MSC-Based Cell Therapy in Neurological Diseases: A Concise Review of the Literature in Pre-Clinical and Clinical Research.

Mesenchymal stem cells (MSCs) are multipotent stromal cells with the ability to self-renew and multi-directional differentiation potential. Exogenously administered MSCs can migrate to damaged tissue sites and participate in the repair of damaged tissues. A large number of pre-clinical studies and clinical trials have demonstrated that MSCs have the potential to treat the abnormalities of congenital nervous system and neurodegenerative diseases. Therefore, MSCs hold great promise in the treatment of neurological diseases. Here, we summarize and highlight current progress in the understanding of the underlying mechanisms and strategies of MSC application in neurological diseases.

Matrine reverses the resistance of Haemophilus parasuis to cefaclor by inhibiting the mutations in penicillin-binding protein genes (ftsI and mrcA).

Introduction: Matrine (MT) is a potential resistance reversal agent. However, it remains unclear whether MT can reverse the resistance of Haemophilus parasuis (H. parasuis) to ß-lactams, and, if so, by what mechanism MT works. Methods: We screened one cefaclor (CEC)-resistant strain (clinical strain C7) from eight clinical (H. parasuis) strains and determined the underlying resistance mechanism. Then, we investigated the reversal effect of MTon the resistance of this strain to CEC. Results and Discussion: The production of ß-lactamase, overexpression of AcrAB-TolC system, and formation of biofilm might not be responsible for the resistance of clinical strain C7 to CEC. Fourteen mutation sites were found in four PBP genes (ftsI, pbp1B, mrcA, and prcS) of clinical strain C7, among which the mutation sites located in ftsI (Y103D and L517R) and mrcA (A639V) genes triggered the resistance to CEC. The minimum inhibitory concentration (MIC) of CEC against clinical strain C7 was reduced by two to eight folds after MT treatment, accompanied by the significant down-regulated expression of mutated ftsI and mrcA genes. Based on such results, we believed that MT could reverse the resistance of H. parasuis to CEC by inhibiting the mutations in ftsI and mrcA genes. Our research would provide useful information for restoring the antimicrobial activity of ß-lactams and improving the therapeutic efficacy of Glässer's disease.

Heat stress enhances the occurrence of erythromycin resistance of Enterococcus isolates in mice feces.

Heat stress is a common environmental factor in livestock breeding that has been shown to impact the development of antibiotic resistance within the gut microbiota of both human and animals. However, studies investigating the effect of temperature on antibiotic resistance in Enterococcus isolates remain limited. In this study, specific pathogen free (SPF) mice were divided into a control group maintained at normal temperature and an experimental group subjected to daily 1-h heat stress at 38 °C, respectively. Gene expression analysis was conducted to evaluate the activation of heat shock responsive genes in the liver of mice. Additionally, the antibiotic-resistant profile and antibiotic resistant genes (ARGs) in fecal samples from mice were analyzed. The results showed an upregulation of heat-inducible proteins HSP27, HSP70 and HSP90 following heat stress exposure, indicating successful induction of cellular stress within the mice. Furthermore, heat stress resulted in an increase in the proportion of erythromycin-resistant Enterococcus isolates, escalating from 0 % to 0.23 % over a 30-day duration of heat stress. The resistance of Enterococcus isolates to erythromycin also had a 128-fold increase in minimum inhibitory concentration (MIC) within the heated-stressed group compared to the control group. Additionally, a 2∼8-fold rise in chloramphenicol MIC was observed among these erythromycin-resistant Enterococcus isolates. The acquisition of ermB genes was predominantly responsible for mediating the erythromycin resistance in these Enterococcus isolates. Moreover, the abundance of macrolide, lincosamide and streptogramin (MLS) resistant-related genes in the fecal samples from the heat-stressed group exhibited a significant elevation compared to the control group, primarily driven by changes in bacterial community composition, especially Enterococcaceae and Planococcaceae, and the transfer of mobile genetic elements (MGEs), particularly insertion elements. Collectively, these results highlight the role of environmental heat stress in promoting antibiotic resistance in Enterococcus isolates and partly explain the increasing prevalence of erythromycin-resistant Enterococcus isolates observed among animals in recent years.

Successful spread of mcr-1-bearing IncX4 plasmids is associated with variant in replication protein of IncX4 plasmids.

