Journal of Applied Microbiology最新文献

Aims: This study aimed to characterize and compare the antimicrobial resistance (AMR) 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 (ESBL) 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 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: In the present study, we tested if terrestrially-derived humic substances (HS) could mitigate the adverse effects of elevated temperature and UVB radiation on the bacterial communities of two hard corals (Montipora digitata and Montipora capricornis), one soft coral (Sarcophyton glaucum), sediment and water. We also examined the impact of temperature, UVB radiation and HS supplementation on coral photosynthetic activity, a proxy for coral bleaching.

Methods and results: We performed a multifactorial experiment using a randomized-controlled microcosm setup. Coral photosynthetic efficiency was measured in vivo using a pulse amplitude modulation (PAM) fluorometer. Bacterial communities were analyzed using 16s rRNA gene sequencing. Corals in HS-supplemented microcosms had significantly higher photosynthetic activities than those in microcosms subjected to elevated temperature and UVB radiation. Additionally, HS supplementation significantly influenced the composition of sediment, water and host-associated bacterial communities. Reef organisms in HS supplemented microcosms contained distinct bacterial communities enriched with groups of potentially beneficial bacteria. In the hard coral Montipora digitata, we observed an interactive effect of HS supplementation, UVB radiation, and temperature.

Conclusion: Our findings indicate that HS significantly modulates coral reef bacterial communities and support the hypothesis that these substances contribute to improved reef resistance to the adverse effects of elevated temperature and UVB radiation.

Aim: This study was dedicated to investigating the role of sulfur metabolic processes in sulfate-reducing bacteria in plant resistance to heavy metal contamination.

Methods and results: We constructed sulfate-reducing bacterial communities based on the functional properties of sulfate-reducing strains, and then screened out the most effective sulfate-reducing bacterial community SYN1, that prevented Cd and Pb uptake in rice through hydroponic experiment. This community lowered Cd levels in the roots and upper roots by 36.60% and 39.88%, respectively, and Pb levels by 35.96% and 51.54%. We also compared two treatment groups, inoculated with SYN1 and exogenously added GSH, and found that both enhanced the antioxidant response of the plants, increased the lignin and GSH contents and the expression of genes related to the phenylpropane biosynthesis pathway (OsCAD, Os4CL, OsCOMT, OsPOD, OsC3H, and OsPAL), and decreased the expression of heavy metal transporter genes (OsHMA2, OsIRT1) expression. There were no significant differences between the two treatments.

Conclusions: Sulfate-reducing bacteria produce GSH through the sulfur assimilation pathway, and GSH can directly chelate heavy metals or enhance plant antioxidant enzyme activities and regulate processes such as uptake and translocation of heavy metals, thus enhancing plant resistance to heavy metal toxicity.

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 LSM 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 μg·mL-1 to 8192 μg·mL-1, but stabilized on 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 lowest 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, decreased Firmicutes/Bacteroidetes ratio and abundance of potential pathogens.

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

Aims: The purpose of this study was to investigate the effects of Bacillus subtilis supplementation on the health of weaned piglets and whether Bacillus subtilis supplementation can reduce the damage of piglets induced by ETEC K88.

Methods and results: The experiment was designed with a 2 × 2 factorial arrangement, comprising the control (CON) group, Bacillus subtilis (PRO) group, Escherichia coli K88 (ETEC) group, and Bacillus subtilis + ETEC (PRO + ETEC) group. Regardless of the presence of ETEC, the addition of PRO increased the piglets' final body weight (FW), average daily gain (ADG), and daily feed intake (ADFI). Additionally, PRO primarily achieves a reduction in heat-stable enterotoxin (ST) levels, suppresses the expression of NF-κB, TLR4, and MyD88 mRNA in the jejunum and ileum, lowers pro-inflammatory factors in the blood and small intestine, enhances the expression of tight junction proteins in the small intestine, improves the composition of the colonic microbiota, increases colonic short-chain fatty acids (SCFAs) contents, thereby alleviates diarrhea and mitigates bodily damage caused by ETEC K88 infection.

Conclusion: The addition of Bacillus subtilis MZ-01 alleviated ETEC K88-induced piglet diarrhoea by reducing heat-stable enterotoxin levels, decreasing pro-inflammatory factors in the blood and intestine, and enhancing the intestinal barrier and tight junction proteins.

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 (FRET) 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 (PVL) by protein immunoblotting. Thermal shift assay (TSA) and cellular thermal shift assay (CETSA) 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 (SPR) 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.

Aims: To determine the optimum conditions for extracting Eucommia ulmoides gum (EUG) from Eucommia ulmoides leaves during fermentation by Coprinellus disseminatus. At the same time, the EUG characteristics were characterized.

