Prevalence and characterization of vancomycin-resistant enterococci in chicken intestines and humans of korea

The prevalence, genotype for antibiotic resistance and antibiotic susceptibility of vancomycin resistant enterococci (VRE) were determined. And molecular typings of the Enterococcus faecium isolates were analyzed. Prevalence of VRE in chickens, healthy children and intensive care unit (ICU) patients was 41.6%, 7.9%, and 20.4%, respectively. Forty out of 54 isolates from chicken intestines, and 9 out of 11 from ICU patients were identified as Enterococcus faecium. Eleven out of 13 isolates from non-hospitalized young children were E. gallinarium. Twelve strains of E. faecalis were isolated from chicken intestines. The gene for the antibiotic resistance in E. faecium, and E. faecalis was vanA, while that in E. gallinarium was vanC1. E. faecium isolates were resistant to most of antibiotics except ampicillin and gentamicin. Molecular typing of the E. faecium strains obtained by pulse field gel electrophoresis and repetitive sequence-based PCR suggest that VRE transmit horizontally from poultry to humans, especially young children, via the food chains in Korea.     

Prevalence of streptogramin resistance in enterococci from animals: identification of vatD from animal sources in the USA

There is considerable debate over the contribution of virginiamycin use in animals to quinupristin/dalfopristin (Q/D) resistance in humans. In this study, the prevalence and mechanisms of streptogramin resistance in enterococci from animals and the environment were investigated. From 2000-2004, enterococci from samples were tested for antimicrobial susceptibility. Q/D-resistant isolates (minimum inhibitory concentration >or=4 microg/mL) were subjected to polymerase chain reaction (PCR) using primers for streptogramin resistance genes (ermB, msrC, vatD and vatE). From the analysis, 1029/6227 (17%) Q/D-resistant non-Enterococcus faecalis enterococci were identified. The majority of Q/D-resistant isolates were Enterococcus hirae (n=349; 34%), Enterococcus casseliflavus (n=271; 26%) and Enterococcus faecium (n=259; 25%). Using PCR, 55.5% (n=571) were positive for ermB, 3% (n=34) for msrC, 2% (n=20) for vatE and 0.3% (n=3) for vatD; 39% (n=401) were negative for all four genes. The vatD-positive samples comprised two E. faecium from chicken and one E. hirae from swine. The nucleotide sequence of vatD from the three isolates was 100% homologous to published vatD sequences. These data indicate that Q/D resistance among enterococci from animals remains low despite the long history of virginiamycin use. To date, this is the first report of vatD from enterococci in animals in the USA.     

Heterogeneity of vat(E)-carrying plasmids in Enterococcus faecium recovered from human and animal sources

In this study, quinupristin/dalfopristin (Q/D)-resistant Enterococcus faecium isolates (33 from poultry farms and 1 from a human outpatient) with Q/D minimal inhibitory concentrations ranging from 4 microg/mL to 32 microg/mL were analysed. Polymerase chain reaction detected the presence of vat(E) in all isolates. Using pulsed-field gel electrophoresis (PFGE), 14 distinct PFGE patterns were identified. The human E. faecium isolate was distinguishable from the 33 farm isolates by PFGE. Southern hybridisation localised the vat(E) gene to an 11 kb plasmid and resulted in five plasmid hybridisation types. The vat(E)-carrying plasmid from the human isolate showed a nearly identical hybridisation pattern to a plasmid from a farm isolate. This study showed that the vat(E) gene, conferring resistance to Q/D, was carried on different plasmids in a heterogeneous group of E. faecium, some of which may be acquired by E. faecium capable of infecting humans.     

Risk factors in enterococci isolated from foods in Morocco: Determination of antimicrobial resistance and incidence of virulence traits

