Multi-Year Assessment of Bacterial Contamination on Hand Sanitizer Dispensers at a Community College in Queens, New York: Microbial Contamination of Hand Sanitizer Dispensers

James Timbilla, Cheeryll Meddles-Torres and Gheorghe Proteasa

Background and Objective: Hand sanitizer dispensers (HSDs) are widely used in institutional settings to reduce pathogen transmission; however, their external surfaces may serve as reservoirs for microorganisms due to repeated user contact. This study aimed to characterize microbial contamination on HSDs across a multi-year period at Queensborough Community College, New York and assess associations between dispenser use and contamination levels. Materials and Methods: The HSDs were sampled in ten campus buildings during Fall 2013 (n = 42) and Fall 2014 (n = 42), with targeted follow-up sampling in three buildings during Spring 2016 (n = 15) and two locations in Summer 2023 (n = 8). Sterile swabs were used to collect samples from dispenser surfaces, which were cultured on Tryptic Soy Agar and evaluated using a semi-quantitative growth scale (0-4). Representative isolates underwent Gram staining and morphological characterization, with 2023 isolates identified to species level using MALDI-TOF mass spectrometry. Growth scores were summarized as Mean±SD and Fisher’s exact test assessed sanitizer status vs. contamination (p<0.05). Results: Microbial growth was detected on HSDs in 80% of buildings in 2013 and 90% in 2014, with mean contamination scores ranging from 0.3-2.0 and 0.5-2.7, respectively. The Administration and Art buildings exhibited the highest contamination levels. All characterized isolates were Gram-positive bacteria, including Staphylococcus warneri and Priestia flexa. No statistically significant association was observed between sanitizer fill status and contamination level (Fisher’s exact test: 2013, p = 0.14; 2014, p = 0.70). Conclusion: The HSDs in college environments can harbor predominantly non-pathogenic Gram-positive microorganisms. While the identified organisms pose minimal risk to immunocompetent individuals, routine surface disinfection, enhanced maintenance protocols and evidence-based dispenser design modifications are recommended to ensure hygiene infrastructure integrity in educational settings.

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