ESKAPEE pathogens newly released from biofilm residence by a targeted monoclonal are sensitized to killing by traditional antibiotics

Unveiling the potential of a novel drug efflux pump inhibitor to combat multidrug resistance in ESKAPEE pathogens, with a focus on Acinetobacter baumannii

ESKAPEE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli) is a group of nosocomial pathogens with alarming antibiotic resistance, representing a paramount public health menace. Their multidrug resistance (MDR) is often due to hyperactive drug efflux transporters (DETs) exporting antibiotics from bacterial cells. Fortunately, a breakthrough has been made by the synthetic molecule KSA5_1 (8,10-dimethyl-1,6,11-triazatetracene-5,12-dione). In vitro combination assays of KSA5_1 with antibiotics (colistin, ciprofloxacin, gentamicin) showed excellent reductions in minimum inhibitory concentrations (MICs), as much as 512-fold, against clinical MDR isolates such as Enterococcus faecium, Staphylococcus aureus and Acinetobacter baumannii. Surprisingly, KSA5_1 was more effective than the standard efflux pump inhibitor PAβN in inhibiting ciprofloxacin efflux from A. baumannii, primarily targeting the overexpressed AdeG gene, a key DET protein. Molecular docking and simulations indicated the improved binding of KSA5_1 to AdeG with a suggestion of tight DET inhibition. KSA5_1 also possessed good drug-like profiles. The improved physicochemical profile of the compound and the potential to increase the efficacy of antibiotics by inhibiting DETs offer KSA5_1 an exciting lead to combat antimicrobial resistance (AMR). The new approach promises to address the challenging issue of MDR among ESKAPEE pathogens and has the potential to restore the efficacy of existing antibiotics to combat the AMR crisis.

Characterization and therapeutic potential of phage vB_Eco_ZCEC08 against multidrug-resistant uropathogenic Escherichia coli

BACKGROUND

Urinary tract infections (UTIs) caused by antibiotic-resistant bacteria have become a significant public health concern. The increasing ineffectiveness of antibiotics has led to a renewed focus on investigating other strategies, such as bacteriophages, to target specific pathogenic bacteria and prevent future resistance.

RESULTS

This study reports the isolation and characterization of bacteriophage vB_Eco_ZCEC08 targeting uropathogenic Escherichia coli (UPEC). Phage vB_Eco_ZCEC08 is morphologically a non-contractile tailed phage that exhibits strong lytic activity against UPEC with a short latent period of less than 15 min and a lysis time of 20 min to produce a high burst of around 900 phage particles per host cell. vB_Eco_ZCEC08 phage activity demonstrated exceptional stability against temperature [-80-60 ̊C], pH [2-11], UV exposure and incubation in artificial human urine. The phage effectively reduced UPEC counts over a range of infection rates, with MOI 1 the most effective, and which resulted in the limited emergence of phage-insensitive bacteria. A whole-genome study of the 47.926 bp vB_Eco_ZCEC08 phage identified one tRNA gene and 84 predicted genes. Comparative genomics and phylogenetic analysis suggest that the vB_Eco_ZCEC08 phage belongs to the same genus as the Salmonella phage vB_SenS_ST1 but represents a new species. Phage vB_Eco_ZCEC08 showed minimal cytotoxicity against human urinary bladder cancer and skin fibroblast cell lines.

CONCLUSION

vB_Eco_ZCEC08 phage demonstrates strong selective lytic activity against UPEC in the absence of any lysogenic behavior. These properties coupled with inherent physiochemical stability and low cytotoxicity support the development of vB_Eco_ZCEC08 as an alternative treatment for multidrug-resistant UPEC.

