No abstract

Pseudomonas aeruginosa is an opportunistic pathogen that can form biofilms, which confer resistance to immune clearance and antibacterial treatment. Therefore, effective strategies to prevent biofilm formation are warranted. Here, 103 P. aeruginosa clinical isolates were quantitatively screened for biofilm formation ability via the tissue culture plate method. The effects of lysozyme (hydrolytic enzyme) and proteinase K (protease) on biofilm formation were evaluated at different concentrations. Lysozyme (30 μg/mL), but not proteinase K, significantly inhibited biofilm formation (19% inhibition). Treatment of 24-hour-old biofilms of P. aeruginosa isolates with 50 times the minimum inhibitory concentrations (MICs) of ceftazidime and cefepime significantly decreased the biofilm mass by 32.8% and 44%, respectively. Moreover, the exposure of 24-hour-old biofilms of P. aeruginosa isolates to lysozyme (30 μg/mL) and 50 times MICs of ceftazidime or cefepime resulted in a significant reduction in biofilm mass as compared with the exposure to lysozyme or either antibacterial agent alone. The best antibiofilm effect (49.3%) was observed with the combination of lysozyme (30 μg/mL) and 50 times MIC of cefepime. The promising antibiofilm activity observed after treatment with 50 times MIC of ceftazidime or cefepime alone or in combination with lysozyme (30 μg/mL) is indicative of a novel strategy to eradicate pseudomonal biofilms in intravascular devices and contact lenses.

The spread of multidrug-resistant pathogens together with the development of fatal cases of infectious microorganisms is on the rise. Therefore, there must be new approaches for combating pathogenic microorganisms, either by overcoming antibiotic resistance or via inhibiting their virulence factors. Several virulence factors extremely increase the antimicrobial resistance of various species of pathogens; as a result, the screening of antivirulence agents has gained more and more attention recently. In this aspect, non-traditional strategies that are considered promising in overcoming virulence and pathogenicity of microorganisms will be discussed including; quorum sensing inhibition, antibiofilm, control of the global regulators, bacteriocins and bacteriophages. Applying these methods could provide innovative approaches for competing microbial resistance and virulence.

Hyaluronidase enzyme (HysA) is an extracellular enzyme that is considered to be an important virulence factor for Staphylococcus aureus. We screened the production of HysA enzyme in the spent media of Egyptian clinical isolates (32 isolates) via phenotypic plate assay. We found that 75% of the isolates (24 isolates) were able to produce HysA enzyme. We designed primers for qPCR analysis of hysA mRNA expression that was derived from the alignment of hysA gene sequences of 41 strains of S. aureus. The designed primers could be used for the amplification of hysA in 79.2% of the isolates (19 isolates) that were positive for HysA production as demonstrated by phenotypic plate assay. A significant positive correlation, as indicated by Pearson correlation analysis (r = 0.84 at P < 0.001), was found between phenotypic plate assay and qPCR of mRNA expression of hysA in the investigated isolates of S. aureus. In conclusion, we analyzed for the first time hysA mRNA expression via qPCR in S. aureus. Additionally, our work showed a good agreement between the phenotypic assay of HysA production via plate assay and hysA expression in S. aureus. The qPCR analysis of this study could be used as a more reliable quantitative method for hysA expression analysis particularly in infected animal models of S. aureus.