Azole Resistance and Detection of the ERG11 Gene in Clinical Candida albicans Isolated from Pregnant Women with Vulvovaginitis Attending Federal Medical Centre, Yenagoa, Nigeria

Introduction:Candida albicansis one of the most important aetiological agents causing vaginal candidiasis in pregnant women.Most women will experience at least one episode during their reproductive years. Antifungal resistance is a particular problem with Candida infections. Some types of Candida are increasingly resistant to the first-line and second-line antifungal medications.Objective:To investigate the azole susceptibility of Candida albicans(C. albicans) from pregnant vulvovaginal candidiasis patients and to detect ERG11gene in these azole resistance isolates.Methods:Forty-one clinical isolates of C. albicanswere collected. Azole susceptibility was tested in vitrousing microdilution techniques.The ERG11genes of 27 isolates of C. albicans(All resistant to azoles) were amplified using PCR method

Application of PCR-reverse dot blot hybridization in the diagnosis of vulvovaginal candidiasis and the detection of Candida albicans drug-resistant genes / 临床检验杂志

Objective To evaluate the application value of PCR-reverse dot blot hybridization in the identification of Candida and the detection of Candida albicans drug-resistant genes.Methods The vaginal secretion samples from 285 patients with candidal vaginitis and 50 healthy women were collected.The identification of Candida species and their drug susceptibility were detected by the bioMérieux Yeast identification cards and MIC method(Zhengzhou Antu kit),respectively.The identification of Candida species and the mutation of Candida albicans,drug-resistant genes were also detected by the Shenzheng Yaneng test kit(PCR-reverse dot blot hybridization).The drug-resistant genes were also identified by PCR and nucleic acid sequencing.Based on the culture identification,MIC method and nucleic acid sequencing as the contrast methods,the sensitivity,specificity and accuracy of PCR-reverse dot blot hybridization in the identification of Candida species and the mutation detection of Candida albicans drug-resistant genes were evaluated.Results Compared with the bioMérieux Yeast identification method,the sensitivity,specificity,positive predictive value,negative predictive value and total coincidence rate of PCR-reverse dot blot hybridization for detecting six kinds of Candida species,including Candida albicans,Candida glabrata,Candida tropicalis,Candida parapsilosis,Candida krusei and Candida guilliermondii,were above 95％,96％,96％,98％ and 97％,respectively.There was no significant difference in detecting six kinds of Candida species between the two methods (x2 =0.44,0,0,0,0 and 0,respectively,P ＞ 0.05),and there was good consistency between them (Kappa ＞ 0.9).Compared with the MIC method,the sensitivity,specificity,positive predictive value,negative predictive value and total coincidence rate of PCR-reverse dot blot hybridization for detecting the drug resistance of Candida albicans were 98％,88％,98％,88％ and 96％,respectively.There was no significant difference in detecting the drug resistance of Candida albicans between the two methods (x2 =0.17,P ＞ 0.05),and there was good consistency between them (Kappa ＞ 0.8).The results of PCR-reverse dot blot hybridization in detecting the mutation sites of six kinds of Candida albicans drug-resistant genes were 100％ of coincidence with that of the nucleic acid sequencing method.Conclusion The PCR-reverse dot blot hybridization has high consistency with the culture method and the nucleic acid sequencing method in the identification of Candida species and the mutation detection of Candida albicans drug-resistant genes,which is more early and rapid than the traditional detection methods,and may be applied to the auxiliary diagnosis of vulvovaginal candidiasis (VVC).