A collection of enterococci isolated from meat, dairy and vegetable foods from Morocco including 23 Enterococus faecalis and 15 Enterococcus faecium isolates was studied. All isolates were sensitive to ampicillin, penicillin, and gentamicin. Many E. faecalis isolates were resistant to tetracycline (86.95%), followed by rifampicin (78.26% ciprofloxacin (60.87%), quinupristin/dalfopristin (56.52%), nitrofurantoin (43.47%), levofloxacin (39.13%), erythromycin (21.73%), streptomycin (17.39%), chloramphenicol (8.69%), vancomycin (8.69%), and teicoplanin (4.34%). E. faecium isolates showed a different antibiotic resistance profile: a high percentage were resistant to nitrofurantoin (73.33%), followed by erythromycin (66.60%), ciprofloxacin (66.66%), levofloxacin (60.00%), and rifampicin (26.66%), and only a very low percentage were resistant to tetracycline (6.66%). One isolate was resistant to vancomycin and teicoplanin. The incidence of virulence factors was much higher among E. faecalis isolates, especially for genes encoding for sex pheromones, collagen adhesin, enterococcal endocarditis antigen, and enterococcal surface protein. Isolates with multiple factors (both antibiotic resistance and virulence traits) were also more frequent among E. faecalis isolates, in which one isolate cumulated up to 15 traits. By contrast, several isolates of E. faecium had only very few unwanted traits as compared to only two isolates in E. faecalis. The high abundance of isolates carrying virulence factors and antibiotic resistance traits suggests that the sanitary quality of foods should be improved in order to decrease the incidence of enterococci.     

Nosocomial infections due to methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci at a university hospital in Taiwan from 1991 to 2003: resistance trends, antibiotic usage and in vitro activities of newer antimicrobial agents

A rapid increase of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection (from 39% in 1991 to 75% in 2003) and vancomycin-resistant enterococci (VRE) (from 1.2% in 1996 to 6.1% in 2003) at a university hospital in Taiwan was found. The noticeable rise of MRSA and VRE was significantly correlated with the increased consumption of glycopeptides, beta-lactam-beta-lactamase inhibitor combinations, extended-spectrum cephalosporins, carbapenems and fluoroquinolones (Pearson's correlation coefficient, P < 0.05). Minimum inhibitory concentrations (MICs) of 100 non-duplicate blood isolates of MRSA (in 2003) and of 25 non-duplicate isolates of vancomycin-resistant Enterococcus faecalis and 172 vancomycin-resistant Enterococcus faecium (in 1996-2003) causing nosocomial infection recovered from various clinical specimens of patients treated at the hospital to nine antimicrobial agents were determined by the agar dilution method. All of these isolates were susceptible to linezolid and were inhibited by 0.5mg/L of tigecycline, and all MRSA isolates were inhibited by daptomycin 1mg/L, including two isolates of MRSA with heteroresistance to vancomycin. Daptomycin had two-fold better activity against vancomycin-resistant E. faecalis (MIC90, 2 mg/L) than against vancomycin-resistant E. faecium (MIC90, 4 mg/L). Decreased susceptibilities of vancomycin-resistant E. faecium and MRSA to quinupristin/dalfopristin (non-susceptibility 25% and 8%, respectively) were found. Telithromycin had poor activity against the isolates tested (MIC90, 8 mg/L). Linezolid, daptomycin and tigecycline may represent therapeutic options for infections caused by these resistant Gram-positive organisms.     

Antibiotic resistance among enterococcal strains isolated from clinical specimens

The distribution and resistance patterns of clinical isolates of enterococci from hospital patients were compared with those obtained from outpatients. Of 235 enterococcal isolates 212 (90.2%) were identified as Enterococcus faecalis and 23 (9.8%) as E. faecium. E. faecium occurred more frequently in specimens from hospitalized patients than from outpatients (P < 0.001). Over 90% of all E. faecalis isolates were susceptible to ampicillin. Resistance to ampicillin occurred in 66.7% of hospital strains of E. faecium. High-level resistance to gentamicin (MIC > 500 mg/l) was seen in 37.03% of inpatients' and in 11.5% of outpatients' E. faecalis isolates and in 76.2% of hospital isolates of E. faecium. High-level streptomycin resistance (MIC > 2000 mg/l) occurred in 52.8% of E. faecalis and 76.2% of E. faecium hospital isolates. There were no isolates resistant to vancomycin. The community acquired strains isolated from outpatients were more susceptible than isolates from hospitalized patients to all antimicrobial agents tested.     

