Occurrence, risk factors, serotypes, and antimicrobial resistance of Salmonella strains isolated from imported fertile hatching eggs, hatcheries, and broiler farms in Trinidad and Tobago

Abstract

This cross-sectional study was conducted to determine the occurrence, risk factors, and characteristics of Salmonella isolates recovered from imported fertile broiler hatching eggs, hatcheries, and broiler farms in Trinidad and Tobago. Standard methods were used to isolate and characterize Salmonella isolates from two broiler hatcheries and 27 broiler farms in the country. The frequency of isolation of Salmonella was 0.0% for imported fertile hatching eggs (0 of 45 pools of 10 eggs each, i.e., 450 eggs), 7.6% for hatcheries (12 of 158 samples), and 2.8% for broiler farms (24 of 866 samples) (P = 0.006). Stillborn chicks at hatcheries had the highest prevalence of Salmonella (7 of 28 samples, 28.0%), whereas on broiler farms the cloacal swabs had the highest prevalence of Salmonella (15 of 675 samples, 2.2%). None of the 15 farm management and production practices investigated were significantly associated (P > 0.05) with the isolation of Salmonella. The predominant Salmonella serotypes were Kentucky (83.3%) and Infantis (62.5%) among hatchery and farm isolates, respectively. The disk diffusion method revealed frequencies of antimicrobial resistance (i.e., resistance to one or more agents) of 44.0% (11 of 25 isolates) and 87.5% (35 of 40 isolates) at hatcheries and broiler farms, respectively (P = 0.0002). Antimicrobial resistance among hatchery isolates was highest (28.0%) to doxycycline and kanamycin and was very high (>65%) among farm isolates to sulfamethoxazole-trimethoprim, gentamicin, ceftriaxone, kanamycin, and doxycycline. Multidrug resistance (MDR; i.e., resistance to antimicrobial agents from three or more classes) was exhibited by 4.0 and 85.7% of Salmonella isolates recovered from several environmental and animal sources at the hatcheries and farms, respectively (P < 0.0001). The high level of antimicrobial resistance and the presence of MDR among Salmonella isolates from broiler farms highlight the therapeutic implications and the potential for MDR strains to enter the food chain.