Innovative Antibiofilm Smart Surface against Legionella for Water Systems

Abstract

Legionella pneumophila contamination of water systems is a crucial issue for public health. The pathogen is able to persist in water as free-living planktonic bacteria or to grow within biofilms that adhere to and clog filters and pipes in a water system, reducing its lifespan and, in the case of hospital buildings, increasing the risk of nosocomial infections. The implementation of water management is considered to be the main prevention measure and can be achieved from the optimization of water system architecture, notably introducing new materials and strategies to contrast Legionella biofilm proliferation and so prolong the water system functionality. In this research, we propose a new smart surface against L. pneumophila biofilm formation. This is based on an innovative type of coating consisting of a sulfonated pentablock copolymer (s-PBC, commercially named Nexar™) deposited on top of a polypropylene (PP) coupon in a sandwich filter model. The covering of PP with s-PBC results in a more hydrophilic, acid, and negatively charged surface that induces microbial physiological inhibition thereby preventing adhesion and/or proliferation attempts of L. pneumophila prior to the biofilm formation. The antibiofilm property has been investigated by a Zone of Inhibition test and an in vitro biofilm formation analysis. Filtration tests have been performed as representative of possible applications for s-PBC coating. Results are reported and discussed.

Keywords: Legionella pneumophila; biofilm; s-PBC; smart coatings; water safety plan.

Figure 1

Chamber slide for biofilm analysis. (a) Structural components of cultural system. (b) Sample loaded: (1) L. pneumophila culture; (2) L. pneumophila with Floating PP coupon; (3–4) Replicas of L. pneumophila culture with floating s-PBC coupon.

Figure 2

Nalgene^TM reusable unit for 250 mL water filtration. Details of vacuum nozzle (*) and filter holder (**).

Figure 3

Zone of Inhibition Test on Legionella pneumophila SG 2–16: a s-PBC@PP coupon surrounded by an inhibition zone (green dashed line); b PP coupon.

Figure 4

Biofilm of Legionella pneumophila SG 2–16 at 10×, 40× and 100× of microscope magnification formed without coupon (a–c), on floating PP coupons (d–f) and on floating s-PBC@PP coupons (g–i), respectively. Detail of cell bodies at 100× magnification (*).

Figure 5

Colony density of L. pneumophila in starting (aI,bI) and filtered water samples: 50 mL sample after 1 (aII) and 5 (aIII) filtrations with PP filter; 50 mL sample after 1 (bII) and 5 (bIII) filtrations with s-PBC@PP filter; 200 mL sample after 6 filtrations with PP (cI) and s-PBC@PP (cII) filter. Colony density of total L. pneumophila blocked on PP (dI) and s-PBC@PP (dII) filter surface.

Figure 5

Colony density of L. pneumophila in starting (aI,bI) and filtered water samples: 50 mL sample after 1 (aII) and 5 (aIII) filtrations with PP filter; 50 mL sample after 1 (bII) and 5 (bIII) filtrations with s-PBC@PP filter; 200 mL sample after 6 filtrations with PP (cI) and s-PBC@PP (cII) filter. Colony density of total L. pneumophila blocked on PP (dI) and s-PBC@PP (dII) filter surface.