title: The importance of the K1 capsule in invasive infections caused by Escherichia coli.
abstract: We examined 534 clinical isolates of Escherichia coli for sensitivity to rough lipopolysaccharide-specific and K1-specific phages. Twenty-eight percent of bacteremic isolates were sensitive to rough-specific phages. Forty-two percent of these strains, against only 20% of bacteremic isolates insensitive to rough-specific phages, had K1 capsule (P less than 0.001). K1-positive strains were usually resistant to phagocytic killing, whereas strains lacking the K1 capsule were more likely to be killed regardless of capsular type. Eighty-two percent of strains were typable with O-specific, 57% with K-specific, and 74% with H-specific antisera. Sixty percent of E coli were agglutinated by only 10 O-specific antisera. K1 was the most common capsular type, followed by K5, K2, and K12, whereas four H antigens accounted for nearly half of the H-typable strains. We conclude that (1) the combination of rough-specific and K1-specific phage sensitivity defines functionally similar groups of bacteria and (2) a polyvalent vaccine against invasive E coli is possible given the relatively limited number of invasive O:K:H serotypes.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000942:Antigens, Bacterial / Q000032:analysis; D016667:Bacterial Capsules; D001434:Bacteriophage Typing; D001770:Blood Bactericidal Activity; D002555:Cerebrospinal Fluid / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000145:classification; D004927:Escherichia coli Infections / Q000382:microbiology*; D005243:Feces / Q000382:microbiology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008070:Lipopolysaccharides / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D019081:O Antigens; D010587:Phagocytosis; D011135:Polysaccharides, Bacterial / Q000032:analysis*; D018805:Sepsis / Q000382:microbiology; D012703:Serotyping; D014552:Urinary Tract Infections / Q000382:microbiology; D014947:Wounds and Injuries / Q000382:microbiology
chemical_list: D000942:Antigens, Bacterial; D008070:Lipopolysaccharides; D019081:O Antigens; D011135:Polysaccharides, Bacterial; C036962:capsular polysaccharide K1