Anti-Infective Agents - Volume 11, Issue 2, 2013

Ecoinfectomics is the ecological study of infectomes and explores symbiotic solutions to microbial infections. The most fundamental issue in ecological infectomics is how to transform situations of potential conflict (pathogenesis or Pat) into cooperation (symbiosis or Sym) by dissecting the dynamic Sym-Pat duality in microbial infections and developing symbiotic agents (symbiotics) that favor a healthy symbiosis. Symbiotics are defined as products that are beneficial to the symbiotic ecology of the super-organisms consisting of microbes and their human hosts. These include microbial (e.g., probiotic bacteria and phages) and nonmicrobial agents (e.g., prebiotics). Probiotics have been proposed as a promising way to prevent microbial infection in neonates. It has been shown that probiotics could be useful to correct ecological disorders in human intestinal microbiota associated with neonatal sepsis and meningitis, and might play a protective role in excluding pathogens from the intestine and preventing infections. Compared with commonly used antibiotics, a great advantage of phages is their narrow host range. A rational basis has been provided for the discovery and development of phage-based symbiotics that only kill pathogens but do not disturb benign microbes in normal microbiota. The systems biology study of ecoimmunity or ecoimmunome (ecoimmunomics), which is most closely related to ecoinfectomics, may provide alternative ecological strategies toward clinical challenges in infectious diseases. We propose that the balance between exosymbiosis (e.g, microbiota) and endosymbiosis (e.g., mitochondria) is essential for ecoimmunity and that the exo-endo Sym imbalance plays an important role in the pathogenesis of infectious diseases, including HIV/AIDS. Correction of disorders of the ecoimmunity in patients with AIDS may lead to a rational control of HIV infection. Holistic and integrative studies of ecoinfectomes, ecoimmunomes, and microbiome are important for our understanding of microbial pathogenesis and the development of symbiotic solutions to infectious diseases.

Chemoinfectomics (chemical infectomics) is the study of small exogenous molecules that are highly specified to define molecular targets (e.g., genes, proteins, glycans, and lipids) or infectomic signatures, to enable functional analysis of microbes and their hosts, and to uncover new antimicrobial drug leads. It requires multidisciplinary expertise in chemical omics (chemogenomics, chemoproteomics, chemoglycomics and chemolipidomics), infectious diseases, and computational sciences (bioinformatics, cheminformatics, large scale statistics and machine learning methods). Chemoinfectomics will overcome the major limitation of the conventional paradigm of managing infectious diseases, which has mainly targeted on microorganisms with low selectivity. The development of drug resistance to both pathogenic and nonpathogenic microbes has been one of the most serious disadvantages of the traditional microbe-directed drug targeting strategies. Therefore, a new chemoinfectomics-based drug discovery paradigm has emerged, focusing on identifying and targeting host factors essential for microbial interactions and pathogenesis. Innovative strategies combining chemoinfectomics, computational biology, and conventional targeting of microbial virulence factors have the potential to greatly augment the protective host factors and to specifically and efficiently eliminate the invading pathogen.

The immune system plays an essential role in the pathogenesis, prevention and treatment of infectious diseases. Immunoinfectomics is an emerging field that addresses the interface between the host immune system and pathogens, and studies immunomes and infectomes (immunoinfectomes). Immune responses induced by microbial infections are complex phenomena that supervene on the levels of genomes, and as a result, infection and immunity ultimately depend on immunoinfectomes. The computational and mathematical approaches have shown practical benefits to convert all these complex data into sophisticated computer models of cellular gene and protein networks. The availability of the above methods has resulted in exciting new progress in the discovery and development of drugs and vaccines against infectious diseases with immunoinfectomic approaches. It has been demonstrated that only one single variable domain antibody fragment, referred to as VHH (variable heavy chain antibody) or nanobody, can interact with antigens. Nanobodies display several characteristics superior to the conventional antibodies, including their non-immunogenicity and high thermal and chemical stability. These characteristics make nanobodies strong candidates as targeting agents for infectious diseases. Recently, tremendous progress has been made in immune epitope mapping and vaccine candidate identification through the use of the immunoinfectomic approaches. These omic approaches provide powerful tools for advances in system biology of microbial infections and the discovery of novel antimicrobial agents.

The interaction between Cryptococcus neoformans and the host system is a consummate process, on account of the multiple components involved in its traversal of the blood-brain barrier (BBB). It is possible that this yeast pathogen may use different mechanisms of invasion under different physiological or pathological conditions. Understanding these mechanisms of encroachment can explicate the route of invasion, which may provide us with an indication for identifying the potential drug target sites. Current C. neoformans management still relies on the anti-fungal reagents, such as amphotericin B, fluconazole, or fluorocytosine. However, potential treatments on BBB, e.g., flurofamide and simvastatin, are emerging. This review summarizes the possible routes for C. neoformans traversal of the BBB, current regimens for C. neoformans, and potential new targets for treatments.

