Microbiologic Profile of Staphylococci Isolated from Osteoarticular Infections: Evolution over Ten Years

Abstract

Background:

Staphylococci, especially coagulase-negative staphylococci (CoNS) represent the most frequent micro-organism associated with osteoarticular infections (OAIs), especially those involving orthopedic devices. The antibiotic susceptibility profile of the bacteria mostly responsible for OAIs is therefore crucial information for choosing the appropriate antibiotic regimen administered during the removal procedure until the first results of the conventional culture.

Methods:

The antibiotic susceptibility profile of staphylococci isolated from OAIs in a referent center for osteoarticular infection was studied over a 10-y period to adapt antibiotic protocols to the ecology.

Results:

From 2002 to 2011, the resistance of Staphylococcus aureus to methicillin and rifampicin decreased (27.9% versus 20.6% and 13% versus 1%, respectively); the resistance to fluoroquinolones (FQ) was stable (24% on average), and all the isolates were susceptible to glycopeptides. For CoNS, the resistance to methicillin, rifampicin, and FQ increased (30.4% versus 43.9%, 13% versus 18.5%, and 20.3% versus 34.1%, respectively) over the same period. Resistance of the CoNS to vancomycin was observed in 2011 for the first time (2.3%), and 3.8% were resistant to teicoplanin in 2002 compared with 22% in 2011, with 3.5% resistant to linezolid in 2011.

Conclusion:

The sensibility of bacteria over 10 y remained stable, except for CoNS. The increase of the resistances for CoNS led us to exclude teicoplanin from the first-line empiric antibiotic treatment, to avoid linezolid, and to prefer vancomycin or daptomycin.

Most micro-organisms can be responsible for an osteoarticular infection (OAI), but bacteria, especially staphylococci, are the leading cause of these infections. Microbiology of OAIs depends on the type of infections: Hematogenous (secondary to bacteriemia) or from contiguous infection or from direct inoculation (e.g., post-trauma or fracture), with or without orthopedic device, acute (duration of the symptoms of infection ≤2 wks) or chronic (duration of the symptoms of infection >2 wks). Micro-organisms with high virulence such as Staphylococcus aureus, β-hemolytic streptococci, or gram-negative bacilli are more prevalent in acute infection (hematogenous osteomyelitis or in early post-operative infections with an orthopedic implant). Less virulent bacterial strains and micro-organisms belonging to the commensal skin flora such as coagulase-negative staphylococci (CoNS) are more prevalent in case of chronic infection especially with a orthopedic device in situ [1].

Among staphylococci, S. aureus is the leading cause of hematogenous OAI, especially in young people, whereas CoNS, specifically S. epidermidis, are responsible for OAI involving orthopedic devices. The major complication of prosthetic surgery (hip and knee) is the infection of the implanted device, which occurs in 1% to 3% of procedures [2,3]. Gram-positive cocci, especially Staphylococcus spp., account for two-thirds of cases (30%–43% for CoNS and 12%–23% for S. aureus) [3,4]. In the University Hospital Center of Lille, these infections have been managed by a multidisciplinary team (surgeons, infectious disease specialists, and microbiologists) for more than 10 y, with strict antimicrobial protocols including high dosages of broad-spectrum antibiotics administrated until bacteriologic results become available. However, this protocol might have negative effects on the bacterial ecology particularly with regard to the selection of resistant bacterial strains. The aim of the present retrospective study was to follow the profile of bacterial susceptibility over 10 y, with a focus on the Staphylococcus genus.

Patients and Methods

A single-center observational retrospective study was conducted in the Lille University Hospital orthopedic unit (Lille, France), acting as a national reference center for osteoarticular infection (CRIOAC) of Northern France. This 17-bed unit manages patients requiring orthopedic surgery to manage infections.

Antibiotic protocols

In this unit, patients received empiric antibiotic therapy immediately after surgical samples were taken. This treatment associated an antimicrobial agent with an activity against methicillin-resistant staphylococci (vancomycin, teicoplanin, or linezolid) and a third- or fourth-generation cephalosporin or aztreonam. This probabilistic therapy was maintained until intra-operative microbiologic results were available. Antibiotic therapy was then modified and adapted to the micro-organisms found in surgical samples.