Withdrawal of growth-promoting antibiotics in Europe and its effects in relation to human health

The glycopeptide avoparcin, bacitracin, the macrolides spiramycin and tylosin, and the streptogramin virginiamycin were withdrawn as growth promoters in the European Union between 1995 and 1999 on the basis of the Precautionary Principle. Relevant resistance thereupon diminished among enterococci (the indicator organisms) isolated from animal and human faeces. However, animal enterococci were shown to differ from those that caused human infections, although their resistance genes were sometimes indistinguishable and thus probably have a common origin. Before the ban, human clinical isolates of enterococci resistant to vancomycin or teicoplanin were uncommon in many, but not all, parts of Europe and resistance to quinupristin/dalfopristin in the case of Enterococcus faecium was very rare. After the ban, these resistances increased in prevalence almost universally, to the detriment of human health. Campylobacters, normally susceptible to macrolides, increased in prevalence before and after the ban. Analyses suggest that the added risk to human health from resistance among enterococci and campylobacters selected by growth promoter use is small, whilst the benefit to human health from their use, hitherto largely ignored, might more than counterbalance this.     

Occurrence of the Van Genes inEnterococcus faecalis andEnterococcus faecium from clinical isolates in Korea

Enterococcus faecalis and Enterococcus faecium isolated from Korea patients in 1998 and 2005 were tested for susceptibility to nine different antimicrobial agents, including vancomycin and teicoplanin. Polymerase chain reaction (PCR) was used for the detection of several vancomycin resistance genes such as vanA ('high level'), vanB ('moderate high level'), vanC1 and vanC2 ('low level'). Both E. faecalis and E. faecium exhibited a resistance of 80% and more than 60% to synercid and mupirocin, respectively. Moreover, an average of 76% of all isolates was resistant to ciprofloxacin, gentamicin, lincomycin, cefotaxime, and meropenem, confirming the multiple drug resistance of most of the isolates. No resistance to vancomycin or teicoplanin was observed in the 1998 E. faecalis and E. faecium isolates. However, the 2005 E. faecalis and E. faecium isolates exhibited resistance of 16% and 12% to vancomycin and teicoplanin, respectively. In addition, vanA gene was detected in 4 strains of 2005 E. faecium isolates, thus showing a high resistance to vancomycin. No other vancomycin resistance genes, including vanB, vanC1, and vanC2, were found in our isolates. In this study, we compared the occurrence of antimicrobial resistance and the presence of specific resistance genes in E. faecalis and E. faecium. The results showed that the 2005 isolates were usually more resistant than the 1998 isolates.     

In vitro effect of levofloxacin and vancomycin combination against high level aminoglycoside-resistant enterococci

The in vitro effects of levofloxacin and vancomycin in combination were evaluated against high level aminoglycoside-resistant (HLAR) enterococci using chequerboard and time-kill curve techniques. We examined 28 strains of enterococci comprising 17 Enterococcus faecalis, 10 E. faecium and one E. durans. The combination of vancomycin and levofloxacin had indifferent activity against all isolates according to chequerboard microdilution method, but was synergistic for two isolates, one E. faecium and one E. faecalis, using the time-kill curve method. Both strains were levofloxacin resistant and had high level aminoglycoside resistance to gentamicin and streptomycin. Antagonism was not detected in any strain. The results of this study suggested that the combination of vancomycin with levofloxacin does not often show synergistic effect against high level aminoglycoside-resistant enterococci.     

肠球菌感染现状及其耐药性的变迁

目的了解肠球菌感染现状及其耐药性的变迁,为预防和治疗肠球菌感染提供依据。方法收集孙逸仙纪念医院2009～2011年患者标本中分离的肠球菌属,按照CLSI推荐的方法和判断标准,用纸片扩散法进行药敏试验,用WHONET5.3软件和SPSS13软件进行统计分析。结果近3年从各种临床标本中共分离出1016株肠球菌,粪肠球菌587株（57.78%）,屎肠球菌370株（36.42%）。标本主要来源于尿液（21.26%）、痰液（17.42%）、体液及胆汁（17.22%）。粪肠球菌对氨苄西林/舒巴坦、氨苄西林、亚胺培南耐药率较低,分别为0%、7.5%、7.5%左右,对高浓度庆大霉素耐药率为50%左右;屎肠球菌耐药性明显高于粪肠球菌,对氨苄西林/舒巴坦耐药率超过90%,对高浓度庆大霉素耐药率超过70%,但对喹奴普汀/达福普汀仅为0.96%。肠球菌属细菌对利奈唑胺、万古霉素、替考拉宁仍最敏感（耐药率≤5%）,2010及2011年分别分离出耐万古霉素屎肠球菌1株及8株,耐利奈唑胺的粪肠球菌6株及4株,2011年分离出耐替考拉宁的屎肠球菌5株。结论万古霉素、替考拉宁和利奈唑胺是对肠球菌抑菌率最高的药物,万古霉素耐药肠球菌发生率有增加趋势,特别是出现了个别利奈唑胺耐药的肠球菌菌株,因此,监测肠球菌属的耐药状况对指导临床治疗具有重要意义。     

