The need for in-house efficacy testing and assessment of the antimicrobial properties of silver nanoparticle (Ag+) impregnated showerheads, against Pseudomonas aeruginosa, intended for healthcare waters in high-risk patient settings.

Pseudomonas aeruginosa is a Gram-negative water-borne opportunistic pathogen. Reservoirs of bacteria can infect vulnerable populations. Mitigation of this risk in healthcare includes regular microbiology monitoring and chemical/thermal disinfection of outlets. Where contamination is persistent, point-of-use filters/antimicrobial showers may be used to reduce bioburden. In this study, the efficacy of a silver-impregnated (Ag+) antimicrobial showerhead against P. aeruginosa was tested, under simulated conditions. Test (excised from antimicrobial [Ag+] showerhead) and control (stainless-steel) coupons (∼1cm2; n=108) were inoculated with 10µL (∼103 colony forming units [CFU]) P. aeruginosa (NCTC 10662 and wild-types) and overlaid with coverslips. Coupons were incubated at ambient temperature (∼40% relative humidity) for 0 minutes, 30 minutes, 2 hours, 4 hours, 24 hours. Coupons and coverslips were transferred to neutraliser solution followed by bead washing for bacterial recovery and enumeration. Contamination ranged from ∼2.90-log10 CFU (±0.14-log10; type-strain) to ∼3.02-log10 CFU (±0.16-log10; wild-types). No significant reductions in P. aeruginosa bioburden were observed against either of the three strains (P>0.05). Analogous bacterial decline was noted between the test and control (falling to below the detection limit) between 4-24 hours, possibly due to desiccation. Whilst being an economically and environmentally friendly option, antimicrobial showers may not be appropriate to lessen bioburden in healthcare waters. Previous research has demonstrated the bactericidal effects of silver-ions, however this was not established in our study. Although the concentration of silver in the test materials was unknown, our findings suggest that antimicrobial showerheads may require higher concentrations of silver-ions, to display antimicrobial activity. Further testing is required to determine efficacy against biofilms.

Enhanced monitoring of healthcare shower water in augmented and non-augmented care wards showing persistence of Pseudomonas aeruginosa despite remediation work.

Introduction. Pseudomonas aeruginosa in healthcare shower waters presents a high risk of infection to immune-suppressed patients; identifying the colonization-status of water outlets is essential in preventing acquisition.Hypothesis/Gap Statement. Testing frequencies may be insufficient to capture presence/absence of contamination in healthcare waters between sampling and remediation activities. Standardization of outlets may facilitate the management and control of P. aeruginosa.Aim. This study aims to monitor shower waters and drains for P. aeruginosa in augmented and non-augmented healthcare settings every 2 weeks for a period of 7 months during remedial actions.Methodology. All shower facilities were standardized to include antimicrobial silver-impregnated showerhead/hose units, hose-length fixed to 0.8 m and replaced every 3 months. Standard hospital manual decontamination/disinfection occurred daily. Thermostatic-mixer-valves (TMVs) were replaced and disinfected if standard remediation unsuccessful.Results. Of 560 shower and drain samples collected over 14 time-points covering 7 months, P. aeruginosa colonized 40 %(4/10; non-augmented) and 80 %(8/10; augmented-care) showers in the first week. For each week elapsed, new outlets became contaminated with P. aeruginosa by 18-19 % (P<0.001) in shower waters (OR=1.19; CI=1.09-1.31) and drains (OR=1.18; CI=1.09-1.30). P. aeruginosa occurrence in shower water was associated with subsequent colonization of the corresponding drain and vice versa (chi-square; P<0.001) with simultaneous contamination present in 31 %(87/280) of areas. TMV replacement was ineffective in eradicating colonisation in ~83 % of a subset (6/20; three per ward) of contaminated showers.Conclusions. We demonstrate the difficulties in eradicating P. aeruginosa from hospital plumbing, particularly when contamination is no longer sporadic. Non-augmented care settings are reservoirs of P. aeruginosa and should not be overlooked in outbreak investigations. Antimicrobial-impregnated materials may be ineffective once colonization with P. aeruginosa is established beyond the hose and head. Reducing hose-length insufficient to prevent cross-contamination from shower drains. P. aeruginosa colonization can be transient in both drain and shower hose/head. Frequent microbiological monitoring suggests testing frequencies following HTM04-01 guidelines are insufficient to capture the colonization-status of healthcare waters between samples. Disinfection/decontamination is recommended to minimize bioburden and the effect of remediation should be verified with microbiological monitoring. Where standard remediation did not remove P. aeruginosa contamination, intensive monitoring supported justifying replacement of showers and contiguous plumbing.