Prevalence of Multiple Drug-Resistant Escherichia coli from Chicken, Pig and Nile Tilapia (Oreochromis nilotica} Intestines Sold in Wet Markets in Manila and the Conjugative Transferability of the Resistance

摘要

One hundred eighty (180) Escherichia coli isolates from chicken, pig and Nile tilapia intestines sold in wet markets in Manila were studied for their antimicrobial susceptibility patterns using the disc diffusion method, and for conjugative transferability of the resistance. The highest prevalence of resistance in E. coli from all animals was to tetracycline and trimethoprim/suifamethoxazole, the two most widely used antimicrobials in feeds locally. Percentage resistance in isolates from pigs was 93.33% for both antimicrobials, 58.33% for tetracycline and 41.67% for trimethoprim/suifamethoxazole in isolates from chickens, and 38% and 12% to tetracycline and trimethoprim/suifamethoxazole, respectively, in isolates from fish. A high 38.33% of E. colifrom chickens was resistant to the quinolone nalidixic acid, and 25% were resistant to the fluoroquinolone ciprofloxacin compared to those from pigs, where only 10% of the isolates were resistant to nalidixic acid and 5% to ciprofloxacin, and those fromfish, with 5% isolates resistant to nalidixic acid and 0% to ciprofloxacin. Quinolones and fluoroquinolones are mostly used in poultry. The isolates from the different animals also showed varying resistance to ampicillin (2% of isolates from fish, 23.33%from pigs and 38.33% from chickens), chloramphenicol (0%, 6.67% and 20% of isolates from fish, chickens and pigs, respectively), gentamicin (0% isolates from fish, 5% from pigs and 13.33% from chickens), amikacin (0% isolates from fish and pigs, 3.33% from chickens), aztreonam (1.67% of isolates from pigs and chickens, and 2% from fish), cefotaxime (0% resistant isolates from fish and pigs, 1.67% from chickens), cefoxitin (0% resistant isolates from pigs, 3.33% and 5% from chickens and fish, respectively) and ceftazidime (0% resistant isolates from fish and pigs, 3.33% from chickens). All of the isolates were susceptible to ceftriaxone. Isolates that screened positive for extended-spectrum beta-lactamase (ESBL) production were negative for ESBL usingthe confirmatory double-disc synergy method. All the tested E. coli isolates completely transferred their resistance determinants to a susceptible E. coli through conjugation, converting it to a multiple resistant strain. The study showed high prevalenceof E. coli isolated from the intestines of the animals studied that were resistant to multiple antimicrobials, especially to those that are most commonly incorporated in feeds. It also demonstrated the conjugative transferability of all resistance determinants of the isolates.