IncX4 plasmids are one of the most epidemiologically successful vehicles for mcr-1 spread. Here we found that the IncX4 plasmids carried two different replication proteins encoded by genes pir-1 and pir-2, respectively, but mcr-1 was only carried by IncX4 plasmid encoding pir-1. The copy number of pir-2 encoding plasmids (3.15 ± 0.9 copies) are higher than that of pir-1 encoding plasmids (0.85 ± 0.5 copies). When mcr-1 was cloned into IncX4 plasmid encoding pir-2, the higher copy number of these plasmids resulted in increased expression of mcr-1 and a greater fitness burden on their host cells. However, these plasmids exhibited a lower rate of invasion into the bacterial population compared with mcr-1-positive plasmids encoding the pir-1 gene. These findings collectively explain the absence of mcr-1 in all IncX4 plasmids encoding pir-2. Our results further confirmed that low-copy numbers are important for the spread of mcr-1 plasmid from the perspective of natural evolution.

Nitrogen and phosphorus eutrophication enhance biofilm-related drug resistance in Enterococcus faecalis isolated from Water Sources.

Antibiotic resistance is a critical topic worldwide with important consequences for public health. So considering the rising issue of antibiotic-resistance in bacteria, we explored the impact of nitrogen and phosphorus eutrophication on drug resistance mechanisms in Enterococcus faecalis, especially ciprofloxacin, oxytetracycline, and ampicillin. For this purpose we examined the antibiotic-resistance genes and biofilm formation of Enterococcus faecalis under different concentration of nitrogen and phosphorus along with mentioned antibiotics. Mesocosms were designed to evaluate the impact of influence of eutrophication on the underlying mechanism of drugn resistence in Enterococcus faecalis. For this purpose, we explored the potential relation to biofilm formation, adhesion ability, and the expression levels of the regulatory gene fsrA and the downstream gene gelEI. Our results demonstrated that the isolates of all treatments displayed high biofilm forming potential, and fsrA and gelE genes expression. Additionally, the experimental group demonstrated substantially elevated Enterococcus faecalis gelE expression. Crystal violet staining was applied to observe biofilm formation during bacterial development phase and found higher biofilm formation. In conclusion, our data suggest that E. faecalis resistance to ciprofloxacin, oxytetracycline, and ampicillin is related to biofilm development. Also, the high level of resistance in Enterococcus faecalis is linked to the expression of the fsrA and gelE genes. Understanding these pathways is vital in tackling the rising problem of bacterial resistance and its potential effect on human health.

Establishment of a duplex real-time qPCR method for detection of Salmonella spp. and Serratia fonticola in fishmeal.

Salmonella spp. is a high-risk bacterial pathogen that is monitored in imported animal-derived feedstuffs. Serratia fonticola is the bacterial species most frequently confused with Salmonella spp. in traditional identification methods based on biochemical characteristics, which are time-consuming and labor-intensive, and thus unsuitable for daily inspection and quarantine work. In this study, we established a duplex real-time qPCR method with invA- and gyrB-specific primers and probes corresponding to Salmonella spp. and S. fonticola. The method could simultaneously detect both pathogens in imported feedstuffs, with a minimum limit of detection for Salmonella spp. and S. fonticola of 197 copies/µL and 145 copies/µL, respectively (correlation coefficient R2 = 0.999 in both cases). The amplification efficiency for Salmonella spp. and S. fonticola was 98.346% and 96.49%, respectively. Detection of fishmeal was consistent with method GB/T 13091-2018, and all seven artificially contaminated imported feed samples were positively identified. Thus, the developed duplex real-time qPCR assay displays high specificity and sensitivity, and can be used for the rapid and accurate detection of genomic DNA from Salmonella spp. and S. fonticola within hours. This represents a significant improvement in the efficiency of detection of both pathogens in imported feedstuffs.

Eutrophication and Related Antibiotic Resistance of Enterococci in the Minjiang River, China.

