The ever-changing microenvironment of Staphylococcus aureus in cutaneous infections.

BACKGROUND: Staphylococcus aureus is responsible for the majority of skin and soft tissue infections, which are often diagnosed at a late stage, thereby impacting treatment efficacy. Our study was designed to reveal the physiological changes at different stages of infection by S. aureus through the combined analysis of variations in the skin microenvironment, providing insights for the diagnosis and treatment of S. aureus infections. METHODS: We established a murine model of skin and soft tissue infection with S. aureus as the infectious agent to investigate the differences in the microenvironment at different stages of infection. By combining analysis of the host immune status and histological observations, we elucidate the progression of S. aureus infection in mice. RESULTS: The results indicate that the infection process in mice can be divided into at least two stages: early infection (1-3 days post-infection) and late infection (5-7 days post-infection). During the early stage of infection, notable symptoms such as erythema and abundant exudate at the infection site were observed. Histological examination revealed infiltration of numerous neutrophils and bacterial clusters, accompanied by elevated levels of cytokines (IL-6, IL-10). There was a decrease in microbial alpha diversity within the microenvironment (Shannon, Faith's PD, Chao1, Observed species, Simpson, Pielou's E). In contrast, during the late stage of infection, a reduction or even absence of exudate was observed at the infected site, accompanied by the formation of scabs. Additionally, there was evidence of fibroblast proliferation and neovascularization. The levels of cytokines and microbial composition gradually returned to a healthy state. CONCLUSION: This study reveals synchrony between microbial composition and histological/immunological changes during S. aureus-induced SSTIs.

Geraniol-a potential alternative to antibiotics for bovine mastitis treatment without disturbing the host microbial community or causing drug residues and resistance.

Mastitis is one of the most prevalent diseases of dairy cows. Currently, mastitis treatment in dairy cows is mainly based on antibiotics. However, the use of antibiotics causes adverse effects, including drug resistance, drug residues, host-microbiome destruction, and environmental pollution. The present study sought to investigate the potentiality of geraniol as an alternative to antibiotics for bovine mastitis treatment in dairy cows. Additionally, the effectiveness of treatment, improvement in inflammatory factors, the influence on microbiome, presence of drug residues, and drug resistance induction were compared and analyzed comprehensively.Geraniol showed an equivalent therapeutic rate as antibiotics in the mouse infection model and cows with mastitis. Moreover, geraniol significantly inhibited the pathogenic bacteria and restored the microbial community while increasing the abundance of probiotics in milk. Notably, geraniol did not destroy the gut microbial communities in cows and mice, whereas antibiotics significantly reduced the diversity and destroyed the gut microbial community structure. Additionally, no geraniol residue was detected in milk four days after treatment discontinuation, but, antibiotic residues were detected in milk at the 7th day after drug withdrawal. In vitro experiments revealed that geraniol did not induce drug resistance in the Escherichia coli strain ATCC25922 and Staphylococcus aureus strain ATCC25923 after 150 generations of culturing, while antibiotics induced resistance after 10 generations. These results suggest that geraniol has antibacterial and anti-inflammatory effects similar to antibiotics without affecting the host-microbial community structure or causing drug residues and resistance. Therefore, geraniol can be a potential substitute for antibiotics to treat mastitis or other infectious diseases and be widely used in the dairy industry.

Whole-Genome Sequencing Reveals the High Nosocomial Transmission and Antimicrobial Resistance of Clostridioides difficile in a Single Center in China, a Four-Year Retrospective Study.

Clostridioides difficile, which causes life-threatening diarrheal disease, presents an urgent threat to health care systems. In this study, we present a retrospective genomic and epidemiological analysis of C. difficile in a large teaching hospital. First, we collected 894 nonduplicate fecal samples from patients during a whole year to elucidate the C. difficile molecular epidemiology. We then presented a detailed description of the population structure of C. difficile based on 270 isolates separated between 2015 and 2020 and clarified the genetic and phenotypic features by MIC and whole-genome sequencing. We observed a high carriage rate (19.4%, 173/894) of C. difficile among patients in this hospital. The population structure of C. difficile was diverse with a total of 36 distinct STs assigned. In total, 64.8% (175/270) of the isolates were toxigenic, including four CDT-positive (C. difficile transferase) isolates, and 50.4% (135/268) of the isolates were multidrug-resistant. Statistically, the rates of resistance to erythromycin, moxifloxacin, and rifaximin were higher for nontoxigenic isolates. Although no vancomycin-resistant isolates were detected, the MIC for vancomycin was higher for toxigenic isolates (P < 0.01). The in-hospital transmission was observed, with 43.8% (110/251) of isolates being genetically linked to a prior case. However, no strong correlation was detected between the genetic linkage and epidemiological linkage. Asymptomatic colonized patients play the same role in nosocomial transmission as infected patients, raising the issue of routine screening of C. difficile on admission. This work provides an in-depth description of C. difficile in a hospital setting and paves the way for better surveillance and effective prevention of related diseases in China. IMPORTANCE Clostridioides difficile infections (CDI) are the leading cause of healthcare-associated diarrhea and are known to be resistant to multiple antibiotics. In the past decade, C. difficile has emerged rapidly and has spread globally, causing great concern among American and European countries. However, research on CDI remains limited in China. Here, we characterized the comprehensive spectrum of C. difficile by whole-genome sequencing (WGS) in a Chinese hospital, showing a high detection rate among patients, diverse genome characteristics, a high level of antibiotic resistance, and an unknown nosocomial transmission risk of C. difficile. During the study period, two C. difficile transferase (CDT)-positive isolates belonging to a new multilocus sequence type (ST820) were detected, which have caused serious clinical symptoms. This work describes C. difficile integrally and provides new insight into C. difficile surveillance based on WGS in China.

