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| | For now: this is from http://www.rivm.nl/earss/Images/EARSS%202007_FINAL_tcm61-55933.pdf | | For now: this is from http://www.rivm.nl/earss/Images/EARSS%202007_FINAL_tcm61-55933.pdf |
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| - | =Staphylococcus aureus=
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| - | ==Clinical and epidemiological importance==
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| - | Staphylococcus aureus is a gram-positive bacterium that colonizes the skin of about 30% of healthy
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| - | humans. Although mainly a harmless coloniser, S. aureus can cause severe infection. Its oxacillinresistant
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| - | form (methicillin-resistant S. aureus, MRSA) is the most important cause of antibioticresistant
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| - | health care-associated infections worldwide (26). Since health care-associated MRSA
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| - | infections add to the number of infections caused by methicillin-susceptible S. aureus, a high incidence
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| - | of MRSA adds to the overall burden of infections caused by this species in hospitals (20). Moreover,
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| - | infections with MRSA may result in prolonged hospital stay and in higher mortality rates (7), owing
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| - | mainly to the increased toxicity and limited effectiveness of alternative treatment regimens. MRSA
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| - | is currently the most commonly identified antibiotic-resistant pathogen in hospitals in many parts of
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| - | the world, including Europe, the Americas, North Africa and the Middle- and Far-East.
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| - | ==Resistance mechanisms==
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| - | S. aureus acquires resistance to methicillin and all other beta-lactam antibiotics through expression
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| - | of the exogenous mecA gene, that codes for a variant penicillin binding protein PBP2’ (PBP2a) with
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| - | low affinity to beta-lactams, (21), thus preventing the drug induced inhibition of cell wall synthesis.
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| - | The level of methicillin resistance (defined by its minimum inhibitory concentration, MIC) depends
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| - | on the amount of PBP2’ production, which is influenced by various genetic factors. Resistance levels
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| - | of mecA-positive strains can thus range from phenotypically susceptible to highly resistant (5). Upon
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| - | challenge with methicillin, a population of a heterogeneously resistant MRSA strain may quickly be
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| - | outgrown by a subpopulation of highly resistant variants.
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| - | Glycopeptide antibiotics include vancomycin and teicoplanin. Both are very large molecules that
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| - | through binding to the terminal amino acid residues (D-alanyl-D-alanine) of the peptide side chains
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| - | in the growing peptidoglycan polymers inhibit the cross linking essential for cell wall stability. It is
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| - | estimated that to block cell wall synthesis effectively, the glycopeptide antibiotic has to penetrate
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| - | about 20 peptidoglycan layers, all with free D-alanyl-D-alanine targets, without being ‘trapped’,
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| - | and this together with a poor penetration into infected tissues, limits the therapeutic effects of glycopeptides.
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| - | Cell wall thickening of S. aureus thus increases its ability to resist vancomycin, and in S.
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| - | aureus most strains with reduced vancomycin susceptibility have a markedly thicker cell wall (21).
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| - | Vancomycin resistance is far more prevalent among enterococci, owing to different genetic resistance
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| - | determinants.
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| - | ==Staphylococcus aureus resistance trends: 1999-2007==
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| - | ===Beta-lactams===
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| - | In 2007, 31 countries reported AST results of 31,591 invasive S. aureus isolates to EARSS, of which
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| - | 22% (n=7,115) were identified as MRSA. At least thirty-eight percent (n=2,736) of these MRSA
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| - | isolates were confirmed by oxacillin MIC, PCR mecA-gene, or PBP2A-agglutination.
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| - | MRSA proportions vary from 0% in the north to over 50% in southern European countries. Thirteen
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| - | countries reported MRSA proportions equal or higher than 25%. Like previous years, all Mediterranean
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| - | countries, Romania, the United Kingdom and Ireland were included in this category. In the
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| - | UK, yet another year of decreasing MRSA proportions turned the increasing trend that prevailed
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| - | until 2006 into a decrease, although this finding was not found by the subset analysis of laboratories
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| - | that consistently provided data for the entire EARSS observation period (9 years). In France, Turkey
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| - | and Slovenia, the MRSA proportions are still on the decrease and for the first time in 2007 proportions
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| - | in Austria, Bulgaria and Italy also showed a significant decrease (not confirmed for the subset
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| - | laboratories in Austria and Italy). Significant increases reported in 2006 continued in 2007 in Czech
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| - | Republic, Hungary and Germany (Figure 4.8).
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| - | Four countries had MRSA proportions over 40%, of which Portugal and Malta still show a continuing
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| - | increase. In Greece, like last year, the subset laboratories showed a significant decrease, which
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| - | was not confirmed by the overall trend. The same holds for an increase in Spain. These differences
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| - | between the total and the subset laboratories are caused by changes in the national EARSS participation
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| - | over the years.
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| - | In the northern part of Europe, MRSA rates are below 3%, except for the Baltic States (8%-9%). In
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| - | Latvia, MRSA rates continue to decrease strongly, from 25% in 2004 to 8% in 2007. However, in the
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| - | Netherlands, Finland and Denmark a significant increase was reported, although in Denmark not in
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| - | the subset laboratories. The MRSA rates of Estonia, Iceland, Norway and Sweden remain relatively
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| - | stable. In Belgium, the decrease of 2006 was maintained, although not (yet) reflected as statistically
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| - | significant trend (Figure 4.9).
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| - | ===Glycopeptides/vancomycin===
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| - | Overall, four confirmed VISA’s and no VRSA were reported to the EARSS database in 2007.
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| - | Vancomycin intermediate resistant S. aureus were reported by France (n=1), Ireland (n=1) and The
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| - | Netherlands (n=2).
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| - | ==MRSA by hospital department==
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| - | S. aureus susceptibility data reported to EARSS originate from different hospital departments. Across
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| - | the national EARSS networks, an average of 12% (min. 2%, max.26%) of the invasive S. aureus isolates
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| - | was isolated from ICU patients. MRSA strains are more frequently isolated from ICU patients
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| - | than non-ICU patients, and therefore country-specific differences in enrolment can be of influence on
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| - | the comparability of the overall MRSA proportions.
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| - | In 22 of 30 countries the MRSA proportions in ICU were higher compared to non-IC units; for twelve
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| - | countries this difference was significant. In six countries, the MRSA proportions in ICU-isolates
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| - | were lower than in the non-ICU isolates. Two countries had no MRSA isolates at all (Figure 4.10).
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| - | In six countries, Croatia, Greece, Israel, Malta, Portugal, Turkey, the proportion of MRSA found
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| - | among ICU patients was over 60%. Although in these counties, except for Malta, the MRSA proportions
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| - | in ICUs were significantly higher compared to non-IC units, these high levels go together
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| - | with high rates of MRSA, above 30%. However, high specialisation of ICU’s with very vulnerable
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| - | patients could have been of influence.
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| - | ==Conclusions==
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| - | MRSA is still an increasing problem all over Europe. In a number of low-endemic countries increasing
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| - | MRSA proportions are found. In the high endemic countries, on the other hand, some countries seem
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For now: this is from http://www.rivm.nl/earss/Images/EARSS%202007_FINAL_tcm61-55933.pdf
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