Bacterial Virulence Factors and Their Contribution to Pathophysiology after Thermal Injury

Isolation and characterization of bacteriophages targeting methicillin-resistant Staphylococcus aureus (MRSA) from burn patients and sewage water: a genomic and proteomic study

The spectrum of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) ranges from minor conditions to potentially life-threatening diseases. The rising antibiotic resistance in MRSA often leads to treatment failures, underscoring the urgent need for novel eradication strategies. This study focuses on isolating MRSA from burn patients, determining its antibiogram profile, and isolating and characterizing bacteriophages from sewage water that target MRSA, alongside conducting genomic analysis of the phages. A total of 70 samples were collected from burn patients, with MRSA identification and characterization performed using a combination of biochemical and molecular techniques, as well as antibiotic sensitivity testing. Based on host range analysis, a specific phage (phage-3) was selected for detailed characterization, including proteomic analysis, genetic mapping, phylogenetic studies, and analysis of open reading frames (ORFs) and motifs. The prevalence of MRSA in the samples was found to be 28.6%. Antibiotic susceptibility tests indicated that 94% of the MRSA isolates were sensitive to tobramycin and gentamicin, while vancomycin exhibited the lowest sensitivity, with only 2% effectiveness. Using the soft agar overlay method, three bacteriophages (phage-1, phage-2, and phage-3) were successfully isolated from sewage water. Among these, phage-3 exhibited the broadest host range. Further analysis showed that phage-3 demonstrated optimal activity at pH levels between 6 and 8, and within a temperature range of 20-40 °C. Phage-3 also displayed a rapid adsorption phase within the first 0-5 min, and its one-step growth curve revealed a latent period lasting up to 30 min, followed by a significant increase in titer from 30 to 50 min. Proteomic analysis of phage-3 identified the presence of 33 kDa and 65 kDa proteins. Phylogenetic analysis showed that phage-3 shares 96.6% similarity with Mammallicoccus phage vB_MscM-PMS3. The ORF analysis identified 80 potential ORFs within the phage's entire genome.

Farnesol Emulsion as an Effective Broad-Spectrum Agent against ESKAPE Biofilms

The family of ESKAPE pathogens is comprised of Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter. Together they are the main contributors of nosocomial infections and are well established for their ability to "escape" antibiotics. Farnesol is an FDA-approved cosmetic and flavoring agent with significant anti-biofilm properties. In a proprietary emulsion, farnesol has been shown to be capable of disrupting S. aureus, P. aeruginosa, and A. baumannii biofilms. The current work demonstrates that this farnesol emulsion reduces the number of viable bacteria, while also leading to reductions in biomass, of the other three ESKAPE pathogens: Enterococcus faecium, Klebsiella pneumoniae, and Enterobacter, both in vitro and in an ex vivo human skin model. A concentration of 0.5 mg/mL was effective for impeding biofilm development of all three bacteria, while 1 mg/mL for E. faecium and K. pneumoniae, or 0.2 mg/mL for E. cloacae, was able to kill bacteria in established biofilms. Contrary to antibiotics, no resistance to farnesol was observed for E. faecium or K. pneumoniae. The results indicate that farnesol is effective for direct cell killing and also has the ability to induce biofilm detachment from surfaces, as confirmed using Live/Dead image analysis. Our findings confirm that farnesol emulsion is an effective broad-spectrum agent to impede ESKAPE biofilms.

Repurposing Farnesol for Combating Drug-Resistant and Persistent Single and Polymicrobial Biofilms

Biofilm-associated infections caused by drug-resistant and persistent bacteria remain a significant clinical challenge. Here we report that farnesol, commercially available as a cosmetic and flavoring agent, shows significant anti-biofilm properties when dissolved in ethanol using a proprietary formulation emulsion technique. Farnesol in the new formulation inhibits biofilm formation and disrupts established biofilms for Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa, including their polymicrobial biofilms, and, moreover, kills S. aureus persister cells that have developed tolerance to antibiotics. No resistance to farnesol was observed for S. aureus after twenty continuous passages. Farnesol combats biofilms by direct killing, while also facilitating biofilm detachment. Furthermore, farnesol was safe and effective for preventing and treating biofilm-associated infections of both types of bacteria in an ex vivo burned human skin model. These data suggest that farnesol in the new formulation is an effective broad-spectrum anti-biofilm agent with promising clinical potential. Due to its established safety, low-cost, versatility, and excellent efficacy-including ability to reduce persistent and resistant microbial populations-farnesol in the proprietary formulation represents a compelling transformative, translational, and commercial platform for addressing many unsolved clinical challenges.

