Abstract
BackgroundAntibiotic resistance, is often conferred by the presence of antibiotic resistance genes. This study aimed to investigate the relationship between tetracycline resistance (Tet-R) and genotype in 31 Lactobacillus isolates from caries-active patients.MethodsThe tetracycline susceptibility of Lactobacillus isolates was determined using the agar spot test and the genetic characteristics associated with tetracycline resistance using whole-genome sequencing (WGS).ResultsThe minimum inhibitory concentration (MIC) values of most isolates were equal to or lower than the breakpoint MIC values. Four strains that were phenotypically more sensitive (L. fermentum B09, S23 and L. rhamonsus B17) or more resistant (L. plantarum B43) than other isolates to tetracycline were subjected to conduct whole-genome sequencing in order to detect the tetracycline resistance genes. The results revealed that the most common Tet-R genes in Lactobacillus strains were tetT, tetW, tetO and tetL. In addition, tetPB, tcr3 and otrA were detected for the first time. There were distinct Tet-R gene mutations in Lactobacillus isolates. Overall, the mean expression values of Tet-R-mutated genes in L. plantarum B43 were elevated, and the relative expression levels of tetT and tetW genes in L. rhamonsus B17 L. fermentum B09 and S23 were decreased relative to reference strains.ConclusionThe results of this study indicate that Lactobacillus isolates from saliva of caries-active patients do not present considerable tetracycline resistance reservoirs. However, genetic compounds associated with tetracycline resistance were identified by whole-genome sequencing, providing meaningful insights into tetracycline resistance mechanisms.
Highlights
Antibiotic resistance, is often conferred by the presence of antibiotic resistance genes
It is essential to check for signs of transferable antibiotic resistance in Lactobacilli strains that are important in oral cavity, and in strains that are used as probiotics
We explored the tetracycline susceptibility of isolated Lactobacillus clinical strains and identified the genetic characteristics associated with tetracycline resistance using whole-genome sequencing
Summary
Antibiotic resistance, is often conferred by the presence of antibiotic resistance genes. Antibiotic resistance has become a major global public health problem [1] It is often conferred by the presence of antibiotic resistance genes, which may spread rapidly through horizontal gene transfer via plasmids and other genetic elements, and can result the environmental contamination with antibiotic resistance strains [2]. Lactobacilli are members of the lactic acid bacteria community, which can adapt to a wide variety of ecological niches (e.g., food, oral cavity, gastro-intestinal tract, and vagina) [14]. As members of oral microbial communities, the Lactobacillus strains have the opportunity to exchange resistance factors with other microorganisms [21], potentially transferring these genes to other pathogenic bacteria. It is essential to check for signs of transferable antibiotic resistance in Lactobacilli strains that are important in oral cavity, and in strains that are used as probiotics
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