Polyacrylamide-Based Antimicrobial Copolymers to Replace or Rescue Antibiotics

Antibiotics save countless lives each year and have dramatically improved human health outcomes since their introduction in the 20th century. Unfortunately, bacteria are now developing resistance to antibiotics at an alarming rate, with many new strains of "superbugs" showing simultaneous resistance to multiple classes of antibiotics. To mitigate the global burden of antimicrobial resistance, we must develop new antibiotics that are broadly effective, safe, and highly stable to enable global access. In this manuscript, we report the development of polyacrylamide-based copolymers as a class of broad-spectrum antibiotics with efficacy against several critical pathogens. We demonstrate that these copolymer drugs are selective for bacteria over mammalian cells, indicating a favorable safety profile. We show that they kill bacteria through a membrane disruption mechanism, which allows them to overcome traditional mechanisms of antimicrobial resistance. Finally, we demonstrate their ability to rehabilitate an existing small-molecule antibiotic that is highly subject to resistance development by improving its potency and eliminating the development of resistance in a combination treatment. This work represents a significant step toward combating antimicrobial resistance.

Mycobacterium abscessus biofilm cleared from murine lung by monoclonal antibody against bacterial DNABII proteins

BACKGROUND

Pulmonary infections with multidrug-resistant nontuberculous mycobacteria (NTM), particularly Mycobacterium abscessus (MAB), are increasingly more prevalent in individuals with lung disease such as cystic fibrosis and are extremely difficult to treat. Protracted antibiotic therapies consist of multidrug regimens that last for months to years. Despite these intense protocols, failure rates are high with 50%-60% of patients not achieving a sustained culture-negative status. A major contributor to the difficult medical management of NTM infections is formation of pulmonary aggregate MAB biofilms which protect the resident bacteria from antimicrobials and host immune effectors. Thereby, novel and more effective approaches to combat recalcitrant NTM infections are urgently needed.

METHODS

We developed an epitope-targeted monoclonal antibody-based technology to rapidly disrupt biofilms and release resident bacteria into a transient yet highly vulnerable phenotype that is significantly more sensitive to killing by both antibiotics and host innate immune effectors (e.g., PMNs and antimicrobial peptides). Herein, we tested this technology in a pre-clinical murine lung infection model to determine whether this treatment would mediate clearance of MAB from the lungs and speed return to homeostasis.

RESULTS

As early as 48 h after a single treatment, bacterial loads were reduced to below the level of detection and histopathologic analysis showed markedly decreased inflammation and rapid eradication of aggregate biofilms compared to controls.

CONCLUSIONS

These new data add to those from multiple prior published studies which show the significant efficacy of this novel therapeutic approach to resolve recalcitrant bacterial biofilm diseases, now potentially including those induced by NTM.

Association of opportunistic bacterial pathogens with female infertility: A case-control study

AIM

Infertility affects a significant proportion of women worldwide, and the colonization of certain vaginal pathogens has been suggested as a possible contributing factor. To explore the relationship between bacterial pathogens and female infertility, a case-control study was conducted involving 55 infertile women as cases and 5 fertile women as controls.

METHOD

Conventional culture-based techniques and biochemical assays followed by 16S rDNA sequence analysis were employed for the identification of vaginal isolates from the two groups. The strength of association between the isolated bacterium and infecundity was derived by odds ratio calculation.

RESULTS

The investigation revealed the presence of bacteria including Enterococcus faecalis, Escherichia coli, Bacillus spp., Acinetobacter baumannii, Pseudomonas spp., Micrococcus luteus, Staphylococcus aureus, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus capitis, Staphylococcus epidermidis, and Staphylococcus saprophyticus in the vaginal swabs of infertile women. Of these, the odds ratios for Staphylococcus aureus, Klebsiella pneumoniae, E. faecalis, and E. coli were 5.43 (95% CI = 0.28, 103.49), 4.59 (95% CI = 0.24, 87.93), 2.25 (95% CI = 0.11, 44.16), and 1.70 (95% CI = 0.09, 34.01), respectively, displaying an association with infertility. Moreover, vaginal colonization of these four bacterial species was also dominant in cases that were diagnosed with pelvic inflammatory disease and idiopathic infertility by laparoscopic examination.

