Meticillin-resistant S. Aureus Research Articles

Meticillin-resistant Staphylococcus aureus and meticillin-susceptible Staphylococcus aureus screening in a cohort of haemodialysis patients: carriage, demographics and outcomes

Patients on haemodialysis are vulnerable to colonization with Staphylococcus aureus due to frequent hospital contact, indwelling devices, and impaired immunity. Additionally colonization is associated with increased risk of infection. To determine the prevalence of both meticillin-resistant S. aureus (MRSA) and meticillin-susceptible S. aureus (MSSA) carriage in our haemodialysis cohort and to identify any risk factors predisposing to carriage, recolonization, or persistent carriage following a decolonization programme. All haemodialysis patients screened for S. aureus carriage between June 2009 and May 2011 were retrospectively followed up for 18 months using hospital electronic records. Statistical analysis was performed using IBM SPSS version 19. Out of 578 patients screened, 288 patients (49%) had at least one positive swab (10% MRSA, 90% MSSA). Of these patients, 265 completed a course of decolonization therapy following which 36% successfully eradicated (eradicators) and 64% did not (non-eradicators). There was no statistically significant difference in patient demography, type of vascular access, 18-month patient mortality, or number of hospital admissions between the two groups. Those who failed to eradicate were more likely to have had an episode of S. aureus bacteraemia within the study period compared to those who successfully decolonized (P = 0.003). Half of our haemodialysis cohort was colonized with S. aureus at any one time over an 18-month period. Following decolonization, one-third of patients remained successfully eradicated for 18 months. Non-eradicators have an increased risk of bacteraemia, which is associated with poor mortality. We would recommend routine screening and aggressive attempts to decolonize.

The dynamic changes of dominant clones of Staphylococcus aureus causing bloodstream infections in the European region: results of a second structured survey.

Staphylococcus aureus is one of the most important human pathogens and meticillin-resistant S. aureus (MRSA) presents a major cause of healthcare- and community-acquired infections. This study investigated the spatial and temporal changes of S. aureus causing bacteraemia in Europe over a five-year interval and explored the possibility of integrating pathogen-based typing data with epidemiological and clinical information at a European level. Between January 2011 and July 2011, 350 laboratories serving 453 hospitals in 25 countries collected 3,753 isolates (meticillin-sensitive S. aureus (MSSA) and MRSA) from patients with S. aureus bloodstream infections. All isolates were sent to the national staphylococcal reference laboratories and characterised by quality-controlled spa typing. Data were uploaded to an interactive web-based mapping tool. A wide geographical distribution of spa types was found, with some prevalent in all European countries. MSSA was more diverse than MRSA. MRSA differed considerably between countries with major international clones expanding or receding when compared to a 2006 survey. We provide evidence that a network approach of decentralised typing and visualisation of aggregated data using an interactive mapping tool can provide important information on the dynamics of S. aureus populations such as early signalling of emerging strains, cross-border spread and importation by travel.

Clonal relatedness is a predictor of spontaneous multidrug efflux pump gene overexpression in Staphylococcus aureus

Increased expression of genes encoding multidrug resistance efflux pumps (MDR-EPs) contributes to antimicrobial agent and biocide resistance in Staphylococcus aureus. Previously identified associations between norA overexpression and spa type t002 meticillin-resistant S. aureus (MRSA), and a similar yet weaker association between mepA overexpression and type t008 meticillin-susceptible S. aureus (MSSA), in clinical isolates are suggestive of clonal dissemination. It is also possible that related strains are prone to mutations resulting in overexpression of specific MDR-EP genes. Exposure of non-MDR-EP-overexpressing clinical isolates to biocides and dyes can select for MDR-EP-overexpressing mutants. spa types t002 and t008 isolates are predominated by multilocus sequencing typing sequence types (STs) 5 and 8, respectively. In this study, non-MDR-EP gene-overexpressing clinical isolates (MRSA and MSSA) representing ST5 and ST8 were subjected to single exposures of ethidium bromide (EtBr) to select for EtBr-resistant mutants. Measurements of active EtBr transport among mutants were used to demonstrate an efflux-proficient phenotype. Using quantitative reverse-transcription PCR, it was found that EtBr-resistant mutants of ST5 and ST8 parental strains predominantly overexpressed mepA (100%) and mdeA (83%), respectively, regardless of meticillin sensitivity. Associations between clonal lineage and MDR-EP gene overexpression differed from those previously observed and suggest the latter is due to clonal spread of efflux-proficient strains. The predilection of in vitro-selected mutants of related strains to overexpress the same MDR-EP gene indicates the presence of a consistent mutational process.

