Antimicrobial and anti-biofilm properties of oleuropein against Escherichia coli and fluconazole-resistant isolates of Candida albicans and Candida glabrata

BACKGROUND

Side effects associated with antimicrobial drugs, as well as their high cost, have prompted a search for low-cost herbal medicinal substances with fewer side effects. These substances can be used as supplements to medicine or to strengthen their effects. The current study investigated the effect of oleuropein on the inhibition of fungal and bacterial biofilm in-vitro and at the molecular level.

MATERIALS AND METHODS

In this experimental study, antimicrobial properties were evaluated using microbroth dilution method. The effect of oleuropein on the formation and eradication of biofilm was assessed on 96-well flat bottom microtiter plates and their effects were observed through scanning electron microscopy (SEM). Its effect on key genes (Hwp1, Als3, Epa1, Epa6, LuxS, Pfs) involved in biofilm formation was investigated using the quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) method.

RESULTS

The minimum inhibitory concentration (MIC) and minimum fungicidal/bactericidal concentration (MFC/MBC) for oleuropein were found to be 65 mg/ml and 130 mg/ml, respectively. Oleuropein significantly inhibited biofilm formation at MIC/2 (32.5 mg/ml), MIC/4 (16.25 mg/ml), MIC/8 (8.125 mg/ml) and MIC/16 (4.062 mg/ml) (p < 0.0001). The anti-biofilm effect of oleuropein was confirmed by SEM. RT-qPCR indicated significant down regulation of expression genes involved in biofilm formation in Candida albicans (Hwp1, Als3) and Candida glabrata (Epa1, Epa6) as well as Escherichia coli (LuxS, Pfs) genes after culture with a MIC/2 of oleuropein (p < 0.0001).

CONCLUSIONS

The results indicate that oleuropein has antifungal and antibacterial properties that enable it to inhibit or destroy the formation of fungal and bacterial biofilm.

Isolation and investigation of external reproduction tract mycoflora in healthy male cats

BACKGROUND

Various infectious agents can infect the male reproductive system.

OBJECTIVES

The aims of this study were to provide current data on fungal and yeast flora of the external organs of reproductive system of male short hair cats including penis and prepuce.

METHODS

In total 28 samples were taken from external genital system of male stray cats using sterilised cotton swabs. Samples were taken based on the absence of any reproductive complications using physical examinations. The samples were transferred to sterilised Stuart transport media and were then incubated in the Sabouraud dextrose agar with chloramphenicol at 32°C for 48 h. The identification of fungi and yeasts was confirmed by germ tube formation test, CHROM agar, urease testing and Corn meal agar medium with Tween 80.

RESULTS

Fungal agents were isolated from 7 (25%) out of 28 male stray cats. Fungal isolates were obtained from the penis and prepuce of 4 (36%) and 7 (100%) male cats, respectively. The most commonly recovered species samples were Candida krusei (3.75%) and Penicillum spp. (6.86%) from the penis and prepuce of the cats, respectively. The external organs of male reproduction of cats were infected with 2-4 different fungal agents. Only 5 (45%) cats were infected with one fungus; however, in 6 (55%) cats, mixed fungal infections were isolated. Cats 3-4 years old had the highest fungal contamination in the prepuce region (4/7), while the penis at this age had the least contamination (1/4).

CONCLUSIONS

It is concluded that the external reproduction organs of male cats could be infected by different fungal agents.

Antifungal susceptibility profile of yeasts isolated from the oral cavity of cats

BACKGROUND

Microorganisms living in the oral cavity play an important role in health and disease of the host. Cats are susceptible to oral infections, and it is documented that fungi in the oral cavity could impact these infections. Antifungal resistance has been increasing in recent years.

OBJECTIVES

This study was designed to identify yeast isolates from the oral cavity of healthy cats and to evaluate their antifungal susceptibility pattern.

METHODS

Oral specimens were collected from 60 cats and cultured at 37°C for 10 days. Yeasts were isolated and identified. Their antifungal susceptibility pattern was determined according to CLSI M44-A.

RESULTS

Three yeast genera were isolated, including Candida spp (55.5%), Rhodotorula spp (33.3%) and Hanseniaspora spp (11.1%). Antifungal susceptibility profiling showed that, apart from a dose-dependent effect of itraconazole, Hanseniaspora spp was susceptible to all seven drugs studied. The Candida species were susceptible to all drugs except ketoconazole (sensitivity 80%) and caspofungin (sensitivity 40%). In R. glutinis and R. minuta, 100% sensitivity was observed for amphotericin B, posaconazole, ketoconazole and voriconazole.

CONCLUSIONS

The results suggest that, in comparison with humans and other animals, cats have a different oral mycoflora in terms of species, number and diversity. However, these isolates have similar susceptibility patterns to those seen in isolates from other animals and humans. More studies should be done to further characterize the oral mycobiota of cats and its role in oral infections.

Sheep serve as a reservoir of Trichophyton mentagrophytes genotype V infection

Human infections by Trichophyton mentagrophytes occur mainly due to contact with diseased animals. In Iran, T. mentagrophytes genotype V is the most prevalent variant of the fungus. We aimed to determine the animal reservoir of T. mentagrophytes genotype V infection. The study was done on a total of 577 dermatophyte strains obtained from animals with signs of dermatophytosis and human patients. The list of extensively sampled animals included sheep, cows, cats and dogs. For human cases, epidemiological data were collected. All dermatophyte isolates from animals along with 70 human isolates morphologically similar to T. verrucosum and T. mentagrophytes genotype V were identified by rDNA internal transcribed spacer region restriction fragment length polymorphism analysis and DNA sequencing. A total of 334 animal dermatophyte strains were identified as Microsporum canis, T. mentagrophytes genotype V, T. verrucosum, Nannizzia gypsea, T. mentagrophytes genotype II*, T. mentagrophytes genotype VII, T. quinckeanum, and N. fulva. All clinical isolates identified as T. mentagrophytes genotype V originated from skin and scalp infections. Almost all veterinary isolates of T. mentagrophytes genotype V were cultured from sheep, but epidemiological data on animal-to-human transmission of T. mentagrophytes genotype V infection were limited and we found evidence in favor of interhuman transmission. In Iran, sheep maintain T. mentagrophytes genotype V population and therefore serve as animal reservoir of respective infections. The role of sheep as the source of human dermatophytosis due to T. mentagrophytes genotype V isolates is yet to be proven.