Dynamic changes of inflammatory response and oxidative stress induced by methicillin-resistant Staphylococcus aureus in mice.

This study is to analyze the dynamic changes of inflammation and oxidative stress in mice infected with MRSA and to provide experimental basis for clinically formulating reasonable treatment plans. We established a model of MRSA infection in mice, detected the fluctuations in the concentration of proinflammatory cytokines and oxidative stress factors with time, and combined with the results of microscopic examination of tissue sections to explain the infection in vivo caused by MRSA. The results showed that on the 1st, 3rd, and 7th day of MRSA infection, the number of leukocytes and eosinophils decreased at first and then increased, monocytes increased continuously, and neutrophils and basophils decreased. At the same time, the levels of proinflammatory cytokines IL-1ß, IL-6, and TNF-α increased. The concentration of glutathione peroxide decreased, and the oxidative metabolites increased. Tissue sections also showed that inflammation and oxidative stress occurred in mice. It is obvious that MRSA infection can lead to significant inflammation and oxidative stress. Therefore, while treating MRSA infection, attention should be paid to the levels of inflammation and oxidative stress in different periods to achieve better treatment effects.

Inflammatory and pathological changes in Escherichia coli infected mice.

Purpose: Understanding the inflammation and histopathological changes in vivo caused by Escherichia coli infection is of great significance for scientific research and clinical diagnosis. Methods: Mice were randomly divided into 6 groups (N = 10) after adaptive feeding, and it challenged by intraperitoneal injection with different concentrations of E. coli ATCC25922. The survival situation within 7 days was recorded, and the half-lethal dose (LD50) was calculated by Karber's method. After the end, the blood, heart, liver, spleen, lung, and kidney of the mice were collected. We detected the concentration of inflammatory cytokines (IL-6, IL-ß, and TNF-α) and inducible nitric oxide synthase (iNOS) in serum by ELSIA. Organs were observed by histopathological staining and electron microscope observation. Results: The LD50 of mice infected with E. coli was 1.371∗106 CFU/kg. The concentrations of IL-6, IL-ß, and TNF-α increased with time after infection in mice, reaching the highest concentration on the 7th day. iNOS was significantly increased on the 1st day of infection, and then decreased over time (P < 0.01). Within a week after infection, the colony counts of the heart, liver, spleen, lung and kidney showed a first decrease, and then reached a surge on the 7th day. Pathological results showed that a small amount of mitochondrial swelling and autophagy were seen in the spleen, lung and kidney tissues of the infected group; and a small amount of secondary lysosomes and autophagy were also seen; but no pathological changes were found in the liver and heart. Conclusion: Escherichia coli can cause inflammation and oxidative stress in mice, causing different degrees of damage to the spleen, lung, and kidney tissues, which provides theoretical support for inflammatory and pathological changes caused by Escherichia coli infection in vivo.

The Inhibitory Efficiencies of Geraniol as an Anti-Inflammatory, Antioxidant, and Antibacterial, Natural Agent Against Methicillin-Resistant Staphylococcus aureus Infection in vivo.