Antimicrobial resistance of Enterococci in Lebanon

There is little information on the types of Enterococcus spp and their antibiotic resistance patterns in Lebanon. One hundred and fifty-three consecutive clinical enterococcal isolates collected between 1998 and 1999 were tested against 11 antimicrobial agents using disk diffusion and the Etest. The isolates were identified by conventional methods and API-Strep and were found to consist of Enterococcus faecalis (72.5%), Enterococcus faecium (22.9%), Enterococcus avium (3.2%) and Enterococcus gallinarum (1.3%). The percent of resistant strains of E. faecalis and E. faecium respectively were, ampicillin 0.9 and 14%, erythromycin 59% and 40%, tetracycline 72% and 34%, chloramphenicol 32 and 11%, rifampin 36% and 57%, ciprofloxacin, 23% and 34%, norfloxacin 22 and 8%. High level aminoglycoside (HLA) resistance was found in 19% E. faecalis and 9% E. faecium for gentamicin and 36% and 26% for streptomycin. Excellent correlation was observed between the high level disk tests and the Etest in the detection of HLA resistance but not with the regular disks. None of the isolates showed resistance to vancomycin or teicoplanin except for one E. gallinarum isolate which showed intermediate resistance (MIC 16 mg/l) to vancomycin. These variable antimicrobial rates of resistance suggest a surveillance programme for antimicrobial resistance in this country would be helpful to help control infection, guide empirical antibiotic therapy and implement a policy of antibiotic usage.     

Reduced susceptibility to quinupristin/dalfopristin in Enterococcus faecium in Greece without prior exposure to the agent

During 2005-2006, a total of 865 Enterococcus faecium isolated from patients from eight Greek hospitals were tested for susceptibility to quinupristin/dalfopristin (Q/D). Among them, 250 genetically unrelated strains (28.9%) were found to be intermediate-resistant to Q/D (minimum inhibitory concentration (MIC) 1.5-4 mg/L); all were resistant to dalfopristin (MIC=16-64 mg/L), whilst 69% were resistant to quinupristin, carrying the ermB gene. No strain was found to carry any of the known genes, such as vatE and vatD, involved in Q/D resistance, indicating that a non-transferable undetermined mechanism is responsible for the expression of low-level Q/D resistance. The high percentage of Q/D-intermediate-resistant E. faecium in Greece was not associated with prior consumption of the agent or with the veterinary use of virginiamycin.     

120株肠球菌耐药分析及药物选择

目的观察肠球菌属的临床分布特点及耐药状况。方法收集医院2011年1月～6月培养检出的120株肠球菌属,分析其在各种临床标本中的分布特征和耐药状况。结果检出粪肠球菌63株(52.5%)、屎肠球菌48株(40.8%)、其他肠球菌8株(6.7%)。其中尿液中检出58株肠球菌(48.3%)。屎肠球菌的耐药率普遍较粪肠球菌高。未检出耐万古霉素的尿肠球菌和粪肠球菌,检出耐利奈唑胺粪肠球菌2株。结论肠球菌属感染以粪肠球菌和屎肠球菌为主,肠球菌属中各种菌对抗菌药物的耐药性有差异,应在抗菌药物敏感试验指导下并结合感染部位合理地选用抗菌药物。     