Survey of neonatal unit outbreaks in North London: identifying causes and risk factors

This survey was undertaken after a number of neonatal unit (NNU) outbreaks were reported to the North London health protection teams (HPTs). To determine the diversity of the outbreaks, ascertain potential sources and contributing factors, and identify the investigative procedures followed and control measures implemented. Using a structured questionnaire, information from the HPT database was collected for all NNU outbreaks reported between January 2010 and February 2011. Ten outbreaks were identified from seven hospitals in 14 months. There was one para-influenza outbreak, seven Staphylococcus aureus [including six meticillin-resistant S.aureus (MRSA)] outbreaks, and two Gram-negative outbreaks. Potential sources of transmission identified for the MRSA outbreaks were healthcare worker (HCW)-assisted transmission (N=2) and mother-to-baby transmission with onward HCW-assisted transmission (N=3). An environmental source with onward HCW-assisted transmission was documented for one of the Gram-negative outbreaks. Interventions included patient screening and enhanced cleaning (N=10), isolating/cohorting affected neonates (N=9), barrier nursing (N=6), staff movement restrictions (N=5), hand hygiene audits (N=4), staff screening (N=4), household contact screening (N=3) and environmental sampling (N=3). Potential contributing factors included inadequate staffing levels, cluttered unit, inadequate sterilization of communal milk-expressing equipment and inappropriate follow-up of MRSA results. This survey determined the diversity of NNU outbreaks in North London, and highlighted the importance of a multi-faceted approach to outbreak control. These data will assist in the development of clinical standards for the prevention, control and reporting of NNU outbreaks, and guidance for best practice in NNUs.

Pharmacodynamic profile of commonly utilised parenteral therapies against meticillin-susceptible and meticillin-resistant Staphylococcus aureus collected from US hospitals

Staphylococcus aureus is a well-recognised pathogen with an evolving phenotypic profile often limiting conventional β-lactam use. In vitro potency and pharmacodynamic profile of commonly utilised agents against 1238 meticillin-susceptible S. aureus (MSSA) and 1259 meticillin-resistant S. aureus (MRSA) from clinical specimens at 42 hospitals were assessed. Non-duplicate, non-urine isolates were tested by broth microdilution against cefazolin, ceftaroline, ceftriaxone, daptomycin, linezolid, nafcillin, tigecycline and vancomycin. Monte Carlo simulations were conducted using pharmacokinetic profiles from patients or volunteers to generate the probability of target attainment and determine the cumulative fraction of response (CFR), a modelling-based prediction tool of achieving pharmacokinetic/pharmacodynamic endpoints, for commonly used regimens. Of isolates tested, 62 MSSA (5.0%) were ceftriaxone-non-susceptible and 4 (0.3%) and 2 (0.2%) MRSA were ceftaroline- and daptomycin-non-susceptible, respectively. Against MSSA, cefazolin 1000mg q8h and nafcillin 2000mg q4h produced CFRs ≥90%. For ceftriaxone, only 2000mg q12h produced a CFR ≥90%. Against MSSA and MRSA, ceftaroline, daptomycin, linezolid and tigecycline provided CFRs ≥90%. Vancomycin produced similar CFRs against MSSA and MRSA. Vancomycin 1000mg and 15mg/kg q8h produced CFRs of 91% and 93%, respectively, whilst q12h doses were <90%. Against respiratory and blood isolates or ICU isolates, only vancomycin q8h produced desired CFRs, where the MIC90 was 2μg/mL. These data suggest cefazolin and nafcillin produce high CFRs against MSSA, whilst ceftriaxone at common doses may no longer be suitable. Vancomycin q8h is needed to optimise CFRs. Ceftaroline, daptomycin, tigecycline and linezolid produced sufficiently high CFRs against MSSA and MRSA utilising approved regimens.

