Molecular epidemiology of MRSA in 13 ICUs from eight European countries

OBJECTIVES

The European epidemiology of MRSA is changing with the emergence of community-associated MRSA (CA-MRSA) and livestock-associated MRSA (LA-MRSA). In this study, we investigated the molecular epidemiology of MRSA during 2 years in 13 ICUs in France, Greece, Italy, Latvia, Luxemburg, Portugal, Slovenia and Spain.

METHODS

Surveillance cultures for MRSA from nose and wounds were obtained on admission and twice weekly from all patients admitted to an ICU for ≥3 days. The first MRSA isolate per patient was genotyped in a central laboratory by MLST, spa typing, agr typing and SCCmec (sub)typing. Risk factors for patients with an unknown history of MRSA colonization were identified.

RESULTS

Overall, 14 390 ICU patients were screened, of whom 8519 stayed in an ICU for ≥3 days. Overall MRSA admission prevalence was 3.9% and ranged from 1.0% to 7.0% for individual ICUs. Overall MRSA acquisition rate was 2.5/1000 patient days at risk and ranged from 0.2 to 8/1000 patient days at risk per ICU. In total, 557 putative MRSA isolates were submitted to the central laboratory for typing, of which 511 (92%) were confirmed as MRSA. Each country had a distinct epidemiology, with ST8-IVc (UK-EMRSA-2/-6, USA500) being most prevalent, especially in France and Spain, and detected in ICUs in five of eight countries. Seventeen (3%) and three (<1%) isolates were categorized as CA-MRSA and LA-MRSA, respectively. Risk factors for MRSA carriage on ICU admission were age >70 years and hospitalization within 1 year prior to ICU admission.

CONCLUSIONS

The molecular epidemiology of MRSA in 13 European ICUs in eight countries was homogeneous within, but heterogeneous between, countries. CA-MRSA and LA-MRSA genotypes and Panton-Valentine leucocidin-producing isolates were detected sporadically.

Staphylococcus aureus spa type t437: identification of the most dominant community-associated clone from Asia across Europe

Methicillin-resistant Staphylococcus aureus (MRSA) belonging to the multilocus sequence type clonal complex 59 (MLST CC59) is the predominant community-associated MRSA clone in Asia. This clone, which is primarily linked with the spa type t437, has so far only been reported in low numbers among large epidemiological studies in Europe. Nevertheless, the overall numbers identified in some Northern European reference laboratories have increased during the past decade. To determine whether the S. aureus t437 clone is present in other European countries, and to assess its genetic diversity across Europe, we analysed 147 S. aureus t437 isolates from 11 European countries collected over a period of 11 years using multiple locus variable number tandem repeat fingerprinting/analysis (MLVF/MLVA) and MLST. Additionally 16 S. aureus t437 isolates from healthy carriers and patients from China were included. Most isolates were shown to be monophyletic with 98% of the isolates belonging to the single MLVA complex 621, to which nearly all included isolates from China also belonged. More importantly, all MLST-typed isolates belonged to CC59. Our study implies that the European S. aureus t437 population represents a genetically tight cluster, irrespective of the year, country and site of isolation. This underpins the view that S. aureus CC59 has been introduced into several European countries, not being restricted to particular geographical regions or specific host environments. The European S. aureus t437 isolates thus bear the general hallmarks of a high-risk clone.

arcA, the regulatory gene for the arginine catabolic pathway in Aspergillus nidulans

We have cloned and analysed the arcA gene which encodes a transcriptional activator necessary for the high-level expression of two genes for enzymes of the arginine catabolic pathway in Aspergillus nidulans: agaA (for arginase) and otaA (for ornithine transaminase, OTAse). Here we present complete genomic and cDNA sequences for, and describe the pattern of expression of, the arcA gene. This gene contains one intron and encodes a polypeptide of 600 amino acids. The deduced protein belongs to the family of Zn(2)Cys(6) fungal regulatory proteins. ARCA is the first known protein of this family that has glycine instead of the conserved proline at the fifth position in the second, six-residue, loop of the Zn cluster domain. We have established that transcription of the arcA gene is not self-regulated and does not depend on arginine. Two mutations in arcA, one gain-of-function and one loss-of-function, have been sequenced and the effects of these mutations on the expression of the agaA gene at the transcriptional level are reported.

Structure of the arginase coding gene and its transcript in Aspergillus nidulans

The arginase structural gene (agaA) from Aspergillus nidulans has been cloned and characterised. Depending on the growth conditions of the mycelium, transcripts of this gene have different 5'ends. These differences could result either from the presence of multiple transcription initiation sites or from differential processing of mRNA. The agaA mRNA has a long 5'UTR with a potentially complex secondary structure. Putative arginine binding aptamers were found in this UTR suggesting interesting possibilities for regulation of the agaA expression.

Structure of the arginase coding gene and its transcript in Aspergillus nidulans

The arginase structural gene (agaA) from Aspergillus nidulans has been cloned and characterised. Depending on the growth conditions of the mycelium, transcripts of this gene have different 5'ends. These differences could result either from the presence of multiple transcription initiation sites or from differential processing of mRNA. The agaA mRNA has a long 5'UTR with a potentially complex secondary structure. Putative arginine binding aptamers were found in this UTR suggesting interesting possibilities for regulation of the agaA expression.

Aspergillus nidulans 5S rRNA genes and pseudogenes

The sequence of four Aspergillus nidulans 5S rRNA genes and of two pseudogenes has been determined. A conserved sequence about 100 bp upstream of the 5S rRNA coding sequences has been found in three genes and one pseudogene. The two pseudogenes correspond to the 5' half of the 5S rRNA coding sequence and their 3' flanking sequences which are not homologous to 5S rRNA are strongly conserved.