Search

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of ventilator-associated pneumonia (VAP). Patients with VAP have poorly functioning neutrophils, related to increased levels of the complement fragment C5a. The antibiotic linezolid has been useful in controlling MRSA-related VAP infections; however clinical benefit does not always correlate with antimicrobial effect, suggesting the possibility of immunomodulatory properties. Here the effects of linezolid on healthy and dysfunctional neutrophils (modelled by C5a-induced injury) was investigated. Functional assays (killing, phagocytosis, transmigration, and respiratory burst) were used to assess the effects of pre-, co- and post-incubating linezolid (0.4–40 mg/L) with healthy neutrophils relative to those with C5a-induced injury. C5a decreased neutrophil killing, and phagocytosis of MRSA. Furthermore, C5a significantly decreased neutrophil transmigration to IL-8, but did not affect respiratory burst. Co-incubation of linezolid significantly improved killing of MRSA by dysfunctional neutrophils, which was supported by concomitant increases in phagocytosis. Conversely linezolid impaired killing responses in healthy neutrophils. Pre- or post-incubation of linezolid prior or following C5a induced injury had no effect on neutrophil function. This study suggests that linezolid has immunomodulatory properties that protect human neutrophils from injury and provides insight into its mode of action beyond a basic antibiotic.

The susceptibility of the cell-wall free bacterial pathogens Ureaplasma spp. to Manuka honey was examined. The minimum inhibitory concentration (MIC) of Manuka honey for four Ureaplasma urealyticum and four Ureaplasma parvum isolates was determined. Sensitivity to honey was also compared to clinical isolates with resistance to tetracycline, macrolide and fluoroquinolone antibiotics. Finally step-wise resistance training was utilised in an attempt to induce increased tolerance to honey. The MIC was dependent on the initial bacterial load with 7.5 % and 18.0 % w/v honey required to inhibit U. urealyticum at 1 and 10 6 colour changing units (CCU), respectively, and 4.8 % and 15.3 % w/v required to inhibit U. parvum at 1 and 10 6 CCU, respectively. MIC values were consistently lower for U. parvum compared with U. urealyticum. Antimicrobial activity was seen against tetracycline resistant, erythromycin resistant and ciprofloxacin resistant isolates at 10 5 CCU. No resistance to honey was observed with fifty consecutive challenges at increasing concentrations of honey. This is the first report of the antimicrobial activity of Manuka honey against a cell-wall free bacterial pathogen. The antimicrobial activity was retained against antibiotic resistant strains and it was not possible to generate resistant mutants.

Staphylococcus pseudintermedius is an important member of the skin microbial community in animals and can cause opportunistic infections in both pets and their owners. The high incidence of antimicrobial resistance in S. pseudintermedius highlights that this opportunistic zoonotic pathogen can cause infections which require prolonged and intensive treatment to resolve. Manuka honey has proven efficacy against many bacterial pathogens and is an accepted topical treatment for infections in both veterinary and clinical practice, and so it is a particularly appropriate antimicrobial for use with zoonotic pathogens such as S. pseudintermedius. Here, we demonstrate that not only is manuka honey highly potent against novel multidrug-resistant S. pseudintermedius isolates, it also acts synergistically with clinically relevant antibiotics. In addition, manuka honey modulates S. pseudintermedius virulence activity, even at subinhibitory concentrations. In a clinical setting, these attributes may assist in controlling infection, allowing a more rapid resolution and reducing antibiotic use., Staphylococcus pseudintermedius causes opportunistic infections in dogs. It also has significant zoonotic potential, with the emergence of multidrug resistance leading to difficulty treating both animal and human infections. Manuka honey has previously been reported to inhibit many bacterial pathogens, including methicillin-resistant Staphylococcus aureus, and is successfully utilized in both clinical and veterinary practice. Here, we evaluated the ability of manuka honey to inhibit strains of S. pseudintermedius grown alone and in combination with antibiotics, as well as its capacity to modulate virulence within multiple S. pseudintermedius isolates. All 18 of the genetically diverse S. pseudintermedius strains sequenced and tested were inhibited by ≤12% (wt/vol) medical-grade manuka honey, although tolerance to five clinically relevant antibiotics was observed. The susceptibility of the isolates to four of these antibiotics was significantly increased (P ≤ 0.05) when combined with sublethal concentrations of honey, although sensitivity to oxacillin was decreased. Virulence factor (DNase, protease, and hemolysin) activity was also significantly reduced (P ≤ 0.05) in over half of isolates when cultured with sublethal concentrations of honey (13, 9, and 10 isolates, respectively). These findings highlight the potential for manuka honey to be utilized against S. pseudintermedius infections. IMPORTANCE Staphylococcus pseudintermedius is an important member of the skin microbial community in animals and can cause opportunistic infections in both pets and their owners. The high incidence of antimicrobial resistance in S. pseudintermedius highlights that this opportunistic zoonotic pathogen can cause infections which require prolonged and intensive treatment to resolve. Manuka honey has proven efficacy against many bacterial pathogens and is an accepted topical treatment for infections in both veterinary and clinical practice, and so it is a particularly appropriate antimicrobial for use with zoonotic pathogens such as S. pseudintermedius. Here, we demonstrate that not only is manuka honey highly potent against novel multidrug-resistant S. pseudintermedius isolates, it also acts synergistically with clinically relevant antibiotics. In addition, manuka honey modulates S. pseudintermedius virulence activity, even at subinhibitory concentrations. In a clinical setting, these attributes may assist in controlling infection, allowing a more rapid resolution and reducing antibiotic use.