Data collection

All staphylococci were derived from positive cultures of intra-operative samples performed in the orthopedic unit from patients hospitalized for OAI.

All S. aureus isolated from one or more samples were included in the study. Only coagulase-negative staphylococci isolated from two or more samples (same genus and species and common antibiogram) were included in the study [5]. Microbiologic data were collected retrospectively from the laboratory computerized system (Molis V3 and V4, Vision4health, Paris, France) from January 2002 to December 2011.

Conventional Microbiology

Intra-operative specimens (bone, tissue, joint biopsy, or joint fluid) were analyzed microbiologically as described previously [6]. Staphylococci were identified by VITEK cards (bioMérieux S.A., Marcy l'Etoile, France) from 2002 to 2008, and by matrix-assisted laser desorption ionization-time of flight mass spectrometry (Microflex Biotyper 2.0, Bruker Daltonics GmbH, Bremen, Germany) according to the manufacturer's instructions (software version 3.1.1.0) since 2008. In case of failure of the conventional methods, identification was realized by sodA sequencing [7].

The antimicrobial susceptibility testing was performed with VITEK-2 AST card (bioMérieux S.A., Marcy l'Etoile, France) according to published recommendations (www.sfm-microbiologie.org): The results for oxacillin and cefoxitin obtained from the automated system were used to detect methicillin-resistance in Staphylococcus spp. In case of doubtful result, the research of mecA gene was performed by amplification of the mecA gene by polymerase chain reaction (PCR) as described by Ünal et al. [8].

Statistical analysis

The statistical analysis was based on a comparison of averages by means of the of the χ² test. The significance level was established at 0.01.

Results

Prevalence of bacterial pathogens isolated from OAI over the 10-y period

Data were collected on staphylococcal isolates between 2002 and 2011, when at least one antimicrobial susceptibility test was performed. A total of 5,006 non-duplicate clinical isolates was included retrospectively between January 2002 and December 2011: 2,876 staphylococci (57.4%), 649 Enterococcus or Streptococcus (13%), 614 Enterobacteriaceae (12.2%), 252 non-fermenting gram-negative bacilli (5.1%), 185 gram-positive bacilli (3.7%), and 399 anaerobes (7.9%) (Fig. 1).

FIG. 1.

Distribution of strains isolated from osteoarticular infections in the period 2002–2011.

The distribution of the different isolates remained stable during the period of the study for each year. The only statistically significant difference emerging from this analysis concerned Propionibacterium acnes, which increased from 8 isolates in 2002 to 32 isolates in 2011 (χ², p=0.0001).

Staphylococcus aureus

Among the 2,876 staphylococci isolated over 10 y, a total of 950 S. aureus (33% of all staphylococcal strains) was isolated. The distribution remained stable with on average 95 strains of S. aureus isolated each year (n=122, n=81, n=82, n=73, n=83, n=94, n=90, n=114, n=114, n=97 from 2001 to 2011, respectively). For S. aureus, almost all isolates were resistant to penicillin G (90.1% in 2002 versus 91.8% in 2011). Methicillin resistant S. aureus (MRSA), thereby resistant to all β-lactam antibiotics, remained unchanged over the 10-y period: 27.9% in 2002 versus 20.6% in 2011 (P=NS). At the same time, gentamicin resistance was higher in 2002 (9.8%) than in 2011 (1%; NS). Macrolides resistance was unchanged during the study period, with 23.7% of isolates resistant to erythromycin in 2011 (versus 36.9% in 2002; NS), and 7.2% resistant to lincomycin in 2011 (versus 19.2% in 2002; NS). Resistance to trimethoprim-sulfamethoxazole (TMP-SMX), to fluoroquinolones, to rifampicin were unchanged (10.6% versus 3.1% [NS], 37% versus 17.7% [NS]), but decreased for 13.1% versus 1% (χ², p=0.006), but not for fostomycin (6.6% versus 1% [NS]) from 2002 to 2011, respectively. Fusidic acid resistance remained stable (14.8% and 14.4% in 2002 and 2011, respectively). Tetracyclines averaged approximately 95% susceptibility for all years (only 6.2% and 2.1% of isolates resistant to tetracycline Hcl and minocycline, respectively, in 2011). Neither glycopeptide resistance (teicoplanin or vancomycin), nor linezolid resistance were detected during the period of the study (Fig. 2). Among MRSA isolates, the rate of multi-drug resistance decreased (NS) between 2002 and 2011: the majority of MRSA were susceptible to gentamycin, TMP-SMX and rifampicin, but resistant to fluoroquinolones in 2011 (Table 1).

