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Bakterie z rodziny Enterobacteriaceae w wodach przybrzeżnych jeziora Wigry w latach 1995-1999

Korzeniewska E., Niewolak S., Filipkowska Z.

Inżynieria i Ochrona Środowiska

2001

T. 4, nr 1

61-72

Przedstawiono wyniki badań ilościowych i jakościowych drobnoustrojów z rodziny Enterobacteriaceae w wodzie kąpielisk jeziora Wigry. Próby wody do badań mikrobiologicznych pobierano na terenie 8 najbardziej uczęszczanych kąpielisk jeziora Wigry w odstępach jednomiesięcznych od czerwca do września w latach 1995-1999. Próby wody pobierane ze stanowisk usytuowanych na terenie Ploso Północnego charakteryzowały się wyższą liczebnością drobnoustrojów z rodziny Enterobacteriaceae w porównaniu z próbami wody pobieranymi na pozostałych stanowiskach. Spośród bakterii z rodziny Enterobacteriaceae najliczniej były reprezentowane rodzaje Enterobacter, Escherichia, Citrobacter i Klebsiella. Rzeka Czarna Hańcza, do której dopływają ścieki z oczyszczalni ścieków w Suwałkach, ma istotny wpływ na zanieczyszczenie jeziora Wigry.

Objectives: Public bath waters are used for recreation and bathing purposes, so their sanitary and bacteriological condition is important for the users safety. Because some infections are caused by bacteria from Enterobacteriaceae family, the aim of the study was detection and analysis of occurrence and differentiation of the waterborne bacteria! pathogens from this family in the water of Wigry Lake public bath areas. Wigry Lake is situated in north-eastern Poland, in the area of Wigry National Park. Methods: Eight sampling sites in the most frequently attended public bath areas of the lake, situated near landing stages, camping sites and holiday resorts were investigated. The water samples were collected from June 1995 to September 1999 at one-month intervals, during bathing season. The samples were taken from depth of 0.3 m at each site, poured into 250 ml sterile bottles with water-tight glass closures, transported at 4-^6°C to the laboratory and subjected to bacteriological analyses within 12 hours from collection. Microbial investigations involved the membrane filtration method (with 0.22 urn pore-size filters, Millipore). Volume ranging 1,10 and 50 ml of the sample were filtered through filter and the filters were incubated on solid media Endo Agar in the plates. Another 50 ml of the same water sample was inoculated into 50 ml of Mueller-Kaufmann's medium. Plates and flasks were incubated at 37°C for 24 or 48 hours. The isolates were preliminary screened using the following tests: cytochromeoxidase, Gram stain and motility. Only the strains found to be oxidase and Gram negative were considered to be potential Enterobacteriaceae. Individual colonies from each plate were then picked up, tested for activity and inoculation on solid media Chromocult Agar, Rambach Agar and SS Agar. The strains were then presumptively identified with API 20E strips (bioMerieux). Results: The results of this study allowed to make a qualitative evaluation and provide information on the presence/absence of microorganisms associated with pathogenicity in humans in surface waters. The concentration of Enterobacteriaceae colonies ranged from 2 o 10' to 4.5 o 10s in 100 ml of water. The highest number of Enterobacteriaceae was noticed in August and September (except bathing season 1996). The most abundant species were: Enterobacter cloacae, Enterobacter agglomerans, Escherichia coli and Citrobacter diversus. During the bathing period, relatively lower incidence of Escherichia coli (15%) could be ascribed to contamination from different additional sources and/or by excrements of sick people or disease carriers. The overall presence of Salmonella spp. recovered 22.6% of total (160) water samples; higher frequencies of this genus were found in those sites, which were situated close to villages and animal farms. The public bath areas in northern part of Wigry Lake (called Northern Ploso) showed the highest number of the waterborne bacterial from Enterobacteriaceae family. The Czarna Hańcza River, which brings a lot of pollution to northern part of Wigry Lake has immense influence on the sanitary state of Wigry Lake. The presence of pathogenic bacteria in absence of fecal coliforms, confirms that sanitary evaluation of water based exclusively on numbers of indicatory bacteria is not sufficient.