Mechanisms of resistance to fluconazole in Candida albicans clinical isolates from Iranian HIV-infected patients with oropharyngeal candidiasis

ABSTRACT Candida dubliniensis is a newly identified species of Candida that is phenotypically similar to but genetically distinct from C. albicans. This organism has been recovered with increasing frequency from the oral cavities of human immunodeficiency virus (HIV)-infected and AIDS patients and has been implicated as a causative agent of oral candidiasis and systemic disease. In the present study we characterized the molecular mechanisms of resistance to fluconazole (FLC) in C. dubliniensis clinical isolates from two different HIV-infected patients with oropharyngeal candidiasis. Isolates were identified to the species level by phenotypic and genotypic tests. DNA-typing techniques were used to assess strain identity. Antifungal susceptibility testing was performed by NCCLS techniques. Northern blotting analysis was used to monitor the expression of genes encoding lanosterol demethylase (ERG11) and efflux transporters (CDR and MDR1) in matched sets of C. dubliniensis-susceptible and -resistant isolates by using probes generated from their homologous C. albicans sequences. In addition, ERG11 genes were amplified by PCR, and their nucleotide sequences were determined in order to detect point mutations with a possible effect in the affinity for azoles. Decreasing susceptibilities to FLC were detected in C. dubliniensis isolates recovered from both patients during the course of treatment. FLC-resistant C. dubliniensis isolates from one patient demonstrated combined upregulation of the MDR1, CDR1, and ERG11 genes. Among the isolates from the second patient, all isolates showing decreased susceptibility to FLC demonstrated upregulation of MDR1, whereas the levels of mRNA for the ERG11 genes remained constant and the expression of CDR genes was negligible. Fourteen point mutations were found in the ERG11 genes of the isolates with decreased susceptibility to FLC. These data demonstrate that the development of azole resistance in C. dublinensis clinical isolates from HIV-infected patients treated with FLC is mediated by multiple molecular mechanisms of resistance, similar to the observations found in the case of C. albicans.

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Resistance Mechanisms in Clinical Isolates of Candida albicans

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.46.6.1704-1713.2002 ◽

2002 ◽

Vol 46 (6) ◽

pp. 1704-1713 ◽

Cited By ~ 299

Author(s):

Theodore C. White ◽

Scott Holleman ◽

Francis Dy ◽

Laurence F. Mirels ◽

David A. Stevens

Keyword(s):

Candida Albicans ◽

Molecular Mechanisms ◽

Efflux Pump ◽

Point Mutations ◽

Resistance Mechanisms ◽

Northern Blotting ◽

Clinical Isolates ◽

Cross Resistance ◽

Polymorphism Analysis ◽

Mechanisms Of Resistance

ABSTRACT Resistance to azole antifungals continues to be a significant problem in the common fungal pathogen Candida albicans. Many of the molecular mechanisms of resistance have been defined with matched sets of susceptible and resistant clinical isolates from the same strain. Mechanisms that have been identified include alterations in the gene encoding the target enzyme ERG11 or overexpression of efflux pump genes including CDR1, CDR2, and MDR1. In the present study, a collection of unmatched clinical isolates of C. albicans was analyzed for the known molecular mechanisms of resistance by standard methods. The collection was assembled so that approximately half of the isolates were resistant to azole drugs. Extensive cross-resistance was observed for fluconazole, clotrimazole, itraconazole, and ketoconazole. Northern blotting analyses indicated that overexpression of CDR1 and CDR2 correlates with resistance, suggesting that the two genes may be coregulated. MDR1 overexpression was observed infrequently in some resistant isolates. Overexpression of FLU1, an efflux pump gene related to MDR1, did not correlate with resistance, nor did overexpression of ERG11. Limited analysis of the ERG11 gene sequence identified several point mutations in resistant isolates; these mutations have been described previously. Two of the most common point mutations in ERG11 associated with resistance, D116E and E266D, were tested by restriction fragment length polymorphism analysis of the isolates from this collection. The results indicated that the two mutations occur frequently in different isolates of C. albicans and are not reliably associated with resistance. These analyses emphasize the diversity of mechanisms that result in a phenotype of azole resistance. They suggest that the resistance mechanisms identified in matched sets of susceptible and resistant isolates are not sufficient to explain resistance in a collection of unmatched clinical isolates and that additional mechanisms have yet to be discovered.