Expression of the ERG11 gene in fluconazole-resistant Trichosporon asahii / 中华皮肤科杂志

Objective To investigate the role of the ERG11 gene in the drug resistance of Trichosporon asahii (T.asahii), and to explore the relationship between the gene expression and drug concentrations. Methods Stable fluconazole-resistant strains of T.asahii were induced in vitro following exposure to a series of concentrations of fluconazole. Fluconazole-sensitive and-resistant strains of T.asahii were separately cultured in the medium containing fluconazole at concentrations of 0, 0.25, 0.5, 1, 2, 4, 8, 16, 32 and 64 μg/ml. Real-time quantitative PCR was performed to determine the mRNA expression of ERG11 gene. Results In fluconazole-free medium, the fluconazole-resistant strain of T.asahii showed significantly increased mRNA expression of the ERG11 gene compared with the fluconazole-sensitive strain (7.542 ± 5.311 vs. 1.014 ± 0.012, t=3.002, P=0.03). Additionally, the mRNA expression of ERG11 gene was also significantly higher in the fluconazole-resistant strains than the fluconazole-sensitive strains in the culture medium containing fluconazole at different concentrations of 0.25 (9.183 ± 3.226 vs. 3.281 ± 2.068), 0.5(13.657 ± 5.428 vs. 3.459 ± 1.923), 1(15.292 ± 7.007 vs. 3.242 ± 2.530), 2(13.720 ± 8.550 vs. 3.651 ± 0.728), 4(13.949 ± 2.960 vs. 3.969 ± 1.924)and 8(13.123 ± 6.429 vs. 3.824 ± 1.875)μg/ml(all P<0.05). However, no significant correlation was observed between the mRNA expression of ERG11 gene and fluconazole concentrations(fluconazole-resistant strains: rs = 0.229, P = 0.096; fluconazole-sensitive strains:rs=0.166, P=0.357). Conclusion Overexpression of ERG11 gene is associated with fluconazole resistance in T.asahii, but there is no correlation between the mRNA expression of ERG11 gene and fluconazole concentrations.

ERG11 mutations associated with azole resistance in Candida albicans isolates from vulvovaginal candidosis patients

Objective: To investigate the azole susceptibility of Candida albicans ( C. albicans) from vulvovaginal candidosis patients and to analyze the relationship between ERG11 gene mutations in these isolates and azole resistance. Methods: Three hundred and two clinical isolates of Candida species were collected. Azole susceptibility was tested in vitro in microdilution studies. The ERG11 genes of 17 isolates of C. albicans (2 susceptibles, 5 dose-dependent resistants and 10 resistants) were amplified and sequenced. Results: Of the 302 isolates collected, 70.2% were C. albicans, of which 8.5%, 3.8% and 4.2% were resistant to fluconazole, itraconazole and voriconazole, respectively. In total, 27 missense mutations were detected in ERG11 genes from resistant/susceptible dose-dependent isolates. Among them, Y132H, A114S, and Y257H substitutions were most prevalent and were known to cause fluconazole resistance. G464S and F72S also have been proved to cause fluconazole resistance. Two novel substitutions (T285A, S457P) in hotspot regions were identified. Conclusions: Twenty seven mutations in the ERG11 gene were identified in azole-resistant C. albicans isolates, which indicated a possible relation with the increase in resistance to azole drugs and the recurrence of vulvovaginal candidosis. The relationship of two novel substitutions (T285A, S457P) with fluconazole resistance needs to be further verified by site-directed mutagenesis.

ERG11 mutations associated with azole resistance in Candida albicans isolates from vulvovaginal candidosis patients

Objective:To investigate the azole susceptibility of Candida albicans (C. albicans) from vulvovaginal candidosis patients and to analyze the relationship between ERG11 gene mutations in these isolates and azole resistance. Methods:Three hundred and two clinical isolates of Candida species were collected. Azole susceptibility was tested in vitro in microdilution studies. The ERG11 genes of 17 isolates of C. albicans (2 susceptibles, 5 dose-dependent resistants and 10 resistants) were amplified and sequenced. Results:Of the 302 isolates collected, 70.2%were C. albicans, of which 8.5%, 3.8%and 4.2%were resistant to fluconazole, itraconazole and voriconazole, respectively. In total, 27 missense mutations were detected in ERG11 genes from resistant/susceptible dose-dependent isolates. Among them, Y132H, A114S, and Y257H substitutions were most prevalent and were known to cause fluconazole resistance. G464S and F72S also has been proved to cause fluconazole resistance. Two novel substitutions (T285A, S457P) in hotspot regions were identified. Conclusions:Twenty seven mutations in the ERG11 gene were identified in azole-resistant C. albicans isolates, which indicated a possible relation with the increase in resistance to azole drugs and the recurrence of vulvovaginal candidosis. The relationship of two novel substitutions (T285A, S457P) with fluconazole resistance needs to be further verified by site-directed mutagenesis.

