Publications by authors named "Aki Hirabayashi"

Article Synopsis
  • Tigecycline is an antimicrobial with effectiveness against a wide range of bacteria, but resistance genes, specifically tnfxB-tmexCD-toprJ, have been spreading globally, raising concerns about their prevalence in Japan.
  • A study analyzed genome sequences from 5143 Enterobacterales clinical isolates collected in Japan to investigate the presence of the tnfxB-tmexCD-toprJ gene cluster.
  • The study found two Klebsiella pneumoniae isolates carrying the tnfxB1-tmexCD1-toprJ1 cluster along with other antibiotic resistance genes, indicating a potential public health threat from multidrug-resistant Enterobacterales even in regions with low clinical use of tigecycline.
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Surveillance of antimicrobial resistance (AMR) is a crucial strategy to combat AMR. Using routine surveillance data, we could detect and control hospital outbreaks of AMR bacteria as early as possible. Previously, we developed a framework for automatic detection of clusters of AMR bacteria using SaTScan, a free cluster detection tool integrated into WHONET.

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  • The study examines how the COVID-19 pandemic affected the occurrence of certain respiratory bacteria, highlighting significant changes in their epidemiology due to new social behaviors and non-pharmaceutical interventions (NPIs).
  • Researchers analyzed data from a national surveillance database from 2018 to 2021, comparing cases of four bacteria before and after the pandemic, focusing on different age groups and specimen sources.
  • Findings showed a significant drop in cases of S. pneumoniae, H. influenzae, and S. pyogenes between 2019 and 2020, with a resurgence in 2021, particularly among young children, indicating the varied impact of NPIs on different bacteria and demographics.
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Japan is a country with an approximate 10% prevalence rate of carbapenem-resistant (CRPA). Currently, a comprehensive overview of the genotype and phenotype patterns of CRPA in Japan is lacking. Herein, we conducted genome sequencing and quantitative antimicrobial susceptibility testing for 382 meropenem-resistant CRPA isolates that were collected from 78 hospitals across Japan from 2019 to 2020.

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  • A study was conducted to compare the disease and economic burden of methicillin-resistant Staphylococcus aureus (MRSA) infections versus methicillin-susceptible Staphylococcus aureus (MSSA) infections, and between MRSA infections and MRSA colonization.
  • Data from 496 in-patients with infections and 1178 with MRSA colonization were analyzed to evaluate factors like in-hospital mortality, length of stay, and hospital charges.
  • Results showed no significant difference in mortality rates between MRSA and MSSA or MRSA infections and colonization; however, MRSA infections led to longer hospital stays and higher hospital charges compared to MSSA and colonization.
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Article Synopsis
  • Monitoring antibiotic-resistant bacteria (ARB) and understanding their impact on the human microbiome and resistome is essential for public health, especially in long-term care facilities where residents often harbor ARB.
  • This study used shotgun metagenome sequencing on oral and stool samples from these residents to analyze the effects of antimicrobial treatment, finding increased abundance of certain archaea and antimicrobial resistance genes (ARGs) in those with recent treatment histories.
  • Interestingly, the research showed that taxonomic diversity in gut microbiota did not decrease during antimicrobial treatment, indicating that the impact of a single drug might be less significant than previously believed, particularly in older adults.
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Background: Antimicrobial use (AMU) in primary care is a contributing factor to the emergence of antimicrobial-resistant bacteria. We assessed the potential effects of AMU on the prevalence of a combination of resistance phenotypes in bacteraemic Escherichia coli in outpatient care settings between primary care facilities ('clinics') and hospitals.

Methods: Population-weighted total AMU calculated from the national database was expressed as DDDs per 1000 inhabitants per day (DID).

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Article Synopsis
  • * The study involved genome sequencing and testing of 4,195 bacterial isolates from Japan to identify mechanisms of 3GC resistance and found that certain resistance genes were often located on similar plasmids.
  • * Findings included strains that were resistant to carbapenems but appeared susceptible in standard testing, highlighting the need for national genomic surveillance to better understand and combat antibiotic resistance.
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  • The study examines the rising rates of anaerobic bacteremia worldwide, emphasizing the need for ongoing monitoring of these infections.
  • It analyzes data from a significant longitudinal study in Japan (2011-2020), focusing on antibiotic resistance among various anaerobic bacteria isolated from blood cultures.
  • Results show a notable increase in bacteremia cases linked to specific species, with some antibiotic resistances increasing, which suggests a connection to factors like colorectal cancer incidence and advances in detection methods.
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Background: Surgical site infections (SSIs) are among the most common healthcare-associated infections. Laparoscopy is increasingly being used in various surgical procedures. However, no study has examined the association between the proportion of laparoscopic procedures and the incidence of SSIs in digestive surgery using nationwide surveillance data.

