A novel bioengineered derivative of nisin displays enhanced antimicrobial activity against clinical Streptococcus agalactiae isolates.

BACKGROUND: Streptococcus agalactiae (S. agalactiae) is the leading cause of neonatal disease worldwide and infections caused by this opportunistic pathogen are becoming increasingly more prevalent in adults. With the global incidence of antibiotic resistance continuing to rise, there is a recognised need for new therapeutic agents. Nisin is a potent antimicrobial peptide that has demonstrated broad spectrum activity against a range of clinically significant pathogens.

OBJECTIVES: This study aimed to examine the efficacy of nisin against a clinical population of S. agalactiae strains and further investigate the bioactivity of a novel bioengineered derivative of the peptide, designated nisin PV.

METHODS: A deferred antagonism assay was used to assess the bioactivity of wild type nisin and nisin PV against S. agalactiae strains (n = 122). MICs were evaluated to determine the specific activity of both peptides. The genetic basis of nisin resistance among the collection of strains was investigated by PCR detection of the nsr gene.

RESULTS: In total 91% of the collection showed some level of susceptibility to nisin while 9% displayed complete resistance. Interestingly, the nisin derivative exhibited enhanced antimicrobial activity for 64.8% of isolates. The frequency of the nsr gene, which confers nisin resistance, was also investigated and the gene was detected in 98.4% of isolates suggesting that resistance may be linked to levels of expression of the protein or other regulatory elements.

CONCLUSION: This study indicates that there is potential for use of nisin and its derivatives as therapeutic agents against S. agalactiae infections.