Microbiology-Sgm最新文献

This study aimed to examine the effects of minocycline (MINO) and hyaluronic acid (HA) on wound healing in rats. MINO/HA was combined with ultrasound therapy for treating wounds infected with Staphylococcus aureus. Cutaneous wounds in 40 female Wistar rats were infected with S. aureus and then randomly divided into four groups: infected-wounded skin treated with sterile saline solution (control group), treated with ultrasound (ultrasound group), treated by a mixture of MINO and HA (MINO+HA group) and treated with a mixture of MINO and HA combined with ultrasound (MINO+HA+ultrasound group). General observations of the wound healing were photographed. After three treatments, bacterial counts were obtained to determine antibacterial efficacy and wound healing was assessed by histological analysis and evaluation of inflammatory cytokine levels (TNF-α and IL-1β) by immunohistochemistry. Compared with the control group, both the MINO+HA group and the MINO+HA+ultrasound group achieved a significant wound square reduction of 43.7% and 54.9 %, respectively (P<0.001). A small number of inflammatory cells, organization of collagen fibres and maturation of granulation tissue were observed in the histological evaluation of the MINO+HA+ultrasound group. The expression levels of TNF-α and IL-1β in the MINO+HA+ultrasound group were decreased compared to both the control group and the MINO+HA group (P<0.001). These findings revealed the possibility of using a mixture of MINO and HA combined with ultrasound to minimize inflammation and promote tissue regeneration during the treatment of wound infections.

Lipooligosaccharides (LOSs) are polar glycolipids found in the cell envelope of many pathogenic mycobacteria. Here, we show that LOS transport in Mycobacterium marinum requires mmpL12, a member of the resistance-nodulation-division family of membrane proteins. Deletion of mmpL12 resulted in a rough colony morphology and increased hydrophobicity. The △mmpL12 mutant accumulated three of the biosynthesis intermediates of LOSs (LOS-I, LOS-II and LOS-III) intracellularly and failed to produce the final product, LOS-IV, suggesting that final glycosylation of LOS-III to yield LOS-IV occurs extracellularly after LOS-III export. In silico structural analysis of the MmpL12 suggests that it is a proton-driven transporter that shares very similar organization with other subclass 1 MmpLs (MmpL1, 2, 4-8 and 9-10), featuring a large periplasmic loop (PD3 domain) which is predicted to form a large coiled coil that may be involved in the trimerization of this subset of MmpL transporters. Furthermore, the long C-terminal extension domain, which is unique to MmpL12, may provide additional trimerization support and scaffold for assembly of additional LOS biosynthetic enzymes. The absence of any extracellular LOS intermediates and of LOS-IV had an impact on virulence, with the mutant strain exhibiting a larger bacterial burden in infected zebrafish embryos.

Cryptosporidiosis, caused by Cryptosporidium parvum, poses significant health risks, particularly for children and immunocompromised individuals. Current treatments are ineffective in these vulnerable groups. This study explores the antiparasitic effects of peptoids against C. parvum. Out of 14 synthetic peptidomimetics (peptoids) screened, TM9 and TM19 exhibited potent anti-cryptosporidial activity with minimal host toxicity. These findings suggest that peptoids could be a promising new therapeutic avenue for cryptosporidiosis, warranting further investigation.

Pseudomonas aeruginosa is an environmentally resilient bacterium and an important cause of both acute and chronic infections in people with impaired natural barriers or immunological defences. Chronic respiratory infection with P. aeruginosa is a major cause of morbidity and mortality in people with airway diseases, including cystic fibrosis (CF) and non-CF bronchiectasis. Chronic airway infection is characterized by periods of relative stability punctuated by pulmonary exacerbations, during which times rapid bacterial outgrowth necessitates intense antimicrobial chemotherapy. The periods of stable infection can be modelled in mice by nasal instillation of airway-adapted P. aeruginosa in saline, leading to prolonged colonization of both upper airway (sinus) and lower airway (lung) environments that is not associated with symptomatic disease. Here, we use NMR metabolomics to investigate the impact of P. aeruginosa colonization on the metabolic landscape of sinuses and lungs. Lung infection led to pronounced changes in the airway metabolome, with significant depletion of glucose and myo-inositol but enrichment of glutathione (GSH), relative to uninfected lungs. Changes in the sinuses were more subtle but could be identified through dimensionality reduction approaches. The NMR spectral peaks that discriminated between infected and uninfected sinuses in partial least squares discriminant analysis included those for lactate and choline but were mostly representative of yet unidentified metabolites. These data highlight the differential impact of infection on separate airway compartments and identify undefined metabolites undergoing pronounced abundance changes during infection.