CONCLUSION

Overall, the findings of this study indicate a probable association between specific pathogenic microorganisms and women's barrenness, emphasizing the significant role of these disease-causing agents in hindering conception. This highlights the significance of a complete understanding of the vaginal microbiome and emphasizes further research in this area.

An engineered peptide derived from the innate immune effector high-mobility group box 1 disrupts and prevents dual-genera biofilms formed by common respiratory tract pathogens

Bacterial biofilms mediate chronic and recurrent bacterial infections that are extremely difficult to treat by currently available standards of care. In nature, these encased bacterial communities are typically comprised of more than one genus or species. Specifically, in the airway, nontypeable Haemophilus influenzae (NTHI) predominates and is commonly isolated with one or more of the following co-pathogens with which it forms unique relationships: methicillin-resistant Staphylococcus aureus, Burkholderia cenocepacia, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Moraxella catarrhalis. We recently showed that dual-genera biofilms comprised of NTHI plus a co-pathogen are disrupted when the biofilm matrix is destabilized by a pathogen-directed strategy that uses a humanized monoclonal antibody directed against the protective domains of bacterial DNABII proteins found at vertices of crossed strands of eDNA within the biofilm matrix. We also recently showed that a peptide synthesized from the host innate immune effector High Mobility Group Box 1 (HMGB1), called mB Box-97syn, competitively inhibits binding of the bacterial DNABII proteins to eDNA, which thereby also destabilizes single-species biofilms to release biofilm-resident bacteria into a transient yet highly vulnerable state that is more effectively cleared by the host innate immune system and/or antibiotics. Here, we expanded upon these studies to assess the ability of host-augmenting mB Box-97syn to both disrupt two-genera biofilms formed by NTHI plus a common co-pathogen, and prevent their formation. Disruption of established two-genera biofilms ranged from 57% to 88%, whereas prevention of two-genera biofilm formation ranged from 65% to 80% (P = .002 to P < .0001). The sobering recalcitrance of chronic and recurrent respiratory tract infections, combined with growing global concern of antimicrobial resistance (AMR), demands development of more effective management and prevention options. Ideally, novel treatment strategies would both target the pathogens and augment the host's natural abilities to eradicate them. Herein, we provide additional data to support continued development of the latter concept via demonstration of mB Box-97syn's efficacy against polymicrobial biofilms.

Computational Design of Pore-Forming Peptides with Potent Antimicrobial and Anticancer Activities

Peptides that form transmembrane barrel-stave pores are potential alternative therapeutics for bacterial infections and cancer. However, their optimization for clinical translation is hampered by a lack of sequence-function understanding. Recently, we have de novo designed the first synthetic barrel-stave pore-forming antimicrobial peptide with an identified function of all residues. Here, we systematically mutate the peptide to improve pore-forming ability in anticipation of enhanced activity. Using computer simulations, supported by liposome leakage and atomic force microscopy experiments, we find that pore-forming ability, while critical, is not the limiting factor for improving activity in the submicromolar range. Affinity for bacterial and cancer cell membranes needs to be optimized simultaneously. Optimized peptides more effectively killed antibiotic-resistant ESKAPEE bacteria at submicromolar concentrations, showing low cytotoxicity to human cells and skin model. Peptides showed systemic anti-infective activity in a preclinical mouse model of Acinetobacter baumannii infection. We also demonstrate peptide optimization for pH-dependent antimicrobial and anticancer activity.

