Abstract
ABSTRACTBackground: Tn916 and Tn1545 are paradigms of a large family of related, broad host range, conjugative transposons that are widely distributed in bacteria and contribute to the spread of antibiotic resistance genes (ARGs). Variation in the copy number (CN) of Tn916-Tn1545 elements and the circularization ratio (CR) may play an important role in propagation of ARGs carried by these elements.Objectives and Design: In this study, the CN and CR of Tn916-Tn1545 elements in oral streptococci were determined using droplet digital PCR (ddPCR). In addition, we investigated the influence of tetracycline on the CR of Tn916-Tn1545 elements.Results: The ddPCR assay designed in this study is a reliable way to rapidly determine CN and CR of Tn916-Tn1545 elements.Conclusions: Our data also suggest that Tn916-Tn1545 elements are generally stable without selective pressure in the clinical oral Streptococcus strains investigated in this study.
Highlights
The oral cavity is among the most microbiologically diverse environments in the human body and has been shown to contain over 1100 different bacterial species [1] of which Streptococcus species are the most abundant [2]
The 10 oral Streptococcus species. included in this study were identified by MALDI-TOF as follows: S. mitis (n = 2), S. sanguinis (n = 2), S. oralis (n = 5), and S. gordonii (n = 1)
Advances in molecular biological techniques and detection methods of resistance genes, have increased our knowledge of factors contributing to the propagation of mobile genetic elements (MGEs) carrying resistance genes in bacterial populations
Summary
The oral cavity is among the most microbiologically diverse environments in the human body and has been shown to contain over 1100 different bacterial species [1] of which Streptococcus species are the most abundant [2]. There has been an increase in the number of antibiotic-resistant streptococcal strains over the last few decades [4], and recent studies suggest that the oral cavity functions as a reservoir for transferable antibiotic resistance genes [5,6,7,8] including genes encoding resistance to macrolides [9], beta-lactams, and tetracyclines [10]. One of the most common tetracycline resistance genes within oral isolates and metagenomes is tet(M) [8,11]. The broad distribution of tet(M) has frequently been linked to its association with mobile genetic elements (MGE) from the Tn916-Tn1545 family of conjugative transposons/ Integrative Conjugative Elements [ICEs] [12,13,14,15,16]. Tn916 and Tn1545 are paradigms of a large family of related, broad host range, conjugative transposons that are widely distributed in bacteria and contribute to the spread of antibiotic resistance genes (ARGs). We investigated the influence of tetracycline on the CR of Tn916-Tn1545 elements
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