The studies included 10 public indoor swimming pools and 3 public open-air swimming pools located in the city of Szczecin. In 2003, water samples were collected for detection of virulent amphizoic amoebae strains. In all pools, 16 strains of thermophilic Acanthamoeba spp. were isolated, 5 of which proved virulent for mice. No pathogenic strains were detected in the water sampled in the indoor swimming pools, and the virulent strains, AD 16, AD 148, AD 166, AM 17, and AM 148, were found only in the open-air swimming pools. The post-mortem studies of mice that had been inoculated with these strains revealed the amoebae invasions in brain, lungs, liver, kidneys, and spleen.
The role of the genus Acanthamoeba in the process of maintaining, multiplying and transmitting human pathogens has not been well recognized. The aim of our study was to evaluate the association of potentially pathogenic Acanthamoeba spp. with bacteria in strains recently isolated from Lake Malta near the city of Poznań, Poland. Most of the isolated amoebae belonged to the species A. castellanii and A. rhysodes. The majority of the isolates were pathogenic for mice and amoebae could be recovered from their brains and lungs. In those cases when amoebae could not be recovered from the autopsy material histopathological analysis showed changes in tissues indicating bacterial infection. We found that approximately 50% of the isolates were associated with endosymbiotic or endocytobiotic bacteria, e.g., Proteus sp., Micrococcus sp., Chryseobacterium meningosepticum, Clostridium perfringens, Escherichia coli, Salmonella sp., Legionella pneumophila and other species. The presence of bacteria residing inside free-living amoebae possess a great challenge in terms of disease control and sanitation of contaminated water sources.