Isolation of Raoultella planticola from refillable antimicrobial liquid soap dispensers in a dental setting

Abstract

Background: Liquid antimicrobial soaps are commonly used in the dental health care setting for hand washing to minimize the potential spread of infectious agents to health care workers and patients. The purpose of the current study was to evaluate possible bacterial contamination of antimicrobial liquid soap dispensers located in 2 institutional comprehensive dental care clinics.

Methods: Fourteen soap dispensers and 16 original stock containers were sampled. A 1-milliliter aliquot was diluted in 10 mL of phosphate buffer (Tween-80; Acros). Serial dilutions were plated in duplicate on neutralizing agar and incubated for 7 days. Molecular identification was performed using 500 base pair comparisons of 16S ribosomal ribonucleic acid sequencing. Taq polymerase chain reaction was performed with sequence-specific primers for Raoultella species.

Results: Bacterial growth was observed at 18 hours for 57% (8 of 14) of soap dispenser samples. Bacterial densities ranged from 4 × 10(2) to 6 × 10(9) colony-forming units per milliliter. Original commercial containers exhibited no growth. Isolates were identified as Raoultella (Klebsiella) planticola.

Conclusions: This is the first study to the authors' knowledge indicating recovery of R. planticola from antimicrobial liquid soap dispensers. R. planticola is a recognized environmental opportunistic pathogen that potentially poses a health concern.

Practical implications: These findings indicate compliance problems with infection prevention recommendations and support the US Centers for Disease Control and Prevention's recommendation that dispensers should not be topped off. High bacterial loads of R. planticola are inconsistent with infection control practices and are a concern because transmission and possible infection to the health care worker or the patient may occur.

Keywords: Bacterial contamination; Raoultella (Klebsiella) planticola; hand washing; liquid soap.

Figure 1

Representative alignment of the 16S rDNA 500 base pair sequencing of 8 Raoultella planticola isolates from liquid soap dispensers.

Figure 2

Taq PCR amplicons for 6 bacterial isolates using Raoultella planticola sequence specific primers (amplicon size 1121 bp) on 1% agarose gel. Lanes are labeled with collection locations. NTC lanes = no template controls. Abbreviation Key.