Influence of menthol on biofilm formation, ergosterol content, and cell surface hydrophobicity of Candida glabrata

Resistance to synthetic antifungals has become one of the leading public health challenges around the world. Accordingly, novel antifungal products like naturally occurring molecules can be one of the potential ways to reach efficient curative approaches to control candidiasis. This work evaluated the effect of menthol on cell surface hydrophobicity (CSH), biofilm formation, growth, and ergosterol content of Candida glabrata, a yeast with a high resistance against antifungal agents. Disc diffusion method (susceptibility to synthetic antifungals), broth micro-dilution method (Susceptibility to menthol), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide reduction assay (biofilm formation), High-performance liquid chromatography (HPLC) technique (ergosterol content), and adherence to n-hexadecane (CSH) were employed to determine the influence of menthol against C. glabrata isolates. The minimum inhibitory concentration (MIC) range of menthol versus C. glabrata was 1250-5000 µg/mL (mean ± SD: 3375 ± 1375 µg/mL). The mean rate of C. glabrata biofilm formation was decreased up to 97.67%, 81.15%, 71.21%, 63.72%, 47.53%, 26.31%, and 0.051% at 625, 1250, 2500, 5000, 10 000, 20 000, and 40 000 µg/mL concentrations, respectively. The percentages of CSH were significant in groups treated with MIC/2 (17.51 ± 5.52%) and MIC/4 (26 ± 5.87%) concentrations of menthol. Also, the percentage changes in membrane ergosterol were 15.97%, 45.34%, and 73.40% at 0.125, 0.25, and 0.5 mg/mL concentrations of menthol, respectively, in comparison with untreated control. The results showed the menthol impact versus sessile and planktonic C. glabrata cells, and the interference with ergosterol content, CSH, and biofilm formation, which made it a potent natural antifungal.

Descriptive epidemiology of dermatophytosis in rodents

INTRODUCTION

Dermatophytosis is a zoonotic disease caused by a group of keratinophilic fungi called dermatophytes.

OBJECTIVES

Since the epidemiology of diseases revolves over time, this research studies the incidence of dermatophytosis among rodents referred to mycology laboratory during 2019-2021.

METHODS

A total of 163 rodents including rabbits, guinea pigs, and hamsters suspecting having dermatophytosis were sampled by scraping lesions. Direct microscopic examination, culture, and polymerase chain reaction were done for diagnosis of dermatophytosis and identification of the etiologic agent.

RESULTS

The results of this study showed that 37.4% of rodents were involved with dermatophytosis, among which 41.13% of rabbits, 25% of guinea pigs, and 26.3% of hamsters were included. Microsporum canis (52.7%) was the most isolated agent. Incidence of dermatophytosis was higher in female in rabbits while in hamsters and guinea pigs male were mostly infected. Rodents less than 6 months were more susceptible for dermatophytosis except for hamsters in which 6-12 months animals had a higher prevalence.

CONCLUSION

In conclusion, it is significant to update our knowledge about the epidemiology of dermatophytosis in rodents and other animals every few years to define valid preventive strategies. Moreover, since dermatophytes are contagious and zoonotic, it is also a priority to apply preventing methods for dermatophytosis and treat infected rodents with appropriate antifungal agents to decrease the risk of infection.

P082 Synergistic activity, anti-adherence and anti-fungal abilities of fluconazole and voriconazole combined with thymol and carvacrol against C andida species

 

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM

Objectives

The current study aimed to assess the anti-adherence and antifungal activities of thymol and carvacrol against Candida albicans, C. glabrata, and C. krusei isolates obtained from patients with oral candidiasis concerning growth inhibition and fungal death as compared to the synthetic antifungals such as fluconazole and voriconazole.

Methods

The susceptibility assay for the test compounds was performed using the disk diffusion method against all Candida isolates. Also, anti-adherence activity was examined using a rapid and highly reproducible 96 well microtiter-based method.

Results

Both natural phenols and antifungal drugs revealed various efficacies against studied Candida species. The susceptibility to fluconazole and voriconazole were 100% for C. albicans, 50% and 90% for C. glabrata, and 0% and 100% for C. krusei isolates, respectively. The mean diameter of the inhibition zone was greater for thymol than carvacrol in C. albicans (19.89-0.80 mm vs 17.05-0.61 mm), C. glabrata (18.87-0.71 mm vs 15.77-0.57 mm), and C. krusei (15.11-0.91 mm vs 13.91-1.04 mm) isolates tested.

Thymol showed more effective inhibition on adherence of all Candida species than other treatments. The mean relative adherence ratios for C. albicans, C. glabrata, and C. krusei were 0.50, 0.60, and 0.64, respectively.

Conclusions

This study demonstrated significant inhibitory properties of thymol and carvacrol on the adherence and growth of azole susceptible- and -resistant Candida isolates. Also, thymol was more effective for preventing the adherence of yeast cells to polystyrene in comparison to carvacrol.

