There is an increasing body of work in the literature which documents the relationship between Legionella and protozoa. Recent research points to the possibility that the protozoa can serve as hosts to Legionella, thereby providing an environment in which Legionella can multiply while being protected from biocides. While several studies examined the efficiency of commonly used biocides against protozoa the efficacy of glutaraldehyde had not been determined. This paper will detail the efficiency of glutaraldehyde and a glutaraldehyde/quatemary amine blend along with several different commonly used water treatment biocides against both pure protozoan strains and field isolates.
Perhaps no other microorganism provokes as much concern in the water treatment industry as Legionella bacteria. ?II-h causative agent? for Legioinellosis is ubiquitous: but is known to be easily killed by most commonly used water treatment biocides.3-? Still, the occurrence of LegioneUa outbreaks is cause for concern. When such outbreaks occur, the recommended guidelines for remediation involve the use of very high levels of oxidizing biocides.8 Biocidal treatment regimens are not always effective as it is known that rigorous treatments do not always provide long term protection tkom reoccurring outbreaks.9 This apparent paradox would suggest the involvement of some external factor or factors which helps the Legionella survive in those systems.
There now exists in the scientific literature a fascinating body of evidence which documents the relationship between Legionella and amoebae. Amoebae and protozoa are single cell microorganisms which are also known to be ubiquitous in nature. The link between Legione12a and amoebae was first demonstrated by Rowbotham who showed that amoebae could serve as hosts for the Legione21a.?0 Soon after, Kurd? described the isolation of amoebae in cooling waters which contain Legionella, thereby lending further support to Rowbotham?s theory on the relationship between the two. A later report by Rowbotham?2then offered a mechanism for the growth and proliferation of Legionlla within the amoebae, Acanthamoeba polyphaga.
Amoebae and Legionella were found in cooling water systems known to contain blofrlms.]3 The presence of biofilms could provide aprotective environment for these organisms, and may help explain why the recommended guidelines for Legionella remediation does not always eliminate the infection problem. Rowbotham?2 hypothesized that the actual infective agent for Legionellosis in humans was the Legionella infected amoebae. If this theory is true, then it would suggest that amoebae should rdso be targeted for control by water treatment biocides. Indeed, Fields?4 suggested in 1989 that it may be more practical to eliminate the amoebae-Legiorrella interactions rather than try to eliminate the bacteria alone. Eliminating amoebae and protozoa may have additional health benefits as some species of amoebae are known to be class III pathogens.
While the efficacy of most commonly used biocides against Legionella has been studied, very little has appeared in the literature on the effectiveness of biocides against amoebae and protozoa. A recent report by Sutherland and Berk?s determined the efficacy of four different nonoxidizing biocides against several different protozoa while there are several other reports on the eficacy of other oxidizing and nonoxidizing biocides against amoebae.?16?17 Glutaraldehyde was not used in any of the earlier studies and as such its effectiveness against the amoebae has not been determined. This paper will detail the efficacy of glutaraldehyde, and a glutaradehyde/quaternary amine blend, against both pure stra
