Vigilance for Salmonella in Feedstuffs Available in Costa Rica: Prevalence, Serotyping and Tetracycline Resistance of Isolates Obtained from 2009 to 2014

Relevant epidemiological information is provided in this report for Salmonella based on data obtained from a Costa Rican surveillance program for animal feeds. In addition to prevalence, a description in terms of serotypes and tetracycline (TET) resistance of the isolates is included. A total of 1725 feed and feed ingredients samples were analyzed during 2009 and 2014, from which 110 Salmonella strains were recovered (76 from poultry, 23 from meat and bone meal [MBM], 3 from pet foods, and 8 from other feed). Retrieved isolates were serotyped and tested for minimum inhibitory concentration (MIC) against TET. Salmonella strains were found mainly from poultry feed (different growth stages, n=76/110; 69.1%) and MBM (n=23/109; 21.1%). The rest of the isolates were recovered from feather meal, pet food, fish meal (n=3/110; 2.3% each) and swine feed (n=1/110; 0.9%). From the different serotypes recovered (n=21), the most common were Salmonella Give (n=18; 13.8%) and Salmonella Rissen (n=6; 4.6%) for MBM and Salmonella Havana (n=14; 10.8%), Salmonella Rissen, Salmonella Soerenga, and Salmonella Schwarzengrund (n=8; 6.2% each) in poultry feed. Recovered strains were regarded to be sensitive or have an intermediate resistance to TET as evidenced by their MIC50 and MIC90 concentrations of 4 and 8g/mL for MBM and poultry feed, respectively. Compound feed and MBM samples exhibited strains characterized by 86.8 and 88.9% of the isolates classified (according to CLSI, 2015) as sensitive, 7.7 and 3.7% as intermediate, and 5.5% (with >256g/mL as the highest concentration) and 7.4% (with 64g/mL as the highest concentration) as resistant to TET, respectively. Salmonella serovars Anatum and Havana exhibited the highest resistance profile >256 and 128g/mL, respectively. Hence, MBM and poultry feed seem to be a target of interest if Salmonella incidence is to be controlled. Serotypes recovered have in the past demonstrated pathogenic capability; therefore, hereafter a stricter surveillance program may be in order.