S2.4d Combination antifungal effects of eugenol with voriconazole against Candida tropicalis and Candida krusei strains isolated from the genital tract of mares

 

S2.4 Veterinary mycology research, September 21, 2022, 3:00 PM - 4:30 PM

Objectives

The objective of the current study was to investigate the possibility that eugenol synergizes the antifungal effects of voriconazole on genital isolates of Candida krusei and Candida tropicalis from mares.

Methods

The antifungal activity of eugenol and voriconazole was evaluated using the broth microdilution assay (CLSI- M27-A3). The synergism of eugenol and voriconazole against genital Candida isolates was evaluated by the microdilution checkerboard method.

Results

Minimum inhibitory concentration (MIC) values for eugenol and voriconazole ranged from 400 to 800 μg/ml and 1 to 8 μg/ml, respectively, for C. tropicalis isolates, and from 200 to 400 μg/ml for eugenol and 2 to 16 μg/ml for voriconazole against C. krusei isolates. Eugenol decreased the arithmetic mean of MIC for voriconazole against C. tropicalis and C. krusei isolates from 2.66 to 0.46 μg/ml and 7.77 to 0.41 μg/ml respectively. The fractional inhibitory concentration index (FICI) values for the eugenol voriconazole combination ranged from 0.25 to 0.88 and 0.19 to 0.63 for C. tropicalis and C. krusei isolates respectively. A synergistic effect of eugenol in combination with voriconazole was observed for 83.3% of C. tropicalis and 77.7% of C. krusei isolates. The antagonistic activity was not seen in any of the isolates tested.

Conclusions

Eugenol showed fungistatic and fungicidal effects against genital Candida isolates and, in combination, synergized the antifungal effects of voriconazole. The eugenol-voriconazole combination can lay the foundation for a therapeutic approach against isolates in which azole resistance has increased over time.

Potential antifungal impact of citral and linalool administered individually or combined with fluconazole against clinical isolates of Candida krusei

Introduction: Candida krusei is recognized as a major fungal pathogen in patients with immunodeficiency disorders. The present study aimed at investigating the anticandidal activities of citral and linalool combined with fluconazole (FLZ) against FLZ-resistant C. krusei strains. Methods: Antifungal activities were evaluated by the broth microdilution (MD) method to determine the minimum inhibitory and fungicidal concentrations (namely, MICs and MFCs) according to the Clinical and Laboratory Standards Institute (CLSI) M27-A3 document. The interactions were further evaluated using fractional inhibitory concentration indices (FICIs) for combinations of citral+FLZ and linalool+FLZ, calculated from checkerboard MD assays. Results: The mean ± standard deviation (SD) MIC values of citral, linalool, and FLZ against the C. krusei isolates were 70.23 ± 17, 150 ± 38.73, and 74.66 ± 36.95 μg/mL, respectively. Some fungicidal activities were also observed for citral (2.5) and linalool (1.53) against the C. krusei isolates. The FICI values of citral+FLZ and linalool+FLZ for the C. krusei isolates ranged from 0.4 to 1.00 and 0.19 to 0.63, respectively. The additive and synergistic interactions of linalool + FLZ were further observed in 12 (57.1%) and 9 (42.9%) C. krusei isolates. However, there was an additive interaction for citral + FLZ in 17 (80.9%) isolates. They also showed a synergistic interaction in only four (19.1%) isolates. Moreover, linalool and citral plus FLZ did not have any antagonistic effect on any isolates. Conclusion: The study findings support the possible capabilities of citral and linalool, as anticandidal agents, and FLZ might be supplemented with citral and/or linalool for treating FLZ-resistant C. krusei infections.

Efficacy of Syzygium aromaticum essential oil on the growth and enzymatic activity of pathogenic Candida albicans strains

BACKGROUND AND PURPOSE

Candida albicans (C. albicans) is the most common human pathogen owing to the most virulence factors. It seems that extracellular hydrolytic enzymes play a key role in C. albicans pathogenicity. The present study aimed to assess the susceptibility and enzymatic activity of pathogenic C. albicans isolates exposed to the Syzygium aromaticum (S. aromaticum) essential oil.

MATERIALS AND METHODS

S. aromaticum oil was characterized using gas chromatography-mass spectrometry (GC-MS). The broth microdilution technique (CLSI, M27-A3) was used to determine the minimum inhibitory concentration (MIC) of test compounds. Furthermore, before and after treatment with S. aromaticum essential oil, the yeasts were analyzed regarding the proteinase (Prz), hemolysin (Hz), and phospholipase (Phz) production/activity.

RESULTS

β-caryophyllene (12.76%) was found to be the major constituent in the essential oil after eugenol (84.64%). Only one isolate of C. albicans showed the antifungal resistance to fluconazole. All isolates were susceptible to S. aromaticum essential oil with MIC of 625-1250 μg/ml. S. aromaticum oil represented the best antifungal effect against C. albicans at MIC 1000 μg/ml. The mean±SD enzyme activity of C. albicans not exposed to S. aromaticum essential oil was obtained at 0.55±0.03, 0.73±0.04, and 0.61±0.05 for proteinase, hemolysin, and phospholipase, respectively. The activities of these enzymes were reduced significantly (P<0.05) to 0.33±0.06, 0.40±0.04, and 0.16±0.03 for phospholipase, proteinase, and hemolysin, respectively, after the yeasts were subjected to S. aromaticum essential oil.

CONCLUSION

The present study aimed to determine the ability of S. aromaticum essential oil to prevent the growth of C. albicans and decrease their enzymatic activity. As a natural antifungal agent, S. aromaticum can be utilized in pharmaceutical systems.