Antimicrobial resistance (AMR) in the aquatic environment has received increasing attention in recent years, and growing eutrophication problems may contribute to AMR in aquatic ecosystems. To evaluate whether and how eutrophication affects AMR, 40 surface water samples were collected from the Minjiang River, Fujian Province, China. Total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (CODMn) were measured as eutrophication factors. Additionally, enterococci species were isolated and their resistance to six common antibiotics was tested. Eutrophication generally showed a trend of increasing with the flow direction of the Minjiang River, with 25 sites (62.5%) having a TN/TP value over the Redfield value (16:1), which indicated that eutrophication in this region was of phosphorus limitation. High nutrition sites were in or near urban areas. Poor quality water was found in the middle and lower reaches of the Minjiang River system. The resistance frequency of 40 enterococci isolates to the six antibiotics tested was as follows: oxytetracycline > erythromycin > ciprofloxacin > chloramphenicol > ampicillin > vancomycin (70, 50, 17.5, 12.5, 2.5, 0%), and the multi-resistant rate reached 50% with eight resistance phenotypes. AMR also increased along the direction of water flow downstream, and most of the sites with the highest AMR were in or near urban areas, as was true for nutrition levels. Positive correlations between AMR and eutrophication factors (TN, TP, and CODMn) were identified using the Pearson's correlation coefficient, and TN/TP generally was negatively related to AMR. These results indicated that eutrophication may induce or selective for resistance of water-borne pathogens to antibiotics, with a high resistance level and a wide resistance spectrum.

Inhibitory Effect of Two Traditional Chinese Medicine Monomers, Berberine and Matrine, on the Quorum Sensing System of Antimicrobial-Resistant Escherichia coli.

The quorum sensing (QS) system controls bacterial biofilm formation, which is highly related to the virulence and resistance of pathogens. In the present study, the effect of two traditional Chinese medicine (TCM) monomers, berberine and matrine, on biofilm formation and QS-related gene expression of antimicrobial-resistant (AMR) Escherichia coli strains was investigated by laser scanning confocal microscopy (LSCM) observation and real-time PCR. The results indicated a roughly positive relationship between biofilm formation ability and antimicrobial resistance. LSCM observation showed that berberine and matrine inhibited biofilm formation of AMR E. coli strains at 1/2 minimal inhibitory concentration (MIC) (1/2 MIC berberine at OD630: 0.1020; 1/2 MIC matrine: OD630: 0.1045); furthermore, abnormal cell morphology such as rounded and elongated cells was also observed. This finding was consistent with the downregulation of QS-related genes: luxS, pfS, sdiA, hflX, motA, and fliA. At 1/2 MIC and 1/4 MIC concentrations of berberine, a significant downregulation of luxS, pfS, hflX, ftsQ, and ftsE was observed. The results indicate that berberine and matrine can inhibit biofilm formation by inhibiting the QS system and that berberine is more effective than matrine.

PK/PD modeling of Ceftiofur Sodium against Haemophilus parasuis infection in pigs.

BACKGROUND: Ceftiofur Sodium is widely used in China. Our aim was to determine Ceftiofur Sodium activity and optimize dosing regimens against the pathogen Haemophilus parasuis using an in vitro and ex vivo pharmacokinetics/pharmacodynamics modeling approach. By adopting these strategies, we wanted to extend the effective life of Ceftiofur Sodium in reduce drug-resistance in pigs. RESULTS: We established an H. parasuis infection model in pigs, and assessed the pharmacokinetics of Ceftiofur Sodium in both healthy and infected animals. After Ceftiofur Sodium (10 mg/kg, i.m.) administration to healthy and H. parasuis-infected pigs, plasma based desfuroylceftiofur (a metabolite of Ceftiofur Sodium) was measured by High Performance Liquid Chromatography. The pharmacokinetics of Ceftiofur Sodium (desfuroylceftiofur) was consistent with a two-compartment open model, with first-order absorption. We observed no significant differences (P > 0.05) in pharmacokinetic parameters between healthy and infected pigs. Pharmacodynamics data showed that Ceftiofur Sodium was highly inhibitory against H. parasuis, with MIC, MBC, and MPC values of 0.003125, 0.0125 and 0.032 µg/mL, respectively. Desfuroylceftiofur in plasma also had strong bactericidal activity. Almost all H. parasuis cultured in plasma medium of Ceftiofur Sodium-inoculated healthy pigs, at each time point, were killed within 24 h. A weaker antibacterial activity was measured in infected-pig plasma medium at 18, 24, 36, and 48 h, after Ceftiofur Sodium inoculation. Pharmacokinetic parameters were combined with ex vivo pharmacodynamic parameters, and the bacteriostatic effect (36.006 h), bactericidal effect (71.637 h) and clearance (90.619 h) within 24 h, were determined using the Hill equation. Dose-calculation equations revealed the optimal dose of Ceftiofur Sodium to be 0.599-1.507 mg/kg. CONCLUSIONS: There were no significant differences in Ceftiofur Sodium pharmacokinetic parameters between healthy and infected pigs, although pharmacokinetics/pharmacodynamics fitting curves showed obviously differences. The optimal dose of Ceftiofur Sodium was lower than recommended (3 mg/kg), which may provide improved treatments for Glässers disease, with lower drug-resistance possibility.

