Long-term persistence of a multi-resistant methicillin-susceptible Staphylococcus aureus (MR-MSSA) clone at a university hospital in southeast Sweden, without further transmission within the region.

The objective of this study was to characterise isolates of methicillin-susceptible Staphylococcus aureus (MSSA) with resistance to clindamycin and/or tobramycin in southeast Sweden, including the previously described ECT-R clone (t002) found in Östergötland County, focusing on clonal relatedness, virulence determinants and existence of staphylococcal cassette chromosome (SCC) mec remnants. MSSA isolates with resistance to clindamycin and/or tobramycin were collected from the three county councils in southeast Sweden and investigated with spa typing, polymerase chain reaction (PCR) targeting the SCCmec right extremity junction (MREJ) and DNA microarray technology. The 98 isolates were divided into 40 spa types, and by microarray clustered in 17 multi-locus sequence typing (MLST) clonal complexes (MLST-CCs). All isolates with combined resistance to clindamycin and tobramycin (n = 12) from Östergötland County and two additional isolates (clindamycin-R) were designated as spa type t002, MREJ type ii and were clustered in CC5, together with a representative isolate of the ECT-R clone, indicating the clone's persistence. These isolates also carried several genes encoding exotoxins, Q9XB68-dcs and qacC. Of the isolates in CC15, 83% (25/30) were tobramycin-resistant and were designated spa type t084. Of these, 68% (17/25) were isolated from new-borns in all three counties. The persistence of the ECT-R clone in Östergötland County, although not found in any other county in the region, carrying certain virulence factors that possibly enhance its survival in the hospital environment, highlights the fact that basic hygiene guidelines must be maintained even when MRSA prevalence is low.

Widespread implementation of EUCAST breakpoints for antibacterial susceptibility testing in Europe.

The European Committee on Antimicrobial Susceptibility Testing (EUCAST) was established to harmonise clinical antimicrobial breakpoints and to define breakpoints for new agents in Europe. Data from the European Antimicrobial Resistance Surveillance Network (EARS-Net) external quality assessment (EQA) exercises from 2009 to 2012, from the United Kingdom External Quality Assessment Scheme (UK NEQAS) from November 2009 to March 2013 and data collected by EUCAST through a questionnaire in the first quarter of 2013 were analysed to investigate implementation of EUCAST guidelines in Europe. A rapid change to use of EUCAST breakpoints was observed over time. Figures for implementation of EUCAST breakpoints at the end of the studied period were 61.2% from EARSNet data and 73.2% from UK NEQAS data. Responses to the EUCAST questionnaire indicated that EUCAST breakpoints were used by over 50% of laboratories in 18 countries, by 10 to 50% of laboratories in eight countries and by less than 10% in seven countries. The EUCAST disk diffusion method was used by more than 50% of laboratories in 12 countries, by 10 to 50% of laboratories in ten countries and by less than 10% in eleven countries. EUCAST guidelines implementation is essential to ensure consistent clinical reporting of antimicrobial susceptibility results and antimicrobial resistance surveillance.

Increased risk of venous thromboembolism within the first year after Staphylococcus aureus bacteraemia: a nationwide observational matched cohort study.

OBJECTIVES: Recent evidence suggests that there is an association between infection and venous thromboembolism (VTE). Here, we examined the risk of VTE after Staphylococcus aureus bacteraemia (SAB) compared to the risk in control subjects. DESIGN AND SETTING: Register-based nationwide observational cohort study of hospitalized patients and matched control subjects from the general population in Denmark between 1995 and 2008. RESULTS: Amongst 15 669 SAB cases and 156 690 controls, 182 and 511, respectively, experienced VTE within 1 year. The overall incidence rate (IR) of VTE amongst cases was highest within the first 30 days [IR of deep vein thrombosis (DVT), 39.3 (95% confidence interval (CI) 28.9-53.4)/1000 person-years (PYs); IR of pulmonary embolism (PE), 16.3 (95% CI 10.1-26.2)/1000 PYs]. IRs of DVT were particularly increased amongst cases with a previous diagnosis of VTE, community-acquired infection, a history of injection drug use and in younger age groups. The overall hazard ratio of VTE for cases compared to controls declined from 15.6 (95% CI 10.3-23.5) in the first 30 days after SAB to 4.5 (95% CI 3.2-6.2) from 181 to 365 days after infection. The increased risk of VTE amongst SAB patients persisted after excluding cases with identified VTE risk factors. CONCLUSIONS: There was a particularly high risk of VTE during the first month following an episode of SAB. The risk declined over time, but remained at a threefold increased level compared to control subjects, suggesting that there are shared risk factors for SAB and VTE. Patients with SAB and well-documented risk factors for VTE may benefit from thromboprophylaxis.

