IntroductIonMicroorganisms have caused epidemic, endemic diseases, and deaths of hundreds of millions of humans as well as animal morbidity and mortality worldwide. Microorganisms have developed sophisticated defense mechanisms for their survival in the host cells and to overcome the host defense system such as cells of the immune system, lysozyme attack, cytokinines, complements, antibodies, and phagocytosis. [1] Bacterial infection process attachment and penetration to epithelial cells, multiplication, synthesis of toxins and enzymes, and finally damages the whole cell. [2] The Staphylococcus aureus is a most pathogenic organism of the genus Staphylococcus, and it causes community-acquired and nosocomial infections worldwide. [3] The S. aureus is found in the digestive tracts, livestock, human skin and causes ophthalmic infections with skin infections and sepsis. [4] It is reported that S. aureus causes more fatalities in the USA than AIDS because of antibiotic resistance. [5] The skin and soft-tissue infections are caused by methicillin-resistant S. aureus (MRSA) strain known as USA300. [6] The presence of MRSA has also been established in cats, horses, and rabbits by researchers. [7] Bacillus subtilis damages mammalian membrane by producing lecithinase enzyme. In humans, B. subtilis causes allergic reactions and food poisoning by the production of extracellular toxins. [8] This bacterium causes endocarditis in infants, bacteremia in the patients with the impaired immune system. [9] In hospitals, causes wound infection in hospitalized patients due to the spores production. [9] B. subtilis also contaminates laboratory media. [8] The Salmonella species are Gram-negative bacteria that cause typhoid fever and enterocolitis, intestinal or diarrheal disease Background: Chaetomium cupreum is soil-isolated pigment-producing fungus used as biocontrol agent. Hypothesis: The aim of the present study was to evaluate the bioactive constituents and antibacterial potential of C. cupreum extracts on bacteria such as Staphylococcus aureus, Bacillus subtilis, Salmonella typhi, and Proteus vulgaris. Materials and Methods: The qualitative and quantitative screening of secondary metabolites was done by standard procedures. The antibacterial activity of different extracts of C. cupreum was determined by agar well diffusion method and broth microdilution methods. Results: Among the different extracts of C. cupreum, ethyl acetate and n-butanol extracts exhibited antibacterial activity. In the n-butanol extract, the most susceptible organism was found to be B. subtilis with zone of inhibition 18.5 ± 0.7 mm, followed by P. vulgaris 15.5 ± 0.7 mm, S. typhi 12.5 ± 3.5 mm, and S. aureus 12.0 ± 2.8 mm at 0.5 mg/ml, whereas in the ethyl acetate extract, the most susceptible organism was to found be P. vulgaris with zone of inhibition 17.5 ± 0.7 mm followed by B. subtilis 17.0 ± 1.4 mm, S. typhi 14.0 ± 0.7 mm, and S. aureus 13.5 ± 0.7 mm at 0.5 mg/ml. Conclusion: The obtained results suggest that C. cupreum extracts contain compounds that po...
