Copper Is a Host Effector Mobilized to Urine during Urinary Tract Infection To Impair Bacterial Colonization

Heavy Metal-Gut Microbiota Interactions: Probiotics Modulation and Biosensors Detection

This study provides a comprehensive analysis of the complex interaction between heavy metals (HMs) and the gut microbiota, adopting a bidirectional approach that explores both the influence of HMs on the gut microbiota populations and the potential role of probiotics in modulating these changes. By examining these interconnected aspects, the study aims to offer a deeper understanding of how HMs disrupt microbial balance and how probiotic interventions may mitigate or reverse these effects, promoting detoxification processes and overall gut health. In addition, the review highlights innovative tools, such as biosensors, for the rapid, precise, and non-invasive detection of HMs in urine. These advanced technologies enable the real-time monitoring of the effectiveness of probiotic-based interventions, offering critical insights into their role in promoting the elimination of HMs from the body and improving detoxification.

Innovative synthesis and molecular modeling of actinomycetes-derived silver nanoparticles for biomedical applications

The rising demand for innovative antimicrobial solutions has shifted focus towards silver nanoparticles (AgNPs), especially those produced through eco-friendly methods. This study introduces a novel approach utilizing actinomycetes strains-Streptomyces albus, Micromonospora maris, and Arthrobacter crystallopoietes-to biosynthesize AgNPs with remarkable antibacterial properties. Through molecular characterization, we identified unique features of these nanoparticles, and computational modeling suggested significant ion-ligand interactions with proteins 6REV and 3K07. Our research highlights the promise of these biogenically synthesized nanoparticles in advancing biomedical applications. Actinomycetes were sourced and screened for their ability to produce metallic nanoparticles, revealing that among 35 samples, only six showed this capability. Notably, Streptomyces albus strain smmdk14 (OR685674), Micromonospora maris strain smmdk13 (OR685672), and Arthrobacter crystallopoietes strain smmdk12 (OR685674) were identified as effective silver nanoparticle producers. The synthesized nanoparticles demonstrated potent antibacterial activity against common pathogens including E. coli, Pseudomonas aeruginosa, Klebsiella spp., Enterococcus faecalis, Staphylococcus aureus, and Acinetobacter spp. The data obtained from color change observation, UV-visible spectrophotometry, Zeta potential, FTIR spectroscopy, and transmission electron microscopy (TEM) characterized AgNPs potentiality. The nanoparticles were spherical, with sizes ranging from 6.46 nm to 24.7 nm. Optimization of production conditions, comparison of antimicrobial effects with antibiotics, evaluation of potential toxicity, and assessment of wound-healing capabilities were also conducted. The biosynthesized AgNPs exhibited superior antibacterial properties compared to traditional antibiotics and significantly accelerated wound healing by approximately 66.4 % in fibroblast cell cultures. Additionally, computational analysis predicted interactions between various metal ions and specific amino acid residues in proteins 6REV and 3K07. Overall, this study demonstrates the successful creation of AgNPs with notable antibacterial and wound-healing properties, underscoring their potential for medical applications.

A cynomolgus monkey E. coli urinary tract infection model confirms efficacy of new FimH vaccine candidates

The increase in urinary tract infections (UTI) caused by antibiotic-resistant Escherichia coli requires the development of new therapeutic agents and prophylactic vaccines. To evaluate the efficacy of new lead candidates, we implemented a cynomolgus macaque UTI challenge model that mimics human uncomplicated cystitis in response to transurethral challenge with a multidrug-resistant (MDR) E. coli serotype O25b ST131 isolate. E. coli fimbrial adhesin FimH and O-antigens are separately under clinical evaluation by others as vaccine candidates to prevent UTI and invasive urosepsis disease, respectively. Accordingly, we assessed the protective efficacy of three 50-µg intramuscular doses of a novel recombinant FimH antigen adjuvanted with liposomal QS21/MPLA compared with saline placebo in groups of nine animals. A third group was vaccinated with this FimH formulation in combination with 1 µg each of a four-valent mixture of serotype O1a, O2, O6, and O25b O-antigen CRM197 lattice glycoconjugates. Both vaccines elicited high levels of serum FimH IgG and adhesin blocking antibodies at the time of bacterial challenge and, for the combination group, O-antigen-specific antibodies. Following bacterial challenge, both vaccinated groups showed >200- and >700-fold reduction in bacteriuria at day 2 and day 7 post-infection compared with placebo, respectively. In parallel, both vaccines significantly reduced levels of inflammatory biomarkers IL-8 and myeloperoxidase in the urine at day 2 post-infection relative to placebo. Results provide preclinical proof-of-concept for the prevention of an MDR UTI infection by these new vaccine formulations.

A new spectrophotometric method for measuring ceruloplasmin ferroxidase activity: an innovative approach

Ferroxidases are enzymes that participate in the iron metabolism of different organisms. They catalyze the oxidation of ferrous iron, Fe2⁺, into ferric iron, Fe3⁺, which is essential in iron homeostasis and physiological functioning. The present study describes a novel spectrophotometric method of serum ceruloplasmin ferroxidase activity. This method is easy to perform; it is also sensitive, specific, and rapid. In this method, ferrous ions are used as a substrate for the enzyme, with either salicylic acid or sulfosalicylic acid being taken as a chromogenic compound. These chromogens easily form a colored complex with ferric ions but are not formed with ferrous ions. In the enzymatic reaction, the ceruloplasmin ferroxidase enzyme catalyzes the oxidation of ferrous to ferric ions. The resulting increase in ferric ion concentration is then measured spectrophotometrically, following the formation of the colored complex. The complex formed has maximum absorbance at 540 nm in the case of salicylic acid and 490 nm in the case of sulfosalicylic acid. Comparatively, it was tested against the standard method to ascertain the new method's effectuality and reliability for assaying ferroxidase activity. The determined correlation coefficient amounted to 0.99, showing a strong correlation between the results obtained by the two methods. This new spectrophotometric technique offers a simplified, sensitive, specific, and fast means of estimating ferroxidase activity. It avoids using concentrated strong acids in the procedure and correlates excellently with the standard technique. This sets up a potential alternative for accurately determining ferroxidase activity in biological samples.

Acute phase proteins patterns as biomarkers in bacterial infection: Recent insights

Escherichia coli is a bacterium with command and pathogenic variants. It has been implicated in the induction of several inflammatory conditions. Finding a biomarker for infection began many years ago. The challenge of using acute phase proteins (APPs) as biomarkers for infection is a promising target for many researchers in this field. Many APPs have been studied for their roles as biomarkers of E. coli infection. The following review aims to highlight recent trials that have approved the use of adiponectin, amyloid A, ceruloplasmin, C-reactive protein, Haptoglobin, and Pentraxin 3 as biomarkers for E. coli infection and assess the obtained results. In conclusion, despite the existing approaches for the use of APPs as biomarkers in E. coli infection, we recommend more precise studies to enable these markers to be more specific and applicable in clinical fields. APPs could be markers for systemic inflammatory conditions, regardless of the causative agent.

Identification of a copper-responsive small molecule inhibitor of uropathogenic Escherichia coli

Urinary tract infections (UTIs) are a major global health problem and are caused predominantly by uropathogenic Escherichia coli (UPEC). UTIs are a leading cause of prescription antimicrobial use. Incessant increase in antimicrobial resistance in UPEC and other uropathogens poses a serious threat to the current treatment practices. Copper is an effector of nutritional immunity that impedes the growth of pathogens during infection. We hypothesized that copper would augment the toxicity of select small molecules against bacterial pathogens. We conducted a small molecule screening campaign with a library of 51,098 molecules to detect hits that inhibit a UPEC ΔtolC mutant in a copper-dependent manner. A molecule, denoted as E. coli inhibitor or ECIN, was identified as a copper-responsive inhibitor of wild-type UPEC strains. Our gene expression and metal content analysis results demonstrate that ECIN works in concert with copper to exacerbate Cu toxicity in UPEC. ECIN has a broad spectrum of activity against pathogens of medical and veterinary significance including Acinetobacter baumannii, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus. Subinhibitory levels of ECIN eliminate UPEC biofilm formation. Transcriptome analysis of UPEC treated with ECIN reveals induction of multiple stress response systems. Furthermore, we demonstrate that L-cysteine rescues the growth of UPEC exposed to ECIN. In summary, we report the identification and characterization of a novel copper-responsive small molecule inhibitor of UPEC.IMPORTANCEUrinary tract infection (UTI) is a ubiquitous infectious condition affecting millions of people annually. Uropathogenic Escherichia coli (UPEC) is the predominant etiological agent of UTI. However, UTIs are becoming increasingly difficult to resolve with antimicrobials due to increased antimicrobial resistance in UPEC and other uropathogens. Here, we report the identification and characterization of a novel copper-responsive small molecule inhibitor of UPEC. In addition to E. coli, this small molecule also inhibits pathogens of medical and veterinary significance including Acinetobacter baumannii, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus.

