FREQUENCIES OF LIPOPOLYSACCHARIDE CORE TYPES IN ESCHERICHIA-COLI STRAINS FROM BACTEREMIC PATIENTS

We have investigated the distribution of the various core types (R1, R 2, R3, R4 and K-12) in 138 Escherichia coli isolates obtained from pos itive blood cultures. Rabbit antisera, raised against five rough strai ns expressing the respective core types, were made monospecific by ext ensive absorption. The reactivity of the antisera was tested in ELISA with bacterial cells that had been autoclaved for full exposure of cor e epitopes. One hundred and thirty strains could be typed directly, wh ile eight strains required prior digestion with proteinase K for remov al of cross-reactions. Ninety-four of the strains (68%) expressed the R1 type, and 9 (6.5%), 12 (8.7%), 7 (5.1%) and 3 (2.2%) strains expres sed the R2, R3, R4 and K-12 core types, respectively. An R1R4 mixed co re type, hitherto not yet described, was found in 13 (9.4%) strains. R esults obtained with polyclonal antisera were in agreement with those obtained with monoclonal antibodies to the R1, R2 and R3 core types. C ore typing may serve as an additional serological marker next to conve ntional typing of O-, H- and K-antigens.