The Key Element Role of Metallophores in the Pathogenicity and Virulence of Staphylococcus aureus: A Review

Multi-targets of antimicrobial photodynamic therapy mediated by erythrosine against Staphylococcus aureus identified by proteomic approach

Staphylococcus aureus is a global challenge to the clinical field and food industry. Therefore, the development of antimicrobial photodynamic therapy (aPDT) has become one of the valuable methods to control this pathogen. The antibacterial activity of photoinactivation by erythrosine (Ery) against S. aureus has been reported, but its modes of action are unclear. This study aimed to employ a proteomic approach to analyze modes of action of Ery-aPDT against S. aureus. We determined the antibacterial effect by Ery-aPDT assays, quantified reactive oxygen species (ROS) and injury to the cell membrane, and determined protein expression using a proteomic approach combined with bioinformatic tools. Ery-aPDT was effective in reducing S. aureus to undetectable levels. In addition, the increment of ROS accompanied the increase in the reduction of cell viability, and damage to cellular membranes was shown by sublethal injury. In proteomic analysis, we found 17 differentially expressed proteins. These proteins revealed changes mainly associated with defense to oxidative stress, energy metabolism, translation, and protein biosynthesis. Thus, these results suggest that the effectiveness of Ery-aPDT is due to multi-targets in the bacterial cell that cause the death of S. aureus.

Overview of Proteus mirabilis pathogenicity and virulence. Insights into the role of metals

Proteus mirabilis is a Gram-negative bacterium with exclusive molecular and biological features. It is a versatile pathogen acclaimed for its distinct urease production, swarming behavior, and rapid multicellular activity. Clinically, P. mirabilis is a frequent pathogen of the human urinary system where it causes urinary tract infections (UTIs) and catheter-associated urinary tract infections (CAUTIs). This review explores the epidemiology, risk factors, clinical manifestations, and treatment of P. mirabilis infections, emphasizing its association with UTIs. The bacterium's genome analysis revealed the presence of resistance genes against commonly used antibiotics, an antibiotic-resistant phenotype that poses a serious clinical challenge. Particularly, the emergence of extended-spectrum β-lactamases (ESBLs) and carbapenemases resistant P. mirabilis strains. On a molecular level, P. mirabilis possesses a wide array of virulence factors including the production of fimbriae, urease, hemolysins, metallophores, and biofilm formation. This review thoroughly tackles a substantial gap in understanding the role of metallophores in shaping the virulence factors of P. mirabilis virulence. Siderophores, iron metal chelating and transporting metallophores, particularly contribute to the complex pathogenic strategies, displaying a potential target for therapeutic intervention.

General Overview of Klebsiella pneumonia: Epidemiology and the Role of Siderophores in Its Pathogenicity

The opportunistic pathogen Klebsiella pneumoniae (K. pneumoniae) can colonize mucosal surfaces and spread from mucosae to other tissues, causing fatal infections. Medical equipment and the healthcare setting can become colonized by Klebsiella species, which are widely distributed in nature and can be found in water, soil, and animals. Moreover, a substantial number of community-acquired illnesses are also caused by this organism worldwide. These infections are characterized by a high rate of morbidity and mortality as well as the capacity to spread metastatically. Hypervirulent Klebsiella strains are thought to be connected to these infections. Four components are critical to this bacterium's pathogenicity-the capsule, lipopolysaccharide, fimbriae, and siderophores. Siderophores are secondary metabolites that allow iron to sequester from the surrounding medium and transport it to the intracellular compartment of the bacteria. A number of variables may lead to K. pneumoniae colonization in a specific area. Risk factors for infection include local healthcare practices, antibiotic use and misuse, infection control procedures, nutrition, gender, and age.

Editorial for the Special Issue, 'Secondary Metabolites from Microorganisms or Microorganism-Host Interaction?'

In this Special Issue, there are 13 published papers from over 10 countries [...].

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus among Patients Diagnosed with Surgical Site Infection at Four Hospitals in Ethiopia