Effects of Bunium persicum essential oil on the reduction of spore germination, growth, and expression of FUM1 and FUM14 genes in Fusarium verticillioides isolates

Background and Purpose

Black Cumin of Kerman (Bunium persicum) is an Iranian plant that is commonly used as an antispasmodic, carminative, and antimicrobial substance. The present study aimed to assess different components of the essence of B. persicum and its effect on antifungal activity, spore germination inhibition, and expressions of FUM1 and FUM14 genes in Fusarium verticillioides strains.

Materials and Methods

The essence was extracted by hydrodistillation and analyzed through gas chromatography-mass spectroscopy. A broth microdilution method was used for the determination of the minimum inhibitory concentration (MIC). In addition, the expression of FUM1 and FUM14 genes of toxigenic F. verticillioides was assessed by using the real-time polymerase chain reaction (RT-PCR) technique.

Results

Based on the findings, most of the essence consisted of γ-terpinene (15.56%), propanal, and 2-methyl-3-phenyl (14.18%). The oil showed a good antifungal activity (mean MIC value: 2556.8 μg/ml) as well as the inhibition of spore germination and mycelial growth (P<0.05). The RT-PCR demonstrated that the expression levels of FUM1 and FUM14 of B. persicum-treated F. verticillioides were 0.43 and 0.53 folds lower than the control samples, respectively.

Conclusion

These findings revealed that the essential oil of B. persicum has different components responsible for the inhibition of mycelial growth and spore germination of F. verticillioides as well as reduction of expressions of FUM1 and FUM14 genes involving fumonisin production.

In vitro activity of encapsulated lactic acid bacteria on aflatoxin production and growth of Aspergillus Spp

This study aimed to investigate the potential ability of simultaneously used L. acidophilus(LA-5), L.rhamnosus(LGG), and L.casei(LC-01) in encapsulated (E) and nonencapsulated (NE) forms in mycelial growth of Aspergillus spp and aflatoxin production by A. flavus. In order to assess the zone of fungal growth inhibition by E and NE lactic acid bacteria, the agar well diffusion method was applied. Quantification of aflatoxin was performed using a high-performance liquid chromatography technique. Lactic acid bacteria exhibited high antifungal activity and significantly reduced AFB1, AFB2, AFG1, and AFG2 production in both E and NE forms compared to the control group. The percentage of reduction in total AFs production in treated samples with E and NE lactic acid bacteria was 94.1% and 95.5%, respectively. These results suggested that simultaneously used lactic acid bacteria in E and NE forms can prevent growth and decrease aflatoxin production of toxigenic aspergilla.

In vitro synergy of eugenol on the antifungal effects of voriconazole against Candida tropicalis and Candida krusei strains isolated from the genital tract of mares

BACKGROUND

Due to the limited range of antifungals available to treat genital Candida infections and the emergence of resistant isolates, attention has focused on the antifungal potency of natural compounds with promising biological properties.

OBJECTIVES

To examine whether eugenol synergises the in vitro efficacy of voriconazole against Candida strains isolated from the genital tract of mares.

STUDY DESIGN

In vitro experiment.

METHODS

The antifungal activity of eugenol and voriconazole was evaluated using the broth microdilution assay (CLSI- M27-A3). Synergism of eugenol and voriconazole against genital Candida isolates was evaluated by the microdilution checkerboard method.

RESULTS

Minimum inhibitory concentration (MIC) values for eugenol and voriconazole ranged from 400 to 800 µg/mL and 1 to 8 µg/mL, respectively, for C. tropicalis isolates, and from 200 to 400 µg/mL for eugenol and 2 to 16 µg/mL for voriconazole against C. krusei isolates. Eugenol decreased the arithmetic mean MIC for voriconazole against C. tropicalis and C. krusei isolates from 2.66 to 0.46 µg/mL and 7.77 to 0.41 µg/mL respectively. The fractional inhibitory concentration index (FICI) values for the eugenol-voriconazole combination ranged from 0.25 to 0.88 and 0.19 to 0.63 for C. tropicalis and C. krusei isolates respectively. A synergistic effect of eugenol in combination with voriconazole was observed for 83.3% of C. tropicalis and 77.7% of C. krusei isolates. Antagonistic activity was not seen in any of the isolates tested.

MAIN LIMITATIONS

Since in vitro antifungal susceptibility tests are not systematic analyses, any selection bias could influence the results. In addition, in vitro susceptibility does not uniformly predict clinical success in vivo.

CONCLUSIONS

Eugenol showed fungistatic and fungicidal effects against genital Candida isolates and, in combination, synergised the antifungal effects of voriconazole. The eugenol-voriconazole combination can lay the foundation for a therapeutic approach against isolates in which azole resistance has increased over time.

Antimicrobial Activity of Polylactic Acid Film Incorporated With Marjoram and Clove Essential Oils on Microbial and Chemical Properties of Minced Beef During Refrigerated Storage

Background: Active packaging is one of the new packaging technologies which causes interaction between packaging material and food with the aim of food shelf life extension while maintaining food safety and quality. Biodegradable films like polylactic acid (PLA) can be good alternatives to non-biodegradable plastics because of environmental pollution and concerns about the limitations of petroleum resources. Objective: This study was conducted to evaluate the efficacy of PLA film incorporated with marjoram and clove essential oils (EOs) (0.5 and 1% v/v) in maintaining the microbial and chemical quality of minced beef during refrigerated storage. Materials and Methods: Minced beef was packaged with PLA film incorporated with marjoram and clove EOs (0.5 and 1% v/v) alone and in combination and stored at refrigerator temperature for 10 days. Then, microbiological and chemical analyses were done at 0, 2, 4, 7 and 10 days of examination. Results: A reduction of 1 log CFU/g in total count was observed between groups with simultaneous use of EOs and control group (P<0.05) at day 7; however, there was not any significant difference between the mentioned groups at day 10. Active packaging with marjoram and clove EOs decreased the number of psychrotrophs in comparison to the control group and it was more evident at days 7 and 10. The number of Enterobacteriaceae in control and 1% clove EO/1% marjoram EO groups showed a difference of 3 log units at day 10. TVB-N of 1% clove EO/1% marjoram EO and 0.5% clove EO/1% marjoram EO showed significant differences from control at day 10 (P<0.05). Conclusion: The results of the current study have shown that the active PLA films can be a promising approach in order to maintain microbial and chemical quality of minced beef at refrigerator temperature for 10 days.

