Bacterial Contamination in Dental Unit Water Lines at Primary Health Care Centers (2022–2023): A Nationwide Study

<b>Background:</b> Dental unit water lines (DUWLs) can harbor microbial contamination, posing risks for cross-infection to patients and dental staff. This study assessed the prevalence of bacterial contamination in DUWLs at primary healthcare centers in Kuwait during 2022-2023 and examined variation by year, governorate, and sampling outlet. <b>Methods:</b> A retrospective cross-sectional analysis was conducted using 3290 water test results from six governorates. Data were obtained from the Environmental Health Department, Ministry of Health, and analyzed using STATA 17. Contamination was defined as a total plate count (TPC) > 100 CFU/mL or presence of coliforms, <i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i>, or fecal streptococci. Descriptive and logistic regression analyses were performed. <b>Results:</b> Overall contamination prevalence was 16.8%. Rates were higher in 2023 (19.8%) than in 2022 (13.7%) and higher in Mubarak Alkabeer governorate (23%) and cup filler outlets (18.9%). Logistic regression showed significantly increased odds of contamination in 2023 (OR = 1.6; 95% CI: 1.3-2.0), Mubarak Alkabeer (OR = 1.4; 95% CI: 1.1-1.9), and cup fillers (OR = 1.3; 95% CI: 1.1-1.6). <i>P. aeruginosa</i> was detected in 1.3% of samples. <b>Conclusions:</b> One in six DUWL samples exceeded Kuwait's strict microbial safety threshold. Findings highlight spatial and procedural variations in contamination and underscore the need for enhanced disinfection protocols, preventive maintenance, and targeted staff training to ensure waterline safety.