Tn6198, a novel transposon containing the trimethoprim resistance gene dfrG embedded into a Tn916 element in Listeria monocytogenes

Bertsch, David; Uruty, Anaïs; Anderegg, Janine; Lacroix, Christophe; Perreten, Vincent; Meile, Léo

doi:10.1093/jac/dks531

Cited by 37 publications

(32 citation statements)

References 42 publications

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“…This gene encodes an anti-restriction protein that is probably not part of the typical MPF FA (68). The last gene of the operon, orf24 Tn916 , is often found in other MPF FA systems isolated from the rest of the operon (69), or even not mentioned as part of the conjugative machinery (70). It is thus probably not an essential component of MPF FA .…”

Section: Resultsmentioning

confidence: 99%

Key components of the eight classes of type IV secretion systems involved in bacterial conjugation or protein secretion

Guglielmini

Néron

Abby

et al. 2014

Nucleic Acids Research

189

216

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Conjugation of DNA through a type IV secretion system (T4SS) drives horizontal gene transfer. Yet little is known on the diversity of these nanomachines. We previously found that T4SS can be divided in eight classes based on the phylogeny of the only ubiquitous protein of T4SS (VirB4). Here, we use an ab initio approach to identify protein families systematically and specifically associated with VirB4 in each class. We built profiles for these proteins and used them to scan 2262 genomes for the presence of T4SS. Our analysis led to the identification of thousands of occurrences of 116 protein families for a total of 1623 T4SS. Importantly, we could identify almost always in our profiles the essential genes of well-studied T4SS. This allowed us to build a database with the largest number of T4SS described to date. Using profile–profile alignments, we reveal many new cases of homology between components of distant classes of T4SS. We mapped these similarities on the T4SS phylogenetic tree and thus obtained the patterns of acquisition and loss of these protein families in the history of T4SS. The identification of the key VirB4-associated proteins paves the way toward experimental analysis of poorly characterized T4SS classes.

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Section: Resultsmentioning

confidence: 99%

Key components of the eight classes of type IV secretion systems involved in bacterial conjugation or protein secretion

Guglielmini

Néron

Abby

et al. 2014

Nucleic Acids Research

189

216

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“…The overall G+C content of Tn 6188 (32.9%), being considerably lower than the overall G+C content of Listeria genomes, suggests a relatively recent transfer of Tn 6188 into L. monocytogenes . In line with this, to our knowledge, only few transposons have been identified in L. monocytogenes so far: Tn 5422 , which is found on the majority of Listeria plasmids, conferring tolerance to cadmium [44-46], the IS 1216 composite transposon harboring the bcrABC resistance cassette [20], Tn 6198 , a conjugative Tn 916 -like transposon conferring resistance to antibiotics [47], a Tn 554 -like transposon putatively involved in arsenic resistance [48], and an integrative conjugative element belonging to the Tn 916 family which has been found in the L. monocytogenes EGDe genome [49]. In contrast to Tn 6188 , Tn 5422 and Tn 6198 have a G+C content of 37.9%, which is much more similar to the overall G+C content of L. monocytogenes genomes.…”

Section: Resultsmentioning

confidence: 99%

Tn6188 - A Novel Transposon in Listeria monocytogenes Responsible for Tolerance to Benzalkonium Chloride

