Effects of quorum sensing-interfering agents, including macrolides and furanone C-30, and an efflux pump inhibitor on nitrosative stress sensitivity in Pseudomonas aeruginosa.

Long-term administration of certain macrolides is efficacious in patients with persistent pulmonary Pseudomonas aeruginosa infection, despite how limited the clinically achievable concentrations are, being far below their MICs. An increase in the sub-MIC of macrolide exposure-dependent sensitivity to nitrosative stress is a typical characteristic of P. aeruginosa. However, a few P. aeruginosa clinical isolates do not respond to sub-MIC of macrolide treatment. Therefore, we examined the effects of sub-MIC of erythromycin (EM) on the sensitivity to nitrosative stress together with an efflux pump inhibitor (EPI) phenylalanine arginyl ß-naphthylamide (PAßN). The sensitivity to nitrosative stress increased, suggesting that the efflux pump was involved in inhibiting the sub-MIC of macrolide effect. Analysis using efflux pump-mutant P. aeruginosa revealed that MexAB-OprM, MexXY-OprM, and MexCD-OprJ are factors in reducing the sub-MIC of macrolide effect. Since macrolides interfere with quorum sensing (QS), we demonstrated that the QS-interfering agent furanone C-30 (C-30) producing greater sensitivity to nitric oxide (NO) stress than EM. The effect of C-30 was decreased by overproduction of MexAB-OprM. To investigate whether the increase in the QS-interfering agent exposure-dependent sensitivity to nitrosative stress is characteristic of P. aeruginosa clinical isolates, we examined the viability of P. aeruginosa treated with NO. Although treatment with EM could reduce cell viability, a high variability in EM effects was observed. Conversely, C-30 was highly effective at reducing cell viability. Treatment with both C-30 and PAßN was sufficiently effective against the remaining isolates. Therefore, the combination of a QS-interfering agent and an EPI could be effective in treating P. aeruginosa infections.

Proposal of Helicobacter higonensis sp. nov. isolated from a human clinical specimen, and emended description of Helicobacter valdiviensis Collado, 2014.

We have previously isolated a gram-negative microaerophilic strain, PAGU2000T from a patient presenting with a fever in Kumamoto Prefecture, Japan. The present study aimed to comprehensively analyze the taxonomy of the isolated strain using a polyphasic approach. The 16S rRNA gene sequence analysis indicated that the strain was a member of enterohepatic Helicobacter. The strain PAGU2000T shared a 97.5% 16S rRNA gene nucleotide identity with Helicobacter valdiviensis, and this taxonomic position was confirmed by phylogenetic analysis of the GyrA amino acid sequences. The proposed strain PAGU2000T has a 1.482 Mbp chromosome with a DNA G + C content of 31.3 mol% and encodes 1520 predicted coding sequences. The average nucleotide identity between the strain PAGU2000T and type strain of H. valdiviensis was 70.3%, which was lower than the recommended threshold of 95% for species delineation. The strain PAGU2000T was a motile, non-spore-forming, and spiral-shaped bacterium, exhibiting catalase and oxidase activities but not urease and nitrate reduction. This study demonstrates that the isolate represents a novel species within enterohepatic Helicobacter, for which the name Helicobacter higonensis is proposed (type strain: PAGU2000T = GTC 16811T = LMG 33095T). In this study, we describe the phenotypic and morphological features of this strain and propose an emended description of some biochemical traits of H. valdiviensis.

Comparison of the effects of cefmetazole and meropenem on microbiome: A pilot study.

BACKGROUND: Cefmetazole (CMZ) is a carbapenem-sparing option in the treatment of extended-spectrum beta-lactamase (ESBL)-producing bacterial infection. In this pilot study, we aimed to compare the effects of antimicrobial treatment (meropenem [MP] and CMZ) with those of no antimicrobial treatment (control group) on the microbiome. METHODS: The study was a multicenter, prospective, observational pilot study conducted from October 2020 to October 2022. Feces and saliva samples were collected for microbiome analyses at two time points (early-period: days 1-3; and late-period: days 4-30) for the antimicrobial treatment group, and at one time point for the control group. RESULTS: Five feces (MP-F and CMZ-F) and five saliva (MP-S and CMZ-S) samples were included in the MP and the CMZ groups. Ten feces (C-F) and saliva (C-S) samples were included in the control group. Group α diversity was notably lower in the late-period MP-F group than the control group as determined with the Shannon richness index. ß diversity analysis of the feces samples based on weighted and unweighted UniFrac distances revealed distinctions in both the late-period CMZ-F and MP-F groups compared with the control group. Weighted UniFrac analysis showed that only the early-period MP-F group differed from the control group. In the saliva samples, weighted and unweighted UniFrac analyses showed significant differences between the control group and the early CMZ, late CMZ, and late MP groups. CONCLUSIONS: MP treatment may cause larger impact on the feces microbiome than CMZ in Japanese patients.