Mezcal is a spirit obtained from the fermentation and distillation of juices obtained from different agave species. It is one of the distilled beverages with great sociocultural value in different regions of Mexico, and in recent years, it has also gained great economic importance. It is known to present differences in its flavour, thanks to the richness of compounds incorporated within the spirit, which vary according to the agave species used, the microbial population present and the processes involved in its manufacture. This variety reflects the richness of local traditions and the craftsmanship behind its production. The main objective of the present work was to explore parameters that could impact fungal and bacterial diversity. The microbiome of bacteria and yeasts present in fermentations in the same distillery, in two different years and with three different agave species was investigated by metataxonomic analysis obtained from the sequencing of regions V3-V4 for bacteria and ITS1 for yeasts. The results showed that the dominant fungal genera in the fermentations correspond to non-Saccharomyces yeasts (Hanseniaspora, Pichia and Zygosaccharomyces). A major finding was that Saccharomyces was not the dominant yeast in any of the 15 fermentations characterized. The dominant bacteria belong to the groups of lactic acid bacteria and acetic acid bacteria. The statistical analysis of the alpha and beta diversities shows that the main statistical differences are seen in the year of fermentation rather than in the species of agave used. Finally, the microbial consortium was composed of the same genera during the different fermentations studied; the fundamental difference was the dominant genus in each fermentation.

The opportunistic pathogens Staphylococcus aureus and Pseudomonas aeruginosa are often found together causing persistent infections where they exhibit complex interactions that affect their virulence and resistance to treatment. We sought to clarify how interactions between these organisms affect their resistance to the antimicrobial metal silver (AgNO₃). As previous work showed that cell-free supernatant from P. aeruginosa enhances the resistance of S. aureus, we aimed to identify the exact factor(s) responsible for this increase. Using molecular weight cutoff filters and proteomics, we identified the protein AprA and pyocyanin as the responsible factors. Transposon-mediated disruption of aprA led to the production of supernatant which could not enhance the silver tolerance of S. aureus. These findings suggest that the protease AprA from P. aeruginosa plays an important role in increasing the tolerance of S. aureus to AgNO₃ via in part by mediating the levels of pyocyanin which in turn reduces Ag²⁺ to detoxify it.

Biofilms represent a discrete form of microbial life which are physiologically distinct from free-living planktonic cells. The altered phenotypic manifestations of the biofilm may also elicit lifestyle-dependent adaptive responses to selective pressures. In this work, an experimental evolution model was used to study the adaptation to a biofilm lifestyle in Pseudomonas aeruginosa PA14. The serial passage of biofilms selected for biofilm hyperproduction in a stepwise fashion characterized by increased biomass production and phenotypic diversification was not associated with reduced susceptibility to antibiotics. Adaptation to a biofilm lifestyle selected for mutations causes constitutive increases of intracellular c-di-GMP concentrations via mutations in the phosphodiesterase dipA, the yfiBNR signalling complex and the bifunctional diguanylate cyclase/phosphodiesterase morA. Furthermore, selection for biofilm hyperproduction also gave rise to self-generated diversity by eliciting morphotypic diversification into complex community structures. Individual morphotypes were not associated with specific mutations and lineages dynamically switched between morphotypes despite possessing conserved mechanisms of biofilm hyperproduction. This work provides insights into the evolutionary importance of self-generated diversity to the biofilm and reveals the genetic control and phenotypic dynamics which contribute to the characteristically rugged fitness landscape associated with a sessile lifestyle.