The purpose of this study was to investigate the effects of manuka honey on the structural integrity of Pseudomonas aeruginosa ATCC 27853. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of manuka honey for P. aeruginosa were determined by a microtitre plate method, and the survival of bacteria exposed to a bactericidal concentration of manuka honey was monitored. The effect of manuka honey on the structure of the bacteria was investigated using scanning and transmission electron microscopy (SEM and TEM, respectively). The MIC and MBC values of manuka honey against P. aeruginosa were 9.5% (w/v) and 12% (w/v) respectively; a time-kill curve demonstrated a bactericidal rather than a bacteriostatic effect, with a 5 log reduction estimated within 257 min. Using SEM, loss of structural integrity and marked changes in cell shape and surface were observed in honey-treated cultures. With TEM, these changes were confirmed, and evidence of extensive cell disruption and lysis was found. Manuka honey does not induce the same structural changes in P. aeruginosa as those observed in staphylococci. Our results indicate that manuka honey has the potential to be an effective inhibitor of P. aeruginosa.

The purpose of this study was to investigate the effect of manuka honey on Staphylococcus aureus in order to identify the intracellular target site. The mode of inhibition of manuka honey against S. aureus NCTC 10017 was investigated by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and the effect of time on viability. Structural changes were observed by scanning (SEM) and transmission electron microscopy (TEM) of cells suspended for 4 h at 37 degrees C in 0.05 mM Tris buffer containing 10% (w/v) manuka honey and were compared to cells in buffer alone or buffer containing 10% (w/v) artificial honey (to assess osmotic damage). A bactericidal mode of inhibition for manuka honey on S. aureus was established. Marked structural changes in honey-treated cells were seen only with TEM, where a statistically significant increase in the number of whole cells with completed septa compared to untreated cells were observed (P0.05). Structural changes found with TEM suggest that honey-treated cells had failed to progress normally through the cell cycle and accumulated with fully formed septa at the point of cell division without separating. Sugars were not implicated in this effect. The staphylococcal target site of manuka honey involves the cell division machinery.

Pseudomonas and Burkholderia pose a significant health threat to people with chronic respiratory conditions; the resistance inherent in these bacteria indicates that new antimicrobial strategies are required. Susceptibility of 56 strains of P. aeruginosa and 55 strains of Burkholderia to manuka honey, tobramycin and colistin using microbroth dilution and E strip was determined. MICs of antibiotics with honey were determined to search for synergistic combinations against two representative strains of each genus. All strains exhibited susceptibility to honey ≤10 % (w/v); mean susceptibility of Burkholderia (4.6 % w/v) was lower than P. aeruginosa (7.3 % w/v). Synergistic or additive combinations were found with all four strains tested. Combinations of manuka honey with antibiotics can be used to lower the MIC need to successfully inhibit both P. aeruginosa and B. cepacia. The use of honey as a combination agent may be possible for the management of P. aeruginosa and B. cepacia.

Resistance to antibiotics continues to rise and few new therapies are on the horizon. Honey has good antibacterial activity against numerous microorganisms of many different genera and no honey-resistant phenotypes have yet emerged. The mechanisms of antimicrobial activity are just beginning to be understood; however, it is apparent that these are diverse and often specific for certain groups or even species of bacteria. Manuka honey has been most thoroughly characterized and is commercially available as a topical medical treatment for wound infections. Furthermore, since most data are available for this honey, there is a considerable focus on it in this review. It is becoming evident that honeys are more than just bactericidal, as they impact on biofilm formation, quorum sensing and the expression of virulence factors. With this in mind, honey represents an attractive antimicrobial treatment that might have the potential to be used alongside current therapies as a prophylactic or to treat wound infection with multidrug-resistant bacteria in future.