FIG. 2.

Resistance of Staphylococcus aureus isolated from osteoarticular infections in the period 2002–2011. I=intermediate; R=resistant; P=benzylpenicillin; iMETI=methicillin; GM=gentamicin; TE=tetracycline; MNO=minocycline; E=erythromycin; L=lincomycin; SXT=trimethoprim-sulfamethoxazole; FQ=fluoroquinolones; RA=rifampicin; FA=fusidic acid; FOS=fosfomycin; VA=vancomycin; TEC=teicoplanin; LZD=linezolid.

Table 1.

Evolution of Co-Resistance in Methicillin-Resistant Staphylococcus aureus and Methicillin-Resistant Coagulase-Negative Staphylococci, 2002 versus 2011

	% of isolates I+R
	MRSA		MRCoNS
	2002	2011	2002	2011
Gentamicin	23%	4%	52%	67%
Erythromycin	50%	42%	69%	74%
Trimethoprim-sulfamethoxazole	20%	4%	47%	42%
Fluoroquinolones	68%	83%	57%	71%
Rifampicin	53%	4%	37%	34%
Fosfomycin	13%	13%	43%	36%

I=intermediate, R=resistant; MRSA=methicillin-resistant Staphylococcus aureus; MRCoNS=methicillin-resistant coagulase-negative staphylococci.

Coagulase-negative staphylococci

Among the 2,876 staphylococci isolated over the 10-y period, a total of 1,926 CoNS strains (67%) were recovered intra-operatively: 1,115 S. epidermidis strains (58%), 179 S. capitis (9.3%), 109 S. warneri (5.7%), 76 S. lugdunensis (3.9%), 62 S. hominis (3.2%), 56 S. haemolyticus (2.9%), 53 S. simulans (2.8%) 21 S. caprae (1.1%), and others species (Table 2). In 2002, more than 50% of CoNS were not identified to the species level, but since the use of VITEK2 and MALDI-TOF, almost all CoNS have been identified completely: in 2011 more than 60% of CoNS (n=159) were identified as S. epidermidis versus 12.1% in 2002. Most strains were resistant to penicillin G (70.2% in 2002, 79.8% in 2011). The resistance to methicillin increased over the 10-y period (30.4% in 2002 versus 43.9% in 2011; χ², p=0.004). At the same time, resistance to gentamicin was two times higher between 2002 (17.5%) and 2011 (30.6%; χ², p=0.002). Regarding the macrolides, the resistance was stable (48.8% versus 50.9% for erythromycin and 18.6% versus 16% for lincomycin in 2002 and 2011, respectively). Regarding resistance to TMP-SMX (18.3% in 2002 versus 19.7% in 2011), to fluoroquinolones (20.3% in 2002 versus 34.1% in 2011), to rifampicin (13% in 2002 versus 18.5% in 2011), to fusidic acid (43.5% in 2002 versus 48% in 2011), and to fosfomycin (39.4% in 2002 versus 37.6% in 2011), no significant differences were observed during the study period (Fig. 3). Approximately 40% of strains were resistant to tetracycline whereas less than 4% of strains were resistant to minocycline. Finally, strains resistant to glycopeptides appeared during the study period: in 2002, there was one strain resistant to vancomycin (0.4%), eight strains intermediate to teicoplanin (3.3%) and one resistant to teicoplanin (0.4%); in 2011, four strains were resistant to vancomycin (2.3%), nine intermediate to teicoplanin (5.2%), and 29 resistant to teicoplanin (16.8%). The prevalence of decreased susceptibility (intermediate or resistant) to teicoplanin increased throughout the study: 3.7% in 2002, 14.9% in 2008, 21.2% in 2009, 19.7% in 2010 and 22% in 2011 (χ², p<0.0001). Linezolid resistance also appeared during the study from 0.8% in 2003 to 3.5% in 2011 (NS) (Table 3). Among methicillin-resistant CoNS (MRCoNS) isolates, the rate of multi-drug resistance remained stable between 2002 and 2011: the majority of MRCoNS were multi-drug resistant with one-third resistant to rifampicin and one-half resistant to TMP-SMX in 2011 (Table 1).

