Community-acquired methicillin-resistant Staphylococcus aureus provoked cytokine storm causing severe infection on BALB/c mice

Changing patterns and biological features of community-acquired Clostridioides difficile infection in Southwest China: 7 years of surveillance data

The molecular epidemiological features of community-acquired Clostridioides difficile infection in Southwest China from 7 years of surveillance data were analyzed. Four representative C. difficile strains were selected for RNA-seq, biofilm formation, toxin expression, and cytotoxicity assays. Overall, 5.04% of the C. difficile strains were isolated within 7 years, 85.51% of which were toxigenic C. difficile (both tcdA+/tcdB+). Multilocus sequence typing (ST) and genomic sequencing divided all the isolates into two clusters, namely, clade 1 and clade 4, respectively. ST37 of C. difficile gradually replaced the ST3, ST35, and ST54 genotypes and became the dominant genotype in this area. The antibiotic resistance rate of strains in clade 4 was higher than that in clade 1, especially for the ST37 genotype strains, which were resistant to quinolones. Four C. difficile strains, R20291 (RT027), CD21062 (RT078), CD279 (ST54), and CD413 (ST37), were selected as representative isolates for subsequent biological investigations. RNA-seq revealed that the DEGs of C. difficile ST54 were enriched mainly in ABC transporters, two-component systems, and quorum sensing (QS) pathways and exhibited strong biofilm formation ability. The DEGs of the ST37 genotype strains were mainly enriched in the phosphotransferase system (PTS), ribosome, and some sugar and amino acid metabolism pathways, suggesting that these isolates have increased proliferation and metabolic status. On the other hand, C. difficile R20291 had the highest level of toxin transcription, expression, and cytotoxicity among these four strains. These genotype strains had their own biological characteristics, which provided certain clues for analyzing the causes of these changes.IMPORTANCEThis study carried out a molecular epidemiological investigation of community-acquired C. difficile infection in Southwest China and revealed the characteristics of genotype pattern changes in the strains. C. difficile ST37 gradually replaced the ST3, ST35, and ST54 genotypes to become the dominant strains in this area. Moreover, some representative strains were used to study their biological features. The ST54 strain had strong biofilm formation ability, and ABC transporters, two-component systems, and quorum sensing pathways were enriched according to RNA-seq. The ST37 genotype strain was enriched in the PTS, ribosome, and several sugar and amino acid metabolism pathways. The antibiotic resistance rate of Clade 4 C. difficile was higher than that of clade 1 strains, especially for the resistance of C. difficile ST37 to quinolones. The biological characteristics of these representative strains might provide certain clues for investigating the reasons for these changes.

The Role of PI3k-Gamma Modulation in Bacterial Infection: A Review of the Literature and Selected Experimental Observations

Background: Phosphoinositide 3-kinase is a potent target for cancer therapy due to its significant role in the regulation of cellular growth and proliferation. Dysregulation of the PI3k signaling cascade can constitutively activate growth pathways to trigger the progression of cancer, resulting in the development of multiple inhibitors as cancer therapeutics. Objectives: The wide array of cells expressing PI3k also include immune cells, and the inhibition of these receptors has shown promise in combating inflammation and infectious disease, a relationship we sought to examine further. Methods: We infected wild-type and PI3kγ knockout murine macrophages as well as PI3kγ inhibitor-treated THP-1 human macrophage-like cells with Staphylococcus aureus and quantified inflammation through gene expression analysis, protein secretion assays, and immunofluorescence imaging. Results: We observed that knockout of PI3kγ in murine macrophages alongside pharmacological inhibition through IPI549 treatment in THP-1 cells led to an NF-κB-driven suppression in transcription and release of inflammatory cytokines upon infection with methicillin-resistant Staphylococcus aureus. We were also able to confirm that this suppression of NF-κB translocation and subsequent decrease in inflammatory cytokine release did not compromise and even slightly boosted the bacterial killing ability. Conclusion: PI3k is primarily targeted for cancer therapies, but further exploration can also be carried out on its potential roles in treating bacterial infection.

The Rapidly Changing Patterns in Bacterial Co-Infections Reveal Peaks in Limited Gram Negatives during COVID-19 and Their Sharp Drop Post-Vaccination, Implying Potential Evolution of Co-Protection during Vaccine-Virus-Bacterial Interplay