Systematic literature analysis and review of targeted preventive measures to limit healthcare-associated infections by meticillin-resistant Staphylococcus aureus.

Meticillin-resistant Staphylococcus aureus (MRSA) is a major cause of healthcare-associated infections in Europe. Many examples have demonstrated that the spread of MRSA within healthcare settings can be reduced by targeted infection control measures. The aim of this systematic literature analysis and review was to summarise the evidence for the use of bacterial cultures for active surveillance the benefit of rapid screening tests, as well as the use of decolonisation therapies and different types of isolation measures. We included 83 studies published between 2000 and 2012. Although the studies reported good evidence supporting the role of active surveillance followed by decolonisation therapy, the effectiveness of single-room isolation was mostly shown in non-controlled studies, which should inspire further research regarding this issue. Overall, this review highlighted that when planning the implementation of preventive interventions, there is a need to consider the prevalence of MRSA, the incidence of infections, the competing effect of standard control measures (e.g. hand hygiene) and the likelihood of transmission in the respective settings of implementation.

Risk factors for Staphylococcus aureus nasal colonization in Danish middle-aged and elderly twins.

Staphylococcus aureus is a human commensal bacterium found in the nasal cavity and other body sites. Identifying risk factors for S. aureus nasal carriage is of interest, as nasal carriage is a risk factor for subsequent invasive infection. We recently investigated the influence of host genetics on S. aureus carriage in Danish middle-aged and elderly twins, which indicated no significant heritability that could account for the observed S. aureus carriage. In the present study, we performed a questionnaire-based study of S. aureus colonization on the same cohort of 2,196 Danish middle-aged and elderly twins to identify specific risk factors for S. aureus nasal colonization, including analyzing the paired twins (n = 478) that were discordant for S. aureus colonization. We found associations between risk factors and S. aureus nasal colonization among middle-aged and elderly twins, including age, male gender, psoriasis, and atopic diseases. Also, present living on a farm is clearly associated with S. aureus colonization, while smoking had a borderline statistically significant protective effect.

Comparison of Rosco Neo-Sensitabs with Oxoid paper disks in EUCAST disk diffusion antimicrobial susceptibility testing on Mueller-Hinton agar.

This study compared Neo-Sensitabs with Oxoid paper disks using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) disk diffusion antimicrobial susceptibility test on Mueller-Hinton agar. The EUCAST-recommended quality control strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212) (Part I) and clinical isolates (Part II) were investigated. In Part I of the study, 27 combinations of antimicrobial agents were tested on four quality control strains repeatedly up to 60 times and zone diameters of tablets and disks were compared. In Part II of the study, 351 clinical isolates were included to cover a broad range of species, as well as resistance mechanisms. In Part I, four major deviations (>1 mm outside quality control ranges) were observed with Neo-Sensitabs. In one case with P. aeruginosa ATCC 27853 (meropenem), there was a corresponding major deviation (2 mm) with the Oxoid disk. The three remaining major deviations with Neo-Sensitabs were observed with meropenem (2 mm) in E. coli ATCC 25922 and with ciprofloxacin (2 mm) and gentamicin (3 mm) in P. aeruginosa ATCC 27853. For Oxoid disks, there were only minor deviations (=1 mm outside quality control ranges) in these three cases. In Part II, there were six discrepancies, susceptible versus resistant, in 3,533 comparisons between the two methods with the clinical isolates. The Rosco Neo-Sensitabs appear to be a possible alternative to Oxoid paper disks for EUCAST disk diffusion antimicrobial susceptibility testing on Mueller-Hinton agar.

