In vitro and in vivo activities of the carbonic anhydrase inhibitor, dorzolamide, against vancomycin-resistant enterococci

Development of Penicillin-Based Carbonic Anhydrase Inhibitors Targeting Multidrug-Resistant Neisseria gonorrhoeae

The development of antibacterial drugs with new mechanisms of action is crucial in combating the rise of antibiotic-resistant infections. Bacterial carbonic anhydrases (CAs, EC 4.2.1.1) have been validated as promising antibacterial targets against pathogens such as Helicobacter pylori, Neisseria gonorrhoeae, and vancomycin-resistant enterococci. A multitarget strategy is proposed to design penicillin-based CA inhibitor hybrids for tackling resistance by targeting multiple bacterial pathways, thereby resensitizing drug-resistant strains to clinical antibiotics. The sulfonamide derivatives potently inhibited the CAs from N. gonorrhoeae and Escherichia coli with KI values in the range of 7.1-617.2 nM. Computational simulations with the main penicillin-binding protein (PBP) of N. gonorrhoeae indicated that these hybrid derivatives maintained the mechanism of action of the lead β-lactams. A subset of derivatives showed potent PBP-related antigonococcal effects against multidrug-resistant N. gonorrhoeae strains, with several compounds significantly outperforming both the lead β-lactam and CA inhibitor drugs (MIC values in the range 0.25 to 0.5 μg/mL).

Drug interactions of carbonic anhydrase inhibitors and activators

INTRODUCTION

Carbonic anhydrases (CAs, EC 4.2.1.1) have been established drug targets for decades, with their inhibitors and activators possessing relevant pharmacological activity and applications in various fields. At least 11 sulfonamides/sulfamates are clinically used as diuretics, antiglaucoma, antiepileptic, or antiobesity agents and one derivative, SLC-0111, is in clinical trials as antitumor/antimetastatic agent. The activators were less investigated with no clinically used agent.

AREAS COVERED

Drug interactions between CA inhibitors/activators and various other agents are reviewed in publications from the period March 2020 - January 2024.

EXPERT OPINION

Drug interactions involving these agents revealed several interesting findings. Acetazolamide plus loop diuretics is highy effective in acute decompensated heart failure, whereas ocular diseases such as X-linked retinoschisis and macular edema were treated by acetazolamide plus bevacizumab or topical NSAIDs. Potent anti-infective effects of acetazolamide and other CAIs, alone or in combination with other agents were demonstrated for the management of Neisseria gonorrhoea, vancomycin resistant enterococci, Acanthamoeba castellanii, Trichinella spiralis, and Cryptococcus neoformans infections. Topiramate, in combination with phentermine is incresingly used for the management of obesity, whereas zonisamide plus levodopa is highly effective for Parkinson's disease. Acetazolamide, methazolamide, ethoxzolamide, and SLC-0111 showed synergistic antitumor/antimetastatic action in combination with many other antitumor drugs.

Benzothiadiazinone-1,1-Dioxide Carbonic Anhydrase Inhibitors Suppress the Growth of Drug-Resistant Mycobacterium tuberculosis Strains

2H-Benzo[e][1,2,4]thiadiazin-3(4H)-one 1,1-dioxide (BTD) based carbonic anhydrase (CA) inhibitors are here explored as new anti-mycobacterial agents. The chemical features of BTD derivatives meet the criteria for a potent inhibition of β-class CA isozymes. BTD derivatives show chemical features meeting the criteria for a potent inhibition of β-class CA isozymes. Specifically, three β-CAs (MtCA1, MtCA2, and MtCA3) were identified in Mycobacterium tuberculosis and their inhibition was shown to exert an antitubercular action. BTDs derivatives 2a-q effectively inhibited the mycobacterial CAs, especially MtCA2 and MtCA3, with Ki values up to a low nanomolar range (MtCA3, Ki = 15.1-2250 nM; MtCA2, Ki = 38.1-4480 nM) and with a significant selectivity ratio over the off-target human CAs I and II. A computational study was conducted to elucidate the compound structure-activity relationship. Importantly, the most potent MtCA inhibitors demonstrated efficacy in inhibiting the growth of M. tuberculosis strains resistant to both rifampicin and isoniazid-standard reference drugs for Tuberculosis treatment.

