Prevalence and characterization of Salmonella among humans in Ghana

Linda Aurelia Andoh; Shabana Ahmed; John Elmerdahl Olsen; Kwasi Obiri-Danso; Mercy Jemima Newman; Japheth Awuletey Opintan; Lisa Barco; Anders Dalsgaard

doi:10.1186/s41182-017-0043-z

Prevalence and characterization of Salmonella among humans in Ghana

Trop Med Health. 2017 Feb 10:45:3. doi: 10.1186/s41182-017-0043-z. eCollection 2017.

Authors

Linda Aurelia Andoh^{1

2}, Shabana Ahmed¹, John Elmerdahl Olsen¹, Kwasi Obiri-Danso², Mercy Jemima Newman³, Japheth Awuletey Opintan³, Lisa Barco⁴, Anders Dalsgaard¹

Affiliations

¹ Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigboejlen 4, 1870 Frederiksberg C, Denmark.
² Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
³ Department of Microbiology, University of Ghana Medical School, Korle-Bu, Accra, Ghana.
⁴ OIE, National Reference Laboratory for Salmonellosis, Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro Padova, Italy.

Abstract

Background: Non-typhoidal Salmonella (NTS) is a public health problem worldwide and particularly in Africa with high disease burden. This study characterized Salmonella isolates from humans in Ghana to determine serovar distribution, phage types, and antimicrobial resistance. Further, the clonal relatedness among isolates was determined.

Methods: One hundred and thirty-seven Salmonella isolates (111 clinical and 26 public toilet) were characterized using standard serotyping, phage typing, and antimicrobial susceptibility testing methods. The molecular epidemiology of common serovars (Salmonella Typhimurium and Salmonella Enteritidis) was established by pulsed field gel electrophoresis (PFGE).

Results: Twenty-two serovars were identified with S. Enteritidis, S. Typhimurium, and Salmonella Derby as the most dominant. One hundred and twelve isolates showed resistance to more than one antimicrobial. Fifty-eight (n = 58/112; 54.5%) strains were multi-resistant with low resistance to cephalosporins ceftazidime (8.0%), cefotaxime (4.5%), and cefoxitin (2.7%) with synergy to clavulanic acid indicating possible ESBLs. Isolates showed high resistance to trimethoprim (66.1%), tetracycline (61.6%), ampicillin (57.1%), sulfamethoxazole (46.4%), chloramphenicol (33.9%), and ciprofloxacin (25.0%). The most common resistance pattern of multi-resistant serovars was to ampicillin, chloramphenicol, sulphonamide, and trimethoprim. S. Enteritidis (18/43) strains reacted with typing phages but did not conform to any phage type with PT14B and PT4 as predominant definitive phage types. Six S. Typhimurium strains reacted but did not conform to any recognized phage type while seven were non-typable. The predominant definitive phage types were DT1 and DT22. PFGE patterns of human S. Enteritidis were closely related to patterns of poultry isolates obtained in a previous study in Ghana.

Conclusions: Cephalosporin resistance is uncommon among Salmonella from humans in Ghana. Poultry may be an important source of human salmonellosis. There is an urgent need for the implementation of routine surveillance of antimicrobial use and bacterial resistance among humans in Ghana.

Keywords: Antibiotic resistance; Ghana; Phage types; Salmonella; Serotypes.