Decline in the rates of meticillin-resistant Staphylococcus aureus acquisition and bacteraemia in a general intensive care unit between 1996 and 2008.

Analysis of admission and weekly screening and other cultures for meticillin-resistant Staphylococcus aureus (MRSA) taken in the intensive care unit (ICU) demonstrated a 75% reduction in the estimated rate of acquisition of MRSA between 1996 and June 2008. Four periods were defined by three events: a new ICU (December 1997); addition of a two-bed bay (January 2001); and extra infection control measures in ICU and the hospital generally, including screening of all admissions (December 2006). In ICU, acquisition/1000 bed-days decreased promptly in each successive period, 49.0 (34.4-63.6), 28.3 (21.7-34.9), 19.3 (16.3-22.3) and 11.8 (7.3-16.3) respectively, and MRSA bacteraemias/1000 bed-days decreased between the last three periods, 7.6 (4.7-10.5), 3.7 (2.6-4.8) and 0.4 (0-2.9) with no change in the proportion colonised progressing to bacteraemia and a small increase in the rate of other bacteraemias. From December 2006 prevalence of MRSA in admissions to ICU from general wards decreased from 13.5% (11.6-15.4) to 6.4% (4.0-8.8) consequent upon a reduction in estimated pre-ICU acquisition rate from 26.0 (22.7-29.3) to 9.4 (6.0-12.8)/1000 bed-days. These results suggest that the improved environment of the new ICU and its extension and the recent changes in infection control each contributed to the observed reductions in MRSA acquisition and subsequent bacteraemia within ICU. Improved infection control in the hospital was associated with decreased acquisition of MRSA on the general wards.