Novel Drug Screening Assay for Acanthamoeba castellanii and the Anti-Amoebic Effect of Carbonic Anhydrase Inhibitors

Acanthamoeba castellanii is an amoeba that inhabits soil and water in every part of the world. Acanthamoeba infection of the eye causes keratitis and can lead to a loss of vision. Current treatment options are only moderately effective, have multiple harmful side effects, and are tedious. In our study, we developed a novel drug screening method to define the inhibitory properties of potential new drugs against A. castellanii in vitro. We found that the clinically used carbonic anhydrase inhibitors, acetazolamide, ethoxzolamide, and dorzolamide, have promising antiamoebic properties.

Selected strategies to fight pathogenic bacteria

Natural products and analogues are a source of antibacterial drug discovery. Considering drug resistance levels emerging for antibiotics, identification of bacterial metalloenzymes and the synthesis of selective inhibitors are interesting for antibacterial agent development. Peptide nucleic acids are attractive antisense and antigene agents representing a novel strategy to target pathogens due to their unique mechanism of action. Antisense inhibition and development of antisense peptide nucleic acids is a new approach to antibacterial agents. Due to the increased resistance of biofilms to antibiotics, alternative therapeutic options are necessary. To develop antimicrobial strategies, optimised in vitro and in vivo models are needed. In vivo models to study biofilm-related respiratory infections, device-related infections: ventilator-associated pneumonia, tissue-related infections: chronic infection models based on alginate or agar beads, methods to battle biofilm-related infections are discussed. Drug delivery in case of antibacterials often is a serious issue therefore this review includes overview of drug delivery nanosystems.

Inhibition of pathogenic bacterial carbonic anhydrases by monothiocarbamates

Carbonic anhydrases (CAs) from the pathogenic bacteria Nesseria gonorrhoeae and vancomycin-resistant enterococci (VRE) have recently been validated as antibacterial drug targets. Here we explored the inhibition of the α-CA from N. gonorrhoeae (α-NgCA), of α- and γ-class enzymes from Enterococcus faecium (α-EfCA and γ-EfCA) with a panel of aliphatic, heterocyclic and aryl-alkyl primary/secondary monothiocarbamates (MTCs). α-NgCA was inhibited in vitro with KIs ranging from 0.367 to 0.919 µM. The compounds inhibited the α-EfCA and γ-EfCA with KI ranges of 0.195-0.959 µM and of 0.149-1.90 µM, respectively. Some MTCs were also investigated for their inhibitory effects on the growth of clinically-relevant N. gonorrhoeae and VRE strains. No inhibitory effects on the growth of VRE were noted for all MTCs, whereas one compound (13) inhibited the growth N. gonorrhoeae strains at concentrations ranging from 16 to 64 µg/mL. This suggests that compound 13 may be a potential antibacterial agent against N. gonorrhoeae.

Antimicrobial effects of Medicines for Malaria Venture Pathogen Box compounds on strains of Neisseria gonorrhoeae

Therapeutic options for Neisseria gonorrhoeae are limited due to emerging global resistance. New agents and treatment options to treat patients with susceptible and multi-extensively drug-resistant N. gonorrhoeae is a high priority. This study used an in vitro approach to explore the antimicrobial potential, as well as synergistic effects of Medicine for Malaria Venture (MMV) Pathogen Box compounds against ATCC and clinical N. gonorrhoeae strains. Microbroth dilution assay was used to determine pathogen-specific minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the Pathogen Box compounds against susceptible and resistant N. gonorrhoeae strains, with modification, by adding PrestoBlue HS Cell Viability Reagent. A checkerboard assay was used to determine synergy between the active compounds and in conjunction with ceftriaxone. Time-kill kinetics was performed to determine if the compounds were either bactericidal or bacteriostatic. The Pathogen Box compounds: MMV676501, MMV002817, MMV688327, MMV688508, MMV024937, MMV687798 (levofloxacin), MMV021013, and MMV688978 (auranofin) showed potent activity against resistant strains of N. gonorrhoeae at an MIC and MBC of ≤10 µM. Besides the eight compounds, MMV676388 and MMV272144 were active against susceptible N. gonorrhoeae strains, also at MIC and MBC of ≤10 µM. All the compounds were bactericidal and were either synergistic or additive with fractional inhibitory concentration index ranging between 0.40 and 1.8. The study identified novel Pathogen Box compounds with potent activity against N. gonorrhoeae strains and has the potential to be further investigated as primary or adjunctive therapy to treat gonococcal infections.

