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. 2022 Sep:127:26-33.
doi: 10.1016/j.jhin.2022.05.017. Epub 2022 Jun 8.

Prevalence of alcohol-tolerant and antibiotic-resistant bacterial pathogens on public hand sanitizer dispensers

Y W S Yeung  1 , Y Ma  1 , S Y Liu  1 , W H Pun  2 , S L Chua  3
Affiliations

Prevalence of alcohol-tolerant and antibiotic-resistant bacterial pathogens on public hand sanitizer dispensers

Y W S Yeung et al. J Hosp Infect. 2022 Sep.

Abstract

Background: Since the advent of the COVID-19 pandemic, alcohol-based hand sanitizer dispensers (HSDs) have been installed in most public and clinical settings for hygiene purposes and convenient application.

Aim: To determine whether sanitizer-tolerant bacterial pathogens can colonize HSDs, spreading diseases and antibiotic resistance.

Methods: Sampling was conducted from operational automatic HSDs, specifically the dispensing nozzle in direct contact with sanitizer. Culture-dependent cultivation of bacteria and MALDI-TOF were employed to assess microbiological contamination. Bacterial isolates were selected for rapid killing and biofilm eradication assays with alcohol treatment. Antibiotic minimum inhibitory concentration assays were performed according to the Clinical and Laboratory Standards Institute guidelines. Virulence potential of bacterial isolates was evaluated in the Caenorhadbitis elegans infection model.

Findings: Nearly 50% of HSDs from 52 locations, including clinical settings, food industry, and public spaces, contain microbial contamination at 103-106 bacteria/mL. Bacterial identification revealed Bacillus cereus as the most frequent pathogen (29%), while Enterobacter cloacae was the only Gram-negative bacterial pathogen (2%). Selecting B. cereus and E. cloacae isolates for further evaluation, these isolates and associated biofilms were found to be tolerant to alcohol with survival up to 70%. They possessed resistance to various antibiotic classes, with higher virulence than laboratory strains in the C. elegans infection model.

Conclusion: HSDs serve as potential breeding grounds for dissemination of pathogens and antibiotic resistance across unaware users. Proper HSD maintenance will ensure protection of public health and sustainable use of sanitizing alcohols, to prevent emergence of alcohol-resistant pathogens.

Keywords: Alcohol tolerance; Antibiotic resistance; Bacteria; Hand sanitizer; Infection.

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Figures

Figure 1
Figure 1
Characteristics of the microbes found on dispensing nozzle of hand sanitizer dispensers. (A) Study profile of samples collected from different locations for microbiological analysis. (B) Bacterial cfu from each dispenser contaminated with bacteria (presented in ascending order). Means and SD from triplicate experiments are shown.
Figure 2
Figure 2
Microbes are tolerant to killing by low levels of alcohol after 10 min of treatment. Means and SD from triplicate experiments are shown. BC, Bacillus cereus; EC, Enterobacter cloacae. ∗∗∗P < 0.001; n.s., not significant; n.d., not detectable.
Figure 3
Figure 3
Microbial biofilms are tolerant to low levels of alcohol. Means and SD from triplicate experiments are shown. BC, Bacillus cereus; EC, Enterobacter cloacae. ∗∗∗P < 0.001; n.s., not significant; n.d., not detectable.
Figure 4
Figure 4
Bacillus cereus (BC) (A) and Enterobacter cloacae (EC) (B) are virulent against Caenorhabditis elegans infection assay.
See this image and copyright information in PMC

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