Selection and characterisation of Staphylococcus aureus mutants with reduced susceptibility to the investigational oxazolidinone MRX-I

MRX-I is a new oxazolidinone antimicrobial under development. In this study, the potential for development of resistance to MRX-I in Staphylococcus aureus was investigated and key mutations were characterised. Determination of spontaneous resistance frequency and the mutant selection window (MSW) were performed with meticillin-susceptible S. aureus (MSSA) ATCC 29213, meticillin-resistant S. aureus (MRSA) ATCC 33591 and two clinical MRSA isolates SA 0016 and SA 0017. Selected resistant mutants were sequenced for 23S rRNA as well as genes encoding the ribosomal proteins L3, L4 and L22. Resistance frequencies for the aforementioned strains were <8.25×10−12, <6.33×10−12, <2.96×10−13 and <4.52×10−13, respectively, and the MSW of MRX-I was 2–4, 1–4, 1–2 and 1–4mg/L, respectively. After 30 serial passages, MRX-I minimum inhibitory concentrations (MICs) increased up to 8- to 16-fold both against MSSA and MRSA, whilst linezolid MICs increased 128-fold against MSSA and 16- to 32-fold against MRSA. MRX-I resistance mutations were clustered mainly in 23S rRNA and L3 protein regions. The U2504A transversion in 23S rRNA dominated in MRX-I-resistant mutants. No mutations in L4 and L22 proteins were observed. MRX-I exhibits a low potential to develop resistance in S. aureus, with a reduced resistance propensity compared with linezolid.

Minocycline, often forgotten but preferred to trimethoprim–sulfamethoxazole or doxycycline for the treatment of community-acquired meticillin-resistant Staphylococcus aureus skin and soft-tissue infections

Treatment of uncomplicated skin and soft-tissue abscesses caused by meticillin-sensitive Staphylococcus aureus or meticillin-resistant S. aureus (MRSA) is problematic. Incision and drainage aside, oral antibiotic therapy for uncomplicated community-acquired MRSA (CA-MRSA) is limited and frequent choices include clindamycin, doxycycline or trimethoprim–sulfamethoxazole (TMP–SMX). The most common oral antibiotics used for CA-MRSA are doxycycline or TMP–SMX, which often fail to eradicate the infection. With MRSA, in vitro susceptibilities do not always predict in vivo effectiveness. In situations where doxycycline or TMP–SMX fails in the treatment of uncomplicated cutaneous abscesses due to CA-MRSA, minocycline is reliably effective.

High vancomycin minimum inhibitory concentrations with heteroresistant vancomycin-intermediate Staphylococcus aureus in meticillin-resistant S. aureus bacteraemia patients

Patients with high vancomycin minimum inhibitory concentrations (MICs) and heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) infection are associated with treatment failure and poor outcomes. The main purpose of this study was to investigate the effect of hVISA on patient outcome, considering both the high vancomycin MIC and the existence of heteroresistant phenotypes. From January 2005 to December 2009, consecutive meticillin-resistant S. aureus (MRSA) isolates from 284 cases of MRSA bacteraemia receiving glycopeptide therapy were collected for further MIC and hVISA testing. The demographic distribution, clinical features and outcomes in bacteraemia patients with different vancomycin MICs and hVISA status in MRSA isolates were subsequently compared. Subjects were divided into three groups: low vancomycin MIC (<1.5mg/L) with vancomycin-sensitive S. aureus (VSSA) (n=50); high vancomycin MIC (≥1.5mg/L) with VSSA (n=218); and high vancomycin MIC with hVISA (n=16). Cox regression analysis demonstrated that the high MIC with VSSA group exhibited significantly higher 30-day mortality than the low MIC with VSSA group [odds ratio (OR)=2.349, 95% confidence interval (CI) 1.078–5.118]. The high MIC with hVISA phenotype was not associated with higher mortality but was independently associated with persistent MRSA bacteraemia (OR=5.996, 95% CI 1.438–25.005). To summarise, although hVISA is correlated with persistent bacteraemia, higher mortality in high vancomycin MIC infections could not be explained by the existing hVISA phenotype. Facing persistent bacteraemia under glycopeptide therapy for 7 days, clinicians should consider shifting to an alternative class of antibiotics to treat hVISA infection.