Inflammatory immunity and bacteriological perspectives: A new direction for copper treatment of sepsis

Copper is an essential trace element for all aerobic organisms because of its unique biological functions. In recent years, researchers have discovered that copper can induce cell death through various regulatory mechanisms, thereby inducing inflammation. Efforts have also been made to alter the chemical structure of copper to achieve either anticancer or anti-inflammatory effects. The copper ion can exhibit bactericidal effects by interfering with the integrity of the cell membrane and promoting oxidative stress. Sepsis is a systemic inflammatory response caused by infection. Some studies have revealed that copper is involved in the pathophysiological process of sepsis and is closely related to its prognosis. During the infection of sepsis, the body may enhance the antimicrobial effect by increasing the release of copper. However, to avoid copper poisoning, all organisms have evolved copper resistance genes. Therefore, further analysis of the complex relationship between copper and bacteria may provide new ideas and research directions for the treatment of sepsis.

The inner membrane protein YhiM links copper and CpxAR envelope stress responses in uropathogenic E. coli

Urinary tract infection (UTI) is a ubiquitous infectious condition, and uropathogenic Escherichia coli (UPEC) is the predominant causative agent of UTI. Copper (Cu) is implicated in innate immunity, including against UPEC. Cu is a trace element utilized as a co-factor, but excess Cu is toxic due to mismetalation of non-cognate proteins. E. coli precisely regulates Cu homeostasis via efflux systems. However, Cu import mechanisms into the bacterial cell are not clear. We hypothesized that Cu import defective mutants would exhibit increased resistance to Cu. This hypothesis was tested in a forward genetic screen with transposon (Tn5) insertion mutants in UPEC strain CFT073, and we identified 32 unique Cu-resistant mutants. Transposon and defined mutants lacking yhiM, which encodes a hypothetical inner membrane protein, were more resistant to Cu than parental strain. Loss of YhiM led to decreased cellular Cu content and increased expression of copA, encoding a Cu efflux pump. The CpxAR envelope stress response system was activated in the ΔyhiM mutant as indicated by increased expression of cpxP. Transcription of yhiM was regulated by CueR and CpxR, and the CpxAR system was essential for increased Cu resistance in the ΔyhiM mutant. Importantly, activation of CpxAR system in the ΔyhiM mutant was independent of NlpE, a known activator of this system. YhiM was required for optimal fitness of UPEC in a mouse model of UTI. Our findings demonstrate that YhiM is a critical mediator of Cu homeostasis and links bacterial adaptation to Cu stress with the CpxAR-dependent envelope stress response in UPEC.IMPORTANCEUPEC is a common bacterial infection. Bacterial pathogens are exposed to host-derived Cu during infection, including UTI. Here, we describe detection of genes involved in Cu homeostasis in UPEC. A UPEC mutant lacking YhiM, a membrane protein, exhibited dramatic increase in resistance to Cu. Our study demonstrates YhiM as a nexus between Cu stress and the CpxAR-dependent envelope stress response system. Importantly, our findings establish NlpE-independent activation of CpxAR system during Cu stress in UPEC. Collectively, YhiM emerges as a critical mediator of Cu homeostasis in UPEC and highlights the interlinked nature of bacterial adaptation to survival during Cu and envelope stress.

Photochemical inactivation as an alternative method to produce a whole-cell vaccine for uropathogenic Escherichia coli (UPEC)

Uropathogenic Escherichia coli (UPEC) is the primary causative agent of lower urinary tract infection (UTI). UTI presents a serious health risk and has considerable secondary implications including economic burden, recurring episodes, and overuse of antibiotics. A safe and effective vaccine would address this widespread health problem and emerging antibiotic resistance. Killed, whole-cell vaccines have shown limited efficacy to prevent recurrent UTI in human trials. We explored photochemical inactivation with psoralen drugs and UVA light (PUVA), which crosslinks nucleic acid, as an alternative to protein-damaging methods of inactivation to improve whole-cell UTI vaccines. Exposure of UPEC to the psoralen drug AMT and UVA light resulted in a killed but metabolically active (KBMA) state, as reported previously for other PUVA-inactivated bacteria. The immunogenicity of PUVA-UPEC as compared to formalin-inactivated UPEC was compared in mice. Both generated high UPEC-specific serum IgG titers after intramuscular delivery. However, using functional adherence as a measure of surface protein integrity, we found differences in the properties of PUVA- and formalin-inactivated UPEC. Adhesion mediated by Type-1 and P-fimbriae was severely compromised by formalin but was unaffected by PUVA, indicating that PUVA preserved the functional conformation of fimbrial proteins, which are targets of protective immune responses. In vitro assays indicated that although they retained metabolic activity, PUVA-UPEC lost virulence properties that could negatively impact vaccine safety. Our results imply the potential for PUVA to improve killed, whole-cell UTI vaccines by generating bacteria that more closely resemble their live, infectious counterparts relative to vaccines generated with protein-damaging methods.

IMPORTANCE

Lower urinary tract infection (UTI), caused primarily by uropathogenic Escherichia coli, represents a significant health burden, accounting for 7 million primary care and 1 million emergency room visits annually in the United States. Women and the elderly are especially susceptible and recurrent infection (rUTI) is common in those populations. Lower UTI can lead to life-threatening systemic infection. UTI burden is manifested by healthcare dollars spent (1.5 billion annually), quality of life impact, and resistant strains emerging from antibiotic overuse. A safe and effective vaccine to prevent rUTI would address a substantial healthcare issue. Vaccines comprised of inactivated uropathogenic bacteria have yielded encouraging results in clinical trials but improvements that enhance vaccine performance are needed. To that end, we focused on inactivation methodology and provided data to support photochemical inactivation, which targets nucleic acid, as a promising alternative to conventional protein-damaging inactivation methods to improve whole-cell UTI vaccines.

Scs system links copper and redox homeostasis in bacterial pathogens

The bacterial envelope is an essential compartment involved in metabolism and metabolites transport, virulence, and stress defense. Its roles become more evident when homeostasis is challenged during host-pathogen interactions. In particular, the presence of free radical groups and excess copper in the periplasm causes noxious reactions, such as sulfhydryl group oxidation leading to enzymatic inactivation and protein denaturation. In response to this, canonical and accessory oxidoreductase systems are induced, performing quality control of thiol groups, and therefore contributing to restoring homeostasis and preserving survival under these conditions. Here, we examine recent advances in the characterization of the Dsb-like, Salmonella-specific Scs system. This system includes the ScsC/ScsB pair of Cu+-binding proteins with thiol-oxidoreductase activity, an alternative ScsB-partner, the membrane-linked ScsD, and a likely associated protein, ScsA, with a role in peroxide resistance. We discuss the acquisition of the scsABCD locus and its integration into a global regulatory pathway directing envelope response to Cu stress during the evolution of pathogens that also harbor the canonical Dsb systems. The evidence suggests that the canonical Dsb systems cannot satisfy the extra demands that the host-pathogen interface imposes to preserve functional thiol groups. This resulted in the acquisition of the Scs system by Salmonella. We propose that the ScsABCD complex evolved to connect Cu and redox stress responses in this pathogen as well as in other bacterial pathogens.

Copper affects virulence and diverse phenotypes of uropathogenic Proteus mirabilis

BACKGROUND

Copper plays a role in urinary tract infection (UTI) and urinary copper content is increased during Proteus mirabilis UTI. We therefore investigated the effect of copper on uropathogenic P. mirabilis and the underlying mechanisms, focusing on the virulence associated aspects.

METHODS

Mouse colonization, swarming/swimming assays, measurement of cell length, flagellin level and urease activity, adhesion/invasion assay, biofilm formation, killing by macrophages, oxidative stress susceptibility, OMPs analysis, determination of MICs and persister cell formation, RT-PCR and transcriptional reporter assay were performed.

RESULTS

We found that copper-supplemented mice were more resistant to be colonized in the urinary tract, together with decreased swarming/swimming, ureases activity, expression of type VI secretion system and adhesion/invasion to urothelial cells and increased killing by macrophages of P. mirabilis at a sublethal copper level. However, bacterial biofilm formation and resistance to oxidative stress were enhanced under the same copper level. Of note, the presence of copper led to increased ciprofloxacin MIC and more persister cell formation against ampicillin. In addition, the presence of copper altered the outer membrane protein profile and triggered expression of RcsB response regulator. For the first time, we unveiled the pleiotropic effects of copper on uropathogenic P. mirabilis, especially for induction of bacterial two-component signaling system regulating fitness and virulence.

CONCLUSION

The finding of copper-mediated virulence and fitness reinforced the importance of copper for prevention and therapeutic interventions against P. mirabilis infections. As such, this study could facilitate the copper-based strategies against UTI by P. mirabilis.

Survey of the infant male urobiome and genomic analysis of Actinotignum spp

The urinary bladder harbors a community of microbes termed the urobiome, which remains understudied. In this study, we present the urobiome of healthy infant males from samples collected by transurethral catheterization. Using a combination of enhanced culture and amplicon sequencing, we identify several common bacterial genera that can be further investigated for their effects on urinary health across the lifespan. Many genera were shared between all samples suggesting a consistent urobiome composition among this cohort. We note that, for this cohort, early life exposures including mode of birth (vaginal vs. Cesarean section), or prior antibiotic exposure did not influence urobiome composition. In addition, we report the isolation of culturable bacteria from the bladders of these infant males, including Actinotignum spp., a bacterial genus that has been associated with urinary tract infections in older male adults. Herein, we isolate and sequence 9 distinct strains of Actinotignum spp. enhancing the genomic knowledge surrounding this genus and opening avenues for delineating the microbiology of this urobiome constituent. Furthermore, we present a framework for using the combination of culture-dependent and sequencing methodologies for uncovering mechanisms in the urobiome.

