Hemolysin and K antigens in relation to serotype and hemagglutination type of Escherichia coli isolated from extraintestinal infections

Abstract

Escherichia coli isolated from cases of bacteremia and from a variety of urinary tract infections were characterized according to serotype (O:H antigenicity), K type (possession of K1, K2, K3, K12, or K13), hemagglutination (HA) type, and production of beta-hemolysin. Results obtained with the bacteremia and urinary tract infection isolates were similar except for more hemolytic isolates from urine than from blood (42 versus 29%) and more K1+ isolates from blood than from urine (50 versus 29%). A close correlation was found between HA type VI (production of fimbriae which mediate mannose-resistant HA of human and African green monkey erythrocytes) and the production of hemolysin or K1 capsular antigen or both. Most (95 of 98, or 95%) of the HA type VI+ blood isolates and most (146 of 164, or 89%) of the HA type VI+ urine isolates produced hemolysin or K1 or both, in contrast to 22 and 26%, respectively, of those belonging to HA types other than HA type VI. Also, 76% of all hemolytic and 70% of all K1+ isolates belonged to HA type VI. Remarkably few of the HA type VI+ isolates (13%) and even fewer of the HA type VI- isolates (3%) produced both K1 and hemolysin; these belonged mainly to serotypes O16:H6, O18:H7, and O2:H4. Other major serogroups were usually K1+/hemolysin- (O1, O7) or K1-/hemolysin+ (O2, O4, O6). At least 74% (262 of 351) and possibly as many as 83% (293 of 351) of those isolates which produced mannose-resistant HA of human erythrocytes were classified as HA type VI+; 31 isolates produced mannose-resistant HA with all erythrocytes tested. Taking serogroup and serotype into consideration, we conclude that the E. coli fimbrial hemagglutinin(s) responsible for the HA type VI phenotype will prove to be the same as the virulence-associated mannose-resistant adhesins of uropathogenic E. coli which other investigators have characterized as unique fimbrial antigens detectable by mannose-resistant HA of human erythrocytes.