Methicillin resistant Staphylococcus aureus strains in the greater Dusseldorf area

Over a period of three years the incidence of methicillin resistant Staphylococcus aureus (MRSA) isolates in II hospitals in the greater Dusseldorf area was observed. From a total of 7,814 S. aureus isolates, 489 (6.3%) were methicillin resistant. From 198 different patients, MRSA first isolates and 291 second isolates could be cultured. Methicillin resistance among all S. aureus isolates from 11 hospitals in the greater Dusseldorf area, ranged from 0.5 to 7.8% dependant on the size of the hospital. The highest incidence (7.8%) was found in a 1,500 bed hospital and the lowest incidence in a smaller 200 bed hospital (0.5%). With respect to the distribution among clinical departments the highest incidence of MRSA isolates was found on intensive care units and surgical wards, 25.5% and 13.0% respectively. The commonest specimen from which the MRSA isolates were cultured were respiratory secretions (17.6%) followed by central venous catheter tips (12.8%). In terms of the drug resistance pattern: all isolates were resistant to the aminoglycosides and gyrase inhibitors, whereas between 80% and 90% were sensitive to fusidic acid, chloramphenicol and pyrimethamine-sulfamethoxazole. All the strains were sensitive to the glycopeptide antibiotics, vancomycin and teicoplanin. Strain typing of 181 available first isolates (from a total of 198 first isolates) by PFGE and phage lysotyping produced identical results in more than 90% of all cases. Twenty-eight different MRSA strain types were identified by PFGE and in total 23 lysotypes could be determined. During the period of investigation an increased incidence of MRSA on an intensive care unit was observed, in which a total of 204 MRSA (42% of the total number) were isolated. The strain typing using both methods showed that on that ICU eight different MRSA types were involved in this outbreak. A hygiene plan was implemented on the unit with considerable success in reducing the incidence and spread of MRSA.