Caracterización de los mecanismos de resistencia a azoles en aislados clínicos chilenos de Candida albicans / Characterization of azole resistance mechanisms in Chilean clinical isolates of Candida albicans

Introduction: The commensal yeast Candida albicans, can cause superficial or systemic candidiasis in susceptible hosts. In Chile, azole antifungals are the most widely used drugs in the treatment of candidiasis. In a previous study performed at our center, 2.1 and 1.6% of clinical isolates of C. albicans were found to be resistant to fluconazole and voriconazole, respectively. Objective: To characterize the resistance mechanisms involved in azoles resistance in Chilean clinical isolates. Methodology: Eight resistant, nine susceptible-dose dependent (SDD) and 10 susceptible strains (n: 27) were selected according to the Clinical Laboratory Standards Institute (CLSI) M27-S3 criteria, from vaginal and urine samples. Mutations in the 408-488 region of the ERG11 gene were studied by sequencing, and the relative expression of ERG11 gene and efflux pump genes CDR1, CDR2 and MDR1, was evaluated by quantitative real-time PCR (q-PCR). Results: No mutations were detected in the ERG11 gene and its overexpression was found only in 12.5% of the resistant strains (1/8). The most prevalent mechanism of resistance was the over-expression of efflux pumps (62.5%; 5/8). Conclusion: The study of the expression of efflux pumps by q-PCR could be a useful diagnostic tool for early detection of azole resistance in C. albicans.

Introducción: Candida albicans es una levadura comensal capaz de causar una infección oportunista en hospederos susceptibles denominada candidiasis, que puede ser superficial o sistémica. En Chile, los antifúngicos más utilizados para el tratamiento de las candidiasis son los azoles. En un estudio previo en nuestro centro, se detectó que 2,1 y 1,6% de cepas clínicas de C. albicans fueron resistentes a fluconazol y voriconazol, respectivamente. Objetivo: Caracterizar los mecanismos de resistencia involucrados en la resistencia a azoles en cepas clínicas chilenas. Metodología: Según los criterios del Clinical Laboratory Standards Institute (CLSI) M27-S3, se seleccionaron ocho cepas resistentes, nueve cepas susceptibles dosis dependiente (SDD) y 10 cepas sensibles (n: 27), aisladas de flujo vaginal y orina. Se evaluó la presencia de mutaciones en la región 408-488 del gen ERG11 por secuenciación y la expresión relativa del gen ERG11 y de los genes de bombas de eflujo CDR1, CDR2 y MDR1 por RPC en tiempo real cuantitativa (q-PCR). Resultados: No se encontraron mutaciones en el gen ERG11 y la sobre-expresión de éste sólo se presentó en 12,5% de las cepas resistentes (1/8). El mecanismo prevalente en la cepas resistentes fue la sobre-expresión de bombas de eflujo encontrándose en 62,5% de las cepas resistentes (5/8). Conclusión: El estudio de la expresión bombas de eflujo por q-PCR podría ser una herramienta diagnóstica útil para la detección temprana de resistencia a azoles en C. albicans.

