What are the microbial burden and potential pathogens on hospital surfaces before and after cleaning?

Healthcare-associated infections (HCAIs) remain a significant challenge in hospitals, with environmental contamination increasingly recognized as a contributing factor. However, the relationship between surface microbial burden, pathogen presence, and the effectiveness of cleaning interventions remains incompletely understood. This study aimed to describe the microbial contamination of hospital surfaces before and after cleaning, evaluate the impact of an educational intervention targeting environmental services (EVS) staff, and assess the relevance of two cleanliness thresholds (4 CFU/cm 2 and 2.5 CFU/cm 2 ) for predicting pathogen presence. A prospective study was conducted over a 5-month period across 10 wards in a 1,600-bed university hospital. Surface contamination was assessed weekly using contact agar plates to sample 15 high-touch surfaces and floors in randomly selected rooms, both before and after routine cleaning. Cleaning performance was concurrently monitored using fluorescent markers. In addition, a 2-day training program was delivered to 50% of EVS staff. Microbial burden (CFU/cm 2 ), the prevalence of contaminated surfaces, and the presence of clinically relevant pathogens were analyzed. A total of 736 samples were collected. Cleaning significantly reduced the overall microbial burden (mean 1.05 vs. 0.75 CFU/cm 2 , p < 0.001) and pathogen prevalence (19.0% vs. 13.1%, p = 0.03). Floors were the most frequently contaminated surfaces, whereas high-touch surfaces exhibited lower contamination rates. Pathogen presence was strongly associated with higher bioburden: 53% vs. 10% for surfaces with >4 CFU/cm 2 compared with those with ≤ 4 CFU/cm 2 , and 56.3% vs. 5.9% for surfaces with >2.5 CFU/cm 2 compared with those with ≤ 2.5 CFU/cm 2 ( p < 0.0001 for both). The educational intervention significantly improved cleaning compliance as assessed using fluorescent markers (40.3% vs. 62.8%, p < 0.001), though reductions in overall bioburden were not statistically significant. In this study, we found that a substantial proportion of hospital surfaces remained contaminated with pathogens even after routine cleaning. Lower microbial thresholds, particularly a threshold of 2.5 CFU/cm 2 , may be relevant indicators of cleanliness for high-touch surfaces. Targeted training improved cleaning practices and showed a trend toward bioburden reduction, highlighting the importance of structured interventions in HCAI prevention strategies.