Population structure and characterisation of Staphylococcus aureus from bacteraemia at multiple hospitals in China: association between antimicrobial resistance, toxin genes and genotypes

Staphylococcus aureus from bacteraemia at multiple hospitals in China were genetically characterised to improve understanding of its epidemiology. A total of 236 consecutive, non-duplicate S. aureus bacteraemia isolates were collected at 16 Chinese hospitals. Isolates were characterised by antimicrobial resistance, 19 toxin genes, agr alleles, multilocus sequence typing and spa typing. The prevalence of meticillin-resistant S. aureus (MRSA) was 47.5% (112/236). Forty-two sequence types (STs) and 63 spa types were identified, including 14 STs and 14 spa types for MRSA. Clonal complex (CC) 8, CC5, ST7 and CC188 accounted for 67.4% of the isolates. ST239–t030/t037–SCCmecIII–agrI was the predominant MRSA genotype (50%), followed by ST5–t002/t570–SCCmecII–agrII (8%). A vancomycin MIC ≥ 1mg/L was detected significantly more often in ST5–SCCmecII and ST239–t037–SCCmecIII, whereas rifampicin resistance was overwhelmingly associated with ST239–t030–SCCmecIII (P<0.001). Oxacillin MICs were relatively low for ST59-MRSA. Major genotypes of meticillin-susceptible S. aureus (MSSA) were ST7–t091/t796–agrI (16.1%), ST188–t189–agrI (12.1%) and ST398–t571/t034–agrI (5.6%). Toxin genes were identified in 95.8% of isolates and formed 89 toxin gene profiles. The toxin genes sea, selk, selq and sell were significantly more common in MRSA, whilst tsst-1, seb, sed, selm, seln, selp and selj were more prevalent in MSSA (P<0.001). The pvl gene was more commonly detected in CC59, whereas tsst-1 was more frequent in CC15, CC188 and ST398 (P<0.001). The major genotypes were associated with specific antimicrobial resistance and toxin gene profiles.

Activity of the antiseptic polyhexanide against meticillin-susceptible and meticillin-resistant Staphylococcus aureus.

Staphylococcus aureus is one of the most important pathogens, with increasing emergence of meticillin-resistant S. aureus (MRSA) strains. This is associated not only with multiresistance to antibiotics but also with increasing resistance to topical antibiotics and antiseptics. As the antiseptic polyhexanide has only a low risk of emergence of resistant strains, the aim of the study was to obtain data on the sensitivity of S. aureus towards polyhexanide. The effect of polyhexanide was tested against 80 meticillin-susceptible S. aureus (MSSA) and 80 MRSA strains from sporadic cases as well as against 6 MRSA outbreak strains. The clonal diversity of the 166 strains was proven by pulsed-field gel electrophoresis (PFGE). Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined by the serial broth microdilution technique according to DIN 58940. Time-kill studies were performed for reference strains MSSA ATCC 29213 and MRSA ATCC 33591. MICs and MBCs in the range of 0.5-2mg/L were found. According to a created epidemiological cut-off (ECOFF) value of 4mg/L, all strains were regarded as susceptible to polyhexanide, including MRSA epidemic strains and MSSA and MRSA sporadic strains with various antibiotic susceptibility patterns. Addition of up to 4% albumin to the test medium did not change the MICs and MBCs. Time-kill studies showed reduction rates of 4log10CFU/mL for 200mg/L and 5log10CFU/mL for 400mg/L polyhexanide within 5-30min. It is concluded that polyhexanide is suitable for topical eradication of S. aureus.