et al. 2013

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Controlling the food-borne pathogen Listeria (L.) monocytogenes is of great importance from a food safety perspective, and thus for human health. The consequences of failures in this regard have been exemplified by recent large listeriosis outbreaks in the USA and Europe. It is thus particularly notable that tolerance to quaternary ammonium compounds such as benzalkonium chloride (BC) has been observed in many L. monocytogenes strains. However, the molecular determinants and mechanisms of BC tolerance of L. monocytogenes are still largely unknown. Here we describe Tn6188, a novel transposon in L. monocytogenes conferring tolerance to BC. Tn6188 is related to Tn554 from Staphylococcus (S.) aureus and other Tn554-like transposons such as Tn558, Tn559 and Tn5406 found in various Firmicutes. Tn6188 comprises 5117 bp, is integrated chromosomally within the radC gene and consists of three transposase genes (tnpABC) as well as genes encoding a putative transcriptional regulator and QacH, a small multidrug resistance protein family (SMR) transporter putatively associated with export of BC that shows high amino acid identity to Smr/QacC from S. aureus and to EmrE from Escherichia coli. We screened 91 L. monocytogenes strains for the presence of Tn6188 by PCR and found Tn6188 in 10 of the analyzed strains. These isolates were from food and food processing environments and predominantly from serovar 1/2a. L. monocytogenes strains harboring Tn6188 had significantly higher BC minimum inhibitory concentrations (MICs) (28.5 ± 4.7 mg/l) than strains without Tn6188 (14 ± 3.2 mg/l). Using quantitative reverse transcriptase PCR we could show a significant increase in qacH expression in the presence of BC. QacH deletion mutants were generated in two L. monocytogenes strains and growth analysis revealed that ΔqacH strains had lower BC MICs than wildtype strains. In conclusion, our results provide evidence that Tn6188 is responsible for BC tolerance in various L. monocytogenes strains.

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“…Other parts of the Tn916 transposon bore genetic elements for bacterial conjugation. Although a circular form of the 3.3-kb sequence was detected in L. monocytogenes, the dfrG-containing fragment could not be transferred on its own to L. monocytogenes or to Enterococcus faecalis (30). Transfer of the dfrG gene was observed only when it was part of Tn916, which provided genetic elements that were required for conjugation.…”

Section: Discussionmentioning

confidence: 95%

“…The element was integrated into a sequence that was homologous to SPy_1769. Recently, Bertsch et al (30) identified an identical 3.3-kb sequence, which was a part of the transposon Tn916 in Listeria monocytogenes. Other parts of the Tn916 transposon bore genetic elements for bacterial conjugation.…”

Section: Discussionmentioning

confidence: 99%

Factors That Cause Trimethoprim Resistance in Streptococcus pyogenes

Bergmann

Linden

Chhatwal

et al. 2014

Antimicrob Agents Chemother

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bThe use of trimethoprim in treatment of Streptococcus pyogenes infections has long been discouraged because it has been widely believed that this pathogen is resistant to this antibiotic. To gain more insight into the extent and molecular basis of trimethoprim resistance in S. pyogenes, we tested isolates from India and Germany and sought the factors that conferred the resistance. Resistant isolates were identified in tests for trimethoprim or trimethoprim-sulfamethoxazole (SXT) susceptibility. Resistant isolates were screened for the known horizontally transferable trimethoprim-insensitive dihydrofolate reductase (dfr) genes dfrG, dfrF, dfrA, dfrD, and dfrK. The nucleotide sequence of the intrinsic dfr gene was determined for resistant isolates lacking the horizontally transferable genes. Based on tentative criteria, 69 out of 268 isolates (25.7%) from India were resistant to trimethoprim. Occurring in 42 of the 69 resistant isolates (60.9%), dfrF appeared more frequently than dfrG (23 isolates; 33.3%) in India. The dfrF gene was also present in a collection of SXT-resistant isolates from Germany, in which it was the only detected trimethoprim resistance factor. The dfrF gene caused resistance in 4 out of 5 trimethoprim-resistant isolates from the German collection. An amino acid substitution in the intrinsic dihydrofolate reductase known from trimethoprim-resistant Streptococcus pneumoniae conferred resistance to S. pyogenes isolates of emm type 102.2, which lacked other aforementioned dfr genes. Trimethoprim may be more useful in treatment of S. pyogenes infections than previously thought. However, the factors described herein may lead to the rapid development and spread of resistance of S. pyogenes to this antibiotic agent.

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Tn6198, a novel transposon containing the trimethoprim resistance gene dfrG embedded into a Tn916 element in Listeria monocytogenes

Cited by 37 publications

References 42 publications

Key components of the eight classes of type IV secretion systems involved in bacterial conjugation or protein secretion

Key components of the eight classes of type IV secretion systems involved in bacterial conjugation or protein secretion

Tn6188 - A Novel Transposon in Listeria monocytogenes Responsible for Tolerance to Benzalkonium Chloride

Factors That Cause Trimethoprim Resistance in Streptococcus pyogenes

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