Epidemiological analysis of methicillin-resistant Staphylococcus aureus ina Zagreb Trauma Hospital using a randomly amplified polymorphic DNA-typingmethod

During a 1-month period in 1996, all inpatients and staff in the Zagreb Tra uma Hospital were screened for methicillin-resistant Staphylococcus aureus (MRSA) carriage in order to control MRSA spread within the hospital. During the study period, 663 patients were admitted to the hospital, and screenin g prior to discharge revealed that 42 were colonised or infected with MRSA, Twenty-three (55%) of these would not have been detected if active screeni ng had not been performed. Amongst 205 staff members, MRSA carriage was onl y found in one (0.5%) nurse. The prevalence and incidence of MRSA carriage varied significantly amongst the wards and was related to the length of hos pital stay. One-third of the patients colonised or infected with MRSA had a history of previous admission to another hospital, and one-third were tran sferred to another institution after discharge. Thirty-nine of 42 MRSA isol ates shared the same antibiotic sensitivity pattern, suggesting endemic spr ead of MRSA. However, randomly amplified polymorphic DNA molecular typing r evealed four profiles, the most common involving 15 of 36 tested strains. T here was no obvious clustering of epidemiological types by ward, except for the appearance of a single type on the burns unit, and it was likely that different strains had been introduced into the hospital by patient transfer s from elsewhere. The results of this study indicate that a substantial pro portion of MRSA carriers escape infection control measures if active screen ing is not performed. Based on the results of this study, steps have been t aken to improve interhospital communication about the transfer of patients colonised with MRSA. Randomly amplified polymorphic DNA typing proved to be a useful aid to epidemiological investigations of MRSA.