Antimicrobial Resistance of Salmonella Isolates Recovered from Chickens Sold at Retail Outlets in Trinidad

This study determined the frequency of resistance of 135 isolates of Salmonella, including 15 serotypes recovered from chickens purchased from retail outlets (cottage processors and supermarkets) across Trinidad. Resistance to 16 antimicrobial agents was determined by using the disk diffusion method. Resistance among the isolates was related to the type of retail outlet, location of outlets, type of sample, and isolate serotype. Overall, all isolates exhibited resistance to one or more of the 16 antimicrobial agents tested. All isolates were sensitive to cefoxitin and norfloxacin, with the overall frequency of resistance ranging from 1.1% (sulfamethoxazole-trimethoprim) to 100.0% (ceftiofur and doxycycline). The frequency of resistance to tetracycline, ampicillin, ceftriaxone, amoxycillin-clavulanic acid, and chloramphenicol was significantly (P < 0.05) higher in isolates recovered from cottage processor outlets compared with those from supermarkets. The frequency of resistance to antimicrobial agents was significantly different only to kanamycin (P = 0.046) and enrofloxacin (P = 0.000) across seven counties in Trinidad). Regarding sample presentation (whole versus parts), the frequency of resistance was only significantly higher to gentamicin (P = 0.039) for chicken part isolates from cottage processor and to only tetracycline (P = 0.034) for isolates from whole carcasses from supermarkets. All the 135 Salmonella isolates exhibited multidrug resistance patterns. The high frequency of resistance to seven antimicrobial agents (erythromycin, streptomycin, ceftiofur, doxycycline, kanamycin, tetracycline, and ampicillin), some used in the poultry industry, coupled with the occurrence of multidrug resistance, may have potential therapeutic implications for broiler farmers in Trinidad.