Performance of different commercial methods for determining minimum inhibitory concentrations of glycopeptides and linezolid against blood isolates of Staphylococcus aureus.

The aim of this study was to determine the accuracy of commercial systems (VITEK® 2, Etest and Sensititre®) in determining the minimum inhibitory concentrations of vancomycin, teicoplanin and linezolid of Staphylococcus aureus strains and to evaluate the reproducibility of each system in a clinical microbiology laboratory. In total, 115 strains of S. aureus isolated from blood cultures were tested with all three commercial methods as well as the broth microdilution method, which is designated as the standard for glycopeptides and linezolid. Fourteen different S. aureus strains were included in a reproducibility test for all methods and antibiotics. For these strains, antimicrobial susceptibility testing was repeated 10 times on different days with all four methods, each time using the same inoculum. All three commercial methods exhibited similar performance in categorisation of nearly all of the meticillin-susceptible S. aureus (MSSA) isolates. Discrepancies were registered for meticillin-resistant S. aureus (MRSA); 2.5% of the strains in the intermediate or resistant category with the VITEK 2 system were not recognised as resistant by Etest and Sensititre. Moreover, none of the three commercial methods provided accurate results compared with homemade broth microdilution. Reproducibility of vancomycin and teicoplanin was 100% with VITEK 2 and Sensititre and 98.75% with Etest. Microdilution showed a reproducibility of 95.6% with vancomycin and 83.1% with teicoplanin. In contrast to previous reports, the best agreement with microdilution was exhibited by VITEK 2 both for MSSA and MRSA. For the antibiotics tested, the best reproducibility was obtained with the VITEK 2 and Sensititre systems.

Effectiveness of a bundled intervention of decolonization and prophylaxis to decrease Gram positive surgical site infections after cardiac or orthopedic surgery: systematic review and meta-analysis

Objective To evaluate studies assessing the effectiveness of a bundle of nasal decolonization and glycopeptide prophylaxis for preventing surgical site infections caused by Gram positive bacteria among patients undergoing cardiac...

P106 Comparing susceptibility profiles of antibiotics by contour interval analysis: Ceftaroline and Belgian Streptococcus pneumoniae (SP) and MRSA isolates

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil, is a novel cephalosporin exhibiting bactericidal activity in vitro against Gram-positive organisms, including meticillin-susceptible Staphylococcus aureus (MSSA), meticillin-resistant S. aureus (MRSA), β-haemolytic streptococci, viridans group streptococci (VGS) and Streptococcus pneumoniae, as well as against many common Gram-negative organisms. The objective of this study was to determine the spectrum and potency of ceftaroline against recent (2010) leading pathogens causing complicated skin and soft-tissue infections (cSSTIs) isolated in Europe. A total of 2438 isolates from the Assessing Worldwide Antimicrobial Resistance and Evaluation (AWARE) programme were identified as cSSTI pathogens. Isolates were collected from patients in 52 medical centres in 19 European countries. Reference susceptibility testing for ceftaroline and commonly used antimicrobials was performed by broth microdilution methodologies. Ceftaroline was very active overall against S. aureus (MIC50/90 = 0.25/1 mg/L) and inhibited 100.0% of isolates at a MIC of ≤2 mg/L. Activity against MRSA was documented (MIC50/90 = 1/2 mg/L) but was lower than that observed against MSSA (MIC50/90 = 0.25/0.25 mg/L). Ceftaroline was also very active against 460 β-haemolytic streptococci and 93 VGS (MIC90 = 0.015 mg/L and 0.06 mg/L, respectively). Ceftaroline was active against Escherichia coli (MIC50 = 0.12 mg/L) and Klebsiella pneumoniae (MIC50 = 0.06 mg/L) not expressing extended-spectrum β-lactamases, with activity similar to ceftriaxone and ceftazidime. In summary, this study documents the potent in vitro activity of ceftaroline when tested against recent pathogens isolated from patients with cSSTI in Europe.