Evaluation of Antimicrobial Activity of Cymbopogon citratus Essential Oil Alone and in Combination with Origanum majorana and Caryophyllus aromaticus Essential Oils against Some Foodborne Bacteria

Background: Food spoilage and foodborne diseases are two important problems in the food industry. On the other hand, consumers’ tendency to use natural additives is increasing. Hence, plant essential oils (EOs) can be safe alternatives in this regard. Objective: The objectives were to determine the chemical composition and to evaluate the antimicrobial activity of Cymbopogon citratus EO against some foodborne bacteria alone and in combination with Origanum majorana and Caryophyllus aromaticus EOs. Materials and Methods: Chemical composition of C. citratus EO was analyzed by gas chromatography-mass spectrometry. Further, antibacterial activity of the EO against foodborne bacteria was assessed using disk diffusion method. In addition, the minimum inhibitory concentration of the EO was determined by microdilution broth method and then the minimum bactericidal concentration value was determined. Checkerboard synergy testing was also performed to determine the fractional inhibitory concentration index. Finally, time-kill curves were drawn based on the bacterial population (CFU/mL) against time (h). Results: The major compounds of C. citratus EO were isothymol, thymol, trans-caryophyllene, and cymene. The most and the least sensitive foodborne bacteria to C. citratus EO were Staphylococcus aureus and Bacillus subtilis, respectively. The minimum inhibitory concentration (MIC) values of C. citratus EO against all the evaluated bacteria were 0.1% and The minimum bactericidal concentration (MBC) values ranged between 0.1 and >2% (v/v). The combination of C. citratus and O. majorana EOs showed a synergistic activity against Salmonella typhimurium and partial synergism against B. subtilis, Escherichia coli O157:H7, S. aureus, and Listeria monocytogenes. Moreover, the combination of C. citratus and C. aromaticus EOs demonstrated partial synergism against S. aureus and L. monocytogenes, and additive interaction against S. typhimurium; however, the combination was indifferent against E. coli O157:H7 and B. subtilis. Furthermore, C. citratus plus O. majorana EOs and C. citratus plus C. aromaticus EOs showed a bactericidal effect against S. typhimurium after 24 hours in the time-kill assay. Conclusion: In general, the synergism, partial synergism, and additive effects of C. citratus in combination with C. aromaticus and O. majorana EOs strengthen the antimicrobial activity, expand the spectrum of activity, reduce the concentrations required, decrease the side effects, and prevent the alteration of organoleptic properties of food.

Concurrent production of sodium lignosulfonate and ethanol from bagasse spent liquor

This study was done with the aim of lignosulfonate and ethanol production from different spent liquors of bagasse pulping process. For this purpose, alkali lignin from bagasse alkali liquor was separated and was sulfomethylated to produce soda lignosulfonate (SLig). Furthermore, raw bagasse was directly treated with sodium sulfite in acidic and neutral conditions to produce BLig and NLig bagasse lignosulfonate, respectively. In addition, the pentoses and hexoses impurities in lignosulfonates were fermented to ethanol using Candida guilliermondii. Results showed that the molecular weight of NLig lignosulfonate was considerably high comparing to the SLig and BLig lignosulfonates. A high level of thermal resistance was found in case of SLig regarding to the other samples at 500 °C. Fermentation of the spent liquors with Candida guilliermondii led to a maximum ethanol yield of 7.0, 1.0 and 5.1 g L^-1 in NLig, SLig and BLig, respectively.

Potential effect of 2-isopropyl-5-methylphenol (thymol) alone and in combination with fluconazole against clinical isolates of Candida albicans, C. glabrata and C. krusei

Limitations of antifungals used in the treatment of candidiasis, as the development of resistant strains, are known by the scientific community. In this context, the aim of this study was to investigate the activity of 2-isopropyl-5-methylphenol (thymol) in combination with fluconazole (FLZ) against clinical Candida strains. The antifungal activity of thymol along with FLZ was evaluated by the Clinical Laboratory Standards Institute (CLSI) M27-A2 broth microdilution method. In addition, synergism was observed for clinical strains of Candida spp. with combination of thymol-FLZ evaluated by the chequerboard microdilution method. The mean of minimum inhibitory concentration (MIC) values of thymol and FLZ were 49.37 and 0.475μg/ml for C. albicans, 51.25 and 18.80μg/ml for C. glabrata and 70 and 179.20μg/ml for C. krusei strains, respectively. Thymol in combination with FLZ exhibited the synergistic effects against all species of Candida tested. FICI values for thymol plus FLZ ranged from 0.366 to 0.607 for C. albicans strains, 0.367 to 0.482 for C. glabrata strains, and 0.375 to 0.563 for C. krusei strains. No antagonistic activity was seen in the strains tested. Thymol was found to have a fungicidal effect on Candida species and a synergistic effect when combined with FLZ.