INTRODUCTION: Antibiotics wee widely used as feed additives in animal husbandry. With the increase of drug resistance of bacteria, there is an urgent need to find alternatives to antibiotics. Clinically, methicillin-resistant Staphylococcus aureus (MRSA) infections account for about 25% to 50% of Staphylococcus aureus infections worldwide. Similarly, it is also one of the pathogens that cause serious animal infections. METHODS: We established a mouse model of systemic infection of MRSA to study the preventive effect of geraniol on MRSA and the immunomodulatory effect of geraniol. The mice in the experiment were injected with geraniol by intramuscular injection and were fed intraperitoneally with minimum lethal dose of MRSA. Then, the survival rate, inflammatory cytokines, oxidative stress factors in serum were measured. These values were used to estimate the bacterial load in different organs and to assess histopathological changes in the lungs, liver and kidneys. RESULTS: The above-mentioned two ways of using geraniol could prevent MRSA infection in vivo in mice and showed a significant dose-response relationship. In other words, geraniol significantly decreased the concentrations of inflammatory cytokines and oxidative stress factors in MRSA-infected mice. At the same time, the level of glutathione peroxidase also increased in a dose-proportional relationship. In the group of mice treated with geraniol, their superoxide dismutase levels were significantly higher than those in the vancomycin. After treatment with geraniol, the burden of MRSA decreased. No obvious histopathological abnormalities were found in the liver and kidney of MRSA-infected mice. In addition, geraniol improved the inflammatory changes in the lungs. CONCLUSION: The results indicated that geraniol was a natural substance that could be used as an anti-inflammatory, antioxidant and antibacterial substance to protect mice from MRSA systemic infection. Generally, the research shows that as a natural medicine, geraniol has broad potential in the development and application of antibiotic substitutes.

Assessment of the anti-virulence potential of extracts from four plants used in traditional Chinese medicine against multidrug-resistant pathogens.

BACKGROUND: Multidrug-resistant pathogens are resistant to many antibiotics and associated with serious infections. Amomum tsaoko Crevost et Lemaire, Sanguisorba officinalis, Terminalia chebula Retz and Salvia miltiorrhiza Bge, are all used in Traditional Chinese Medicine (TCM) against multidrug-resistant pathogens, and the purpose of this study was to evaluate the antibacterial and anti-virulence activity of extracts derived from them. METHODS: The antibacterial activity of ethanol and aqueous extracts from these four plants was examined against several multi-drug resistant bacterial strains, and their anti-virulence potential (including quorum quenching activity, biofilm inhibition, and blocking production of virulence factor δ-toxin) was assessed against different S. aureus strains. The chemical composition of the most effective extract was determined by LC-FTMS. RESULTS: Only extracts from S. officinalis and A. tsaoko were shown to exhibit limited growth inhibition activity at a dose of 256 µg·mL-1. The S. officinalis ethanol extract, the ethanol and aqueous extract of A. tsaoko, and the aqueous extract of S. miltiorrhiza all demonstrated quorum quenching activity, but didn't significantly inhibit bacterial growth. The ethanol extract of S. officinalis inhibited bacterial toxin production and biofilm formation at low concentrations. Chemical composition analysis of the most effective extract of S. officinalis showed that it mainly contained saponins. CONCLUSIONS: The most active extract tested in this study was the ethanol root extract of S. officinalis. It inhibited δ-toxin production and biofilm formation at low concentrations and saponins may be its key active components. While the four plants showed no direct antibacterial effects, their anti-virulence properties may be key to fighting bacterial infections.

Effects of infection of MRSA on the expression and activity of renal cytochrome P450s in mice.

Methicillin-resistant Staphylococcus aureus (MRSA) leads to serious infections, but it is not known whether it changes the expression of kidney drug metabolizing enzymes during infection. The mice were infected with different doses of MRSA and the oxidative stress and inflammation levels in the kidney were examined. The mRNA expression and activity of cytochrome P450 enzyme was analysed. Mice infected with high levels of MRSA showed a decrease in renal antioxidant capability and an elevated level of oxidative metabolites, which was accompanied by the release of inflammatory cytokines. The levels of interleukin 1ß, tumour necrosis factor alpha, and macrophage inflammatory protein-1α were significantly increased along with the levels of nitric oxide and malondialdehyde. On day 7, mRNA expression of Cyp1a2, 2d22, and 3a11 were decreased by the high level of MRSA, but the low level of MRSA increased their expressions. Cyp2e1 mRNA expression was increased by MRSA in the kidney of mice. High dose of MRSA infection increased the oxidative stress and inflammatory response in mouse kidney, leading to the decrease in the expression of renal drug-metabolizing enzymes and no recovery within 7 days.

Effect and mechanism of citral against methicillin-resistant Staphylococcus aureus in vivo.

