Methicillin-resistant Staphylococcus aureus (MRSA) is recognized as one of the serious pathogen that causes acquired infections worldwide. Its emerging need to discover novel, safe and potent anti-MRSA drugs. In this study, primary screening by anti-MRSA activity assay found one strain WA5-2-37 isolated from the intestinal tract of Periplaneta americana, exhibited great activity against MRSA ATCC 43300. The strain WA5-2-37 produced actinomycin X₂ and collismycin A which showed strong inhibition of MRSA with minimum inhibitory concentration (MIC) values of 0.25 and 8 μg/mL. The structures of the pure compounds were elucidated by analysis of mass spectrometry (MS), ¹H and ¹³C nuclear magnetic resonance (NMR). The strain WA5-2-37 was considered as Streptomyces globisporus on the basis of morphological characteristics, genotypic data, and phylogenetic analysis. This is the first reported naturally occurring strain of S. globisporus isolated from the intestinal tract of P. americana, whereas it has almost been found from plants, marine, and soil previously. Moreover, S. globisporus has not been reported to produce any anti-MRSA substances previously, such as actinomycin X₂ and collismycin A. In conclusion, the insect-derived strain of S. globisporus WA5-2-37 was considered of great potential as a new strain of producing actinomycin X₂, collismycin A or other anti-MRSA compounds.

Gordonia sp. are members of the actinomycete family, their contribution to the environment improvement and environmental protection by their biological degradation ability, but there are few studies on the antimicrobial activity of their secondary metabolites. Our team isolated and purified an actinomycete WA 4-31 from the intestinal tract of Periplaneta americana, firstly identified the strain WA 4-31 by the morphological characteristics and the phylogenetic analyses, and found it was completely homologous to the strain of Gordonia terrae from the Indian desert. Meanwhile, actinomycin D (1), actinomycin X2 (2), mojavensin A (3) and cyclic (leucine-leucne) dipeptide (4) were obtained from the EtOAc extract from the broth of WA 4-31. Compounds 1–4 showed anti-fungus activities against Candida albicans, Aspergillus niger, A. fumigatus and Trichophyton rubrum, also anti-MRSA and inhibited Escherichia coli in different degree. Interestingly, we found when 3 was mixed with 4 with ratio of 1:1, the activity of the mixture on anti-Candida albicans was better than the single. Besides, compounds 1–3 had varying degrees of antiproliferative activities on CNE-2 and HepG-2 cell lines. These indicated that Gordonia rare actinomycete from the intestinal tract of Periplaneta americana possessed a potential as a source of active secondary metabolites.