ESBL resistance patterns among environmental and clinical bacterial isolates

Objectives

We have studied the phenotypic and genetic pattern among Extended Spectrum Beta-lactamase (ESBL) producing bacteria in the aquatic environment, and have compared the result with clinical samples from the same area.

Methods

Water samples have been collected at three different sites in the Helge river, Kristianstad community, Sweden. The first station is located before the outlet from the municipal sewage plant, the second just after the outlet and the third close to the Baltic Sea. Cultured bacterial isolates from the water and clinical isolates were analysed for phenotypic expression of ESBL related genes using the MAST-test, and genetically by PCR analyses of a set of ESBL genes, i.e. bla_CTX-M, bla_SHV, bla_TEM, and bla_OXA  

Results

Both clinical and environmental ESBL isolates were dominated by Escherichia coli and Klebsiella pneumoniae. Highest abundance of environmental ESBL isolates were obtained from the station close to the sewage outlet, the lowest close to the Baltic Sea. The gene cluster bla_CTX-M was the most common among all isolates (65%), followed by bla_{TEM (30%)}.  The bla_OXA and bla_SHV genes were more common in clinical isolates.

Conclusion

A majority of the ESBL bacteria were mediated by chromosomal genes, dominated by bla_CTX-M. However, bla_{OXA .}and bla_SHV were more common in clinical isolates. Further genetic analyses will be performed on more isolates, and on total bacterial community DNA.