The antagonistic effects of Candida parapsilosis on the growth of Fusarium species and fumonisin production

Background and Purpose:

Fusarium species are avid producers of secondary toxic and carcinogenic metabolites such as fumonisin. Contamination of food and feed products with fumonisin can be hazardous to the health of humans and animals and may lead to agricultural loss. Accordingly, in this study, we aimed to evaluate the effects of Candida parapsilosis on the growth and fumonisin production of Fusarium species.

Materials and Methods:

Mycelial growth rate of 26 Fusarium isolates, including F. verticillioides (n=6), F. proliferatum (n=18), F. solani (n=1), and F. oxysporum (n=1), in the presence of 42 C. parapsilosis strains was investigated by pour-plate method. The decline in fumonisin production was measured in co-cultured fungi in coarsely ground maize after four weeks of incubation in the dark at 22°C, using ELISA technique. For data analysis, paired t-test was performed, using SPSS version 20.

Results:

The mycelial growth and fumonisin production of Fusarium isolates significantly decreased in the presence of C. parapsilosis in comparison with the control cultures (P<0.05). The percentage of mycelial growth inhibition ranged from 56.36% to 74.54%. The minimum and maximum decline in total fumonisin production was 12% and 78%, respectively. F. oxysporum and F. solani were found to be minor fumonisin producers among the studied Fusarium species. On the other hand, a decline was reported in the growth of Fusarium species and fumonisin production in the presence of C. parapsilosis.

Conclusion:

C. parapsilosis showed notable inhibitory activities against Fusarium isolates. Therefore, this fungal species could be considered as a biocontrol agent against the growth and fumonisin production of toxigenic Fusarium species in the future.

A survey of the etiological agents of scalp and nail dermatophytosis in Yazd, Iran in 2014-2015

Background and Purpose:

Tinea capitis and tinea unguium are regarded as global public health concerns. The purpose of the present study was to identify the etiological agents of tinea capitis and tinea unguium in patients, referring to the Central Laboratory of Yazd University of Medical Sciences, Yazd, Iran.

Materials and Methods:

This study was conducted during 2014-2015. Skin scraping, scalp hair, and nail clipping specimens were collected from 134 patients (80 males and 54 females) with clinical features suggesting fungal involvement. Direct microscopic examinations were carried out, using potassium hydroxide 10%, while culture studies were performed on Sabouraud dextrose agar, containing chloramphenicol and cycloheximide at 28^°C for four weeks. Fungal colonies were identified based on their macroscopic and microscopic characteristics, as well as supplementary diagnostic tests.

Results:

Among 134 patients, 12 cases showed positive results on direct examination and culture studies. The frequency of infections was equal among male and female subjects. Among 12 affected cases, the frequency of tinea capitis and tinea unguium was 91.6% and 8.4%, respectively. Microsporum canis (50%) was the most prevalent species, followed by Trichophyton verrucosum (25%) and Trichophyton mentagrophytes (25%). Also, tinea unguium, caused by T. mentagrophytes, was found in a female patient.

Conclusion:

The etiological agents of scalp and nail dermatophytosis have changed in Yazd over the past 13 years. In the present study, replacement of anthropophilic dermatophytes by zoophilic species was noteworthy, highlighting the necessity of efficient surveillance for the management and prevention of infections.

A study on etiologic agents and clinical manifestations of dermatophytosis in Yazd, Iran

BACKGROUND AND PURPOSE

Dermatophytosis is one of the most common infections of skin, hair, and nails, caused by a group of keratinophilic fungi known as dermatophytes. Species identification of these fungi is of great significance from epidemiological and therapeutic points of view. The objective of the present study was to investigate dermatophytosis and its causative agents in patients, referring to the Central Mycology Laboratory of Yazd University of Medical Sciences, Yazd, Iran.

MATERIALS AND METHODS

In total, 139 clinically suspected cases of dermatophytosis were examined during 12 months from February 2014 to February 2015. Skin scrapings were assessed through direct microscopic examinations and culture studies. Dermatophyte isolates were identified based on colony morphology on potato dextrose agar and dermatophyte test medium, nutritional requirements, urease and hair perforation tests, and microscopic characteristics on slide cultures.

