Viktor Majtan

Anti-biofilm Effects of Honey Against Wound Pathogens Proteus mirabilis and Enterobacter cloacae

Biofilm growth and its persistence within wounds have recently been suggested as contributing factors to impaired healing. The goal of this study was to investigate the anti‐biofilm effects of several honey samples of different botanical origin, including manuka honey against Proteus mirabilis and Enterobacter cloacae wound isolates.

Methylglyoxal-induced modifications of significant honeybee proteinous components in manuka honey: Possible therapeutic implications.

Methylglyoxal (MGO) is a major antibacterial component of manuka honey. Another antibacterial component found in Revamil honey, peptide defensin1, was not identified in manuka honey. The primary aim of the study was to evaluate the content of defensin1 in honeys of different botanical origins and to investigate a presumed effect of reactive MGO on defensin1 and a dominant protein of honey MRJP1 in manuka honey. Immunoblotting of honey samples showed that defensin1 was a regular but quantitatively variable component of honeys. One of the reasons of varying contents of defensin1 in different honeys seems to be constitutive but varying defensin1 expression in individual honeybees in bee populations that we documented on samples of nurse and forager bees by RT-PCR. Comparative analyses of honeys revealed a size modification of defensin1, MRJP1 and probably also α-glucosidase in manuka honey. We further showed that (i) the treatment of purified defensin1 in solution containing high amount of MGO caused a time-dependent loss of its antibacterial activity and (ii) increasing MGO concentrations in a non-manuka honey were connected with a gradual increase in the molecular weight of MRJP1. Obtained results demonstrate that MGO abrogates the antibacterial activity of defensin1 and modifies MRJP1 in manuka honey. We assume that MGO could also have negative effects on the structure and function of other proteins/peptides in manuka honey, including glucose oxidase, generating hydrogen peroxide.

In vitro effect of subinhibitory concentrations of antibiotics on biofilm formation by clinical strains of Salmonella enterica serovar Typhimurium isolated in Slovakia

Aims:  In this study, we examined the biofilm formation of 75 Salmonella enterica serovar Typhimurium (Salm. Typhimurium) human clinical isolates and the effect of subinhibitory concentrations (sub‐MICs) of gentamicin, ciprofloxacin and cefotaxime on biofilm formation and exopolysaccharides (EPS) production.

Fir honeydew honey flavonoids inhibit TNF-α-induced MMP-9 expression in human keratinocytes: a new action of honey in wound healing

Matrix metalloproteinase-9 (MMP-9) appears to be a major protease responsible for the degradation of matrix and growth-promoting agents in chronic wounds. Honey has been successfully used for treating non-healing wounds associated with infections. However, the mechanisms of its action at the cellular level have remained poorly understood. The aim of this study was to investigate the effect of fir honeydew honey on TNF-α-induced MMP-9 expression and secretion from human keratinocytes (HaCaT) and to identify the honey component(s) responsible for a discovered effect. A C18 solid-phase column was used for preparation of honey aqueous extract (HAE). Expression and production of MMP-9 by HaCaT cells were determined by reverse transcription-PCR, gelatine zymography and Western blot analysis using a polyclonal antibody against MMP-9. We found that HAE inhibited TNF-α-induced production of MMP-9 in keratinocytes in a dose-dependent manner at both the mRNA and protein levels. Apigenin and kaempferol, identified flavonoids in HAE, markedly inhibited MMP-9 production from HaCaT and epidermal keratinocytes. Taken together, fir honeydew honey, which contains certain flavonoids, prevents TNF-α-induced proteolytic activity in cutaneous inflammation. Thus, our findings provide clear evidence that honey may serve as a natural treatment for dermatological problems associated with a persistent inflammation.

Honeydew honey as a potent antibacterial agent in eradication of multi‐drug resistant Stenotrophomonas maltophilia isolates from cancer patients

Multi‐drug resistance in nosocomial pathogens is a continually evolving and alarming problem in health care units. Since ancient times, honey has been used successfully for the treatment of a broad spectrum of infections with no risk of resistance development.