Macroelement and Microelement Levels in the Urine in Experimental Acanthamoebiasis

Free-living amoebas can impact the excretion of macroelements and microelements in urine. The aim of the present study was to examine the concentrations of macroelements, including calcium (Ca), phosphorus (P), sodium (Na), potassium (K), and magnesium (Mg), as well as microelements such as manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), and chromium (Cr), in the urine during acanthamoebiasis while considering the host's immunological status. This is the first study to show an increase in urinary excretion of Ca, Mn, Cu, Fe, Na, and Cr, along with a decreased excretion of K, in immunocompetent mice 16 days post Acanthamoeba sp. infection. In the final phase of infection (24 dpi), there was a further decrease in urinary K excretion and a lower level of P in Acanthamoeba sp. infected immunocompetent hosts. During acanthamoebiasis in immunosuppressed hosts, increased excretion of Zn, Fe, and Cr was observed at the beginning of the infection, and increased Na excretion only at 16 days post Acanthamoeba sp. infection. Additionally, host immunosuppression affected the concentration of Fe, Cr, Zn, Cu, Mn, and Ca in urine.

Control of nutrient metal availability during host-microbe interactions: beyond nutritional immunity

The control of nutrient availability is an essential ecological function of the host organism in host-microbe systems. Although often overshadowed by macronutrients such as carbohydrates, micronutrient metals are known as key drivers of host-microbe interactions. The ways in which host organisms control nutrient metal availability are dictated by principles in bioinorganic chemistry. Here I ponder about the actions of metal-binding molecules from the host organism in controlling nutrient metal availability to the host microbiota. I hope that these musings will encourage new explorations into the fundamental roles of metals in the ecology of diverse host-microbe systems.

Machine learning-based identification of cuproptosis-related markers and immune infiltration in severe community-acquired pneumonia

BACKGROUND

Severe community-acquired pneumonia (SCAP) is one of the world's most common diseases and a major etiology of acute respiratory distress syndrome (ARDS). Cuproptosis is a novel form of regulated cell death that can occur in various diseases.

METHODS

Our study explored the degree of immune cell infiltration during the onset of severe CAP and identified potential biomarkers related to cuproptosis. Gene expression matrix was obtained from GEO database indexed GSE196399. Three machine learning algorithms were applied: The least absolute shrinkage and selection operator (LASSO), the random forest, and the support vector machine-recursive feature elimination (SVM-RFE). Immune cell infiltration was quantified by single-sample gene set enrichment analysis (ssGSEA) scoring. Nomogram was constructed to verify the applicability of using cuproptosis-related genes to predict the onset of severe CAP and its deterioration toward ARDS.

RESULTS

Nine cuproptosis-related genes were differentially expressed between the severe CAP group and the control group: ATP7B, DBT, DLAT, DLD, FDX1, GCSH, LIAS, LIPT1, and SLC31A1. All 13 cuproptosis-related genes were involved in immune cell infiltration. A three-gene diagnostic model was constructed to predict the onset of severe CAP: GCSH, DLD, and LIPT1.

CONCLUSION

Our study confirmed the involvement of the newly discovered cuproptosis-related genes in the progression of SCAP.

Defining the Infant Male Urobiome and Moving Towards Mechanisms in Urobiome Research

The urinary bladder harbors a community of microbes termed the urobiome, which remains understudied. In this study, we present the urobiome of healthy infant males from samples collected by transurethral catheterization. Using a combination of extended culture and amplicon sequencing, we identify several common bacterial genera that can be further investigated for their effects on urinary health across the lifespan. Many genera were shared between all samples suggesting a consistent urobiome composition among this cohort. We note that, for this cohort, early life exposures including mode of birth (vaginal vs. Caesarean section), or prior antibiotic exposure did not influence urobiome composition. In addition, we report the isolation of culturable bacteria from the bladders of these infant males, including Actinotignum schaalii, a bacterial species that has been associated with urinary tract infection in older male adults. Herein, we isolate and sequence 9 distinct strains of A. schaalii enhancing the genomic knowledge surrounding this species and opening avenues for delineating the microbiology of this urobiome constituent. Furthermore, we present a framework for using the combination of culture-dependent and sequencing methodologies for uncovering mechanisms in the urobiome.

Host-Mediated Copper Stress Is Not Protective against Streptococcus pneumoniae D39 Infection

Metal ions are required by all organisms for the chemical processes that support life. However, in excess they can also exert toxicity within biological systems. During infection, bacterial pathogens such as Streptococcus pneumoniae are exposed to host-imposed metal intoxication, where the toxic properties of metals, such as copper, are exploited to aid in microbial clearance. However, previous studies investigating the antimicrobial efficacy of copper in vivo have reported variable findings. Here, we use a highly copper-sensitive strain of S. pneumoniae, lacking both copper efflux and intracellular copper buffering by glutathione, to investigate how copper stress is managed and where it is encountered during infection. We show that this strain exhibits highly dysregulated copper homeostasis, leading to the attenuation of growth and hyperaccumulation of copper in vitro. In a murine infection model, whole-tissue copper quantitation and elemental bioimaging of the murine lung revealed that infection with S. pneumoniae resulted in increased copper abundance in specific tissues, with the formation of spatially discrete copper hot spots throughout the lung. While the increased copper was able to reduce the viability of the highly copper-sensitive strain in a pneumonia model, copper levels in professional phagocytes and in a bacteremic model were insufficient to prosecute bacterial clearance. Collectively, this study reveals that host copper is redistributed to sites of infection and can impact bacterial viability in a hypersusceptible strain. However, in wild-type S. pneumoniae, the concerted actions of the copper homeostatic mechanisms are sufficient to facilitate continued viability and virulence of the pathogen. IMPORTANCE Streptococcus pneumoniae (the pneumococcus) is one of the world's foremost bacterial pathogens. Treatment of both localized and systemic pneumococcal infection is becoming complicated by increasing rates of multidrug resistance globally. Copper is a potent antimicrobial agent used by the mammalian immune system in the defense against bacterial pathogens. However, unlike other bacterial species, this copper stress is unable to prosecute pneumococcal clearance. This study determines how the mammalian host inflicts copper stress on S. pneumoniae and the bacterial copper tolerance mechanisms that contribute to maintenance of viability and virulence in vitro and in vivo. This work has provided insight into the chemical biology of the host-pneumococcal interaction and identified a potential avenue for novel antimicrobial development.

Interactive Effects of Copper-Doped Urological Implants with Tissue in the Urinary Tract for the Inhibition of Cell Adhesion and Encrustation in the Animal Model Rat

The insertion of a ureteral stent provides acute care by restoring urine flow and alleviating urinary retention or dysfunction. The problems of encrustation, bacterial colonization and biofilm formation become increasingly important when ureteral stents are left in place for a longer period of time. One way to reduce encrustation and bacterial adherence is to modify the stent surface with a diamond-like carbon coating, in combination with copper doping. The biocompatibilities of the Elastollan^® base material and the a-C:H/Cu-mulitilayer coating were tested in synthetic urine. The copper content in bladder tissue was determined by atomic absorption spectroscopy and in blood and in urine by inductively coupled plasma mass spectrometry. Encrustations on the materials were analyzed by scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. A therapeutic window for copper ions of 0.5–1.0 mM was determined to kill bacteria without affecting human urothelial cells. In the rat animal model, it was found that copper release did not reach toxic concentrations in the affecting tissue of the urinary tract or in the blood. The encrustation behavior of the surfaces showed that the roughness of the amorphous carbon layer with the copper doping is probably the causal factor for the higher encrustation.

Acclimation to Nutritional Immunity and Metal Intoxication Requires Zinc, Manganese, and Copper Homeostasis in the Pathogenic Neisseriae

Neisseria gonorrhoeae and Neisseria meningitidis are human-specific pathogens in the Neisseriaceae family that can cause devastating diseases. Although both species inhabit mucosal surfaces, they cause dramatically different diseases. Despite this, they have evolved similar mechanisms to survive and thrive in a metal-restricted host. The human host restricts, or overloads, the bacterial metal nutrient supply within host cell niches to limit pathogenesis and disease progression. Thus, the pathogenic Neisseria require appropriate metal homeostasis mechanisms to acclimate to such a hostile and ever-changing host environment. This review discusses the mechanisms by which the host allocates and alters zinc, manganese, and copper levels and the ability of the pathogenic Neisseria to sense and respond to such alterations. This review will also discuss integrated metal homeostasis in N. gonorrhoeae and the significance of investigating metal interplay.

