Nihon saikingaku zasshi. Japanese journal of bacteriology最新文献

In the concept of central dogma (RNA is transcribed from DNA to produce proteins), RNA was thought to be merely an intermediary for genetic information to synthesize proteins from DNA. Since the discovery of RNA interference in 2000, research on RNA has progressed remarkably, especially in mammals. On the other hand, the role of RNA in bacterial infections was largely unknown. At that time, we started research on RNA and bacterial infection and revealed that miR-210, a small RNA in the gastric epithelial cells, is involved in gastric diseases caused by Helicobacter pylori in-fection. Furthermore, we have successfully developed sequence-specific antimicrobials by loading CRISPR-Cas13, an RNA-targeting CRISPR-Cas, on bacteriophage. The constructed antimicrobials were effective against at least Escherichia coli and Staphylococcus aureus. In this paper, we would like to introduce the importance of RNA in bacteriology.

With the rapid spread of multidrug-resistant bacteria, carbapenem-resistant Enterobacteriaceae (CRE) has been reported worldwide as a major concern because of limited treatment options. Carbapenem resistance is mainly due to carbapenem-ase, a carbapenem-degrading enzyme, which is mainly encoded on a plasmid to spread across bacterial species. However, there have been only small-scale attempts to determine the similarities or accommodations of the plasmids disseminating regionwide. We analysed the 230 CRE isolates carrying bla_IMP from 43 medical facilities in the northern Osaka area focusing on the plasmids, the main carriers of the drug resistance genes. Combination of whole genome sequencing and Southern blotting revealed the predominant dissemination of bla_IMP-6 by the pKPI-6 plasmid among genetically distinct isolates, as well as the emergences of derivatives that acquired various advantages. We iden-tified heteroresistance likely causing stealth transmissions, which was generated by the transcriptional regu-lation of bla_IMP-6, stabilization of bla_IMP-6 through chromosomal integration, enhanced carbapenem resistance through plasmid multimerization, or broadened antimicrobial resistance due to a single point mutation in bla_IMP-6. In this article, I dis-cussed the mechanisms of regional spread of CRE and enhancement of carbapenem resistance providing the insights to prevent their disseminations.

Escherichia albertii is an emerging zoonotic enteric pathogen, closely related to E. coli. Several foodborne outbreaks caused by E. albertii accounting for >100 patients have recently occurred in Japan. This bacterium carries eae gene, similar to enteropathogenic E. coli. Some of them harbor Shiga toxin 2 (stx2a, stx2f) genes, primary virulence factor of enterohemorrhagic E. coli (EHEC), suggesting that the Stx2 producers could cause severe diseases such as HUS in humans. However, due to lack of the knowledges about its bacteriological characteristics and of the diagnostic methods, E. albertii-related infections might have been underestimated, and the infection sources and routes have not yet been understood. We had continuously performed molecular epidemiological studies targeting for cytolethal distending toxin-producing E. coli, and unexpectedly found that cdt-II gene-positive isolates were not E. coli but E. albertii. This finding led us to initiate research more focusing on E. albertii. We have constructed simple, efficient and reliable methods for the detection, isolation and identification of this bacterium by developing an E. albertii-specific PCR assay targeting Eacdt genes and E. albertii-selective isolation medium named XRM-MacConkey agar. We have also identified raccoons as a potential natural reservoir of E. albertii through wildlife survey using these methods. Here, I describe what I have studied with my colleagues.