Antibiofilm activity of Rosaceae honeys against Acinetobacter baumannii and their prebiotic effect on Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus

INTRODUCTION

Natural products are an important source of therapeutic agents for their antimicrobial and prebiotic properties in an era of increasing antibiotic resistance. The antimicrobial and prebiotic properties of honeys from hawthorn, cherries, raspberries, almonds and apples were investigated.

METHODS

The antimicrobial activity of the honey, diluted 1:1 w: vol with deionized water and filtered, was assessed (20 mg/ml) by evaluating, through the crystal violet test, its ability to inhibit the biofilm of the high-risk pathogen Acinetobacter baumannii, and, through the MTT test, its capacity to affect the metabolism of the A. baumannii sessile cells. The prebiotic potentiality of the honey was assessed on Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus, to evaluate the capacity to affect their growth and to inhibit the biofilm of that pathogen.

RESULTS

The honeys inhibited the biofilm of A. baumannii with percentages ranging from 43.49% (cherry) to 59.43% (apple). The honeys did not affect the metabolism of the sessile cells of the pathogen (except cherry honey, 27.16%), so other inhibition mechanisms should be investigated. Rosaceae honey positively affected the growth of the two lactobacilli, with an increase ranging from 8-fold to even 13-fold (when L. rhamnosus grew in the presence of cherry honey), compared to the control, grown in MRS medium. The biofilm inhibitory activity of the supernatants of lactobacilli showed that all types of honey were more effective than the control, with inhibition percentages of up to 34.24% (supernatant of L. plantarum grown with apple honey), and was especially evident on the metabolism of sessile cells, as demonstrated by the high inhibition percentages observed (up to 61.31%), higher than the supernatant of the two strains conventionally grown.

CONCLUSIONS

Future work will focus on the effect of Rosaceae honey on other pathogenic bacteria and probiotics, with the aim of expanding knowledge of its biological properties and assessing the consequent possibilities of its use.