Inhibition of hyphal growth of Candida albicans by activated lansoprazole, a novel benzimidazole proton pump inhibitor

In vitro interactions of proton pump inhibitors and azoles against pathogenic fungi

Introduction

Azole resistance has been increasingly reported and become an issue for clinical managements of invasive mycoses. New strategy with combination therapy arises as a valuable and promising alternative option. The aim of the present study is to investigate the in vitro combinational effect of proton pump inhibitors (PPIs) and azoles against pathogenic fungi.

Methods

In vitro interactions of PPIs including omeprazole (OME), lansoprazole (LAN), pantoprazole (PAN), and rabeprazole (RAB), and commonly used azoles including itraconazole (ITC), posaconazole (POS), voriconazole (VRC) and fluconazole (FLC), were investigated via broth microdilution chequerboard procedure adapted from the CLSI M27-A3 and M38-A2. A total of 67 clinically isolated strains, namely 27 strains of Aspergillus spp., 16 strains of Candida spp., and 24 strains of dematiaceous fungi, were studied. C. parapsilosis (ATCC 22019) and A. flavus (ATCC 204304) was included to ensure quality control.

Results

PPIs individually did not exert any significant antifungal activity. The combination of OME with ITC, POS, or VRC showed synergism against 77.6%, 86.6%, and 4% strains of tested pathogenic fungi, respectively, while synergism of OME/FLC was observed in 50% strains of Candida spp. Synergism between PAN and ITC, POS, or VRC was observed against 47.8%, 77.6% and 1.5% strains of tested fungi, respectively, while synergism of PNA/FLC was observed in 50% strains of Candida spp. Synergism of LAN with ITC, POS, or VRC was observed against 86.6%, 86.6%, and 3% of tested strains, respectively, while synergism of LAN/FLC was observed in 31.3% strains of Candida spp. Synergy of the combination of RAB with ITC, POS, or VRC was observed against 25.4%, 64.2%, and 4.5% of tested strains, respectively, while synergism of RAB/FLC was observed in 12.5% of Candida spp.. Among PPIs, synergism was least observed between RAB and triazoles, while among triazoles, synergism was least observed between VRC and PPIs. Among species, synergy was much more frequently observed in Aspergillus spp. and dematiaceous fungi as compared to Candida spp. Antagonism between PPIs with ITC or VRC was occasionally observed in Aspergillus spp. and dematiaceous fungi. It is notable that PPIs combined with azoles showed synergy against azole resistant A. fumigatus, and resulted in category change of susceptibility of ITC and POS against Candida spp.

Discussion

The results suggested that PPIs combined with azoles has the potential to enhance the susceptibilities of azoles against multiple pathogenic fungi and could be a promising strategy to overcome azole resistance issues. However, further investigations are warranted to study the combinational efficacy in more isolates and more species, to investigate the underlying mechanism of interaction and to evaluate the potential for concomitant use of these agents in human.

Anti-infective properties of proton pump inhibitors: perspectives

Infectious diseases are among the main causes of morbidity and mortality today. In facing this crisis, the development of new drug options and combat strategies is necessary. In this sense, drug repositioning or drug redirection has emerged for the faster identification of effective drugs. In this “Commentary,” the anti-infective properties of the class of proton pump inhibitors (PPIs) are emphasized. Studies report activities against bacterial, fungal, parasitic, and viral agents. In addition, we have provided in a table a summary of the specific characteristics of PPIs and some of their anti-infective activities.

Systematic review: the effects of proton pump inhibitors on the microbiome of the digestive tract-evidence from next-generation sequencing studies

BACKGROUND

Proton pump inhibitors (PPI) are widely used to treat acid-related disorders of the upper gastrointestinal tract. However, large observational studies have raised concerns about PPI-associated adverse events. In recent years, data from next-generation sequencing studies suggested that PPIs affect the composition of the intestinal microbiota, while a balanced gut microbiome is essential for maintaining health.

AIM

To review the available evidence from next-generation sequencing studies on the effect of PPIs on the intestinal microbiome and to discuss possible implications of PPI-induced dysbiosis in health and disease.

METHODS

A systematic review was conducted following the recommendations of the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement. A PubMed query yielded 197 results. 19 publications met the prespecified eligibility criteria.

