Antifungal activity of local anesthetics againstCandida species

Novel avenues for identification of new antifungal drugs and current challenges

INTRODUCTION

: Some of otherwise useful fungi are pathogenic to humans, and unfortunately, the number of these pathogens is increasing. In addition to common skin infections, these opportunistic pathogens are able to cause severe, often incurable, systemic mycoses.

AREAS COVERED

: The number of antifungal drugs is limited, especially drugs that can be used for systemic administration, and resistance to these drugs is very common. This review summarizes various approaches to the discovery and development of new antifungal drugs, provides an overview of the most important molecules in terms of basic (laboratory) research and compounds currently in clinical trials, and focuses on drug repurposing strategy, while providing an overview of drugs of other indications that have been tested in vitro for their antifungal activity for possible expansion of antifungal drugs and/or support of existing antimycotics.

EXPERT OPINION

: Despite the limitations of the research of new antifungal drugs by pharmaceutical manufacturers, in addition to innovated molecules based on clinically used drugs, several completely new small entities with unique mechanisms of actions have been identified. The identification of new molecular targets that offer alternatives for the development of new unique selective antifungal highly effective agents has been an important outcome of repurposing of non-antifungal drugs to antifungal drug. Also, given the advances in monoclonal antibodies and their application to immunosuppressed patients, it may seem possible to predict a more optimistic future for antifungal therapy than has been the case in recent decades.

Evaluation of antifungal susceptibility using flow cytometry

Flow cytometry has found wide applications in areas like haematology and immunology, but also presents great potential in microbiology. The susceptibility of clinical isolates of Candida and Cryptococcus to antifungal compounds can be assayed by flow cytometry using fluorescent probes like FUN-1, propidium iodide and JC-1, with several advantages. Following 1 or 2 h of incubation, depending on the antifungal compound, versus 48 h of the classical methods, it is possible to establish the different susceptibility profiles. Additionally, it provides information regarding the mechanisms of action and might infer about resistance mechanisms.

Local anesthetics as antimicrobial agents: a review

BACKGROUND

Since the introduction of cocaine in 1884, local anesthetics have been used as a mainstay of pain management. However, numerous studies over the past several decades have elucidated the supplemental role of local anesthetics as antimicrobial agents. In addition to their anesthetic properties, medications such as bupivacaine and lidocaine have been shown to exhibit bacteriostatic, bactericidal, fungistatic, and fungicidal properties against a wide spectrum of microorganisms.

METHODS

A comprehensive literature search was conducted using MEDLINE 1950-present for in vitro and in vivo studies pertaining to the antimicrobial activity of various local anesthetics on a broad range of bacterial and fungal pathogens. Studies testing the effect on microbial growth inhibition of local anesthetics alone and in combination with other agents, such as preservatives and other medications, as well as the effect of conditions such as concentration and temperature, were included for review. Outcome measures included colony counts, area-under-the-curve and time-kill curve calculations, minimum inhibitory concentrations, and post-antibiotic effect.

RESULTS

Evidence suggests that local anesthetics as a class possess inherent antimicrobial properties against a wide spectrum of human pathogens. Multiple local anesthetics at concentrations typically used in the clinical setting (e.g., bupivacaine 0.125%-0.75%; lidocaine 1%-3%) inhibit the growth of numerous bacteria and fungi under various conditions. Different local anesthetics showed various degrees of antimicrobial capacity; bupivacaine and lidocaine, for example, inhibit growth to a significantly greater extent than does ropivacaine. Greater concentrations, longer exposure, and higher temperature each correlate with a proportional increase in microbial growth inhibition. Addition of other agents to the anesthetic solutions, such as preservatives, opioids, or intravenous anesthetics such as propofol, modify the antimicrobial activity via either synergistic or antagonistic action. Limited studies attribute the mechanism of action of antimicrobial activity of local anesthetics to a disruption of microbial cell membrane permeability, leading to leakage of cellular components and subsequent cell lysis.

