Prevalence, diversity and transferability of the Tn916-Tn1545 family ICE in oral streptococci

Abstract

Background: The Tn916-Tn1545 family of Integrative Conjugative Elements (ICE) are mobile genetic elements (MGEs) that play a role in the spread of antibiotic resistance genes. The Tn916 harbors the tetracycline resistance gene tet(M) and it has been reported in various bacterial species. The increase in the levels of tetracycline resistance among oral streptococci is of great concern primarily due to the abundance of these species in the oral cavity and their ability to act as reservoirs for antibiotic resistance genes. Methods: In the current study, we screened 100 Norwegian clinical oral streptococcal isolates for the presence and diversity of the Tn916-Tn1545 family. In addition, we investigated the transferability the elements, and the associated transfer frequencies. Results: We observed that 21 isolates harboured the Tn916-Tn1545 family and that two of these elements were the novel Tn6815 and Tn6816. The most prevalent member of the Tn916-Tn1545 family observed in the Norwegian clinical oral streptococcal isolates was the wild type Tn916. Conclusion: The detection of other members of this family of ICE and varying transfer frequencies suggests high versatility of the Tn916 element in oral streptococci in Norway.

Prevalence of antibiotic resistance genes in the oral cavity and mobile genetic elements that disseminate antimicrobial resistance: A systematic review

“…Other conjugative transposons that can disseminate resistance are CTn 60002 (part of the Tn 916 family) that transfers doxycycline resistance (Warburton et al., 2013) and Tn 4555 , which harbours cfxA , a beta‐lactam resistance gene (Fernandez‐Canigia et al., 2015). Recently one study (Lunde et al., 2021) investigated the presence of Tn 916 ‐like elements in the oral cavity of 100 clinical oral samples from Norway. They found that 24% of oral streptococci contained tet (M) and that this gene was contained on integrative conjugative elements of the Tn 916 family.…”

Characterization and Fitness Cost of Tn7100, a Novel Integrative and Conjugative Element Conferring Multidrug Resistance in Haemophilus influenzae

“…This strain carries a transposon with a tentative 5-or 6-bp coupling sequence (GTCTA/GTCTAA) identical to the sequence starting one nucleotide downstream from Tn7471 on Tn7100, suggesting that Tn7471 may originate from oral streptococci. This hypothesis is supported by a recent investigation of Tn916-like elements in oral streptococci in Norway, which revealed that strains possessing the transposition machinery of Tn916 (xis-Tn and int-Tn) in the absence of tet(M) are frequent (Lunde et al, 2021).…”

TnSmu1 is a functional integrative and conjugative element in Streptococcus mutans that when expressed causes growth arrest of host bacteria

“…Horizontal gene transfer (HGT) is a driving force in microbial evolution, allowing bacteria to acquire new traits and phenotypes from other bacterial lineages. Biofilms, including dental plaque, are hot spots for HGT, and HGT is well documented in the oral microbiome (Jones et al, 2021;Lunde et al, 2021;Olsen et al, 2013;Roberts et al, 1999Roberts et al, , 2001. Further, oral bacteria can cause major health issues.…”

“…Further, oral bacteria can cause major health issues. For example, Streptococcus mutans, a major causative agent of dental caries, acts as a reservoir for antibiotic resistance genes and mobile genetic elements within the oral microbiome and can be a causative agent of infective endocarditis (Lunde et al, 2021;Nomura et al;Olsen et al, 2013).…”

“…Integrative and conjugative elements (ICEs) represent the most prevalent type of conjugative element and are found in all major clades of bacteria, including oral and cavity-causing bacteria (Guglielmini et al, 2011; Lunde et al, 2021; Roberts and Mullany, 2009, 2011; Roberts et al, 2001). Integrative and conjugative elements mediate their own transfer from a host cell to a recipient and often contain cargo genes that confer beneficial phenotypes to the host cells.…”