| Summary: | <p>Abstract</p> <p>Background</p> <p>In the last years, international traffic volume has significantly increased, raising the risk for acquisition of infectious diseases. Among travel-associated infections, increased incidence of legionellosis has been reported among travellers.</p> <p>Aim of our study was: to describe the frequency and severity of <it>Legionella </it>spp. contamination in ferries and cruise ships; to compare the levels of contamination with those indicated by the Italian ministerial guidelines for control and prevention of legionellosis, in order to assess health risks and to adopt control measures.</p> <p>Method</p> <p>A prevalence study was carried out on 9 ships docked at the seaports of northern Sardinia in 2004. Water samples were collected from critical sites: passenger cabins, crew cabins, kitchens, coffee bars, rooms of the central air conditioning system. It was performed a qualitative and quantitative identification of <it>Legionella </it>spp. and a chemical, physical and bacteriological analysis of water samples.</p> <p>Results</p> <p>Forty-two percent (38/90) water samples were contaminated by <it>Legionella </it>spp.. Positive samples were mainly drawn from showers (24/44), washbasins (10/22). <it>L. pneumophila </it>was isolated in 42/44 samples (95.5%), followed by <it>L. micdadei </it>(4.5%).</p> <p>Strains were identified as <it>L. pneumophila </it>serogroup 6 (45.2%; 19 samples), 2–14 (42.9%), 5 (7.1%) and 3 (4.8%). <it>Legionella </it>spp. load was high; 77.8% of the water samples contained > 10<sup>4 </sup>CFU/L.</p> <p>Low residual free chlorine concentration (0–0,2 mg/L) was associated to a contamination of the 50% of the water samples.</p> <p>Conclusion</p> <p><it>Legionella </it>is an ubiquitous bacterium that could create problems for public health.</p> <p>We identified <it>Legionella </it>spp. in 6/7 ferries. Microbial load was predominantly high (> 10<sup>4 </sup>CFU/L or ranging from 10<sup>3 </sup>to 10<sup>4 </sup>CFU/L). It is matter of concern when passengers are subjects at risk because of <it>Legionella </it>spp. is an opportunist that can survive in freshwater systems; high bacterial load might be an important variable related to disease's occurrence.</p> <p>High level of contamination required disinfecting measures, but does not lead to a definitive solution to the problem. Therefore, it is important to identify a person responsible for health safety in order to control the risk from exposure and to apply preventive measures, according to European and Italian guidelines.</p>
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