Methicillin-resistant Staphylococcus aureus: Risk factors of infection/colonisation and clonal heterogeneity in an intensive care unit.

Purpose: The aim of this study was to determine the risk factors associated with colonisation/infection by methicillin-resistant Staphylococcus aureus (MRSA) and to demonstrate the chain of infections by genotyping of all MRSA isolates. Methods: A total of 6143 microbiological samples from 1753 patients was obtained at a surgical ICU of Frankfurt University hospital during 1995. Results: MRSA was detected in 1.6% of patients and three members of staff (3.3%). Typing of these 31 MRSA-strains (first isolates) by macrorestriction analysis of chromosomal DNA revealed nine different genotypes. More than 60% of all isolates belonged to one type that was confirmed to be closely related to the "South Germany" epidemic strain. A strong correlation between severity of underlying disease and length of hospitalisation on the one hand and detection of MRSA on the other could be demonstrated. Detection of MRSA was significantly more common in patients with adult respiratory distress syndrome (ARDS), sepsis, kidney failure, prolonged respiratory treatment and in patients with prolonged phases of haemodynamic instability. It appeared that the mortality rate of MRSA-infected patients was higher (28.6%) than the mortality rate of all patients (6.5%). Conclusion: Following of a strict hygiene regime is important to prevent clonal spread of MRSA and especially to protect immunocompromised patients from complicating infections.