid significantly decreased biofilm formation in 93 and 80% of isolates, respectively. An unexpected outcome of MBC testing was the observation that vancomycin was not bactericidal against 93% of S. lugdunensis isolates, suggesting widespread vancomycin tolerance in this species. These data provide insights into the response of S. lugdunensis isolates when challenged with various levels of antimicrobial agents in clinical use.