Risk Assessment for the Spread of Serratia marcescens Within Dental-Unit Waterline Systems Using Vermamoeba vermiformis

Abstract

(2015) Risk assessment for the spread of Serratia marcescens within dental unit waterline systems using Vermamoeba vermiformis. Current Microbiology, 71 (4). pp. 434 442.It is advisable to refer to the publisher's version if you intend to cite from the work.http://dx.doi.org/10.1007/s00284-015-0872-0For more information about UCLan's research in this area go to http://www.uclan.ac.uk/researchgroups/ and search for <name of research Group>. Conflict of interest disclosure statementAll named authors declare that there is no conflict of interest.2 Title: Risk assessment for the spread of Serratia marcescens within dental-unit waterline systems using Vermamoeba vermiformis Abstract:Vermamoeba vermiformis is associated with the biofilm ecology of dental-unit waterlines (DUWLs). This study investigated whether V. vermiformis is able to act as a vector for potentially pathogenic bacteria and so aid their dispersal within DUWL systems. Clinical dental water was initially examined for Legionella species by inoculating it onto Legionella selective-medium plates. The molecular identity/profile of the glassy colonies obtained indicated none of these isolates were Legionella species. During this work bacterial colonies were identified as a non-pigmented Serratia marcescens. As the water was from a clinical DUWL which had been treated with Alpron™ this prompted the question as to whether S. marcescens had developed resistance to the biocide. Exposure to Alpron™ indicated that this dental biocide was effective, under laboratory conditions, against S. marcescens at up to 1x10 8 colony forming units/millilitre (cfu/ml). V. vermiformis was cultured for eight weeks on cells of S. marcescens and Escherichia coli. Subsequent electron microscopy showed that V.vermiformis grew equally well on S. marcescens and E. coli (p = 0.0001). Failure to detect the presence of S.marcescens within the encysted amoebae suggests that V. vermiformis is unlikely to act as a vector supporting the growth of this newly isolated, nosocomial bacterium.

Developing an ecologically relevant heterogeneous biofilm model for dental-unit waterlines

“…The large size of the L. pneumophila seen under the electron microscope also supports this conclusion, as it was out-with the size-range of bacteria, this amoeba choose to feed upon (Dillon et al 2014 b ;Lal et al 2015).…”

“…In this study, the rationale for sub-culturing all colonies that were initially observed on GVPC plates was to determine whether they were Legionella, as a variety of non-Legionella species with glassy appearance, a typical example S. marcescens, can also grow on this medium (Lal et al 2015). By culturing bacteria on R2A, the isolated bacteria may demonstrate their pigmentation and swarming characteristics.…”

“…For isolating protozoa, freshly prepared Escherichia coli (XL blue) were used to serve as a "food line" (Lal et al 2015). The unused half of the cut side of the tubing was placed directly in contact with one end of the food line to "encourage" amoebae to graze on E. coli supplied as food on the R2A plate then incubated at 22°C for 7 days.…”

“…In vitro simulated waterline systems have been used to test proprietary biocides for dental use (Spratt et al 2004;Dillon et al 2014 b ;Lal et al 2015;Ditommaso et al 2016). These in vitro models were designed primarily for testing biocide efficacy on specific biofilm bacterial species (Spratt et al 2004) and on Vermamoeba vermiformis ).…”

“…These in vitro models were designed primarily for testing biocide efficacy on specific biofilm bacterial species (Spratt et al 2004) and on Vermamoeba vermiformis ). The latter model was used for subsequent studies on the cultivation of amoebae for in vitro propagation of an avirulent form of Legionella (Dillon et al 2014 b ), and Serratia marcescens (Lal et al 2015). More recently, Ditommaso et al (2016) tested the efficacy of a biocide on L. pneumophila serogroup 1 in a new clinical dental waterline without an ecologically relevant biofilm.…”