Potency of Netilmicin against Staphylococci Compared to Other Ophthalmic Antibiotics

Netilmicin is a potent and safe antibiotic with a very low incidence of resistance used as a topical ophthalmic medication in bacterial ocular infections. The aim of this study was to compare netilmicin’s Quotient of Inhibitions (QIs) and killing kinetics vs Staphylococci with other ophthalmic antimicrobials. Conjunctival and corneal QIs of netilmicin formulations, in single and multiple doses of administration, were compared with those of tobramycin, ofloxacin, levofloxacin and azithromycin preparations. The same analysis was performed in human tears, comparing netilmicin eye drops solution with tobramycin ofloxacin and levofloxacin. Furthermore, killing kinetics against Staphylococci (ATCC strains and ocular isolates) of the above-cited antibiotics, as well as chloramphenicol, were compared at different time points. QI results showed that in the conjunctiva, netilmicin, in both single and multiple doses of administration, is highly effective against all staphylococcal strains tested, while in the cornea it was particularly active against methicillin-resistant Staphylococci strains. Moreover, in human tears, netilmicin eye drops solution showed a more favourable QI against Staphylococci than tobramycin, ofloxacin and levofloxacin all in single-dose administration regimen. Killing kinetic results showed that netilmicin has a great bactericidal activity vs all the microbe strains tested as netilmicin showed to be almost the most active antibiotic. Results suggest that netilmicin has one of the most favourable killing kinetic and tissue inhibitory effects against Staphylococci than the principal ophthalmic antibiotics on the market

In Vitro Antifungal Activity of Epigallocatechin 3-O-Gallate against Clinical Isolates of Dermatophytes

Previously, we reported that epigallocatechin 3-O-gallate (EGCg) has growth-inhibitory effect on clinical isolates of Candida species. In this study, we investigated the antifungal activity of EGCg and antifungal agents against thirty-five of dermatophytes clinically isolated by the international guidelines (M38-A2). All isolates exhibited good susceptibility to EGCg (MIC50, 2-4 µg/mL, MIC90, 4-8 µg/mL, and geometric mean (GM) MICs, 3.36-4 µg/mL) than those of fluconazole (MIC50, 2-16 µg/mL, MIC90, 4-32 µg/mL, and GM MICs, 3.45-25.8 µg/mL) and flucytosin (MIC50, MIC90, and GM MICs, >64 µg/mL), although they were less susceptible to other antifungal agents, such as amphotericin B, itraconazole, and miconazole. These activities of EGCg were approximately 4-fold higher than those of fluconazole, and were 4 to 16-fold higher than flucytosin. This result indicates that EGCg can inhibit pathogenic dermatophyte species. Therefore, we suggest that EGCg may be effectively used solely as a possible agent or combined with other antifungal agents for antifungal therapy in dermatophytosis

Epigallocatechin-Gallate Enhances the Activity of Tetracycline in Staphylococci by Inhibiting Its Efflux from Bacterial Cells

Epigallocatechin-gallate (EGCg), the major catechin present in green tea extracts, has been shown to have several antibacterial activities, limiting bacterial growth and invasion and acting in synergy with β-lactam antibiotics. In this article, we report that EGCg at doses half and below its calculated MIC of 100 μg/ml, is able to reverse tetracycline resistance in staphylococcal isolates expressing the specific efflux pump Tet(K) and appears to improve the MICs of tetracycline for susceptible staphylococcal isolates as well. The visible effect of EGCg is an increased accumulation of tetracycline inside bacterial cells. This effect is likely due to the inhibition of pump activity, and it is evident not only for Tet(K) pumps but also for efflux pumps of a different class [Tet(B)]. In summary, our data indicate that the observed dramatic enhancement by EGCg of tetracycline activity for resistant staphylococcal isolates is caused by impairment of tetracycline efflux pump activity and increased intracellular retention of the drug, suggesting a possible use of EGCg as an adjuvant in antibacterial therapy

Epigallocatechin Gallate Inhibits Biofilm Formation by Ocular Staphylococcal Isolates

Epigallocatechin gallate (EGCg), the main polyphenol component of green tea, has several antibacterial properties. Here we show that sub-MICs of EGCg appear to decrease slime production, therefore inhibiting biofilm formation by ocular staphylococcal isolates previously characterized for the presence of ica genes by the Congo red agar plate assay and for adhesion to microtiter plates

Susceptibility of methicillin-resistant staphylococci to oregano essential oil, carvacrol and thymol

The aim of this study was to evaluate the susceptibility of methicillin-susceptible and methicillin-resistant staphylococci (MSS, MRS) to oregano essential oil, carvacrol and thymol. The commercial aerial parts of Origanum vulgare L. were hydrodistilled and the essential oil analysed by gas- chromatography/electron impact mass spectrometry. The inhibition efficacy of this essence and its major components was assayed against 26 MSS and 21 MRS, using an agar dilution method. The methicillin resistance was thoroughly typed by Epsilometer test (E-test), polymerase chain reaction for mecA gene detection and PBP2P latex agglutination test. The results clearly demonstrated that the comparison between the susceptibility of MSS and MRS to oregano oil, carvacrol and thymol showed no significant differences (Fisher’s exact test, P>0.05). The best minimum inhibitory concentration values were reported for carvacrol (0.015-0.03%, v/v) followed by thymol (0.03-0.06%, v/v) and oregano oil (0.06-0.125%, v/v