CONCLUSIONS

Local anesthetics not only serve as agents for pain control, but possess antimicrobial activity as well. In such a capacity, local anesthetics can be considered as an adjunct to traditional antimicrobial use in the clinical or laboratory setting. Additionally, caution should be exercised when administering local anesthetics prior to diagnostic procedures in which culture specimens are to be obtained, as the antimicrobial activity of the local anesthetic could lead to false-negative results or suboptimal culture yields.

Intrathecal baclofen does not inhibit the growth of different bacterial species and Candida albicans

BACKGROUND

The antimicrobial activity of intrathecal baclofen was investigated. Several different microorganisms were used: Staphylococcus aureus (beta-lactamase-positive and beta-lactamase-negative strains); S epidermidis; Enterococcus faecalis; Klebsiella pneumoniae; Escherichia coli; Pseudomonas aeruginosa; and Candida albicans.

METHODS

Three experimental approaches were used to assess baclofen antimicrobial activity: (1) determination of the MIC; (2) determination of the MBC; and (3) kinetic time-kill assay. Experiments were performed according to current methods of the NCCLS.

RESULTS

As compared with control organisms exposed to physiologic saline, organisms exposed to baclofen over a 10-day period failed to reduce the number of viable cells by at least 3 log(10), as requested by NCCLS criteria.

CONCLUSIONS

Because the viability of the investigated organisms was not reduced over that of microbial suspensions exposed to physiologic saline, we conclude that intrathecal baclofen has no measurable activity against different bacterial species and C albicans.

Susceptibility pattern among pathogenic species ofAspergillusto physical and chemical treatments

Physical treatments, like heating or irradiation, may reduce the viability or eradicate Aspergillus conidia, which in turn might help to prevent infections by members of this genus. Chemical treatments can also prevent infection resulting from contaminated hospital fabrics or surfaces. Our objectives were to study the kinetics of survival of the conidia of pathogenic Aspergillus species, like A. fumigatus, A. flavus and A. niger, during exposure to heating at 60 degrees C and microwave irradiation. In addition, we evaluated the susceptibility patterns of Aspergillus conidia to such chemical agents as cupric sulphate and sodium hypochlorite. Heating the conidia of A. flavus and A. niger at 60 degrees C for 45 min was found to be fungicidal (reduction > 104 conidia/ml), but was not with A. fumigatus conidia. Short periods of microwave irradiation (40 s) resulted in a significant reduction of the viability of the conidia of these three Aspergillus species as a result of lethal membrane lesions. All Aspergillus species were similarly susceptible to cupric sulphate and sodium hypochlorite. Therefore, heating, microwave and the chemical treatments tested impaired significantly the viability of Aspergillus conidia, supporting the use of these methods as preventive measures among patients at risk.

Comparison of two probes for testing susceptibilities of pathogenic yeasts to voriconazole, itraconazole, and caspofungin by flow cytometry

A cytometric approach to determine the susceptibilities of Candida spp. and Cryptococcus neoformans to voriconazole, itraconazole, and caspofungin is described. A total of 63 clinical isolates with different susceptibility patterns were exposed for 1, 2, 4, and 6 h to serial concentrations of each antifungal agent, followed by staining with two fluorescent probes: propidium iodide (PI) and FUN-1. FUN-1 was able to identify the susceptibility patterns of the assayed strains to the three agents after 1 h. PI penetrated a maximum of 50% of the cells treated with PI, at the highest concentration of caspofungin, 16 mug/ml, after 6 h of incubation (this percentage varied with the strain and was drug concentration and time of incubation dependent) and did not stain cells treated with high concentrations of either azole after 6 h. The use of FUN-1 appears to be an excellent fast and reliable alternative to the classical dilution method for determining the susceptibility of Candida spp. and C. neoformans to these three antifungal agents.

Novel method using a laser scanning cytometer for detection of mycobacteria in clinical samples

In order to evaluate the capacity of laser scanning cytometry (LSC) to detect acid-fast bacilli directly on clinical samples, a comparison between Kinyoun-stained smears analyzed under light microscopy and propidium iodide-auramine-stained smears analyzed by LSC was performed. The results were compared with those for culture on BACTEC MGIT 960. LSC is a new, reliable methodology to detect MYCOBACTERIA: