Characterization of the Tn 916 Conjugative Transposon in a Food-Borne Strain of Lactobacillus paracasei

Abstract

Food-borne antibiotic-resistant lactic acid bacteria have received growing attention in the past few years. We have recently identified tetracycline-resistant Lactobacillus paracasei in samples of milk and natural whey starter cultures employed in the manufacturing process of a typical Italian fermented dairy product, Mozzarella di Bufala Campana. In the present study, we have characterized at the molecular level the genetic context of tetracycline resistance determinants in these natural strains, which we have identified as tet(M). This gene was present in 21 independent isolates, whose fingerprinting profiles were distributed into eight different repetitive extragenic palindromic groups by cluster analysis. We provide evidence that the gene is associated with the broad-host, conjugative transposon Tn916, which had never before been described to occur in L. paracasei. PCR analysis of four independent isolates by use of specifically designed primer pairs detected the presence of a circular intermediate form of the transposon, carrying a coupling sequence (GGCAAA) located between the two termini of Tn916. This novel coupling sequence conferred low conjugation frequency in mating experiments with the recipient strain JH2-2 of Enterococcus faecalis.

Probiotic attributes of indigenous Lactobacillus spp. isolated from traditional fermented foods and beverages of north-western Himalayas using in vitro screening and principal component analysis

“…Hence, this property makes Lactobacillus spp. abundant in the final phases of many food fermentations (Devirgiliis et al 2009). This might be the main reason that most of the Lactobacillus isolates from traditional fermented foods of North-western Himalayas were of Lactobacillus spp.…”

Update on antibiotic resistance in foodborne Lactobacillus and Lactococcus species

“…Transposon-mediated inter-species genetic transfer was recently described as the most frequent mechanisms contributing to AR spread in bacteria (Wozniak and Waldor, 2010). A variety of AR determinants associated with the Tn 916 - 1545 family of transposons have been described in foodborne bacteria (Hummel et al, 2007; Devirgiliis et al, 2009; Rizzotti et al, 2009). The best characterized member of this family is Tn 916 , an 18 kb conjugative transposon carrying the tet (M) gene and displaying broad host range toward both Gram-positive and Gram-negative bacteria (Clewell et al, 1995).…”

“…Each of these antimicrobials belongs to a specific pharmacological class, and the overall information from these studies covers most of the known mechanisms of action of antibiotics (i.e., protein synthesis and cell wall assembly). Most studies were conducted employing culture-dependent phenotypic assays, followed by PCR-based detection of AR genes, while in few cases additional methodologies were used including Southern blotting, microarray assays and real time PCR (Ammor et al, 2008a,b; Devirgiliis et al, 2009; Egervarn et al, 2009). Altogether, the results from these recent studies confirm the prevalence of tetracycline and erythromycin resistance genes in lactobacilli, with tet (M) and erm (B) representing the most widespread resistance determinants (Table 2 and references therein).…”

Safety Evaluation Of Sjenica Cheese With Regard To Coagulase-Positive Staphylococci And Antibiotic Resistance Of Lactic Acid Bacteria And Staphylococci

“…The general observation pointed out that the presence of tet(M) has not been as frequently associated with lactococci as to other LAB such as E. faecalis and Lactobacillus spp. [74][75][76]. The transmissible nature of tet(M) and tet(K) genes originated from food-borne lactobacilli were confi rmed as it has been shown their association to host a Tn916 transposon [76] and a plasmid [73] respectively.…”