RESULTS

Dermatophytosis was mycologically confirmed in 26 (18.70%) out of 139 cases. Although there was a statistically insignificant difference between male and female subjects, men were dominantly affected. Infection was significantly common in the age group of ≤ 29 years (P<0.043). The most common clinical manifestation of dermatophytosis was tinea corporis (69.2%), followed by tinea cruris (15.4%), tinea manuum (11.5%), and tinea pedis (3.8%). Trichophyton mentagrophytes complex was the main etiologic agent (38.5%), followed by T. rubrum (23%), T. violaceum (15.5%), T. verrucosum (11.5%), Microsporum canis (7.7%), and Epidermophyton floccosum (3.8%).

CONCLUSION

In comparison with previous research, epidemiology of dermatophytosis has changed in Yazd over the past decades. Therefore, periodical investigations on the epidemiological aspects of this infection are required for efficient control and prevention of this cutaneous dermatophytic disease.

In vitro antifungal activities of Euphorbia macroclada and fluconazole against pathogenic Candida species

BACKGROUND AND PURPOSE

Candida species constitute an important group of opportunistic fungi, which cause various clinical diseases. Considering the resistance of some Candida species to conventional antifungal agents, treatment of such cases may be challenging and complicated. The purpose of this study was to evaluate and compare the antifungal activities of Euphorbia macroclada latex and fluconazole against different Candida species.

MATERIALS AND METHODS

A total of 150 Candida isolates including C. albicans (n=77), C. glabrata (n=28), C. parapsilosis (n=23), C. tropicalis (n=15), C. krusei (n=4), C. famata (n=1), C. kefyr (n=1) and C. inconspicua (n=1) were included in this study. In vitro antifungal activities of Euphorbia macroclada latex and fluconazole against these Candida species were evaluated, according to M27-A2 protocol on broth macrodilution method by the Clinical and Laboratory Standards Institute (CLSI).

RESULTS

Among 150 Candida isolates, 98 isolates (65.33%), i.e., C. albicans (n=41), C. glabrata (n=23), C. tropicalis (n=12) and C. parapsilosis (n=22) with minimal inhibitory concentration (MIC) ≤ 8 μg/ml were susceptible to fluconazole. Resistance to fluconazole was noted in 15 isolates, i.e., C. albicans (n=10), C. glabrata (n=2), C. krusei (n=1), C. kefyr (n=1), and C. inconspicua (n=1), with MICs of 64 µg/ml. The remaining isolates (n=37) including C. albicans (n=26), C. glabrata (n=3), C. tropicalis (n=3), C. parapsilosis (n=1), C. krusei (n=3) and C. famata (n=1) with MIC= 16-32 µg/ml showed dose-dependent susceptibility. The latex of Euphorbia macroclada was able to inhibit the growth of 30 out of 150 tested Candida isolates with MIC range of 128-512 µg/ml. These isolates were as follows: C. albicans (n=2), C. glabrata (n=4), C. parapsilosis (n=19), C. krusei (n=2) and C. tropicalis (n=3). Compared to other isolates, higher MIC values were noted for C. albicans and C. glabrata (512 µg/ml), respectively.

CONCLUSION

The latex of Euphorbia macroclada showed notable antifungal activities against some pathogenic Candida species. Therefore, it can be potentially used as an alternative antifungal agent in future. However, further research is required to identify its active components.

Candida parapsilosis as a Potent Biocontrol Agent against Growth and Aflatoxin Production by Aspergillus Species

BACKGROUND

Aflatoxin contamination of food and feed stuff is a serious health problem and significant economic concerns. In the present study, the inhibitory effect of Candida parapsilosis IP1698 on mycelial growth and aflatoxin production in aflatoxigenic strains of Aspergillus species was investigated.

