Cellular Microbiology最新文献

Klebsiella species are becoming a major global public health concern. In particular, the increase in multidrug-resistant strains is a cause for concern. This study was aimed at determining the antibiotic susceptibility of two different isolates of Klebsiella quasipneumoniae subsp. similipneumoniae and determining the virulence characteristics and bacterial morphology under subminimum inhibitory concentrations (sub-MICs) of antibiotics. In this study, two multidrug-resistant K. quasipneumoniae subsp. similipneumoniae isolates were identified, one of which was clinical, and the other was isolated from freshwater. The MICs of the antibiotics meropenem, chloramphenicol, ciprofloxacin, and kanamycin were determined for these isolates. The effects of the sub-MICs on the virulence and morphological characteristics of the bacteria were investigated in comparison with K. pneumoniae (ATCC 13883). The MICs of meropenem, chloramphenicol, ciprofloxacin, and kanamycin were 0.04, 20, 2, and 8 μg/mL in the clinical isolate; 0.2, 15, 5, and 2 μg/mL in the freshwater isolate; and 0.03, 3, 0.1, and 0.3 μg/mL for K. pneumoniae. The biofilm-forming ability of K. quasipneumoniae subsp. similipneumoniae isolates decreased with antibiotic sub-MICs. Siderophore activity increased only with MIC/4 of kanamycin and MIC/2 of chloramphenicol in the clinical isolate (p > 0.05). Furthermore, bacterial morphology and expression of virulence genes were affected differently by the sub-MICs. This study showed that biofilm formation decreased and that the changes in bacterial morphology and expression of virulence genes were very different in the presence of 1/2 and 1/4 sub-MIC antibiotics.

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disease and the second most frequent cause of jaundice in pregnancy, but the etiology of it is poorly understood. By collecting blood and fecal samples from 12 healthy pregnant women (CON group) and 32 ICP patients (ICP group) in China, we performed 16s rRNA gene sequencing and analyzed microbial diversity. The results showed a decrease in species richness of the ICP group compared to that in the CON group, with a significant difference in species diversity between the two groups. Differential analysis revealed the following biomarkers: s__unclassified__Megamonas, g__Megamonas, f__Selenomonadaceae, c__Bacilli, and o__Lactobacillales. Importantly, we found a decrease in species richness of Selenomonadaceae at the family level and decreased bacilli at the class level in ICP patients. Correlation network analysis and functional gene prediction were performed accordingly. Our data provided new information linking microbiota and ICP, and are possibly helpful for further exploration of the disease.

Pseudomonas aeruginosa, an antibiotic-resistant opportunistic pathogen, poses significant challenges in treating infections, particularly in immunocompromised individuals. This review explores current and future innovative approaches to suppress its growth and virulence. We delve into the bacterium’s virulence factors, discussing existing strategies like antibiotics, bacteriophages, probiotics, and small-molecule inhibitors. Additionally, novel approaches, including RNA interference, CRISPR-Cas systems, and nanotechnology, show promise in preclinical studies. Despite advancements, challenges persist, prompting the need for a multifaceted approach targeting various aspects of P. aeruginosa pathogenesis for effective infection management. This review provides a comprehensive perspective on the status and future directions of innovative strategies against P. aeruginosa.

Objectives: Subinhibitory concentration of antibiotics in the environment is an important risk factor for the horizontal transmission of antibiotic resistance genes (ARGs). The signaling mechanism of resistance gene transmission remains unknown. The aim of this study was to investigate whether indole could be used as a molecular signal to help the spread of ARGs under the stress of subinhibitory concentrations of antibiotics.

Methods: The effect of indole on conjugation frequency was investigated through a conjugation test, and its effect on the Type IV secretion system and pili gene expression of E. coli was observed. Meanwhile, we were investigating the trend of changes in indole regulatory factors ibpA, tnaA, and concentration pumps. Subsequently, we predicted the receptors that specifically bind to indole. Finally, our study focused on elucidating the regulatory mechanism of indole synthesis.

Results: Conjugate frequency was significantly increased under 1/5MIC concentration cefotaxime stress. The transferred ARGs were bla_CTX-M and foxA. The mobile plasmid was IncY or IncI2. Meanwhile, the concentration of endogenous indole was also significantly increased. And, surprisingly, inhibition of endogenous indole production resulted in a significant decrease in conjugate frequency. However, the conjugate frequency increased once again when the strains reacquired the exogenous indole. Furthermore, the fluctuation trends of indole-regulated factor (ibpA, tnaA) mRNA and concentration pumps (acrEF, mtr) mRNA consistently with that of indole. Then, we found that the receptors of indole may be four targets of TCSs: CreC, PhoB, AtoC, and UhpA. More than that, when strains retrieved the exogenous indole again, the mRNA levels of T4SS (virB2, virB6, and virD4) and pppA (coding Pili precursor) genes significantly increased. This indicates that there is a close relationship between indole and conjugated channels, which are necessary for horizontal transfer of genetic material. And then, the trends of indole and tnaA mRNA were consistent with that of ibpA (one of SOS response). So, this result confirmed that indole was regulated by SOS response under subinhibitory concentrations of antibiotics.

Conclusions: It is always known that subinhibitory concentrations of antibiotics stimulate an SOS response in E. coli, which helps in the horizontal spread of ARGs by modulating indole.

