MicrobiologyBytes

Honey has been renowned for its wound-healing properties since ancient times. At least part of its positive influence is attributed to antibacterial properties. With the advent of antibiotics, clinical application of honey was abandoned in modern Western medicine, although in many cultures, it is still used. These days, however, abundant use of antibiotics has resulted in widespread resistance. With the development of novel antibiotics lagging behind, alternative antimicrobial strategies are urgently needed. The potent in vitro activity of honey against antibiotic-resistant bacteria and its successful application in treatment of chronic wound infections not responding to antibiotic therapy have attracted considerable attention.

The broad spectrum antibacterial activity of honey is multifactorial in nature. Hydrogen peroxide and high osmolarity – honey consists of 80% (w/v) of sugars – are the only well-characterized antibacterial factors in honey. Recently, high concentrations of the antibacterial compound methylglyoxal (MGO) were found specifically in Manuka honey, derived from the Manuka tree (Leptospermum scoparium). Until now, no honey has ever been fully characterized, which hampered clinical applications of honey.

How honey kills bacteria. FASEB Journal, 2010. doi: 10.1096/fj.09-150789
With the rise in prevalence of antibiotic-resistant bacteria, honey is increasingly valued for its antibacterial activity. To characterize all bactericidal factors in a medical-grade honey, we used a novel approach of successive neutralization of individual honey bactericidal factors. All bacteria tested, including Bacillus subtilis, methicillin-resistant Staphylococcus aureus, extended-spectrum β-lactamase producing Escherichia coli, ciprofloxacin-resistant Pseudomonas aeruginosa, and vancomycin-resistant Enterococcus faecium, were killed by 10–20% (v/v) honey, whereas 40% (v/v) of a honey-equivalent sugar solution was required for similar activity. Honey accumulated up to 5.62 ± 0.54 mM H2O2 and contained 0.25 ± 0.01 mM methylglyoxal (MGO). After enzymatic neutralization of these two compounds, honey retained substantial activity. Using B. subtilis for activity-guided isolation of the additional antimicrobial factors, we discovered bee defensin-1 in honey. After combined neutralization of H2O2, MGO, and bee defensin-1, 20% honey had only minimal activity left, and subsequent adjustment of the pH of this honey from 3.3 to 7.0 reduced the activity to that of sugar alone. Activity against all other bacteria tested depended on sugar, H2O2, MGO, and bee defensin-1. Thus, we fully characterized the antibacterial activity of medical-grade honey.

Related:

• Manuka honey

Today’s post is from guest blogger Alexis Bonari, freelance writer and blog junkie. She is currently a resident blogger at onlinedegrees.org, researching online degree programs. In her spare time, she enjoys square-foot gardening, swimming, and avoiding her laptop.

MicrobiologyBytes welcomes guest bloggers who would like to contribute occasional posts which conform to the style and content of this site. If you would like to be a guest blogger here, please email your post with a completed copyright release form to me at: alan.cann@gmail.com

Cystic fibrosis (CF), a hereditary chronic disease affecting pulmonary and digestive function in over 70,000 individuals worldwide, has proven difficult to analyze in terms of the relationships among lung function, patient age, and microbial colonization of the airways. In the first study of airway microbial colonies in CF patients ranging from neonates (9 months) to adults (72 years), younger patients have been recorded as having more diverse airway bacteria than their older counterparts. This could imply that more limited bacterial diversity and deteriorating airway health correlate.

The study, conducted at the University of California in San Francisco, analyzed deep-throat swab and expectorated sputum samples from 51 patients at the University’s pediatric and adult CF clinics. Analysis was performed using the PhyloChip microarray, which enabled control for variations in fragmentation, biotinylation, hybridization, washing, staining, and scanning; the resulting data were used to generate a phylogenetic distance matrix. Despite these and many other precautions taken, the study suggests that factors such as unmeasured antibiotic use, chest physical therapy, adherence, nutrition, and other potential variables might encourage more stringent inquiry into the subject of airway microbial diversity as a function of patient age. With the affirmation that bacterial community structure and composition are substantial factors in defining the functionality of microbial assemblage and host health status, future research has the potential to further explain pulmonary health in terms of airway microbiota diversity.

Airway Microbiota and Pathogen Abundance in Age-Stratified Cystic Fibrosis Patients. 2010 PLoS ONE 5(6): e11044. doi:10.1371/journal.pone.0011044
Bacterial communities in the airways of cystic fibrosis (CF) patients are, as in other ecological niches, influenced by autogenic and allogenic factors. However, our understanding of microbial colonization in younger versus older CF airways and the association with pulmonary function is rudimentary at best. Using a phylogenetic microarray, we examine the airway microbiota in age stratified CF patients ranging from neonates (9 months) to adults (72 years). From a cohort of clinically stable patients, we demonstrate that older CF patients who exhibit poorer pulmonary function possess more uneven, phylogenetically-clustered airway communities, compared to younger patients. Using longitudinal samples collected form a subset of these patients a pattern of initial bacterial community diversification was observed in younger patients compared with a progressive loss of diversity over time in older patients. We describe in detail the distinct bacterial community profiles associated with young and old CF patients with a particular focus on the differences between respective “early” and “late” colonizing organisms. Finally we assess the influence of Cystic Fibrosis Transmembrane Regulator (CFTR) mutation on bacterial abundance and identify genotype-specific communities involving members of the Pseudomonadaceae, Xanthomonadaceae, Moraxellaceae and Enterobacteriaceae amongst others. Data presented here provides insights into the CF airway microbiota, including initial diversification events in younger patients and establishment of specialized communities of pathogens associated with poor pulmonary function in older patient populations.

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