A Novel Cuproptosis-Related Prognostic Gene Signature and Validation of Differential Expression in Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most prevalent subtype of renal cell carcinoma, which is characterized by metabolic reprogramming. Cuproptosis, a novel form of cell death, is highly linked to mitochondrial metabolism and mediated by protein lipoylation. However, the clinical impacts of cuproptosis-related genes (CRGs) in ccRCC largely remain unclear. In the current study, we systematically evaluated the genetic alterations of cuproptosis-related genes in ccRCC. Our results revealed that CDKN2A, DLAT, DLD, FDX1, GLS, PDHA1 and PDHB exhibited differential expression between ccRCC and normal tissues (|log2(fold change)| > 2/3 and p < 0.05). Utilizing an iterative sure independence screening (SIS) method, we separately constructed the prognostic signature of CRGs for predicting the overall survival (OS) and progression-free survival (PFS) in ccRCC patients. The prognostic score of CRGs yielded an area under the curve (AUC) of 0.658 and 0.682 for the prediction of 5-year OS and PFS, respectively. In the Kaplan−Meier survival analysis of OS, a higher risk score of cuproptosis-related gene signature was significantly correlated with worse overall survival (HR = 2.72 (2.01−3.68), log-rank p = 1.76 × 10−7). Patients with a higher risk had a significantly shorter PFS (HR = 2.83 (2.08−3.85), log-rank p = 3.66 × 10−7). Two independent validation datasets (GSE40435 (N = 101), GSE53757 (N = 72)) were collected for meta-analysis, suggesting that CDKN2A (log2(fold change) = 1.46, 95%CI: 1.75−2.35) showed significantly higher expression in ccRCC tissues while DLAT (log2(fold change) = −0.54, 95%CI: −0.93−−0.15) and FDX1 (log2(fold change) = −1.01, 95%CI: −1.61−−0.42) were lowly expressed. The expression of CDKN2A and FDX1 in ccRCC was also significantly associated with immune infiltration levels and programmed cell death protein 1 (PD-1) expression (CDKN2A: r = 0.24, p = 2.14 × 10−8; FDX1: r = −0.17, p = 1.37 × 10−4). In conclusion, the cuproptosis-related gene signature could serve as a potential prognostic predictor for ccRCC patients and may offer novel insights into the cancer treatment.

Copper Homeostatic Mechanisms and Their Role in the Virulence of Escherichia coli and Salmonella enterica

Copper is an essential micronutrient that also exerts toxic effects at high concentrations. This review summarizes the current state of knowledge on copper handling and homeostasis systems in Escherichia coli and Salmonella enterica. We describe the mechanisms by which transcriptional regulators, efflux pumps, detoxification enzymes, metallochaperones, and ancillary copper response systems orchestrate cellular response to copper stress. E. coli and S. enterica are important pathogens of humans and animals. We discuss the critical role of copper during killing of these pathogens by macrophages and in nutritional immunity at the bacterial-pathogen-host interface. In closing, we identify opportunities to advance our understanding of the biological roles of copper in these model enteric bacterial pathogens.

Copper Resistance Promotes Fitness of Methicillin-Resistant Staphylococcus aureus during Urinary Tract Infection

Urinary tract infection (UTI) is one of the most common infectious conditions affecting people in the United States and around the world. Our knowledge of the host-pathogen interaction during UTI caused by Gram-positive bacterial uropathogens is limited compared to that for Gram-negative pathogens. Here, we investigated whether copper and the primary copper-containing protein, ceruloplasmin, are mobilized to urine during naturally occurring UTI caused by Gram-positive uropathogens in patients. Next, we probed the role of copper resistance in the fitness of methicillin-resistant Staphylococcus aureus (MRSA) during experimental UTI in a murine model. Our findings demonstrate that urinary copper and ceruloplasmin content are elevated during UTI caused by Enterococcus faecalis, S. aureus, S. epidermidis, and S. saprophyticus. MRSA strains successfully colonize the urinary tract of female CBA mice with selective induction of inflammation in the kidneys but not the bladder. MRSA mutants lacking CopL, a copper-binding cell surface lipoprotein, and the ACME genomic region containing copL, exhibit decreased fitness in the mouse urinary tract compared to parental strains. Copper sensitivity assays, cell-associated copper and iron content, and bioavailability of iron during copper stress demonstrate that homeostasis of copper and iron is interlinked in S. aureus. Importantly, relative fitness of the MRSA mutant lacking the ACME region is further decreased in mice that receive supplemental copper compared to the parental strain. In summary, copper is mobilized to the urinary tract during UTI caused by Gram-positive pathogens, and copper resistance is a fitness factor for MRSA during UTI. IMPORTANCE Urinary tract infection (UTI) is an extremely common infectious condition affecting people throughout the world. Increasing antibiotic resistance in pathogens causing UTI threatens our ability to continue to treat patients in the clinics. Better understanding of the host-pathogen interface is critical for development of novel interventional strategies. Here, we sought to elucidate the role of copper in host-Staphylococcus aureus interaction during UTI. Our results reveal that copper is mobilized to the urine as a host response in patients with UTI. Our findings from the murine model of UTI demonstrate that copper resistance is involved in the fitness of methicillin-resistant S. aureus (MRSA) during interaction with the host. We also establish a critical link between adaptation to copper stress and iron homeostasis in S. aureus.

A genome-wide screen reveals the involvement of enterobactin-mediated iron acquisition in Escherichia coli survival during copper stress

Copper (Cu) is a key transition metal that is involved in many important biological processes in a cell. Cu is also utilized by the immune system to hamper pathogen growth during infection. However, genome-level knowledge on the mechanisms involved in adaptation to Cu stress is limited. Here, we report the results of a genome-wide reverse genetic screen for Cu-responsive phenotypes in Escherichia coli. Our screen has identified novel genes involved in adaptation to Cu stress in E. coli. We detected multiple genes involved in the biosynthesis and uptake of enterobactin, a siderophore utilized for high-affinity TonB-dependent acquisition of iron (Fe), as critical players in survival under Cu intoxication. We demonstrated the specificity of Cu-dependent killing by chelation of Cu and by genetic complementation of tonB. Notably, TonB is involved in protection from Cu in both laboratory and uropathogenic strains of E. coli. Cu stress leads to increased expression of the genes involved in Fe uptake, indicating that Fur regulon is derepressed during exposure to excess Cu. Trace element analyses revealed that Fe homeostasis is dysregulated during Cu stress. Taken together, our data supports a model in which lack of enterobactin-dependent Fe uptake leads to exacerbation of Cu toxicity, and elucidates the intricate connection between the homeostasis of Cu and Fe in a bacterial cell.

Whole Genome Sequencing of Methicillin-Resistant Staphylococcus epidermidis Clinical Isolates Reveals Variable Composite SCCmec ACME among Different STs in a Tertiary Care Hospital in Oman

Staphylococcus epidermidis has been recently recognized as an emerging nosocomial pathogen. There are concerns over the increasing virulence potential of this commensal due to the capabilities of transferring mobile genetic elements to Staphylococcus aureus through staphylococcal chromosomal cassette (SCCmec) and the closely related arginine catabolic mobile element (ACME) and the copper and mercury resistance island (COMER). The potential pathogenicity of S. epidermidis, particularly from blood stream infections, has been poorly investigated. In this study, 24 S. epidermidis isolated from blood stream infections from Oman were investigated using whole genome sequence analysis. Core genome phylogenetic trees revealed one third of the isolates belong to the multidrug resistance ST-2. Genomic analysis unraveled a common occurrence of SCCmec type IV and ACME element predominantly type I arranged in a composite island. The genetic composition of ACME was highly variable among isolates of same or different STs. The COMER-like island was absent in all of our isolates. Reduced copper susceptibility was observed among isolates of ST-2 and ACME type I, followed by ACME type V. In conclusion, in this work, we identify a prevalent occurrence of highly variable ACME elements in different hospital STs of S. epidermidis in Oman, thus strongly suggesting the hypothesis that ACME types evolved from closely related STs.

Recurrent Urinary Tract Infections: Unraveling the Complicated Environment of Uncomplicated rUTIs

Urinary tract infections (UTIs) are frequent in humans, affecting the upper and lower urinary tract. Present diagnosis relies on the positive culture of uropathogenic bacteria from urine and clinical markers of inflammation of the urinary tract. The bladder is constantly challenged by adverse environmental stimuli which influence urinary tract physiology, contributing to a dysbiotic environment. Simultaneously, pathogens are primed by environmental stressors such as antibiotics, favoring recurrent UTIs (rUTIs), resulting in chronic illness. Due to different confounders for UTI onset, a greater understanding of the fundamental environmental mechanisms and microbial ecology of the human urinary tract is required. Such advancements could promote the tandem translation of bench and computational studies for precision treatments and clinical management of UTIs. Therefore, there is an urgent need to understand the ecological interactions of the human urogenital microbial communities which precede rUTIs. This review aims to outline the mechanistic aspects of rUTI ecology underlying dysbiosis between both the human microbiome and host physiology which predisposes humans to rUTIs. By assessing the applications of next generation and systems level methods, we also recommend novel approaches to elucidate the systemic consequences of rUTIs which requires an integrated approach for successful treatment. To this end, we will provide an outlook towards the so-called 'uncomplicated environment of UTIs', a holistic and systems view that applies ecological principles to define patient-specific UTIs. This perspective illustrates the need to withdraw from traditional reductionist perspectives in infection biology and instead, a move towards a systems-view revolving around patient-specific pathophysiology during UTIs.

