title: Growth of microorganisms in propofol, thiopental, and a 1:1 mixture of propofol and thiopental.
abstract: To assess and compare the growth of four microorganisms in solutions of intravenous anesthetics, known quanta of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were inoculated into propofol, thiopental, a 1:1 mixture of propofol and thiopental, and normal saline. All microorganisms were taken from standard stock cultures and incubated for 24 h (48 h for C. albicans). Growth of microorganism in each drug was compared by counting the number of colony forming units (CFUs) grown from a subculture of each inoculated anesthetic at 0, 3, 6, 12, and 24 h. The study shows that propofol strongly supports the growth of E. coli and C. albicans but is bacteriostatic toward S. aureus and weakly bactericidal toward P. aeruginosa. In contrast, both thiopental and the 1:1 mixture of propofol and thiopental behaved differently, exhibiting markedly bactericidal properties toward E. coli, S. aureus, and P. aeruginosa and a bacteriostatic effect on C. albicans. This finding supports recommendations that a strict aseptic technique should be used when handling propofol and that the contents of an ampoule should be used within 6 h of aspirating. The measured high pH of both thiopental and the 1:1 mixture of propofol and thiopental compared to propofol alone suggests pH to be a major factor in determining whether a given drug will support microbial growth.
authors.affiliation: Department of Anaesthesia, Royal Alexandra Hospital, Edmonton, Alberta, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Crowther
authors.forename: J
authors.initials: J
authors.lastname: Hrazdil
authors.forename: D T
authors.initials: DT
authors.lastname: Jolly
authors.forename: J C
authors.initials: JC
authors.lastname: Galbraith
authors.forename: M
authors.initials: M
authors.lastname: Greacen
authors.forename: M
authors.initials: M
authors.lastname: Grace
mesh_terms: D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D002176:Candida albicans / Q000187:drug effects / Q000254:growth & development*; D015169:Colony Count, Microbial; D004338:Drug Combinations; D004340:Drug Contamination; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development*; D006863:Hydrogen-Ion Concentration; D015742:Propofol / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000254:growth & development*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development*; D013874:Thiopental / Q000494:pharmacology
chemical_list: D018686:Anesthetics, Intravenous; D000891:Anti-Infective Agents, Local; D004338:Drug Combinations; D013874:Thiopental; D015742:Propofol