Microbial Surveillance Conducted for Infection Control at a Hospital

For infection control purposes,we conducted microbial surveillance targeting the air,floors,and sinks at approximately 250 locations from 1999 to 2004.Annual changes in the average number of microbial isolates from air,floor,and sink samples were not correlated but changes in particular sampling items were correlated.Hospital wards where there was greater movement of people produced larger average numbers of isolates than other parts of the hospital,for example examination rooms.We found that the average number of isolates from air and floor samples was higher when a new hospital ward was under construction as well as just after its opening.Methicillin-resistant Staphylococcus aureus (MRSA) was frequently isolated from floor samples (68.8%) and Pseudomonas aeruginosa was isolated from both floor (10.3%) and sink (89.7%) samples.The numbers of MRSA and Pseudomonas aeruginosa isolated from hospital ward samples were larger than those from other parts of the hospital.Our microbial surveillance clearly showed that the distribution of environmental bacteria changed in the hospital overall rather than for individual units and was affected by human activity and environmental changes.Furthermore,the species of bacteria isolated from the air,floor,and sink samples were different.Therefore,our results suggest that it is important to address the sanitization of the hospital environment as a whole,not on a ward by ward basis.