Cefoxitin sodium activity against anaerobes: effect of the inoculum size, pH variation and different culture media

Abstract

The effect of four different culture media, three different pH and three inoculum densities on the in vitro activity of cefoxitin against 28 anaerobe isolates was investigated. Use of Brucella agar, brain heart infusion agar, tryptic soy agar or Mueller-Hinton agar yielded cefoxitin values for Bacteroides and Clostridium which were all within a twofold dilution regardless of the medium used. There was no significant influence of the initial pH of the medium on the activity of cefoxitin sodium. Changes of pH between 6 and 8 caused variations no greater than one dilution. No significant changes were observed in cefoxitin MICs with variations in inoculum densities between 10 ² and 10 ⁷ .