Substituted salicylic acid analogs offer improved potency against multidrug-resistant Neisseria gonorrhoeae and good selectivity against commensal vaginal bacteria

Drug-resistant Neisseria gonorrhoeae represents a major threat to public health; without new effective antibiotics, untreatable gonococcal infections loom as a real possibility. In a previous drug-repurposing study, we reported that salicylic acid had good potency against azithromycin-resistant N. gonorrhoeae. We now report that the anti-gonococcal activity in this scaffold is easily lost by inopportune substitution, but that select substituted naphthyl analogs (3b, 3o and 3p) have superior activity to salicylic acid itself. Furthermore, these compounds retained potency against multiple ceftriaxone- and azithromycin-resistant strains, exhibited rapid bactericidal activity against N. gonorrhoeae, and showed high tolerability to mammalian cells (CC50 > 128 µg/mL). Promisingly, these compounds also show very weak growth inhibition of commensal vaginal bacteria.

Carbonic Anhydrase Inhibition as a Target for Antibiotic Synergy in Enterococci

Enterococcus faecalis is a hospital-associated opportunistic pathogen that can cause infections with high mortality, such as infective endocarditis. With an increasing occurrence of multidrug-resistant enterococci, there is a need for alternative strategies to treat enterococcal infections. We isolated a gentamicin-hypersusceptible E. faecalis strain from a patient with infective endocarditis that carried a mutation in the alpha-carbonic anhydrase (α-CA) and investigated how disruption of α-CA sensitized E. faecalis to killing with gentamicin. The gentamicin-hypersusceptible α-CA mutant strain showed increased intracellular gentamicin uptake in comparison to an isogenic strain encoding full-length, wild-type α-CA. We hypothesized that increased gentamicin uptake could be due to increased proton motive force (PMF), increased membrane permeability, or both. We observed increased intracellular ATP production in the α-CA mutant strain, suggesting increased PMF-driven gentamicin uptake contributed to the strain's gentamicin susceptibility. We also analyzed the membrane permeability and fatty acid composition of isogenic wild-type and α-CA mutant strains and found that the mutant displayed a membrane composition that was consistent with increased membrane permeability. Finally, we observed that exposure to the FDA-approved α-CA inhibitor acetazolamide lowered the gentamicin MIC of eight genetically diverse E. faecalis strains with intact α-CA but did not change the MIC of the α-CA mutant strain. These results suggest that α-CA mutation or inhibition increases PMF and alters membrane permeability, leading to increased uptake of gentamicin into E. faecalis. This connection could be exploited clinically to provide new combination therapies for patients with enterococcal infections. IMPORTANCE Enterococcal infections can be difficult to treat, and new therapeutic approaches are needed. In studying an E. faecalis clinical strain from an infected patient, we found that the bacteria were rendered hypersusceptible to aminoglycoside antibiotics through a mutation that disrupted the α-CA. Our follow-on work suggested two different ways that α-CA disruption causes increased gentamicin accumulation in E. faecalis: increased proton motive force-powered uptake and increased membrane permeability. We also found that a mammalian CA inhibitor could sensitize a variety of E. faecalis strains to killing with gentamicin. Given that mammalian CA inhibitors are frequently used to treat conditions such as glaucoma, hypertension, and epilepsy, our findings suggest that these "off-the-shelf" inhibitors could also be useful partner antibiotics for the treatment of E. faecalis infections.

