Polymerase chain reaction fingerprints of methicillin-resistant Staphylococcus aureus clinical isolates in Greece are related to certain antibiotypes

Molecular fingerprinting of meticillin-resistant Staphylococcus aureus strains isolated from patients and staff of two Iranian hospitals

Meticillin-resistant Staphylococcus aureus (MRSA) is an important cause of hospital-acquired infection. Methods for typing and epidemiological investigation of MRSA isolates have an important impact in detection of MRSA strains, source, transmission and control of these micro-organisms. The aims of this study were to study molecular diversity of MRSA isolates by randomly amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR), the surveillance efficacy of this method and determination of antibiotic resistance patterns of MRSA isolates. MRSA isolates were collected from clinical specimens and noses of 460 staff and inpatients admitted to Imam Khomeini and Paediatric Hospitals during a six-month period (2004-2005). Eighty MRSA strains, in which the presence of mecA gene had been confirmed by PCR, were subjected to RAPD-PCR using five primers and the results were summarised in a dendrogram to show the relationships between the test isolates. Antibiotic resistance patterns of MRSA isolates were also determined by disc agar diffusion method using 13 antibiotic discs according to Clinical and Laboratory Standards Institute guidelines. Forty-three RAPD-PCR profiles were detected. The test isolates were clustered into 18 taxa with 50% similarity, indicating the heterogeneity of our test isolates. MRSA isolates fell into 41 antibiotic resistance patterns. There was correlation between antibiotic resistance patterns and results of RAPD-PCR. Most of the MRSA isolates were multi-resistant.

Pulse-field gel electrophoresis typing of methicillin-resistant Staphylococcus aureus strains susceptible to aminoglycosides isolated from 1993 to 2002

Methicillin-resistant Staphylococcus aureus (MRSA) susceptible strains to aminoglycosides (AS-MRSA) have been increasingly isolated in the Albert Cheneiver Hospital during the past 10 years. The aim of this study was first, to analyse the genotypes and the profiles of resistance to antibiotics and second to compare the AS-MRSA with the MRSA resistant to gentamicin (GR-MRSA) and with MRSA resistant to kanamycin and tobramycin, but susceptible to gentamicin (GS-MRSA), previously studied in our laboratory. All the AS-MRSA consecutively isolated from clinical samples (carriage isolates excluded) from 01/01/1993 to 31/12/2002 (33 isolates) were typed by DNA macrorestriction. Their susceptibilities to other anti-staphylococcal drugs (erythromycin, lincomycin, tetracycline, rifampicin, fusidic acid and fosfomycin) were studied by the French standard disk method. The 33 strains showed a heterogeneous resistance to oxacillin and fell into five phenotypes. The main phenotype (51.5% of the AS-MRSA strains) was susceptible to the six antibiotics studied. DNA macrorestriction defined 24 genotypes (percentage similarity <80%). Among them 16 genotypes contained only one strain each, and none contained more than three isolates. Conversely the comparison with GR-MRSA and GS-MRSA isolated during the same period showed that the strains were not closely linked. The diversity of our isolates showed that it was not an epidemic phenomenon, in contrast to the results of similar studies. Our findings may be explained by the patients coming mostly from different hospital units. This work indicates the need for further studies on the genome, to determine whether AS-MRSA have derived from strains that occurred before aminoglycosides came into clinical use.