METHODS

Mycelial growth inhibitions of nine strains of aflatoxigenic and non-aflatoxigenic Aspergillus species in the presence of C. parapsilosis investigated by pour plate technique at different pH, temperature and time of incubation. Reduction of aflatoxin was evaluated in co-cultured fungi in yeast extract sucrose broth after seven days of incubation using HPLC method. The data were analyzed by SPSS 11.5.

RESULTS

The presence of the C. parapsilosis at different pH did not affect significantly the growth rate of Aspergillus isolates. On the other hand, temperature and time of incubation showed to be significantly effective when compared to controls without C. parapsilosis (P≤0.05). In aflatoxigenic strains, minimum percentage of reductions in total aflatoxin and B1, B2, G1, G2 fractions were 92.98, 92.54, 77.48, 54.54 and 72.22 and maximum percentage of reductions were 99.59, not detectable, 94.42, and not detectable in both G1 and G2, respectively.

CONCLUSION

C. parapsilosis might employ as a good biocontrol agent against growth and aflatoxin production by aflatoxigenic Aspergillus species.

Aflatoxin Detoxification in Rice using Citric Acid

BACKGROUND

Aflatoxins cause health hazards to human and animals and has also economical problems. Therefore, the detoxification effect of citric acid was investigated in rice as the main food of Iranian people.

METHODS

Initially 275 samples of rice were examined for aflatoxins by HPLC. The aflatoxins contaminated samples were later treated by aqueous citric acid and detoxification of aflatoxins were quantified using HPLC.

RESULTS

Among the 275 samples analyzed, aflatoxin B(1) and aflatoxin B(2) were detected in 211(76.72% of total) samples. Aflatoxin B(1) was detected in 203(73.82% of total) samples with a mean and standard deviation of 2.3±10.21ppb. Aflatoxin B(2) together with aflatoxin B(1) were detected in only 8(2.91% of total) samples with a mean and standard deviation of 1.38±2.7ppb of aflatoxin B(2) and 2.99±1.56 of aflatoxin B(1) respectively. Aflatoxin B(1) level in 5 samples (1.82%) was above the maximum tolerated level of aflatoxin B(1) in Iran (5ppb). However considering the Iranian maximum tolerated level for aflatoxins in rice (30ppb), only 3(1.09%) samples were above the 30ppb and also in regard to the European maximum tolerated level for aflatoxins in rice (4ppb), only 9(3.27%) samples were considered as higher than 4ppb.

CONCLUSION

The HPLC assay showed that although aflatoxins with a concentration of <30 and <4 ppb in the rice samples were completely degraded, but 97.22% degradation occurred in rice contaminated with ≥30 and ≥4ppb when treated with 1N citric acid. These results revealed the efficacy of 1N citric acid in reducing aflatoxins levels in rice.

Upregulation of the ERG11 gene in Candida krusei by azoles

BACKGROUND AND THE PURPOSE OF THE STUDY

Candida species are the agents of local and systemic opportunistic infections and have become a major cause of morbidity and mortality in the last few decades. Azole resistance in Candida krusei (C. krusei) species appears to be the result of gene alterations in relation to the ergosterol biosynthesis pathway, as well as efflux pumps. The main objective of this study was to examine the RNA expression of ERG11 in C. krusei which had been identified to be resistance to azoles.

METHODS

The ERG11 mRNA expression was investigated in four Iranian clinical isolates of C. krusei, which were resistant to fluconazole and itraconazole by a semiquantitative RT-PCR.

RESULTS

The mRNA expression levels were observed in all four isolates by this technique. Furthermore, it was found that ERG11 expression levels vary among four representative isolates of C. krusei. Although DNA sequencing revealed no significant genetic alteration in the ERG11 gene, one heterozygous polymorphism was observed in two isolates, but not in others. This polymorphism was found in the third base of codon 313 for Thr (ACT>ACC).

MAJOR CONCLUSION

Even though such a polymorphism creates a new Ear1 restriction site, no significant effect was found on the resistance of C. krusei to azoles. RESULTS of this investigation are consistent with previous studies and may provide further evidence for the genetic heterogeneity and complexity of the ergosterol biosynthetic pathway or efflux pumps.