Prevalence of fusB in Staphylococcus aureus clinical isolates

Fusidic acid (FA) resistance in Staphylococcus aureus markedly varied among different regions. Few data for FA resistance are available in China. In this study, FA susceptibility testing was performed, and the prevalence of fusB and fusC in 116 clinical isolates of S. aureus was investigated by PCR. Mutations in fusA were also determined by sequencing of PCR products. Molecular typing of fusB-positive strains was based on multilocus sequence typing (MLST), spa typing and pulsed-field gel electrophoresis (PFGE). A DNA fragment flanking fusB was sequenced. Transformation experiments were carried out in fusB-positive S. aureus. Of 116 S. aureus including 19 meticillin-resistant S. aureus (MRSA) and 97 meticillin-susceptible S. aureus (MSSA), four (3.5 %) were resistant to FA with MICs of 6-12 µg ml(-1), including one MRSA from blood and three MSSA from wound exudates. All four FA-resistant isolates were found to be fusB gene positive. Three FA-resistant MSSA strains had the same MLST profile of ST630 and spa type of t377, whilst the MRSA strain belonged to ST630-t4549. Only one PFGE pattern was recognized for these four strains. No fusC and fusA mutations were detected in any of the isolates. FA resistance in fusB-positive clinical isolates could be transferred to S. aureus RN4220. The fusB gene was located in a transposon-like element, which had 99 % identity with that found in pUB101. In conclusion, the FA resistance rate is low in S. aureus, and the fusB gene is responsible for the resistance.

Wound infections caused by inducible meticillin-resistant Staphylococcus aureus strains.

Detection of meticillin resistance in Staphylococcus aureus isolates continues to be a challenge. Clinical specimens obtained from abscesses from two epidemiologically unrelated outpatients were positive for meticillin-resistant S. aureus (MRSA) by a commercial PCR assay, but colonies obtained by culture were susceptible to oxacillin by an automated testing method. The colonies were also negative using a penicillin-binding protein 2a (PBP2a) latex agglutination test. Because of the discrepancy between the genotypic and phenotypic results, both isolates were re-tested by PCR, disc diffusion, VITEK® 2 and MicroScan® and were plated on chromogenic agar. Both isolates also underwent cefoxitin induction for additional susceptibility testing studies. Following overnight induction with cefoxitin, both isolates demonstrated resistance to oxacillin and cefoxitin by the two automated methods and by disc diffusion, and were positive using PBP2a latex agglutination tests. Population analysis failed to identify heteroresistant subpopulations in uninduced isolates. Identifying the presence of MRSA by PCR directly in the specimens was critical for determining the appropriate course of antimicrobial therapy for the patients. Both infections resolved with non-β-lactam therapy.

Antimicrobial susceptibility of Gram-negative and Gram-positive bacteria collected from countries in Eastern Europe: results from the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) 2004–2010

The Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) commenced in 2004 to longitudinally monitor global changes in bacterial susceptibility to a suite of antimicrobial agents. The current study examined the activity of tigecycline and comparators against isolates collected across Eastern Europe between 2004 and 2010. Minimum inhibitory concentrations were determined using Clinical and Laboratory Standards Institute (CLSI) broth microdilution methodologies. Antimicrobial susceptibility was determined using CLSI interpretive criteria, and tigecycline susceptibility was established using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. This study included 10 295 Gram-negative and 4611 Gram-positive isolates from 42 centres. Extended-spectrum β-lactamases (ESBLs) were reported among 15.3% of Escherichia coli and 39.3% of Klebsiella pneumoniae isolates; the highest rates were observed in Turkey (30.9%) and Bulgaria (53.8%), respectively. Imipenem-non-susceptible K. pneumoniae were identified only in Turkey. ESBL-positive E. coli were highly susceptible to imipenem (95.1%), meropenem (98.0%) and tigecycline (98.5%). Most antimicrobials showed poor activity against Acinetobacter baumannii and Pseudomonas aeruginosa. Vancomycin resistance was noted among 0.9% of Enterococcus faecalis and 11.7% of Enterococcus faecium isolates. High rates of susceptibility were reported for linezolid (99.7%) and tigecycline (100%) against E. faecium. One-quarter of Staphylococcus aureus isolates were meticillin-resistant S. aureus (MRSA), with the highest rate in Romania (51.5%); all MRSA were susceptible to linezolid, tigecycline and vancomycin. Antimicrobial resistance is high in much of Eastern Europe, with considerable variation seen among countries. Tigecycline and the carbapenems retain excellent activity against many pathogens from Eastern Europe; linezolid and vancomycin are active against most Gram-positive pathogens.

