The prevalence of F107 fimbriae and their association with Shiga-like toxin II in Escherichia coli strains from weaned Australian pigs.

A total of 480 haemolytic Escherichia coli (HEC) strains from weaned pigs were tested using an oligonucleotide probe to determine the prevalence of F107 fimbriae in Australia. Of these, 62% were positive. F107 was detected in serogroups O141, O138, O8, O45, O139, O157 and O98 but not in O149 nor O147. 81% of E. coli strains not producing other fimbriae (K88, 987P, K99 or F41) were positive for F107; 5% of strains with K88 fimbriae also had F107. Serological investigation of the expression of F107 fimbriae indicated that serogroups O141, O138, O8, O45 and O157 produced variant F107ac. Variant F107ab was found on O139 strains only. The F107 fimbrial subunits of both variants had a molecular weight of approximately 16 kDa. A total of 350 of the HEC strains were tested to determine the prevalence of the Shiga-like toxin II (SLT II) gene. 29.0% of these strains were positive. SLT II was detected in serogroups O141, O138, O149, O98, O45, O8 and O157 but not in O139. 25% of these strains were positive for both F107 and SLT II.

Prevalence of enteroviral and parvoviral antibodies in pig sera.

Surveys of serum antibodies to enterovirus serotype 8 and parvovirus were conducted in pigs three to 21 weeks old using the virus neutralisation (VN), enzyme-linked immunosorbent assay (ELISA) and haemagglutination inhibition tests. Antibody levels to enterovirus were at their lowest at four to eight weeks old, increased at 14 to 16 weeks to high levels which were maintained until 21 weeks. Specific immunoglobulin G (IgG) values measured by ELISA paralleled VN values and were similar in two separate farm surveys. Measurement of immunoglobulin M (IgM) levels indicated that enterovirus infection occurred about four weeks old. Sera obtained from a large number of geographically separated farms, from abattoir-bled animals and from colostrum-deprived piglets raised for 33 weeks from birth in an isolated environment were tested by VN. Results revealed that porcine enterovirus serotype 8 is spread widely throughout northern Victorian piggeries and high antibody levels prevail. In contrast to the enterovirus antibody results, parvovirus antibody levels measured in piglets declined from high levels at three to four weeks to undetectable levels from 13 weeks old.

The characterisation and pathogenicity of porcine enteroviruses isolated in Victoria.

Approximately 23 viruses were isolated from healthy pigs, pigs with encephalitis, and in cases of reproductive failure. Five viruses were identified as enteroviruses and a total of 10 isolates were shown to cross-react serologically to varying degrees. Twenty viruses were neutralised by a reference antiserum of serotype 8 porcine enterovirus. Intracerebral inoculaton of colostrum-deprived piglets with 2 of the characterised viruses caused lesions of encephalomyelitis which were not induced by oral infection. Intrafoetal inoculation of 2 sows with one characterised faecal isolate caused foetal death and abortion, but no adverse effects followed oral dosage.

Atypical porcine enterovirus encephalomyelitis: possible interraction between enteroviruses and arsenicals.

Porcine enteroviruses were isolated from weaner pigs that had nervous signs and mild non-suppurative meningoencephalomyelitis and ganglioneuritis. The clinical signs and lesions were not typical of enterovirus infection and it is believed that an organic arsenical present in feed enhanced pathogenicity of enteroviruses. Severe non-suppurative polioencephalomyelitis and ganglioneuritis were produced in gnotobiotic pigs by oral inoculation of the viruses.

Genetic analysis of Escherichia coli from porcine postweaning diarrhoea.

A total of 79 Australian isolates of beta-haemolytic Escherichia coli from cases of porcine postweaning diarrhoea (PWD), and 18 isolates of serotype O 149:K91:K88 (F4) from unweaned pigs from Australia, Indonesia and Denmark, were examined by multilocus enzyme electrophoresis. These were divided into 57 electrophoretic types (ETs), with an overall mean genetic diversity per enzyme locus of 0.466. This value closely resembled that previously recorded for the whole species. Not only was the collection diverse, but there was considerable genetic heterogeneity amongst PWD isolates of the same serogroup. Isolates from serogroups O 8 and O 138 were most varied, whilst many from serogroups O 141 and O 149 were more closely related. In contrast, the isolates from the unweaned pigs all belonged to only one ET.

Clonal analysis of Escherichia coli of serogroups O9, O20, and O101 isolated from Australian pigs with neonatal diarrhea.

The genetic diversity of 87 isolates of Escherichia coli recovered from Australian pigs with neonatal diarrhea was examined by multilocus enzyme electrophoresis. The isolates were of serogroups O9, O20, and O101, and although most isolates lacked K88(F4), K99(F5), 987P(F6), and F41 fimbriae, they were considered to be involved in the etiology of the diarrhea. The isolates were extremely diverse, considering their origin from a single pathological condition in one country. There were estimated to be 18, 16, and 12 clones of the three respective serogroups in the collection, with serogroup diversities of 0.387, 0.448, and 0.275, respectively. Comparison with the results previously obtained for isolates from piglets with postweaning diarrhea suggested that bacteria from piglets with these two conditions did not come from any particular common genetic background. The overall genetic diversity for the combined collection was the same as that reported by others for representative isolates selected from throughout the species (0.47). The current results indicate that if isolates of these O groups are involved in porcine diarrhea, their pathogenicity is directly linked to their O somatic antigen type and is not simply due to the wide distribution of a small number of virulent clones.