老年患者屎肠球菌感染的临床分布及耐药性分析

目的探讨老年患者屎肠球菌感染的临床分布特点,并分析其对临床常用抗菌药物的耐药性,为临床合理治疗屎肠球菌感染提供参考依据。方法采用回顾性分析及统计分析方法,收集我院2013年1月至2015年12月期间屎肠球菌感染的老年患者(≥65岁)的临床数据,对其进行感染现状及耐药性分析。结果3年内共检出屎肠球菌感染384例,其检出率呈逐年升高趋势。屎肠球菌感染的标本类型中尿液所占比例最高,达47.14%,其次为引流液和全血标本,分别占19.53%和16.15%。在科室分布中,标本主要分离于重症监护病房(ICU)、普通外科病房和呼吸内科病房,分别占23.96%、20.57%和16.41%。药敏结果显示:屎肠球菌对氨苄西林、红霉素、环丙沙星、克林霉素、莫西沙星、青霉素G、左氧氟沙星等抗菌药物的耐药性均超过90%,而对喹奴普汀/达福普汀、替加环素、万古霉素、利奈唑胺等药物具有高度敏感性。结论屎肠球菌对不同抗菌药物的敏感性不同,且其院内感染近年有增高趋势,对屎肠球菌感染的耐药性监测,有利于指导临床合理用药。     

Antibiotic resistant fecal isolates of Enterococci among unselected patients outside the clinical sector: an epidemiological study from Southern Germany

PURPOSE: The aim of the study was to assess the prevalence and determinants of antibiotic-resistant Enterococci in a large group of outpatients in Southern Germany. METHODS: Stool samples were collected from 497 unselected patients aged 40-75 years attending general practitioners. Enterococcus faecium (E. faecium) and Enterococcus faecalis (E. faecalis) were cultured and minimal inhibitory concentrations of antibiotics used inside and outside the clinical sector were tested. RESULTS: E. faecium and E. faecalis could be identified and cultured in 60 (12.4%) and 205 (41.2%) of the stool samples, respectively. Under non-selective culture conditions no vancomycin-resistant Enterococcus (VRE) isolate was found. Only E. faecium isolates showed resistance to fluoroquinolones, 40% were resistant to ciprofloxacin. The prevalences of E. faecium resistance to ampicillin and doxycycline were 3.3% and 13.3%, respectively, whereas 0.5% and 29.6% of the E. faecalis isolates were resistant to ampicillin and doxycycline, respectively. Antibiotic use during the last 3 months was significantly associated with antibiotic resistance (to either ampicillin, imipenem, or doxycycline) of E. faecalis isolates (OR: 2.9; CI: 1.2-6.8). CONCLUSIONS: Prevalences of resistance were generally lower than and patterns of resistance were quite different from previous investigations in the clinical setting. Recent antibiotic use was associated with increased colonization with resistant strains.     

天津市八家医院肠球菌临床分离株的耐药分析

目的：研究天津地区临床分离的肠球菌对常用抗生素的耐药情况，为临床合理选用抗生素提供科学依据。方法：收集天津市8家三级甲等医院于2001年2月-2002年2月分离的149株肠球菌，采用纸片扩散法(K-B法)进行药敏试验。结果：149株肠球菌感染中粪肠球菌73．8％，屎肠球菌16．1％。110株粪肠球菌耐药率较低的药物为万古霉素1．0％，氨苄西林38．6％，青霉素41．3％等。24株屎肠球菌耐药率较低的药物为万古霉素4．3％，氯霉素38．5％。结论：肠球菌耐药情况较为严重，应根据药敏试验合理使用抗菌药物。     

Susceptibilities of Enterococcus faecium, PRSP and MRSA to RP59500 and their correlations with those to other drugs]

Investigations on emergence of vancomycin-resistant Enterococcus faecium (VREF) which has recently been attracting attention, especially in the Western countries, have been conducted in Japan. A total of 1,239 isolates of E. faecium were collected from 19 institutions during the period of April 1995 and June 1996, in the purpose of evaluating susceptibilities to variety of antimicrobial agents, including RP59500 and vancomycin (VCM), and detecting vancomycin-resistant genes (van genes). Susceptibilities of penicillin-resistant Streptococcus pneumoniae (PRSP) and methicillin-resistant Staphylococcus aureus (MRSA) were also studied. As a result, 2 isolates of E. faecium were found to be moderately resistant to VCM showing MIC of 8 micrograms/ml though the final identification in species level and the detection of van genes by PCR method have not been completed. On the other hand there detected no MRSA nor PRSP showing moderately resistant or resistant to VCM. It was concluded that RP59500 and VCM possessed favorable activity against clinically isolated E. faecium, PRSP and MRSA. Among other species of enterococci, moderately resistant strains to VCM showing MIC of 8 micrograms/ml were detected; 10 isolates of E. gallinarum, 4 of E. casseliflavus and 2 of E. flavescens. In those isolates, vanC1 and vanC2 were detected by PCR, and vanB was also detected in a isolates of E. gallinarum simultaneously.     