FIG. 3.

Resistance of coagulase-negative staphyloccocci isolated from osteoarticular infections in the period 2002–2011. I=intermediate; R=resistant; P=benzylpenicillin; METI=methicillin; GM=gentamicin; TE=tetracycline; MNO=minocycline; E=erythromycin; L=lincomycin; SXT=trimethoprim-sulfamethoxazole; FQ=fluoroquinolones; RA=rifampicin; FA=fusidic acid; FOS=fosfomycin; VA=vancomycin; TEC=teicoplanin; LZD=linezolid.

Table 2.

Resistance of Coagulase-Negative Staphyloccocci Isolated from Osteoarticular Infections in the Period 2002–2011

	n of isolates by year										Total by species
Microorganims	2002	2003	2004	2005	2006	2007	2008	2009	2010	2011	n	%
S. kloosii	0	0	1	0	0	0	0	0	0	0	1	0.05%
S. saccharolyticus	0	0	0	0	0	0	1	1	0	0	2	0.10%
S. pasteuri	0	0	0	1	0	0	0	0	0	1	2	0.10%
S. auricularis	2	0	0	1	0	0	0	0	0	0	3	0.16%
S. schleiferi	1	0	1	1	0	0	0	0	0	0	3	0.16%
S. xylosus	0	0	0	0	2	1	1	0	0	0	4	0.21%
S. saprophyticus	0	0	0	2	1	1	0	0	0	1	5	0.26%
S. chromogenes	0	4	1	0	0	0	0	0	0	0	5	0.26%
S. intermedius	0	2	0	1	0	2	0	1	2	0	8	0.42%
S. pettenkoferi	0	0	0	2	0	1	0	2	4	2	11	0.57%
S. cohnii	1	4	4	2	1	0	2	0	2	1	17	0.88%
S. caprae	0	2	1	0	4	2	4	1	2	5	21	1.09%
S. simulans	1	5	2	5	7	8	10	4	4	7	53	2.76%
S. haemolyticus	4	5	4	8	4	8	3	7	4	9	56	2.91%
S. hominis	2	4	9	3	8	6	14	3	5	8	62	3.22%
S. lugdunensis	0	7	9	6	9	17	6	9	4	9	76	3.95%
S. warneri	7	13	14	13	22	16	5	6	5	8	109	5.67%
S. capitis	10	17	11	22	20	18	16	22	29	14	179	9.31%
CoNS	159	5	7	9	2	5	2	4	1	0	194	10.09%
S. epidermidis	60	116	123	132	122	110	111	91	142	108	1,115	57.98%
Total by year	247	184	187	208	202	195	175	151	204	173	1926

CoNS=coagulase-negative staphylococci.

Table 3.

