Folia Microbiol. 55 (1), 61–67 (2010) http://www.biomed.cas.cz/mbu/folia/ Efficacy of Rhodotorula glutinis and Spirulina platensis Carotenoids in Immunopotentiation of Mice Infected with Candida albicans SC5314 and Pseudomonas aeruginosa 35 M.M. EL-SHEEKH, Y.A.-G. MAHMOUD, A.M. ABO-SHADY, W. HAMZA Botany Department, Faculty of Science, Tanta University, Tanta 31527, Egypt fax +20 40 3350804 e-mail mostafaelsheekh@yahoo.com Received 22 January 2009 Revised version 26 May 2009 ABSTRACT. Enhancement of the immune response leading to protection against bacterial and fungal infections was shown using different schedules of immunization with microbial pigments and a polysaccha- ride. The group of mice given carotenoids of Rhodotorula glutinis (preparation I) and polysaccharide of Spitulina platensis (IV) survived for 2 weeks after Pseudomonas aeruginosa infection. The groups of mice given carotenoids (I), polysaccharide (IV), I+IV and with the crude phycocyanin of S. platensis (III)+IV sur- vived for 2 weeks after Candida albicans infection. All other groups recorded a maximum level of mortality reaching 2 mice per group either after immunization or post-infection. Adding the carotenoids, phycocyanin and polysaccharides to food as additives might therefore enhance the human immune response against micro- bial infections. Abbreviations BCG-CWS cell wall component from Bacillus tuberculosis IFN interferon CFU colony forming unit IL interleukin HWE hot water extract PBS phosphate-buffered saline C.a. Candida albicans P.a. Pseudomonas aeruginosa R.g. Rhodotorula glutinis S.p. Spirulina platensis Attention is now being focused on the natural production of carotenoids by microbial technology using cyanobacteria and/or yeasts, because these organisms can produce the whole group of physiologically significant carotenoids (e.g., lutein, lycopene, -carotene, astaxanthin). Carotenoids extracted from different sources have been used as a food supplement. R.g. is an asporogenous, non-fermenting yeast with carotenoid pigment, and is glistening, mucoid, deep coral to salmon pink in color on most mycological media (Takaichi et al. 2005; Liang et al. 2006). S.p. (Arthrospira platensis) is a microscopic and filamentous Cyanobacterium that has a long his- tory of use as food. Early interest in S.p. focused mainly on its rich content of protein, vitamins, essential amino acids, minerals, and essential fatty acids. S.p. is 60–70 % protein by mass and contains a rich source of vita- mins, especially vitamin B 12 and provitamin A (-carotene), and minerals, especially iron. One of the few sources of dietary -linolenic acid, it also contains a host of other phytochemicals that have potential health benefits (Qiang et al. 1997). Belay et al. (1993) reviewed the potential health benefits of S.p., presented the limited published information on this Cyanobacterium and called the attention of researchers to the particular areas of immune enhancement and cancer. For a detailed study of immunomodulatory properties of dietary S.p. in mice see Hayashi et al. (1994). According to authors’ findings, (1) mice fed S.p. showed increased numbers of splenic antibody-producing cells in the primary immune response to sheep red blood cells, (2) the percentage of phagocytic cells in peri- toneal macrophages from mice fed a S.p. diet was significantly increased, (3) the proliferation of spleen cells by either concavalin A or phytohemagglutinin was significantly increased, (4) addition of HWE of S.p. to an in vitro culture of spleen cells significantly increased proliferation of these cells with no effect on thymus cells, (5) HWE also significantly enhanced interleukin-1 (IL-1) production from peritoneal macrophages, and (6) addition of the HWE to in vitro spleen culture and the supernatant of macrophages resulted in enhance-