Exogenous methionine contributes to reversing the resistance of Streptococcus suis to macrolides.

Streptococcus suis (S. suis) has been increasingly recognized as a porcine zoonotic pathogen that threatens the health of both pigs and humans. Multidrug-resistant Streptococcus suis is becoming increasingly prevalent, and novel strategies to treat bacterial infections caused by these organisms are desperately needed. In the present study, an untargeted metabolomics analysis showed that the significant decrease in methionine content and the methionine biosynthetic pathway were significantly affected by the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis in drug-resistant S. suis. The addition of L-methionine restored the bactericidal activity of macrolides, doxycycline, and ciprofloxacin on S. suis in vivo and in vitro. Further studies showed that the exogenous addition of methionine affects methionine metabolism by reducing S-adenosylmethionine synthetase activity and the contents of S-adenosylmethionine, S-adenosyl homocysteine, and S-ribose homocysteine. Methionine can decrease the total methylation level and methylesterase activity in multidrug resistant S. suis. The drug transport proteins and efflux pump genes were significantly downregulated in S. suis by exogenous L-methionine. Moreover, the exogenous addition of methionine can reduce the survival of S. suis by affecting oxidative stress and metal starvation in bacteria. Thus, L-methionine may influence the development of resistance in S. suis through methyl metabolism and metal starvation. This study provides a new perspective on the mitigation of drug resistance in S. suis.IMPORTANCEBacterial antibiotic resistance has become a severe threat to human and animal health. Increasing the efficacy of existing antibiotics is a promising strategy against antibiotic resistance. Here, we report that L-methionine enhances the efficacy of macrolides, doxycycline, and ciprofloxacin antibiotics in killing Streptococcus suis, including multidrug-resistant pathogens. We investigated the mechanism of action of exogenous methionine supplementation in restoring macrolides in Streptococcus suis and the role of the methionine cycle pathway on methylation levels, efflux pump genes, oxidative stress, and metal starvation in Streptococcus suis. It provides a theoretical basis for the rational use of macrolides in clinical practice and also identifies a possible target for restoring drug resistance in Streptococcus suis.

New Characterization of Multi-Drug Resistance of Streptococcus suis and Biofilm Formation from Swine in Heilongjiang Province of China.

The aim of this study was to investigate the antimicrobial resistance profiles and genotypes of Streptococcus suis in Heilongjiang Province, China. A total of 29 S. suis were isolated from 332 samples collected from 6 pig farms. The results showed that serotypes 2, 4 and 9 were prevalent, and all the clinical isolates were resistant to at least two antibacterial drugs. The most resisted drugs were macrolides, and the least resisted drugs were fluoroquinolones. Resistant genes ermB and aph (3')-IIIa were highly distributed among the isolates, with the detection rates of 79.31% and 75.86%. The formation of biofilm could be observed in all the isolated S. suis, among which D-1, LL-1 and LL-3 strains formed stronger biofilm structure than other strains. The results indicate that S. suis in Heilongjiang Province presents a multi-drug resistance to commonly used antimicrobial drugs, which was caused by the same target gene, the dissemination of drug resistance genes, and bacterial biofilm.

Rapid Screening of Essential Oils as Substances Which Enhance Antibiotic Activity Using a Modified Well Diffusion Method.

Antimicrobial resistance is recognized as one of the major global health challenges of the 21st century. Synergistic combinations for antimicrobial therapies can be a good strategy for the treatment of multidrug resistant infections. We examined the ability of a group of 29 plant essential oils as substances which enhance the antibiotic activity. We used a modified well diffusion method to establish a high-throughput screening method for easy and rapid identification of high-level enhancement combinations against bacteria. We found that 25 essential oils possessed antibacterial activity against Escherichia Coli ATCC 25922 and methicillin-resistant Staphylococcus aureus (MRSA) 43300 with MICs that ranged from 0.01% to 2.5% v/v. We examined 319 (11 × 29) combinations in a checkerboard assay with E. Coli ATCC 25922 and MRSA 43300, and the result showed that high-level enhancement combinations were 48 and 44, low-level enhancement combinations were 214 and 211, and no effects combinations were 57 and 64, respectively. For further verification we randomly chose six combinations that included orange and Petitgrain essential oils in a standard time-killing assay. The results are in great agreement with those of the well diffusion assays. Therefore, the modified diffusion method was a rapid and effective method to screen high-level enhancement combinations of antibiotics and essential oils.

Albendazole solid dispersions prepared using PEG6000 and Poloxamer188: formulation, characterization and in vivo evaluation.

This study aimed to optimize the preparation process of albendazole (ABZ) solid dispersion (SD) and enhance its dissolution rate and oral bioavailability in dogs. The ABZ-SD formulations were prepared by a fusion method with ABZ and polyethylene glycol 6000 (PEG 6000), poloxamer 188 (P 188) polymers at various weight ratios or the combination of PEG 6000&P 188. The characterizations of the optimal formulations were performed by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), in vitro dissolution test and molecular docking. The in vivo pharmacokinetic study was conducted in beagle dogs. As a result, ABZ solid dispersion based on PEG 6000&P 188 (1:2) was successfully prepared. The ABZ-SD formulation could significantly improve the apparent solubility and dissolution rate of ABZ compared with commercial tablets. Furthermore, the water solubility of ABZ-SD was improved mainly based on hydrogen bond association. Besides, at an oral dosage of 15 mg/kg ABZ, the SDs had higher Cmax values and areas under the curve (AUCs) compared to those of commercial ABZ tablets. Preparation of ABZ-loaded SDs by PEG 6000&P 188 is a promising strategy to improve the oral bioavailability of ABZ.

