A novel bioengineered derivative of nisin displays enhanced antimicrobial activity against clinical Streptococcus agalactiae isolates
Highlights•Some level of activity was detected for wild type nisin against majority of S. agalactiae strains.•A novel derivative, nisin PV, displayed improved activity against 64.8% of isolates.•A gene encoding the nisin resistance protein was detected in 98.4% of isolates.•There is potential for the use of nisin and its derivatives in the treatment of S. agalactiae infections.Abstract/SummaryBackgroundStreptococcus 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.ObjectivesThis 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.MethodsA 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.ResultsIn 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.ConclusionThis study indicates that there is potential for use of nisin and its derivatives as therapeutic agents against S. agalactiae infections.