High Frequency and Diversity of Tetracycline Resistance Genes in the Microbiota of Broiler Chickens in Tunisia

SIMPLE SUMMARY: The extensive use of tetracyclines in clinical practice and livestock has subjected bacterial populations to selection pressure and increased the prevalence of tetracycline resistance, one of the most abundant antibiotic resistances among pathogenic and commensal microorganisms. In the present survey, DNA extracted from cloacal swabs from 195 broiler chickens in Tunisia were molecularly tested for 14 tetracycline resistance genes. A high frequency and diversity of tetracycline resistance genes in the chickens sampled were detected. The results confirm the antimicrobial resistance urgency in Tunisia’s poultry sector and suggest that the investigation of antibiotic resistance genes directly in biological samples could be a useful means for epidemiological studies on the spread of the antimicrobial resistance. ABSTRACT: Tetracycline resistance is still considered one of the most abundant antibiotic resistances among pathogenic and commensal microorganisms. The aim of this study was to evaluate the prevalence of tetracycline resistance (tet) genes in broiler chickens in Tunisia, and this was done by PCR. Individual cloacal swabs from 195 broiler chickens were collected at two slaughterhouses in the governorate of Ben Arous (Grand Tunis, Tunisia). Chickens were from 7 farms and belonged to 13 lots consisting of 15 animals randomly selected. DNA was extracted and tested for 14 tet genes. All the lots examined were positive for at least 9 tet genes, with an average number of 11 tet genes per lot. Of the 195 animals tested, 194 (99%) were positive for one or more tet genes. Tet(L), tet(M) and tet(O) genes were found in 98% of the samples, followed by tet(A) in 90.2%, tet(K) in 88.7% and tet(Q) in 80%. These results confirm the antimicrobial resistance impact in the Tunisian poultry sector and suggest the urgent need to establish a robust national antimicrobial resistance monitoring plan. Furthermore, the molecular detection of antibiotic resistance genes directly in biological samples seems to be a useful means for epidemiological investigations of the spread of resistance determinants.