Salmonella enterica resistant to antimicrobials in wastewater effluents and black-headed gulls in the Czech Republic, 2012

- We documented the continuous presence of resistant Salmonella in wastewater.
- Using PFGE, we confirmed identical clusters of Salmonella in wastewater and gulls.
- Wastewater aids to the spreading of resistant Salmonella in the environment.
- Prevalence of resistant Salmonella gull isolates in Czech Republic increased.

We investigated the presence and epidemiological relatedness of Salmonella isolates from a wastewater treatment plant (WWTP) in Brno, Czech Republic and from nestlings of black-headed gulls (Chroicocephalus ridibundus) at the Nove Mlyny waterworks, situated 35 km downstream from the WWTP. During 2012, we collected 37 wastewater samples and 284 gull cloacal swabs. From wastewater samples, we obtained 89 Salmonella isolates belonging to 19 serotypes. At least one resistant strain was contained in 89% of those samples. Ten different serotypes of Salmonella were detected in 38 young gulls, among which 14 (37%) were resistant to antimicrobials. Wastewater isolates were mostly resistant to sulphonamides and tetracycline, gull isolates to tetracycline and ampicillin. We detected the occurrence of blaTEM-1,tet(A), tet(B), tet(G), sul1, sul2, sul3, floR and strA resistance genes. For the first time, we identified a class 1 integron with the dfrA12-orfF-aadA2 gene cassette in S. Infantis. Using pulsed-field gel electrophoresis, we confirmed the presence of identical clusters of S. Agona, S. Enteritidis PT8, S. Infantis and S. Senftenberg in wastewater and black-headed gulls, thus indicating the possibility of resistant Salmonella isolates spreading over long distances in the environment.

PFGE analysis of salmonellae from wastewater and gulls.Lanes C: control strain - S. Braenderup H9812, L. 1: S. Senftenberg - gull, L. 2: S. Senftenberg - wastewater, L. 3: S. Agona - wastewater, L. 4: S. Agona - wastewater, L. 5: S. Agona - gull, L. 6: S. Agona - gull, L. 7: S. Agona - gull, L. 8: S. Agona - gull.108