Evaluation of the in vitro activity of tigecycline against multiresistant Gram-positive cocci containing tetracycline resistance determinants

This study was undertaken to test the in vitro activity of tigecycline against 117 clinically relevant Gram-positive pathogens and to correlate this activity with their resistance gene content. Overall, tigecycline showed a minimal inhibitory concentration (MIC) range of 0.015-0.5mg/L, able to inhibit potently all multiresistant streptococci, enterococci and MR staphylococci. Tigecycline was active against methicillin-resistant Staphylococcus aureus (MRSA) and enterococci, with MICs for 90% of the organisms (MIC(90)) of 0.25 mg/L and 0.12 mg/L, respectively, being more active than linezolid (MIC(90)=2 mg/L) and quinupristin/dalfopristin (MIC(90)=0.5 and 2-4 mg/L, respectively). Molecular characterisation of resistance determinants demonstrated the concomitant presence of different classes of genes: in particular, tet(M), erm(B) and erm(C) in Streptococcus agalactiae; tet(O), variably associated with different erm genes, in Streptococcus pyogenes; vanA, tet(M) and erm(B) in Enterococcus faecalis, and vanA and erm(B) in Enterococcus faecium. All the MRSA strains harboured SCCmec and erm genes and 50% possessed tet(K) with tet(M) genes. Staphylococcus epidermidis strains were only resistant to erythromycin. These results clearly demonstrate that tigecycline has a MIC(90) range of 0.015-0.5 mg/L both against tetracycline-susceptible and -resistant isolates carrying other resistance determinants, suggesting that this drug could play an important role in the treatment of infections caused by these multiresistant Gram-positive pathogens.     

Bacterial resistance to antimicrobials in urinary isolates

Escherichia coli accounted for about 80% of organisms in uncomplicated urinary tract infections (UTIs), followed by Staphylococcus spp. especially Staphylococcus saprophyticus, and Proteus mirabilis. Against E. coli isolates from patients with uncomplicated UTI, faropenem was the most effective. Up to 1999, fluoroquinolone-resistant isolates were not observed in patients with uncomplicated UTI, but in 2001 fluoroquinolone-resistant E. coli isolates emerged and accounted for about 8%. Various types of organisms were isolated in patients with complicated UTI. Enterococcus faecalis, E. coli, and Pseudomonas aeruginosa were the three most frequent organisms isolated. These three organisms accounted for 44.6%. Amongst oral agents, faropenem showed the lowest rate of resistance against E. coli followed by cephems. The rates of highly fluoroquinolone-resistant and cefpodoxime-resistant E. coli isolates increased rapidly from 1998 to 2001. Fluoroquinolone-resistant P. aeruginosa isolates accounted for about 40% in 2001. Against this species, amikacin was the most effective antimicrobials among all agents tested. About 17% of Pseudomonas were resistant to carbapenem. Eight milligram per litre of ampicillin inhibited all E. faecalis isolates; about 60% of Enterococcus faecium were resistant to ampicillin. The rates of levofloxacin-resistant isolates of E. faecalis and E. faecium were 38 and 97% respectively. UTIs caused by vancomycin resistant enterococci (VRE) are rare in Japan.     

Linezolid and quinupristin/dalfopristin resistance in vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus prior to clinical use in Turkey

The aim of this study was to determine the in vitro antimicrobial activity of recently licensed quinupristin/dalfopristin and linezolid which have not yet been in clinical use in Turkey against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) strains isolated from various clinical specimens by using the Etest. The results showed that all MRSA strains were fully susceptible to both the new compounds. All strains were inhibited by 1 mg/l quinupristin/dalfopristin (mode MIC 0.38 mg/l) and by 3 mg/l linezolid (mode MIC 1.5 mg/l). Four strains of Enterococcus faecium showed an increase of resistance of 2-3 mg/l to quinupristin/dalfopristin (susceptible mode MIC 0.38 mg/l). With linezolid, all strains except two fell within the range 0.75-2.0 mg/l.