Staphylococcus saprophyticus Causing Infections in Humans Is Associated with High Resistance to Heavy Metals

Staphylococcus saprophyticus is a common pathogen of the urinary tract, a heavy metal-rich environment, but information regarding its heavy metal resistance is unknown. We investigated 422 S. saprophyticus isolates from human infection and colonization/contamination, animals, and environmental sources for resistance to copper, zinc, arsenic, and cadmium using the agar dilution method. To identify the genes associated with metal resistance and assess possible links to pathogenicity, we accessed the whole-genome sequence of all isolates and used in silico and pangenome-wide association approaches. The MIC values for copper and zinc were uniformly high (1,600 mg/liter). Genes encoding copper efflux pumps (copA, copB, copZ, mco, and csoR) and zinc transporters (zinT, czrAB, znuBC, and zur) were abundant in the population (20 to 100%). Arsenic and cadmium showed various susceptibility levels. Genes encoding the ars operon (arsRDABC), an ABC transporter and a two-component permease, were linked to resistance to arsenic (MICs ≥ 1,600 mg/liter; 14% [58/422]; P < 0.05). At least three cad genes (cadA or cadC and cadD-cadX or czrC) and genes encoding multidrug efflux pumps and hyperosmoregulation in acidified conditions were associated with resistance to cadmium (MICs ≥ 200 mg/liter; 20% [85/422]; P < 0.05). These resistance genes were frequently carried by mobile genetic elements. Resistance to arsenic and cadmium were linked to human infection and a clonal lineage originating in animals (P < 0.05). Altogether, S. saprophyticus was highly resistant to heavy metals and accumulated multiple metal resistance determinants. The highest arsenic and cadmium resistance levels were associated with infection, suggesting resistance to these metals is relevant for S. saprophyticus pathogenicity.

Genomics and Virulence of Klebsiella pneumoniae Kpnu95 ST1412 Harboring a Novel Incf Plasmid Encoding Blactx-M-15 and Qnrs1 Causing Community Urinary Tract Infection

The emergence of extended-spectrum β-lactamase (ESBL)-producing multidrug resistant Klebsiella pneumoniae causing community urinary tract infections (CA-UTI) in healthy women undermines effective treatment and poses a public health concern. We performed a comprehensive genomic analysis (Illumina and MinION) and virulence studies using Caenorhabditis elegans nematodes to evaluate KpnU95, a bla_CTX-M-15-producing CA-UTI K. pneumoniae strain. Whole genome sequencing identified KpnU95 as sequence type 1412 and revealed the chromosomal and plasmid-encoding resistome, virulome and persistence features. KpnU95 possess a wide virulome and caused complete C. elegans killing. The strain harbored a single novel 180.3Kb IncFIB(K) plasmid (pKpnU95), which encodes ten antibiotic resistance genes, including bla_CTX-M-15 and qnrS1 alongside a wide persistome encoding heavy metal and UV resistance. Plasmid curing and reconstitution were used for loss and gain studies to evaluate its role on bacterial resistance, fitness and virulence. Plasmid curing abolished the ESBL phenotype, decreased ciprofloxacin MIC and improved bacterial fitness in artificial urine accompanied with enhanced copper tolerance, without affecting bacterial virulence. Meta-analysis supported the uniqueness of pKpnU95 and revealed plasmid-ST1412 lineage adaptation. Overall, our findings provide translational data on a CA-UTI K. pneumoniae ST1412 strain and demonstrates that ESBL-encoding plasmids play key roles in multidrug resistance and in bacterial fitness and persistence.

Transcription factor-driven alternative localization of Cryptococcus neoformans superoxide dismutase

Cryptococcus neoformans is an opportunistic fungal pathogen whose pathogenic lifestyle is linked to its ability to cope with fluctuating levels of copper (Cu), an essential metal involved in multiple virulence mechanisms, within distinct host niches. During lethal cryptococcal meningitis in the brain, C. neoformans senses a Cu-deficient environment and is highly dependent on its ability to scavenge trace levels of Cu from its host and adapt to Cu scarcity to successfully colonize this niche. In this study, we demonstrate for this critical adaptation, the Cu-sensing transcription factor Cuf1 differentially regulates the expression of the SOD1 and SOD2 superoxide dismutases in novel ways. Genetic and transcriptional analysis reveals Cuf1 specifies 5’-truncations of the SOD1 and SOD2 mRNAs through specific binding to Cu responsive elements within their respective promoter regions. This results in Cuf1-dependent repression of the highly abundant SOD1 and simultaneously induces expression of two isoforms of SOD2, the canonical mitochondrial targeted isoform and a novel alternative cytosolic isoform, from a single alternative transcript produced specifically under Cu limitation. The generation of cytosolic Sod2 during Cu limitation is required to maintain cellular antioxidant defense against superoxide stress both in vitro and in vivo. Further, decoupling Cuf1 regulation of Sod2 localization compromises the ability of C. neoformans to colonize organs in murine models of cryptococcosis. Our results provide a link between transcription factor–mediated alteration of protein localization and cell proliferation under stress, which could impact tissue colonization by a fungal pathogen.

Antimicrobial Peptides and Copper(II) Ions: Novel Therapeutic Opportunities

The emergence of new pathogens and multidrug resistant bacteria is an important public health issue that requires the development of novel classes of antibiotics. Antimicrobial peptides (AMPs) are a promising platform with great potential for the identification of new lead compounds that can combat the aforementioned pathogens due to their broad-spectrum antimicrobial activity and relatively low rate of resistance emergence. AMPs of multicellular organisms made their debut four decades ago thanks to ingenious researchers who asked simple questions about the resistance to bacterial infections of insects. Questions such as "Do fruit flies ever get sick?", combined with pioneering studies, have led to an understanding of AMPs as universal weapons of the immune system. This review focuses on a subclass of AMPs that feature a metal binding motif known as the amino terminal copper and nickel (ATCUN) motif. One of the metal-based strategies of hosts facing a pathogen, it includes wielding the inherent toxicity of copper and deliberately trafficking this metal ion into sites of infection. The sudden increase in the concentration of copper ions in the presence of ATCUN-containing AMPs (ATCUN-AMPs) likely results in a synergistic interaction. Herein, we examine common structural features in ATCUN-AMPs that exist across species, and we highlight unique features that deserve additional attention. We also present the current state of knowledge about the molecular mechanisms behind their antimicrobial activity and the methods available to study this promising class of AMPs.

Deep insights into urinary tract infections and effective natural remedies

Background

Urinary tract infection (UTI) is a common occurrence in females, during pregnancy, and in peri- and postmenopausal women. UTIs are associated with significant morbidity and mortality, and they affect the quality of life of the affected patients. Antibiotic therapy is an effective approach and reduces the duration of symptoms. Development of resistance, adverse effects of antibiotics, and other associated problems lead to establishing the research framework to find out the alternative approaches in controlling UTIs. Natural approaches have been extensively used for the management of various diseases to improve symptoms and also improve general health.

Main body

Different databases were employed to identify studies reporting on natural options including herbal medicines, vitamins, trace elementals, sugars, and probiotics without time limitations.

Conclusion

Herbal medicines can be effective at the first sign of the infection and also for short-term prophylaxis. Using vitamins, trace elementals, and/or sugars is an effective approach in preventing UTIs, and a combination of them with other antibacterial agents shows positive results. Probiotics have great potential for the threat of antibiotic over-usage and the prevalence of antibiotic-resistant microorganisms. This study may be of use in developing the efficient formulation of treatment of UTI.

Inflammation accelerates copper-mediated cytotoxicity through induction of six-transmembrane epithelial antigens of prostate 4 expression

Copper is an essential trace metal, but imbalance in copper homeostasis can induce oxidative damage. Inflammation is a fundamental element of various pulmonary diseases. Although a positive relationship between copper and chronic pulmonary diseases has been reported, the underlying reasons are still not clear. The copper level in the sputum of patients with various pulmonary diseases was measured. An inflammatory model was established to evaluate the impact of inflammation on copper uptake in the lung. We found that the level of sputum copper was increased in patients with various pulmonary diseases, especially chronic obstructive pulmonary disease and asthma. Then, we confirmed that mice with pulmonary inflammation were susceptible to copper-mediated oxidative damage because of copper overload in lung tissue. Further investigation demonstrated that interleukin (IL)-17 and tumor necrosis factor (TNF)-α exerted synergistic effects in airway epithelial cells by upregulating the expression of six-transmembrane epithelial antigens of prostate 4 (STEAP4), a metalloreductase that reduces extracellular copper ions from the cupric state to the cuprous state and facilitates copper uptake. Inhibition of STEAP4 decreased the copper uptake of cells and inhibited copper-mediated oxidative damage. Moreover, we demonstrated that the upregulation of STEAP4 by IL-17 and TNF-α was largely dependent on TNF receptor-associated factor 4 (TRAF4). Traf4^-/- mice were resistant to copper-mediated oxidative damage. Our data suggest a novel IL-17/TNF-α-TRAF4-STEAP4 axis that regulates copper homeostasis.

