Isolation of a Raoultella (Klebsiella) species from refillable soap dispensers

Antimicrobial soaps are commonly used in the dental healthcare setting for hand washing to minimize the potential spread of infectious agents among dental healthcare workers (DHCWs). Objectives: This study determined if refillable soap dispensers in a clinical dental setting harbor bacteria that may pose an infection control risk to DHCWs. Methods: Five ml of liquid soap was collected from 14 soap dispensers throughout a dental clinic and from their commercial containers. One ml aliquots were diluted in 10 ml of phosphate buffer, pH 7.2 (Ricca Chemical Co, Arlington, TX) with 2% polysorbate-80 (Tween-80). Samples were vortexed for 1 minute until homogenous. Serial dilutions to 10⁶ were plated in duplicate by spread-plate method on D/E Neutralizing Agar (Becton Dickinson, Sparks, MD). Plates were incubated at 35^oC for 7 days. Plates with bacterial colonies were enumerated and then re-isolated on D/E Neutralizing agar for molecular identification using 500 bp comparisons of 16S rDNA sequencing (Accugenix, Newark, DE). Positive samples were also plated on selective media, MacConkey-Inositol-Carbenicillin (MCIC) agar, for Klebsiella spp. for additional 16S rDNA identification. Results: Bacterial growth was observed at 18 hours on D/E agar plates with 8 of the 14 samples collected from refillable soap dispensers. Bacterial densities from positive soap samples ranged from 4 X 10² to 6 X 10¹⁰ colony forming units/ml. No growth was observed from stock soaps taken from their commercial containers. Colony isolates from both D/E and MCIC agar plates were Gram negative rods and identified as Raoultella (Klebsiella) planticola/ornithinolytica using 16S rDNA sequencing. Conclusions: Raoultella (Klebsiella) planticola/ornithinolytica was isolated from dental clinic soap dispensers and is recognized as an environmental opportunistic pathogen. Supported by UAB School of Dentistry.