Abstract
Candida krusei (C. krusei) has been recently recognized as an important pathogen involved in mycotic mastitis of cows. The phenotypic and molecular characteristics of 15 C. krusei clinical isolates collected from cows with clinical mastitis in three herds of Yinchuan, Ningxia, were identified by matrix-assisted laser desorption ionization–time of flight mass spectrometry. In addition to sequencing analysis, the ERG11 gene that encodes 14α-demethylases, the expression of the ERG11 gene, and efflux transporters ABC1 and ABC2 in itraconazole-susceptible (S), itraconazole-susceptible dose dependent (SDD), and itraconazole-resistant (R) C. krusei isolates was also quantified by a quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) assay. Sequencing analysis revealed three synonymous codon substitutions of the ERG11 gene including T939C, A756T, and T642C in these C. krusei clinical isolates. Among them, T642C and T939C mutations were detected in itraconazole-resistant and -susceptible C. krusei isolates, but the A756T substitution was found only in itraconazole-resistant isolates. Importantly, the expression of the ERG11 gene in itraconazole-resistant isolates was significantly higher compared with itraconazole-SDD and itraconazole-susceptible isolates (p = 0.052 and p = 0.012, respectively), as determined by the qRT-PCR assay. Interestingly, the expression of the ABC2 gene was also significantly higher in itraconazole-resistant isolates relative to the itraconazole-SDD and itraconazole-susceptible strains. Notably, the expression of ERG11 was positively associated with resistance to itraconazole (p = 0.4177 in SDD compared with S, p = 0.0107 in SDD with R, and p = 0.0035 in S with R, respectively). These data demonstrated that mutations of the ERG11 gene were involved in drug resistance in C. krusei. The A756T synonymous codon substitution of the ERG11 gene was correlated with an increased expression of drug-resistant genes including ERG11 and ABC2 in itraconazole-resistant C. krusei isolates examined in this study.
Highlights
Cow mastitis has a major negative impact on dairy industries, causing significant economic losses to farmers
We evaluated the profile of the susceptibility of C. krusei to itraconazole and investigated the potential alterations of the ERG11 gene and the differential expression of ERG11, ABC1, and ABC2 genes of 15 clinical C. krusei isolates that were isolated from cow mastitis in Yinchuan, Ningxia, China
Drug sensitivity testing was performed according to the broth microdilution method M27-A2 (NCCLS 2002), and the result showed that among 15 C. krusei isolates, 73.4, 73.4, and 66.7% were resistant to fluconazole (FLC), ketoconazole (KET), and 5-flucytosine (5FC), respectively
Summary
Cow mastitis has a major negative impact on dairy industries, causing significant economic losses to farmers. In cases of fungal infection of the mammary gland, yeasts of Candida genus are the most reported fungal pathogens in cow mastitis [2]. (NAC), such as C. krusei, C. parapsilosis, C. glabrata, and C. tropicalis, have increased significantly during the last decade [4] Among these NACs, C. krusei ranked as the fifth most common cause of cow mycotic mastitis [5, 6]. Our previous investigation suggested that C. krusei was one of the most important pathogens in mycotic mastitis in dairy farms of the Yinchuan region in Ningxia, China. This result was in accordance with the report of Erbas et al [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