RESULTS

Twelve observational study cohorts with 708 PPI users and 11 interventional cohorts with 180 PPI users were included in the review. In most studies, PPI treatment did not affect microbiological richness and diversity, but was associated with distinct taxonomic alterations: In the upper gastrointestinal tract, PPI users showed overgrowth of orally derived bacteria, mostly Streptococcaceae (findings based on six independent cohorts with 126 PPI users). In faecal samples, PPIs increased multiple taxa from the orders Bacillales (eg, Staphylococcaceae), Lactobacillales (eg, Enterococcaceae, Lactobacillaceae, Streptococcaceae) and Actinomycetales (eg, Actinomycetaceae, Micrococcaceae), the families Pasteurellaceae and Enterobacteriaceae and the genus Veillonella. Taxa decreased by PPIs include Bifidobacteriaceae, Ruminococcaceae, Lachnospiraceae and Mollicutes (findings in faecal samples based on 19 independent cohorts with 790 PPI users).

CONCLUSION

PPI use is associated with moderate alterations to upper and distal gut microbiota. The available data suggest that PPI-induced hypochlorhydria facilitates colonization of more distal parts of the digestive tract by upper gastrointestinal microbiota.

Proton pump inhibitors act synergistically with fluconazole against resistant Candida albicans

The incidence of resistant Candida isolates, especially Candida albicans, has increased continuously. To overcome the resistance, research on antifungal agent sensitizers has attracted considerable attention. Omeprazole and lansoprazole were found to inhibit the growth of sensitive C. albicans and hyphae formation in a high dose, respectively. This study aimed to determine the interactions of common clinically proton pump inhibitors (PPIs) and fluconazole both in vitro and in vivo and to further explore the possible mechanisms. In vitro, the tested PPIs all acted synergistically with fluconazole against both resistant C. albicans planktonic cells and biofilms preformed for ≤12 h with the minimum inhibitory concentration of fluconazole decreased from >512 μg/mL to 1–4 μg/mL. In vivo, PPIs plus fluconazole prolonged the survival rate of infected Galleria mellonella larvae by two-fold compared with that for the fluconazole monotherapy group and significantly reduced the tissue damage of infected larvae. Mechanism studies showed that PPIs significantly suppressed efflux pump activity, which is the common resistance mechanism of C. albicans, and significantly inhibited the virulence factors: phospholipase activity and morphology switching. These findings will provide new insights into antifungal agent discovery and potential approaches for the treatment of candidiasis caused by resistant C. albicans.

Promising Antifungal Targets Against Candida albicans Based on Ion Homeostasis

In recent decades, invasive fungal infections have been increasing significantly, contributing to high incidences and mortality in immunosuppressed patients. Candida albicans (C. albicans) is the most prevalent opportunistic fungal pathogen in humans that can cause severe and often fatal bloodstream infections. Current antifungal agents have several limitations, including that only a small number of classes of antifungals are available, certain of which have severe toxicity and high cost. Moreover, the emergence of drug resistance is a new limitation to successful patient outcomes. Therefore, the development of antifungals with novel targets is an essential strategy for the efficient management of C. albicans infections. It is widely recognized that ion homeostasis is crucial for all living cells. Many studies have identified that ion-signaling and transduction networks are central to fungal survival by regulating gene expression, morphological transition, host invasion, stress response, and drug resistance. Dysregulation of ion homeostasis rapidly mediates cell death, forming the mechanistic basis of a growing number of compounds that elicit antifungal activity. Most of the potent antifungals have been widely used in the clinic, and certain of them have low toxicity, meaning that they may be expected to be used as antifungal drugs in the future. Hence, we briefly summarize the homeostasis regulation of several important ions, potential antifungal targets based on these ion-signaling networks, and antifungal compounds based on the disruption of ion homeostasis. This summary will help in designing effective drugs and identifying new targets for combating fungal diseases.

Risk factors of Candida colonization in the oropharynx of patients admitted to an intensive care unit

OBJECTIVES

Candida colonization is an important precursor for candidiasis. However, there is little information about its risk factors in critically ill patients. We aimed to identify risk factors for oropharyngeal Candida colonization in critically ill patients.

PATIENTS, MATERIALS AND METHODS

This is a prospective observational study of 110 patients admitted to a medical intensive care unit (MICU). Oropharyngeal swabs were obtained on day one and day four. Characteristics of patients colonized with Candida species at admission or not colonized were compared. In addition, patients becoming colonized during their ICU stay were compared to patients who did not.

