Journal of Applied Microbiology最新文献

Aims: This study aimed to characterize and compare the antimicrobial resistance profiles of clinically relevant bacterial taxa isolated from biting stable flies (Stomoxys spp.) and bovine manure samples collected at a dairy research facility over the course of an entire fly breeding season. The presence of extended-spectrum beta-lactamase and other antimicrobial resistance genes (ARGs) was also examined.

Methods and results: A total of 606 fly- and 180 manure-derived strains were tested via disk diffusion for susceptibility to commonly administered antibiotics used in veterinary and human medicine. A small percentage of Enterobacterales exhibited resistance to the tested antimicrobials, including ceftiofur and other beta-lactam antibiotics. Extended spectrum beta-lactamase genes (TEM, CTX, OXA, CMY) were detected by polymerase chain reaction (PCR) amplification in ceftiofur-resistant Escherichia coli, Klebsiella, and Enterobacter spp. isolates. We additionally identified pirlimycin-resistant Staphylococcus and Mammaliicoccus spp. isolates encoding lnuA, a lincosamide resistance gene found primarily on small mobilizable plasmids.

Conclusions: These findings highlight the significance of stable flies in the carriage of antimicrobial-resistant bacterial strains and plasmid-associated ARGs on dairy farms.

Aims: To prevent peri-implantitis, we investigated the adhesion of periodontopathogenic bacteria to titanium surfaces using a hydrophobic 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer to inhibit adhesion.

Method and results: We immersed titanium plates (TiPs) coated with a hydrophobic MPC polymer in a bacterial suspension for 30 min or 24 h and measured the number of adherent bacteria. Bacteria adhering to the TiPs were observed using scanning electron microscopy (SEM). Furthermore, mimicking an oral cavity, TiPs coated with MPC polymer and saliva, were immersed in bacterial suspensions of Porphyromonas gingivalis, Fusobacterium nucleatum, and Streptococcus mutans for 24 h, and adenosine triphosphate in the adherent bacteria was measured.Bacterial adhesion was significantly inhibited on MPC polymer-coated TiPs after 30 min and 24 h. SEM results showed a similar trend. Bacterial adhesion was significantly inhibited on MPC polymer-treated TiPs in the presence of saliva, both before and after MPC treatment. Furthermore, their effectiveness was maintained when the MPC polymer-treated TiPs were stored in saline for 1 week.

Conclusions: Hydrophobic MPC polymer coating on TiP surface inhibited bacterial adhesion, indicating that it may be effective in preventing peri-implantitis.

Aim: The current study aimed to establish a phenotypic and genotypic characterization record of a novel lytic bacteriophage (phage) against multidrug-resistant (MDR) Escherichia coli (E. coli) infections.

Methods and results: Phenotypic characterization of the isolated phage included the assessment of phage morphology, host range, stability, and antibiofilm activity. The isolated phage vB_EcoM_ECO78 demonstrated a high lytic activity against MDR E. coli and E. coli serotypes O78: K80: H12 and O26: H11. Additionally, it showed a marked antibiofilm activity and high physical stability at a wide range of temperatures and pH. Genotypic investigations identified a double-stranded DNA genome of 165 912 base pairs (bp) spanning 258 open reading frames (ORFs), out of which 149 ORFs were identified and annotated. In vivo analysis further confirmed the therapeutic potential of vB_EcoM_ECO78 which effectively increased the survival of mice infected with MDR E. coli.

Conclusion: The isolated phage vB_EcoM_ECO78 exhibits considerable stability and antibiofilm activity against MDR E. coli isolates, supported by notable environmental fitness and in vivo antibacterial capability.

Aims: Plant growth-promoting rhizobacteria (PGPR) improve microbial community structure, promote crop growth, and reduce greenhouse gas emissions in agricultural soils; however, the effects of PGPR fermentation on the growth and salt tolerance of tomato plants remain unclear. In this study, we aimed to investigate the effects of the PGPR Stutzerimonas stutzeri NRCB010 on the microbial communities, tomato growth, and nitrous oxide (N2O) emissions in saline soil by performing a greenhouse pot experiment.

