To What Extent Does Environmental Cleaning Affect Contamination Levels?


The role of the hospital environment as a reservoir of infection is poorly understood. Therefore, baseline levels of methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile contamination on surfaces in an ICU ward need to be determined. Researchers from Edinburgh Napier University, the Royal Infirmary of Edinburgh, and the University of Edinburgh, in Edinburgh, UK, sought to determine whether contamination differs at certain times of the day, if recovery of pathogens is influenced by total background contamination and to what extent cleaning affects contamination levels.

Sampling occurred in an 18-bed ICU ward on regular days for one month. Surfaces were sampled from patient and non-patient areas, morning and afternoon, to detect total viable counts (TVC), MRSA and C. difficile using contact plates and swabs. Multi-locus variable number tandem repeat fingerprinting (MLVF) was performed on selected isolates to determine relationship of MRSA from patients and environment. Statistical analyses were carried out using non-parametric tests.

Ram, et al. showed that MRSA was recovered from 32 percent of surfaces and C. difficile recovered from 27 percent of surfaces. All surfaces tested were contaminated with no significant difference in TVC regardless of time of sampling. MLVF data suggested transfer of MRSA from patient to environment rather than the converse.

The researchers say that cleaning was scheduled in the morning however, whether surfaces were re-contaminated after cleaning or whether cleaning was ineffective remains to be established and requires more investigation. Therefore bacteria were detected throughout the surveillance period providing data on baseline levels of MRSA and C. difficile on surfaces. Bacterial contamination remains at easily detectable levels despite regular cleaning so ward cleaning protocols may need to be revised.

Their research was presented at the International Conference on Prevention & Infection Control (ICPIC) held in Geneva, Switzerland, June 29 through July 2, 2011.

Reference: A Ram, AP Gibb, K Templeton, A Holmes, D Swann, CM Taylor. Recovery of MRSA and Clostridium difficile in an ICU Ward. Presentation at International Conference on Prevention & Infection Control (ICPIC). BMC Proceedings 2011, 5(Suppl 6):P185

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