Mosaic Tetracycline Resistance Genes and Their Flanking Regions in Bifidobacterium thermophilum and Lactobacillus johnsonii

Abstract

For the first time, mosaic tetracycline resistance genes were identified in Lactobacillus johnsonii and in Bifidobacterium thermophilum strains. The L. johnsonii strain investigated contains a complex hybrid gene, tet(O/W/32/O/W/O), whereas the five bifidobacterial strains possess two different mosaic tet genes: i.e., tet(W/ 32/O) and tet(O/W). As reported by others, the crossover points of the mosaic tet gene segments were found at similar positions within the genes, suggesting a hot spot for recombination. Analysis of the sequences flanking these genes revealed that the upstream part corresponds to the 5 end of the mosaic open reading frame. In contrast, the downstream region was shown to be more variable. Surprisingly, in one of the B. thermophilum strains a third tet determinant was identified, coding for the efflux pump Tet(L).

Chlortetracycline-Resistant Intestinal Bacteria in Organically Raised and Feral Swine

“…More recently, the genome of M. elsdenii strain 14-14, from an organic pig, was sequenced, and two genes, tet(40) and mosaic tet(OWO), were found in close proximity (T. B. Stanton and S. B. Humphrey, unpublished observations). Linkage between a mosaic tet gene and a nonmosaic tet gene has been noted for other intestinal bacteria (9,21). Based on the above findings, other isolates listed in Table 4 could have additional tet genes, either duplicated genes or genes not detected by PCR assays.…”

“…Eight organic and three feral swine isolates did not have detectable tet genes ( Table 4), suggesting that their resistance genes have minor sequence differences in regions targeted by the PCR primers (13) or represent a tet class not targeted in this study (5,10,21). Most CTC-resistant swine isolates (99/ 110) were positive in PCR assays for tet genes (Table 4).…”

“…Mosaic (interclass recombinant) tet(O)-tet(W) genes were present in M. elsdenii isolates but were not detected in other anaerobes from the same organic swine (Table 4). Mosaic tet genes have been detected in fecal DNAs and bacterial strains from humans and swine (14,21).…”

Characterization of a Streptococcus suis tet(O/W/32/O)-Carrying Element Transferable to Major Streptococcal Pathogens

“…At first thought to be confined to a small group of anaerobic bacteria (28), mosaic tet genes were then found to be abundant in human and animal fecal samples (26). Other mosaic tet genes were later detected in organisms of genera Clostridium (19,26), Bifidobacterium, and Lactobacillus (35).…”

A tet(S/M) hybrid from CTn6000 and CTn916 recombination

“…The mosaic tet genes described to date are hybrids of other ribosome protection type [tet(O), tet(32), tet(W)] which are particularly abundant among Firmicutes (Lactobacillus, Bifidobacterium, Streptococcus, Clostridium) isolated from animals (Stanton et al, 2005;Patterson et al, 2007;van Hoek et al, 2008;Palmieri et al, 2012). The origin and nomenclature of such genetically divergent mosaic tet genes remains controversial due to the lack of information about their genetic contexts and the identical size of the resulting proteins (Zheng et al, 2004, Stanton et al, 2005Palmieri et al, 2012).…”