Methods and results: The experiment was conducted under two soil salt concentrations (0 and 3 g kg-1 NaCl) and three treatments (LSFJ broth, NRCB010 cells, and NRCB010 culture). Both salt stress and NRCB010 treatments significantly affected the physicochemical properties and microbial community structure of tomato rhizosphere soil. Treatment with 3 g kg-1 NaCl significantly reduced the shoot and root dry weights of the plants compared with those of the control plants. Application of NRCB010 cells as well as that of culture promoted the growth of tomato seedlings and alleviated salt stress. The copy number changes in the nosZⅠ gene on day 3 and amoA gene on day 25 demonstrated that NRCB010 cells significantly reduced soil N2O emissions when treated with 0 g kg-1 NaCl. Furthermore, soil physicochemical properties, plant biomass, and soil microbial diversity were correlated with each other.

Conclusions: The results emphasize the enormous potential of S. stutzeri NRCB010 culture to resist abiotic stress, promote crop growth, and improve the rhizosphere soil microenvironment; however, its ability to decrease N2O emissions is constrained by soil salinity.

Aims: The aim of this study was to identify sesamin as a Casein hydrolase P (ClpP) inhibitor and to determine whether it could attenuate the virulence of methicillin-resistant Staphylococcus aureus (MRSA).

Methods and results: Through fluorescence resonance energy transfer screening, a natural compound sesamin demonstrated a significant inhibitory effect on ClpP enzyme activity with an IC50 of 20.62 μg/ml. Sesamin suppressed the expression of virulence factors of MRSA such as α-hemolysin (Hla) and Panton-Valentine leucocidin by protein immunoblotting. Thermal shift assay and cellular thermal shift assay showed that sesamin could bind to ClpP and enhance the thermal stability of ClpP. Furthermore, the binding affinity between sesamin and ClpP was determined by surface plasmon resonance with a KD value of 7.18 × 10-6 M. Molecular docking, dynamics simulations and point mutation analysis confirmed the stability of the sesamin-ClpP complex with a -10.184 kcal/mol total binding energy and identified PHE-174 in ClpP as a key binding site. In mice pneumonia model, sesamin combined vancomycin treatment markedly reduced the pathogenicity of MRSA-infected mice, offering protection against fatal lung infections.

Conclusions: Overall, these findings validate sesamin as a promising compound that targets ClpP, reducing virulence factor expression, that holds potential as a hit compound against MRSA infections.

Aim: The primary objective of the study was to assess the applicability of a growth model initially developed for Aspergillus brasiliensis on solid surfaces to other micromycetes, specifically Fusarium and Cladosporium. Additionally, the research identifies conditions for complete growth inhibition of these micromycetes using two distinct sources of a nonthermal plasma (NTP).

Methods and results: The growth model incorporates two critical parameters: growth rate and growth delay, which effectively describe the growth dynamics and the impact of NTP treatments. For complete inactivation of Fusarium solani and Cladosporium halotolerans, a single 10-minute exposure of a 0-, 24-, 48-, or 72-hour-old culture to a diffuse coplanar surface barrier discharge (DCSBD) was sufficient. A point-to-ring (PtR) corona discharge completely suppressed the growth of freshly inoculated cultures and 24-hour-old cultures. However, when 48- and 72-hour-old cultures were exposed to the point-to-ring NTP for 10 min, only partial inactivation was observed.

Conclusions: The article verifies a model for simulating the surface growth of micromycetes and evaluates the efficacy of two NTP sources in deactivating F. solani and C. halotolerans.

Aims: Supplementing Lactobacillus alongside antibiotic treatment was a curative strategy to modulate gut microbiota and alleviate antibiotic-associated dysbiosis. But the lactobacilli that are used as probiotics are sensitive or have a low level of resistance to antibiotics, so they usually cannot achieve their beneficial effect, since they are killed by the applied antibiotics. This work aimed to develop the highly resistant Lactiplantibacillus plantarum subsp. plantarum ATCC14917 to cephalexin and evaluate its recovery effects of antibiotic-resistant L. plantarum on the antibiotic-disturbed intestinal microbiota using a mice model.