Evolution of Resistance of Glycopeptides and Linezolid in Coagulase-Negative Staphylococci during the Study Period

	2002 n (%)		2003 n (%)		2004 n (%)		2005 n (%)		2006 n (%)		2007 n (%)		2008 n (%)		2009 n (%)		2010 n (%)		2011 n (%)
	I	R	I	R	I	R	I	R	I	R	I	R	I	R	I	R	I	R	I	R
Vancomycin	1 (0.4%)	0	0	0	0	0	0	0	0	0	1 (0.5%)	0	0	0	0	0	0	0	0	4 (2.3%)
Teicoplanin	8 (3.3%)	1 (0.4%)	10 (5.4%)	0	33 (17.6%)	2 (1.1%)	38 (18.3%)	8 (3.8%)	28 (13.9%)	1 (0.5%)	25 (12.8%)	0	22 (12.6%)	4 (2.3%)	27 (17.9%)	5 (3.3%)	25 (12.3%)	15 (7.4%)	9 (5.2%)	29 (16.8%)
Linezolid	nt	nt	0	1 (0.8%)	0	0	0	0	0	0	0	0	0	2 (1.1%)	0	3 (2%)	0	2 (1%)	0	6 (3.5%)

I=intermediate; R=resistant; nt=not tested.

Discussion

Surgery and antibiotic treatment are the cornerstones of the eradication of bone and joint infections [3,4,9]. Various surgical treatment modalities may be observed according to the type and severity of the infection and the patient's general health. But in all these cases, the outcome is generally correlated with the efficiency of the anti-microbial therapy introduced in the perioperative period [9]. Bacterial resistance profile to antibiotics is an important point in the choice of the first-line empirical antibiotic regimen introduced during surgery [10,11].

Staphylococcus spp. is the bacterial genus involved in more than 60% of OAIs managed at the Lille University Hospital and the coagulase negative species remain the major cause of these infections, particularly in prosthetic joint infections (PJIs) in accordance with previous published series [10 –13]. This study describes the evolution of resistance trends for 2,876 staphylococcal strains isolated from osteoarticular samples in our center for the last 10 y. These samples were collected during surgery of bone and joint infection with or without orthopedic device. From this point of view, this study is in contrast to many others focused on prosthetic infections [10 –15].

Methicillin resistance is the main diagnostic challenge to optimize management of OAIs and is associated with a higher risk of treatment failure [16,17] and a substantial economic impact [18]. For the last decade, the prevalence of MRSA strains decreased from 27.9% to 20.6% corresponding to a general phenomenon in most European countries [19]. Moreover, S. aureus strains became more susceptible to fluoroquinolones and rifampicin between 2002 and 2011 in our center. This tendency is probably caused by the limitation in the prescription of these molecules restricted to infectious disease specialists of the center. However, S. aureus represents only 34% of all staphylococci species isolated each year.

Coangular-negative staphylococci are the most common organisms isolated from osteoarticular samples, and treatment of CoNS infections becomes increasingly difficult because of the high prevalence of resistant strains [20]. Moreover, S. epidermidis is the main species involved in these infections, accounting for 57.9% of all CoNS isolates. Staphylococcus epidermidis is well known for complicating orthopedic device infections because of its ability to form biofilm on the surface of the implant. This virulence factor along with antimicrobial resistance has a huge impact on the therapy of these infections. In contrast to S. aureus, the proportion of MRCoNS significantly increased, exceeding 40% in 2011. This rate is comparable to that observed by Tsuyakama et al. [13] (48%) but lower than that of Hellmark et al. [14] (85%).

These observations led us to use glycopeptides as first-line empiric treatment until culture results become available. Indeed, as described previously by Biavasco et al. [21], a significant increase of glycopeptide resistance is observed, raising 22% of the CoNS for teicoplanin in 2011. Cremniter et al. [22] reported a prevalence of 5.1% of CoNS with decreased susceptibility to teicoplanin in orthopedic device-associated infections. Adverse effects of glycopeptides are well known, such as slow bactericidal activity, lower activity against methicillin-susceptible strains, and potential toxicity directly proportional to duration of therapy and high serum concentrations [23,24]. Based on this, linezolid appears to be an option in OAIs because of its good activity against methicillin-resistant strains without nephrotoxic consequences, and its similar oral and parenteral bioavailability without central venous access requirement [25,26]. However, in OAIs, linezolid must be administered for a long period of time [27,28] with a real impact on the hospital microbial ecology [29], as shown by the emergence of linezolid resistance that averaged 3.5% of the CoNS in our center in 2011. This value is higher than the rates exposed in other studies [14,30 –32]. In our center, glycopeptide and linezolid resistance is limited currently to CoNS and resistance to glycopeptides has not been detected in S. aureus, contrary to the results reported by Vaudaux et al. [33]. Finally, in 2011, the fluoroquinolone/rifampicin combination used widely for the treatment of OAIs (particularly in PJIs) [4] appeared to be effective in fewer than 50% of CoNS infections because of the significant increase of fluoroquinolone resistance.

