International Journal of One Health

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Characterization of Salmonella Isolates from Municipal Sewage, Patients, Foods, and Animals in Greece Using Antimicrobial Susceptibility Testing and Pulsed Field Gel Electrophoresis


Affiliations
1 National Reference Centre for Salmonella, National School of Public Health & Central Public Health Laboratory, Hellenic Centre of Disease Control and Prevention, 16672 Vari, Greece
2 Laboratory of Bacterial Diseases, Veterinary Research Institute, National Agricultural Foundation, NAGREF Campus, 57001 Thermi, Greece
3 Laboratory of Microbiology, School of Veterinary Medicine, Aristotle University, University Campus, 54124 Thessaloniki, Greece
 

Aims: We aimed to compare Salmonella isolates from different sources using molecular and phenotypic methods, targeting better possibility of understanding the epidemiology of this organism in the Greek context with emphasis in municipal wastewater.

Materials and Methods: In this study, we used pulsed field gel electrophoresis (PFGE) in combination with antimicrobial susceptibility testing to analyze a total of 88 Salmonella Enterica isolates from municipal sewage (n=25), humans (n=36), animals (n=24), and foods (n=3) in Greece.

Results: The higher resistance rates were found to the following antimicrobials: streptomycin (59.1%), tetracycline (47.7%), nalidixic acid (46.6%), ampicillin (37.5%), and oxolinic acid (35.2%). Resistance to ciprofloxacin was not observed; 22 isolates (25%) were sensitive to all 9 antimicrobials, 36%, 25% and 12% of human, animal and wastewater origin, respectively, showing a significant difference. Salmonella ser. Hadar was the serovar with the highest resistance rates followed by Salmonella ser. Anatum and Salmonella ser. Typhimurium; Salmonella ser. Infantis strains were almost pansusceptible. Cluster analysis did not reveal close genetic relationship between human animal food and wastewater strains belonging to the same serovars. In most of the cases, distinct clusters were observed between human and non-human isolates indicating diversity and no epidemiological connection.

Conclusion: This study indicates that municipal wastewater would be of interest to further monitor the community's prevalence of subclinical or non-reported S. Enterica infections.


Keywords

Salmonella, Wastewater, Sewage, PFGE, Antimicrobial Resistance.
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  • Characterization of Salmonella Isolates from Municipal Sewage, Patients, Foods, and Animals in Greece Using Antimicrobial Susceptibility Testing and Pulsed Field Gel Electrophoresis

Abstract Views: 234  |  PDF Views: 96

Authors

Theofilos Papadopoulos
National Reference Centre for Salmonella, National School of Public Health & Central Public Health Laboratory, Hellenic Centre of Disease Control and Prevention, 16672 Vari, Greece
Antonios Zdragas
Laboratory of Bacterial Diseases, Veterinary Research Institute, National Agricultural Foundation, NAGREF Campus, 57001 Thermi, Greece
Georgia Mandilara
National Reference Centre for Salmonella, National School of Public Health & Central Public Health Laboratory, Hellenic Centre of Disease Control and Prevention, 16672 Vari, Greece
Georgios Vafeas
Laboratory of Bacterial Diseases, Veterinary Research Institute, National Agricultural Foundation, NAGREF Campus, 57001 Thermi, Greece
Virginia Giantzi
Laboratory of Bacterial Diseases, Veterinary Research Institute, National Agricultural Foundation, NAGREF Campus, 57001 Thermi, Greece
Evanthia Petridou
Laboratory of Microbiology, School of Veterinary Medicine, Aristotle University, University Campus, 54124 Thessaloniki, Greece
Alkiviadis Vatopoulos
National Reference Centre for Salmonella, National School of Public Health & Central Public Health Laboratory, Hellenic Centre of Disease Control and Prevention, 16672 Vari, Greece

Abstract


Aims: We aimed to compare Salmonella isolates from different sources using molecular and phenotypic methods, targeting better possibility of understanding the epidemiology of this organism in the Greek context with emphasis in municipal wastewater.

Materials and Methods: In this study, we used pulsed field gel electrophoresis (PFGE) in combination with antimicrobial susceptibility testing to analyze a total of 88 Salmonella Enterica isolates from municipal sewage (n=25), humans (n=36), animals (n=24), and foods (n=3) in Greece.

Results: The higher resistance rates were found to the following antimicrobials: streptomycin (59.1%), tetracycline (47.7%), nalidixic acid (46.6%), ampicillin (37.5%), and oxolinic acid (35.2%). Resistance to ciprofloxacin was not observed; 22 isolates (25%) were sensitive to all 9 antimicrobials, 36%, 25% and 12% of human, animal and wastewater origin, respectively, showing a significant difference. Salmonella ser. Hadar was the serovar with the highest resistance rates followed by Salmonella ser. Anatum and Salmonella ser. Typhimurium; Salmonella ser. Infantis strains were almost pansusceptible. Cluster analysis did not reveal close genetic relationship between human animal food and wastewater strains belonging to the same serovars. In most of the cases, distinct clusters were observed between human and non-human isolates indicating diversity and no epidemiological connection.

Conclusion: This study indicates that municipal wastewater would be of interest to further monitor the community's prevalence of subclinical or non-reported S. Enterica infections.


Keywords


Salmonella, Wastewater, Sewage, PFGE, Antimicrobial Resistance.