Field trial of biocides for control of Legionella in cooling towers

Bentham, Richard; Broadbent, Clive

doi:10.1007/bf00296203

Cited by 13 publications

(6 citation statements)

References 12 publications

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“…The high level of L. pneumophila obtained when the plant was restarted in October may be due to fouling of the network and considerable biofilm development during the shutdown period. This result fits in with the fact that cooling towers are implicated in outbreaks of legionellosis, particularly at startup or during construction (7,10). It has been suggested that there may be a relationship between high Legionella counts in cooling towers and the occurrence of outbreaks of legionellosis (31).…”

Section: Discussionsupporting

confidence: 74%

“…Most cases of legionellosis can be traced to human-made aquatic environments where the water temperature is higher than the ambient temperature (17). In particular, cooling towers have been implicated in major outbreaks of legionellosis caused by Legionella pneumophila (7,10,19,22). Legionella species are facultative intracellular gram-negative bacilli which multiply in protozoan hosts and can also survive within microbial biofilm communities (17).…”

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confidence: 99%

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Dynamics of Legionella spp. and Bacterial Populations during the Proliferation of L. pneumophila in a Cooling Tower Facility

Wéry

Bru-Adan

Minervini

et al. 2008

Appl Environ Microbiol

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The dynamics of Legionella spp. and of dominant bacteria were investigated in water from a cooling tower plant over a 9-month period which included several weeks when Legionella pneumophila proliferated. The structural diversity of both the bacteria and the Legionella spp. was monitored by a fingerprint technique, single-strand conformation polymorphism, and Legionella spp. and L. pneumophila were quantified by real-time quantitative PCR. The structure of the bacterial community did not change over time, but it was perturbed periodically by chemical treatment or biofilm detachment. In contrast, the structure of the Legionella sp. population changed in different periods, its dynamics at times showing stability but also a rapid major shift during the proliferation of L. pneumophila in July. The dynamics of the Legionella spp. and of dominant bacteria were not correlated. In particular, no change in the bacterial community structure was observed during the proliferation of L. pneumophila. Legionella spp. present in the cooling tower system were identified by cloning and sequencing of 16S rRNA genes. A high diversity of Legionella spp. was observed before proliferation, including L. lytica, L. fallonii, and other Legionella-like amoebal pathogen types, along with as-yet-undescribed species. During the proliferation of L. pneumophila, Legionella sp. diversity decreased significantly, L. fallonii and L. pneumophila being the main species recovered.

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Section: Discussionsupporting

confidence: 74%

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confidence: 99%

Dynamics of Legionella spp. and Bacterial Populations during the Proliferation of L. pneumophila in a Cooling Tower Facility

Wéry

Bru-Adan

Minervini

et al. 2008

Appl Environ Microbiol

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“…On the other hand, the others [21,23] indicated that BNPD was ineffective against legionellae. In our study, the efficacy of BNPD showed variability according to strains and contact times.…”

Section: Resultsmentioning

confidence: 99%

Efficacy of Colloidal Silver-Hydrogen Peroxide and 2-Bromo-2-nitroporopane-1,3-diol Compounds Against Different Serogroups of Legionella pneumophila Strains

et al. 2011

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Cooling towers are considered as amplifier and disseminator sources for Legionella spp. despite preventive treatments. Information which was obtained from biocidal tests could improve the effectiveness of treatments. Therefore, the choice of appropriate biocides and the applying of biocides in correct dosages and contact times are important. Various oxidizing and non-oxidizing biocides have been investigated in vitro for their effectiveness against legionellae. Colloidal silver-hydrogen peroxide (CSHP) and 2-bromo-2-nitroporopane-1,3-diol (BNPD) biocides were selected as an example for oxidizing and non-oxidizing agents, respectively, in view of bactericidal action against different serogroups of L. pneumophila strains [serogroup 1 (S1) and serogroup 2-14 (S2)] which are isolated different cooling towers in the vicinity of Istanbul, Turkey and reference strain. In the current study, oxidizing biocide was found more effective than non-oxidizing biocide in terms of contact times, log reductions and recommended dosages. At the recommended concentrations for cooling towers (100 ppm), while CSHP compound killed all strains in 3 h contact time, BNPD compound killed S2 and reference strain in the same contact time, S1 strain after 6 h contact time. The results of the present study showed that effective biocide applications can be achieved by pre-determining minimum inhibitory concentration (MIC) and minimum contact time of different biocides to kill target bacteria.

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“…A similar outbreak also occurred in 2013, with repeat mass shock-dosing undertaken in April 2013. Shock dosing is expected to render Legionella species undetectable for between one to thirty days with considerable variability, depending on the characteristics of the tower (one study reported a mean of 14 days, with standard deviation 13 days, based on a sample of experiments undertaken on 9 contaminated towers with chlorinated phenolic thioether [8]). …”

Section: Introductionmentioning

confidence: 99%

Mass Shock-dosing of Cooling Towers in Response to A Legionella pneumophila Outbreak: Did it Work?

Baker¹,

O’Brien²,

Reynolds³

2015

J Biom Biostat

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Between January and June 2012, a moderate-sized Legionella pneumophila serogroup 1 (Lp1) outbreak occurred in Auckland, New Zealand, which involved 19 cases, with two deaths. Initial investigation did not reveal a common source. Poorly maintained cooling towers were a likely cause, and mass shock dosing of all such towers with biocide was undertaken in April 2012 and repeated after an almost identical outbreak in the autumn of 2013. Our aim was to assess whether shock dosing of towers affected disease incidence. A time-series analysis, using regression discontinuity, of the notified Lp1 cases from 2007 to October 2014 was carried out.A total of 84 out of 92 cases of Lp1 were available for analysis. Seasonal trend decomposition showed an excess of cases in the autumn of 2012 and 2013, with a decline in 2014. Poisson regression showed an average log-linear annual increase in monthly notifications by 40% (95% confidence interval (CI): 17% to 68%), with an average 46% decline (95% CI: 74% decrease to 13% increase) comparing cases before April 2012 to those that occurred afterward. In dispersed outbreaks in urban settings, we conclude that this study supports mass shock dosing of cooling towers to limit disease occurrence.

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Field trial of biocides for control of Legionella in cooling towers

Cited by 13 publications

References 12 publications

Dynamics of Legionella spp. and Bacterial Populations during the Proliferation of L. pneumophila in a Cooling Tower Facility

Dynamics of Legionella spp. and Bacterial Populations during the Proliferation of L. pneumophila in a Cooling Tower Facility

Efficacy of Colloidal Silver-Hydrogen Peroxide and 2-Bromo-2-nitroporopane-1,3-diol Compounds Against Different Serogroups of Legionella pneumophila Strains

Mass Shock-dosing of Cooling Towers in Response to A Legionella pneumophila Outbreak: Did it Work?

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