Research Note: Detection of antibiotic-resistance genes in commercial poultry and turkey flocks from Italy

Abstract

Antibiotics are routinely used in commercial poultry farms for the treatment of economically important bacterial diseases. Repeated use of antibiotics, usually administered in the feed or drinking water, may also result in the selection of resistant bacteria in animal feces, able to transfer their antimicrobial-resistance genes ( ARG ), residing on mobile elements, to other microorganisms, including human pathogens. In this study, single and multiplex PCR protocols were performed to detect tetracycline-, lincomycin-, chloramphenicol-, aminoglycoside-, colistin-, vancomycin-, and carbapenem-resistance genes, starting from 38 litter samples collected from 6 poultry and 2 turkey Italian flocks. The ARG were confirmed for all investigated classes of antimicrobials, except for colistin ( mcr-1, mcr-2, mcr-3,mcr-4 mcr-5 ) and carbapenem ( IMP, OXA-48, NDM , KPC ), while the vanB gene was only detected for vancomycin. The highest positivity was obtained for tetracycline ( tet[L], tet[M] , tet[K], tetA[P] ] and aminoglycoside ( aadA2 ) ARG, confirming the predominant use of these antimicrobials in the veterinary practice and their potential to enhance the resistance patterns also in humans as a consequence of environmental contamination. On the contrary, the dissemination by poultry of ARG for critically important antimicrobials seems to be of minor concern, suggesting a negligible environmental dissemination by these genes in the Italian poultry industry. Finally, the molecular screening performed in this study using a noninvasive sampling method represents a simple and rapid tool for monitoring the ARG patterns at the farm level.

Pilot Study on Poultry Meat from Antibiotic Free and Conventional Farms: Can Metagenomics Detect Any Difference?

“…Genes coding for resistance to vancomycin were identified among the ARGs with normalized mean values of abundance >1000 in at least one tested group. In accordance with other authors [40,52], vancomycin resistance genes can be identified in poultry flocks, although avoparcin has been banned by the EU since 1997. The relative abundance we estimated for the vancomycin resistance genes constitutes a body of evidence of their persistence, while Savin et al [40] reported a declining trend.…”

Antibiotic Resistance Genes Occurrence in Conventional and Antibiotic-Free Poultry Farming, Italy

“…Concerning the other resistance genes, the aad A2 gene, specific for aminoglycosides, was the most representative gene in samples from all the investigated farms, confirming a previous study carried out on the same geographical area [ 11 ] and in accordance with the aminoglycoside resistance profiles described in bacterial isolates coming from poultry farms in Italy [ 35 ].…”

“…A similar survey has already been performed in central Italy, involving only conventional broiler and turkey flocks, while a more extensive study was conducted in a high-density farming area of northern Italy, focusing on the microbial community and ARGs abundance in different types of conventional livestock manure (dairy cattle, poultry, and swine) [ 11 , 12 ]. More recently, a single antibiotic-free broiler farm, located in northern Italy, was investigated to quantify some representative ARGs at different sampling sites [ 15 ].…”

“…Total DNA was recovered from each sample by means of the Maxwell ® 11 Instrument (Promega, Italy) using the related Maxwell kit ® 11 Tissue DNA Purification (Promega, Italy), allowing us to obtain 100 μL of high-quality DNA useful for the PCR testing. Previously published primers, targeting specific ARGs fragments, were selected in order to perform single or multiplex end-point PCR protocols, as already described [ 11 ]. In particular, ARGs commonly used as antibiotics in poultry farming for therapeutic purposes ( tet A, tet B, tet C, tet K, tet L, tet M, tet B(P), tet A(P) for tetracyclines, lnu A, lnu B for lincomycin, and aad A2, aad B, aac (3)IV for aminoglycosides) [ 16 ], along with some highly/critically important antimicrobials for human medicine ( cat A1 for chloramphenicol, mcr -1 to mcr -5 for colistin, van A, van B, van C1, van C2, van D, van M, van N for vancomycin, and IMP , OXA-48 , NDM , KPC for carbapenems) [ 17 ], were investigated.…”

“…More recently, a culture-independent approach has been applied to investigate the ARGs distribution in chicken intestinal microbiota, performing PCR-based or metagenomic sequence analysis [ 11 , 12 , 13 ]. These alternative methods appear to be particularly useful to study the microbial community and its genetic profiles in different types of samples, such as animal manure or agricultural soils, providing more extensive information on the resistance patterns harbored by all bacteria from investigated samples and not only in selected colonies [ 11 , 12 ].…”