Antifungal Susceptibility Testing: A Primer for Clinicians

Synergistic antimicrobial system based on nisin and α-hydroxy organic acids

Synergistic antimicrobial is a promising way to overcome microbial contamination in food and drugs. In the study, the synergistic effect between nisin and α-hydroxy organic acids on E. coli and S. aureus was investigated. The experimental results showed that the combined antibacterial ability of nisin-citric acid system was the most prominent. The FCI index also indicated that the combination of nisin and citric acid had synergistic effects on E. coli. When nisin was combined with citric acid, the inhibition rates of E. coli and S. aureus were increased to 4.43 and 1.49 times, respectively. Nisin-citric acid complex system could effectively slow down the proliferation of S. aureus and E. coli at lower concentrations, and can quickly destroy the cell membrane after 4 h of action. Therefore, the combination of nisin and citric acid is expected to be a potential solution for food and drug preservation.

Aggregation-induced emission biomaterials for anti-pathogen medical applications: detecting, imaging and killing

Microbial pathogens, including bacteria, fungi and viruses, greatly threaten the global public health. For pathogen infections, early diagnosis and precise treatment are essential to cut the mortality rate. The emergence of aggregation-induced emission (AIE) biomaterials provides an effective and promising tool for the theranostics of pathogen infections. In this review, the recent advances about AIE biomaterials for anti-pathogen theranostics are summarized. With the excellent sensitivity and photostability, AIE biomaterials have been widely applied for precise diagnosis of pathogens. Besides, different types of anti-pathogen methods based on AIE biomaterials will be presented in detail, including chemotherapy and phototherapy. Finally, the existing deficiencies and future development of AIE biomaterials for anti-pathogen applications will be discussed.

Synergistic antimicrobial effect of nisin-octanoic acid nanoemulsions against E. coli and S. aureus

Food safety is a major public health concern all over the world. Therefore, the prevention of food contamination is becoming extremely crucial. In this study, an antimicrobial nanoemulsion composed of water-soluble nisin and fat-soluble octanoic acid was successfully prepared. The results showed that the average particle size and the polymer dispersity index of the nisin-octanoic acid (NOA) nanoemulsion were around 52.21 nm and 0.253, respectively. The NOA nanoemulsion required less amounts of nisin and octanoic acid to achieve the effective antimicrobial effect against Escherichia coli and Staphylococcus aureus. In addition, the growth curves of E. coli and S. aureus were determined. The OD₆₀₀ of NOA nanoemulsion was significantly lower than free nisin after being incubated for 24 h (p < 0.001), indicating that the antimicrobial effect of NOA nanoemulsion was outstanding. Meanwhile, the synergistic antimicrobial property of NOA nanoemulsion against E. coli and S. aureus was significantly better than free nisin under nonacid conditions (p < 0.05). Overall, the results of this study may provide guidance for the further application of nisin in more forms.

Rapid and high-throughput testing of antifungal susceptibility using an AIEgen-based analytical system

The increasing resistance among fungi to antimicrobials are posing global threats to health. Early treatment with appropriate antifungal drugs guided by the antifungal susceptibility testing (AFST) can dramatically reduce the mortality of severe fungal infections. However, the long test time (24-48 h) of the standard AFSTs cannot provide timely results due to the slow growth of the pathogen. Herein, we report a new AFST that is independent of growth rate analysis using a luminogen with aggregation-induced emission characteristics (AIEgen) named DMASP. DMASP is a water-soluble small-molecule probe that can readily penetrate the dense fungal cell wall. Based on its mitochondria-targeting ability and AIE characteristics, fungal activity can be dynamically indicated via real-time fluorescence monitoring. This allows fungal susceptibility to various antimicrobials to be assessed within 12 h in a wash-free, one-step manner. This method may serve as a promising tool to rapidly detect possible drug-resistant fungal strain and guide the precise use of antimicrobial against fungal diseases.

Don't mess with the machine - evaluation of fluconazole susceptibility testing for Candida glabrata using the new VITEK2 AST-YS08 card following species modification

A modification of fluconazole formulation in the VITEK2 AST-YS08 card revoked the fluconazole-Candida glabrata combination. An evaluation of AST-YS08 following C. glabrata to C. albicans adjustment within VITEK2 software revealed higher fluconazole MICs compared to AST-YS07 and E-test, with major discrepancies. This mandates an alternative approach to fluconazole-C. glabrata susceptibility testing.