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of severe surgical site infections (SSI). The molecular epidemiology of MRSA is poorly documented in Ethiopia. This study is designed to determine the prevalence of MRSA and associated factors among patients diagnosed with SSI. A multicenter study was conducted at four hospitals in Ethiopia. A wound culture was performed among 752 SSI patients. This study isolated S. aureus and identified MRSA using standard bacteriology, Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), and cefoxitin disk diffusion test. The genes mecA, femA, vanA, and vanB were detected through PCR tests. S. aureus was identified in 21.6% of participants, with 24.5% of these being methicillin-resistant Staphylococci and 0.6% showing vancomycin resistance. Using MALDI-TOF MS for the 40 methicillin-resistant Staphylococci, we confirmed that 31 (77.5%) were S. aureus, 6 (15%) were Mammaliicoccus sciuri, and the other 3 (2.5%) were Staphylococcus warneri, Staphylococcus epidermidis, and Staphylococcus haemolyticus. The gene mecA was detected from 27.5% (11/40) of Staphylococci through PCR. Only 36.4% (4/11) were detected in S. aureus, and no vanA or vanB genes were identified. Out of 11 mecA-gene-positive Staphylococci, 8 (72.7%) were detected in Debre Tabor Comprehensive Specialized Hospital. Methicillin-resistant staphylococcal infections were associated with the following risk factors: age ≥ 61 years, prolonged duration of hospital stay, and history of previous antibiotic use, p-values < 0.05. Hospitals should strengthen infection prevention and control strategies and start antimicrobial stewardship programs.

Cadmium-chelating ability of the siderophore DHBS secreted by Leclercia adecarboxylata FCH-CR2 and its action mechanism

As one of the most accumulative toxic heavy metals, cadmium (Cd) poses a major threat to human health. Bacterial siderophores, as small molecules with metal-absorbing ability, have great potential activity for Cd-reduction. In this study, the siderophore-producing bacterialstrain FCH-CR2 was isolated from a high-Cd contaminated soil using the CAS method. Leclercia adecarboxylata was identified through 16S rRNA sequence, homology analysis, colony morphology, physiological and biochemical tests. A siderophore, catechol type 2,3-dihydroxy-N-benzoyl-l-serine (DHBS) secreted by FCH-CR2, was purified using RP-HPLC and identified by LC-MS/MS. Intraperitoneal injection of DHBS significantly increased fecal Cd levels, and reduced Cd accumulation in organs. In density flooding theory (DFT) analysis, DHBS may bind to Cd via the hydroxyl site on the benzene ring. Besides, the isothermal titration calorimetry (ITC) assay revealed that the formation of Cd-DHBS is a spontaneous and endothermic reaction with ΔG = -21.4 kJ/mol and ΔH = 1.51 ± 0.142 kJ/mol.

Microbial interaction-induced siderophore dynamics lead to phenotypic differentiation of Staphylococcus aureus

This study investigated the impact of microbial interactions on siderophore dynamics and phenotypic differentiation of Staphylococcus aureus under iron-deficient conditions. Optimization of media demonstrated that the glycerol alanine salts medium was best suited for analyzing the dynamics of siderophore production because of its stable production of diverse siderophore types. The effects of pH and iron concentration on siderophore yield revealed a maximum yield at neutral pH and low iron concentration (10 µg). Microbial interaction studies have highlighted variations in siderophore production when different strains (Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli) are co-cultured with S. aureus. Co-culture of S. aureus with P. aeruginosa eliminated siderophore production in S. aureus, while co-culture of S. aureus with E. coli and S. epidermidis produced one or two siderophores, respectively. Raman spectroscopy revealed that microbial interactions and siderophore dynamics play a crucial role in directing the phenotypic differentiation of S. aureus, especially under iron-deficient conditions. Our results suggest that microbial interactions profoundly influence siderophore dynamics and phenotypic differentiation and that the study of these interactions could provide valuable insights for understanding microbial survival strategies in iron-limited environments.

Structural Study of a New MbtI-Inhibitor Complex: Towards an Optimized Model for Structure-Based Drug Discovery

MbtI from Mycobacterium tuberculosis (Mtb) is a Mg2+-dependent salicylate synthase, belonging to the chorismate-utilizing enzyme (CUE) family. As a fundamental player in iron acquisition, MbtI promotes the survival and pathogenicity of Mtb in the infected host. Hence, it has emerged in the last decade as an innovative, potential target for the anti-virulence therapy of tuberculosis. In this context, 5-phenylfuran-2-carboxylic acids have been identified as potent MbtI inhibitors. The first co-crystal structure of MbtI in complex with a member of this class was described in 2020, showing the enzyme adopting an open configuration. Due to the high mobility of the loop adjacent to the binding pocket, large portions of the amino acid chain were not defined in the electron density map, hindering computational efforts aimed at structure-driven ligand optimization. Herein, we report a new, high-resolution co-crystal structure of MbtI with a furan-based derivative, in which the closed configuration of the enzyme allowed tracing the entirety of the active site pocket in the presence of the bound inhibitor. Moreover, we describe a new crystal structure of MbtI in open conformation and in complex with the known inhibitor methyl-AMT, suggesting that in vitro potency is not related to the observed enzyme conformation. These findings will prove fundamental to enhance the potency of this series via rational structure-based drug-design approaches.

