Characterization of Salmonella spp. from wastewater used for food production in Morogoro, Tanzania
Wastewater use for crop irrigation and aquaculture is commonly practiced by communities situated close to wastewater treatment ponds. The objective of this study was to characterize Salmonella spp. and their antimicrobial susceptibility patterns among isolates from wastewater and Tilapia fish. A total of 123 Salmonella spp. isolates were isolated from 52 water and 21 fish intestinal samples. Genotyping of Salmonella spp. isolates was done by Pulsed-field Gel Electrophoresis (PFGE). Antimicrobial susceptibility testing was done by the minimal inhibitory concentration (MIC) technique. A total of 123 Salmonella spp. isolates represented 13 different serovars and 22 PFGE groups. Salmonella serovars showed resistance to 8 out of 14 antimicrobials; sulfamethaxazole (94%), streptomycin (61%), tetracycline (22%), ciprofloxacin and nalidixic acid (17%), trimethoprim (11%); gentamycin and chloramphenicol (6%). Salmonella Kentucky, S. Chandans, S. Durban and S. Kiambu showed multiple antimicrobial resistance to 7, 6 and 3 antimicrobials, respectively. This study has demonstrated that wastewater at the study sites is contaminated with Salmonella spp. which are resistant to common antimicrobials used for treatment of diseases in humans. Wastewater may, therefore, contaminate pristine surface water bodies and foodstuffs including fish and irrigated crops as well as food handlers.
KeywordsAntimicrobial resistance Fish intestinal Salmonella serovars Tilapia
This work was part of the PhD study program. Authors are very grateful to the Danish International Development Assistance (DANIDA) through ‘Safe Water for Food’ (SaWaFo) project for the financial support. We extend many thanks to Ms Gitte Petersen for her guidance during Laboratory work and Ms Vivian Etsiapa (Kwame Nkurumah University of Science and Technolgy, Ghana) for her assistance in laboratory work at the Department of Veterinary Disease Biology, University of Copenhagen in Denmark. Finally, we acknowledge Ms Barco Lisa at the OIE and Italian National Reference Laboratory for Salmonellosis, Istituto Zooprofilattico Sperimentale delle Venezie, Padova, Italy for the serotyping work.
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Conflict of interest
Authors of this paper have no conflict of interest.
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