Porcine enteropathogenic Escherichia coli strains possessing or lacking K88 antigen were studied by using hydrophobic interaction chromatography on crosslinked agarose gels with alkyl or aryl substituents (amphiphilic gels) to determine whether or not they possessed surface-associated hydrophobic properties. Strains with K88ab or K88ac antigen adsorbed to phenyl and octyl Sepharose gels in the presence of 4 M sodium chloride. This property correlated with phenotypic expression of K88 antigen. Cells grown at 37°C but not those grown at 18°C possessed hydrophobic adsorptive characteristics in addition to the property of mannose-resistant hemagglutination of guinea pig erythrocytes. Adsorption of K88-positive strains to gels with hydrophobic ligands was independent of 0 group and enterotoxicity. Strains lacking K88 antigen did not adsorb to the hydrophobically substituted derivatives of Sepharose and lacked mannose-resistant hemagglutinating characteristics. Neither the presence of additional polysaccharide K antigens nor nonhemagglutinating pili conferred the property of hydrophobic interaction on the strains. K88-positive bacteria had a lower electrophoretic migration rate than did K88-negative bacteria of the same serotype in free-zone electrophoresis. K88-positive bacteria also adsorbed strongly to hydrophobic ligands in the presence of 1 M ammonium sulfate, whereas K88-negative strains did not. These observations provide evidence for the suspected role of hydrophobic interaction in the adhesive properties of certain enteropathogenic strains of E. coli. Moreover, hydrophobic interaction chromatography provides convenient and rapid alternative means of screening strains for a property potentially associated with adhesiveness.

. 1997. We used the Phene Plate generalized microplates to investigate the metabolic activities of faecal flora of pigs during pre-and post-weaning periods. Weekly samples were collected from four sows and their litters (four piglets from each) during 5 months. The metabolic fingerprints obtained from faecal floras of sows and their litters in the first sampling occasion was very similar, suggesting that sows were the initial source of flora for piglets. This similarity, however, was lost in week 2 and piglets developed new types of flora which, although similar among the litter-mates, differed from those of the sows. The metabolic fingerprints of pigs' floras during the post-weaning period also differed from those of the suckling period. On day 70 pigs were transferred to a fattening stable. The faecal flora of the animals during this period was unstable in each individual and differed among litter-mates. A pattern of successive changes was observed in the fermentative capacity (FC) of pigs' floras reaching the highest value before weaning (day 34). An overall decrease in the FC value of faecal floras was observed as a consequence of dietary shifts from milk to solid food to high energy fattening diet. The mean FC value of pig floras on the first sampling occasion (mean 2 S.D. 0·41 2 0·02) was significantly higher than that obtained in the last sampling occasion (day 145) (0·31 2 0·04) (P ³ 0·001). Faecal floras of sows also had lower FC values (0·25 2 0·01) than those of piglets suggesting that loss of FC by the faecal flora of young pigs will continue as they age.

Parenteral vaccination of sows against Escherichia coli diarrhea in their newborn piglets has become more common during the last decade in Sweden, and the vaccination has generally had positive effects. For more than 20 years we have investigated E. coli strains isolated from piglets and wegned pigs with enteric disorders, noting the presence of 0 groups, enterotoxins, and adhesins. There has been a continuous change in`the frequency of these virulence factors. The present study was performed during 1983 and 1984 to follow this change, since such information is essential for the proper choice of vaccines. A total of 856 E. coli strains were obtained from 683 herds divided into three age groups: 1 to 6 days old, 1 to 6 weeks old, and weaned pigs. 0 group 149 still dominated in the last two age groups, while 0 group 101 was, for the first time, the most frequent 0 group in neonatal piglets. AU but four 0149 strains carried the K88 antigen, which was found in only one other strain (0 group 8). K99 antigen was most often found in 0 groups 101 and 64, and among all the K99 strains ST mouse was the most common (44 of 57), followed by ST mouse-ST pig strains (12 of 57). The 987P antigen was demonstrated in 26 strains belonging to 0 groups 141 and OX46 and nontypable strains. Two strains belonging to 0 group 101 were positive for F41 antigen; one of them also carried the K99 antigen. Among ail non-0149 strains, ST mouse was the most common type of enterotoxigenic E. coli (n = 88), followed in decreasing order by ST mouse-ST pig strains (n = 69) and ST pig strains (n = 33). In 114 strains producing enterotoxins no adhesive factor was found. Thus, vaccination of the Swedish sow population for more than 5 years with vaccines containing 0149 and K88 antigens has apparently changed the pattern of enterotoxigenic E. coli in neonatal diarrhea. The frequency of 0149:K88 strains has been reduced, and 0101:K99:ST mouse strains now dominate. However, 0149 strains remain the dominant 0 group in piglets older than 1 'week. In spite of all our diagnostic efforts, no virulence factors were detected in about one third of the piglets and weaned pigs with enteric disorders.

A highly discriminatory and standardized biochemical fingerprinting method was used to monitor the persistence and colonization of intestinal Escherichia coli isolated from the feces of four sows and their litters (four piglets from each) during the suckling, postweaning, and fattening periods. Altogether, 195 fecal samples were collected and 1,827 E. coli strains were tested (mean number of isolates tested per fecal sample per pig, 9.5). Strains were divided into similarity groups on the basis of their biochemical phenotypes (BPTs). The diversity of E. coli strains in each sample was measured with Simpson's index of diversity, and similarity between E. coli floras of piglets was calculated with a population similarity index. Each fecal sample contained several BPTs of E. coli, some of which dominated that population. The intestinal colonization of piglets consisted of successive waves of different E. coli BPTs, the tenure of which varied from a few days to 2 weeks. Most of these BPTs disappeared in the succeeding samples and were not recovered again from the same piglets. On the other hand, some E. coli strains which colonized piglets early during the suckling period persisted for a long period and were referred to as resident BPTs. Each piglet carried more than one resident BPT (mean of 2.4 BPTs per pig), some of which were also found in other piglets. This finding indicates that both strain and host specificity are important for colonization and persistence of E. coli in pigs. During the first week of life, E. coli floras of piglets were quite different from those of their dams, suggesting that the dominant E. coli strains in piglets might be quite different from those of their sow. Despite the similarity in E. coli floras between littermates during suckling, each piglet developed a unique flora during postweaning and fattening periods. Pigs which were kept together in one litter until the end of the study had E. coli floras more similar to each other than those mixed with other pigs.

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