Major but differential decline in the incidence of Staphylococcus aureus bacteraemia in HIV-infected individuals from 1995 to 2007: a nationwide cohort study*.

OBJECTIVES: Incidence rates (IRs) of Staphylococcus aureus bacteraemia (SAB) are known to be higher in HIV-infected individuals than in the general population, but have not been assessed in the era of highly active antiretroviral therapy. METHODS: From 1 January 1995 to 31 December 2007, all Danish HIV-infected individuals (n=4871) and population controls (n=92 116) matched on age and sex were enrolled in a cohort and all cases of SAB were registered. IRs and risk factors were estimated using time-updated Poisson regression analysis. RESULTS: We identified 329 cases of SAB in 284 individuals, of whom 132 individuals were infected with HIV and 152 were not [crude IR ratio (IRR) 24.2; 95% confidence interval (CI) 19.5-30.0, for HIV-infected vs. non-HIV-infected individuals]. Over time, IR declined for HIV-infected individuals (IRR 0.40). Injecting drug users (IDUs) had the highest incidence and the smallest decline in IR, while men who have sex with men (MSM) had the largest decline over time. Among HIV-infected individuals, a latest CD4 count <100 cells/µL was the strongest independent predictor of SAB (IRR 10.2). Additionally, HIV transmission group was associated with risk of SAB. MSM were more likely to have hospital-acquired SAB, a low CD4 cell count and AIDS at the time of HIV acquisition compared with IDUs. CONCLUSIONS: We found that the incidence of SAB among HIV-infected individuals declined during the study period, but remained higher than that among HIV-uninfected individuals. There was an unevenly distributed burden of SAB among HIV transmission groups (IDU>MSM). Low CD4 cell count and IDU were strong predictors of SAB among HIV-infected individuals.

Livestock veterinarians at high risk of acquiring methicillin-resistant Staphylococcus aureus ST398.

The prevalence and risk factors associated with livestock-associated MRSA (LA-MRSA) carriage was examined in Danish and Belgian veterinarians. The MRSA and LA-MRSA carriage rates were 9·5% (95% CI 5·3-15·6) and 7·5% (95% CI 3·8-13·1) for MRSA and LA-MRSA, respectively, in Belgium and 1·4% (95% CI: 0·17-5·05) in Denmark (all Danish MRSA isolates belonged to the LA-MRSA genotype). All LA-MRSA isolates were resistant to tetracycline and 53·4% (7/13) showed a multi-resistant phenotype. LA-MRSA was significantly associated with veterinarians in contact with livestock (P=0·046). In the multivariable analysis, working with small animals in a veterinary clinic seems to be negatively associated (OR 0·15, 95% CI 0-1·0, P=0·05) and a strong direct association was found for LA-MRSA acquisition and exposure to live pigs (OR 12·1, 95% CI 1·6-548·5, P=0·01). Since carriage of MRSA ST398 may increase the risk of complications during hospitalization, our results underline that preventive measures may need to be developed for veterinary professionals, particularly for livestock veterinarians.

Farm-specific lineages of methicillin-resistant Staphylococcus aureus clonal complex 398 in Danish pig farms.

The objective of this study was to investigate the genetic diversity of methicillin-resistant Staphylococcus aureus (MRSA) clonal complex (CC) 398 using pulsed-field gel electrophoresis (PFGE). Dust and pigs at five age groups were sampled in six Danish MRSA-positive pig farms. MRSA CC398 was isolated from 284 of the 391 samples tested, including 230 (74%) animal and 54 (68%) environmental samples. PFGE analysis of a subset of 48 isolates, including the six strains previously isolated from farm workers, revealed the existence of farm-specific pulsotypes. With a single exception, human, environmental and porcine isolates originating from the same farm clustered together in the PFGE cluster analysis, indicating that spread of MRSA CC398 in Danish pig farms is mainly due to clonal dissemination of farm-specific lineages that can be discriminated by PFGE. This finding has important implications for planning future epidemiological studies investigating the spread of CC398 in pig farming.

