Legionella and agar cultures in healthcare facilities waters: a monitoring study in North-East Italy

Abstract

Background Water healthiness is fundamental in medical facilities. Monitoring Legionella spp. and agar cultures concentration is therefore very important. This study looks into these parameters to examine possible criticalities that could need interventions. Methods We collected 399 Legionella and 82 agar cultures withdrawals between November 2019 and February 2020 from 157 detection points (like taps and showers) in 31 structures of four health districts. Withdrawals referred to the 4 quarters of year 2019 (t1, t2, t3, t4). Legionella values were expressed in colony forming units (CFU)/l; agar cultures in CFU/ml. We performed a non-parametric analysis to compare mean values between districts. We used the statistical software package SAS version 9.4 for Windows, setting the significance level at α = 0.05. Results 45% of structures presented at least one positive withdrawal for Legionella (in six we found positivity in more than 1 quarter). Concerning Legionella concentration, we found significant difference between districts in t2 (p = 0.012) and between wards of one district in t3 (p < 0.05). We observed agar positive values in 11 structures (in four cases in more than 1 quarter). In t4 we found a very significant difference (p < 0.0001) between agar values in the four districts, while in t3 we observed a non significant association (p = 0.067). In t3 we found a significant difference for agar values between wards of one district (p = 0.025). We finally considered the simultaneous presence or absence of Legionella and agar positivities: without considering quarters division, we observed accordance (both present or both absent) in 60 detection points, while in 34 points we didn't find it. Conclusions Data provided by this study show that Legionella is rather present in our districts, revealing an association with concentration of CFU in agar. Disinfecting operations should be implemented considering the differences between districts to provide a safe water in every ward. Key messages Water quality monitoring in healthcare facilities is fundamental to provide a safe and healthy environment. Legionella spp. and agar cultures concentrations depend by quarter and spot considered; focused operations should be taken into account to improve disinfection quality.