title: Antibacterial effect of oregano essential oil alone and in combination with antibiotics against extended-spectrum beta-lactamase-producing Escherichia coli.
abstract: In this paper, we studied the antibacterial effects of oregano essential oil (OEO) both alone, using a twofold dilution method, and combined with antibiotics, using a checkerboard microtitre assay, against extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli. The result indicated that multiple drug-resistant E. coli was very sensitive to OEO and polymycin; their minimal inhibitory concentration values are 0.5 microL mL(-1) and 0.8 microg mL(-1). The antibacterial effects of OEO in combination with kanamycin were independent against E. coli, with fractional inhibitory concentration (FIC) indices of 1.5. The antibacterial effects of OEO combined with amoxicillin, polymycin, and lincomycin showed an additive effect against E. coli, with FIC indices in the range of 0.625-0.750. The antibacterial effects of OEO in combination with fluoroquinolones, doxycycline, lincomycin, and maquindox florfenicol displayed synergism against E. coli, with FIC indices ranging from 0.375 to 0.500. The combination of OEO with fluoroquinolones, doxycycline, lincomycin, and maquindox florfenicol to treat infections caused by ESBL-producing E. coli may lower, to a great extent, the effective dose of these antibiotics and thus minimize the side effects of antibiotics. This is the first report on OEO against ESBL-producing E. coli.
authors.affiliation: Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, China.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Si
authors.forename: Jinqiang
authors.initials: J
authors.lastname: Hu
authors.forename: Zhichang
authors.initials: Z
authors.lastname: Liu
authors.forename: Zhen-ling
authors.initials: ZL
authors.lastname: Zeng
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology*; D002645:Chickens; D024901:Drug Resistance, Multiple, Bacterial; D004357:Drug Synergism; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology; D008826:Microbial Sensitivity Tests; D009822:Oils, Volatile / Q000302:isolation & purification / Q000494:pharmacology*; D031341:Origanum / Q000737:chemistry*; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D009822:Oils, Volatile; D001618:beta-Lactamases