Abstract
Aspergillus fumigatus causes severe problems in poultry production systems. Seven South African tree species were selected from the database of the Phytomedicine Programme based on its antifungal activity against the fungus Cryptococcus neoformans. The acetone leaf extracts of the selected species had minimum inhibitory concentrations (MICs) of 0.16 mg/ml and lower in the preliminary screening. The antibacterial and antifungal activities of hexane, dichloromethane, acetone and methanol extracts of the leaves were determined using a two-fold serial microdilution method against a range of commonly encountered animal pathogenic fungi ( A. fumigatus, Candida albicans, C. neoformans, Microsporum canis and Sporothrix schenckii) and four nosocomial bacteria ( Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa). The plant species investigated were Combretum vendae (A.E. van Wyk) (Combretaceae), Commiphora harveyi (Engl.) Engl. (Burseraceae), Khaya anthotheca (Welm.) C.DC (Meliaceae), Kirkia wilmsii Engl. (Kirkiaceae), Loxostylis alata A. Spreng. ex Rchb. (Anacardiaceae), Ochna natalitia (Meisn.) Walp. (Ochnaceae) and Protorhus longifolia (Bernh.) Engl. (Anacardiaceae). All the extracts had activity against at least one of the test organisms over an incubation period of 24 or 48 h. The MIC values of the non-polar and intermediate polarity extracts of O. natalitia, K. anthotheca, C. vendae, C. harveyi, and P. longifolia had MICs as low as 0.08 mg/ml against at least one of the tested bacteria. Furthermore, the acetone extracts of L. alata, K. wilmsii, O. natalitia and C. vendae had antifungal activities with MIC values ranging from 0.04 to 0.08 mg/ml against at least one of the tested fungi. The average MIC values of the plant extracts against the different bacteria ranged from 0.17 to 2.11 mg/ml, while the range was 0.23–1.98 mg/ml for fungi. The Gram-positive bacteria ( S. aureus and E. faecalis) were more susceptible to the plant extracts than the Gram-negative bacteria ( E. coli and P. aeruginosa). E. faecalis was the most susceptible microbe and C. vendae extracts were the most active against nearly all the bacteria tested. The acetone extract of L. alata was the most active against fungal pathogens, with activity against at least 3 fungal organisms. L. alata was selected for further work to isolate compounds active against A. fumigatus and other fungal pathogens.
Highlights
With the development of relatively effective and safe antibiotics in the 1940's, medical treatment had been revolutionalised leading to a drastic drop in morbidity and mortality previously induced by microbial diseases (Rang et al, 2003)
In addition to the pathogenic bacteria, opportunistic fungal infections are becoming more important especially due to the immune deficiency induced by HIV-AIDS (Groll et al, 1996)
Invasive pulmonary aspergillosis (IPA) is a serious fungal infection of immunocompromised patients usually caused by Aspergillus fumigatus with ever increasing incidence (Stevens, 1990; Denning, 1998)
Summary
With the development of relatively effective and safe antibiotics in the 1940's, medical treatment had been revolutionalised leading to a drastic drop in morbidity and mortality previously induced by microbial diseases (Rang et al, 2003). This development was rapidly hampered by the emergence of drugresistance microbes (Walsh, 2000). This resistance has resulted in an increased incidence of infectious diseases with some pathogens (Kunin, 1993; Archibald et al, 1997; Sahm et al, 1999). There are only a limited number of Please cite this article as: Suleiman, M.M., et al, Evaluation of several tree species for activity against the animal fungal pathogen Aspergillus fumigatus, South African Journal of Botany (2009), doi:10.1016/j.sajb.2009.07.001
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