Molecular Epidemiology of Escherichia coli Resistant to Carbapenems, Fluoroquinolones, and Aminoglycosides Isolated from One of the Largest Hospitals in Vietnam in 2014-2019.

Introduction: Multidrug-resistant (MDR) Gram-negative bacilli including carbapenem-resistant Gram-negative Enterobacteriaceae (CRE) threaten global health. Little is known, however, about the distribution of antimicrobial resistance genes in MDR isolated from patients in Vietnamese hospitals. In this study, we collected MDR Escherichia coli, defined as E. coli resistance against all fluoroquinolones, aminoglycosides, and carbapenems. Aim: This study was designed to clarify the molecular epidemiology of Escherichia coli isolates resistant to carbapenems, fluoroquinolones, and aminoglycosides isolated from patients admitted to one of the largest hospitals in Vietnam in 2014-2019 based on both whole-genome sequencing (WGS) and phenotypic data. Methodology. Sixty-seven Vietnamese isolates screened by drug resistance by the disk test were subjected to WGS, and their sequences were analyzed to determine their multilocus sequence type (MLST), O-types, H-types, distribution of drug resistance genes, plasmid types, pathogenicity islands (PIs), virulence factor distribution, and phylogenetic evolution using the WGS data. Results: Among the STs detected, ST410 was relatively dominant. Dominant O-types and H-types were O102 and H9 and showed some links, such as those between O102 and H8. The most dominant plasmid type and carbapenemase type were 4 and NDM-5, respectively. MLST, O-types, H-types, plasmid types, and types of carbapenemases were very heterogeneous among the isolates, with no clear correlation between them. Dominant plasmid type carrying drug resistance gene was IncQ1_1. The percentage of isolates positive for drug resistance genes, such as anti-beta-lactams and aminoglycosides, was relatively high because the isolates screened were resistant to carbapenems, fluoroquinolones, and aminoglycosides. Conclusions: MDR E. coli isolates isolated at a high-volume Vietnamese hospital were very heterogeneous, suggesting that they were acquired from different sources, including nosocomial infection, animals, and water. Eradication of MDR E. coli from hospitals and other clinical environments is very challenging because a single measure may be ineffective.

Streptococcus suis subsp. hashimotonensis subsp. nov.: Lancefield group A antigen-positive organisms isolated from human clinical specimens and wild boar oral cavity samples.

Three Streptococcus suis-like strains positive for Lancefield antigen group A were isolated from human boar bite wounds and the oral cavities of boars in Hashimoto City, Wakayama Prefecture, Japan, and their taxonomic positions were investigated. Application of the VITEK2 system identified all three isolates as S. suis with > 94 % probability. The isolates were assigned to S. suis based on the results of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis (Biotyper score of 2.382) but were differentiated according to the characteristic signal peaks (4709 m/z and 9420 m/z) that were not present for S. suis. Sequence analysis of the 16S rRNA and sodA genes determined that the isolates were similar to S. suis; however, these genes appeared on a phylogenetic sub-branch. Phylogenetic analysis of the whole chromosomal DNA showed that the isolate formed a cluster with S. suis but with clear divergence. The average nucleotide index using BLAST between the clinical isolate (PAGU 2482) and a closely related reference strain of S. suis was 94.75 %, which was not clearly conclusive; however, digital DNA-DNA hybridization showed a value of 61.2 %. Biochemical reactions, including those with acid phosphatase, α-chymotrypsin, and tagatose (acidification), distinguished our isolates from S. suis. Thus, based on phylogenetic, genomic, and phenotypic characteristics and MALDI-TOF-MS signal patterns, we propose that the isolate with Lancefield group A positive characteristics be designated as a novel subspecies, Streptococcus suis subsp. hashimotonensis subsp. nov., with the type strain PAGU 2482T (GTC 18290T = CCUG 77434T).

Genetic Characterization of Streptococcus pyogenes emm89 Strains Isolated in Japan From 2011 to 2019.

Invasive infection caused by Streptococcus pyogenes emm89 strains has been increasing in several countries linked to a recently emergent clade of emm89 strains, designated clade 3. In Japan, the features of emm89 S. pyogenes strains, such as clade classification, remains unknown. In this study, we collected emm89 strains isolated from both streptococcal toxic shock syndrome (STSS) (89 STSS isolates) and noninvasive infections (72 non-STSS isolates) in Japan from 2011 to 2019, and conducted whole-genome sequencing and comparative analysis, which resulted in classification of a large majority into clade 3 regardless of disease severity. In addition, invasive disease-associated factors were found among emm89 strains, including mutations of control of virulence sensor, and absence of the hylP1 gene encoding hyaluronidase. These findings provide new insights into genetic features of emm89 strains.