Antibiotic use is associated with resistance of environmental organisms in a teaching hospital

An intensive care unit (ICU), acute stroke unit (ASU) and medical day bed unit (MDBU) underwent a standardized four-month environmental screening programme. The aim was to examine environmental organisms from these wards and compare bacterial resistances in association with antimicrobial usage. Hand-touch and other sites were screened using commercial dip-slides, and staff were asked to provide fingertip cultures. Patient blood isolates were retained throughout the study. Organisms were quantitatively and qualitatively assessed including antimicrobial susceptibility testing. Antibiotic consumption data in defined daily doses/1000 patient-days were obtained for each unit for the previous year. Two hundred and seventy-six staphylococci and 67 Gram-negative bacilli were recovered. Antibiotic resistance was significantly associated with individual wards for staphylococci (P<0.0001) and coliforms (P=0.04), and trends were also demonstrated for other Gram-negative organisms (P=0.06) despite fewer numbers. Antibiotic consumption on the ICU was six-fold higher than on the ASU and MDBU. Associations were found between consumption of selected antibiotic groups and corresponding resistances among staphylococci and Gram-negative bacilli. Antibacterial resistance was the only significant difference between environmental bacteria from different wards, and appeared to reflect prescribing pressure. Visual inspection of a ward may not provide a reliable guide regarding the presence of multi-resistant organisms in the hospital environment or the potential risk of infection. These findings have implications for local antibiotic policies, infection control and cleaning schedules.