Combined Antimicrobial Activity of Photodynamic Inactivation and Antimicrobials-State of the Art

Antimicrobial photodynamic inactivation (aPDI) is a promising tool for the eradication of life-threatening pathogens with different profiles of resistance. This study presents the state-of-the-art published studies that have been dedicated to analyzing the bactericidal effects of combining aPDI and routinely applied antibiotics in in vitro (using biofilm and planktonic cultures) and in vivo experiments. Furthermore, the current paper reviews the methodology used to obtain the published data that describes the synergy between these antimicrobial approaches. The authors are convinced that even though the combined efficacy of aPDI and antimicrobials could be investigated with the wide range of methods, the use of a unified experimental methodology that is in agreement with antimicrobial susceptibility testing (AST) is required to investigate possible synergistic cooperation between aPDI and antimicrobials. Conclusions concerning the possible synergistic activity between the two treatments can be drawn only when appropriate assays are employed. It must be noticed that some of the described papers were just aimed at determination if combined treatments exert enhanced antibacterial outcome, without following the standard methodology to evaluate the synergistic effect, but in most of them (18 out of 27) authors indicated the existence of synergy between described antibacterial approaches. In general, the increase in bacterial inactivation was observed when both therapies were used in combination.

Antifungal Therapy in Equine Ocular Mycotic Infections

Fungi are clinically important causes of ocular infections in the horse. Keratomycosis is the most common; however, a diverse range of mycotic infections, affecting numerous ocular tissues, may be encountered. Many equine mycoses are diagnostic and therapeutic challenges. Prompt and appropriate treatment is essential to minimize morbidity and reduce the likelihood of vision loss. Knowledge of the characteristics and properties of equine ophthalmology antifungal medications is essential to selecting an optimal treatment strategy, including selection of appropriate medication and effective administration route. Newer delivery methods and devices are available and can contribute to an improved outcome in select situations.

[Standardisation and validation of an HPLC method for determining serum posaconazole levels in Colombia]

BACKGROUND

Colombia currently does not have a specialised service for measuring antifungal levels in serum, which is of prime importance for the proper treatment and correct management of invasive fungal infections.

AIMS

To standardise and validate a simple, sensitive, and specific protocol, based on high performance liquid chromatography, complying with the parameters recommended by the Food and Drug Administration, to detect, identify, and quantify serum concentrations of posaconazole.

METHODS

A high performance liquid chromatography Agilent series-1 200 equipment was used with ultraviolet diode array detector and analytical column-Eclipse XDB-C18. Posaconazole-SCH56592 (batch IRQ-PAZ-10-X-103) was used as the primary control and itraconazole (batch ZR051211PUC921) was used as an internal control. The validation was performed taking into account all criteria recommended by the Food and Drug Administration (selectivity, calibration curves, recovery, accuracy, precision, sensitivity, reproducibility, and stability of the sample).

RESULTS

The most suitable chromatographic conditions were the following: column temperature 25°C, ultraviolet detection at 261nm, 50μl injection volume, flow volume 0.8ml/min, 10min running time, mobile phase of acetonitrile:water (70:30), and final retention times of 3.4 and 7.2min for posaconazole and itraconazole, respectively, with a wide and reliable quantification range (0.125μg/ml to 16μg/ml). Using these parameters, the method was selective, R² in the calibration curves was≥0.99, and the percentage recovery was 98.7%, with a coefficient of variation less than 10%. The relative error for accuracy and the coefficient of variation for precision were less than 15%, all meeting the acceptance criteria recommended by the Food and Drug Administration.

CONCLUSIONS

The selectivity and chromatographic purity of the obtained signal, as well as the standardised limits of detection and quantification, make this method an excellent tool for therapeutic monitoring of patients treated with posaconazole.

Antimalarial iron chelator FBS0701 blocks transmission by Plasmodium falciparum gametocyte activation inhibition

Reducing the transmission of the malarial parasite by Anopheles mosquitoes using drugs or vaccines remains a main focus in the efforts to control malaria. Iron chelators have been studied as potential antimalarial drugs due to their activities against different stages of the parasite. The iron chelator FBS0701 affects the development of Plasmodium falciparum early gametocytes and lowers blood-stage parasitemia. Here, we tested the effect of FBS0701 on stage V gametocyte infectivity for mosquitoes. The incubation of stage V gametocytes for up to 3 days with increasing concentrations of FBS0701 resulted in a significant dose-related reduction in mosquito infectivity, as measured by the numbers of oocysts per mosquito. The reduction in mosquito infectivity was due to the inhibition of male and female gametocyte activation. The preincubation of FBS0701 with ferric chloride restored gametocyte infectivity, showing that the inhibitory effect of FBS0701 was quenched by iron. Deferoxamine, another iron chelator, also reduced gametocyte infectivity but to a lesser extent. Finally, the simultaneous administration of drug and gametocytes to mosquitoes without previous incubation did not significantly reduce the numbers of oocysts. These results show the importance of gametocyte iron metabolism as a potential target for new transmission-blocking strategies.