Electron-microscopic Study of the Bactericidal Effect of OPB-2045, a New Disinfectant Produced from Biguanide Group Compounds, Against Methicillin-resistant Staphylococcus aureus

Abstract

The bactericidal effect of OPB-2045, a new disinfectant produced from biguanide group compounds, against methicillin-resistant Staphylococcus aureus (MRSA), MRSA IID 1677, was investigated by transmission electron microscopy. OPB-2045 showed strong bactericidal activity against MRSA. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of OPB-2045 against the test strain were 0.78 and 1.56 microg mL(-1), respectively. The test bacteria were incubated in the presence of OPB-2045 at 1/2 MIC (0.39 microg mL(-1)), 1 MIC (0.78 microg mL(-1)), 2 MIC (1 MBC, 1.56 microg mL(-1)), 4 MIC (2 MBC, 3.13 microg mL(-1)) or 10 MIC (5 MBC, 7.8 microg mL(-1)) at 37 degrees C for 30 s, 3 min, 30 min or 6h. The morphology of the cells was examined by transmission electron microscopy. The cell damage observed after 30-min or 6-h incubation in the presence of OPB-2045 at 1/2 or 1 MIC was the same as that at 2, 4 or 10 MIC. The numbers of damaged MRSA cells increased according to the increase in concentration of added disinfectant, and the image of bacteriolysis was observed, too. After treatment at 1/2 or 1 MIC, a few leaking cells were recognized, but no destroyed cells were found. No morphological changes were observed after treatment at 1 or 2 MIC for 30 s, 3 min or 30 min. When the incubation time was extended to 6 h, morphological changes in the MRSA cells treated at 1 or 2 MIC were observed. When examining the relationship between the numbers of surviving bacteria and the MIC (MBC) values in soybean casein digest broth, no decrease in MRSA cell numbers was recognized in the untreated control or at 1/2 MIC, but a marked decrease in MRSA cell numbers was recognized as the OPB-2045 concentration was increased. The new disinfectant OPB-2045 would make a useful contribution to the medical field for the prevention of infections caused by pathogenic bacteria such as MRSA.

Bactericidal Effects and Mechanism of Action of Olanexidine Gluconate, a New Antiseptic

“…This difference might be related to the bactericidal effect against S. aureus. The results above, combined with the electron microscope observations by Sakagami et al (35), suggest that olanexidine binds to the surface of S. aureus, where it disrupts the membrane, causing cytoplasmic components to leak from the cell, thereby killing it.…”

“…This hypothesis is supported by observations with electron microscopy of P. aeruginosa and methicillin-resistant S. aureus treated by olanexidine hydrochloride. Sakagami et al (34,35) reported that olanexidine hydrochloride released intracellular components from such bacteria at the level of the MIC. On the other hand, chlorhexidine did not disrupt the membrane of the LUVs but did disrupt that of E. coli.…”

Virucidal Efficacy of Olanexidine Gluconate as a Hand Antiseptic Against Human Norovirus

“…Thus, the difference in the virucidal efficacy of OLG-HR and other antiseptics is thought to be due to differences in the capsid structure stability by a trivial difference in the amino acid sequence structure, which needs to be addressed in a future study. The mechanism of action of virucidal efficacy of OLG-HR against human norovirus is not well understood, but it is known that at relatively high concentrations, olanexidine aggregates the cells through a protein-denaturing effect (Hagi et al 2015;Sakagami et al 2000). Furthermore, the virucidal effect of OLG-HR against non-enveloped viruses such as feline calicivirus and bacteriophage MS2 has been found to be stronger under basic conditions (data not shown).…”

In Vitro Efficacy of a Polyhexamethylene Biguanide‐Impregnated Gauze Dressing Against Bacteria Found in Veterinary Patients

“…PHMB is rapidly bactericidal at high concentrations, causing disruption of bacterial cytoplasmic membranes with eventual leakage and precipitation of cell contents 15 . When tested by agar and broth dilution methods at 1.56–60 μg/mL, PHMB was effective against various pathogens, including methicillin‐resistant Staphylococcus aureus , Pseudomonas aeruginosa , Streptococcus equi , and Erysipelothrix rhusiopathiae 16,17 . Solutions of 0.02% PHMB are clinically effective against Acanthamoeba sp.…”