Contribution of Enterococci to the Spread of Antibiotic Resistance in the Production Chain of Swine Meat Commodities

Abstract

Thirty-six samples, including fecal specimens, dry feedstuffs, raw and processed pork meat products, and dry fermented sausages, were collected from two production chains of swine meat commodities and analyzed for the presence of 11 antibiotic resistance (AR) genes. Specific PCR assays carried out on DNA extracted directly from the samples revealed a high incidence of the genes tet(K) (80.5%), ermB (66.7%), and tet(M) (66.7%). Feces and feedstuffs gave the largest number of positive amplifications. To elucidate the contribution of enterococci to the occurrence and spread of AR, 146 resistant enterococci were isolated, and their identity, genetic fingerprints, and AR gene profiles were determined by means of molecular techniques. Enterococcus faecalis and Enterococcus faecium were the predominant isolated species (43.8 and 38.4%, respectively); Other Enterococcus species identified were E. durans (8.9%), E. hirae (2.7%), E. gallinarum (2.1%), E. mundtii (2.1%), and E. casseliflavus (2.1%). A number of isolates displayed a complex AR gene profile comprising up to four different resistance determinants. The genes tet(M) and ermB were highly diffused, being present in 86.9 and 84.9%, respectively, of the isolates. The application of amplified fragment length polymorphism fingerprinting was particularly valuable to monitor the resistant enterococcal isolates along the production chain and to individuate steps in which contamination might occur. In fact, isolates of E. faecalis and E. faecium showing the same amplified fragment length polymorphism profile and AR gene pattern were detected in samples taken at different steps of the food chain suggesting three cases of bacterial clonal spread.

Characterization of Tetracycline-Resistant Streptococcus thermophilus Isolates from Italian Soft Cheeses

“…The identities of tetracycline-resistant S. thermophilus isolates were confirmed by species-specific PCR analysis, using the method described by Lick et al (12) modified with an annealing step of 56°C for 30 s in order to avoid amplification of related lactic acid bacteria, such as lactococci. For some isolates, showing a faint 968-bp band (results not shown) with the procedure described above, identification was further corroborated by sequencing a 16S rRNA gene fragment, as previously reported (19).…”

“…To obtain information about the nucleotide sequences of the tetracycline resistance genes found in our isolates, fragments of tet(S), tet(M), and tet(L) from representative strains were sequenced as previously described (19). The online BLASTN program was used for sequence similarity searches.…”

Erythromycin- and tetracycline-resistant lactobacilli in Italian fermented dry sausages

“…Most investigations in this regard have focused on pathogenic bacteria (Gevers et al 2003a;Rizzotti et al 2005), and data on AR in lactobacilli are relatively limited (Jacobsen et al 2007). However, the number of studies on LAB has recently increased because of growing interest in probiotic bacteria and genetic modification of LAB for various purposes (Ouoba et al 2008).…”

Modeling the Aminogenic Potential of Enterococcus faecalis EF37 in Dry Fermented Sausages through Chemical and Molecular Approaches

“…However, their occurrence in foods is highly controversial since enterococci have been described as spoilage microorganisms and also as indicators of fecal contamination (10). Moreover, food-borne enterococci are known to harbor resistances to different antibiotics (25), and they are recognized as powerful tyrosine-decarboxylating microorganisms (6,20,21). The tyrosine decarboxylase enzyme of enterococci has recently been demonstrated to also decarboxylate phenylalanine, although to a lower extent than tyrosine (22).…”