Evaluation of glycerol antiseptic effect on Gram positive and Gram negative bacteria

Objectives: To assess glycerol antibacterial activity against both Gram positive and negative microorganisms, detect impact of increasing glycerol concentration in bacterial cultures on extra/ intracellular Glycerol-3-phosphate (G3P) concentration, evaluate antiseptic efficacy of different glycerol/alcohol formulations and monitor HCWs tolerability to these formulations to recommend the best antiseptic preparation in vitro. Background: The progressively rising nosocomial infections have enforced the need for novel infection prevention modalities. Glycerol emerges as a significant and cheap antibacterial agent against both Gram positive and negative organisms without any toxic effects. Methodology: Different glycerol/ethanol formulations were evaluated for both bacterial inhibitory and bactericidal activity against selected bacteria (4 reference and 5 clinical strains). Effect of glycerol/ethanol combination was tested by checkerboard method. Colorimetric assay of extra and intracellular bacterial concentration of G3P was done. Skin tolerance of involved HCWs was evaluated against obtained bactericidal formulations including; 80% ethanol (E80)without glycerol (G0) as group (A), E80G1.45 (B), E80G20 (C)and E0G80 as group (D). Results: Microbial growth inhibition was detected at G40E40, G40E60, G1.45 E80 and G20 E80 for most strains. No visible growth (bactericidal effect) was detected with G80, G20 E80 and G1.45 E80. Glycerol/ethanol combination showed synergistic effect against Enterococcus faecalis and biofilm producing MRSA with additive effect against Proteus mirabilis, staphylococcus aureus. Acinetobacter baumannii displayed indifference. No antagonism was detected. G3P levels were positively correlated with added glycerol concentration. E80G20 achieved HCWs maximum tolerability (100%) followed by E0G80 (92.3%). Conclusion: E80G20 and E0G80 were superior to WHO recommended E80G1.45. However, more advanced studies are needed.