Legionella species colonization of water distribution systems, pools and air conditioning systems in cruise ships and ferries.

Georgia Goutziana,Kostantinos Gourgoulianis,Nikolaos E Stathakis,Varvara A Mouchtouri,Antonios Kavagias,Christos Hadjichristodoulou,Jenny Kremastinou,Maria Karanika

doi:10.1186/1471-2458-8-390

Abstract

BackgroundLegionnaires' disease continues to be a public health concern in passenger ships. This study was scheduled in order to investigate Legionella spp. colonization of water distribution systems (WDS), recreational pools, and air-conditioning systems on board ferries and cruise ships in an attempt to identify risk factors for Legionella spp. colonization associated with ship water systems and water characteristics.MethodsWater systems of 21 ferries and 10 cruise ships including WDS, air conditioning systems and pools were investigated for the presence of Legionella spp.ResultsThe 133 samples collected from the 10 cruise ships WDS, air conditioning systems and pools were negative for Legionella spp. Of the 21 ferries WDS examined, 14 (66.7%) were legionellae-positive. A total of 276 samples were collected from WDS and air conditioning systems. Legionella spp. was isolated from 37.8% of the hot water samples and 17.5% of the cold water samples. Of the total 96 positive isolates, 87 (90.6%) were L. pneumophila. Legionella spp. colonization was positively associated with ship age. The temperature of the hot water samples was negatively associated with colonization of L. pneumophila serogroup (sg) 1 and that of L. pneumophila sg 2 to 14. Increases in pH ≥7.8 and total plate count ≥400 CFU/L, correlated positively with the counts of L. pneumophila sg 2 to 14 and Legionella spp. respectively. Free chlorine of ≥0.2 mg/L inhibited colonization of Legionella spp.ConclusionWDS of ferries can be heavily colonized by Legionella spp. and may present a risk of Legionnaires' disease for passengers and crew members. Guidelines and advising of Legionnaires' disease prevention regarding ferries are needed, in particular for operators and crew members.

Highlights

Legionnaires' disease continues to be a public health concern in passenger ships
The sampling points were chosen according to the EWGLI guidelines [7] a) in the engine room, the hot water leaving the water heater, and when possible the circulating hot water returning to the heater, b) the outlet nearest to the entry of the hot water into the ship water distribution systems (WDS), and the most distal site within the WDS, c) showers or taps of crew members or passenger cabins on different decks to be representative of the different loops of the WDS
A total of 7 ferries WDS were contaminated with concentrations of ≥104 CFU/L in at least one sample, whereas 4 of 7 ferries were colonized with ≥105 CFU/L in at least one sample

Summary

Introduction

Legionnaires' disease continues to be a public health concern in passenger ships. It is well documented that cases of Legionnaires' disease (LD) have occurred among passengers of cruise ships and ferries [1,2]. A World Health Organization compendium published in 2001, showed that from 1970 to 2000, 51 incidents of LD were reported to be associated with ships, involving almost 200 cases, while 10 fatalities were recorded [3]. Water distribution systems [9] and whirlpool spas [6,10] of passenger ships have been identified as the source of infection, while a possible link with air-conditioning systems have been documented [11]

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