Exploring novel aryl/heteroaryl-isosteres of phenylthiazole against multidrug-resistant bacteria

Antimicrobial resistance has become a concern as a worldwide threat. A novel scaffold of phenylthiazoles was recently evaluated against multidrug-resistant Staphylococci to control the emergence and spread of antimicrobial resistance, showing good results. Several structural modifications are needed based on the structure-activity relationships (SARs) of this new antibiotic class. Previous studies revealed the existence of two key structural features essential for the antibacterial activity, the guanidine head and lipophilic tail. In this study, a new series of twenty-three phenylthiazole derivatives were synthesized utilizing the Suzuki coupling reaction to explore the lipophilic part. The in vitro antibacterial activity was evaluated against a range of clinical isolates. The three most promising compounds, 7d, 15d and 17d, with potent MIC values against MRSA USA300 were selected for further antimicrobial evaluation. The tested compounds exhibited potent results against the tested MSSA, MRSA, and VRSA strains (concentration: 0.5 to 4 μg mL^-1). Compound 15d inhibited MRSA USA400 at a concentration of 0.5 μg mL^-1 (one-fold more potent than vancomycin) and showed low MIC values against ten clinical isolates, including linezolid-resistant strain MRSA NRS119 and three vancomycin-resistant isolates VRSA 9/10/12. Moreover, compound 15d retained its potent antibacterial activity using the in vivo model by the burden reduction of MRSA USA300 in skin-infected mice. The tested compounds also showed good toxicity profiles and were found to be highly tolerable to Caco-2 cells at concentrations of up to 16 μg mL^-1, with 100% of the cells remaining viable.

Resistance, Tolerance, Virulence and Bacterial Pathogen Fitness-Current State and Envisioned Solutions for the Near Future

The current antibiotic crisis and the global phenomena of bacterial resistance, inherited and non-inherited, and tolerance-associated with biofilm formation-are prompting dire predictions of a post-antibiotic era in the near future. These predictions refer to increases in morbidity and mortality rates as a consequence of infections with multidrug-resistant or pandrug-resistant microbial strains. In this context, we aimed to highlight the current status of the antibiotic resistance phenomenon and the significance of bacterial virulence properties/fitness for human health and to review the main strategies alternative or complementary to antibiotic therapy, some of them being already clinically applied or in clinical trials, others only foreseen and in the research phase.

Evaluation of 1,3,4-Thiadiazole Carbonic Anhydrase Inhibitors for Gut Decolonization of Vancomycin-Resistant Enterococci

Vancomycin-resistant enterococci (VRE), Enterococcus faecium and Enterococcus faecalis, are high-priority drug-resistant pathogens in need of new therapeutic approaches. VRE originate in the gastrointestinal tract of carriers and can lead to more problematic downstream infections in the healthcare setting. Having a carrier of VRE admitted into a healthcare setting increases the risk to other patients for acquiring an infection. One strategy to eliminate the downstream infections is decolonization of VRE from carriers. Here, we report the activity of a set of carbonic anhydrase inhibitors in the in vivo VRE gastrointestinal decolonization mouse model. The molecules encompass a range of antimicrobial potency and intestinal permeability, and these factors were shown to influence the in vivo efficacy for VRE gut decolonization. Overall, carbonic anhydrase inhibitors exhibited superior VRE decolonization efficacy compared to the current drug of choice, linezolid.

Carbonic Anhydrase Inhibitors as Novel Antibacterials in the Era of Antibiotic Resistance: Where Are We Now?

Resistance to antibiotic treatment developed by bacteria in humans and animals occurs when the microorganisms resist treatment with clinically approved antibiotics. Actions must be implemented to stop the further development of antibiotic resistance and the subsequent emergence of superbugs. Medication repurposing/repositioning is one strategy that can help find new antibiotics, as it speeds up drug development phases. Among them, the Zn²⁺ ion binders, such as sulfonamides and their bioisosteres, are considered the most promising compounds to obtain novel antibacterials, thus avoiding antibiotic resistance. Sulfonamides and their bioisosteres have drug-like properties well-known for decades and are suitable lead compounds for developing new pharmacological agent families for inhibiting carbonic anhydrases (CAs). CAs are a superfamily of metalloenzymes catalyzing the reversible reaction of CO₂ hydration to HCO₃^- and H⁺, being present in most bacteria in multiple genetic families (α-, β-, γ- and ι-classes). These enzymes, acting as CO₂ transducers, are promising drug targets because their activity influences microbe proliferation, biosynthetic pathways, and pathogen persistence in the host. In their natural or slightly modified scaffolds, sulfonamides/sulfamates/sulamides inhibit CAs in vitro and in vivo, in mouse models infected with antibiotic-resistant strains, confirming thus their role in contrasting bacterial antibiotic resistance.