Mechanisms of fluconazole resistance in clinical and experimental induced isolates of Candida glabrata / 中华微生物学和免疫学杂志

Objective To investigate the mechanisms of fluconazole resistance in clinical and experimental induced isolates of C.glabrata.Methods Efflux of rhodamine 6G was performed to evaluate the effects of efflux pumps.The expression levels of transporter genes CDR1,CDR2,SNQ2 and ERG11 were examined by real-time RT-PCR.Meanwhile,sequence of PDR1 was determined by PCR based DNA sequencing.Results Efflux pumps of all fluconazole-resistant isolates had stronger effects than that of susceptible isolates,consistently with significant upregulation of CDR1,but no obvious difference was found in CDR2 or SNQ2.Also,no notable change in the expression level of ERG11 between susceptible and resistant isolates.PDR1 mutations existed in both clinical and experimental induced isolates of C.glabrata,among which P927S,L543P and S947L haven't been reported previously.Conclusion Mutations of PDR1 were induced by fluconazole both in vivo andin vitro,which will result in overexpression of CDR1 and strengthen the effect of efflux pump.

Mutation analysis of ERG 11 gene in Candida albicans isolates from patients with acquired immunodeficiency syndrome (AIDS) / 中华皮肤科杂志

Objective To investigate the relationship between the mutation of ERG11 gene,a target of azole antifungal drugs (fluconazole,itraconazole,voriconazole),and azole-resistance in Candida albicans isolates from patients with AIDS.Methods Ninety-three Candida albicans strains were isolated from patients with AIDS.DNA was extracted from these isolates,and ERG11 gene was amplified by PCR followed by bidirectional sequencing.DNAman software was used to compare the resultant sequence with the reference sequence of ERG11 gene (GenBank accession no.X13296).Then,different base sequences were translated into amino acid sequences to determine whether missense mutations occured.Results A total of 40 mutation sites were identified in these isolates,including 27 silent mutations and 13 missense mutations.One or no missense mutation was detected in Candida albicans strains resistant to 1 antifungal agent,while those resistant to 2 or 3 antifungal agents simultaneously harbored 2 or 3 missense mutations.Conclusion The missense mutations in ERG11 gene are probably connected with azole resistance in Candida albicans.

Analysis of ERG11 gene mutations in fluconazole-resistant Candida glabrata strains / 中华传染病杂志

Objective To study the mutations of ERG11 gene which encodes P450 lanosterol 14-α demethylase, and to explore the possible role of ERG11 gene in inducing fluconazole resistance in Candida glabrata. Methods ERG11 genes of 9 fluconazole-resistant Candida glabrata isolates and 10 fluconazole-sensitive Candida glabrata isolates were cloned into pUC57-T vector. The open reading frame of ERG11 gene were sequenced by two directional sequencing using universal primers. All sequences were compared with the published sequence. Results Ten kinds of synonymous point mutation were found. Neither missense mutation nor frame-shifting mutation was found. Among the 10 kinds of synonymous point mutation, 5 were found in both fluconazole-resistant and fluconazolesensitive Candida glabrata isolates, and 3 were only found in fluconazole-resistant isolates, 2 were only found in fluconazole-sensitive ones. The majority of the point mutations were located between 1320-2200 base pair of ERG11 gene. Conclusions There are ERG11 gene polymorphisms in clinical strains of Candida glabrata. ERG11 gene mutations are not found to be involved in the development of fluconazole resistance in Candida glabrata.

Application of DNA microarray in the identification of Candida spp. and mutations of ERG11 gene resulting in fluconazole resistance / 中华皮肤科杂志

