Arbekacin Sulfate

Salmonella enterica serovar Mbandaka, a prevalent foodborne pathogen, poses a threat to public health but remains poorly understood. We have determined the phylogenomic tree, genetic diversity, virulence, and antimicrobial resistance (AMR) profiles on a large genomic scale to elucidate the evolutionary dynamics within the Mbandaka pan-genome. The polyphyletic nature of this serovar is characterized by two distinct phylogenetic groups and inter-serovar recombination boundaries, that potentially arising from recombination events at the H2-antigen loci. The open pan-genome exhibited a flexible gene repertoire, with numerous cloud gene families involved in virulence and AMR. Extensive gene gain and loss observed at the terminal nodes of the phylogenetic tree indicate that Mbandaka individuals have undergone frequent gene turnover. The resulting changes in virulence and AMR genes potentially pose emerging threats to public health. We explored serovar conversion due to recombination of H-antigen loci, inter-serovar divergences in gene gain and loss, prophage-mediated acquisition of virulence factors, and the role of incompatibility group plasmids in acquiring resistance determinants as key molecular mechanisms driving the pathogenicity and antibiotic resistance of Mbandaka. Our work contributes to a comprehensive understanding of the complex mechanisms of pathogenesis and the ongoing evolutionary arms race with current therapeutic approaches in serovar Mbandaka.

Staphylococcus argenteus, a newly described species of coagulase-positive Staphylococcus, was first identified in clinical isolates in northern Japan in 2019. The aim of the present study was to clarify the trends in the epidemiological features and antimicrobial resistance traits of S. argenteus in the recent years.

S. argenteus isolates from various clinical specimens were screened using MALDI-TOF and genotyped using the multilocus sequence typing scheme. Antimicrobial susceptibility was determined using broth microdilution test and resistance genes were detected by multiplex/uniplex PCR. Nucleotide sequences of haemolysin genes (hla, hlb, hld, and hlg) were determined and analysed in some isolates.

From August 2020 to December 2023, 210 isolates were identified as S. argenteus. The ratio of S. argenteus to Staphylococcus aureus clinical isolates was 0.0045, showing a slightly decreasing trend compared to what was previously reported (2019.8-2020.7). Three genotypes, ST1223-coa-XV, ST2198-coa-XIV, and ST2250-coa-XId were identified, with ST2250 being dominant (49%) and exhibiting an increasing trend. S. argenteus isolates were almost susceptible to antimicrobials examined, while ST2198 isolates showed higher resistance rates to ampicillin, macrolides, and aminoglycosides than other clones, harbouring blaZ, msrA, and aac(6')-Ie-aph(2″)-Ia. Only eight isolates (4-ST2250, 3-ST1223, and 1-ST2198) did not show haemolysis on blood agar plates. These isolates had intact haemolysin genes and promoter regions; however, a novel deletion mutation in hlg-component A was detected in some haemolytic and non-haemolytic isolates.

The present study revealed the epidemiological trend of S. argenteus clones in northern Japan, along with the occurrence of non-haemolytic isolates with intact haemolysin genes.