*Coker, M. O., Thomas, B. T., Efuntoye, M. O., and Popoola, O. D.
Department of Microbiology, Olabisi Onabanjo University, Ago-Iwoye, Ogun State, Nigeria.
*Correspondence to: olawunmimercy707@gmail.com; Mobile: +2349054006625;
ORCID ID: https://orcid.org/0000–0003–0937–7755
Abstract:
Background: Cryptococcus species, including C. neoformans and C. gattii, are environmental yeasts of clinical importance and major agents of cryptococcosis. Environmental reservoir represents the primary source of human and animal infections therefore, characterization of genetic diversity is essential for epidemiological surveillance and understanding the pool of genotypes from which pathogenic strains may arise.
Methodology: This study evaluated the genetic diversity of 18 environmental Cryptococcus isolates recovered from soil samples using random amplified polymorphic DNA (RAPD) analysis. Seven primer combinations (three 20–22 mer and four 12-mer) were employed to generate reproducible banding patterns, and genetic diversity indices were calculated based on RAPD polymorphic loci.
Results: A total of 214 bands, ranging from 330-3800 bp, were amplified from 17 isolates with 10-13 polymorphic bands per isolate; one isolate failed to amplify with all primers and was excluded from further analysis. The isolates were resolved into five haplotypes (A-E), with haplotype B being most prevalent (61.1%). Primer-specific bands enabled diagnostic differentiation of certain haplotypes, demonstrating the discriminating capacity of the selected RAPD primers. Diversity indices indicated high genetic variability among the soil isolates, with a Shannon–Wiener index (Hʹ) of 2.83, Simpson’s index of diversity (1-D) of 0.941, and evenness (E) of 0.999.
Conclusion: These results demonstrate substantial genetic heterogeneity among environmental Cryptococcus isolates, even within a restricted locale. Although no direct comparisons were made with clinical or animal isolates, the observed diversity highlights the complexity of environmental reservoirs that serve as potential sources of infection. This study underscores the utility of RAPD markers for preliminary molecular characterization and epidemiological studies, providing baseline data relevant to environmental and public health surveillance in Nigeria.
Keywords: Cryptococcus Species, Genetic Diversity, RAPD, Polymorphic bands
Download this Article in PDF format below