Fems Microbiology Letters最新文献

Adaptation to environmental change during both colonization and infection is essential to the pathogenesis of Staphylococcus aureus. Like other bacterial pathogens that require potassium to fulfill nutritional and chemiosmotic requirements, S. aureus has been shown to utilize potassium transport to modulate virulence gene expression, antimicrobial resistance, and osmotic tolerance. Recent studies examining the role for potassium uptake in mediating S. aureus physiology have also described its contribution in mediating carbon flux within central metabolism and generation of a proton motive force. Here, we utilize a pH-sensitive green fluorescent protein to examine the temporal regulation of S. aureus intracellular pH by potassium and sodium under various environmental conditions, including extracellular pH and antibiotic stress. Our results distinguish unique conditions and transport mechanisms that utilize these ions to modulate cytoplasmic pH homeostasis, and they identify these processes as a novel mechanism of intrinsic ampicillin resistance in S. aureus.

The ResistAZM randomized controlled trial found that the receipt of ceftriaxone/azithromycin, compared to ceftriaxone was not associated with an increase in the proportion of oral commensal Neisseria spp. and streptococci with azithromycin resistance 14 days after treatment. We repeated the analyses by measuring the minimum inhibitory concentrations (MICs) of azithromycin and ceftriaxone for individual colonies of commensal Neisseria spp. and streptococci at day 0 and day 14 in both arms. The receipt of ceftriaxone/azithromycin but not ceftriaxone was associated with an increase in azithromycin MIC for both Neisseria spp. (P < 0.0001) and streptococci (P = 0.0076). Likewise, ceftriaxone/azithromycin but not ceftriaxone monotherapy was associated with an increase in ceftriaxone MICs in Neisseria spp. (P = 0.0035). Whereas the proportion method failed to detect an association between the receipt of azithromycin and increased macrolide resistance, the MIC distribution method detected this effect. The MIC distribution method is thus a more sensitive method to assess the effect of antimicrobials on antimicrobial susceptibility.

Background: The ResistAZM randomized controlled trial found that the receipt of ceftriaxone/azithromycin, compared to ceftriaxone was not associated with an increase in the proportion of oral commensal Neisseria spp. and streptococci with azithromycin resistance 14 days after treatment.

Methods: We repeated the analyses by measuring the minimum inhibitory concentrations (MICs) of azithromycin and ceftriaxone for individual colonies of commensal Neisseria spp. and streptococci at day 0 and day 14 in both arms.

Results: The receipt of ceftriaxone/azithromycin but not ceftriaxone was associated with an increase in azithromycin MIC for both Neisseria spp. (P < 0.0001) and streptococci (P = 0.0076). Likewise, ceftriaxone/azithromycin but not ceftriaxone monotherapy was associated with an increase in ceftriaxone MICs in Neisseria spp. (P = 0.0035).

Conclusions: Whereas the proportion method failed to detect an association between the receipt of azithromycin and increased macrolide resistance, the MIC distribution method detected this effect. The MIC distribution method is thus a more sensitive method to assess the effect of antimicrobials on antimicrobial susceptibility.

Seasonal changes in the diversity of tea plant endophytic fungi and the effects of sample storage conditions on detection were analyzed. Tea leaves were collected from the Saitama Tea Research Institute in Japan during winter (January 2020) and summer (August 2020). The effects of storage temperature (5, 10, 20, 25, and 30°C) and durations (1, 2, 3, 4, 5, 6, and 7 days) on endophytic fungal diversity and community structure were investigated. In summer, storage period and temperature did not affect the fungal colonization rate, frequency, and composition. In winter, storage temperature and period significantly affected the endophytic community structure. Fungal diversity was higher in winter than in summer. Positive relationships between diversity index and storage temperature and period were observed in winter, whereas the opposite trend was observed in summer. Our findings provide insight into the ecology of foliar endophytes of tea plants and the importance of proper sample collection and storage for microbiome studies.

Enterococcus raffinosus, named by Collins et al. in 1989, is a cocci-shaped bacterium that typically appears in pairs or short chains. As a Gram-positive and non-motile bacterium, it grows at 10°C-45°C, exhibiting negative peroxidase activity [1]. It is a normal flora in the oropharynx and gastrointestinal tract of domestic cats [2] and can also be isolated from human rectal swabs [3], it belongs to the same genus Enterococcus as Enterococcus faecalis and Enterococcus faecium. Enterococcus faecalis and Enterococcus faecium constitute 90% of clinically isolated strains. However, the incidence of other enterococci, excluding E. faecalis and E. faecium, is on the rise [4]. In this case report, a patient with pediatric urinary tract infections caused by E. raffinosus was presented, and a summary of relevant literature was provided.

Short-term adaptation of the microbiota could promote nutrient degradation and the host health. While numerous studies are currently undertaking feeding trials using sustainable diets for the aquaculture industry, the extent to which the microbiota adapts to these novel diets is poorly described. The incorporation of carbohydrates (CHO) within a 100% plant-based diet could offer a novel, cost-effective energy source that is readily available, potentially replacing the protein component in the diets. In this study, we investigated the short-term (3 weeks) effects of a high CHO, 100% plant-based diet on the mucosal and digesta associated microbiota diversity and composition, as well as several metabolic parameters in rainbow trout. We highlighted that the mucosa is dominated by Mycoplasma (44.86%). While the diets did not have significant effects on the main phyla (Proteobacteria, Firmicutes, and Actinobacteria), after 3 weeks, a lower abundance of Bacillus genus, and higher abundances of four lactic-acid bacteria were demonstrated in digesta. In addition, no post-prandial hyperglycemia was observed with high carbohydrate intake. These results provide evidence for the rapid adaptation of the gut microbiota and host metabolism to high CHO in combination with 100% plant ingredients in rainbow trout.

