High-frequency transfer of a naturally occurring chromosomal tetracycline resistance element in the ruminal anaerobe Butyrivibrio fibrisolvens

Abstract

Butyrivibrio fibrisolvens strains resistant to tetracycline were isolated from the bovine rumen. Two of three Tc r B. fibrisolvens tested were able to donate tetracycline resistance at frequencies ranging from 10 ؊7 to 10 ؊1 per donor cell in anaerobic filter matings to a rifampin-resistant mutant of the type strain of B. fibrisolvens, 2221 R. The recipient strain 2221 R exhibited rapid autoaggregation, which might be a factor in the high transfer rates observed. Tc r transconjugants of B. fibrisolvens 2221 R were also capable of further transferring tetracycline resistance to a fusidic acid-resistant mutant, 2221 F. Comparison of genomic DNAs by pulsed-field gel electrophoresis demonstrated altered band profiles in transconjugants, consistent with the acquisition of a large mobile chromosomal element. The transferable elements from the two B. fibrisolvens donors 1.23 and 1.230 (TnB123 and TnB1230, respectively) showed the same preferred insertion site in the B. fibrisolvens 2221 R chromosome and are likely to be similar, or identical, elements. Hybridization experiments showed no close relationship between TnB1230 and int-xis regions from Tn916 or Tn5253. Although DNA from the B. fibrisolvens donor strains hybridized with probes carrying tet(M) or tet(O) sequences, transconjugants were found to have acquired a distinct band that hybridized only weakly with these probes, suggesting that a second, distantly related Tc r determinant had been transferred.

Evidence for recent intergeneric transfer of a new tetracycline resistance gene, tet(W), isolated from Butyrivibrio fibrisolvens, and the occurrence of tet(O) in ruminal bacteria

“…2). This is consistent with the presence of more than one copy of the transferred gene in transconjugants resulting from multiple insertion events or internal transpositions after the initial insertion, as postulated previously (Scott et al, 1997). Surprisingly, neither the largest band of 390 kb nor a 145 kb band obtained with some transconjugants (e.g.…”

“…The fact that tet (W) has not been reported previously might be taken to indicate that it is not common in clinical or veterinary pathogens. On the other hand, the contribution of tet (W) to tetracycline resistance could have been overlooked, particularly if it is often present as one of two Tc R determinants, as in the original B. fibrisolvens strains studied here (Scott et al, 1997). Furthermore, there are reports of Tc R bacteria from cattle, pigs, cats and dogs that fail to hybridize to the DNA sequences of known Tc R genes (Brown and Roberts, 1991;Schwarz and Noble, 1994;Chaslus-Dancla et al, 1995;Sachdé et al, 1997).…”

“…The tet (W) gene could provide a much needed selectable marker for developing genetic systems in ruminal anaerobes, particularly in Selenomonas ruminantium in which there has been limited success so far in introducing vector constructs based on indigenous or heterologous plasmids (Attwood and Brooker, 1992). The new transposable elements may find application in transposon mutagenesis, although the B. fibrisolvens element has a preferred insertion site within the genome (Scott et al, 1997). The demonstration of widespread genetic exchange within the rumen community also has important implications for the design of safe, stable recombinant organisms that might be added as inoculants or probiotics to animal feed or to the rumen, or that might be used in crop production and then ingested by the grazing animal.…”

“…A hybridizing band of 3 kb was detected under high-stringency conditions with the donor B. fibrisolvens strains 1.230, 1.23 and with Tc R transconjugants (Fig. 5), but no hybridization was found to the Tc S recipient 2221 R or to the Tc R strain 1.210, which does not transfer tetracycline resistance (Scott et al, 1997). Chromosomal DNA from two Australian ᮊ 1999 Blackwell Science Ltd, Environmental Microbiology, 1, 53-64 3.…”

Antibiotic‐resistance profile in environmental bacteria isolated from penicillin production wastewater treatment plant and the receiving river

“…(Huddleston et al, 2006) and Campylobacter (Wittwer et al, 2005). It should be noted that the majority of resistant bacteria in environments are indigenous species, which constitute a reservoir that could contribute to the maintenance and spread of antibiotic-resistance genes to human pathogens through horizontal gene transfer facilitated by mobile genetic elements such as plasmids, transposons and integrons (Kruse and Sørum, 1994;Scott et al, 1997;Adams et al, 1998;Hamelin et al, 2007), especially in wastewater treatment plant (WWTP) environments (Szczepanowski et al, 2004;Schlüter et al, 2007). The elucidation of antibiotic resistance characteristics of the whole bacterial community is in need to assess bacterial resistance comprehensively.…”