Selective Antibiofilm Effects of Lucilia sericata Larvae Secretions/Excretions against Wound Pathogens

Background. Maggot debridement therapy (MDT), using Lucilia sericata larvae, represents efficient, simple, and low-cost therapy for the treatment of chronic wounds. Aim. The aim was to investigate the antibiofilm activity of maggot excretions/secretions (ES) against biofilm of wound isolates Staphylococcus aureus (S. aureus), Enterobacter cloacae (E. cloacae), and Proteus mirabilis (P. mirabilis). Methods. Quantification of biofilm formation, was carried out using a microtiter plate assay. Proteolytic activity of maggot ES was performed using skim milk agar plates. A solid phase extraction and reverse phase HPLC C18 chromatography were employed to the isolate of maggot ES antibiofilm compounds. Results. Maggot ES at 100 mg/mL concentration significantly reduced biofilm formation thus disrupting established biofilm of E. cloacae. Heat-treated ES did not show any antibiofilm activity towards E. cloacae. Similar results were obtained in the case of S. aureus; however, the heat-treatment of maggot ES did not affect its antibiofilm activity. Moreover, a compound with molecular weight of 25 kDa exhibiting antibiofilm activity was identified in maggot ES. On the other hand, maggot ES protected and even stimulated P. mirabilis biofilm formation. Conclusions. Our results suggest that maggot ES may act selectively against different bacterial strain.

Increasing trend of resistance to nalidixic acid and emerging ceftriaxone and ciprofloxacin resistance in Salmonella enterica serovar Typhimurium in Slovakia, 2005 to 2009

A 5-year survey from 2005 to 2009 revealed an increasing trend of resistance to nalidixic acid (from 0% in 2005 to 11% in 2009) among 858 clinical isolates of Salmonella Typhimurium. In addition, 10 ceftriaxone-resistant and 3 ciprofloxacin-resistant Salmonella Typhimurium isolates were detected over the period of study.

Postantibiotic effect of some antibiotics on the metabolism of Pseudomonas aeruginosa.

The influence of the postantibiotic effects (PAEs) of ciprofloxacin, pefloxacin, imipenem, meropenem and amikacin in the suprainhibitory concentrations (2 × and 4 × MIC) on the metabolic processes of P. aeruginosa was studied. The synthesis of macromolecules was expressed by influencing of the incorporation rate of [14C] adenine and [14C] leucine. Remarkable affecting of both biosynthetic processes evoked the suprainhibitory concentration 4 × MIC of meropenem by inhibition of the nucleic acids synthesis to 76.1% and proteins synthesis to 61.1% against the control. The suprainhibitory concentration 4 × MIC of both pefloxacin and ciprofloxacin affected the highest suppression of the endogenous respiration to 16.5% and to 20.3%, respectively. The respiration was influenced the least after the effect of meropenem in the both suprainhibitory concentrations tested. According to our knowledge, this is first report about the evaluation of the endogenous respiration after PAE. In this study we demonstrated the inhibitory effects of 4 × MIC concentration of antibiotics studied on the metabolic processes of P. aeruginosa. The results suggest a multiple mechanism for the PAE.

Trends in phage types of Salmonella enterica serovars Enteritidis and Typhimurium isolated in Slovakia from 1995 to 2009

The phage typing of 3900 isolates of Salmonella Enteritidis and 1741 isolates of Salmonella Typhimurium has been carried out in the period 1995-2009. Among Salmonella Enteritidis in individual years, the most prevalent phage type (PT) was 8. The most predominant PTs of Salmonella Typhimurium were DT104 and U302.

Dimethyl sulfoxide attenuates TNF-α-induced production of MMP-9 in human keratinocytes.

Dimethyl sulfoxide (DMSO), an aprotic solvent, is found to be useful as a topical agent with antioxidant effects in treatment of chronic wounds. However, the effects of DMSO on matrix metalloproteinase-9 (MMP-9) production in the presence of an inflammatory environment as in the case of disordered wound healing has not been previously investigated. The aim of this study was to investigate whether TNF-α-induced MMP-9 levels and MMP-9 mRNA expression from human keratinocytes (HaCaT) might be attenuated by DMSO. Human keratinocytes were treated with DMSO (0.1–1%) for 24 h and then exposed to tumor necrosis factor (TNF)-α (10 ng/ml) for an additional 24 h. Expression and production of MMP-9 from HaCaT cells were determined by reverse transcription polymerase chain reaction (RT-PCR) and gelatin zymography, respectively. Results showed that DMSO inhibited production of both MMP-9 levels and MMP-9 mRNA expression in TNF-α-stimulated cells in a concentration-dependent manner. Inhibition of MMP-9 levels was statistically significant at DMSO concentrations of 0.75% and higher. Similarly, the increase of MMP-9 mRNA expression levels in TNF-α-stimulated cells was markedly reduced by DMSO. Data suggest that DMSO may attenuate the deleterious effects of MMP-9 through downregulation at the transcription level. Therefore, DMSO may provide a good strategy to prevent TNF-α-induced proteolytic activity in cutaneous inflammatory reactions.