Continual genetic variation supports hepatitis C virus (HCV) persistent infection, a leading cause of cirrhosis and hepatocellular carcinoma. The current standard of care has limited efficacy and is associated with severe adverse effects. Efforts to improve patients' outcomes have focused on the design and development of small molecule compounds targeted towards essential viral proteins. Following the clinical success of HIV protease inhibitors, the HCV NS3-4A protease domain emerged as one of the most successful antiviral drug targets. This mini-review describes several HCV protease inhibitors in the various stages of clinical trials, and discusses their antiviral activities, pharmacokinetic properties, side effects and resistance profiles.

Production of Candida albicans biofilms is one resistance mechanism of fluconazole in C. albicans and accordingly biofilm-related infections pose a great challenge to antifungal therapy. In this study, each of the three antibacterial agents of azithromycin, fosfomycin and rifampin, which could destroy bacteria biofilms, was respectively tested in combination with fluconazole to verify whether they had synergistic effects on C. albicans biofilms. The nature of drug interaction was interpreted by calculating fractional inhibitory concentration index (FICI) and percentages of growth difference (ΔE) from the results of checkerboard assay. In order to evaluate the potential of the three antibiotics on fluconazole penetrating the biofilms, a penetrating experiment was explored. In addition, fluorescein diacetate staining method was adopted to observe metabolic activity of the sessile cell. It was revealed that rifampin could work synergistically with fluconazole against the biofilms, while only negligible antifungal effects were observed for the other drug combinations. A potent synergistic interaction in vitro between fluconazole and rifampin against the biofilms by a fluconazole-resistant strain was demonstrated by a FICI value of 0.035 and synergistic high-interaction percentages of 1256% as interpreted by the ΔE model. Results of the penetrating experiment indicated that fluconazole combined with rifampin markedly enhanced inhibitory zone of an indicative organism. Fluorescence micrographs showed that the addition of rifampin rendered the cellular metabolism largely reduced. To sum up, rifampin could sensibilize fluconazole’ antifungal effect on C. albicans biofilms and the synergistic mechanism needs further investigating.

Pine needles are used in folk medicine to treat liver disease, gastrointestinal diseases, nervous system disease, circulatory diseases, and skin problems. The present study was to evaluate the antibacterial activity of methanol (MeOH) extract of pine needles against some cariogenic and periodontal bacteria. The chekerboard and time-kill tests were used for the combined evaluations. The MIC and MBC values for MeOH extract against all tested oral bacteria were in the ranges 0.25-4 mg/mL and 1-16 mg/mL, respectively. The range of MIC50 and MIC90 of MeOH extract was 0.0625-2 mg/mL and 1-16 mg/mL, respectively. Significant synergies were observed by the MeOH extract with ampicillin or gentamicin combinations at FICI ranged all 0.5. Furthermore, 2-6 hours of treatment with 1/2 MIC of MeOH extract with 1/2 MIC of antibiotics resulted in an increase in the rate of killing in units of CFU/ml to a greater degree than was observed with MeOH extract alone. These results demonstrated that MeOH extract of pine needles enhanced the efficacy of ampicillin and gentamicin in vitro, which had potential for combinatory therapy of patients infected with oral pathogens.

Lactoferrin is an iron binding protein belonging to the transferrin superfamily. Its main function is the protection towards infections. In a previous article (Leboffe et al., Anti-Infective Agents in Medicinal Chemistry, 2009), we have reviewed the antifungal and antiparasitic activity of lactoferrin. In the present updated review we focused the attention on the newly discovered antifungal properties of lactoferrin and its derived peptides in clinical, diagnostic and biotechnological applications. In particular, we discuss the new findings on diagnosis of fungal infections utilizing Lf and on emerging pharmacological treatments exploiting combined effects of Lf and classical antifungal drugs. We also reported recent studies on the use of Lf antifungal activity for food and beverage preservation. These new properties have found applications both “in vitro” and “in vivo”, opening new scenarios about the use of this protein as an antinfective agent both in translational medicine and biotechnology.

The aim of this work was to investigate the antibacterial activity of clove (Syzygium aromaticum) essential oil against multidrug resistant clinical strains of Klebsiella pneumoniae ESBL+. Materials: The antibacterial activity of the oil was tested against standard strain Klebsiella pneumoniae ATCC 700603 and 60 clinical strains of Klebsiella pneumoniae isolated from patients with infections of the respiratory tract, abdominal cavity, urinary tract, skin and from the hospital environment. Methods: The agar dilution method was used to assess the inhibition of microbial growth at various concentrations of the clove oil. Susceptibility testing to antibiotics was carried out using disc-diffusion. Results: The results of experiments showed that clove essential oil possessed very strong activity against all of the clinical strains of extendedspectrum β-lactamase (ESBL)-producing ESBL+ from Klebsiella pneumoniae. Conclusions: The results of this study suggest the potential use of clove essential oil against K. pneumoniae ESBL+ that is responsible for infections difficult to treat. Essential oils my be an excellent alternative for synthetic preparations and, used in combination with antibiotics, may prevent antibiotic-resistant strain development.

