Transmitting Antibiotic-Resistant Bacteria

MRSA is on the rise; © PHIL

Two particular microorganisms cause significant illness and death in hospitals: methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Researchers previously found that 29 percent of patients who acquire these pathogens develop infections or other complications within 18 months.

Researchers conducted a 20-month study of 8,203 patients who had 11,528 stays in eight intensive care units (ICUs). As part of the hospitals' normal protocols, cultures were obtained from all ICU patients when they arrived and every week they stayed to determine the presence of MRSA and VRE.

Fourteen percent of these ICU patients stayed in rooms in which the prior occupant had MRSA and thirteen percent stayed in rooms in which the prior occupant had VRE. Those who stayed in rooms after patients with one of the types of bacteria were more likely to acquire that type of bacteria than those who stayed in rooms following patients who did not test positive for that bacteria (4.5 percent vs. 2.8 percent for VRE and 3.9 percent vs. 2.9 percent for MRSA). The excess risk associated with an infected prior occupant accounted for 5.1 percent of all new cases of MRSA and 6.8 percent of all new cases of VRE.

This additional risk occurred despite the fact that the room cleaning procedures of the hospital in the study exceed national guidelines, indicating that such guidelines do not prevent transmission of disease-causing bacteria. However, the low overall risk among patients exposed to the bacteria "suggests that levels of contamination do not pose a high risk for transmission or that current cleaning methods generally reduce contamination below levels required for transmission," the authors of the study write.

Though the number of cases attributed to previous room occupants was small, this type of transmission could become more common as the prevalence of treatment-resistant bacteria continues to rise.; Source: JAMA and Archives Journals