Distribution of fusidic acid resistance determinants in methicillin-resistant Staphylococcus aureus.

The prevalence of resistance to fusidic acid in clinical isolates of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), has increased in the past 2 decades. However, there are limited data regarding the relative importance in this process of the different staphylococcal determinants that mediate resistance to fusidic acid. Furthermore, the roles played by clonal dissemination of fusidic acid-resistant strains versus horizontal transmission of fusidic acid resistance determinants have not been investigated in detail. To gain insight into both issues, we examined fusidic acid resistance in 1,639 MRSA isolates collected in Denmark between 2003 and 2005. Resistance to fusidic acid (MIC, >1 µg/ml) was exhibited by 291 (17.6%) isolates. For the majority of these isolates (∼87%), resistance was attributed to carriage of fusB or fusC, while the remainder harbored mutations in the gene (fusA) encoding the drug target (EF-G). The CC80-MRSA-IV clone carrying fusB accounted for ∼61% of the resistant isolates in this collection, while a single CC5 clone harboring fusC represented ∼12% of the resistant strains. These findings emphasize the importance of clonal dissemination of fusidic acid resistance within European MRSA strains. Nonetheless, the distribution of fusB and fusC across several genetic lineages, and their presence on multiple genetic elements, indicates that horizontal transmission of fusidic acid resistance genes has also played an important role in the increasing prevalence of fusidic acid resistance in MRSA.

Cloning and occurrence of czrC, a gene conferring cadmium and zinc resistance in methicillin-resistant Staphylococcus aureus CC398 isolates.

We recently reported a phenotypic association between reduced susceptibility to zinc and methicillin resistance in Staphylococcus aureus CC398 isolates from Danish swine (F. M. Aarestrup, L. M. Cavaco, and H. Hasman, Vet. Microbiol. 142:455-457, 2009). The aim of this study was to identify the genetic determinant causing zinc resistance in CC398 and examine its prevalence in isolates of animal and human origin. Based on the sequence of the staphylococcal cassette chromosome mec (SCCmec) element from methicillin-resistant S. aureus (MRSA) CC398 strain SO385, a putative metal resistance gene was identified in strain 171 and cloned in S. aureus RN4220. Furthermore, 81 MRSA and 48 methicillin-susceptible S. aureus (MSSA) strains, isolated from pigs (31 and 28) and from humans (50 and 20) in Denmark, were tested for susceptibility to zinc chloride and for the presence of a putative resistance determinant, czrC, by PCR. The cloning of czrC confirmed that the zinc chloride and cadmium acetate MICs for isogenic constructs carrying this gene were increased compared to those for S. aureus RN4220. No difference in susceptibility to sodium arsenate, copper sulfate, or silver nitrate was observed. Seventy-four percent (n = 23) of the animal isolates and 48% (n = 24) of the human MRSA isolates of CC398 were resistant to zinc chloride and positive for czrC. All 48 MSSA strains from both human and pig origins were found to be susceptible to zinc chloride and negative for czrC. Our findings showed that czrC is encoding zinc and cadmium resistance in CC398 MRSA isolates, and that it is widespread both in humans and animals. Thus, resistance to heavy metals such as zinc and cadmium may play a role in the coselection of methicillin resistance in S. aureus.

Semi-selective broth improves screening for methicillin-resistant Staphylococcus aureus.