Objective To investigate the performance of DNA microarray in identifying 6 common Candida spp. and validating ERG11 mutations resulting in fluconazolc-resistance in Candida albicans. Methods Oligonucleotide probes were designed and synthesized targeting the species-specific sequence in the internal transcribed spacer 2 (ITS2) region of rDNA of Candida albicans, Candida tropicalis, Candida glabrata, Candida dubliniensis, Candida parapsilosis and Candida krusei, as well as 6 sequences embracing the following mutations respectively in ERG11 gene leading to fluconazole-resistance, i.c., T541C, A 1090G, C1361T, G1537A, G1547A, and T1559C, then arranged onto a chip. Twelve 50-base-pair oligonucleotides were artificially synthesized based on the above specific sequences, and utilized to hybridize with the DNA microarray. Thirty-lbur Candida strains, including 29 C. albicans, 1 Candida tropicalis, 1 Candida glabrata,1 Candida dubliniensis, 1 Candida parapsilosis and 1 Candida krusei, were detected with microarray. Genomic DNA was extracted from these tested strains and underwent multiple PCR for the amplification of ITS2 region and ERGI 1 gene. Sequencing was performed to analyze the sequence of ERG11 in 29 strains of C. albicans and the results were compared with those of DNA microarray hybridization. Results Multiple PCR successfully produced ITS2 fragment of 307-415 bp from all the 34 strains, as well as ERG11 fragment of 1712 bp from 29 C. albicans strains. DNA microarray hybridization offered the same results in species identification of the 34 strains with their given information, as well as in mutation detection of the 29 strains of C. albicans with ERG11 sequencing results. Also, the 6 synthesized oligonucleotides containing the muta- tions were identified precisely as T541C, A1090G, C1361T, G1537A, G1547A, and T1559C, and the 6 species specific oligonucleotieds were identified correctly as C. albicans, C. tropicalis, C. glabrata, C. dubliniensis, C. parapsilosis and C. krusei Both the sensitivity and the specificity of the microarray were 100%. Conclu- sion DNA microarray is a quite reliable method to identify Candida spp. and fluconazole resistance-associ- ated mutations in the ERG11 gene of C. albicans.

Correlation between antifungal susceptibility of clinical isolates of Candida albicans to fluconazole and ERG11 mutations / 中华皮肤科杂志

Objective To analyze the sensitivity of clinical isolates of Candida albicans to flucona- zole,to detect mutations in their ERG11 genes,and to investigate the correlation between ERG11 gene mutation and resistance to fluconazole.Methods Candida albicans was identified from clinical isolates of Candida spp..The sensitivity to fluconazole was detected in vitro by microdilution-basesd method and Rosco tablets method.Three pairs of primers were designed to amplify three fragments of ERG11 gene(483 bps, from 295 bp to777 bp;482bps,from 723 bp to 1204 bp;489 bps,from 1179 bp to 1667 bp)after the extracting of genomic DNA.PCR products were sequenced.Results Eighty clinical isolates of Candida spp.were collected,which included 52 isolates of Candida albicans,all of which were sensitive to flucona- zole.Nineteen mutations were detected in ERG11 gene of 5 fluconazole-sensitive clinical isolates.Of the 19 mutations,14 were samesense mutations,and the remaing 5 missense mutations(T495A,A530C, G640A,A945C and G1609A),resulting in amino acid substitution D116E,K128T,E165K,E266D and V488I,respectively in lanosterol 14 alpha-demethylase.E165K was a novel mutation.Conclusions The clinical isolates of Candida albicans were highly sensitive to fluconazole;E165K and V488I might not lead to the resistance of Candida albicans to fluconazole.

The point mutation of cytochrome P-450 lanosterol 14-? demethylase ERG11 gene in Fluconazole-resistant Candida albicans / 中华传染病杂志

Objective To investigate the point mutation of the open reading frame of cytochrome P-450 lanosterol 14-? demethylase gene ERG11. Methods In order to identify such alterations, the DNA was extracted by enzyme lysis methods and the PCR was performed. The PCR products were purified and cloned into PBS vector, then transformed into DH5? and sequenced. Results Twenty nine point mutations were identified in this 15 resistant isolates, most of which were different from susceptible strains. The mutations included 12 missense substitutions: F72L, D81G, D116E, K128T, Y132H, E266D, D294G, S361P, M374V, P386L, H400R, and Q474K, of which 6 had not been described previously (D294G, S361P, M374V, P386L, H400R, and Q474K). The other mutations included a frameshift, and 17 silent mutations. Conclusions The point mutation of resistant isolate is different from that of the susceptible isolate. It is suggested that the drug resistance is related with by the newly found alterations, including D294G, S361P, M374V, P386L, H400R, Q474K, and a frameshift.