RESULTS

Independent risk factors for a positive Candida sample at the time of admission were: a history of proton pump inhibitor (PPI) use before admission (OR: 5.24, 95% CI: 1.36-20.19), the presence of diabetes mellitus (OR: 2.84, 95%CI: 1.02-7.92) and a lower BMI (OR: 0.9, 95% CI: 0.84-0.97). Chronic kidney disease was associated with a decreased frequency of Candida colonization (OR: 0.26, 95% CI: 0.01-0.46). No independent risk factors could be identified for patients who gained Candida during their ICU hospitalization. Patients with Candida colonization frequently had abnormal oral bacterial flora.

CONCLUSIONS

Diabetes mellitus, PPI use and a lower BMI are risk factors for Candida colonization in critically ill patients being admitted to the MICU.

Functional complementation of the yeast P-type H-ATPase, PMA1, by the Pneumocystis carinii P-type H-ATPase, PCA1

The opportunistic fungus Pneumocystis is the etiologic agent of an interstitial plasma cell pneumonia that primarily afflicts immunocompromised individuals. Like other fungi Pneumocystis maintains a H(+) plasma membrane gradient to drive nutrient uptake and regulates intracellular pH by ATP-dependent proton efflux. Previously, we identified a Pneumocystis gene, PCA1, whose predicted protein product was homologous to fungal proton pumps. In this study, we show by functional complementation in a Saccharomyces strain whose endogenous PMA1 proton pump activity is repressed that the Pneumocystis PCA1 encodes a H(+)-ATPase. The properties of PCA1 characterized in this system closely resemble those of yeast PMA1. Yeast expressing PCA1 grow at low pH and are able to acidify the external media. Maximal enzyme activity (V(max)) and efficiency of substrate utilization (K(m)) in plasma membranes were nearly identical for PCA1 and PMA1. PCA1 contains an inhibitory COOH-terminal domain; removal of the final 40 amino acids significantly increased V(max) and growth at pH 6.5. PCA1 activity was inhibited by proton pump inhibitors omeprazole and lansoprazole, but was unaffected by H(+)/K(+)-ATPase inhibitor SCH28080. Thus, H(+) homeostasis in Pneumocystis is likely regulated as in other fungi. This work also establishes a system for screening PCA1 inhibitors to identify new anti-Pneumocystis agents.

Potent synergistic in vitro interaction between nonantimicrobial membrane-active compounds and itraconazole against clinical isolates of Aspergillus fumigatus resistant to itraconazole

To develop new approaches for the treatment of invasive infections caused by Aspergillus fumigatus, the in vitro interactions between itraconazole (ITZ) and seven different nonantimicrobial membrane-active compounds--amiodarone (AMD), amiloride, lidocaine, lansoprazole (LAN), nifedipine (NIF), verapamil, and fluphenazine--against seven ITZ-susceptible and seven ITZ-resistant (ITZ-R) strains were evaluated by the checkerboard microdilution method based on National Committee for Clinical Laboratory Standards M-38A guidelines. The nature and the intensity of the interactions were assessed by a nonparametric approach (fractional inhibitory concentration [FIC] index model), a fully parametric response surface approach (Greco model) of the Loewe additivity no-interaction theory, and the nonparametric (Prichard model) and semiparametric response surface approaches of the Bliss independence (BI) no-interaction theory. Statistically significant synergy was found for the combination of ITZ and AMD and the combination of LAN and NIF, although with different intensities against ITZ-R strains. The FIC index values ranged from 1 to 0.02 for ITZ-AMD, 0.53 to 0.04 for ITZ-LAN, and 0.28 to 0.06 for ITZ-NIF. By use of the BI-based model, the strongest synergy was found for the combination of ITZ with AMD, followed by the combination of ITZ and NIF. The parametric models could not be fit adequately because most of the drugs alone did not show any effect and, thus, no sigmoid dose-response. In general, the combination of ITZ with calcium pump blockers displayed in vitro synergistic activity, primarily against ITZ-R strains, and warrants further investigation.