Role of Glutathione in Buffering Excess Intracellular Copper in Streptococcus pyogenes

Copper (Cu) is an essential metal for bacterial physiology but in excess it is bacteriotoxic. To limit Cu levels in the cytoplasm, most bacteria possess a transcriptionally responsive system for Cu export. In the Gram-positive human pathogen Streptococcus pyogenes (group A Streptococcus [GAS]), this system is encoded by the copYAZ operon. This study demonstrates that although the site of GAS infection represents a Cu-rich environment, inactivation of the copA Cu efflux gene does not reduce virulence in a mouse model of invasive disease. In vitro, Cu treatment leads to multiple observable phenotypes, including defects in growth and viability, decreased fermentation, inhibition of glyceraldehyde-3-phosphate dehydrogenase (GapA) activity, and misregulation of metal homeostasis, likely as a consequence of mismetalation of noncognate metal-binding sites by Cu. Surprisingly, the onset of these effects is delayed by ∼4 h even though expression of copZ is upregulated immediately upon exposure to Cu. Further biochemical investigations show that the onset of all phenotypes coincides with depletion of intracellular glutathione (GSH). Supplementation with extracellular GSH replenishes the intracellular pool of this thiol and suppresses all the observable effects of Cu treatment. These results indicate that GSH buffers excess intracellular Cu when the transcriptionally responsive Cu export system is overwhelmed. Thus, while the copYAZ operon is responsible for Cu homeostasis, GSH has a role in Cu tolerance and allows bacteria to maintain metabolism even in the presence of an excess of this metal ion.IMPORTANCE The control of intracellular metal availability is fundamental to bacterial physiology. In the case of copper (Cu), it has been established that rising intracellular Cu levels eventually fill the metal-sensing site of the endogenous Cu-sensing transcriptional regulator, which in turn induces transcription of a copper export pump. This response caps intracellular Cu availability below a well-defined threshold and prevents Cu toxicity. Glutathione, abundant in many bacteria, is known to bind Cu and has long been assumed to contribute to bacterial Cu handling. However, there is some ambiguity since neither its biosynthesis nor uptake is Cu-regulated. Furthermore, there is little experimental support for this physiological role of glutathione beyond measuring growth of glutathione-deficient mutants in the presence of Cu. Our work with group A Streptococcus provides new evidence that glutathione increases the threshold of intracellular Cu availability that can be tolerated by bacteria and thus advances fundamental understanding of bacterial Cu handling.

Copper primes adaptation of uropathogenic Escherichia coli to superoxide stress by activating superoxide dismutases

Copper and superoxide are used by the phagocytes to kill bacteria. Copper is a host effector encountered by uropathogenic Escherichia coli (UPEC) during urinary tract infection in a non-human primate model, and in humans. UPEC is exposed to higher levels of copper in the gut prior to entering the urinary tract. Effects of pre-exposure to copper on bacterial killing by superoxide has not been reported. We hypothesized that copper-replete E. coli is more sensitive to killing by superoxide in vitro, and in activated macrophages. We utilized wild-type UPEC strain CFT073, and its isogenic mutants lacking copper efflux systems, superoxide dismutases (SODs), regulators of a superoxide dismutase, and complemented mutants to address this question. Surprisingly, our results reveal that copper protects UPEC against killing by superoxide in vitro. This copper-dependent protection was amplified in the mutants lacking copper efflux systems. Increased levels of copper and manganese were detected in UPEC exposed to sublethal concentration of copper. Copper activated the transcription of sodA in a SoxR- and SoxS-dependent manner resulting in enhanced levels of SodA activity. Importantly, pre-exposure to copper increased the survival of UPEC within RAW264.7 and bone marrow-derived murine macrophages. Loss of SodA, but not SodB or SodC, in UPEC obliterated copper-dependent protection from superoxide in vitro, and from killing within macrophages. Collectively, our results suggest a model in which sublethal levels of copper trigger the activation of SodA and SodC through independent mechanisms that converge to promote the survival of UPEC from killing by superoxide. A major implication of our findings is that bacteria colonizing copper-rich milieus are primed for efficient detoxification of superoxide.

Antimicrobial Susceptibility Testing of Antimicrobial Peptides to Better Predict Efficacy

During the development of antimicrobial peptides (AMP) as potential therapeutics, antimicrobial susceptibility testing (AST) stands as an essential part of the process in identification and optimisation of candidate AMP. Standard methods for AST, developed almost 60 years ago for testing conventional antibiotics, are not necessarily fit for purpose when it comes to determining the susceptibility of microorganisms to AMP. Without careful consideration of the parameters comprising AST there is a risk of failing to identify novel antimicrobials at a time when antimicrobial resistance (AMR) is leading the planet toward a post-antibiotic era. More physiologically/clinically relevant AST will allow better determination of the preclinical activity of drug candidates and allow the identification of lead compounds. An important consideration is the efficacy of AMP in biological matrices replicating sites of infection, e.g., blood/plasma/serum, lung bronchiolar lavage fluid/sputum, urine, biofilms, etc., as this will likely be more predictive of clinical efficacy. Additionally, specific AST for different target microorganisms may help to better predict efficacy of AMP in specific infections. In this manuscript, we describe what we believe are the key considerations for AST of AMP and hope that this information can better guide the preclinical development of AMP toward becoming a new generation of urgently needed antimicrobials.

Copper stress in Staphylococcus aureus leads to adaptive changes in central carbon metabolism

Copper toxicity has been a long-term selection pressure on bacteria due to its presence in the environment and its use as an antimicrobial agent by grazing protozoa, by phagocytic cells of the immune system, and in man-made medical and commercial products. There is recent evidence that exposure to increased copper stress may have been a key driver in the evolution and spread of methicillin-resistant Staphylococcus aureus, a globally important pathogen that causes significant mortality and morbidity worldwide. Yet it is unclear how S. aureus physiology is affected by copper stress or how it adapts in order to be able to grow in the presence of excess copper. Here, we have determined quantitatively how S. aureus alters its proteome during growth under copper stress conditions, comparing this adaptive response in two different types of growth regime. We found that the adaptive response involves induction of the conserved copper detoxification system as well as induction of enzymes of central carbon metabolism, with only limited induction of proteins involved in the oxidative stress response. Further, we identified a protein that binds copper inside S. aureus cells when stressed by copper excess. This copper-binding enzyme, a glyceraldehyde-3-phosphate dehydrogenase essential for glycolysis, is inhibited by copper in vitro and inside S. aureus cells. Together, our data demonstrate that copper stress leads to the inhibition of glycolysis in S. aureus, and that the bacterium adapts to this stress by altering its central carbon utilisation pathways.

A Porcine Model for Urinary Tract Infection

Urinary tract infection (UTI) is the most common bacterial infectious disease with a high frequency of recurrence and the leading cause of septicemia. In vivo experimentation has contributed significantly to the present-day knowledge on UTI pathogenesis. This research has traditionally been based on murine models of UTI. Occasional conflicting results between UTI in mice and humans and increasing skepticism toward small rodent models in general warrant the need of novel large-animal infection models that better resemble the anatomy and physiology of humans, and thus better mimic the course of infection in humans. Here, we report, to our knowledge, the first large-animal model of cystitis. The model is based on pigs, and the protocol supports the establishment of persistent, non-ascending infection in this animal and is established without invasive surgical procedures, pain, and discomfort for the animal. The course of infection is monitored by cystoscopy, microscopy of bladder biopsies, and biochemical analysis of urine and blood samples. At termination, harvested whole bladders from infected pigs are analyzed for microbiological colonization using microscopy, histology, and viable bacterial counts. The model is a useful tool in future studies of UTI pathogenesis and opens up novel possibilities to bridge the current knowledge obtained from small-animal UTI models to UTI pathogenesis in humans.

Analysis of urinary trace element levels in general population of Wuhan in central China

Trace element distribution in the human body varies across regions and countries due to their different living environment and lifestyle. Thus, it is of great significance to investigate the reference level of trace element in a specific population. Wuhan is the largest metropolitan area in central China with highly developed heavy industries. This study aimed at determining the reference urinary distribution in general populations of Wuhan for nine trace elements (Cr, Mn, Cu, As, Se, Cd, Hg, Tl, Pb), and analyzed their associations with age, sex, and the kidney function. In total, 226 healthy adults not exposed to these trace elements were recruited, and the first-morning urine specimens were analyzed by using ICP-MS-based method. Our results showed higher urinary levels for As and Cd in Wuhan population when compared with other countries, while other element levels were almost equivalent. Sex difference existed for urinary Cu, Mn, As, Tl, and Pb. And urinary Cd, Tl, and Pb levels were associated with the glomerular filtration rate. Almost all these urinary elements showed significant inter-correlations, especially for Cu but except for Mn. This study provides systematic information regarding urinary trace element levels in residents of Wuhan in central China, and shall be of importance for future environmental and occupational biomonitoring.