Mucoadhesive brinzolamide-loaded nanofibers for alternative glaucoma treatment

Despite the advances in the field of pharmaceutical materials and technology, topical administration remains a method of choice for the treatment of eye diseases such as glaucoma, with eye drops being a leading dosage form. Their main disadvantage is a very short drug residence time and thus poor drug bioavailability, leading to the necessity of continuous repeated dosing. Mucoadhesive electrospun nanofibers are promising candidates for overcoming these challenges, while still benefiting from topical ocular administration. As an alternative for eye drops, a nanofibrous drug delivery system (DDS) for the delivery of brinzolamide (BRZ), based on β-cyclodextrin (β-CD), hydroxypropyl cellulose (HPC) and polycaprolactone (PCL), was designed. The results showed β-CD/BRZ guest-host interactions, successful drug incorporation into the nanofibers, and the possibility of more accurate dosing in comparison with the control eye drops. Drug permeation through sheep corneas was almost linear in time, achieving therapeutic concentrations in the receptor medium, and mucoadhesion to sheep eye mucosa was relatively high in case of formulations with high HPC content. All formulations were biocompatible, their mechanical properties were sufficient to handle them without caution and UV irradiation was suitable to reduce bioburden of the fibers matrix, yet no antibacterial properties of BRZ were observed.

Mechanistic Studies and In Vivo Efficacy of an Oxadiazole-Containing Antibiotic

Methicillin-resistant Staphylococcus aureus (MRSA) infections are still difficult to treat, despite the availability of many FDA-approved antibiotics. Thus, new compound scaffolds are still needed to treat MRSA. The oxadiazole-containing compound, HSGN-94, has been shown to reduce lipoteichoic acid (LTA) in S. aureus, but the mechanism that accounts for LTA biosynthesis inhibition remains uncharacterized. Herein, we report the elucidation of the mechanism by which HSGN-94 inhibits LTA biosynthesis via utilization of global proteomics, activity-based protein profiling, and lipid analysis via multiple reaction monitoring (MRM). Our data suggest that HSGN-94 inhibits LTA biosynthesis via direct binding to PgcA and downregulation of PgsA. We further show that HSGN-94 reduces the MRSA load in skin infection (mouse) and decreases pro-inflammatory cytokines in MRSA-infected wounds. Collectively, HSGN-94 merits further consideration as a potential drug for staphylococcal infections.

Biological investigation of N-methyl thiosemicarbazones as antimicrobial agents and bacterial carbonic anhydrases inhibitors

The enormous burden of the COVID-19 pandemic in economic and healthcare terms has cast a shadow on the serious threat of antimicrobial resistance, increasing the inappropriate use of antibiotics and shifting the focus of drug discovery programmes from antibacterial and antifungal fields. Thus, there is a pressing need for new antimicrobials involving innovative modes of action (MoAs) to avoid cross-resistance rise. Thiosemicarbazones (TSCs) stand out due to their easy preparation and polypharmacological application, also in infectious diseases. Recently, we reported a small library of TSCs (1–9) that emerged for their non-cytotoxic behaviour. Inspired by their multifaceted activity, we investigated the antibacterial, antifungal, and antidermatophytal profiles of derivatives 1–9, highlighting a new promising research line. Furthermore, the ability of these compounds to inhibit selected microbial and human carbonic anhydrases (CAs) was assessed, revealing their possible involvement in the MoA and a good selectivity index for some derivatives.