With the growing threat of drug-resistant Acinetobacter baumannii, there is an urgent need to comprehensively understand the physiology of this nosocomial pathogen. As penicillin-binding proteins are attractive targets for antibacterial therapy, we have tried to explore the physiological roles of two putative DD-carboxypeptidases, viz., DacC and DacD, in A. baumannii. Surprisingly, the deletion of dacC resulted in a reduced growth rate, loss of rod-shaped morphology, reduction in biofilm-forming ability, and enhanced susceptibility towards beta-lactams. In contrast, the deletion of dacD had no such effect. Interestingly, ectopic expression of dacC restored the lost phenotypes. The ∆dacCD mutant showed properties similar to the ∆dacC mutant. Conversely, in vitro enzyme kinetics assessments reveal that DacD is a stronger DD-CPase than DacC. Finally, we conclude that DacC might have DD-CPase and beta-lactamase activities, whereas DacD is a strong DD-CPase.

Salmonella enterica (S. enterica) is the most common food and waterborne pathogen worldwide. The growing trend of antibiotic-resistant S. enterica poses severe healthcare threats. As an alternative antimicrobial agent, bacteriophage-encoded endolysins (endolysins) are a potential agent in controlling S. enterica infection. Endolysins are enzymes that particularly target the peptidoglycan layer of bacterial cells, leading to their rupture and destruction. However, the application of endolysins against Gram-negative bacteria is limited due to the presence of the outer membrane in the cell wall, which hinders the permeation of externally applied endolysins. This study aimed the prokaryotic expression system to produce the recombinant endolysin ENDO-1252, encoded by the Salmonella bacteriophage-1252 associated with S. Enteritidis. Subsequently, ENDO-1252 had strong lytic activity not only against S. Enteritidis but also against S. Typhimurium. In addition, ENDO-1252 showed optimal thermostability and lytic activity at 25°C with a pH of 7.0. In combination with 0.1 mM EDTA, the effect of 120 µg of ENDO-1252 for 6 hours exhibited the highest lytic activity, resulting in a reduction of 1.15 log or 92.87% on S. Enteritidis. These findings suggest that ENDO-1252 can be used as a potential and innovative antibacterial agent for controlling the growth of S. Enteritidis.

The extensive use of chemical pesticides, such as herbicides, has resulted in significant environmental pollution. Microbial degradation represents a crucial approach for managing this pesticide-associated pollution, with enrichment culturing serving as a method for isolating pesticide-degrading microorganisms. However, the efficiency of this strategy is limited, often yielding only a few isolated strains. In this study, a new mineral salt medium (MSM) was developed, and a high-throughput method was used for screening pendimethalin-degrading bacteria by measuring the bacterial growth in the MSM. The utilization of this method resulted in the isolation of 56 pendimethalin-degrading bacteria from approximately 2000 bacterial strains, including 37 Bacillus spp., 10 Alcaligenes spp., 5 Pseudomonas spp., and other 4 strains identified for the first time as pendimethalin-degrading strains. This method may hold promise not only for isolating bacterial strains capable of degrading other pesticides but also for facilitating the utilization of the substantial bacterial strains stored in bacterial banks.

Background: Vibrio vulnificus NCIMB2137, a Gram-negative, metalloprotease negative estuarine strain was isolated from a diseased eel. A 45 kDa chymotrypsin-like alkaline serine protease known as VvsA has been recently reported as one of the major virulence factor responsible for the pathogenesis of this strain. The vvsA gene along with a downstream gene vvsB, whose function is still unknown constitute an operon designated as vvsAB.

Objective: This study examines the contribution of VvsB to the functionality of VvsA.

Method: In this study, VvsB was individually expressed using Rapid Translation System (RTS system), followed by an analysis of its role in regulating the serine protease activity of VvsA.

Result: The proteolytic activity of VvsA increased upon the addition of purified VvsB to the culture supernatant of V. vulnificus. However, the attempts of protein expression using an E. coli system revealed a noteworthy observation that protein expression from the vvsA gene exhibited higher protease activity compared to that from the vvsAB gene within the cytoplasmic fraction. These findings suggest an intricate interplay between VvsB and VvsA, where VvsB potentially interacts with VvsA inside the bacterium and suppress the proteolytic activity. While outside the bacterial milieu, VvsB appears to stimulate the activation of inactive VvsA.

Conclusion: The findings suggest that Vibrio vulnificus regulates VvsA activity through the action of VvsB, both intracellularly and extracellularly, to ensure its survival.

Indole serves as a signaling molecule that could regulate different bacterial physiological processes, including antibiotic resistance through biofilm formation and drug efflux pump activity. In Escherichia coli, indole is produced through the tryptophan pathway, which involves three permeases (Mtr, AroP, and TnaB) that can transport the amino acid tryptophan. Although these permeases play distinct roles in the secretion of indole biosynthesis, their impact on multidrug resistance mediated by indole remaines unclear. This study was designed to investigate the connection between the tryptophan transport system and antibiotic resistance by constructing seven gene deletion mutants from E. coli MG1655 (wild type). Our result showed that deletion of the aroP or tnaB gene led to increased antibiotic resistance as evaluated by MICs for different antibiotics. Efflux activity test results revealed that the increased antibiotic resistance was related with the AcrAB-Tolc drug efflux pump in the mutants. The transcriptome analysis further demonstrated that decreased susceptibility to kanamycin and ampicillin in E. coli was accompanied by reduced accumulation of reactive oxygen species and decreased motility. These findings highlight the substantial influence of the tryptophan transport system on antibiotic resistance in E. coli, which is crucial for developing strategies against antibiotic resistance in bacterial infections.