ClpP Peptidase as a Plausible Target for the Discovery of Novel Antibiotics

Antimicrobial resistance (AMR) to currently available antibiotics/drugs is a global threat. It is desirable to develop new drugs that work through a novel target(s) to avoid drug resistance. This review discusses the potential of the caseinolytic protease P (ClpP) peptidase complex as a novel target for finding novel antibiotics, emphasising the ClpP's structure and function. ClpP contributes to the survival of bacteria via its ability to destroy misfolded or aggregated proteins. In consequence, its inhibition may lead to microbial death. Drugs inhibiting ClpP activity are currently being tested, but no drug against this target has been approved yet. It was demonstrated that Nblocked dipeptides are essential for activating ClpP's proteolytic activity. Hence, compounds mimicking these dipeptides could act as inhibitors of the formation of an active ClpP complex. Drugs, including Bortezomib, Cisplatin, Cefmetazole, and Ixazomib, inhibit ClpP activation. However, they were not approved as drugs against the target because of their high toxicity, likely due to the presence of strong electrophiles in their warheads. The modifications of these warheads could be a good strategy to reduce the toxicity of these molecules. For instance, a boronate warhead was replaced by a chloromethyl ketone, and this new molecule was shown to exhibit selectivity for prokaryotic ClpP. A better understanding of the structure and function of the ClpP complex would benefit the search for compounds mimicking N-blocked dipeptides that would inhibit ClpP complex activity and cause bacterial death.

Disruption of nontuberculous mycobacteria biofilms induces a highly vulnerable to antibiotic killing phenotype

Objectives

Structural or mucus hypersecretory pulmonary diseases such as cystic fibrosis (CF), wherein viscous mucus accumulates and clearance functions are impaired, predispose people to lung infection by inhaled bacteria that form biofilm aggregates. Nontuberculous mycobacteria (NTM), primarily Mycobacterium abscessus and Mycobacterium avium, are the growing cause of these lung infections and are extremely challenging to treat due to antibiotic recalcitrance. Better therapeutic approaches are urgently needed. We developed a humanized monoclonal antibody (HuTipMab) directed against a biofilm structural linchpin, the bacterial DNABII proteins, that rapidly disrupts biofilms and generates highly vulnerable newly released bacteria (NRel).

Methods

HuTipMab's ability to recognize HupB, NTM's DNABII homologue was determined by ELISA. Relative ability of HuTipMab to disrupt biofilms formed by lab-passaged and clinical isolates of NTM was assessed by CLSM. Relative sensitivity of NTM NRel to antibiotic killing compared to when grown planktonically was evaluated by plate count.

Results

HuTipMab recognized HupB and significantly disrupted NTM biofilms in a time- and dose-dependent manner. Importantly, NTM NRel of lab-passaged and clinical isolates were now highly sensitive to killing by amikacin and azithromycin.

Conclusions

If successful, this combinatorial treatment strategy would empower existing antibiotics to more effectively kill NTM newly released from a biofilm by HuTipMab and thereby both improve clinical outcomes and perhaps decrease length of antibiotic treatment for people that are NTM culture-positive.

Nontypeable Haemophilus influenzae released from biofilm residence by monoclonal antibody directed against a biofilm matrix component display a vulnerable phenotype

Bacterial biofilms contribute significantly to pathogenesis, recurrence and/or chronicity of the majority of bacterial diseases due to their notable recalcitrance to clearance. Herein, we examined kinetics of the enhanced sensitivity of nontypeable Haemophilus influenzae (NTHI) newly released (NRel) from biofilm residence by a monoclonal antibody against a bacterial DNABII protein (α-DNABII) to preferential killing by a β-lactam antibiotic. This phenotype was detected within 5 min and lasted for ~ 6 h. Relative expression of genes selected due to their known involvement in sensitivity to a β-lactam showed transient up-regulated expression of penicillin binding proteins by α-DNABII NTHI NRel, whereas there was limited expression of the β-lactamase precursor. Transient down-regulated expression of mediators of oxidative stress supported similarly timed vulnerability to NADPH-oxidase sensitive intracellular killing by activated human PMNs. Further, transient up-regulated expression of the major NTHI porin aligned well with observed increased membrane permeability of α-DNABII NTHI NRel, a characteristic also shown by NRel of three additional pathogens. These data provide mechanistic insights as to the transient, yet highly vulnerable, α-DNABII NRel phenotype. This heightened understanding supports continued validation of this novel therapeutic approach designed to leverage knowledge of the α-DNABII NRel phenotype for more effective eradication of recalcitrant biofilm-related diseases.