Screening of Sponge-associated Actinobacteria against Human Pathogenic Candida albicans in Kien Giang Sea, Vietnam
Abstract
From 198 actinomycetes isolated from sponges at the Kien Giang Sea in Vietnam, 42 actinomycete isolates were selected with the ability to resist Candida albicans, a species of yeast causes human diseases. There were eight isolates having strong resistance, 31 moderate, and three weak resistances. Eight best isolates were selected to identify by 16S rDNA gene analysis and sequencing. The result showed that six strains were characterized as Streptomyces spp., one strain belonged to genus Microbacterium, and one strain was genus Rhodococcus.
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Introduction
Candida albicans is an opportunistic pathogenic yeast [1] that is a standard member of the human gut flora. It can also survive outside the human body [2]. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults [3]. It is usually a commensal organism, but it can become human pathogenic in immunocompromised individuals under a variety of conditions [4]. It is one of the few species of the genus Candida that causes the human infection candidiasis, which results from an overgrowth of the fungus [5]. Candidiasis is, for example, often observed in HIV-infected patients [6]. Candidiasis is understood to cause gastrointestinal (GI) symptoms particularly in immunocompromised patients or those receiving steroids (e.g. to treat asthma) or antibiotics. Recently, there is an emerging literature that an overgrowth of fungus within the intestine of non-immunocompromised subjects may cause unexplained GIsymptoms. Candida albicans is a species of yeast-a single-celled fungus, in fact – that lives naturally in the body. This yeast may be a normal part of the microbes that survive your skin and in your alimentary canal, but under some circumstances, it can multiply out of control. Small amounts of Candida albicans also sleep in various warm, moist areas throughout the body, including on the skin, within the mouth and gut, and also the rectum and vagina.
Elbendary [7] using ethyl acetate extraction method, the isolates culture’ssupernatants were tested by diffusion method against indicator microorganisms. These results indicated that actinobacteria isolated from Egypt farms could be sources of antimicrobial bioactive substances.
These identified isolates showed antimicrobial activity against the test organism, and the range of inhibition zones was between 2.5 and 10.2 mm. Out of 287 actinomycetes166 isolates were found antagonistic to Candida albicans isolated and selected a Streptomyces sp. [8]. Al-Dhabi [8] used the chromatogram of GC-MSanalysis of this ethyl acetate extract (EA) had diverse chemical compounds namely benzene acetic acid (7.81%), acetic acid, methoxy-, and 2-phenylethyl ester (6.01%) were the major compounds. Minimum inhibitory concentrations (MIC) values were observed against Candida albicans and Aspergillus niger by (312 μg/ml).
This study aimed to selected and identify the Actinobacteria and discover potential sources of antimicrobial secondary metabolites to human pathogenic yeast, especially Candida albicans.
Conclusion
From 198 isolated actinomycetes, 42 isolates had the ability against Candida albicans, a species of yeast that causes human diseases. The six best isolates were chosen to identify by PCR 16S rRNA technique. They belonged to four Streptomyces, one Microbacterium, and one Rhodococcus. The present study showed that the potential bioactive compound from sponge-associated actinobacteria has not been exploited yet in the Kien Giang Sea, Vietnam. The other invertebrates as coral with endophytes containing many novel secondary metabolites especially, antibiotics, antimicrobial, antifungal, anti-cancer, and so on, need to study in the future.
