[Effect of chlorhexidine gluconate on Serratia marcescens clinical isolates: relevance to serotype O3]

Effect of chlorhexidine gluconate (CHG) on 98 clinical isolates of Serratia marcescens, previously O-serotyped, in The Showa University Fujigaoka Hospital (1989. 1-1991. 3) was investigated. The serotype O3 group (28 strains) was more frequently isolated than any other groups and more resistant to 28 different antimicrobial agents tested. 18 (50%) of 36 strains (MIC of CHG > or = 100 micrograms/ml) were serotype O3 and MIC-distribution of CHG for total O3 strains was more resistant than that for the other serotype strains. Bactericidal effect of CHG on 18 O3 strains (MIC of CHG > or = 100 micrograms/ml) was significantly lower than on the other 10 strains (MIC of CHG < or = 50 micrograms/ml). Although 19 (68%) of total O3 strains were resistant to cefotaxime and the other drugs, MIC-distribution of CHG for these strains was not associated with the antimicrobial resistance tested. The above results, at least, suggest that the serotype O3 group is suited for residing in hospitalized patients more than any other serotype groups.