Staphylococci in Polluted Waters and in Waters of Uninhabited Areas

Abstract

The aim was to study the occurrence of staphylococci in southern Finland using both the modified Vogel-Johnson (VJP) and the M-5LSMA media in the MF technique. The study involved brooks and small lakes in uninhabited areas and sparsely populated farming areas as well as effluents from sewage treatment plants. Fecal indicator bacteria were determined simultaneously in all these samples. Median colony counts on both of the staphylococcal media in 100 mL samples were 1 to 2 for uninhabited areas, 60 to 110 for agricultural areas and 1000 to 1600 for treated wastewater. The maximum values were much higher in all the environments. The M-5LSMA recovered at least as many staphylococci as the VJP medium, but was more selective. Strains isolated from pristine waters and from wastewater were identified with the API 20 Staph kit. Six different species of staphylococci were recovered on the VJP medium and ten on the M-5LSMA medium. About one third of the isolates could not be identified to species level. Only 2% of the isolates from wastewater were Staphylococcus aureus whereas 18 % of the isolates from uninhabited areas belonged to this species. The identification was confirmed with the coagulase and DNAse tests.