Prevalence and resistance of commensal Staphylococcus aureus, including meticillin-resistant S aureus, in nine European countries: a cross-sectional study

Information about the prevalence of Staphylococcus aureus resistance to antimicrobial drugs has mainly been obtained from invasive strains, although the commensal microbiota is thought to be an important reservoir of resistance. We aimed to compare the prevalence of nasal S aureus carriage and antibiotic resistance, including meticillin-resistant S aureus (MRSA), in healthy patients across nine European countries. In this cross-sectional study, nasal swabs were obtained from 32,206 patients recruited by family doctors participating in existing nationwide family doctor networks in Austria, Belgium, Croatia, France, Hungary, Spain, Sweden, the Netherlands, and the UK. Eligible patients were aged 4 years or older (≥ 18 years in the UK) and presented with a non-infectious disorder. Swabs were sent to national microbiological laboratories for identification and isolation of S aureus. Antibiotic resistance testing was done at one central microbiological laboratory. We established the genotypic structure of the isolated MRSA strains with the spa typing method. S aureus was isolated from 6956 (21 · 6%) of 32,206 patients swabbed. The adjusted S aureus prevalence for patients older than 18 years ranged from 12 · 1% (Hungary) to 29 · 4% (Sweden). Except for penicillin, the highest recorded resistance rate was to azithromycin (from 1 · 6% in Sweden to 16 · 9% in France). In total, 91 MRSA strains were isolated, and the highest MRSA prevalence was reported in Belgium (2 · 1%). 53 different spa types were detected-the most prevalent were t002 (n = 9) and t008 (n = 8). The prevalence of S aureus nasal carriage differed across the nine European countries assessed, even after correction for age, sex, and family doctor. Generally, the prevalence of resistance, including that of MRSA, was low. The MRSA strains recorded showed genotypic heterogeneity, both within and between countries. European Commission, 7th Framework Programme(grant agreement 223083).

Effect of habituation to tea tree (Melaleuca alternifolia) oil on the subsequent susceptibility of Staphylococcus spp. to antimicrobials, triclosan, tea tree oil, terpinen-4-ol and carvacrol

The aim of this study was to seek additional data on the antimicrobial susceptibility of Staphylococcus spp. after habituation to low levels of the topical antimicrobial agent tea tree (Melaleuca alternifolia) oil. Meticillin-susceptible Staphylococcus aureus (MSSA), meticillin-resistant S. aureus (MRSA) and coagulase-negative staphylococci (CoNS) were habituated to 0.075% tea tree oil for 3 days. Subsequently, the susceptibility of five isolates each of MSSA, MRSA and CoNS to fusidic acid, mupirocin, chloramphenicol, linezolid and vancomycin was determined by Etest, and susceptibility to tea tree oil, terpinen-4-ol, carvacrol and triclosan was determined by agar dilution. Following habituation to 0.075% tea tree oil, antimicrobial MICs differed between control and habituated isolates on 33 occasions (out of a possible 150), with MICs being higher in habituated isolates on 22 occasions. Using clinical breakpoint criteria, one MSSA isolate changed susceptibility category from vancomycin-susceptible (MIC=2μg/mL) to intermediate susceptibility (MIC=3μg/mL) after habituation in one of two replicates. For the non-antibiotic antimicrobial agents, MICs of habituated and control isolates differed on 12 occasions (out of a possible 120); 10 occasions in MRSA and 2 occasions in MSSA. MICs were higher for habituated isolates on five occasions. However, all the differences were one serial dilution only and were not regarded as significant. Habituation to sublethal concentrations of tea tree oil led to minor changes in MICs of antimicrobial agents, only one of which may have been clinically relevant. There is no evidence to suggest that tea tree oil induces resistance to antimicrobial agents.

