Expression of genes encoding bacteriocin ST4SA as well as stress proteins by Enterococcus mundtii ST4SA exposed to gastro-intestinal conditions, as recorded by real-time polymerase chain reaction (PCR)

[摘要] ENGLISH ABSTRACT: The tolerance of Enterococcus mundtii ST4SA to stressful gastro-intestinal conditions inhumans and animals is vital to its success as a probiotic. The need for new effectiveprobiotics with stronger inhibitory (bacteriocin) activity has arisen due to the increasingnumber of antibiotic resistant pathogens. Enterococci are used in the fermentation ofsausages and olives, cheese making and as probiotics. Their role as opportunisticpathogens in humans makes them a controversial probiotic (Moreno et al., 2005).Enterococci occur naturally in the gastro-intestinal tract which renders them intrinsic acidand bile resistance characteristics. E. mundtii ST4SA produces a 3950 Da broad-spectrumantibacterial peptide active against Gram-positive and Gram-negative bacteria, andviruses. The bacteria include Enterococcus faecalis, Streptococcus spp., Pseudomonasaeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae and Staphylococcusaureus. E. mundtii ST4SA inactivates the herpes simplex viruses HSV-1 (strain F) andHSV-2 (strain G), a measles virus (strain MV/BRAZIL/001/91, an attenuated strain ofMV), and a polio virus (PV3, strain Sabin).This study focuses on the genetic stability of E. mundtii ST4SA genes when exposed tostress factors in the human and animal gastrointestinal tract. Based on results obtained byreal-time PCR, the expression of genes encoding bacST4SA, RecA, GroES and 23SrRNA by E. mundtii ST4SA were not affected when the cells were exposed to acid, bileand pancreatic juice. This suggests that these genes of E. mundtii ST4SA will remainstable in the intestine. This could indicate that other genes of E. mundtii ST4SA couldremain stable in the host. Further studies on the stability of genes encoding antibioticresistance and virulence factors should be conducted to determine their stability andexpression in the host in stress conditions. Concluded from this study, E. mundtii ST4SAis an excellent probiotic strain.

[发布机构] Stellenbosch University