Cytoplasmic amino acid profiles of clinical and ATCC 29213 strains of Staphylococcus aureus harvested at different growth phases

Staphylococcus aureus strains are a great contributor to both hospital acquired infections as well as community acquired infections. The objective of the present investigation was to compare potential differences in cytoplasmic amino acid levels between clinical and ATCC 29213 strains of S. aureus. The two strains were grown under ideal conditions to mid-exponential and stationary growth phases, after which they were harvested to analyze their amino acid profiles. Initially, the amino acid patterns of both strains were compared at the mid-exponential phase when grown in controlled conditions. At the mid-exponential phase, both strains shared common features in cytoplasmic amino acid levels, with glutamic acid, aspartic acid, proline, and alanine identified as key amino acids. However, the concentration profiles of seven amino acids exhibited major variances between the strains, even though the total cytoplasmic levels of amino acids did not alter significantly. At the stationary phase, the magnitudes of the amino acids abundant in the mid-exponential phase were altered. Aspartic acid became the most abundant amino acid in both strains accounting for 44% and 59% of the total amino acids in the clinical and ATCC 29213 strains, respectively. Lysine was the second most abundant amino acid in both strains, accounting for 16% of the total cytoplasmic amino acids, followed by glutamic acid, the concentration of which was significantly higher in the clinical strain than in the ATCC 29213 strain. Interestingly, histidine was clearly present in the clinical strain but was virtually lacking in the ATCC 29213 strain. This study reveals the dynamic diversity of amino acid levels among strains, which is an essential step toward illustrating the variability in S. aureus cytoplasmic amino acid profiles and could be significant in explaining variances among strains of S. aureus.

Bibliometric Review on New Possibilities of Antimycobacterial Agents: Exploring Siderophore Desferrioxamine's Applications as an Antimicrobial Agent

Mycobacteria cause tuberculosis and other serious diseases. Understanding their mechanisms of resistance to our immune system and exploring novel drugs are critical strategies to combat infections. A bibliometric analysis was performed to identify publication trends and critical research areas in the field of the antimicrobial activity of desferrioxamine. A total of twenty-four publications on the topic, from 2012 to 2023, were retrieved from databases including Web of Science, Scopus, PubMed, and Embase, using specific keywords. The quality of the publications was assessed using impact and productivity metrics, with an average annual publication rate of 2.1 articles. The United States emerged as the most productive country, with medicine (23.4%, 11 publications) and biochemistry, genetics, and molecular biology (21.3%, 10 publications) as the top research fields. The five most cited publications accounted for 672 citations, with a relatively low h-index (11:11). In conclusion, there has been a lack of publications on this topic in the last decade. The United States dominates production and publication in this area, and there appears to be limited exchange of knowledge, ideas, and technology within the field. Therefore, fostering international cooperation through funding is essential to facilitate further research and development of desferrioxamine-related studies.

Towards new antibiotics classes targeting bacterial metallophores

The increasing bacterial resistance caused by antibiotic overuse has promoted the search for new antimicrobial strategies. Metals uptake via bacterial metallophores are studied to develop new therapeutics against infectious diseases, because metal ions are essential for bacterial growth and virulence. Metal ions assimilation is mainly dependent on metallophores production which are metal chelators synthetized and produced by bacteria to facilitate metals uptake and are vital for bacterial pathogenicity. Here we highlight the perspective for antimicrobial and therapeutic potential of metallophores through several approaches for metallophores application in antimicrobial therapy.

Hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKP), especially multidrug-resistant hvKP (MDR-hvKP) infections, are distributed globally, and lead to several outbreaks with high pathogenicity and mortality in immunocompetent individuals. This is usually characterized by a rapidly metastatic spread resulting in multiple pyogenic tissue abscesses. To date, even though the explanation of hypervirulent factors of hvKP has been identified, it still remains to be fully understood. The most common key virulence agents of hvKP included (1) siderophore systems for iron acquisition, (2) increased capsule production, (3) the colibactin toxin, (4) hypermucoviscosity, and so on. Several hypervirulence factors have been renewed, and the evolution of MDR-hvKP has been deeply explored recently. We aim to describe a chain of key virulence agents attributed to the lethality of hvKP and MDR-hvKP. In this review, recent advances in renewed factors in hypervirulence were summarized, and potential therapeutic targets are explored. Novel co-existence of hypervirulence agents and multidrug-resistant elements, even the superplasmid, was screened. Superplasmid simultaneously harbours hypervirulence and multidrug-resistant genes and can mobile autonomously by its complete conjugative elements. Research into related immunity has also gained traction, which may cause multiple invasive infections with higher mortality rates than classical ones, such as neutrophil- and complement-mediated activity. The evolution of virulence and multidrug resistance is accelerating. More reliable methods for identifying hvKP or MDR-hvKP must be investigated. Furthermore, it is critical to investigate innovative treatment targets in the future.