Methods and results: The ability of C. disseminatus to secrete degrading enzymes, including enzyme activity and lignocellulose content, was observed by culturing C. disseminatus on a medium with different formulations. Based on the optimal formula, the fermentation conditions were determined by an orthogonal test and EUG was extracted. After that, the characteristic parameters of EUG were determined by FT-IR, 1H-NMR, SEM, POM, DSC, XRD and GPC. The results showed that the lignin and hemicellulose contents in Eucommia leaves decreased significantly with the increase of fermentation days, and C. disseminatus mediated fermentation had an obvious damage effect on the tissue of Eucommia leaves. At the same time, At the same time, xylan can be used as an initiator to induce the expression of degradation-related enzymes. The extraction yield of EUG from Eucommia ulmoides leaves after fermentation was 3.06%, which was significantly improved. The optimum fermentation conditions were 4% inoculum, 28°C fermentation temperature, and pH = 5. The results of infrared FT-IR and 1H-NMR showed that the extract had typical characteristics of EUG, and the surface and quenching part of the EUG were smooth, as observed by SEM. In addition, DSC and XRD analysis show that there are two crystal types, α and β, in the crystallization process of molten EUG. The main crystallization type of EUG extracted from fermented leaves was β type.

Conclusion: The ability of C. disseminatus to produce degrading enzymes can effectively improve the extraction rate of EUG under optimal fermentation process. The method can maintain the integrity of gutta-percha better. EUG has the characteristics of good crystallinity, many β crystal types and high molecular weight.

Mycoplasmas are significant pathogens in human health, implicated in a range of clinical conditions from respiratory infections to urogenital disorders. Their resistance to commonly used antibiotics poses a substantial challenge to treatment and control. This study aims to provide a comprehensive overview of the global distribution of clinical mycoplasmas, elucidate their resistance to various antibiotics, and identify the genetic and molecular mechanisms underlying their resistance. A systematic review and meta-analysis were conducted, collating data from peer-reviewed publications between 2012 and 2024. The UK (100%) and Germany (98%) reported high numbers of respiratory mycoplasmas, with 7% and 2% being resistant to macrolides. For urogenital mycoplasmas, Iceland (99%) and Estonia (94%) reported a high prevalence of Mycoplasma species, whereas the UK (85%), France (82%), and the USA (82%) reported a high prevalence of Ureaplasma species. High resistance rates in Mycoplasma and Ureaplasma have been reported in Greenland (100%) and the UK (86%), respectively. The rising resistance rates in these species underscore an urgent need for updated treatment guidelines and the development of novel therapeutic options. Our findings highlight the importance of tailored antibiotic stewardship and the potential of genomic insights in guiding effective treatment strategies.

Aims: The present study aimed to detect the frequency of vancomycin resistance and virulence genes' profiles of multi-drug-resistant (MDR) enterococcal isolates from different sources and to investigate the sequence heterogeneity between the esp genes of MDR and vancomycin-resistant Enterococcus faecalis isolates from chicken and human sources.

Methods and results: Conventional phenotypic methods identified 91 isolates (60.7%) as Enterococcus species, and these isolates were retrieved from dairy (37/52), chicken (35/54), and human (19/44) origins. Enterococcal isolates were frequently resistant to rifampin (67%), and 38.5% of the isolates were MDR. Of the 22 vancomycin-resistant enterococci (VRE) detected isolates, 11 (50%), 9 (41%), 1 (4.5%), and 1 (4.5%) isolate were identified as E. faecium, E. faecalis, E. casseliflavus, and un-specified Enterococcus spp., respectively. Moreover, 22 (100%) and 19 (86.4%) isolates harbored vanA and vanB genes, respectively. Of note, gelE and asa1 genes were more prevalent among the tested isolates (95.5% each), and the multi-virulence criteria were detected among 68.2% of the examined isolates. The sequences of esp genes of E. faecalis from the chicken breast meat and human urine samples were 100% identical with other esp genes and pathogenicity islands on GeneBank, which is undesirable.

Conclusion: Our findings require strict hygienic measures during the processing of chickens and their by-products to minimize the possibility of transmission of virulent enterococcal strains. Furthermore, the use of antimicrobials in poultry and animal production in developing countries should be controlled to minimize the prevalence of MDR and VRE isolates in humans.

Aims: The aim of this prospective study was to evaluate the diagnostic value of targeted next-generation sequencing (tNGS) in identifying pathogens from bronchoalveolar lavage fluid (BALF) in thoracic surgery ICU patients, offering additional diagnostic methods for clinical practice.

Methods and results: We collected clinical data from patients with suspected pulmonary infections in the thoracic surgery ICU of the Second Affiliated Hospital of Air Force Medical University. A total of 50 patients were enrolled in this study. Traditional pathogen detection (TPD), involving culture and loop-mediated isothermal amplification assays for 12 pathogens, along with tNGS, was employed for pathogen identification in BALF samples. Our findings demonstrated that the positive rate of tNGS was significantly greater than that of TPD (96% vs. 68%). Among the 50 samples analyzed, tNGS identified a total of 165 pathogens, whereas TPD detected only 48 pathogens. The TPD method primarily detected bacteria and fungi, whereas tNGS exhibited broader capabilities, identifying 104 cases with bacteria, 19 with fungi, 34 with DNA viruses, and 8 with RNA viruses. Notably, tNGS displayed enhanced efficiency in detecting atypical pathogens such as fungi, DNA viruses and RNA viruses. Furthermore, compared with TPD, tNGS demonstrated superior sensitivity (95.83% vs. 68.75%).

Conclusions: tNGS technology, characterized by its high sensitivity, specificity, and cost-effectiveness, holds great promise as a reliable diagnostic tool for assessing pulmonary infections in the thoracic surgery ICU patients.