Chemical composition, antioxidant activity and antifungal effects of five Iranian essential oils against Candida strains isolated from urine samples

Systemic candidiasis has become an emerging fungal infection in recent years. Anti-Candida resistance to conventional antifungal agents has subsequently increased. This study reported the chemical composition, antioxidant and anti-Candida activity of Origanum majorana, Artemisia dracunculus, Cymbopogon citrate, Cinnamomum verum and Caryophyllus aromaticus essential oils. Different Candida species, from urine tracts of hospitalized patients, were included to be challenged with understudied essential oils. Chemical compositions were determined using gas chromatography/mass spectroscopy (GC/MS) analysis and antioxidant activity was measured using DDPH assay. MIC of these essential oils was evaluated using broth micro-dilution test. Caryophyllus aromaticus had the highest antioxidant activity while the lowest antioxidant activity was for Artemisia dracunculus. MICs of Cinnamomum verum, Caryophillium aromaticus, Artemisia dracunculus, Origanum vulgare and Cymbopogon citratus essential oils ranged from 125 to 175μg/mL (mean value: 147.7±25.5μg/mL), 700 to 1000μg/mL (mean value: 740.9±105.4μg/mL), 1000 to 2000μg/mL (mean value: 1454.5±509.6μg/mL), 173 to 350μg/mL (mean value: 208±55.8μg/mL) and 125 to 175μg/mL (mean value: 156.8±24.6μg/mL) for different Candida species, respectively. In general, natural compounds are suitable to be used as anti-Candida and antioxidant agents. However in this stage, these compounds could be applied as supplementary agents along with conventional antifungal drugs.

Fungicidal efficacy of various honeys against fluconazole-resistant Candida species isolated from HIV+ patients with candidiasis

OBJECTIVE

Honey is well known to possess a broad spectrum of activity against medically important organisms. The purpose of this study was to assess the antifungal activity of different honeys against 40 fluconazole (FLU) resistant Candida species, including Candida albicans (C. albicans), Candida glabrata, Candida krusei and Candida tropicalis.

MATERIALS AND METHODS

Three honey samples were collected from northern (Mazandaran, A), southern (Hormozgan, B) and central (Lorestan, C) regions of Iran. A microdilution technique based on the CLSI, M27-A2 protocol was employed to compare the susceptibility of honeys "A", "B" and "C" against different pathogenic Candida isolates.

RESULTS

The results showed that different Candida isolates were resistant to FLU, ranging from 64μg/mL to 512μg/mL. All of the honeys tested had antifungal activities against FLU-resistant Candida species, ranging from 20% to 56.25% (v/v) and 25% to 56.25% (v/v) for minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs), respectively. Honey "A" (MIC: 31.59%, v/v) showed higher anti-Candida activity than honey "B" (MIC: 35.99%, v/v) and honey "C" (MIC: 39.2%, v/v). No statistically significant differences were observed among the mean MIC values of the honey samples (P>0.05). The order of overall susceptibility of Candida species to honey samples were; C. krusei>C. glabrata>C. tropicalis>C. albicans (P>0.05). In addition, the mean MICs of Candida strains isolated from the nail, vagina and oral cavity were 33.68%, 36.44% and 39.89%, respectively, and were not significantly different (P>0.05).

CONCLUSION

Overall, varying susceptibilities to the anti-Candida properties of different honeys were observed with four FLU-resistant species of Candida. Further research is needed to assess the efficacy of honey as an inhibitor of candidal growth in clinical trials.

Antifungal activity and influence of propolis against germ tube formation as a critical virulence attribute by clinical isolates of Candida albicans

OBJECTIVE

The potentiality to switch between yeast and hyphal morphologies plays an important role in the virulence of Candida albicans (C. albicans). The objective of the present study was to evaluate the chemical composition, antifungal activity and influence of propolis upon germ tube formation of C. albicans clinical isolates.

METHODS

The major compounds of propolis ethanolic extract (PEE) was revealed by gas chromatography-mass spectrometry (GC/MS) analysis. Broth microdilution method was used for determination of minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) of this extract. C. albicans isolates were exposed to sub-MIC concentrations of propolis and germ tube reduction percent (GRP) and morphological transition from yeast to filamentous form were monitored microscopically.

RESULTS

Phenolic compounds, aromatic acids, aliphatic acids, sugars and polycyclic aromatic hydrocarbons were the major compound classes in PEE. Mean of MIC and MFC values of PEE against C. albicans isolates were 360.6μg·mL^-1 and 1250.1μg·mL^-1, respectively. The increase in concentration led to a significant reduction in germ tube formation, so mean of GRP was 36.7±11.1 and 22±10.1 at concentration of ½ MIC and ¼ MIC of PEE, respectively.

CONCLUSIONS

In conclusion, the present study indicated that PEE has interesting potential as a therapeutic agent that targets germ tube formation by C. albicans as a critical virulence factor.

Chemical composition and antifungal activity of Satureja hortensis L. essentiall oil against planktonic and biofilm growth of Candida albicans isolates from buccal lesions of HIV(+) individuals

ETHNOPHARMACOLOGICAL RELEVANCE

Oral candidiasis is an opportunistic infection of the oral cavity which usually occurs in the immunocompromised individuals. Candida albicans (C. albicans) is the most common species of yeast responsible for oral candidiasis. This study investigated the effects of Satureja hortensis L. essentiall oil (EO) on the planktonic, biofilm formation and mature biofilms of C. albicans isolates from buccal lesions of HIV(+) individuals.

MATERIALS AND METHODS

MTT reduction assay, broth micro-dilution method and scanning electron microscopy (SEM) were employed to determine the effect of mentioned EO on the C. albicans planktonic and biofilm forms. GC-GC/MS was used to detect the major active compounds of EO.

