The study investigated 110 Enterobacteriaceae isolates from broiler chickens isolated from Sharkia poultry farms and analyzed the isolates antimicrobial resistance and the presence of integrons as a potential basis for this resistance. Antibiotic susceptibilities against 12 different antibiotics were determined by the disk diffusion method. Prevalences and classes of integrons were then detected in multi-drug resistant (MDR) strains using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) followed by sequencing of the variable parts. Fifty-three isolates were MDR (resistant to three or more antimicrobial agents). High resistance was detected for rifamycin (82.7%), erythromycin (67.2%), and amoxicillin-clavulanic acid (63%). Classes 1 and 2 integrons were detected in 38 of 53 MDR Enterobacteriaceae isolates of which the most common were Salmonella species (n=19), followed by Escherichia coli (12), Klebsiella pneumoniae (3), Proteus species (3), and Citrobacter freundii (1). Three isolates only harbored class 1 integrons while the remaining 35 isolates carried class 2. All class 1 integron positive isolates exhibited the same gene cassettes arrangements: 1.) dfrA12-orfF-aadA27 (1.6 kbp); 2.) aadA23 (1.0 kbp); and 3.) dfrA15 (0.8 kbp). Moreover, four different gene cassettes were identified within class 2 integrons: 1.) dfrA1-sat2-aadA30 (2 kbp) in all isolates; 2.) sat2-aadA1 (1.7 kbp) in only one isolate; 3.) catB2 (0.9 kbp) in four isolates; and 4.) a new variant of sat2 (0.65 kbp) in three isolates. Efforts should be made to introduce surveillance programs for monitoring antimicrobial resistance that could potentially be transmitted from broiler chickens to human via integrons.
Keywords: Enterobacteriaceae; Gene cassettes.; Integrons; Multidrug resistance; Poultry; RFLP.