Conclusion

The choice of molecules used for the first-line empiric antibiotic treatment is directed by guidelines but also by protocols based on the local microbiologic data. Thus, the high proportion of methicillin-resistant strains involved in OAIs makes the use of an antimicrobial agent necessary with activity against methicillin-resistant staphylococci (glycopeptides or daptomycin). However, the increasing resistance to teicoplanin and the emergence of linezolid-resistant CoNS strains leads us to exclude these molecules as first-line agents in our center.

Finally, the challenge of improving diagnostic tests is huge, particularly to detect any resistance genes directly in specimens. Hence, collaboration among surgeons, microbiologists, and infectious disease specialists remains essential.

Footnotes

Author Disclosure Statement

The authors declare that no competing financial interests exist concerning this article, except for Eric Senneville, who has received honorarium from Novartis and travel grants from MSD, Sanofi-Aventis, and Novartis.

References

Lew

, Waldvogel

. Osteomyelitis. Lancet, 2004; 364:369–379.

Kurtz

, Lau

, Schmier

, et al. Infection burden for hip and knee arthroplasty in the United States. J Arthroplasty, 2008; 23:984–991.

Zimmerli

, Trampuz

, Ochsner

. Prosthetic-joint infections. N Engl J Med, 2004; 351:1645–1654.

Trampuz

, Zimmerli

. Diagnosis and treatment of implant-associated septic arthritis and osteomyelitis. Curr Infect Dis Rep, 2008; 10:394–403.

Osmon

, Berbari

, Berendt

, et al. Diagnosis and management of prosthetic joint infection: Clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis, 2013; 56:1–25.

Titécat

, Loïez

, Senneville

, et al. Evaluation of rapid mecA gene detection versus standard culture in staphylococcal chronic prosthetic joint infection. Diagn Microbiol Inf Dis, 2012; 73:318–321.

Poyart

, Quesne

, Boumaila

, Trieu-Cuot

. Rapid and accurate species-level identification of coagulase-negative staphylococci by using the sodA gene as a target. J Clin Microbiol, 2001; 39:4296–4301.

Ünal

, Hoskins

, Flokowitsch

, et al. Detection of methicillin-resistant staphylococci by using the polymerase chain reaction. J Clin Microbiol, 1992; 30:1685–1691.

Société de Pathologie Infectieuse de Langue Francaise (SPILF). Recommendations for bone and joint prosthetic device infections in clinical practice (prosthesis, implants, osteosynthesis). 2009; 1–61. www.infectiologie.com/site/medias/_documents/consensus/inf-osseuse-long.pdf (Last accessed November 30, 2014).

10.

Peel

, Cheng

, Buising

, Choong

. Microbiological aetiology, epidemiology, and clinical profile of prosthetic joint infections: Are current antibiotic prophylaxis guidelines effective?. Antimicrob Agents Chemother, 2012; 56:2386–2391.

11.

Sharma

, Douglas

, Coulter

, et al. Microbiology of infected arthroplasty: Implications for empiric peri-operative antibiotics. J Orthop Surg (Hong Kong), 2008; 16:339–342.

12.

Del Pozo

, Patel

. Clinical practice. Infection associated with prosthetic joints. N Engl J Med, 2009; 361:787–794.

13.

Tsukayama

, Estrada

, Gustilo

. Infection after total hip arthroplasty. A study of the treatment of one hundred and six infections. J Bone Joint Surg Am, 1996; 78:512–523.

14.

Hellmark

, Unemo

, Nilsdotter-Augustinsson

, Söderquist

. Antibiotic susceptibility among Staphylococcus epidermidis isolated from prosthetic joint infections with special focus on rifampicin and variability of the rpoB gene. Clin Microbiol Infect, 2009; 15:238–244.

