Copper Silver Ionisation Effect On stenotrophomonas Maltophilia
The updated version of HTM04-01 states that duty holders at healthcare estates must ensure the safety of all water used by patients, residents, staff and visitors to minimise the risk of infection associated with all waterborne pathogens, including Stenotrophomonas maltophilia. Copper silver ionisation has been proven to effectively control pathogens, such as as Stenotrophomonas maltophilia, in water systems.
About Stenotrophomonas Maltophilia
The HTM04-01 states that S. maltophilia “is an emerging opportunistic environmental pathogen that causes healthcare-associated infections and is found in aqueous habitats including water sources." This, in combination with the increasing incidence of community-acquired infections, is of particular concern for immune-compromised individuals due to the pathogen's significant fatality/case ratio (Brooke 2012).
Stenotrophomonas Maltophilia, previously known as Pseudomonas maltophilia and Xanthomonas maltophilia, is associated with wet surfaces and aqueous solutions. It is an organism with various molecular mechanisms for colonisation and infection and its habits within the healthcare environment are similar to P. aeruginosa. We associate it with the colonisation of:
- Taps/tap water
- Sinks/sink traps
- Hydrotherapy pools
- Ice-makers, disinfectant solutions
- Nebuliser chambers
- Humidifier reservoirs
- Ventilator circuits
S. maltophilia has become an important pathogen as it can acquire genes from other bacteria species, including those involved in antibiotic resistance (Brooke 2012). Adding to this, it can transfer antibiotic resistance to other bacteria and survive with minimal nutrients (Babalova et al. 1995).
S. maltophilia cut-off from tap water was responsible for the colonisation/infection of five neonates in a neonatal intensive-care unit. Where clinical results indicate water may be a vector in the transmission of Stenotrophomonas spp., then you should carry out water sampling as per P. Aeruginosa.” (See page 20 of HTM04-01).
S. Maltophilia Control In Water Systems
Tolerance is a problem when trying to control microorganisms. S. maltophilia is of particular concern because of its resistance to some biocides. Brooke (2012) presented a comprehensive review of studies on S. maltophilia which includes its biocide tolerance. The study showed that:
- S. macrophilia was recovered in large numbers (5.1 x 105 – 4.8 x 106) in sputum suction tubing after exposure to 0.1% sodium hypochlorite for 2h.
- Resistance to Triclosan (2,4,4’-trichloro-2’-hydroxydiphenylether) and sodium dodecyl sulphate (SDS) was also demonstrated, with clinical isolate X26332 surviving and persisting in a 0.02% solution of SDS for 14 days at 30⁰C.
- Silver nitrate, at the recommended dose of 100 µg/L, did not prevent biofilms formation in drinking water. Only when concentration of silver nitrate reached around 10,000 µg/L was it able to inhibit biofilm formation.
Brooke’s study also discussed metal resistance in clinical and environmental settings. It showed that S. maltophilia cells have gene clusters used for the import, storage and efflux of metals.
Copper Silver Ionisation Effect On Stenotrophomonas Maltophilia
HTM04-01 states that S. maltophilia is heat-sensitive and will not grow above 40°C. Therefore, good temperature management should reduce the risk of colonisation. However, control is not certain.
Copper and silver ionisation is effective against Stenotrophomonas Maltophilia, as well as Legionella and P. aeruginosa (Liu et al. 1994, Miuetzner et al. 1997, Liu et al. 1998, Stout et al. 1998, Biurrun et al. 1999, Rohr et al. 1999, Kusnetsov et al. 2001, Stout and Yu 2003, Chen et al. 2008, Lin et al. 2011, Bedford 2012, Barbosa & Thompson 2016). I
In addition, there is evidence that copper silver ionisation inactivates biofilm and free living based forms of Stenotrophomonas Maltophilia. Because the copper and silver are in their ionic state they are able to kill microbial cells and therefore control Stenotrophomonas Maltophilia in water systems.