Prevalence of multiple drug-resistant Escherichia coli from the chicken, pig and Nile Tilapia (Oreachromis niloticus)intestines sold in wet markets in Manila [Philippines] and the conjugative transferability of the resistance

One hundred eighty (180) Escherichia coli isolates from chicken,pig, and Nile tilapia intestines sold in wet markets in Manila (Philippines) 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 tetracyline and trimethoprim/sulfamethoxazole 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 the trimetoprim/sulfamethoxazole in isolates from chickens, and 38% and 12% to tetracycline and trimethoprim/sulfamethoxazole,respectively in isolates from fish. A high 38.33% of E. coli from chickens was resistant to quinolone nalidixic acid, and 25% were resistant to fluoroquinolone ciprofloxacin compared to those from pigs, where only 10% of the isolates were resistant to nalidixic acid and 5% to ciprofloxacin, and those from fish, with 5% isolates resistant to nalidixic acid and 0% ciprofloxacin. Quinolones and fluroquinilones 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), chloraphenicol (0%, 6.67% and 20% from isolates from fish, chickens and pigs, respectively), gentamicin (0% isolates from fish, 5% from pigs and 3.33% 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 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 using the 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 into a multiple resistant strain. The study showed high prevalence of E. coli isolated from the intestines of the animals studied that were resistant to multiple antimicrobial, especially to those that are most commonly incorporated in feeds.It also demonstrated the conjugative transferability of all resistant determinants of the isolates.