Whole genome sequencing of Levilactobacillus brevis HQ1-1 for understanding the characteristics of Its antibiotic resistance genes

Abstract: Lactic acid bacteria (LAB) are the most commonly used microorganisms in fermented foods. Currently, in the context of antibiotic resistance (AR), the safe use of LAB has attracted more and more attention from researchers. Therefore, a strain of Levilactobacillus brevis HQ1-1 isolated from Chinese traditional fermented milk was used to investigate the association between genomic information and AR characteristics. The current study revealed that its complete genome contained a single circular chromosome of 2 376 708 bp with 7 plasmids, and harbored 2268 CDSs. Among the predicted CDSs, 1874 proteins of L. brevis HQ1-1 were functionally categorized, and divided into 25 groups using COG class description. There were 9 pairs of genes for the two-component regulatory system in the L. brevis HQ1-1 genome. It also contained 11 AR genes responsible for resistance to different antibiotics. Compared with 9 other L. brevis strains, strain HQ1-1 showed a different genome size, GC content, and protein coding regions. However, these strains all carried 11 AR genes. PCR and Kirby-Bauer (K-B) methods were also used to identify their AR genes and evaluate the antibiotic susceptibility. Strain HQ1-1 was not resistant to ampicillin, amoxicillin, rifampicin, erythromycin, and clarithromycin, but was resistant to norfloxacin, ciprofloxacin, fosfomycin, vancomycin and polymyxin B. In this study, it was emphasized that the AR of L. brevis HQ1-1 might bring safety hazards to human diet and health. Therefore, the safety concerns of microbial resistance should be considered when used in food.