Aim: To characterize the effect of manuka honey on medically important wound bacteria in vitro, focusing on its antiadhesive properties. Materials & methods: Crystal violet biofilm assays, fluorescent microscopy, protein adhesion assay and gentamicin protection assay were used to determine the impact of manuka honey on biofilm formation, human protein binding and adherence to/invasion into human keratinocytes. Results: Manuka honey effectively disrupted and caused extensive cell death in biofilms of Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus pyogenes. Sublethal doses of manuka honey inhibited bacterial adhesion to the fibronectin, fibrinogen and collagen. Manuka honey impaired adhesion of laboratory and clinical isolates of S. aureus, P. aeruginosa and S. pyogenes to human keratinocytes in vitro, and inhibited invasion by S. pyogenes and homogeneous vancomycin intermediate S. aureus. Conclusion: Manuka honey can directly affect bacterial cells embedded in a biofilm and exhibits antiadhesive properties against three common wound pathogens.

Objectives: Honey is an ancient wound remedy that has recently been introduced into modern clinical practice in developed countries. Manuka honey inhibits growth of methicillin-resistant Staphylococcus aureus (MRSA) by preventing cell division. In Gram-negative bacteria a synergistic interaction between honey and antibiotics has been suggested. We aimed to determine the effect of manuka honey on oxacillin resistance in MRSA. Methods: Inhibition of MRSA by manuka honey and oxacillin separately and in combination was tested by disc diffusion, Etest strips, serial broth dilution, chequerboards and growth curves. Results: Manuka honey and oxacillin interacted synergistically to inhibit MRSA. Manuka honey reversed oxacillin resistance in MRSA, and down-regulation of mecR1 was found in cells treated with manuka honey. Conclusions: Microarray analysis showed that exposure of MRSA to inhibitory concentrations of manuka honey resulted in down-regulation of mecR1. Here we demonstrated that subinhibitory concentrations of honey in combination with oxacillin restored oxacillin susceptibility to MRSA. Other honey and antibiotic combinations must now be evaluated.

Antimicrobial agents have been used with varying success in the treatment of wound infections for thousands of years. Without knowing the identity of wound pathogens, ancient civilizations develope...

Objectives: The aim of this study was to investigate the effect of manuka honey, artificial honey and an antibacterial component (methylglyoxal) on cell division in methicillin-resistant Staphylococcus aureus (MRSA). Methods: Viability of epidemic MRSA-15 NCTC 13142 incubated with manuka honey, artificial honey and methylglyoxal was determined, and structural effects monitored by electron microscopy. Activity of murein hydrolase (a peptidoglycan-degrading enzyme implicated in cell separation, encoded by atl) was estimated by cell wall hydrolysis and zymography; expression of atl was quantified by real-time PCR. Results: Growth of MRSA was inhibited by 5%, 10% and 20% (w/v) manuka honey and 10% (w/v) artificial honey containing methylglyoxal, but not 10% (w/v) artificial honey. Statistically significantly increased numbers of cells containing septa and increased cell diameter (P,0.001 and P,0.001, respectively) were found in MRSA exposed to 5%, 10% or 20% (w/v) manuka honey, but not 10% (w/v) artificial honey with and without methylglyoxal. Intracellular activity of murein hydrolase was elevated in MRSA grown in 10% (w/v) artificial honey and at undetectable levels in MRSA treated with 10% (w/v) manuka honey. Increased atl expression was found in MRSA treated with 10% (w/v) manuka honey and 10% artificial honey containing methylglyoxal. Conclusions: Enlarged cells containing septa were observed in MRSA exposed to inhibitory concentrations of manuka honey, suggesting that cell division was interrupted. These changes were not caused by either the sugars or methylglyoxal in honey and indicate the presence of additional antibacterial components in manuka honey.

Following the discovery of synergistic action between oxacillin and manuka honey against methicillin-resistant Staphylococcus aureus, this study was undertaken to search for further synergistic combinations of antibiotics and honey that might have potential in treating wounds. Fifteen antibiotics were tested with and without sublethal concentrations of manuka honey against each of MRSA and Pseudomonas aeruginosa using disc diffusion, broth dilution, E strip, chequerboard titration and growth curves. Five novel antibiotic and manuka honey combinations were found that improved antibacterial effectiveness in vitro and these offer a new avenue of future topical treatments for wound infections caused by these two important pathogens.