A Superficial Skin Scarification Method in Mice to Mimic Streptococcus pyogenes Skin Infection in Humans

Disruption of IL-17-mediated immunosurveillance in the respiratory mucosa results in invasive Streptococcus pyogenes infection

Introduction

Streptococcus pyogenes is a Gram-positive pathogen that causes a significant global burden of skin pyoderma and pharyngitis. In some cases, infection can lead to severe invasive streptococcal diseases. Previous studies have shown that IL-17 deficiency in mice (IL-17-/-) can reduce S. pyogenes clearance from the mucosal surfaces. However, the effect of IL-17 on the development of severe invasive streptococcal disease has not yet been assessed.

Methods

Here, we modeled single or repeated non-lethal intranasal (IN) S. pyogenes M1 strain infections in immunocompetent and IL-17-/- mice to assess bacterial colonization following a final IN or skin challenge.

Results

Immunocompetent mice that received a single S. pyogenes infection showed long-lasting immunity to subsequent IN infection, and no bacteria were detected in the lymph nodes or spleens. However, in the absence of IL-17, a single IN infection resulted in dissemination of S. pyogenes to the lymphoid organs, which was accentuated by repeated IN infections. In contrast to what was observed in the respiratory mucosa, skin immunity did not correlate with the systemic levels of IL-17. Instead, it was found to be associated with the activation of germinal center responses and accumulation of neutrophils in the spleen.

Discussion

Our results demonstrated that IL-17 plays a critical role in preventing invasive disease following S. pyogenes infection of the respiratory tract.

In vitro and in vivo antibacterial studies of volatile oil from Atractylodis Rhizoma against Staphylococcus pseudintermedius and multidrug resistant Staphylococcus pseudintermedius strains from canine pyoderma

ETHNOPHARMACOLOGICAL RELEVANCE

Atractylodis Rhizoma is extensively employed in Traditional Chinese Medicine for the treatment of skin and gastrointestinal ailments. Its active components have been proven to demonstrate numerous beneficial properties, including antibacterial, antiviral, anti-inflammatory, anti-tumor, and anti-ulcer activities. Furthermore, the volatile oil from Atractylodis Rhizoma (VOAR) has been reported to effectively inhibit and eradicate pathogens such as Staphylococcus aureus, Escherichia coli and Candida albicans. Of particular concern is Staphylococcus pseudintermedius, the predominant pathogen responsible for canine pyoderma, whose increasing antimicrobial resistance poses a serious public health threat. VOAR merits further investigation regarding its antibacterial potential against Staphylococcus pseudintermedius.

AIM OF THE STUDY

The study aims to verify the in vitro antibacterial activity of VOAR against Staphylococcus pseudintermedius. And a superficial skin infection model in mice was established to assess the in vivo therapeutic effect of VOAR.

MATERIALS AND METHODS

Thirty strains of S. pseudintermedius were isolated from dogs with pyoderma, and the drug resistance was analyzed by disc diffusion method. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of VOAR were determined through the broth dilution method. The growth curve of bacteria in a culture medium containing VOAR was monitored using a UV spectrophotometer. Scanning electron microscopy was employed to observe the effects of VOAR on the microstructure of S. pseudintermedius. The impact of VOAR on the antibiotic resistance of S. pseudintermedius was assessed using the disc diffusion method. Twenty mice were randomly divided into four groups: the control group, the physiological saline group, the VOAR group, and the amikacin group. With the exception of the control group, the skin barrier of mice was disrupted by tap stripping, and the mice were subsequently inoculated with S. pseudintermedius to establish a superficial skin infection model. The modeled mice were treated with normal saline, VOAR, and amikacin for 5 days. Following the treatment period, the therapeutic effect of each group was evaluated based on the measures of body weight, skin symptoms, tissue bacterial load, tissue IL-6 content, and histopathological changes.

RESULTS

The MIC and MBC of VOAR against 30 clinical isolates of S. pseudintermedius were found to be 0.005425% and 0.016875%, respectively. VOAR could exhibit the ability to delay the entry of bacteria into the logarithmic growth phase, disrupt the bacterial structure, and enhance the antibacterial zone in conjunction with antibiotic drugs. In the superficial skin infection model mice, VOAR significantly reduced the scores for skin redness (P < 0.0001), scab formation (P < 0.0001), and wrinkles (P < 0.0001). Moreover, VOAR markedly reduced the bacterial load (P < 0.001) and IL-6 content (P < 0.0001) in the skin tissues of mice. Histopathological observations revealed that the full-layer skin structure in the VOAR group was more complete, with clearer skin layers, and showed significant improvement in inflammatory cell infiltration and fibroblast proliferation compared to other groups.

CONCLUSION

The results demonstrate that VOAR effectively inhibits and eradicates Staphylococcus pseudintermedius in vitro while also enhancing the pathogen's sensitivity to antibiotics. Moreover, VOAR exhibits a pronounced therapeutic effect in the superficial skin infection model mice.

A Glycolipidated-liposomal peptide vaccine confers long-term mucosal protection against Streptococcus pyogenes via IL-17, macrophages and neutrophils

Mucosally active subunit vaccines are an unmet clinical need due to lack of licensed immunostimulants suitable for vaccine antigens. Here, we show that intranasal administration of liposomes incorporating: the Streptococcus pyogenes peptide antigen, J8; diphtheria toxoid as a source of T cell help; and the immunostimulatory glycolipid, 3D(6-acyl) PHAD (PHAD), is able to induce long-lived humoral and cellular immunity. Mice genetically deficient in either mucosal antibodies or total antibodies are protected against S. pyogenes respiratory tract infection. Utilizing IL-17-deficient mice or depleting cellular subsets using antibodies, shows that the cellular responses encompassing, CD4+ T cells, IL-17, macrophages and neutrophils have important functions in vaccine-mediated mucosal immunity. Overall, these data demonstrate the utility of a mucosal vaccine platform to deliver multi-pronged protective responses against a highly virulent pathogen.

Pathogenesis, epidemiology and control of Group A Streptococcus infection

Streptococcus pyogenes (Group A Streptococcus; GAS) is exquisitely adapted to the human host, resulting in asymptomatic infection, pharyngitis, pyoderma, scarlet fever or invasive diseases, with potential for triggering post-infection immune sequelae. GAS deploys a range of virulence determinants to allow colonization, dissemination within the host and transmission, disrupting both innate and adaptive immune responses to infection. Fluctuating global GAS epidemiology is characterized by the emergence of new GAS clones, often associated with the acquisition of new virulence or antimicrobial determinants that are better adapted to the infection niche or averting host immunity. The recent identification of clinical GAS isolates with reduced penicillin sensitivity and increasing macrolide resistance threatens both frontline and penicillin-adjunctive antibiotic treatment. The World Health Organization (WHO) has developed a GAS research and technology road map and has outlined preferred vaccine characteristics, stimulating renewed interest in the development of safe and effective GAS vaccines.