Diversity and molecular characterization of the virulence genes of antibiotic-resistant Salmonella strains isolated from bovine faeces in Abidjan district (Côte d'Ivoire)

The emergence of potentially pathogenic and antibiotic-resistant Salmonella strains in livestock has become a public health concern and is the subject of increased scientific interest. 

The overall objective of this study is to determine the diversity and molecularly characterize the virulence of antibiotic-resistant Salmonella strains isolated from cattle faeces in the district of Abidjan (Côte d'Ivoire).

Salmonella strains were isolated from various samples of fresh cattle faeces using conventional methodology in accordance with ISO 6579:2002 (E), and the identity of the strains was then confirmed by MALDI-TOF mass spectrometry, followed by the determination of the different serotypes. An antibiotic sensitivity test was used to determine the resistance profiles of the isolated strains. The search for different virulence genes was carried out using the PCR technique with specific primers (invA, spvC, iroN and pefA, etc.). 

Thus, out of a total of 420 faecal samples analysed, 84 Salmonella strains (20%) were isolated. Serotyping detected 50 different serotypes, with a predominance of Salmonella serotype II. The resistance profile of the Salmonella strains showed relatively high levels of resistance to tetracycline, minocycline and colistin, with rates ranging from 20.2% to 33.3%. However, low levels of resistance were observed to β-lactams, aminoglycosides, fluoroquinolones and trimethoprim/sulfamethoxazole. PCR testing for virulence genes showed that these strains possess at least one virulence gene. In Salmonella, the invA, spvC and iroN genes were detected in 100%, 3.9% and 53.9% of cases, respectively. 

Poor antibiotic use practices in livestock farming contribute to the spread of potentially pathogenic and antibiotic-resistant bacteria among the human population. Hence the need to collect data to develop strategies based on a One Health approach in order to protect public health in Côte d'Ivoire.