Antimicrobial and Antibiofilm Activities of Helical Antimicrobial Peptide Sequences Incorporating Metal-Binding Motifs

Antimicrobial peptides (AMPs) represent alternative strategies to combat the global health problem of antibiotic resistance. However, naturally occurring AMPs are generally not sufficiently active for use as antibiotics. Optimized synthetic versions incorporating additional design principles are needed. Here, we engineered amino-terminal Cu(II) and Ni(II) (ATCUN) binding motifs, which can enhance biological function, into the native sequence of two AMPs, CM15 and citropin1.1. The incorporation of metal-binding motifs modulated the antimicrobial activity of synthetic peptides against a panel of carbapenem-resistant enterococci (CRE) bacteria, including carbapenem-resistant Klebsiella pneumoniae (KpC+) and Escherichia coli (KpC+). Activity modulation depended on the type of ATCUN variant utilized. Membrane permeability assays revealed that the in silico selected lead template, CM15, and its ATCUN analogs increased bacterial cell death. Mass spectrometry, circular dichroism, and molecular dynamics simulations indicated that coordinating ATCUN derivatives with Cu(II) ions did not increase the helical tendencies of the AMPs. CM15 ATCUN variants, when combined with Meropenem, streptomycin, or chloramphenicol, showed synergistic effects against E. coli (KpC+ 1812446) biofilms. Motif addition also reduced the hemolytic activity of the wild-type AMP and improved the survival rate of mice in a systemic infection model. The dependence of these bioactivities on the particular amino acids of the ATCUN motif highlights the possible use of size, charge, and hydrophobicity to fine-tune AMP biological function. Our data indicate that incorporating metal-binding motifs into peptide sequences leads to synthetic variants with modified biological properties. These principles may be applied to augment the activities of other peptide sequences.

Differential Susceptibility of Mycoplasma and Ureaplasma Species to Compound-Enhanced Copper Toxicity

Rationale

Mycoplasmas represent important etiologic agents of many human diseases. Due to increasing antimicrobial resistance and slow rate of novel discovery, unconventional methods of drug discovery are necessary. Copper ions are utilized in host microbial killing, and bacteria must regulate intracellular Cu concentrations to avoid toxicity. We hypothesized that human mollicutes may have susceptibility to Cu-induced toxicity, and compounds that augment copper-dependent killing.

Methods

Mycoplasma pneumoniae (Mpn), Ureaplasma parvum (Up), Ureaplasma urealyticum (Uu), and Mycoplasma hominis (Mh) were exposed to CuSO₄ to determine minimal inhibitory concentrations (MICs). Once inhibitory concentrations had been determined, bacteria were treated with an FDA-approved drug disulfiram (DSF), glyoxal bis(4-methyl-3-thiosemicarbazone) (GTSM), and 2,9-dimethyl-1,10-phenanthroline (neocuproine), with or without Cu²⁺, to determine compound MICs.

Results

Ureaplasma species and Mh were able to tolerate 30–60 μM CuSO₄, while Mpn tolerated over 10-fold higher concentrations (>1 mM). GTSM inhibited growth of all four organisms, but was unaffected by Cu²⁺ addition. Inhibition by GTSM was reduced by addition of the cell-impermeant Cu chelator, bathocuproine disulfonate (BCS). Neocuproine exhibited Cu-dependent growth inhibition of all organisms. DSF exhibited Cu-dependent growth inhibition against Mh at low micromolar concentrations, and at intermediate concentrations for Mpn.

Conclusion

MICs for CuSO₄ differ widely among human mollicutes, with higher MICs for Mpn compared to Mh, Uu, and Up. DSF and Neocuproine exhibit Cu-dependent inhibition of mollicutes with copper concentrations between 25 and 50 μM. GTSM has copper-dependent anti-microbial activity at low levels of copper. Drug enhanced copper toxicity is a promising avenue for novel therapeutic development research with Mycoplasma and Ureaplasma species.

Uropathogenic Escherichia coli employs both evasion and resistance to subvert innate immune-mediated zinc toxicity for dissemination

Uropathogenic Escherichia coli (UPEC) is responsible for most urinary tract infections and is also a frequent cause of sepsis, thus necessitating an understanding of UPEC-mediated subversion of innate immunity. The role of zinc in the innate immune response against UPEC infection, and whether this pathogen counters this response, has not been examined. Here we demonstrate, both in vitro and in vivo, that UPEC both evades and resists innate immune-mediated zinc toxicity to persist and disseminate within the host. Moreover, we have defined the set of UPEC genes conferring zinc resistance and have developed highly selective E. coli reporter systems to track zinc toxicity. These innovative approaches substantially enhance our understanding of immune-mediated metal ion toxicity and bacterial pathogenesis.

Toll-like receptor (TLR)-inducible zinc toxicity is a recently described macrophage antimicrobial response used against bacterial pathogens. Here we investigated deployment of this pathway against uropathogenic Escherichia coli (UPEC), the major cause of urinary tract infections. Primary human macrophages subjected EC958, a representative strain of the globally disseminated multidrug-resistant UPEC ST131 clone, to zinc stress. We therefore used transposon-directed insertion site sequencing to identify the complete set of UPEC genes conferring protection against zinc toxicity. Surprisingly, zinc-susceptible EC958 mutants were not compromised for intramacrophage survival, whereas corresponding mutants in the nonpathogenic E. coli K-12 strain MG1655 displayed significantly reduced intracellular bacterial loads within human macrophages. To investigate whether the intramacrophage zinc stress response of EC958 reflected the response of only a subpopulation of bacteria, we generated and validated reporter systems as highly specific sensors of zinc stress. Using these tools we show that, in contrast to MG1655, the majority of intramacrophage EC958 evades the zinc toxicity response, enabling survival within these cells. In addition, EC958 has a higher tolerance to zinc than MG1655, with this likely being important for survival of the minor subset of UPEC cells exposed to innate immune-mediated zinc stress. Indeed, analysis of zinc stress reporter strains and zinc-sensitive mutants in an intraperitoneal challenge model in mice revealed that EC958 employs both evasion and resistance against zinc toxicity, enabling its dissemination to the liver and spleen. We thus demonstrate that a pathogen of global significance uses multiple mechanisms to effectively subvert innate immune-mediated zinc poisoning for systemic spread.

Manganese acquisition is essential for virulence of Enterococcus faecalis

Manganese (Mn) is an essential micronutrient that is not readily available to pathogens during infection due to an active host defense mechanism known as nutritional immunity. To overcome this nutrient restriction, bacteria utilize high-affinity transporters that allow them to compete with host metal-binding proteins. Despite the established role of Mn in bacterial pathogenesis, little is known about the relevance of Mn in the pathophysiology of E. faecalis. Here, we identified and characterized the major Mn acquisition systems of E. faecalis. We discovered that the ABC-type permease EfaCBA and two Nramp-type transporters, named MntH1 and MntH2, work collectively to promote cell growth under Mn-restricted conditions. The simultaneous inactivation of EfaCBA, MntH1 and MntH2 (ΔefaΔmntH1ΔmntH2 strain) led to drastic reductions (>95%) in cellular Mn content, severe growth defects in body fluids (serum and urine) ex vivo, significant loss of virulence in Galleria mellonella, and virtually complete loss of virulence in rabbit endocarditis and murine catheter-associated urinary tract infection (CAUTI) models. Despite the functional redundancy of EfaCBA, MntH1 and MntH2 under in vitro or ex vivo conditions and in the invertebrate model, dual inactivation of efaCBA and mntH2 (ΔefaΔmntH2 strain) was sufficient to prompt maximal sensitivity to calprotectin, a Mn- and Zn-chelating host antimicrobial protein, and for the loss of virulence in mammalian models. Interestingly, EfaCBA appears to play a prominent role during systemic infection, whereas MntH2 was more important during CAUTI. The different roles of EfaCBA and MntH2 in these sites could be attributed, at least in part, to the differential expression of efaA and mntH2 in cells isolated from hearts or from bladders. Collectively, this study demonstrates that Mn acquisition is essential for the pathogenesis of E. faecalis and validates Mn uptake systems as promising targets for the development of new antimicrobials.

The iron hand of uropathogenic Escherichia coli: the role of transition metal control in virulence

The role of iron as a critical nutrient in pathogenic bacteria is widely regarded as having driven selection for iron acquisition systems among uropathogenic Escherichia coli (UPEC) isolates. Carriage of multiple transition metal acquisition systems in UPEC suggests that the human urinary tract manipulates metal-ion availability in many ways to resist infection. For siderophore systems in particular, recent studies have identified new roles for siderophore copper binding as well as production of siderophore-like inhibitors of iron uptake by other, competing bacterial species. Among these is a process of nutritional passivation of metal ions, in which uropathogens access these vital nutrients while simultaneously protecting themselves from their toxic potential. Here, we review these new findings within the current understanding of UPEC transition metal acquisition.

A horizontally gene transferred copper resistance locus confers hyper-resistance to antibacterial copper toxicity and enables survival of community acquired methicillin resistant Staphylococcus aureus USA300 in macrophages

Excess copper is highly toxic and forms part of the host innate immune system's antibacterial arsenal, accumulating at sites of infection and acting within macrophages to kill engulfed pathogens. We show for the first time that a novel, horizontally gene transferred copper resistance locus (copXL), uniquely associated with the SCCmec elements of the highly virulent, epidemic, community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) USA300, confers copper hyper-resistance. These genes are additional to existing core genome copper resistance mechanisms, and are not found in typical S. aureus lineages, but are increasingly identified in emerging pathogenic isolates. Our data show that CopX, a putative P_1B-3 -ATPase efflux transporter, and CopL, a novel lipoprotein, confer copper hyper-resistance compared to typical S. aureus strains. The copXL genes form an operon that is tightly repressed in low copper environments by the copper regulator CsoR. Significantly, CopX and CopL are important for S. aureus USA300 intracellular survival within macrophages. Therefore, the emergence of new S. aureus clones with the copXL locus has significant implications for public health because these genes confer increased resistance to antibacterial copper toxicity, enhancing bacterial fitness by altering S. aureus interaction with innate immunity.