BACKGROUND: Citral is an active component of many plant extracts, and it is a safe additive used in food and cosmetics. A previous study showed that citral has a good antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA) in vitro, but its in vivo anti-infective activity has not been studied. Anti-MRSA activity and the preliminary mechanism of citral against MRSA were investigated in MRSA-infected KM mice. The ED50 was calculated using Karber's method. Groups were selected for inflammatory and oxidative stress level tests, and lung and liver tissues were counterstained with HE for detection of pathological changes. Cytokines and oxidative factors were evaluated using the ELISA method (one-way ANOVA computed using SPSS 19.0.). RESULTS: With the increase in the concentration of citral, the survival rate of MRSA-infected mice increased accordingly. The ED50 values of citral for intramuscular injection and intragastric administration were 0.09 and 0.26 g kg-1 respectively. Citral significantly reduced cytokines (IL-1ß, IL-6, TNF-α) and oxidative factors (malondialdehyde and hydroxyl radicals) of MRSA-infected mice, whereas it increased gluthtione and superoxide dismutase levels. Citral can reduce the lung inflammatory infiltrates infected by MRSA. CONCLUSIONS: Citral exerted a dose-dependent anti-MRSA effect and ameliorated MRSA-induced abnormal changes in inflammation and oxidative stress. This indicates that citral has the potential for development as a new anti-MRSA drug. © 2019 Society of Chemical Industry.

Effect of citral on mouse hepatic cytochrome P450 enzymes.

CONTEXT: Citral is used as a potential natural treatment for various infectious diseases. OBJECTIVE: To examine the effect of citral on the mRNA expression and activities of cytochrome P450 (CYP450) enzymes and establish the relationship between citral-induced liver injury and oxidative stress. MATERIALS AND METHODS: ICR mice were randomly divided into citral (20, 200, and 2000 mg/kglow), Tween-80, and control groups (0.9% saline), 10 mice in each group. The citral-treated groups were intragastrically administered citral for 3 d, control groups treated with 0.5% Tween-80 and 0.9% saline in the same way. Liver injury and CYP450 enzymes were analyzed by analyzing the histopathological changes and the changes of related enzymes. RESULTS: Citral treatment (2000 mg/kg) for 3 d increased serum glutamic pyruvic transaminase and glutamic oxaloacetic transaminase levels, as well as glutathione, gydroxyl radicals, malonaldehyde and total superoxide dismutase contents, but decreased the content of total antioxidant capacity. In doses of 20 and 200 mg/kg groups mice, the contents of NO were decreased significantly and other changes were similar to the 2000 mg/kg group mice, but the liver damage was most severe in the 2000 mg/kg group. Citral induced the mRNA expression and activities of CYP450 1A2, 2D22, and 2E1 in the liver of mice at doses of 20 and 200 mg/kg. There were no changes in testing indexes in Tween-80 treated group mice. Due to its toxic effects, the CYP induction effect of citral negatively correlated with its dose. Although the mRNA expression of CYP450 3A11 was induced by citral, its activity was not affected by low and moderate doses of citral. CYP450 3A11 activity was significantly decreased by high-dose citral. CONCLUSIONS: Citral is hepatotoxic and induced oxidative stress in higher dose, which has a negative effect on CYP450 enzymes. These data suggest caution needs to be taken in order to avoid citral-drug interactions in human beings.

Effect of MRSA on CYP450: dynamic changes of cytokines, oxidative stress, and drug-metabolizing enzymes in mice infected with MRSA.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a very damaging and widespread pathogen, which is associated with many diseases and causes serious infections. MRSA infection can modulate the effects of drugs, which may occur through an influence on cytochrome P450 (CYP450), the drug-metabolizing enzyme in the liver. In this study, we evaluated the underlying mechanism of drug failure or poisoning in MRSA infection. MATERIALS AND METHODS: Mice were infected with three different doses of MRSA and the changes in CYP450 expression, cytokines, and oxidative stress markers were evaluated. RESULTS: The administration of an attack dose of MRSA caused serious symptoms of infection and resulted in a 40% mortality rate in the mice. MRSA induced strong inflammation and oxidative stress in the mice, predominantly caused by significant increases in interleukin (IL)-1ß, IL-4, IL-6, macrophage inflammatory protein, glutathione S-transferase (GST), and malondialdehyde, and decreases in oxygen radical absorbance capacity and glutathione levels in the liver. The expression of IL-2, tumor necrosis factor-α, and GST was briefly suppressed, but increased on days 3 and 7. The increased inflammation and oxidative stress further induced a significant decrease in the mRNA levels and activities of CYP450 1A2, 2D22, 2E1, and 3A1 in MRSA-infected mice within the first day of infection. CONCLUSION: These results show that MRSA infection leads to inflammation and oxidative stress, and reduces the expression levels and activities of drug metabolism enzymes, which decreased drug metabolism in patients infected with MRSA. Therefore, to avoid a drug overdose, the plasma concentration of patients with MRSA infection should be continuously monitored.