Candida albicans identification and microsatellite DNA genotyping of Lebanese clinical isolates. (c2007)

Abstract

Candida albicans is an opportunistic fungal pathogen. Hospital identification test for C. a!bica1ls vary but the germ tube test, followed by the CHROMagar, and possibly the Biolog tests are the main tests utilized for correct identification. These techniques are subjective and none of them have a 100% identification accuracy. Recently a molecular test based on C. albicans-specific microsatellite DNA genotyping was introduced which eliminates all subjectivity in identification. The present study involves collecting 125 isolates labeled as C. albicans from 5 different Lebanese hospitals and utilizing the microsatellite genotyping test to determine the following: First, the accuracy of hospital identification by comparing micro satellite results to the results of the above mentioned tests. Second the number and genotype of infectious strains present relative to tissue and hospital location- a possible indicator of nosocomial infection, and third a possible relationship between lack of microsatellite heterozygosity and drug resistance. Our results showed that the most accurate identification test was the germ tube test (94.8% sensitivity), followed by the CHROMagar test (88.8% sensitivity, and where some CHROMagar negative Candida albicans strains were observed) and lastly the Biolog (53.4% sensitivity). The error in identification varied from 2-33% amongst hospitals with hospitals combining the germ tube test to any other non-molecular identification test having the best results. Furthermore the highest identification error was found in sputum and stool. These tissues also contained isolates with similar genotypes regardless of hospital origin suggesting that they could be a reservoir for potentially pathogenic strains. Moreover, strains with similar genotypes were found to occur in relatively high frequency within certain hospitals suggesting a possible nosocomial infection rate. Finally, a relationship between lack of heterozygosity and azole drug resistance was observed since 8 out of 9 homozygous isolates sharing a common allele with a heterozygote strain were sensitive to at least one drug. In conclusion, Lebanese hospital should eventually incorporate molecular data in their identification techniques as that would decrease the number of false identifications and improve the well-being of patients suffering from fungal infections.