15.

Segawa

, Tsukayama

, Kyle

, et al. Infection after total knee arthroplasty. A retrospective study of the treatment of eighty-one infections. J Bone Joint Surg Am, 1999; 81:1434–1445.

16.

Salgado

, Dash

, Cantey

, Marculescu

. Higher risk of failure of methicillin-resistant Staphylococcus aureus prosthetic joint infections. Clin Orthop Relat Res, 2007; 461:48–53.

17.

Senneville

, Joulie

, Legout

, et al. Outcome and predictors of treatment failure in total hip/knee prosthetic joint infections due to Staphylococcus aureus. Clin Infect Dis, 2011; 53:334–340.

18.

Parvizi

, Pawasarat

, Azzam

, et al. Periprosthetic joint infection: The economic impact of methicillin-resistant infections. J Arthroplasty, 2010; 25:103–107.

19.

Köck

, Becker

, Cookson

, et al. Methicillin-resistant Staphylococcus aureus (MRSA): Burden of disease and control challenges in Europe. Euro Surveill, 2010; 15:19688.

20.

John

, Harvin

. History and evolution of antibiotic resistance in coagulase-negative staphylococci: Susceptibility profiles of new anti-staphylococcal agents. Ther Clin Risk Manag, 2007; 3:1143–1152.

21.

Biavasco

, Vignaroli

, Varaldo

. Glycopeptide resistance in coagulase-negative staphylococci. Eur J Clin Microbiol Infect Dis, 2000; 19:403–417.

22.

Cremmiter

, Slassi

, Quincampoix

, et al. Decreased susceptibility to teicoplanin and vancomycin in coagulase-negative Staphylococci isolated from orthopedic-device-associated infections. J Clin Microbiol, 2010; 48:1428–1431.

23.

Gould

, Cauda

, Esposito

, et al. Management of serious methicillin-resistant Staphylococcus aureus infections: What are the limits?. Int J Antimicrob Agents, 2011; 37:202–209.

24.

Kim

, Kim

, et al. Outcome of vancomycin treatment in patients with methicillin-susceptible Staphylococcus aureus bacteremia. Antimicrob Agents Chemother, 2008; 52:192–197.

25.

Falagas

, Siempos

, Papagelopoulos

, Vardakas

. Linezolid for the treatment of adults with bone and joint infections. Int J Antimicrob Agents, 2007; 29:233–239.

26.

Senneville

, Legout

, Valette

, et al. Effectiveness and tolerability of prolonged linezolid treatment for chronic osteomyelitis: A retrospective study. Clin Ther, 2006; 28:1155–1163.

27.

Bassetti

, Vitale

, Melica

, et al. Linezolid in the treatment of gram-positive prosthetic joint infections. J Antimicrob Chemother, 2005; 55:387–390.

28.

Rao

, Ziran

, Hall

, Santa

. Successful treatment of chronic bone and joint infections with oral linezolid. Clin Orthop Relat Res, 2004; 427:67–71.

29.

Ager

, Gould

. Clinical update on linezolid in the treatment of Gram-positive bacterial infections. Infect Drug Resist, 2012; 5:87–102.

30.

, Kelesidis

, Tsiodras

, et al. The emerging problem of linezolid-resistant Staphylococcus. J Antimicrob Chemother, 2012; 68:4–11.

31.

Jones

, Ross

, Bell

, et al. Zyvox annual appraisal of potency and spectrum program: Linezolid surveillance program results for 2008. Diagn Microbiol Infect Dis, 2009; 65:404–413.

32.

Meka

, Gold

. Antimicrobial resistance to linezolid. Clin Infect Dis, 2004; 39:1010–1015.

33.

Vaudaux

, Ferry

, Uçkay

, et al. Prevalence of isolates with reduced glycopeptide susceptibility in orthopedic device-related infections due to methicillin-resistant Staphylococcus aureus. Eur J Clin Microbiol Infect Dis, 2012; 31:3367–3374.