Enterococcus faecalis is a Gram-positive bacterium and opportunistic pathogen that acquires resistance to a wide range of antibiotics by horizontal gene transfer (HGT). The rapid increase of multidrug-resistant (MDR) bacteria including MDR E. faecalis necessitates the development of alternative therapies and a deeper understanding of the factors that impact HGT. CRISPR-Cas systems provide sequence-specific defense against HGT. From previous studies, we know that E. faecalis CRISPR-Cas provides sequence-specific anti-plasmid defense during agar plate biofilm mating and in the murine intestine. Those studies were mainly conducted using laboratory model strains with a single, CRISPR-targeted plasmid in the donor. MDR E. faecalis typically possess multiple plasmids that are diverse in sequence and may interact with each other to impact plasmid transfer and CRISPR-Cas efficacy. Here, we altered multiple parameters of our standard in vitro conjugation assays to assess CRISPR-Cas efficacy, including the number and genotype of plasmids in the donor, and laboratory model strains as donor versus recent human isolates as donor during conjugation. We found that the plasmids pTEF2 and pCF10, which are not targeted by CRISPR-Cas in our recipient, enhance the conjugative transfer of the CRISPR-targeted plasmid pTEF1 into both WT and CRISPR-Cas-deficient (via deletion of cas9) recipient cells. However, the effect of pTEF2 on pTEF1 transfer is much more pronounced, with a striking 6-log increase in pTEF1 conjugation frequency when pTEF2 is also present in the donor and recipients are deficient for CRISPR-Cas (compared with 4-log for pCF10). Overall, this study provides insight about the interplay between plasmids and CRISPR-Cas defence, opening avenues for developing novel therapeutic strategies to curb HGT among bacterial pathogens and highlighting pTEF2 as a plasmid for additional mechanistic study.

Bacteria can gain multiple resistance mechanisms in a single step by the acquisition of multidrug-resistant (MDR) plasmids, but it is unclear how antibiotic selection during the acquisition of MDR plasmids affects the evolution of additional resistance mechanisms. Through conjugating separate extended-spectrum β-lactamase (ESBL)- and carbapenemase-producing MDR plasmids into plasmid-naive Escherichia coli hosts, we examine the effects of acquisition of a single plasmid or co-acquisition of multiple plasmids upon fitness costs, resistance and subsequent genomic adaptation. We show that acquisition of pOXA-48, encoding OXA-48 carbapenemase, is associated with highly variable fitness costs and levels of resistance to ertapenem in transconjugants independent of the presence of pLL35. This phenomenon was not observed during the acquisition of ESBL CTX-M-15-encoding pLL35 alone. Within a single growth cycle, transconjugants receiving pOXA-48 rapidly gained parallel mutations affecting the membrane porin OmpF, or its regulators OmpR or EnvZ. These chromosomal mutations were not compensatory for the fitness costs imposed by the plasmid, nor did they provide significant increases in resistance to carbapenems in the absence of the pOXA-48. Rather, they acted synergistically with the plasmid-encoded carbapenemase, which alone only provided marginal resistance, together providing high-level resistance to ertapenem. Such rapid evolutionary processes may play an important role in plasmid dynamics within environments with strong antibiotic selection for plasmid-encoded antimicrobial resistance genes (ARGs), particularly when these ARGs provide only marginal resistance.

Enterococcus faecalis synthesizes phospholipids from either de novo synthesized or exogenous fatty acids. However, environmental saturated fatty acids are toxic to E. faecalis. The mechanism of toxicity is unknown. We report that saturated acids block growth by efficiently repressing transcription of the fatty acid biosynthesis (fab) genes, resulting in blockage of the synthesis of unsaturated fatty acyl chains. Saturated fatty acid toxicity depends on the chain length of the acyl chains. Growth was restored in the presence of toxic saturated fatty acids by the increased de novo unsaturated fatty acid synthesis, resulting from the deletion of the fabT gene, the repressor that regulates (fab) gene transcription. The addition of unsaturated fatty acids to the medium also restored growth in the presence of toxic saturated fatty acids. Overexpression of AcpA, the fatty acid synthesis acyl carrier protein, also gave increased de novo synthesis of unsaturated fatty acids and restored growth.