MC21-A, a Bactericidal Antibiotic Produced by a New Marine Bacterium, Pseudoalteromonas phenolica sp. nov. O-BC30 ^T , against Methicillin-Resistant Staphylococcus aureus

Abstract

We previously reported a new marine bacterium, Pseudoalteromonas phenolica sp. nov. O-BC30 T , which produced a bactericidal antibiotic against methicillin-resistant Staphylococcus aureus (MRSA). In the present study, we purified an anti-MRSA substance (MC21-A) from the methanol extract of the cells of P. phenolica O-BC30 T and analyzed its chemical structure. MC21-A was determined to be 3,3,5,5-tetrabromo-2,2-biphenyldiol by spectrometric analyses. Its anti-MRSA activity against 10 clinical isolates of MRSA was comparable to that of vancomycin (MC21-A MICs, 1 to 2 g/ml; vancomycin MICs, <0.25 to 2 g/ml). This substance was also high active against Enterococcus serolicida, Enterococcus faecium, and Enterococcus faecalis but was less active against Streptococcus spp. A time-kill study also demonstrated that MC21-A was bactericidal and that its killing rate was much higher than that of vancomycin. The postantibiotic effect (PAE) of MC21-A against a clinical MRSA isolate, strain E 31243, was also comparable to that of vancomycin (MC21-A PAEs, 1.46 to 1.65 h; vancomycin PAEs, 0.84 to 1.43 h). However, a lysis experiment demonstrated that this substance failed to lyse MRSA cells. This substance also did not lyse human erythrocytes. A SYTOX Green staining experiment implied that this substance permeabilized the cell membrane of MRSA as its mode of action. When its activities against a hypersensitive Escherichia coli mutant (KO 1489) and wild-type strains were tested, MC21-A exhibited higher levels of activity against the former. Furthermore, MC21-A was not cytotoxic to human normal fibroblast, rat pheochromocytoma, and Vero cells at concentrations up to 50 g/ml. These results suggest that MC21-A might be useful as a lead compound in the development of new types of anti-MRSA substances with modes of action different from those of vancomycin and teicoplanin.

Biodiversity of Antimicrobial-Producing Actinomycetes Strains Isolated from Dry Dipterocarp Forest Soil in Northeast Thailand

“…This resistant bacterial strain has become a worldwide concern since it is highly prevalent and potentially cause death. It is capable of developing the new clones to resist to almost all currently available antibiotics except vancomycin and teicoplanin (Witte 1999;Isnansetyo and Kamei 2003).…”

“…Nowadays, vancomycin-intermediate Staphylococcus aureus (VISA) and vancomycinresistant Staphylococcus aureus (VRSA) have been reported in several countries (Isnansetyo and Kamei 2003;David and Daum 2010). Thus, there is an urgent needed to the search of new antibiotic agents, particularly against drug-resistant strains.…”

Assessment of Genotypic Diversity of Antibiotic-Producing Pseudomonas Species in the Rhizosphere by Denaturing Gradient Gel Electrophoresis

“…2,4-Diacetylphloroglucinol (DAPG) produced by Pseudomonas fluorescens has activity against a range of plant pathogens, including bacteria, fungi, and nematodes (reviewed in reference 41). Recently, the broad-spectrum activity of DAPG also has drawn attention in the medical area because of the bacteriolytic activity of DAPG against multidrug-resistant Staphylococcus aureus (18). DAPGproducing Pseudomonas spp.…”

Cytotoxicity of Fucoidan from Three Tropical Brown Algae Against Breast and Colon Cancer Cell Lines

“…Cells proliferation was observed by MTT assay (3-[4,5-dimethylthiazol-2-yl] -2,5-diphenyltetrazolium bromide [Sigma-Aldrich, St. Louis, MO, USA]). 27 Growth was detected with a microplate reader at a wavelength of 570 nm. The growth rate of cells exposed to fucoidan compared to the positive and negative controls, and then the cells mortality expressed in percent (%) was calculated.…”