Antifungal activity of nonantifungal drugs

The antifungal activity of synthetic, nonchemotherapeutic compounds, antineoplastic agents and antibacterial drugs, such as sulphonamides, has been known since the early 20th century (1932). In this context, the term "nonantifungal" is taken to include a variety of compounds that are employed in the management of pathological conditions of nonfungal infectious etiology but have been shown to exhibit broad-spectrum antifungal activity. In this review, the antifungal properties of compounds such as chlorpromazine, proton pump inhibitors, antiarrhythmic agents, cholesterol-lowering agents, antineoplastic and immunosuppressive agents, antiparasitic drugs and antibiotics are described. Since fungi are eukaryotic cells, they share many pathways with human cells, thus increasing the probability of antifungal activity of "nonfungal drugs". The potential of these drugs for treatment of fungal infections has been investigated sporadically using the drugs alone or in combination with "classic" antifungal agents. A review of the literature, supplemented with a number of more recent investigations, suggests that some of these compounds enhance the activity of conventional antifungal agents, eliminate natural resistance to specific antifungal drugs (reversal of resistance) or exhibit strong activity against certain fungal strains in vitro and in animal models. The role of these agents in the epidemiology and in the clinical manifestations of fungal infections and the potential of certain drugs for treatment of invasive fungal infections require further investigation.

Functional characterization of a H+/nucleoside co-transporter (CaCNT) from Candida albicans, a fungal member of the concentrative nucleoside transporter (CNT) family of membrane proteins

Human and other mammalian concentrative (Na(+)-linked) nucleoside transport proteins belong to a membrane protein family (CNT, TC 2.A.41) that also includes Escherichia coli H(+)-dependent nucleoside transport protein NupC. Here, we report the cDNA cloning and functional characterization of a CNT family member from the pathogenic yeast Candida albicans. This 608 amino acid residue H(+)/nucleoside symporter, designated CaCNT, contains 13 predicted transmembrane domains (TMs), but lacks the exofacial, glycosylated carboxyl-terminus of its mammalian counterparts. When produced in Xenopus oocytes, CaCNT exhibited transport activity for adenosine, uridine, inosine and guanosine but not cytidine, thymidine or the nucleobase hypoxanthine. Apparent K(m) values were in the range 16-64 micro M, with V(max) : K(m) ratios of 0.58-1.31. CaCNT also accepted purine and uridine analogue nucleoside drugs as permeants, including cordycepin (3'-deoxyadenosine), a nucleoside analogue with anti-fungal activity. Electrophysiological measurements under voltage clamp conditions gave a H(+) to [(14)C]uridine coupling ratio of 1 : 1. CaCNT, obtained from logarithmically growing cells, is the first described cation-coupled nucleoside transporter in yeast, and the first member of the CNT family of proteins to be characterized from a unicellular eukaryotic organism.

Identification of surface-membrane P-type ATPases resembling fungal K(+)- and Na(+)-ATPases, in Trypanosoma brucei, Trypanosoma cruzi and Leishmania donovani

Genomic DNA fragments encoding nine, novel, P-type ATPases in trypanosomatid organisms were amplified in PCR, using degenerate oligonucleotide primers that recognize the ATP-binding and -phosphorylation sites present in all P-type ATPases. Subsequent phylogenetic analysis, based on the presence of conserved motifs in predicted peptide sequences for six Trypanosoma brucei, T. cruzi or Leishmania donovani PCR fragments, identified calcium-, proton- and phospholipid-translocating ATPases. DNA fragments that predict proteins homologous to the fungal, type-IID, P-type, ATPase pumps that transport Na(+) or K(+) ions were also present in T. brucei (TBCA1; 1022 nucleotides representing 340 amino acids), T. cruzi (TCNA1; 1022 nucleotides representing 340 amino acids) and L. donovani (LDCA1; 1031 nucleotides representing 343 amino acids). Southern blots showed that the Na(+)-ATPases were each present as a single-copy gene. The LDCA1 fragment was used to clone the complete LDCA1 gene from an L. donovani genomic-DNA library. The LDCA1 gene encodes a protein, of 1047 amino acids, with a predicted molecular mass of 115,501 Da. The results of analyses based on northern blots and the rapid amplification of cDNA ends (RACE) indicated that LDCA1 was expressed in promastigotes and amastigotes from axenic cultures and in animal-derived amastigotes. TBCA1 was expressed, as a 5.0-kb transcript, in procyclic culture stages and bloodstream trypomastigotes, with the 5.0-kb message up-regulated six-fold in the trypomastigote stage. Western blots probed with an antibody to the partial TBCA1 peptide identified a 150-kDa protein that was detected, by immunofluorescence, on the surface membrane of procyclic T. brucei.