Distribution patterns and influential factors of pathogenic bacteria in freshwater aquaculture sediments

Pathogenic bacteria, the major causative agents of aquaculture diseases, are a serious impediment to the aquaculture industry. However, the bioinformatics of pathogenic bacteria and virulence factors (VFs) in sediments, an important component of freshwater aquaculture ecosystems, are not well characterized. In this study, 20 sediment samples were collected from fish pond sediments (FPS), shrimp field sediments (SFS), fish pond sediment control (FPSC), and shrimp field sediment control (SFSC). Molecular biological information was obtained on a total of 173 pathogenic bacteria, 1093 virulence factors (VFs), and 8475 mobile genetic elements (MGEs) from these samples. The results indicated that (1) aquaculture patterns and sediment characteristics can affect the distribution of pathogenic bacteria. According to the results of the Kruskal-Wallis H test, except for Mycobacterium gilvum, there were significant differences (P < 0.05) among the four sediment types in the average abundance of major pathogenic bacteria (top 30 in abundance), and the average abundance of major pathogenic bacteria in the four sediment types followed the following pattern: FPS > SFS > FPSC > SFSC. (2) Pathogenic bacteria are able to implement a variety of complex pathogenic mechanisms such as adhesion, invasion, immune evasion, and metabolic regulation in the host because they carry a variety of VFs such as type IV pili, HSI-I, Alginate, Colibactin, and Capsule. According to the primary classification of the Virulence Factor Database (VFDB), the abundance of VFs in all four types of sediments showed the following pattern: offensive VFs > non-specific VFs > defensive VFs > regulation of virulence-related genes. (3) Total organic carbon (TOC), total phosphorus (TP), available phosphorus (AP), nitrite, and nitrate were mostly only weakly positively correlated with the major pathogenic bacteria and could promote the growth of pathogenic bacteria to some extent, whereas ammonia was significantly positively correlated with most of the major pathogenic bacteria and could play an important role in promoting the growth and reproduction of pathogenic bacteria. (4) Meanwhile, there was also a significant positive correlation between CAZyme genes and major pathogenic bacteria (0.62 ≤ R ≤ 0.89, P < 0.05). This suggests that these pathogenic bacteria could be the main carriers of CAZyme genes and, to some extent, gained a higher level of metabolic activity by degrading organic matter in the sediments to maintain their competitive advantage. (5) Worryingly, the results of correlation analyses indicated that MGEs in aquaculture sediments could play an important role in the spread of VFs (R = 0.82, P < 0.01), and in particular, plasmids (R = 0.75, P < 0.01) and integrative and conjugative elements (ICEs, R = 0.65, P < 0.05) could be these major vectors of VFs. The results of this study contribute to a comprehensive understanding of the health of freshwater aquaculture sediments and provide a scientific basis for aquaculture management and conservation.

Screening of Toxin Genes in Methicillin-Resistant Staphylococcus aureus Clinical Isolates from a Hospital Setting in a Tertiary Hospital in Northern Cyprus

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant opportunistic pathogen with a wide repertoire of virulence characteristics. Data regarding the molecular profile of MRSA in Northern Cyprus is limited. The current study aimed to examine the virulence profiles of MRSA with a focus on toxin-associated factors. Ninety-one S. aureus isolates collected at a university hospital were included in the study. Identification and antibiotic susceptibility testing were performed with BD Phoenix™ automated system. Methicillin resistance was evaluated by the disc diffusion assay and mecA detection. The presence of nuc was confirmed by conventional PCR. Confirmed MRSA isolates were assessed for the presence of virulence genes hla, eta, etb, etd and tst using molecular methods. Among 91 S. aureus isolates identified as MRSA using the BD Phoenix™ platform, 80.85% (n = 76/91) were confirmed as MRSA using phenotypic and genotypic methods. All confirmed MRSA isolates (n = 76, 100%) were positive for the nuc. MRSA rates were statistically higher in elderly inpatients. The prevalence of toxin-encoding genes was 97.3% (n = 74/76) for hla, 2.63% (n = 2/76) for eta, 1.3% (n = 1/76) for etb, and 2.63% (n = 2/76) for tst. None of the screened isolates harbored the etd gene. These results represent the first report to investigate multiple virulence factors in MRSA isolates in Northern Cyprus.

