[O-serotypes, biotypes and antimicrobial susceptibilities of Serratia marcescens isolates from clinical specimens: 4th report].

The clinical isolates of Serratia marcescens in The Showa University Fujigaoka Hospital in the period V during the 3 years from 1991 April to 1994 March were epidemiologically investigated by determining O-antigens, biotypes and antimicrobial susceptibilities. The isolates were collected, while the consumption of beta-lactam antibiotics, new quinolones, and aminoglycosides in the hospital had not changed significantly since 1991. The urease positive O3 strains were predominantly isolated in the period II to IV during the 9 years and 3 months from 1982 January to 1991 April and were more resistant to third generation cephalosporins and the other drugs such as new quinolones and aminoglycosides than the other O-serotype strains. However, the urease negative O14 strains, unlike such O3 strains, were predominantly isolated in the period V and were more resistant to the above mentioned drugs than the other O-serotype strains, indicating that they had higher resistance rates for carbenicillin, latamoxef, ceftizoxime, cefoperazone, cefpirome, tobramycin, dibekacin, gentamicin and fosfomycin than the O3 strains in the period IV during the two years and three months from 1989 January to 1991 March. The hospital wards in which the O14 strains were mainly isolated were the departments of urology, general surgery, orthopedic surgery, haematology, and internal secretion and kidney medicines, corresponding to those in which the isolation number of the O3 strains decreased in the period V. These findings suggest that S. marcescens resident in the hospital inherits multiple drug resistance by changing the biotype and O-serotype.