Methods and results: After successive growth in lactic acid bacteria susceptibility medium broth containing a gradually increasing concentration of cephalexin for 70 days, the minimum inhibitory concentration (MIC) of L. plantarum ATCC14917 to cephalexin significantly increased from 16 to 8192 μg ml-1, but stabilized at 4096 μg ml-1. After sequencing and sequence analysis, no mutated genes were detected on mobile elements, showing that horizontal transfer of mutated genes could not occur. Compared to the control group (Con), feeding mice with cephalexin (1 mg ml-1; Cep) led to a decrease in alpha diversity. However, concurrently used cephalexin and L. plantarum (Cep + LpR) increased the alpha diversity in both microbial richness and diversity. The Cep + LpR group showed a lower distance with the Con group than either Cep or Cep + LpS groups, suggesting that resistant L. plantarum treatment was more effective than the original strain for the recovery of intestinal microbiota. Compared to the cephalexin-treated group, concurrent ingestion of cephalexin together with resistant L. plantarum significantly increased the proportion of beneficial bacteria and decreased Firmicutes/Bacteroidetes ratio and abundance of potential pathogens.

Conclusions: The use of antibiotic-resistant L. plantarum ATCC14917 contributed to a much faster and richer recovery of the gut microbiota disturbed by antibiotic treatment compared to the original strain.

Aim: The aim of this study was to isolate Klebsiella spp. from clinically healthy animals fed diets with or without antimicrobial growth promoters (AGP). Additionally, the study evaluated whether the inclusion of growth promoters affected the recovery of multi-drug-resistant isolates.

Methods and results: A total of 144 isolates were obtained from rectal swabs on Simmons citrate agar supplemented with 1% inositol. Of these, 45 non-replicative isolates underwent extensive characterization, including molecular and phenotypic analyses. Sequencing identified that 77% were Klebsiella pneumoniae, 14.5% K. aerogenes, and 8.5% K. variicola. Isolates exhibiting the same polymorphic profiles were detected across different animals and treatments, with and without AGP. Seventy-one percent were multidrug-resistant, as determined by disk diffusion testing. The isolates harbored genes such as mcr-1, blaCTX-M-2, sul2, tetB, qnrS, and dfrA, among others. Additionally, genes encoding siderophores like enterobactin, aerobactin, and yersiniabactin were detected via Polymerase Chain Reaction (PCR). Thirty-nine isolates were strong biofilm producers, 45% moderate, and 16% weak in vitro tests. The predominant genetic profiles included single, double, or triple-locus variants of ST25, ST147, and ST4691. Two novel sequence types were identified: ST7694 (K. pneumoniae) and ST7699 (K. variicola). Survival and persistence analyses in Galleria mellonella showed that these isolates exhibited a virulent phenotype and an enhanced capacity for multiplication in the early hours of infection.

Conclusion: Clinically healthy swine act as reservoirs for multidrug-resistant Klebsiella spp. exhibiting significant virulence phenotypes. The identification of novel sequence types contributes to epidemiological surveillance and the One Health framework.

Aims: This study aims to evaluate the antiviral activity of sophorolipids against herpes simplex virus type 1 (HSV-1) and develop an anti-herpetic formulation for treatment of cutaneous lesions caused by HSV-1.

Methods and results: The antiherpetic activity of sophorolipids was evaluated in vitro against both sensitive (KOS) and acyclovir-resistant HSV-1 strains. used as a model to assess the antiviral activity of sophorolipids against non-enveloped viruses Poliovirus was used as a model to assess the antiviral activity of sophorolipids against non-enveloped viruses. The results showed that sophorolipids exhibit effective antiviral activity against both strains with low cytotoxicity to VERO cells. However, antiviral activity against poliovirus was not observed, suggesting that sophorolipids specifically target enveloped virus. In vivo, the sophorolipid-based cream formulation demonstrated good stability and efficacy in reducing herpetic lesions, including those caused by the drug-resistant strain. Promising antiviral activity was confirmed through histopathological analysis, indicating a reduced occurrence of tissue damage in the treated group compared to the viral control.

Conclusions: Sophorolipids, whether isolated or incorporated as an active ingredient in a cream formulation, represent a promising and innovative alternative for the treatment of cutaneous lesions caused by HSV-1, including strains resistant to the reference drug.