Legionella on board trains: effectiveness of environmental surveillance and decontamination

Abstract

BackgroundLegionella pneumophila is increasingly recognised as a significant cause of sporadic and epidemic community-acquired and nosocomial pneumonia. Many studies describe the frequency and severity of Legionella spp. contamination in spa pools, natural pools, hotels and ships, but there is no study analysing the environmental monitoring of Legionella on board trains. The aims of the present study were to conduct periodic and precise environmental surveillance of Legionella spp. in water systems and water tanks that supply the toilet systems on trains, to assess the degree of contamination of such structures and to determine the effectiveness of decontamination.MethodsA comparative pre-post ecological study was conducted from September 2006 to January 2011. A total of 1,245 water samples were collected from plumbing and toilet water tanks on passenger trains. The prevalence proportion of all positive samples was calculated. The unpaired t-test was performed to evaluate statistically significant differences between the mean load values before and after the decontamination procedures; statistical significance was set at p ≤ 0.05.ResultsIn the pre-decontamination period, 58% of the water samples were positive for Legionella. Only Legionella pneumophila was identified: 55.84% were serogroup 1, 19.03% were serogroups 2–14 and 25.13% contained both serogroups. The mean bacterial load value was 2.14 × 103 CFU/L. During the post-decontamination period, 42.75% of water samples were positive for Legionella spp.; 98.76% were positive for Legionella pneumophila: 74.06% contained serogroup 1, 16.32% contained serogroups 2–14 and 9.62% contained both. The mean bacterial load in the post-decontamination period was 1.72 × 103 CFU/L. According to the t-test, there was a statistically significant decrease in total bacterial load until approximately one and a half year after beginning the decontamination programme (p = 0.0097).ConclusionsThis study indicates that systematic environmental surveillance could be a useful approach for assessing the risk of exposure to Legionella bacteria, which still represents a public health threat. According to the study results, an environmental surveillance programme, followed by decontamination procedures where necessary, would decrease the total bacterial count, protecting the health of travellers and workers.

Legionella control in the water system of antiquated hospital buildings by shock and continuous hyperchlorination: 5 years experience

“…may persist in hospital environment for several years, even at undetectable levels as Legionella Viable but non Culturable (VBNC), causing sporadic infections or epidemics [ 26 , 27 ]. Even if hyperchlorination of the water is consistently performed, this approach is particularly appropriate for the treatment and removal of planktonic cultures of legionella, but remains ineffective against sessile communities of the bacterium [ 28 , 29 ].…”

Quantitative Microbial Risk Assessment Applied to Legionella Contamination on Long-Distance Public Transport

“…At the time of our study, we found only one paper carried out on passenger trains, collecting water from plumbing and toilet water tanks before and after chlorine-based disinfection treatment [ 22 ]. Our monitoring results showed similar percentages of Legionella positivity, species, and serogroups as in pre-decontamination samples of Quaranta et al 2012 [ 22 ]; namely, they found more than 50% of water samples positive for Legionella , they identified only the L. pneumophila species, and the most frequently isolated was L. pneumophila sg1. Regarding the Legionella concentrations, our study found slightly higher values, but still with a geometric means around 10 3 CFU/L.…”

“…Although such water is not ingested, it can be aerosolized during the usage of sinks for handwashing, and it can create an exposure scenario to Legionella . LDT is rarely monitored for Legionella contamination [ 22 ] and, consequently, possible infection or illness risk has not yet been explored. To fill this gap of knowledge, the aims of this paper were: (i) to investigate Legionella contamination on LDT through the analysis of 6-year monitoring data from the faucet of toilet cabins and (ii) to develop a QMRA model for sink usage on LDT using monitoring data to understand the probability of Legionella infection in such exposure scenario.…”

Influence of Sampling Season and Sampling Protocol on Detection of Legionella Pneumophila Contamination in Hot Water / Paraugu Ņemšanas Sezonalitātes Un Paraugu Ņemšanas Metodes Ietekme Uz Legionella Pneumophila Kontaminācijas Noteikšanu Karstajš Ūdenī

“…The sampling method should be chosen depending on the purpose of sampling, such as post-outbreak investigation or preventive measurement. Sampling may be performed immediately after tap switching, or after at least one minute of water pre-flush, which is more representative for the characterisation of water quality in the system (Quaranta, 2012;Bedard, 2015).…”