Water Quality Index and Human Health Risk Assessment of Drinking Water in Selected Urban Areas of a Mega City

The present study was conducted to evaluate the quality of drinking water and assess the potential health hazards due to water contaminants in selected urban areas of Lahore, Pakistan. Water samples were collected from ten sites and analyzed for different physico-chemical parameters including turbidity, color, pH, total dissolved solids (TDS), nitrates, fluoride, residual chlorine, and total hardness. Additionally, heavy metal (arsenic) and microbial parameters (E. coli) were also determined in the water samples. Drinking water quality evaluation indices, including the water quality index (WQI) for physico-chemical and biological parameters and human health risk assessment (HHRA) for heavy metal were estimated using the analytical results of the target parameters. It was found in most of the areas that the levels of arsenic, fluoride, TDS, and residual chlorine were higher than those recommended by the National Environmental Quality Standard (NEQS) and World Health Organization (WHO) guidelines. In addition to the physico-chemical parameters, microbial content (E. coli) was also found in the drinking water samples of the selected areas. Statistical analysis of the results indicated that levels of target parameters in drinking water samples are significantly different between sampling sites. The WQI for all physico-chemical and microbial parameters indicated that drinking water in most of the areas was unfit and unsuitable (WQI > 100) for drinking purposes except for the water of Bhatti Gate and Chota Gaon Shahdara with a WQI of 87 and 91, respectively. Drinking water in these areas had a very poor WQI rating. According to HHRA, drinking water from the selected sites was found to be of high risk to children and adults. The carcinogenic risk of arsenic indicated that all samples were of high risk to both adults and children (4.60 and 4.37 × 10^-3, respectively). Regular monitoring of drinking water quality is essential, and proactive measures must be implemented to ensure the treatment and availability of safe drinking water in urban areas.

Investigation of Upper Respiratory Carriage of Bacterial Pathogens among University Students in Kampar, Malaysia

The carriage of bacterial pathogens in the human upper respiratory tract (URT) is associated with a risk of invasive respiratory tract infections, but the related epidemiological information on this at the population level is scarce in Malaysia. This study aimed to investigate the URT carriage of Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa among 100 university students by nasal and oropharyngeal swabbing. The presence of S. aureus, K. pneumoniae and P. aeruginosa was assessed via swab culture on selective media and PCR on the resulting isolates. For S. pneumoniae, H. influenzae and N. meningitidis, their presence was assessed via multiplex PCR on the total DNA extracts from chocolate agar cultures. The carriage prevalence of H. influenzae, S. aureus, S. pneumoniae, K. pneumoniae, N. meningitidis and P. aeruginosa among the subjects was 36%, 27%, 15%, 11%, 5% and 1%, respectively, by these approaches. Their carriage was significantly higher in males compared to females overall. The S. aureus, K. pneumoniae and P. aeruginosa isolates were also screened by the Kirby-Bauer assay, in which 51.6% of S. aureus were penicillin-resistant. The outcomes from carriage studies are expected to contribute to informing infectious disease control policies and guidelines.

Overview of Yersinia pestis Metallophores: Yersiniabactin and Yersinopine

The pathogenic anaerobic bacteria Yersinia pestis (Y. pestis), which is well known as the plague causative agent, has the ability to escape or inhibit innate immune system responses, which can result in host death even before the activation of adaptive responses. Bites from infected fleas in nature transmit Y. pestis between mammalian hosts causing bubonic plague. It was recognized that a host's ability to retain iron is essential in fighting invading pathogens. To proliferate during infection, Y. pestis, like most bacteria, has various iron transporters that enable it to acquire iron from its hosts. The siderophore-dependent iron transport system was found to be crucial for the pathogenesis of this bacterium. Siderophores are low-molecular-weight metabolites with a high affinity for Fe³⁺. These compounds are produced in the surrounding environment to chelate iron. The siderophore secreted by Y. pestis is yersiniabactin (Ybt). Another metallophore produced by this bacterium, yersinopine, is of the opine type and shows similarities with both staphylopine and pseudopaline produced by Staphylococcus aureus and Pseudomonas aeruginosa, respectively. This paper sheds light on the most important aspects of the two Y. pestis metallophores as well as aerobactin a siderophore no longer secreted by this bacterium due to frameshift mutation in its genome.