Comparison of thermotolerant coliforms and Escherichia coli densities in freshwater bodies

Fecal bacterial indicator analyses have been widely used for monitoring the water quality. This study was designed to determine the ratio between the density of Escherichia coli and other Thermotolerant Coliforms (TtC) bacteria from freshwater samples collected for a two-year period of monitoring. TtC were enumerated by membrane filtration on mFC agar. E. coli enumeration was done by two methods: TtC colonies identified in mFC were inoculated in EC-MUG or water samples were filtered and inoculated in modified mTEC agar media, and both methods were compared for quantitative recovery of E. coli. The results pointed out a mean percentage of E. coli among other thermotolerant coliforms (E. coli/TtC ratio) of 84.3% in mFC media. Taking these results into account, a mandatory standard of 1000 thermotolerant coliforms would correspond to 800 E. coli and the adoption of these E. coli based standards will represent a major improvement for the monitoring of freshwater quality.

Aeromonas spp. and microbial indicators in raw drinking water source

Aeromonas species are autochtonous in the aquatic environment and some of them have been associated with health effects like wound infections, septicemia and diarrhoeal illness. In this study, the occurrence of Aeromonas spp. and microbial indicators in raw drinking water from wells, springs, fountains and mineral waters was evaluated. A total of 126 water samples was analyzed for Aeromonas spp. by the membrane filtration technique using ADA media and by P/A test. Typical colonies of Aeromonas spp. were submitted to biochemical tests for species differentiation. Toxin production was tested using Y-1 mouse adrenal cells. Coliforms and heterotrophic bacteria were enumerated by membrane filtration and pour plate techniques, respectively. P. aeruginosa, C. perfringens and fecal streptococci were determined by P/A method. Aeromonas spp. were isolated in 36.5 percent of the samples, whereas total and thermotolerant coliforms were detected in 51.2 percent and in 23.8 percent of the samples, respectively. C. perfringens, fecal streptococci and P. aeruginosa were present in 16.5 percent, 20.4 percent and 3.8 percent of the samples, respectively. The concentrations of heterotrophic bacteria were higher than 1,0x10³ CFU/mL in 52.5 percent of the samples. A. hydrophila was the most frequent species, followed by A. allosaccharophila,A. jandaei,A.sobria and HG2. A heat label toxin was detected in 13 from the 58 strains tested. These data show that the drinking water sources analyzed can represent a risk for human health. It is important to consider that wells and springs are used as drinking water supply in poor areas and rural regions, where undernourished people more susceptible to infections by these microorganisms predominate.

Bactérias do gênero Aeromonas são naturais no ambiente aquático e algumas espécies podem causar infecções em humanos como feridas, septicemia e diarréia. Este trabalho objetivou avaliar a ocorrência de Aeromonas sp. em 126 amostras de água de poços, nascentes, fontes e água mineral, e associar sua presença com indicadores microbianos de contaminação. Foi utilizada a técnica de membrana filtrante com o meio ADA e o teste P/A. Colônias típicas de Aeromonas sp. foram submetidas a testes bioquímicos para identificação da espécie. A produção de toxina foi avaliada utilizando-se células Y-1 de adrenal de camundongo. Coliformes e bactérias heterotróficas foram analisados através de filtração em membrana e pela técnica de inoculação em profundidade, respectivamente. P. aeruginosa, C. pefringens e os estreptococos fecais foram determinados pelo teste P/A. Aeromonas sp. foi isolada em 36,5 por cento das amostras, enquanto que os coliformes totais e termotolerantes estavam presentes em 51,2 por cento e 23,8 por cento das amostras, respectivamente. C. perfringens, estreptococos fecais e P. aeruginosa foram detectados em 16,5 por cento, 20,4 por cento e 3,8 por cento das amostras respectivamente. Concentrações de bactérias heterotróficas superiores a 1,0x10³ UFC/mL ocorreram em 52,5 por cento das amostras. A. hydrophila foi a espécie mais isolada, seguida por A. allosaccharophila, A. jandaei, A. sobria e HG2. Uma toxina termolábil foi detectada em 13 dos 58 isolados analisados. Portanto, as fontes de água de consumo humano analisadas podem representar um risco para a saúde humana. É importante considerar que fontes, poços e nascentes são utilizadas como suprimento de água em áreas pobres e regiões rurais, onde predominam pessoas com problemas de desnutrição, mais suscetíveis a doenças infecciosas.