RESISTANCE TYPES IN CITROBACTER FREUNDII Occurrence and Resistance to Ampicillin, Carbenicillin, Cephalothin and Mecillinam. Transfer of Ampicillin Resistance

Publisher Website
Google Scholar
Abstract
The resistance types of C. freundii were investigated. The strains were divided into 3 groups according to susceptibility to penicillin derivatives. Group 1, comprising ampicillin-carbenicillin sensitive strains (A-s/Ca-s), constituted 22%; group 2 (ampicillin-resistant (A-r)/Ca-s) constituted 45% and group 3 (A-r/Ca-r), 32%. Two strains (1%) were recorded as A-s/Ca-r. Group 3 contained a higher proportion of multi-resistant strains than groups 1 and 2. The ln of the median inhibitory concentrations with ampicillin, carbenicillin, cephalothin and mecillinam in the tube-dilution method were determined for 32 strains. Groups 1 and 2 differed only as regards cephalothin resistance. The strains of group 3 were more A-r than the group 2 ones. Mecillinam susceptibility did not differ among the 3 groups. No strains in group 2 could transfer A-resistance. In group 3, 10 of 16 strains transferred A-resistance. Resistance to sulfonamide, tetracycline, and streptomycin was also transferred, but with low frequency. The A-r/Ca-r strains could be divided into 2 subgroups, probably reflecting different modes of developing .beta.-lactam resistance. One group was very A- and Ca-r, less cephalothin-r, more mecillinam-r and could transfer A-resistance. The other group had very high cephalothin- and could not transfer A-resistance. C. freundii and Enterobacter cloacae are very similar as regards resistance conditions.