Negligible influence of limescale deposits on faucet aerators on measured microorganism loads

Abstract

Introduction: The study was conducted to assess the effects of limescale deposits on faucet aerators on the qualitative and quantitative detection of microorganisms from swabbing and first jet water samples.

Methods: Limescale deposits on faucet aerators were categorized into three groups: not / slightly calcified, moderately calcified and heavily calcified. Colonization was assessed by isolating microorganisms from standardized swabbing and water samples. Microorganisms isolated from the aerators were compared with clinical isolates from the same year.

Results: Regardless of the degree of calcification on the faucet aerators, similar numbers and types of microorganisms were found. Except for Staphylococcus epidermidis and the rare occurrence of Staphylococcus aureus and Nacaseomyces glabratus on the aerators, there were no matches between the microorganisms isolated from the aerators and the top ten clinical isolates. Microorganisms frequently isolated from aerators, such as Sphingomonas paucimobilis, were extremely rare in clinical samples. No differences in species were observed based on the degree of calcification of the aerators.

Conclusions: The study did not demonstrate a significant effect of the degree of calcification on the colonization of aerators. Although calcification of aerators as a risk factor for increased microbial transmission cannot be entirely dismissed, its importance appears to be secondary.

Keywords: calcification; hygiene; risk; transmission; water quality; waterborne.

Fig. 1.

a–d. Categories of lime deposits on faucet aerators and swab-based sampling technique. a) not / slightly calcified (no calcification or only small deposits), b) moderately calcified (defined by a yet interrupted ring of limescale) and c) heavily calcified (aerator covered by a continuous ring of limescale). d) Aerators were sampled comprising one swipe along the outside metal ring, followed by two more swipes across the underside surface in a perpendicular manner

Fig. 2.

Microbial loads on faucet aerators. The mean values and standard deviations of the microbial loads on aerators across all three degrees of calcification, determined by swabbing, are visualized for the individual microorganism groups in a logarithmic scale. Very small values for bacterial counts or standard deviations are not graphically represented due to the chosen logarithmic scale. CFU = colony forming unit

Fig. 3.

Microbial loads on faucet aerators. The mean values and standard deviations of the microbial loads on aerators across all three degrees of calcification, determined by water sampling, are visualized for the individual microorganism groups in a logarithmic scale. Very small values for bacterial counts or standard deviations are not graphically represented due to the chosen logarithmic scale. CFU = colony forming unit