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Faculty Opinions recommendation of Candida glabrata Binding to Candida albicans Hyphae Enables Its Development in Oropharyngeal Candidiasis.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.726253922.793516291 ◽

2016 ◽

Author(s):

Neil Andrew Robert Gow ◽

Bhawna Yadav

Keyword(s):

Candida Albicans ◽

Candida Glabrata ◽

Oropharyngeal Candidiasis

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The role of yeasts other than Candida albicans in oropharyngeal candidiasis

Current Opinion in Infectious Diseases ◽

10.1097/00001432-200112000-00002 ◽

2001 ◽

Vol 14 (6) ◽

pp. 673-677 ◽

Cited By ~ 34

Author(s):

Spencer W. Redding

Keyword(s):

Candida Albicans ◽

Oropharyngeal Candidiasis

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Patterns of Fluconazole Susceptibility in Isolates from Human Immunodeficiency Virus-Infected Patients with Oropharyngeal Candidiasis Due to Candida albicans

Clinical Infectious Diseases ◽

10.1093/clinids/24.2.124 ◽

1997 ◽

Vol 24 (2) ◽

pp. 124-130 ◽

Cited By ~ 35

Author(s):

F. Laguna ◽

J. L. Rodriguez-Tudela ◽

J. V. Martinez-Suarez ◽

R. Polo ◽

E. Valencia ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Candida Albicans ◽

Oropharyngeal Candidiasis ◽

Immunodeficiency Virus

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Pathogenicity of Candida tropicalis and Candida albicans after gastrointestinal inoculation in mice

Infection and Immunity ◽

10.1128/iai.29.2.808-813.1980 ◽

1980 ◽

Vol 29 (2) ◽

pp. 808-813 ◽

Cited By ~ 1

Author(s):

J R Wingard ◽

J D Dick ◽

W G Merz ◽

G R Sandford ◽

R Saral ◽

...

Keyword(s):

Candida Albicans ◽

Mouse Model ◽

Lung Tissue ◽

Candida Tropicalis ◽

Cytotoxic Drugs ◽

Clinical Isolates ◽

Yeast Cells ◽

Gastrointestinal Mucosa ◽

Compromised Host ◽

Adult Mice

The ability of clinical isolates of Candida albicans and candida tropicalis to invade through normal and damaged gastrointestinal mucosa was determined. Adult mice were treated with either gentamicin or gentamicin and cytarabine. Suspensions of yeast cells (10(7)) were administered through a catheter intraesophageally. Invasion was determined by culturing liver, kidney, and lung tissue from mice sacrificed after 48 h. C. albicans and C. tropicalis were incapable of invading through normal gastrointestinal mucosa in mice treated only with gentamicin. Two isolates of C. tropicalis penetrated the damaged gastrointestinal mucosa in 69% (49 of 71) of mice treated with gentamicin and cytarabine. In contrast, three isolates of C. albicans penetrated he damaged gastrointestinal mucosa in only 23% (14 of 62) of mice. These results suggest that C. tropicalis is more capable of invading through damaged gastrointestinal mucosa than C. albicans. The observations in this mouse model parallel those seen in patients on cytotoxic drugs. Therefore, this model offers a tool for investigation of the pathogenicity of these organisms in a model analogous to the compromised host.

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Comparison of 3 Alcohol Gels and 70% Ethyl Alcohol for Hand Hygiene

Infection Control and Hospital Epidemiology ◽

10.1086/591092 ◽

2008 ◽

Vol 29 (10) ◽

pp. 960-962 ◽

Cited By ~ 6

Author(s):

Mirian Nicéa Zarpellon ◽

Vanessa Sarto Soares ◽

Natal Rodrigo Albrecht ◽

Douglas Ricardo da Silva Bergamasco ◽

Lourdes Botelho Garcia ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Candida Albicans ◽

Hand Hygiene ◽

Serratia Marcescens ◽

Ethyl Alcohol ◽

Laboratory Study ◽

Clinical Isolates ◽

Methicillin Resistant ◽

Human Volunteers

In a laboratory study, we demonstrated that 3 alcohol-based hand gels, commercially available in Brazil, were as effective as the traditional 70% ethyl alcohol (by weight) in removing clinical isolates of methicillin-resistant Staphylococcus aureus, Serratia marcescens, and Candida albicans from heavily contaminated hands of human volunteers.

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Detection of erythromycin-resistant determinants by PCR.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.40.11.2562 ◽

1996 ◽

Vol 40 (11) ◽

pp. 2562-2566 ◽

Cited By ~ 632

Author(s):

J Sutcliffe ◽

T Grebe ◽

A Tait-Kamradt ◽

L Wondrack

Keyword(s):

Direct Sequencing ◽

Pcr Primers ◽

Efflux Pumps ◽

Clinical Isolates ◽

Gene Products ◽

Mechanisms Of Resistance ◽

Erythromycin Resistance ◽

Surveillance Studies ◽

Resistance Determinants ◽

Pcr Products

Erythromycin resistance determinants include Erm methylases, efflux pumps, and inactivating enzymes. To distinguish the different mechanisms of resistance in clinical isolates, PCR primers were designed so that amplification of the partial gene products could be detected in multiplex PCRs. This methodology enables the direct sequencing of amplified PCR products that can be used to compare resistance determinants in clinical strains. Further, this methodology could be useful in surveillance studies of erythromycin-resistant determinants.

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