Despite strict measures for decontamination of ICU rooms, antibiotic-resistant bacteria (such as methicillin-resistant Staphylococcus aureus [MRSA] or vancomycin-resistant enterococci [VRE]) can still be passed from one ICU occupant to the next. Experts examined weekly cultures from 11,528 patients admitted to ICUs over almost 2 years. Of these patients, 14.3% were exposed to MRSA through rooms previously occupied by carriers of the pathogen, 12.5% to VRE. Respectively, 3.9% and 4.5% of exposed patients became positive as MRSA and VRE carriers themselves, a slight increase over patients who weren't exposed through a prior ICU occupant, of which 2.9% became positive for MRSA and 2.8% for VRE. This route of transmission is estimated to be responsible for less than 10% of ICU cases, but could be a more serious concern as these organisms become more widespread.

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