OBJECTIVES: To evaluate two enrichment broths for methicillin-resistant Staphylococcus aureus (MRSA) detection and compare results with direct plating. METHODS: Swabs from 1224 patients were re-analysed for MRSA in a central laboratory (Münster) using six methods. Swabs were suspended in 0.5 mL of non-selective enrichment broth (NB) and vortexed. Aliquots of 100 microL were inoculated on/into: (I) ChromID MRSA agar; (II) Columbia sheep blood (5%) agar (BA) and ChromID MRSA; (III, IV) NB incubated overnight followed by plating on BA and ChromID MRSA; and (V, VI) a semi-selective broth containing cefoxitin and aztreonam (TSB-SSI) incubated overnight followed by plating on BA and ChromID MRSA. In III-VI, 100 microL of the enriched broth was plated on each agar. RESULTS: The combined MRSA-positive rate was 21.5%. MRSA isolates detected by each method were: TSB-SSI, n = 223; NB, n = 205; BA and ChromID MRSA, n = 203; ChromID MRSA alone, n = 183. TSB-SSI detected more positive throat samples than the comparators and significantly reduced methicillin-susceptible S. aureus (MSSA) growth. The maximum sensitivity obtained was only 85%, possibly due to the study design using pre-used swabs and dilution of swab material. For 997 samples, results from Münster were compared with initial results. Peripheral laboratories identified 172 MRSA compared with Münster where 186, 186 and 204 MRSA were found for direct plating, NB and TSB-SSI broth, respectively. CONCLUSIONS: TSB-SSI was superior to both NB and direct plating on ChromID MRSA and BA. Despite re-using swabs for the study, we showed that routine diagnostic screening could be significantly improved, using a semi-selective enrichment broth.

Methicillin-resistant Staphylococcus aureus (MRSA): burden of disease and control challenges in Europe.

Methicillin-resistant Staphylococcus aureus (MRSA) isa major cause of healthcare- and community-associated infections worldwide. Within the healthcare setting alone, MRSA infections are estimated to affect more than 150,000 patients annually in the European Union (EU), resulting in attributable extra in-hospital costs of EUR 380 million for EU healthcare systems. Pan-European surveillance data on bloodstream infections show marked variability among EU Member States in the proportion of S. aureus that are methicillin-resistant, ranging from less than 1% to more than 50%. In the past five years, the MRSA bacteraemia rates have decreased significantly in 10 EU countries with higher endemic rates of MRSA infections. In addition to healthcare-associated infections, new MRSA strains have recently emerged as community and livestock-associated human pathogens in most EU Member States. The prevention and control of MRSA have therefore been identified as public health priorities in the EU. In this review, we describe the current burden of MRSA infections in healthcare and community settings across Europe and outline the main threats caused by recent changes in the epidemiology of MRSA. Thereby, we aim at identifying unmet needs of surveillance, prevention and control of MRSA in Europe.

EUCAST disc diffusion criteria for the detection of mecA-Mediated ß-lactam resistance in Staphylococcus pseudintermedius: oxacillin versus cefoxitin.

OBJECTIVES: Until recently, the European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommended the cefoxitin disc to screen for mecA-mediated ß-lactam resistance in Staphylococcus pseudintermedius. A recent study indicated that cefoxitin was inferior to oxacillin in this respect. We have re-evaluated cefoxitin and oxacillin discs for screening for methicillin resistance in S. pseudintermedius. METHODS: We included 224 animal and human S. pseudintermedius isolates from Europe (n = 108) and North America (n = 116), of which 109 were mecA-positive. Disc diffusion was performed per EUCAST recommendations using 30-µg cefoxitin and 1-µg oxacillin discs from three manufacturers and Mueller-Hinton agar from two manufacturers. RESULTS: Cefoxitin inhibition zones ranged from 6 to 33 mm for mecA-positive S. pseudintermedius (MRSP) and from 29 to 41 mm for mecA-negative S. pseudintermedius (MSSP). The corresponding oxacillin zone intervals were 6-20 mm and 19-30 mm. For cefoxitin 16% (95% CI 14.8-18.0%) of the isolates were in the area where positive and negative results overlapped. For oxacillin the corresponding number was 2% (1.6-2.9%). For oxacillin a breakpoint of susceptible (S) ≥ 20 mm and resistant (R) <20 mm resulted in only 0.4% and 1.1% very major error and major error rates respectively. CONCLUSIONS: This investigation confirms that the 1-µg oxacillin disc predicts mecA-mediated methicillin resistance in S. pseudintermedius better than the 30-µg cefoxitin disc. For a 1-µg oxacillin disc we propose that 20 mm should be used as cut off for resistance, i.e. isolates with a zone diameter <20 mm are resistant to all ß-lactam antibiotics except those with activity against methicillin-resistant staphylococci.