Spectrum and potency of ceftaroline tested against leading pathogens causing skin and soft-tissue infections in Europe (2010)

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil, is a novel cephalosporin exhibiting bactericidal activity in vitro against Gram-positive organisms, including meticillin-susceptible Staphylococcus aureus (MSSA), meticillin-resistant S. aureus (MRSA), β-haemolytic streptococci, viridans group streptococci (VGS) and Streptococcus pneumoniae, as well as against many common Gram-negative organisms. The objective of this study was to determine the spectrum and potency of ceftaroline against recent (2010) leading pathogens causing complicated skin and soft-tissue infections (cSSTIs) isolated in Europe. A total of 2438 isolates from the Assessing Worldwide Antimicrobial Resistance and Evaluation (AWARE) programme were identified as cSSTI pathogens. Isolates were collected from patients in 52 medical centres in 19 European countries. Reference susceptibility testing for ceftaroline and commonly used antimicrobials was performed by broth microdilution methodologies. Ceftaroline was very active overall against S. aureus (MIC50/90=0.25/1mg/L) and inhibited 100.0% of isolates at a MIC of ≤2mg/L. Activity against MRSA was documented (MIC50/90=1/2mg/L) but was lower than that observed against MSSA (MIC50/90=0.25/0.25mg/L). Ceftaroline was also very active against 460 β-haemolytic streptococci and 93 VGS (MIC90=0.015mg/L and 0.06mg/L, respectively). Ceftaroline was active against Escherichia coli (MIC50=0.12mg/L) and Klebsiella pneumoniae (MIC50=0.06mg/L) not expressing extended-spectrum β-lactamases, with activity similar to ceftriaxone and ceftazidime. In summary, this study documents the potent in vitro activity of ceftaroline when tested against recent pathogens isolated from patients with cSSTI in Europe.

Antibacterial properties of a pre-formulated recombinant phage endolysin, SAL-1

To evaluate the phage endolysin SAL-1 as a therapeutic agent for Staphylococcus aureus infections, the in vitro and in vivo antibacterial properties of a pre-formulation containing recombinant SAL-1 as an active pharmaceutical ingredient were investigated. The stable pre-formulation (designated SAL200) uniquely included calcium ions and Poloxamer 188 as enhancing and stabilising ingredients, respectively. SAL-1 was successfully produced with no extraneous amino acids by decreasing the culture temperature and was highly purified using a two-step chromatography procedure consisting of ion exchange and hydrophobic interaction chromatography. SAL200 exhibited rapid and effective bactericidal activity against encapsulated and biofilm-forming S. aureus as well as against planktonic S. aureus cells. In addition, SAL200 demonstrated increased effectiveness in the serum environment, with a significantly reduced minimum bactericidal concentration compared with that determined in culture medium. In in vitro antibacterial tests performed against 425 clinical isolates [including 336 meticillin-resistant S. aureus (MRSA) isolates and 1 vancomycin-intermediate S. aureus isolate], collected from 421 patients and four animals, SAL200 exhibited obvious antibacterial activity against all S. aureus isolates tested. Intravenous injection of SAL200 in a mouse model of MRSA infection prolonged the viability of mice and significantly reduced bacterial counts in the bloodstream and splenic tissue. The results presented in this article strongly support SAL200 as a highly potent bactericidal agent against MRSA with an adequate pharmaceutical formulation.