SARS-CoV-2 has caused the most devastating pandemic of all time in recent human history. However, there is a serious paucity of high-quality data on aggravating factors and mechanisms of co-infection. This study aimed to identify the trending patterns of bacterial co-infections and types and associated outcomes in three phases of the pandemic. Using quality hospital data, we have investigated the SARS-CoV-2 fatality rates, profiles, and types of bacterial co-infections before, during, and after COVID-19 vaccination. Out of 389 isolates used in different aspects, 298 were examined before and during the pandemic (n = 149 before, n = 149 during). In this group, death rates were 32% during compared to only 7.4% before the pandemic with significant association (p-value = 0.000000075). However, the death rate was 34% in co-infected (n = 170) compared to non-co-infected patients (n = 128), indicating a highly significant value (p-value = 0.00000000000088). However, analysis of patients without other serious respiratory problems (n = 28) indicated that among the remaining 270 patients, death occurred in 30% of co-infected patients (n = 150) and only 0.8% of non-co-infected (n = 120) with a high significant p-value = 0.00000000076. The trending patterns of co-infections before, during, and after vaccination showed a significant decline in Staphylococcus aureus with concomitant peaks in Gram negatives n = 149 before/n = 149 during, including Klebsiella pneumonian = 11/49 before/during, E. coli n = 10/24, A. baumannii n = 8/25, Ps. aeruginosa n = 5/16, and S. aureus 13/1. Nevertheless, in the post-vaccination phase (n = 91), gender-specific co-infections were examined for potential differences in susceptibility. Methicillin-resistant S. aureus dominated both genders followed by E. coli in males and females, with the latter gender showing higher rates of isolations in both species. Klebsiella pneumoniae declined to third place in male patients. The drastic decline in K. pneumoniae and Gram negatives post-vaccination strongly implied a potential co-protection in vaccines. Future analysis would gain more insights into molecular mimicry.

Increased susceptibility to pneumonia due to tumour necrosis factor inhibition and prospective immune system rescue via immunotherapy

Immunomodulators such as tumour necrosis factor (TNF) inhibitors are used to treat autoimmune conditions by reducing the magnitude of the innate immune response. Dampened innate responses pose an increased risk of new infections by opportunistic pathogens and reactivation of pre-existing latent infections. The alteration in immune response predisposes to increased severity of infections. TNF inhibitors are used to treat autoimmune conditions such as rheumatoid arthritis, juvenile arthritis, psoriatic arthritis, transplant recipients, and inflammatory bowel disease. The efficacies of immunomodulators are shown to be varied, even among those that target the same pathways. Monoclonal antibody-based TNF inhibitors have been shown to induce stronger immunosuppression when compared to their receptor-based counterparts. The variability in activity also translates to differences in risk for infection, moreover, parallel, or sequential use of immunosuppressive drugs and corticosteroids makes it difficult to accurately attribute the risk of infection to a single immunomodulatory drug. Among recipients of TNF inhibitors, Mycobacterium tuberculosis has been shown to be responsible for 12.5-59% of all infections; Pneumocystis jirovecii has been responsible for 20% of all non-viral infections; and Legionella pneumophila infections occur at 13-21 times the rate of the general population. This review will outline the mechanism of immune modulation caused by TNF inhibitors and how they predispose to infection with a focus on Mycobacterium tuberculosis, Legionella pneumophila, and Pneumocystis jirovecii. This review will then explore and evaluate how other immunomodulators and host-directed treatments influence these infections and the severity of the resulting infection to mitigate or treat TNF inhibitor-associated infections alongside antibiotics.

pH-responsive hierarchical H2S-releasing nano-disinfectant with deep-penetrating and anti-inflammatory properties for synergistically enhanced eradication of bacterial biofilms and wound infection

Background

Methicillin-resistant Staphylococcus aureus (MRSA) biofilm-associated bacterial infection is the primary cause of nosocomial infection and has long been an ongoing threat to public health. MRSA biofilms are often resistant to multiple antimicrobial strategies, mainly due to the existence of a compact protective barrier; thus, protecting themselves from the innate immune system and antibiotic treatment via limited drug penetration.

Results

A hierarchically structured hydrogen sulfide (H₂S)-releasing nano-disinfectant was presented, which was composed of a zinc sulfide (ZnS) core as a H₂S generator and indocyanine green (ICG) as a photosensitizer. This nano-disinfectant (ICG-ZnS NPs) sensitively responded to the biofilm microenvironment and demonstrated efficient eradication of MRSA biofilms via a synergistic effect of Zn²⁺, gas molecule-mediated therapy, and hyperthermia. Physically boosted by released H₂S and a near-infrared spectroscopy-induced hyperthermia effect, ICG-ZnS NPs destroyed the compactness of MRSA biofilms showing remarkable deep-penetration capability. Moreover, on-site generation of H₂S gas adequately ameliorated excessive inflammation, suppressed secretion of inflammatory cytokines, and expedited angiogenesis, therefore markedly accelerating the in vivo healing process of cutaneous wounds infected with MRSA biofilms.

Conclusion

ICG-ZnS NPs combined with NIR laser irradiation exhibited significant anti-biofilm activity in MRSA biofilms, can accelerate the healing process through deep-penetration and anti-inflammatory effectuation. The proposed strategy has great potential as an alternative to antibiotic treatment when combating multidrug-resistant bacterial biofilms.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01262-7.