Abstract
In recent years, the scientific community has focused on the development of new antibiotics to address the difficulties linked to biofilm-forming microorganisms and drug-resistant infections. In this respect, synthetic antimicrobial peptides (AMPs) are particularly regarded for their therapeutic potential against a broad spectrum of pathogens. In this work, the antimicrobial and antibiofilm activities of the peptide WMR-K towards single and dual species cultures of Candida albicans and Klebsiella pneumoniae were investigated. We found minimum inhibitory concentration (MIC) values for WMR-K of 10 µM for K. pneumoniae and of 200 µM for C. albicans. Furthermore, sub-MIC concentrations of peptide showed an in vitro inhibition of biofilm formation of mono and polymicrobial systems and also a good biofilm eradication even if higher concentrations of it are needed. In order to provide additional evidence for the effect of the examined peptide, a study of changes in extracellular metabolites excreted and/or uptaken from the culture medium (metabolomic footprinting) in the poly-microbial association of C. albicans and K. pneumoniae in presence and absence of WMR-K was performed. Comparing to the untreated dual species biofilm culture, the metabolomic profile of the WMR-K treated culture appears significantly altered. The differentially expressed compounds are mainly related to the primary metabolic pathways, including amino acids, trehalose, pyruvic acid, glycerol and vitamin B6.
Highlights
Biofilms are responsible for approximatively 80% of microbial infections in humans, and they have been recovered from all sorts of habitats and surfaces, from aquatic environments to implanted medical devices and artificial industrial structures, passing through plant and mammalian tissues [1,2,3,4]
Microorganisms organized in biofilms undergo epigenetic changes in their state with respect to the planktonic form consisting of alterations in cell morphology, communication between cells, expression of some genes, production of an extracellular matrix made of carbohydrates, proteins and nucleic acids and, above all, evidence of phenotypic characteristics, such as resistance to antimicrobial agents [5,6]
OFDigcuutr=e m1. eBainofoilfmnecghaatrivacetceorinztartoilown.it(hA3) Btiimofeislmadgdriotiwonthoof fSDsin. Qanudandtuifiaclastpioencioefs vmiaibcrleoocregllaonfisKmlesb.s(ienll=a p3n, e±umSDon).iaOe Dancudt = Cmanedaindaoaflbniecganatsivine pcoonlytmroilcwroibthia3l btiimofielsmadadt 2it4ioannodf4S8Dh. ((Bn)=Q3u, a±ntSiDfic)a. tion of viable cell of Klebsiella pneumoniae and Candida albicans in polymicrobial biofilm at 24 and 48 h (n = 3, ± standard deviation (SD))
Summary
Biofilms are responsible for approximatively 80% of microbial infections in humans, and they have been recovered from all sorts of habitats and surfaces, from aquatic environments to implanted medical devices and artificial industrial structures, passing through plant and mammalian tissues [1,2,3,4]. Microorganisms organized in biofilms undergo epigenetic changes in their state with respect to the planktonic form consisting of alterations in cell morphology, communication between cells, expression of some genes, production of an extracellular matrix made of carbohydrates, proteins and nucleic acids and, above all, evidence of phenotypic characteristics, such as resistance to antimicrobial agents [5,6] The latter is one of the most common features of microbial biofilms and, for this reason, diseases involving biofilms are generally chronic and difficult to treat with common antibiotics [7,8]. Multiple microbial species are closely associated in the poly-microbial biofilms providing particular advantages to each species when compared with single-species biofilms [11,12]
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