Germanium Reduces Inflammatory Damage in Mammary Glands During Lipopolysaccharide-Induced Mastitis in Mice.

Ge is a trace element needed for good nutrition and health protection in animals and humans. Ge can be consumed by drinking or eating or administered by injection and transferred with the blood to exert pharmacological activities. The blood is important in the formation of milk. Mastitis is a serious health hazard in animals and humans. The present study explored the effect of Ge on mastitis and the potential underlying mechanism. A mastitis mouse model was established with LPS. mMECs were prepared for study in vitro. Histopathological changes showed that Ge had a protective effect on mammary gland tissues. Ge inhibited MPO activity to reduce inflammatory cell infiltration during mastitis. ELISA and qPCR results for tissues and cells showed that the expression of TNF-α, IL-1ß, and IL-6 was decreased and that of IL-10 was increased by Ge in a dose-dependent manner in mastitis. An analysis of protein phosphorylation was performed with sandwich ELISAs for both tissues and mMECs. The results showed that Ge significantly inhibited the phosphorylation of IκB, NF-κB p65, p38, ERK, and JNK, which was dramatically increased by LPS. These results demonstrate that Ge has an inhibitory effect on inflammation that protects mammary gland tissues by inhibiting NF-κB and MAPK pathway activation and reducing TNF-α, IL-1ß, and IL-6 expression. Ge may be an effective clinical treatment for mastitis and other inflammatory diseases.

The Active Ingredients Identification and Antidiarrheal Mechanism Analysis of Plantago asiatica L. Superfine Powder.

Plantago asiatica L. is a natural medicinal plant that has been widely used for its various pharmacological effects such as antidiarrheal, anti-inflammatory, and wound healing. This study aims to explore the antidiarrheal active ingredients of Plantago asiatica L. that can be used as quality markers to evaluate P. asiatica L. superfine powder (PSP). Molecular docking experiment was performed to identify the effective components of P. asiatica L., which were further evaluated by an established mouse diarrhea model. Na+/K+-ATPase and creatine kinase (CK) activities and the Na+/K+ concentrations were determined. The gene expression of ckb and Atp1b3 was detected. PSP was prepared and evaluated in terms of the tap density and the angle of repose. The structures of PSPs of different sizes were measured by infrared spectra. The active ingredient contents of PSPs were determined by HPLC. The results indicated that the main antidiarrheal components of P. asiatica L. were luteolin and scutellarein that could increase the concentration of Na+ and K+ by upregulating the activity and gene level of CK and Na+/K+-ATPase. In addition, luteolin and scutellarein could also decrease the volume and weight of small intestinal contents to exert antidiarrheal activity. Moreover, as the PSP size decreased from 6.66 to 3.55 µm, the powder tended to be amorphous and homogenized and of good fluidity, the content of active compounds gradually increased, and the main structure of the molecule remained steady. The optimum particle size of PSP with the highest content of active components was 3.55 µm, and the lowest effective dose for antidiarrhea was 2,000 mg/kg. Therefore, the antidiarrheal active ingredients of PSP were identified as luteolin and scutellarein that exert antidiarrheal activity by binding with Na+/K+-ATPase. PSP was successfully prepared and could be used as a new dosage form for the diarrhea treatment.

Synergistic Effect of Pleuromutilins with Other Antimicrobial Agents against Staphylococcus aureus In Vitro and in an Experimental Galleria mellonella Model.

Invasive infections due to Staphylococcus aureus, including methicillin-resistant S. aureus are prevalent and life-threatening. Combinations of antibiotic therapy have been employed in many clinical settings for improving therapeutic efficacy, reducing side effects of drugs, and development of antibiotic resistance. Pleuromutilins have a potential to be developed as a new class of antibiotics for systemic use in humans. In the current study, we investigated the relationship between pleuromutilins, including valnemulin, tiamulin, and retapamulin, and 13 other antibiotics representing different mechanisms of action, against methicillin-susceptible and -resistant S. aureus both in vitro and in an experimental Galleria mellonella model. In vitro synergistic effects were observed in combination of all three study pleuromutilins with tetracycline (TET) by standard checkerboard and/or time-kill assays. In addition, the combination of pleuromutilins with ciprofloxacin or enrofloxacin showed antagonistic effects, while the rest combinations presented indifferent effects. Importantly, all study pleuromutilins in combination with TET significantly enhanced survival rates as compared to the single drug treatment in the G. mellonella model caused by S. aureus strains. Taken together, these results demonstrated synergy effects between pleuromutilins and TET against S. aureus both in vitro and in vivo.