Monomicrobial Necrotizing Fasciitis and Sepsis Caused by Pseudomonas aeruginosa and Pseudomonas fluorescens: A Series of Ten Cases

Monomicrobial necrotizing fasciitis caused by Pseudomonas species is a rare infection. The purpose of this study was to elucidate the specific characteristics and clinical outcomes of necrotizing fasciitis caused by Pseudomonas aeruginosa and Pseudomonas fluorescens. Ten patients with monomicrobial necrotizing fasciitis caused by Pseudomonas species were retrospectively reviewed over an 8-year period. Differences in mortality, patient characteristics, clinical presentations, laboratory data, and clinical outcomes were compared between the death and the survival groups. Two patients died with the mortality rate of 20%. Pseudomonas aeruginosa accounted for 9 patients and Pseudomonas fluorescens for one patient. The most common comorbidity is type 2 diabetes mellitus in 5 patients. We found the death patients had lower albumin level and higher counts of band forms of leukocytes than those of the survival patients. Monomicrobial necrotizing fasciitis caused by Pseudomonas species needs emergent surgical intervention and aggressive intensive care due to high mortality rate. We reported the first case of monomicrobial necrotizing fasciitis with Pseudomonas fluorescens. Severe hypoalbuminemia and increased counts of banded leukocytes in initial laboratory presentations can be considered as poor prognostic factors.

Infection and Burn Injury

Burn injury is debilitating and among one of the most frequently occurring traumas. Critical care improvements have allowed for increasingly positive outcomes. However, infection, whether it be localized to the site of the wound or systemic in nature, remains a serious cause of morbidity and mortality. Immune suppression predisposes the burn population to the development of invasive infections; and this along with the possibility of inhalation injury puts them at a significant risk for mortality. Emerging multi-drug-resistant pathogens, including Staphylococcus aureus, Enterococcus, Pseudomonas, Acinetobacter, Enterobacter, and yeast spp., continue to complicate clinical care measures, requiring innovative therapies and antimicrobial treatment. Close monitoring of antimicrobial regimens, strict decontamination procedures, early burn eschar removal, adequate wound closure, proper nutritional maintenance, and management of shock and resuscitation all play a significant role in mitigating infection. Novel antimicrobial therapies such as ultraviolet light, cold plasma and topical antiseptics must continue to evolve in order to lower the burden of infection in burn.

Stimuli-Responsive Nanoplatform-Assisted Photodynamic Therapy Against Bacterial Infections

Bacterial infections are common diseases causing tremendous deaths in clinical settings. It has been a big challenge to human beings because of the antibiotics abuse and the newly emerging microbes. Photodynamic therapy (PDT) is a reactive oxygen species-based therapeutic technique through light-activated photosensitizer (PS). Recent studies have highlighted the potential of PDT as an alternative method of antibacterial treatment for its broad applicability and high efficiency. However, there are some shortcomings due to the low selectivity and specificity of PS. Growing evidence has shown that drug delivery nanoplatforms have unique advantages in enhancing therapeutic efficacy of drugs. Particularly, stimuli-responsive nanoplatforms, as a promising delivery system, provide great opportunities for the effective delivery of PS. In the present mini-review, we briefly introduced the unique microenvironment in bacterial infection tissues and the application of PDT on bacterial infections. Then we review the stimuli-responsive nanoplatforms (including pH-, enzymes-, redox-, magnetic-, and electric-) used in PDT against bacterial infections. Lastly, some perspectives have also been proposed to further promote the future developments of antibacterial PDT.