Surveillance of Legionella pneumophila: Detection in Public Swimming Pool Environment.

The bacterium Legionella pneumophila is a ubiquitous microorganism naturally present in water environments. The actual presence of this opportunistic premise plumbing pathogen in recreational swimming pools and hot tubs in the northwestern part of Croatia has not been investigated. This study aimed to analyze the presence of the opportunistic pathogen L. pneumophila in public swimming pool water in Primorje-Gorski Kotar County (N = 4587) over a four-year period (2018-2021). Additionally, the second aim was to investigate the connection between the presence of L. pneumophila and pool water physicochemical parameters using mathematical predictive models. The presence of L. pneumophila was detected in six pool samples. Five positive samples were found in the water of indoor hot tubs filled with fresh water, and one positive sample in an outdoor recreational saltwater pool. A predictive mathematical model showed the simultaneous influence of chemical parameters dominated by the temperature in saltwater and freshwater pools, as well as the significant influence of free residual chlorine and trihalomethanes. Our results pointed out that keeping all physicochemical parameters in perfect harmony is necessary to reach the best disinfection procedure and to avoid the optimum conditions for L. pneumophila occurrence.

Polycyclic aromatic hydrocarbons and ecotoxicological characterization of seawater, sediment, and mussel Mytilus galloprovincialis from the Gulf of Rijeka, the Adriatic Sea, Croatia.

The pattern of spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in seawater, sediment, and mussels, potential toxicity of different matrices, and mussel anoxic survival from six sampling sites of the Gulf of Rijeka, the Adriatic Sea, Croatia was examined. The total concentrations of 10 PAHs vary from below detection limit to 305 ng/L in seawater, from 213 to 695 microg/kg dry weight in sediment and from 49.2 to 134 ng/g wet weight in mussel tissue. Combustion is the principal source of PAH contamination in seawater and sediment samples. Sediment samples are distinguished from the majority of seawater and mussel samples by the presence of high molecular weight PAHs, whereas mussels from majority of sampling sites tend to accumulate PAHs of lower molecular weight. The PAH dynamic between different matrices is complex and site specific. Toxicity of seawater and sediment organic extract is correlated with PAH content, indicating that PAHs are the predominant toxic compounds. There is no correlation between toxicity of mussel biological fluids and toxicity of seawater and sediment, or between toxicity of mussel biological fluid and PAH content in mussel, seawater, or sediment. There is a positive correlation between potential toxicity of mussel biological fluids and reduction of anoxic survival time. Mussel anoxic survival is influenced by the presence of complex mixture of toxic contaminants, not only PAHs. The relationship between PAH contents in different marine matrices and their ability to affect mussels revealed specific interactions between an organism and complex mixture of toxic contaminants present in the marine environment.