MRJP1-containing glycoproteins isolated from honey, a novel antibacterial drug candidate with broad spectrum activity against multi-drug resistant clinical isolates.

Robert Lannigan,Katrina Brudzynski,Calvin Sjaarda

doi:10.3389/fmicb.2015.00711

Robert Lannigan, Katrina Brudzynski + Show 1 more

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https://doi.org/10.3389/fmicb.2015.00711

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Abstract

The emergence of extended- spectrum β-lactamase (ESBL) is the underlying cause of growing antibiotic resistance among Gram-negative bacteria to β-lactam antibiotics. We recently reported the discovery of honey glycoproteins (glps) that exhibited a rapid, concentration-dependent antibacterial activity against both Gram-positive Bacillus subtilis and Gram-negative Escherichia coli that resembled action of cell wall-active β-lactam drugs. Glps showed sequence identity with the Major Royal Jelly Protein 1 (MRJP1) precursor that harbors three antimicrobial peptides: Jelleins 1, 2, and 4. Here, we used semi-quantitative radial diffusion assay and broth microdilution assay to evaluate susceptibility of a number of multi-drug resistant (MDR) clinical isolates to the MRJP1-contaning honey glycoproteins. The MDR bacterial strains comprised three methicillin-resistant Staphylococcus aureus (MRSA), four Pseudomonas aeruginosa, two Klebsiella pneumoniae, two vancomycin-resistant Enterococci (VRE), and five ESBL identified as one Proteus mirabilis, three E. coli, and one E. coli NDM. Their resistance to different classes of antibiotics was confirmed using automated system Vitek 2. MDR isolates differed in their susceptibility to glps with MIC90 values ranging from 4.8 μg/ml against B. subtilis to 14.4 μg/ml against ESBL K. pneumoniae, Klebsiella spp. ESBL and E. coli and up to 33 μg/ml against highly resistant strains of P. aeruginosa. Glps isolated from different honeys showed a similar ability to overcome bacterial resistance to β-lactams suggesting that (a) their mode of action is distinct from other classes of β-lactams and that (b) the common glps structure was the lead structure responsible for the activity. The results of the current study together with our previous evidence of a rapid bactericidal activity of glps demonstrate that glps possess suitable characteristics to be considered a novel antibacterial drug candidate.

Highlights

The multi-drug resistant (MDR) bacterial pathogens pose a significant threat to control and treat bacterial infections
MALDI TOF of Honey Glycoproteins Honey glycoproteins used in this study were isolated using Concavalin A-agarose which binds high-mannose-type N-glycans with high affinity
The susceptibility of isolates to two glycoproteins, G208 and G217, isolated from two different buckwheat honeys, was evaluated and compared to that of ampicillin-sensitive control. Both glycoproteins have been shown to exhibit antibacterial activity against K. pneumonia 1 and 2 (Table 2; lab number #1 and #19), P. aeruginosa 3 and 4, E. coli NDM 4, and E. coli ESBL 2. These results indicate that MDR of isolates to antibiotics did not affect antibacterial action of glycoproteins (Figure 3 and Table 2)

Summary

Introduction

The multi-drug resistant (MDR) bacterial pathogens pose a significant threat to control and treat bacterial infections. ESBL genes are consecutively expressed and can be transfer to other bacterial species by horizontal gene transfer via mobile elements such as plasmids and transposons (Bradford, 2001; Warnes et al, 2012). These mechanisms of transmission effectively accelerate the spread of MDR bacteria causing nosocomial outbreaks worldwide. Because ESBL-producing strains present often MDR phenotypes, in order to overcome their global resistance, new approaches in drug discovery and designs are needed. These challenges led to re-new interest in natural products as an untapped reservoir for drug discovery (Koehn and Carter, 2005; Molinari, 2009; Hayashi et al, 2013)

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