Legionella pneumophila Grows Adherent to Surfaces in vitro and in situ

Abstract

Legionella pneumophila continues to play a role in both community- and nosocomially-acquired pneumonia. We investigated the ability of L pneumophila to adhere to various types of materials such as those found in the hospital air-cooling and portable water distribution systems. Through the use of a unique sampling apparatus, we were able to regularly acquire planktonic and sessile samples and determine the numbers of bacteria present in both populations, in vitro and in situ. Portions of these apparatuses could be aseptically removed for examination by scanning electron microscopy, or for the determination of the number of viable adherent L pneumophila. The number of bacteria present in each sample was determined by direct plate count, with presumptive L pneumophila colonies being positively identified by direct fluorescent antibody staining techniques. The results demonstrated that not only are legionellae capable of colonizing various metallic and nonmetallic surfaces but that they are preferentially found on surfaces. Surface-adherent bacteria may play a profound role as a reservoir of these potential pathogens in aquatic environments. Furthermore, these results suggest that any comprehensive legionella monitoring program must include not only water samples but also an examination of the adherent populations.

Legionella pneumophila contamination of a dental unit water line system in a dental teaching centre

“…The significant effect of the clinic can also be ascribed to a number of collective factors that may influence the bacterial levels in dental units: the type of materials used in the tubing, the bore size of the tubing and the frequency of use (38–41). Indeed, due to the fact that mainly the removable prosthodontics are performed in the prosthodontics clinic, the hand pieces will not be used frequently; therefore, the L. pneumophila was found to be present in much lower counts in the prosthodontics clinic than in the conservative dentistry and periodontology clinics, as a result of less utilization rate, no water heating and consequently, less favourable conditions for bacterial amplification.…”

Long-term survival of Legionella pneumophila serogroup 1 under low-nutrient conditions and associated morphological changes

“…The association of L. pneumophila with water and water systems is now well established [3,14,[20][21][22]. Because legionellae are ubiquitous in the natural environment, it is often difficult to 'track', the source of this organism.…”

“…L. pneumophila cells, in general, are pleomorphic, with three morphological types (small rods, large bacilli, and filamentous rods) reported [6,11,22,25]. Anecdotal reports in the literature describe the emergence of filamentous forms of Legionella upon subculture of a clinical isolate on artificial media [11,12,26]; this is possibly due to recovery on antibiotic media.…”

“…Association with cyanobacteria, protozoa, and location within, as well as formation of, biofilms most certainly must be included in strategies employed by Legionella spp. for long-term survival in aquatic environments [1,5,14,22]. Whatever the strategy and regardless of culturability, environmental strains of Legionella can survive for periods greater than 2.4 years under low nutrient conditions and still be detected by direct fluorescent-antibody staining.…”

Legionella in water distribution systems

“…Legionella and other microorganisms attach to surfaces and form biofilms on pipes and other materials throughout the water distribution system. Legionella can colonize plastics such as polyvinyl chloride, stainless steel, rubber, wood, and to a lesser degree copper in concentrations up to 10 5 cfu/cm 2 6 , 17 . Water‐pressure changes that disturb the biofilm may dramatically increase the concentration of Legionella.…”