AcrAB-TolC is involved in the multi-drug resistance (MDR) phenotype of numerous bacterial species. Herein we compared the antibacterial activity of geraniol, a monoterpene found in many plant extracts and derivatives against two isogenic strains of Enterobacter aerogenes, a clinical MDR isolate and its acrAB deletion mutant. These compounds had very different MIC values, which was dependent on the structural features of the compound. Some of the molecules, including geraniol, had a higher MIC for the MDR strain than for the deletion mutant. A similar result was obtained for PAßN, a well-known efflux-pump inhibitor. Conversely, some molecules, including geranylamine, exhibited the same intrinsic activity against both strains, suggesting they are not substrates of AcrAB-TolC. To report efflux activity, we then compared the ability of the compounds to decrease chloramphenicol resistance. Two compounds, geraniol and geranylamine were shown to decrease the MIC for chloramphenicol to the same extent as PAßN. Considering that PAßN is a competitive inhibitor of AcrAB-TolC and that geranylamine is an efficient inhibitor but not a substrate, we suggest that geranylamine inhibits AcrAB-TolC through a non-competitive mechanism. The results are discussed in light of the recent advances in the structural and mechanical features of AcrAB-TolC.

We report here on the synthesis of substituted nitroalkenyl arenes and their evaluation for microbiological activity and for development as anti-infective drugs. Twenty compounds, based on the nitropropenyl benzene structure (1), were synthesized, chemically characterized and investigated for their minimum inhibitory concentration (MIC) to bacteria and fungi and for toxicity to zebrafish eggs and embryos for comparative evaluation of potential mammalian toxicity. The compounds were broadly antimicrobial, with greater activity overall against Gram-positive bacteria and fungi and less against enteric Gram-negative rods. The antimicrobial activity spectrum of the compounds varied greatly. Two compounds, 14 (5-[(E)-2-nitroprop-1-enyl]-1,3-benzodioxole) and 9 ((4-[(E)-2-nitroprop-1-enyl]-1-fluorobenzene), were the most broadly antimicrobial. The chemical groups most closely associated with microbial toxicity were the β-nitropropenyl side chain, fluoro, methylenedioxy and thiazole substitutions on the benzene ring. Thirteen compounds inhibited hatching of zebrafish eggs at concentrations ≤6 µg/mL. Egg toxicity did not correlate with inhibition of microbial growth or with rodent toxicity where data were available. Four compounds were investigated for effect on zebrafish embryonic development. The major effect observed was reduction of heart rate at 24 h with minimal or no morphological abnormalities at the highest doses. It is hypothesised that this series of compounds act as tyrosine mimetics, inhibiting protein tyrosine phosphatases (PTP) and interfering with cell signaling in microorganisms. The data confirms the diversity in function and distribution of bacterial PTPs and the potential for the design of further nitroalkenyl arenes active against specific pathogens.

Background: The non absorbable antibiotic rifamycin SV newly formulated as modified colonic release MMX® tablets was preliminarily investigated. Methods: In a multi-centre, double-blind, double-dummy, randomised, parallelgroup study, efficacy and safety of the 200 mg tablets were investigated vs. rifaximin 200 mg tablets in infectious diarrhoea. Results: 22 rifamycin SV recipients (47.8%) were successes, whilst 24 (52.5%) discontinued. In the reference group 27 (50.9%) were successes, whilst 26 (49.1%) discontinued. The median time to last unformed stool was 67.5 h after rifamycin SV and 65.5 h after rifaximin. Conclusions: The efficacy of the new tablets was not significantly different from that of rifaximin administered 4 times a day for 3 days. The treatments did not differ in rate or frequency of therapeutic success. Isolates of Campylobacter jejuni and lari, Escherichia coli, Anaerobiospirillum, Salmonella enteritidis and Shigella flexneri found at pre-treatment were not retrievable after rifamycin SV.

Acyclovir, a widely used anti-viral drug, is the treatment of choice for initial episodes and management of recurrent episodes of genital herpes. Oral immediate release (IR) formulations of acyclovir have limitations of poor and variable bioavailability (15-30%), and dosing frequency up to five times a day. Such limitations lead to poor patient compliance and development of drug resistance. An oral extended release (ER) formulation of acyclovir can overcome these limitations. In the present study, a simple simulation technique for determination of the dose and in-vitro drug release profile required for an ER formulation of acyclovir to achieve steady state maximum and minimum plasma concentrations ( Cssmax and Cssmin ) similar to or better than those of an IR formulation, has been reported. First order drug release and absorption models were used. The dose and in-vitro drug release rate required for the ER formulation were found to be 725 mg and 0.259 h-1, respectively. Cssmax and Cssmin values of the ER formulation were 90% and 218%, respectively, compared to those of the IR formulation. The fluctuation index of the ER formulation ( FIER ) was 69% of that of the IR formulation ( FIIR ), indicating that the ER formulation can maintain more constant plasma concentrations than the IR formulation. Results of the simulation study indicated the feasibility of an ER formulation of acyclovir for twice daily administration. If the target in-vitro drug release and dose required for an ER formulation are known prior to initiation of formulation development, the number of experiments, cost and development time can be significantly reduced.