Emergence and characterization of community-associated methicillin-resistant Staphyloccocus aureus infections in Denmark, 1999 to 2006.

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) infections has changed worldwide. From being strictly nosocomial, MRSA is now frequently found as a community-associated (CA) pathogen. Denmark has been a low-prevalence country for MRSA since the mid-1970s but has in recent years experienced an increasing number of CA-MRSA cases. The aim of this study was to describe the emergence of CA-MRSA infections in Denmark. All Danish MRSA specimens and corresponding clinical data from 1999 to 2006 were investigated. Isolates were analyzed by antibiotic resistance and molecular typing and were assigned to clonal complexes (CC). Clinical data were extracted from discharge summaries and general practitioners' notes, from which assessments of community association were made for all infected cases. CA-MRSA cases constituted 29.4% of all MRSA infections (n = 1,790) and an increasing proportion of the annual numbers of MRSA infections during the study period. CA-MRSA was associated with a young age, skin and soft tissue infections, and non-Danish origin. Transmission between household members was frequently reported. Molecular typing showed >60 circulating clones, where 89.4% of the isolates belonged to five CC (CC80, CC8, CC30, CC5, and CC22), 81.2% carried staphylococcal cassette chromosome mec IV, and 163/244 (69.4%) were positive for Panton-Valentine leukocidin. Clinical and microbiological characteristics indicated that import of MRSA occurs frequently. Resistance to > or =3 antibiotic classes was observed for 48.8% of the isolates. The emergence of CA-MRSA in Denmark was caused by diverse strains, both well-known and new CA-MRSA strains. The results suggest multiple introductions of MRSA as an important source for CA-MRSA infections in Denmark.

Effects of temperature on the detection of methicillin resistance in Staphylococcus aureus using cefoxitin disc diffusion testing with Iso-Sensitest agar.

OBJECTIVES: Cefoxitin is today the substance of choice for the phenotypic detection of methicillin-resistant Staphylococcus aureus (MRSA). We investigated the influence of incubation temperature in the standard range, i.e. 35-37 degrees C, and time, i.e. 18-20 h, versus a full 24 h. METHODS: Cefoxitin disc testing was examined at incubation temperatures of 35 and 36 degrees C and times of 18-20 and 24 h, respectively, for 94 mecA-negative and 49 mecA-positive S. aureus on Iso-Sensitest agar using a semi-confluent inoculum. RESULTS: Cefoxitin inhibition zones on Iso-Sensitest agar were larger at temperatures above 35 degrees C; two isolates (4%, 95% confidence interval=0.5-14%) incubated at 36 degrees C were falsely categorized as susceptible to methicillin. Incubation time across 18-24 h did not impact results. CONCLUSIONS: Detection of methicillin resistance in S. aureus using the cefoxitin disc method with a semi-confluent inoculum on Iso-Sensitest agar is influenced by incubation temperature, and the temperature should not exceed 35 degrees C for the reliable detection of MRSA.

Staphylococcus aureus and hand eczema severity.

BACKGROUND: The role of bacterial infections in hand eczema (HE) remains to be assessed. OBJECTIVES: To determine the prevalence of Staphylococcus aureus in patients with HE compared with controls, and to relate presence of S. aureus, subtypes and toxin production to severity of HE. METHODS: Bacterial swabs were taken at three different visits from the hand and nose in 50 patients with HE and 50 controls. Staphylococcus aureus was subtyped by spa typing and assigned to clonal complexes (CCs), and isolates were tested for exotoxin-producing S. aureus strains. The Hand Eczema Severity Index was used for severity assessment. RESULTS: Staphylococcus aureus was found on the hands in 24 patients with HE and four controls (P < 0.001), and presence of S. aureus was found to be related to increased severity of the eczema (P < 0.001). Patients carried identical S. aureus types on the hands and in the nose in all cases, and between visits in 90% of cases. Ten different CC types were identified, no association with severity was found, and toxin-producing strains were not found more frequently in patients with HE than in controls. CONCLUSIONS: Staphylococcus aureus was present on hands in almost half of all patients with HE, and was significantly related to severity of the disease. This association indicates that S. aureus could be an important cofactor for persistence of HE.

