Looking back, current status, and future trends of MRSA clones in Italy
Abstract number: P1426
Campanile F., Bongiorno D., Borbone S., Mongelli G., Jeddari S., Stefani S.
Objectives: Our aims were i) to track the epidemiology of meticillin-resistance in Italy, studying the spread and prevalence of various MRSA clones over two decades; ii) to document MRSA changes in the phenotypic and genotypic features, and their shifts in the levels of susceptibility to glycopeptides; iii) to trace the origin of MRSA lineages in Italy comparing the genotypic backgrounds of contemporary isolates, with those of a sample of early MRSA strains from 1980.
Methods: Two hundred fifty-eight non-repetitive MRSA clinical isolates from various Italian hospitals between 1991 and 2006 were analysed for their antibiotic resistance, and typed by PFGE and SCCmec typing. All strains were grouped into clonal types, and representative isolates of the main clones were further characterised by MLST, generating the corresponding sequence type (ST)-SCCmec types for each MRSA genotype. A sample of twenty early MRSA strains from 1980 was also used for comparison.
Results: The most interesting feature was the increase of the Italian clone (ST228-I; PFGE E) over the last decade (from 27% during the first decade, to 70% during the second one), and its stability over this time; associated with the replacement of the multi-drug resistant and highly epidemic Iberian clone (ST247-I/IA; PFGE A), (46% during the first decade to 5% during the second one). The Rome clone (ST247-I/IA; PFGE C), one of the major local clones in the first decade (11%), has almost disappeared. ST1, ST15 and ST30 were the predominant earliest MLST types among the MRSA strains in 1980, carrying the first described SCCmec I, in which resistance to antibiotics, other than b-lactams, was very rare. A temporal shift in the susceptibility levels to glycopeptides was observed: vancomycin MIC90 value increased two fold from 1980 to 2006 (0.52 mg/L), while teicoplanin increased from 0.12 to 48 mg/L.
Conclusions: We describe the change of multi-resistance MRSA clones, which occurred in hospitals from 1991 to 2006, and the increase of the glycopeptide MIC levels, reflecting a worldwide trend, due to the abuse of such molecules in clinical therapy. We document the detection of ST1, ST15, and ST30 in the earlier isolates; we hypothesises a possible correlation of these strains with the current C-MRSA clones.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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