Diversity and antimicrobial susceptibility of Salmonella enterica serovars isolated from pig farms in Ibadan, Nigeria

Animals including food animals play a significant role in the epidemiology of Salmonella enterica. The control requires identification of sources and institution of targeted interventions. This study investigates the diversity of S. enterica serovars, antimicrobial susceptibility, and occurrence of plasmid-mediated quinolone resistance (PMQR) genes in pigs in Ibadan, Nigeria.

Pooled fresh pen floor fecal samples of pigs collected from 31 pig farms were cultured; the Salmonella isolates were serotyped and their antimicrobial susceptibility was determined. PMQR genes were screened by polymerase chain reaction. The 229 Salmonella isolates were made of 50 serovars predominated by rare serovars Salmonella Give (n = 36; 15.7 %), Salmonella Brancaster (n = 17; 7.4 %), Salmonella Colindale (n = 15; 6.6 %), Salmonella Elisaberthville (n = 13; 5.7 %), Salmonella Hillingdon (n = 13; 5.7 %), and Salmonella Kingston (n = 13; 5.7 %).

The most widely distributed serovars among the farms were Salmonella Give (six farms) and Salmonella Elisaberthville (six farms). Resistance to chloramphenicol, sulfonamides, nalidixic acid, streptomycin, and tetracycline ranged from 11.6 % (n = 26) to 22.8 % (n = 51). Resistance ciprofloxacin and gentamicin was low (n = 2; 0.9 %).

Multiply resistant isolates included Salmonella Kentucky, the most resistant serovar. qnrB19 was found in two isolates of Salmonella Corvallis and one isolate of Salmonella Larochelle, respectively, while qnrS1 was found in two isolates of Salmonella Derby. Other PMQR genes were not detected. Pigs constitute an important source of diverse Salmonella serovars in Ibadan.

The isolates were more resistant to old antimicrobials with some multiple resistant. Control measures and regulation of antimicrobials are warranted.