Drug repurposing is sparking considerable interest due to reduced costs and development times. The current study details the screening of teniposide, an antitumor drug, for its antibacterial activity against both Gram-positive and Gram-negative strains, with a focus on Staphylococcus epidermidis (S. epidermidis), the primary causative agent of nosocomial and transplant-related infections. The cytotoxicity was evaluated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and hemolysis assays on immortalized human keratinocyte (HaCaT) cells and human erythrocytes. After 20 h of treatment, the recorded concentrations causing 50% cytotoxicity (CC₅₀) and hemolysis (HC₅₀) were 33.63 and 121.55 μg/mL, respectively. The antibacterial screening employed disk diffusion, the broth microdilution method, LIVE/DEAD staining, and a time-killing test. The drug induced a growth inhibitory area in the 22–25 mm range for all Gram-positive strains. The minimum concentration that inhibited 90% of bacteria (MIC₉₀) was 6.25 μg/mL against Staphylococcus aureus and S. epidermidis and 12.5 μg/mL versus Enterococcus faecalis, exhibiting bactericidal action. Treatment resulted in S. epidermidis cell morphology deformities and damage to the cell membrane, observed by scanning electron microscopy (SEM). Mechanism analysis revealed alterations in the selective permeability of the cell membrane, observed under the fluorescence microscope by the absorption of propidium iodide (PI). The synergistic effect of teniposide in combination with fosfomycin and gentamicin was documented by disk diffusion and checkboard assay, recording a fractional inhibitory concentration index (FICI) of 0.28 and 0.37, respectively. The drug’s action on S. epidermidis biofilm biomass was investigated using crystal violet (CV) and MTT. Teniposide affected biofilm viability in a dose-dependent manner, inducing, at a concentration of 3.12 μg/mL, a matrix inhibition of about 42% and 61%, with a sessile metabolic activity of 54% and 24% recorded after 2 and 24 h, respectively. Overall, this study suggests the potential repurposing of the anticancer drug teniposide as a therapeutic agent to counteract S. epidermidis infections.

Tuberculosis (TB) remains a persistent epidemic, and the emergence of drug-resistant Mycobacterium tuberculosis (Mtb) presents a global healthcare threat. While some new agents have been successfully introduced, innovative technologies to evaluate emerging anti-TB compounds are required to inform transformative approaches. Mtb is an obligate human pathogen, and consequently utilizing models that are consistent with human disease is likely to be critical. We have developed a human 3-dimensional (3-D) cell culture model that reflects human disease gene expression patterns and causes Mtb to become pyrazinamide sensitive in vitro. Here, we identify key differences in virulence between the standard laboratory strain, Mtb H37Rv, and clinical isolates. We demonstrate that Mtb H37Rv is attenuated in the 3-D system, more susceptible to antibiotics and hyperinflammatory compared to clinical isolates. Prolonged in vitro culture of a clinical strain leads to attenuation. We then characterise antibiotic sensitivity of multi-drug-resistant Mtb within the 3-D model and define relative bactericidal activity. Finally, we demonstrate that verapamil increases efficacy of bedaquiline and delamanid antibiotic therapy. Taken together, our findings suggest that studying virulent clinical strains in an advanced cell culture system is a powerful adjunct to established methodologies to evaluate new interventions for TB.

Host actin cytoskeleton is often targeted by pathogenic bacteria through the secretion of effectors. Legionella pneumophila virulence relies on the injection of the largest known arsenal of bacterial proteins, over 300 Dot/Icm type 4 secretion system effectors, into the host cytosol. Here, we define the functional interactions between VipA and LegK2, two effectors with antagonistic activities towards actin polymerization that have been proposed to interfere with the endosomal pathway. We confirmed the prominent role of LegK2 effector in Legionella infection, as the deletion of legK2 results in defects in the inhibition of actin polymerization at the Legionella-containing vacuole, as well as in endosomal escape of bacteria and subsequent intracellular replication. More importantly, we observed the restoration of the ΔlegK2 mutant defects, upon deletion of vipA gene, making LegK2/VipA a novel example of effector-effector suppression pair that targets the actin cytoskeleton and whose functional interaction impacts L. pneumophila virulence. We demonstrated that LegK2 and VipA do not modulate each other’s activity in a “metaeffector” relationship. Instead, the antagonistic activities of the LegK2/VipA effector pair would target different substrates, Arp2/3 for LegK2 and G-actin for VipA, to temporally control actin polymerization at the LCV and interfere with phagosome maturation and endosome recycling, thus contributing to the intracellular life cycle of the bacterium. Strikingly, the functional interaction between LegK2 and VipA is consolidated by an evolutionary history that has refined the best effector repertoire for the benefit of L. pneumophila virulence.

Considering natural compounds for the antiviral effect is another opportunity for exploring novel drug candidates for severe acute respiratory syndrome coronavirus 2. The selected natural compounds were interacted using a molecular docking approach. The 3D structures of the main protease and papain-like protease were used for the virtual screening to detect the potent inhibitor against SARS-CoV-2. The top-scored compounds were further analyzed for absorption, digestion, metabolism, excretion, and toxicity properties and density functional theory analysis. Our results indicated that glycyrrhizin exhibited better docking scores of -9.5 kcal/mol with main protease and -9.7 kcal/mol with papain-like protease. Next to glycyrrhizin, rutin showed a better docking score of -9.1 kcal/mol and -9.2 kcal/mol with 3-chymotrypsin-like and papain-like proteases. Violaxanthin and naringin occupied the subsequent position in the docking score table with 3CL and PL proteases, respectively. In addition, the crucial properties like drug likeliness and pharmacokinetics of the compounds were determined. There is no significant toxicity identified.