Prevalence and antimicrobial resistance of Salmonella serovars isolated from poultry in Ghana

Abstract

Poultry are possible sources of non-typhoidal Salmonella serovars which may cause foodborne human disease. We conducted a cross-sectional study to determine the prevalence of Salmonella serovars in egg-laying hens and broilers at the farm level and their susceptibility to antimicrobials commonly used in the poultry industry in Ghana. Sampling of faeces by a sock method (n = 75), dust (n = 75), feed (n = 10) and drinking water (n = 10) was performed at 75 commercial egg-laying and broiler farms in two regions of Ghana and skin neck (n = 30) at a local slaughterhouse from broilers representing different flocks. Salmonella was detected in 94/200 (47%) samples with an overall flock prevalence of 44·0%. Sixteen different serovars were identified with S. Kentucky (18·1%), S. Nima (12·8%), S. Muenster (10·6%), S. Enteritidis (10·6%) and S. Virchow (9·6 %) the most prevalent types. The predominant phage type of S. Enteritidis was PT1. All strains were susceptible to cefotaxime, ceftazidime and cefoxitin. Fifty-seven (60·6%) strains were resistant to one or more of the remaining nine antimicrobials tested by disk diffusion, of which 23 (40·4%) showed multi-resistance (resistance to ⩾3 classes of antimicrobials). Of the resistant strains (n = 57), the most significant were to nalidixic acid (89·5%), tetracycline (80·7%), ciprofloxacin (64·9%), sulfamethazole (42·1%), trimethoprim (29·8%) and ampicillin (26·3%). All S. Kentucky strains were resistant to more than two antimicrobials and shared common resistance to nalidixic acid or ciprofloxacin and tetracycline, often in combinations with other antimicrobials. PFGE analysis using XbaI of S. Kentucky demonstrated one dominant clone in the country. In conclusion, poultry produced in Ghana has a high prevalence of multi-resistant Salmonella and the common finding of clonal S. Kentucky in the Kumasi area warrants further investigations into the epidemiology of this serovar. There is an urgent need for surveillance and control programmes on Salmonella and use of antimicrobials in the Ghanaian poultry industry to protect the health of consumers.

Keywords: Salmonella; Antimicrobial resistance; Ghana; PFGE; phage-typing.

Fig. 1.

Dendogram showing clusters of XbaI PFGE of (a) Salmonella Kentucky (n = 14). Strain BUG1 and BUG2 are from the same farm but different flocks, ED3, ED4 and ED5 similarly from one farm but different flocks and MB2 and MB1 from the same farm but different flocks. The remaining strains were from different flocks on different farms. (b) S. Nima (n = 11). Strain D11 and D13 are from the same farm but isolated from different flocks. The remaining strains originate from different flocks at different farms. (c) S. Enteritidis (n = 8). PB05-1, PB05-2 and PD05-2 are from the same farm in the Accra region, but from different flocks. The remaining strains were obtained from different flocks and farms. (d) S. Muenster (n = 8) isolates from poultry farms in Ghana. All strains were from different flocks at different farms. Dice coefficient was used for the similarity analysis and clustering was done using unweighted pair-group method with arithmetic means with 1% band position tolerance and 0·50% optimization parameter. KB, PB and B, Salmonella from faecal sources; PD and D, Salmonella from dust; AYFe, Salmonella from feed.