RESULTS

Thymol (45.9%), gamma-terpinen (16.71%), carvacrol (12.81%) and p-cymene (9.61%) were found as the most abundant constituents. MIC values ranged from 250 to 400 μg/ml and MFC values ranged from 350 to 500 μg/ml. All C. albicans isolates formed biofilm on polystyrene plats but the quantity of biofilm mass (optical density) was different for the isolates ranging from 0.850 to 0.559 nm. The mean of biofilm formation by C. albicans isolates was reduced by 87.1 ± 3.7%, 73.6 ± 5.1%, 69.4 ± 5.3% and 67 ± 4.2% at 4800, 3200, 2400 and 1600 μg/ml, respectively. In sub-MIC concentration, SEM analysis revealed loosening of cells, deformity of three dimensional structures of biofilms and shrinkage in cell membranes of sessile cells.

CONCLUSIONS

In conclusion, the substantial anti-fungal activity showed by S. hortensis L. EO suggests exploitation of this oil as potential natural anti-biofilm product to deal with the problem of buccal cavity lesion associated with C. albicans.

Evaluation of antioxidant and antifungal properties of the traditional plants against foodborne fungal pathogens

OBJECTIVE

To determine the antioxidant and antifungal activities of the essential oils from five aromatic herbs, including Thymus vulgaris, Chamaemelum nobile, Ziziphora clinopodioides, Zingiber officinale and Cuminum cyminum, against different Aspergillus and Penicillium species.

METHODS

The oils were subjected to screening for their possible antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The susceptibility test for the oils was carried out in terms of minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) using microdilution method.

RESULTS

The values of the essential oils in DPPH assay were as follows: T. vulgaris (450.11±5.23 μg/mL), Ch. nobile (602.73±4.8 μg/mL), Ziz. clinopodioides (1238.82±9.3 μg/mL), Cu. cyminum (1255.52±8.92 μg/mL) and Zin. officinale (5595.06±8.24 μg/mL). Our findings also indicated a strong activity against tested fungi for the oil of T. vulgaris (1250 μg/mL), followed by Cu. cyminum (1416 μg/mL), Zin. officinale (1833 μg/mL), Ziz. clinopodioides (2166 μg/mL) and Ch. nobile (3750 μg/mL). This study confirmed the excellent antifungal and antioxidant properties of the essential oils, especially T. vulgaris, against foodborne pathogenic fungi.

CONCLUSION

Owing to their strong protective features, these oils could be used in ethno-medicine as preventers of lipid peroxidation and cellular damage, and in food industries as preservers of foodstuffs against spoilage fungi. Also, they could be the candidates to develop new antibiotics and disinfectants to control infective agents.

Antifungal activity of essential oils from Iranian plants against fluconazole-resistant and fluconazole-susceptible Candida albicans

OBJECTIVE

The purpose of this study was to assay the antifungal activity of selected essential oils obtained from plants against both fluconazole (FLU)-resistant and FLU-susceptible C. albicans strains isolated from HIV positive patients with oropharyngeal candidiasis (OPC).

MATERIALS AND METHODS

The essential oils were obtained by hydrodistillation method from Myrtus communis (My. communis), Zingiber officinale roscoe (Z. officinale roscoe), Matricaria chamomilla (Ma. chamomilla), Trachyspermum ammi (T. ammi) and Origanum vulgare (O. vulgare). The susceptibility test was based on the M27-A2 methodology. The chemical compositions of the essential oils were obtained by gas chromatography- mass spectroscopy (GC-MS).

RESULTS

In GC-MS analysis, thymol (63.40%), linalool (42%), α-pinene (27.87%), α-pinene (22.10%), and zingiberene (31.79%) were found to be the major components of T. ammi, O. vulgare, My. communis, Ma. chamomilla and Z. officinale roscoe, respectively. The results showed that essential oils have different levels of antifungal activity. O. vulgare and T. ammi essential oils were found to be the most efficient (P<0.05). The main finding was that the susceptibilities of FLU-resistant C. albicans to essential oils were higher than those of the FLU-susceptible yeasts.

CONCLUSION

Results of this study indicated that the oils from medicinal plants could be used as potential anti FLU-resistant C. albicans agents.

Lactic acid bacteria as functional probiotic isolates for inhibiting the growth of Aspergillus flavus, A. parasiticus, A. niger and Penicillium chrysogenum

OBJECTIVE

The aim of this study was to assess the potential of lactic acid bacteria (LAB) such as Lactobacillus acidophilus, L. rhamnosus, L. casei, L. paracasei and Bifidobacterium bifidum to inhibit the outgrowth of some common food-spoiling fungi including Aspergillus niger, A. flavus, A. parasiticus and Penicillium chrysogenum.

METHODS

Bacterial isolates were cultured on Mann Rogosa Sharpe (MRS) broth and liquid cultures and supernatants were prepared. The antifungal activity was tested using the agar well diffusion method.

RESULTS

Both liquid culture and supernatant of L. casei isolate exhibited high antifungal activity, followed by L. acidophilus and L. paracasei isolates. The least activity was recorded for the isolates B. bifidum, while the isolate L. rhamnosus was moderately active against tested fungi. The antifungal activity of the supernatants obtained from all probiotic isolates against fungi was significantly less than that of liquid cultures (P<0.05). Antifungal activity evaluation showed that A. flavus was the most inhibited fungus by probiotic bacteria, followed by P. chrysogenum, A. niger and A. parasiticus.

CONCLUSION

These results suggest that probiotic bacteria strains have the ability to prevent the growth of pathogenic and mycotoxigenic fungi as antifungal agents for various biomedical applications.

Antifungal effect of Trachyspermum ammi against susceptible and fluconazole-resistant strains of Candida albicans

OBJECTIVE

Trachyspermum ammi (T. ammi) has been known as having many therapeutic properties and its antimicrobial activity has currently received a renewed interest. This study aimed to verify the effectiveness of T. ammi essential oil to inhibit the growth of Candida albicans (C. albicans) strains isolated from HIV(+) patients with oropharyngeal candidiasis (OPC).

