Antimicrobial resistance in foodborne <i>Salmonella enterica</i> isolates in the Republic of Belarus

Introduction. Antimicrobial resistance is a global public health concern. Salmonella spp., which can be transmitted to humans through contaminated food, are among the most important foodborne pathogens worldwide. Materials and methods. The antimicrobial resistance of 358 bacterial isolates collected from food and water in the Republic of Belarus (Belarus) in 20182021 was studied by analyzing phenotypic and genotypic characteristics of antibiotic bacterial resistance. MALDI-TOF mass spectrometry was used to classify and identify bacteria. Phenotypic antimicrobial susceptibility of bacteria was measured by the minimum inhibitory concentration method using a Sensititre automated bacteriological analyzer and the disk diffusion test for 45 antimicrobial agents. Antimicrobial resistance genes in multidrug-resistant Salmonella isolates were identified by whole-genome sequencing. Results. The in vitro testing of phenotypic bacterial susceptibility showed high susceptibility to fluoroquinolones (97.2%), third-generation cephalosporins (93.9%), carbapenems (98.0%), ampicillin (81.8%), aminoglycosides (97.5%), tetracyclines (87.5%), chloramphenicol (93.8%), trimethoprim/sulfamethoxazole (co-trimoxazole) (95.3%) and colistin (85.2%). It was found that the antibiotic resistance mechanism in S. enterica was associated with the presence of genes blaTEM-1B (82%), blaTEM-1C (7.7%), blaSHV-12 (2.6%), blaDHA-1 (2.6%), blaCMY-2 (7.7%), qnrB2 (9.1%), qnrB4 (9.1%), qnrB5 (9.1%), qnrB19 (72.7%), aac(6)-Ib-cr (9.1%), aac(6)-Iaa (100%), aadA1 (13.2%), aadA2 (8.8%), tetB (74.3%), tetA (25.7%), tetM (2.9%), tetD (28.6%), mcr-9 (1.5%). Conclusion. All the bacterial isolates were phenotypically susceptible to first-line antibiotics used in treatment of salmonellosis: fluoroquinolones and third-generation cephalosporins. The whole-genome sequencing of multidrug-resistant Salmonella isolates (19.0%) detected resistance genes for 9 groups of antibiotics: aminoglycosides (100%), beta-lactams (57.4%), fluoroquinolones (16.2%), tetracyclines (51.5%), macrolides (1.5%), phenicols (30.4%), trimethoprim (13.0%), sulfonamides (47.8%) and colistin (1.4%). Thus, epidemiological surveillance of the Salmonella spread through the food chain is of critical importance for the monitoring of antimicrobial resistance among foodborne Salmonella

A Mutation in the <i>MYBL2-1</i> Gene Is Associated with Purple Pigmentation in <i>Brassica oleracea</i>

Anthocyanins are well-known antioxidants that are beneficial for plants and consumers. Dihydroflavonol-4-reductase (DFR) is a key gene of anthocyanin biosynthesis, controlled by multiple transcription factors. Its expression can be enhanced by mutations in the negative regulator of anthocyanin biosynthesis myeloblastosis family transcription factor-like 2 (MYBL2). The expression profiles of the DFR gene were examined in 43 purple and green varieties of Brassica oleracea L., Brassica napus L., Brassica juncea L., and Brassica rapa L. MYBL2 gene expression was significantly reduced in purple varieties of B. oleracea, and green varieties of B. juncea. The MYBL2 gene sequences were screened for mutations that can affect pigmentation. Expression of the DFR gene was cultivar-specific, but in general it correlated with anthocyanin content and was higher in purple plants. Two single nucleotide polymorphysms (SNPs) were found at the beginning of the DNA-binding domain of MYBL2 gene in all purple varieties of B. oleracea. This mutation, leading to an amino acid substitution and the formation of a mononucleotide repeat (A)8, significantly affects RNA structure. No other noteworthy mutations were found in the MYBL2 gene in green varieties of B. oleracea and other studied species. These results bring new insights into the regulation of anthocyanin biosynthesis in genus Brassica and provide opportunities for generation of new purple varieties with precise mutations introduced via genetic engineering and CRISPR/Cas

Correlation of Acinetobacter baumannii K144 and K86 capsular polysaccharide structures with genes at the K locus reveals the involvement of a novel multifunctional rhamnosyltransferase for structural synthesis

Whole genome sequence from Acinetobacter baumannii isolate Ab-46-1632 reveals a novel KL144 capsular polysaccharide (CPS) biosynthesis gene cluster, which carries genes for D-glucuronic acid (D-GlcA) and L-rhamnose (L-Rha) synthesis. The CPS was extracted from Ab-46-1632 and studied by 1H and 13C NMR spectroscopy, including a two-dimensional 1H,13C HMBC experiment and Smith degradation. The CPS was found to have a hexasaccharide repeat unit composed of four L-Rhap residues and one residue each of D-GlcpA and N-acetyl-D-glucosamine (D-GlcpNAc) consistent with sugar synthesis genes present in KL144. The K144 CPS structure was established and found to be related to those of A. baumannii K55, K74, K85, and K86. A comparison of the corresponding gene clusters to KL144 revealed a number of shared glycosyltransferase genes correlating to shared glycosidic linkages in the structures. One from the enzymes, encoded by only KL144 and KL86, is proposed to be a novel multifunctional rhamnosyltransfaerase likely responsible for synthesis of a shared α-L-Rhap-(1 → 2)-α-L-Rhap-(1 → 3)-L-Rhap trisaccharide fragment in the K144 and K86 structures.</p