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Antimicrobial-resistant (AMR) bacterial infections caused by clinically important bacteria, including ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) and mycobacteria (Mycobacterium tuberculosis and nontuberculous mycobacteria), have become a global public health threat. Their epidemic and pandemic clones often accumulate useful accessory genes in their genomes, such as AMR genes (ARGs) and virulence factor genes (VFGs). This process is facilitated by horizontal gene transfer among microbial communities via mobile genetic elements (MGEs), such as plasmids and phages.

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Carbapenemase-producing Enterobacterales (CPE) raise concerns about the treatment options for infectious diseases and infection control. We conducted a multicenter study to clarify the molecular epidemiology of CPE in the Aichi Prefecture during the first 3-month period from 2015 to 2019. Carbapenemase production was screened using a modified carbapenem inactivation method, and the genotypes of the carbapenemase genes were determined by polymerase chain reaction sequencing.

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Article Synopsis
  • * The prevalence of most Candida species remained stable, but notable declines were observed in C. albicans, C. parapsilosis, and C. tropicalis, while C. guilliermondii's prevalence increased.
  • * Significant resistance to azole drugs and micafungin was found in several Candida species, particularly C. glabrata, C. tropicalis, and C. krusei, highlighting the need for ongoing monitoring of these infections.
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Objectives: Tigecycline resistance mediated by the mobile tigecycline-inactivating enzyme gene tet(X) in Gram-negative bacteria is an emerging concern for global public health. However, limited information is available on the distribution of tet(X) in the natural environment. In this study, we investigated the presence of tet(X) in environmental Gram-negative bacteria.

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  • The study aimed to investigate the presence of mobile colistin resistance (mcr) genes in Enterobacterales isolates in Vietnam, focusing on variants other than mcr-1.
  • It discovered two clinical isolates, NIHE14-1904 and MH17-539M, both carrying the mcr-9 gene on similar IncHI2 plasmids obtained from medical institutions in Hanoi.
  • This marks the first detection of mcr-9-harbouring Enterobacterales in Vietnam, highlighting the need for ongoing monitoring due to the potential for widespread dissemination of these resistant plasmids.
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Tigecycline is a last-resort antimicrobial against carbapenemase-producing (CPE). However, mobile tigecycline resistance genes, (X) and , have emerged in China and have spread possibly worldwide. Tet(X) family proteins function as tigecycline-inactivating enzymes, and TMexCD-TOprJ complexes function as efflux pumps for tigecycline.

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Carbapenem-resistant Enterobacterales (CRE) represent a serious threat to public health due to the lack of treatment and high mortality. The rate of antimicrobial resistance of Enterobacterales isolates to major antimicrobials, including carbapenems, is much higher in Vietnam than in Western countries, but the reasons remain unknown due to the lack of genomic epidemiology research. A previous study suggested that carbapenem resistance genes, such as the carbapenemase gene blaNDM, spread via plasmids among Enterobacterales in Vietnam.

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The rapid emergence of carbapenemase-producing gram-negative bacteria (CPGNB) is a global threat due to the high mortality of infection and limited treatment options. Although there have been many reports of CPGNB isolated from Southeast Asian countries, to date there has been no genetic analysis of CPGNB isolated from Cambodia. Sequence-based molecular epidemiological analysis enables a better understanding of the genotypic characteristics and epidemiological significance of antimicrobial-resistant (AMR) bacteria in each country, and allows countries to enact measures related to AMR issues.

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Background: The association between the frequency of surgeries and the incidence of surgical site infections (SSIs) has been reported for various surgeries. However, no previous study has explored this association among video-assisted thoracic surgeries (VATS). Hence, we aimed to investigate the association between the frequency of surgeries and SSI in video-assisted thoracic surgeries.

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Background: Antimicrobial resistance in Neisseria gonorrhoeae is a global health concern. Strains from two internationally circulating sequence types, ST-7363 and ST-1901, have acquired resistance to third-generation cephalosporins, mainly due to mosaic penA alleles. These two STs were first detected in Japan; however, the timeline, mechanism, and process of emergence and spread of these mosaic penA alleles to other countries remain unknown.

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Tigecycline is a last-resort antimicrobial used to treat multidrug-resistant Gram-negative bacterial infections. One of the common antimicrobial resistance mechanisms is the efflux pump system composed of membrane protein complexes to excrete xenobiotic substrates. Recently, a novel gene cluster, , encoding the resistance-nodulation-cell division (RND) efflux pump was identified on plasmids in isolates in China.

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Nontuberculous mycobacterial (NTM) infections in humans have increased in prevalence in recent decades. is one of the most prevalent human pathogenic NTM species worldwide Herein, we report the first isolation of from an indoor domestic cat in Japan. Comparative genome sequence analysis of the feline isolate showed this pathogen is genetically identical to human pathogenic .

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Bacteriophages (phages), or bacterial viruses, are very diverse and highly abundant worldwide, including as a part of the human microbiomes. Although a few metagenomic studies have focused on oral phages, they relied on short-read sequencing. Here, we conduct a long-read metagenomic study of human saliva using PromethION.

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