Copper Ions and Coordination Complexes as Novel Carbapenem Adjuvants

Carbapenem-resistant Enterobacteriaceae are urgent threats to global human health. These organisms produce β-lactamases with carbapenemase activity, such as the metallo-β-lactamase NDM-1, which is notable due to its association with mobile genetic elements and the lack of a clinically useful inhibitor. Here we examined the ability of copper to inhibit the activity of NDM-1 and explored the potential of a copper coordination complex as a mechanism to efficiently deliver copper as an adjuvant in clinical therapeutics. An NDM-positive Escherichia coli isolate, MS6192, was cultured from the urine of a patient with a urinary tract infection. MS6192 was resistant to antibiotics from multiple classes, including diverse β-lactams (penicillins, cephalosporins, and carbapenems), aminoglycosides, and fluoroquinolones. In the presence of copper (range, 0 to 2 mM), however, the susceptibility of MS6192 to the carbapenems ertapenem and meropenem increased markedly. In standard checkerboard assays, copper decreased the MICs of ertapenem and meropenem against MS6192 in a dose-dependent manner, suggesting a synergistic mode of action. To examine the inhibitory effect of copper in the absence of other β-lactamases, the bla_NDM-1 gene from MS6192 was cloned and expressed in a recombinant E. coli K-12 strain. Analysis of cell extracts prepared from this strain revealed that copper directly inhibited NDM-1 activity, which was confirmed using purified recombinant NDM-1. Finally, delivery of copper at a low concentration of 10 μM by using the FDA-approved coordination complex copper-pyrithione sensitized MS6192 to ertapenem and meropenem in a synergistic manner. Overall, this work demonstrates the potential use of copper coordination complexes as novel carbapenemase adjuvants.

Effects of age and gender on reference levels of biomarkers comprising the pediatric Renal Activity Index for Lupus Nephritis (p-RAIL)

BACKGROUND

Systemic Lupus Erythematosus (SLE) is a multisystem autoimmune disease that disproportionately effects women and children of minorities. Renal involvement (lupus nephritis, or LN) occurs in up to 80% of children with SLE and is a major determinant of poor prognosis. We have developed a non-invasive pediatric Renal Activity Index for Lupus (p-RAIL) that consists of laboratory measures that reflect histologic LN activity. These markers are neutrophil gelatinase associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), monocyte chemotactic protein (MCP-1), adiponectin (APN), ceruloplasmin (CP) and hemopexin (HPX). A major gap in the knowledge base and a barrier to clinical utility is how these markers behave in healthy children. We set out to establish a reference range for the p-RAIL markers in a population of healthy children, and to determine if levels of these markers fluctuate with age or gender.

METHODS

Urine was collected from 368 healthy children presenting to Cincinnati Children's primary care clinic for well child visits and assayed for NGAL, KIM-1, MCP-1, APN, CP and HPX using commercially available kits or assay materials.

RESULTS

Specimens were grouped by age (0-5 years (n = 94); 5-10 (n = 89); 10-15 (n = 93); 15-20 (n = 91)) and gender (M = 184, F = 184). For age and gender comparisons, values were log transformed prior to analysis. The medians (minimums, maximums) of each marker in the combined population were as follows: NGAL 6.65 (0.004, 391.52) ng/ml, KIM-1416.84 (6.22, 2512.43) pg/ml, MCP-1209.36 (9.49, 2237.06) pg/ml, APN 8.05 (0.07, 124.50) ng/ml, CP 465.15 (8.02, 7827.00) ng/ml, HPX 588.70 (6.85, 17,658.40)ng/ml. All p-RAIL biomarkers but adiponectin had weak but significant positive correlations with age, with NGAL being the strongest (r = 0.33, p < 0.001). For gender comparisons, NGAL, CP and HPX were elevated in females vs males (86%, p < 0.0001; 3%, p = 0.007, and 5%, p = 0.0005 elevation of the log transformed mean, respectively).

CONCLUSIONS

We have established a reference range for the p-RAIL biomarkers and have highlighted age and gender differences. This information is essential for rational interpretation of studies and clinical trials utilizing the p-RAIL algorithm.

Host and Pathogen Copper-Transporting P-Type ATPases Function Antagonistically during Salmonella Infection

Copper is an essential yet potentially toxic trace element that is required by all aerobic organisms. A key regulator of copper homeostasis in mammalian cells is the copper-transporting P-type ATPase ATP7A, which mediates copper transport from the cytoplasm into the secretory pathway, as well as copper export across the plasma membrane. Previous studies have shown that ATP7A-dependent copper transport is required for killing phagocytosed Escherichia coli in a cultured macrophage cell line. In this investigation, we expanded on these studies by generating Atp7a^LysMcre mice, in which the Atp7a gene was specifically deleted in cells of the myeloid lineage, including macrophages. Primary macrophages isolated from Atp7a^LysMcre mice exhibit decreased copper transport into phagosomal compartments and a reduced ability to kill Salmonella enterica serovar Typhimurium compared to that of macrophages isolated from wild-type mice. The Atp7a^LysMcre mice were also more susceptible to systemic infection by S Typhimurium than wild-type mice. Deletion of the S Typhimurium copper exporters, CopA and GolT, was found to decrease infection in wild-type mice but not in the Atp7a^LysMcre mice. These studies suggest that ATP7A-dependent copper transport into the phagosome mediates host defense against S Typhimurium, which is counteracted by copper export from the bacteria via CopA and GolT. These findings reveal unique and opposing functions for copper transporters of the host and pathogen during infection.

Genome-wide transposon mutagenesis of Proteus mirabilis: Essential genes, fitness factors for catheter-associated urinary tract infection, and the impact of polymicrobial infection on fitness requirements

The Gram-negative bacterium Proteus mirabilis is a leading cause of catheter-associated urinary tract infections (CAUTIs), which are often polymicrobial. Numerous prior studies have uncovered virulence factors for P. mirabilis pathogenicity in a murine model of ascending UTI, but little is known concerning pathogenesis during CAUTI or polymicrobial infection. In this study, we utilized five pools of 10,000 transposon mutants each and transposon insertion-site sequencing (Tn-Seq) to identify the full arsenal of P. mirabilis HI4320 fitness factors for single-species versus polymicrobial CAUTI with Providencia stuartii BE2467. 436 genes in the input pools lacked transposon insertions and were therefore concluded to be essential for P. mirabilis growth in rich medium. 629 genes were identified as P. mirabilis fitness factors during single-species CAUTI. Tn-Seq from coinfection with P. stuartii revealed 217/629 (35%) of the same genes as identified by single-species Tn-Seq, and 1353 additional factors that specifically contribute to colonization during coinfection. Mutants were constructed in eight genes of interest to validate the initial screen: 7/8 (88%) mutants exhibited the expected phenotypes for single-species CAUTI, and 3/3 (100%) validated the expected phenotypes for polymicrobial CAUTI. This approach provided validation of numerous previously described P. mirabilis fitness determinants from an ascending model of UTI, the discovery of novel fitness determinants specifically for CAUTI, and a stringent assessment of how polymicrobial infection influences fitness requirements. For instance, we describe a requirement for branched-chain amino acid biosynthesis by P. mirabilis during coinfection due to high-affinity import of leucine by P. stuartii. Further investigation of genes and pathways that provide a competitive advantage during both single-species and polymicrobial CAUTI will likely provide robust targets for therapeutic intervention to reduce P. mirabilis CAUTI incidence and severity.

Proteus mirabilis is a common cause of single-species and polymicrobial catheter-associated urinary tract infections (CAUTIs). Prior studies have uncovered P. mirabilis virulence factors for single-species ascending UTI, but little is known concerning pathogenesis during CAUTI or polymicrobial infection. Using transposon insertion-site sequencing (Tn-Seq), we performed a global assessment of P. mirabilis fitness factors for CAUTI while simultaneously determining how coinfection with another CAUTI pathogen, Providencia stuartii, alters P. mirabilis fitness requirements. This approach provides six important contributions to the field: 1) the first global estimation of P. mirabilis genes essential for growth, 2) validation of a role for known P. mirabilis fitness factors during CAUTI, 3) identification of novel fitness factors, 4) identification of core fitness factors for both single-species and polymicrobial CAUTI, 5) identification of single-species fitness factors that are complemented during polymicrobial infection, and 6) identification of factors that only provide a competitive advantage during polymicrobial infection. We further demonstrate that the CAUTI model can be used to examine the interplay between fitness requirements of both species during coinfection. Investigation of fitness requirements for other pathogens during single-species and polymicrobial CAUTI will elucidate complex interactions that contribute to disease severity and uncover conserved targets for therapeutic intervention.