MATERIALS AND METHODS

The essential oil was obtained by hydrodistillation in a Clevenger apparatus and analyzed by gas chromatography. Susceptibility tests were expressed as inhibition zone by the disk diffusion method and minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) by the broth microdilution method.

RESULTS

Thymol (63.4%), p-cymene (19%) and γ-terpinen (16.9%) were found as the most abundant constituents. The disk diffusion results revealed that 67% of oral C. albicans isolates were susceptible, 9% susceptible-dose dependent and 24% resistant to fluconazole. In the broth microdilution method, 68% of isolates were susceptible, 5% susceptible-dose dependent and 27% resistant to fluconazole. The increase in concentration led to a significant reduction in yeasts that were growing in exponential phase. In addition, with increasing in T. ammi oil concentration, the time of remaining cells in lag phase was significantly increased.

CONCLUSION

This study showed that all clinical C. albicans isolates were susceptible to T. ammi essential oil, indicating a significant reduction in the yeast growth in exponential phase.

Repetitive sequences based on genotyping of Candida albicans isolates obtained from Iranian patients with human immunodeficiency virus

OBJECTIVES

Candidiasis infection caused by Candida albicans has been known as a major problem in patients with immune disorders. The objective of this study was to genotype the C. albicans isolates obtained from oral cavity of patients with positive human immunodeficiency virus (HIV(+)) with or/and without oropharyngeal candidiasis (OPC).

MATERIALS AND METHODS

A total of 100 C. albicans isolates from Iranian HIV(+)patients were genotyped using specific PCR primers of the 25S rDNA and RPS genes.

RESULTS

The frequencies of genotypes A, B and C which were achieved using 25S rDNA , were 66, 24 and 10 percent, respectively. In addition, genotypes D and E were not found in this study. Each C. albicans genotype was further classified into four subtypes (types 2, 3, 2/3 and 3/4) by PCR amplification targeting RPS sequence.

CONCLUSION

In general, genotype A3 constituted the majority of understudy clinical isolates obtained from oral cavity of Iranian HIV(+) patients.

Antifungal efficacy of thymol, carvacrol, eugenol and menthol as alternative agents to control the growth of food-relevant fungi

OBJECTIVE

This work is an attempt to examine the antifungal activity of thymol, carvacrol, eugenol and menthol against 11 food-decaying fungi.

METHODS

The susceptibility test for the compounds was carried out in terms of minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) using microdilution method in 96 multi-well microtiter plates.

RESULTS

Results indicated that all compounds were effective to varying extents against various fungal isolates, with the highest efficacy displayed by carvacrol (mean MIC value: 154.5 μg/mL) (P<0.05). The incorporation of increased concentrations of all compounds to the media led to progressive and significant reduction in growth for all fungi. The most potent inhibitory activity of thymol, carvacrol, eugenol and menthol was found for Cladosporium spp. (MIC: 100 μg/mL), Aspergillus spp. (MIC: 100 μg/mL), Cladosporium spp. (MIC: 350 μg/mL), and Aspergillus spp. and Cladosporium spp. (MIC: 125 μg/mL), respectively.

CONCLUSION

Thus, the application of these herbal components could be considered as a good alternatives to inhibit fungal growth and to reduce the use of synthetic fungicides.

Ocular fungal flora from healthy horses in Iran

OBJECTIVE

This study was carried out in order to isolate and identify the normal conjunctival fungal flora from Caspian miniature, Thoroughbred, Turkmen and Persian Arab breeds in Tehran, Iran.

MATERIALS AND METHODS

A total of seventy-two adult healthy horses were studied. Ocular samples were collected from right and left eyes by using sterile cotton swabs; samples were cultured on Sabouraud dextrose agar and incubated at 30°C for 7-10 days. Molds and yeasts were identified using macro and micro-morphological and physiological characteristics.

RESULTS AND CONCLUSION

Number of fungal colonies per eye varied between 0 and 123 colony forming units (CFUs). The most predominant fungal isolates were Aspergillus (19.9%), Rhizopus (15.9%) and Penicillium (15.1%). No significant differences were observed between types of eye fungal floras in different breeds. Caspian miniature horses had significantly the highest number of fungal isolates in compare with other breeds (P<0.001), however no significant difference was observed among other breeds under study. The fungal isolates were almost the same as with studies performed in other countries, although differences in species isolated could be related to geographic and climate difference.

Isolation and identification of yeast flora from genital tract in healthy female camels (Camelus dromedarius)

Yeasts are commensal organisms found in the skin, genital and gastrointestinal tracts, and other mucosal sites in mammalians. The purposes of this study were to identify yeast flora and to determine the number of colony forming units (CFUs) in genital tract of healthy female dromedary camels, establishing their connection in both mated and unmated conditions. The samples were taken from different parts of genital tract including vestibule, vagina, cervix, uterine body, and uterine horns of 50 camels using sterilized cotton swabs. They were cultured onto Sabouraud glucose agar containing chloramphenicol and incubated at 30 degrees C for 7-10 days. A total of 454 yeast colonies were obtained from genital tract. Yeast isolates belonged to 8 genera: Candida (73.1%), Trichosporon (10.1%), Geotrichum (7.5%), Kluyveromyces (3.5%), Rhodotorula (2.4%), Aureobasidium (1.4%), Cryptococcus (1.1%) and Prototheca (0.8%). Among different Candida species, C. zeylanoides was the most common isolated species, representing significant difference with other Candida species (P<0.05). The mean number of yeasts found in the vestibule (46%) was significantly higher than the results obtained from other parts (P<0.05). In addition, the mean value of CFUs from unmated females (71.1%) was significantly higher than mated females (P<0.05). The results showed that C. zeylanoides was a common component of healthy camel females' genital mycoflora and the number of yeasts varied between mated and unmated females.