In vivo efficacy of acetazolamide in a mouse model of Neisseria gonorrhoeae infection

Gonococcal infections represent an urgent public health threat worldwide due to the increasing incidence of infections that has been accompanied by an increase in bacterial resistance to most antibiotics. This has resulted in a dwindling number of effective treatment options. Undoubtedly, there is a critical need to develop new, effective anti-gonococcal agents. In an effort to discover new anti-gonococcal therapeutics, we previously identified acetazolamide, a carbonic anhydrase inhibitor, as a novel inhibitor of Neisseria gonorrhoeae. Acetazolamide exhibited potent anti-gonococcal activity in vitro as it inhibited growth of strains of N. gonorrhoeae at concentrations that ranged from 0.5 to 4 μg/mL. The aim of this study was to investigate the in vivo efficacy of acetazolamide in a mouse model of N. gonorrhoeae genital tract infection. Compared to vehicle-treated mice, acetazolamide significantly reduced the gonococcal burden by 90% in the vagina of infected mice after three days of treatment. These results indicate that acetazolamide warrants further investigation as a promising treatment option to supplement the limited pipeline of anti-gonococcal therapeutics.

Novel 1,3,5-Triazinyl Aminobenzenesulfonamides Incorporating Aminoalcohol, Aminochalcone and Aminostilbene Structural Motifs as Potent Anti-VRE Agents, and Carbonic Anhydrases I, II, VII, IX, and XII Inhibitors

A series of 1,3,5-triazinyl aminobenzenesulfonamides substituted by aminoalcohol, aminostilbene, and aminochalcone structural motifs was synthesized as potential human carbonic anhydrase (hCA) inhibitors. The compounds were evaluated on their inhibition of tumor-associated hCA IX and hCA XII, hCA VII isoenzyme present in the brain, and physiologically important hCA I and hCA II. While the test compounds had only a negligible effect on physiologically important isoenzymes, many of the studied compounds significantly affected the hCA IX isoenzyme. Several compounds showed activity against hCA XII; (E)-4-{2-[(4-[(2,3-dihydroxypropyl)amino]-6-[(4-styrylphenyl)amino]-1,3,5-triazin-2-yl)amino]ethyl}benzenesulfonamide (31) and (E)-4-{2-[(4-[(4-hydroxyphenyl)amino]-6-[(4-styrylphenyl)amino]-1,3,5-triazin-2-yl)amino]ethyl}benzenesulfonamide (32) were the most effective inhibitors with K_Is = 4.4 and 5.9 nM, respectively. In addition, the compounds were tested against vancomycin-resistant Enterococcus faecalis (VRE) isolates. (E)-4-[2-({4-[(4-cinnamoylphenyl)amino]-6-[(4-hydroxyphenyl)amino]-1,3,5-triazin-2-yl}amino)ethyl]benzenesulfonamide (21) (MIC = 26.33 µM) and derivative 32 (MIC range 13.80-55.20 µM) demonstrated the highest activity against all tested strains. The most active compounds were evaluated for their cytotoxicity against the Human Colorectal Tumor Cell Line (HCT116 p53 +/+). Only 4,4'-[(6-chloro-1,3,5-triazin-2,4-diyl)bis(iminomethylene)]dibenzenesulfonamide (7) and compound 32 demonstrated an IC₅₀ of ca. 6.5 μM; otherwise, the other selected derivatives did not show toxicity at concentrations up to 50 µM. The molecular modeling and docking of active compounds into various hCA isoenzymes, including bacterial carbonic anhydrase, specifically α-CA present in VRE, was performed to try to outline a possible mechanism of selective anti-VRE activity.

Repurposing FDA-approved sulphonamide carbonic anhydrase inhibitors for treatment of Neisseria gonorrhoeae

Neisseria gonorrhoeae is a high-priority pathogen of concern due to the growing prevalence of resistance development against approved antibiotics. Herein, we report the anti-gonococcal activity of ethoxzolamide, the FDA-approved human carbonic anhydrase inhibitor. Ethoxzolamide displayed an MIC_50, against a panel of N. gonorrhoeae isolates, of 0.125 µg/mL, 16-fold more potent than acetazolamide, although both molecules exhibited almost similar potency against the gonococcal carbonic anhydrase enzyme (NgCA) in vitro. Acetazolamide displayed an inhibition constant (K_i) versus NgCA of 74 nM, while Ethoxzolamide^’s K_i was estimated to 94 nM. Therefore, the increased anti-gonococcal potency of ethoxzolamide was attributed to its increased permeability in N. gonorrhoeae as compared to that of acetazolamide. Both drugs demonstrated bacteriostatic activity against N. gonorrhoeae, exhibited post-antibiotic effects up to 10 hours, and resistance was not observed against both. Taken together, these results indicate that acetazolamide and ethoxzolamide warrant further investigation for translation into effective anti-N. gonorrhoeae agents.

