Widespread Distribution of a Tet W Determinant among Tetracycline-Resistant Isolates of the Animal PathogenArcanobacterium pyogenes

Abstract

Tetracycline resistance is common among isolates of the animal commensal and opportunistic pathogen Arcanobacterium pyogenes. The tetracycline resistance determinant cloned from two bovine isolates of A. pyogenes was highly similar at the DNA level (92% identity) to the tet(W) gene, encoding a ribosomal protection tetracycline resistance protein, from the rumen bacterium Butyrivibrio fibrisolvens. The tet(W) gene was found in all 20 tetracycline-resistant isolates tested, indicating that it is a widely distributed determinant of tetracycline resistance in this organism. In 25% of tetracycline-resistant isolates, the tet(W) gene was associated with a mob gene, encoding a functional mobilization protein, and an origin of transfer, suggesting that the determinant may be transferable to other bacteria. In fact, low-frequency transfer of tet(W) was detected from mob ؉ A. pyogenes isolates to a tetracycline-sensitive A. pyogenes recipient. The mobile nature of this determinant and the presence of A. pyogenes in the gastrointestinal tract of cattle and pigs suggest that A. pyogenes may have inherited this determinant within the gastrointestinal tracts of these animals.Resistance to tetracycline is the most common bacterial antibiotic resistance found in nature and similarly is the most prominent type of resistance among bacteria isolated from animals (10). Tetracycline binds to the 30S ribosomal subunit and inhibits protein synthesis (32), and resistance to this drug is most commonly mediated either by active efflux of tetracycline from the cell or by ribosomal protection from the action of tetracycline (10). In rare cases, tetracycline resistance is mediated through direct inactivation of the antibiotic (30) or by mutations in the 16S rRNA that prevent binding of tetracycline to the ribosome (26).Arcanobacterium pyogenes is a common inhabitant of the respiratory and urogenital tracts of domestic animals, including cattle and swine (8). It has also been isolated from the rumen of feedlot cattle (22) and more recently from the gastric mucosa of pigs (B. H. Jost, K. W. Post, J. G. Songer, and S. J. Billington, unpublished data), suggesting that A. pyogenes may also be a common inhabitant of the gastrointestinal tract of these species. Under conditions of physical trauma or previous microbial infection, A. pyogenes can disseminate to cause a variety of suppurative infections, such as liver abscesses and mastitis in cattle (15,18,21) and suppurative pneumonia and polyarthritis in pigs (14,35). Virulence, at least in an intraperitoneal mouse model, appears to be mediated through a poreforming toxin, pyolysin (6, 16). The development of antibiotic resistance in normal flora secondary pathogens, such as A. pyogenes, is of particular significance, not only because of the ability of resistant A. pyogenes to avoid antibiotic therapy, but also because of the potential for transfer of resistance to other pathogens.Resistance to the tetracycline antibiotics among A. pyogenes isolates is widespread. A French study indicated that 67%...

Presence of tetracycline resistant bacteria and genes in grassland-based animal production systems

“…These phenomena were not observed in our results. Instead, all of the nucleotide sequences identified in the environment exactly match the resistance gene sequences reported in the literature (Aminov et al, 2001;Billington et al, 2002;Flórez et al;Koike et al, 2007Spigaglia et al, 2008). This finding and the fact that the most common genes detected in animal samples (tet(W), tet(M) and tet(Q)) were also the most common genes detected in environmental samples suggests that on these farms, resistance is flowing from animals to the environment.…”

Prevalence of Tetracycline Resistance Genes in Oral Bacteria

“…(Table 4). This gene was originally identified from the bovine rumen anaerobe Butyrivibrio fibrisolvens and subsequently in human fecal anaerobes, pigs, and recently, a facultative anaerobe, Arcanobacterium pyogenes (3,5,33). In B. fibrisolvens, tet(W) is contained within a large conjugative transposon, TnB1230 (3), which is capable of high-frequency conjugative transfer among B. fibrisolvens species.…”

Isolation of Tetracycline-Resistant Megasphaera elsdenii Strains with Novel Mosaic Gene Combinations of tet (O) and tet (W) from Swine

“…Although hybrid tet(O)-tet(W) genes have not been reported, tet(W) genes are present in diverse genera from gastrointestinal environments, e.g., Butyrivibrio fibrisolvens, Selenomonas ruminantium, Mitsuokella multiacidus, Fusobacterium prausnitzii, Bifidobacterium longum, Clostridium-like strain K-10, and Arcanobacterium pyogenes (8,9,37,54). The tet(O) gene is present in various gram-negative and gram-positive bacteria, notably gram-positive cocci (13,60), and in intestinal bacteria such as Campylobacter spp.…”

“…The tet classes are defined by amino acid sequence similarity of the proteins they encode (33). Classes of tet genes are identified by DNA-DNA hybridization, PCR assays, or both (5,6,8,9,12,29,44,48,49,54).…”