Biofilm Formation Plays a Role in the Formation of Multidrug-Resistant Escherichia coli Toward Nutrients in Microcosm Experiments.

In this study, microcosms were established to determine the effect of nitrogen (N) and phosphorus (P) on the multidrug resistance and biofilm-forming abilities of Escherichia coli. The expression of biofilm-formation-related genes was detected to establish correlations between genotype and phenotype. Different concentrations of N and P were added to make one control group and four treatment groups. The glass tube method was used to determine biofilm-forming capabilities. Real-time PCR was used to detect the mRNA abundance of six biofilm-formation-related genes in E. coli. No resistant strains were isolated from the control group; meanwhile, multidrug resistance rates were high in the treatment groups. Expression of the biofilm-associated genes luxS, flhD, fliA, motA, and fimH was detected in all treatment groups; however, there was no expression of mqsR. The expression of luxS, flhD, fliA, motA, and fimH significantly correlated with the concentration of N and P, as well as with the appearance and duration of multidrug resistance in different groups. Overall, the results of this study suggest that biofilm-forming ability plays a key role in the formation of multidrug resistance in E. coli after the addition of N and P to a microcosm.

Molecular Mechanism of Quorum-Sensing in Enterococcus faecalis: Its Role in Virulence and Therapeutic Approaches.

Quorum-sensing systems control major virulence determinants in Enterococcusfaecalis, which causes nosocomial infections. The E. faecalis quorum-sensing systems include several virulence factors that are regulated by the cytolysin operon, which encodes the cytolysin toxin. In addition, the E. faecalis Fsr regulator system controls the expression of gelatinase, serine protease, and enterocin O16. The cytolysin and Fsr virulence factor systems are linked to enterococcal diseases that affect the health of humans and other host models. Therefore, there is substantial interest in understanding and targeting these regulatory pathways to develop novel therapies for enterococcal infection control. Quorum-sensing inhibitors could be potential therapeutic agents for attenuating the pathogenic effects of E. faecalis. Here, we discuss the regulation of cytolysin, the LuxS system, and the Fsr system, their role in E. faecalis-mediated infections, and possible therapeutic approaches to prevent E. faecalis infection.

Nutrient-induced antibiotic resistance in Enterococcus faecalis in the eutrophic environment.

Nutrient deposition and extensive use of antibiotics are increasing worldwide, especially in freshwater ecosystems. Bacteria display resistance to certain antibiotics and thus survive for extended periods in eutrophic environments. In this study, model ecosystems were established to investigate the effect of nitrate and phosphate nutrient salts on antibiotic resistance in strains of Enterococcus faecalis. Mesocosms were replicated to evaluate the ecological effects of nutrient influx. The mesocosms were divided into four different nitrogen (N) and phosphorus (P) regimens. Enterococcus faecalis strains were isolated on Days 0, 1, 7, 14, 21, 28, 40, 60 and 95 to evaluate their sensitivity to ampicillin, oxytetracycline (OXY), ciprofloxacin (CIP), chloramphenicol (CHL), vancomycin and erythromycin (ERY). Resistance genes for ERY (ermB, msrC and mefA), OXY [tet(M), tet(L) and tet(S)] and CHL (cat) as well as the enterococcal surface protein gene (esp) were investigated by PCR. The total nitrogen, total phosphorus, chemical oxygen demand permanganate index (CODMn), chlorophyll-a, Secchi depth and trophic level index were observed. In conclusion, addition of N and P had a significant influence on the resistance phenotypes of E. faecalis to OXY, CHL and ERY. Only high dosage led to CIP resistance. Higher total N concentrations resulted in the development of relatively higher resistance to OXY and CIP. The resistance genes tet(L) and tet(S) for OXY, msrC for ERY and cat for CHL were found to be associated with resistance in E. faecalis.