Selective Inhibition of Helicobacter pylori Carbonic Anhydrases by Carvacrol and Thymol Could Impair Biofilm Production and the Release of Outer Membrane Vesicles

Helicobacter pylori, a Gram-negative neutrophilic pathogen, is the cause of chronic gastritis, peptic ulcers, and gastric cancer in humans. Current therapeutic regimens suffer from an emerging bacterial resistance rate and poor patience compliance. To improve the discovery of compounds targeting bacterial alternative enzymes or essential pathways such as carbonic anhydrases (CAs), we assessed the anti-H. pylori activity of thymol and carvacrol in terms of CA inhibition, isoform selectivity, growth impairment, biofilm production, and release of associated outer membrane vesicles-eDNA. The microbiological results were correlated by the evaluation in vitro of H. pylori CA inhibition, in silico analysis of the structural requirements to display such isoform selectivity, and the assessment of their limited toxicity against three probiotic species with respect to amoxicillin. Carvacrol and thymol could thus be considered as new lead compounds as alternative H. pylori CA inhibitors or to be used in association with current drugs for the management of H. pylori infection and limiting the spread of antibiotic resistance.

An anion and small molecule inhibition study of the β-carbonic anhydrase from Staphylococcus aureus

Pathogenic bacteria resistant to most antibiotics, including the methicillin-resistant Staphylococcus aureus (MRSA) represent a serious medical problem. The search for new antiinfectives, possessing a diverse mechanism of action compared to the clinically used antibiotics, has become an attractive research field. S. aureus DNA encodes a β-class carbonic anhydrase, SauBCA. It is a druggable target that can be inhibited by certain aromatic and heterocyclic sulphonamides. Here we investigated inorganic anions and some other small molecules for their inhibition of SauBCA. The halides, nitrite, nitrate, bicarbonate, carbonate, bisulphite, sulphate, stannate, and N,N-diethyldithiocarbamate were submillimolar SauBCA inhibitors with K_Is in the range of 0.26 − 0.91 mM. The most effective inhibitors were sulfamide, sulfamate, phenylboronic acid, and phenylarsonic acid with K_Is of 7 − 43 µM. Several interesting inhibitors detected here may be considered lead compounds for the development of even more effective derivatives, which should be investigated for their bacteriostatic effects.

Anion inhibition studies of the α-carbonic anhydrases from Neisseria gonorrhoeae

The bacterial pathogen Neisseria gonorrhoeae encodes for an α-class carbonic anhydrase (CA, EC 4.2.1.1), NgCA, which was investigated for its inhibition with a series of inorganic and organic anions. Perchlorate and hexafluorophosphate did not significantly inhibit NgCA CO₂ hydrase activity, whereas the halides, azide, bicarbonate, carbonate, stannate, perosmate, diphosphate, divanadate, perruthenate, and trifluoromethanesulfonate showed inhibition constants in the range of 1.3–9.6 mM. Anions/small molecules such as cyanate, thiocyanate, nitrite, nitrate, bisulphite, sulphate, hydrogensulfide, phenylboronic acid, phenylarsonic acid, selenate, tellurate, tetraborate, perrhenate, peroxydisulfate, selenocyanate, iminodisulfonate, and fluorosulfonate showed K_Is in the range of 0.15–1.0 mM. The most effective inhibitors detected in this study were sulfamide, sulfamate, trithiocarbonate and N,N-diethyldithiocarbamate, which had K_Is in the range of 5.1–88 µM. These last compounds incorporating the CS₂^- zinc-binding group may be used as leads for developing even more effective NgCA inhibitors in addition to the aromatic/heterocyclic sulphonamides, as this enzyme was recently validated as an antibacterial drug target for obtaining novel antigonococcal agents