Distinctive antagonistic role of new Enterococcus faecium ER-3M strain and its bacteriocin effect against Staphylococcus aureus Pneumonia

Bacteriocins secreted by some bacteria such as Enterococcaceae has a protected role against Staph. aureus pneumonia. This study identified a new Enterococcus sp. that produces efficient bacteriocin which attenuates Staph. aureus pneumonia in rats. Identification of Enterococcus sp. was achieved according to Bergey’s manual of systematic bacteriology using 16S rRNA analysis. Bacteriocin was extracted, partially purified and characterized. Antagonistic activity of the bacterial cells or its bacteriocin was estimated in vitro against different pathogenic bacteria and in vivo with an animal experiment, where histopathological and hematological examinations were evaluated. The isolate was identified as Ent. faecium ER-3M, with accession number KY774316. It exhibits broad antimicrobial spectrum against Gram-positive and Gram-negative organisms in vitro. Treatment of rats with bacterial cells or bacteriocin (500 Au mg−1), previously infected with Staph. aureus, significantly decreased the symptoms, WBCs, neutrophils, and liver functions. Histopathological examination of rat lung tissues revealed that treatment with probiotic bacteria and/or its bacteriocin can attenuate the pneumonic lesions caused by Staph. aureus bacteria. Partially purified bacteriocin was characterized by a large molecular weight of approximately 40 kDa a proteinous nature according to both Fourier transform infrared spectrometry (FTIR) spectroscopy and 1H-Nuclear magnetic resonance (NMR) analysis and belongs to class III of bacteriocins termed enterolysin. Based on the results, the successful treatment of Ent. faecium ER-3M or its bacteriocin may be one of the promising treatments against Staph. aureus pneumonia.