Complete genome sequence of a lineage I peste des petits ruminants virus isolated in 1969 in west Africa.

We report the complete genome sequence of a lineage I peste des petits ruminants virus (E32/1969) isolated in a Senegalese laboratory in 1969. This is the earliest peste des petits ruminants virus of any lineage sequenced to date and only the second lineage I virus available in public databases.

WITHDRAWN: Identification of peste-des-petits ruminants virus (PPRV) lineage IV, the Asian lineage, in Nigeria and co-circulation with PPRV lineage II.

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Cornmeal-induced resistance to ciprofloxacin and erythromycin in enterococci.

OBJECTIVE: To establish a model ecosystem to study the impact of cornmeal on the appearance and persistence of the erythromycin (ERY)- and ciprofloxacin (CIP)-resistant phenotypes in waterborne enterococci. METHODS: After the model ecosystem was established, the system was divided into six dose groups, with the addition of 8, 4, 1, 0.25, 0.05, and 0 g L(-1) sterilized cornmeal. System mud samples were collected at 0, 1, 3, 7, 14, 30, 40, 61, and 130 d, and enterococci present in the mud samples were evaluated for their sensitivities to CIP and ERY. PCR was employed to detect genes such as gyrA and ermB. The gyrA gene was sequenced, and codons 83 and 87 were analyzed for mutations. RESULTS: (1) The addition of 0.05-8 g L(-1) cornmeal had an impact on CIP resistance. The higher the dose of cornmeal added, the larger the impact it generated. Furthermore, the earlier the emergence of CIP-resistant strains, the greater the incidence of drug resistance. The impact of cornmeal on resistance to ERY was less consistent, and the degree of the impact was not in proportion to the dose of cornmeal added. (2) There were no mutations at codons 83 and 87 in the gyrA genes from 102 strains isolated from the model ecosystem. The incidence of ermB-positive strains of ERY-resistant enterococci (28 strains) was 78.6%, and the incidence of ermB-positive strains of ERY-sensitive enterococci (16 strains) was 0%. CONCLUSIONS: (1) Adding different doses of cornmeal can facilitate resistance to CIP and ERY in waterborne enterococci. In this study, the degree of resistance was related to the cornmeal dose. (2) In the model ecosystem, enterococcal CIP resistance was not caused by a gyrA gene mutation; however, in the vast majority of cases, resistance to ERY was related to the ermB resistance gene.

Effects of administration mode of antibiotics on antibiotic resistance of Enterococcus faecalis in aquatic ecosystems.

In this study we investigated the effects of antibiotic administration mode on development of antibiotic resistance in a freshwater model ecosystem. Mesocosms were established in 2.25 m(3) cement pools containing tap water and yellow soil free of antibiotic contamination. Oxytetracycline (5 mg L(-1)) and ciprofloxacin (2 mg L(-1)) were used as experimental antibiotics and Enterococcus faecalis was used as indicator bacteria. Antibiotics were either administered directly to the pools, or were administered in a feed-antibiotic mixture or feces-antibiotic mixture. Surface sediment samples were collected and analyzed at 0, 3, 7, 14, 21, 30, 60 and 120 d after inoculation. E. faecalis was isolated and identified by polymerase chain reaction (PCR) and a drug sensitivity test was performed using the micro-broth-dilution method. Maximum antibiotic resistance was reached on day 3 with all methods of administration. The effect was significantly higher in the feed-administration group compared with the direct administration and feces-administration groups, and between the latter two groups the effect appeared to be slightly higher in the direct administration group. The minimum inhibitory concentration (MIC) values showed bacterial resistance percent decreased in a time-dependent manner in all groups; however, the decreasing trend was less dramatic in bacteria isolated from the feed-antibiotics group. Overall, the percent and level of resistance to oxytetracycline was higher than to ciprofloxacin, and the sensitivity recovery time was longer for bacteria exposed to oxytetracycline than to ciprofloxacin. Our findings suggest that antibiotics introduced to water via feed can induce high percent of antibiotic-resistant bacteria in aquatic ecosystems.