Implications of identifying the recently defined members of the Staphylococcus aureus complex S. argenteus and S. schweitzeri: a position paper of members of the ESCMID Study Group for Staphylococci and Staphylococcal Diseases (ESGS).

BACKGROUND: Staphylococcus argenteus and Staphylococcus schweitzeri, previously known as divergent Staphylococcus aureus clonal lineages, have been recently established as novel, difficult-to-delimit, coagulase-positive species within the S. aureus complex. Methicillin-resistant strains of S. argenteus are known from Australia and the UK. Knowledge of their epidemiology, medical significance and transmission risk is limited and partly contradictory, hampering definitive recommendations. There is mounting evidence that the pathogenicity of S. argenteus is similar to that of 'classical' S. aureus, while as yet no S. schweitzeri infections have been reported. AIM: To provide decision support on whether and how to distinguish and report both species. SOURCES: PubMed, searched for S. argenteus and S. schweitzeri. CONTENT: This position paper reviews the main characteristics of both species and draws conclusions for microbiological diagnostics and surveillance as well as infection prevention and control measures. IMPLICATIONS: We propose not distinguishing within the S. aureus complex for routine reporting purposes until there is evidence that pathogenicity or clinical outcome differ markedly between the different species. Primarily for research purposes, suitably equipped laboratories are encouraged to differentiate between S. argenteus and S. schweitzeri. Caution is urged if these novel species are explicitly reported. In such cases, a specific comment should be added (i.e. 'member of the S.aureus complex') to prevent confusion with less- or non-pathogenic staphylococci. Prioritizing aspects of patient safety, methicillin-resistant isolates should be handled as recommended for methicillin-resistant Staphylococcus aureus (MRSA). In these cases, the clinician responsible should be directly contacted and informed by the diagnosing microbiological laboratory, as they would be for MRSA. Research is warranted to clarify the epidemiology, clinical impact and implications for infection control of such isolates.

Evaluation of four selective agars and two enrichment broths in screening for methicillin-resistant Staphylococcus aureus.

To evaluate methicillin-resistant Staphylococcus aureus detection, we tested in vitro four selective agars and two enrichment broths apart and in combination. Tryptone soya broth with salt, aztreonam, and cefoxitin appeared to be the most sensitive medium. This broth was superior to a phenol red mannitol broth with aztreonam and ceftizoxime.

Epidemiology of European community-associated methicillin-resistant Staphylococcus aureus clonal complex 80 type IV strains isolated in Denmark from 1993 to 2004.

In Europe, community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have been caused predominantly by isolates belonging to the "European CA-MRSA" clone (sequence type 80, staphylococcal cassette chromosome mec type IV). In this study, the epidemiology of European CA-MRSA was investigated on a nationwide scale, covering the period from 1993 to 2004. Denmark has been a low-prevalence country regarding MRSA since the mid-1970s but has experienced an increase in the number of new MRSA cases in recent years. Our results show that European CA-MRSA contributed to this increase. The isolates primarily caused skin and soft tissue infections (SSTIs) in patients outside hospitals, and transmission between household members was the predominant mode of spread. Although some of the isolates were found in hospitalized patients, nosocomial transmission seemed likely in only one instance, pointing to endogenous infections as an important factor. Compared to the CA-MRSA clone most common in the United States (USA300), the European CA-MRSA clone seems less well adapted to persist in hospital environments. Patients with a recent history of travel or family relation to the Mediterranean or Middle East were highly overrepresented. The epidemiological data indicated that the European CA-MRSA isolates were introduced into Denmark on multiple occasions, paralleled by an increasing level of genetic diversity of the isolates found during the study period. European CA-MRSA has previously been described as a rather uniform clone. However, we found pronounced, diverse pulsed-field gel electrophoresis subtypes, staphylococcal protein A gene (spa) types, and susceptibility patterns.