Pharmacokinetics of amoxicillin administered in drinking water to recently weaned 3- to 4-week-old pigs with diarrhea experimentally induced by Escherichia coli O149:F4.

OBJECTIVE: To measure effects of Escherichia coli O149:F4-induced diarrhea on water consumption and pharmacokinetics of amoxicillin after administration in drinking water. ANIMALS: 24 recently weaned 24- to 28-day-old crossbred pigs. PROCEDURE: 10 pigs were inoculated with E. coli O149:F4; all 10 pigs subsequently developed diarrhea. Pigs were medicated by administration of amoxicillin in the drinking water (0.75 mg/mL) for a 4-hour period on 2 consecutive days. Fourteen age-matched noninfected healthy pigs (control group) were medicated in a similar manner. Blood samples were obtained from both groups daily, and plasma concentrations of amoxicillin were analyzed by use of high-performance liquid chromatography. RESULTS: Diarrhea reduced the area under the plasma concentration-versus-time curve (AUC) and maximum plasma concentration (C(max)) of amoxicillin on the first day of medication by 56% and 63%, respectively. The AUC of amoxicillin on the second day of medication for diarrheic pigs did not differ significantly from that of control pigs on the first day of medication. CONCLUSIONS AND CLINICAL RELEVANCE: E. coli-induced diarrhea reduced the AUC of amoxicillin and time that plasma concentration of amoxicillin was > 0.025 microg/mL and, hence, less likely to have a therapeutic effect on the first day of administration in drinking water. On the assumption that plasma concentrations may indirectly reflect concentrations at the site of infection, analysis of our results suggests that higher doses of amoxicillin may be appropriate for administration in drinking water during a 4-hour period on the first day that pigs have diarrhea attributable to E. coli O149:F4.

Experimental infection with Escherichia coli O149:F4ac in weaned piglets.

The outcome of experimental intestinal infections with enterotoxigenic Escherichia coli (ETEC) is dependent on several factors. An important factor is adhesion of the challenge strain to the intestinal mucosa. The test for susceptibility towards ETEC adhesion has so far been made by an intestinal adhesion test made after slaughter of piglets. However, in an experimental infection study with the purpose to obtain diarrhoeic piglets, it would be an advantage to test for susceptibility prior to experimentation. The Mucin 4 gene on porcine chromosome 13 has been proposed as a candidate gene for the production of the specific ETEC F4ab/ac receptor, and a DNA marker-based test has been developed to allow genotyping for ETEC F4ab/ac resistance/susceptibility [Jørgensen, C.B., Cirera, S., Archibald, A.L., Anderson, L., Fredholm, M., Edfors-Lilja, I., 2004. Porcine polymorphisms and methods for detecting them. International application published under the patent cooperation treaty (PCT). PCT/DK2003/000807 or WO2004/048606-A2]. The aim of this study was to test an experimental model for ETEC O149:F4ac-induced diarrhoea in piglets, selected for susceptibility towards ETEC O149:F4ac adhesion prior to experimentation using a DNA marker-based test. Sixty-two healthy 25-32 days old recently weaned Danish crossbred piglets were used. All piglets were tested prior to experimentation for susceptibility or resistance towards ETEC O149:F4ac adhesion. Thirty-nine piglets, both susceptible and resistant, were oro-gastric intubated with 10(9)CFU of ETEC O149:F4ac and 23 age-matched piglets, both susceptible and resistant, were used as non-infected controls. Of susceptible piglets, challenged with ETEC O149:F4ac, 74% had ETEC O149:F4ac-associated diarrhoea first day after first challenge, which were significantly higher relatively to the resistant and challenged piglets where 20% had diarrhoea (p=0.04). This study suggests a model for experimental ETEC induced diarrhoea.

Pharmacokinetics of amoxicillin after oral administration in recently weaned piglets with experimentally induced Escherichia coli subtype O149:F4 diarrhea.

OBJECTIVE: To measure the effect of Escherichia coli subtype O149:F4-induced diarrhea on the pharmacokinetics of orally administered amoxicillin in affected piglets relative to that of uninfected piglets. ANIMALS: 22 healthy 4-week-old recently weaned Danish crossbred piglets. PROCEDURE: 12 piglets were orally inoculated through gastric intubation with 10(9) CFUs of an E. coli O149:F4 strain and responded by developing diarrhea 12 to 16 hours later. Piglets were dosed with amoxicillin trihydrate solution (20 mg/kg) by gastric intubation. A control group of 10 age-matched piglets without signs of diarrhea was dosed similarly. Blood samples were obtained before amoxicillin administration and at 0.5, 1, 1.5, 2, 3, 6, 12, and 24 hours after amoxicillin administration. The plasma concentration of amoxicillin was analyzed by high-performance liquid chromatography. RESULTS: A significant 39% decrease in the area under the plasma concentration versus time curve of amoxicillin was observed in piglets with diarrhea relative to that of control piglets. The maximum plasma concentration (Cmax) was significantly (52%) lower in piglets with diarrhea, compared with control piglets, while the elimination rate constant, time to reach Cmax, and elimination half-life were unchanged. CONCLUSIONS AND CLINICAL RELEVANCE: Escherichia coli-induced diarrhea may decrease systemic bioavailability of amoxicillin. Escherichia coli bacteria attach to the intestinal epithelial cells. Because it is assumed that the concentration of the antimicrobial at the site of infection reflects the systemic concentration, higher doses of amoxicillin in the treatment of piglets with E. coli O149:F4-induced diarrhea may be appropriate.

Association between the porcine Escherichia coli F18 receptor genotype and phenotype and susceptibility to colonisation and postweaning diarrhoea caused by E. coli O138:F18.

Porcine postweaning Escherichia coli enteritis is a cause of significant morbidity and mortality in pigs worldwide, and effective prevention remains an unsolved problem. This study examined the correlation between susceptibility of pigs to experimental infection with an E. coli F18 strain and the porcine intestinal F18 receptor genotypes. Thirty-one pigs classified as either belonging to the susceptible or the resistant genotype were inoculated with cultures of an E. coli O138:F18 isolated from a pig with postweaning diarrhoea. Susceptibility to colonisation and diarrhoea was assessed by clinical observations, faecal shedding of the challenge strain, histopathology and microscopic adhesion tests. Ten of 14 (71.4%) genetically susceptible pigs and one of 17 (5.9%) resistant pigs developed diarrhoea attributable to the challenge strain. There was no difference in susceptibility between homozygotic and heterozygotic susceptible pigs. Faecal shedding of the challenge strain correlated with the genetic receptor profile. Twenty pigs examined immunohistochemically revealed focal to extensive small intestinal mucosal colonisation by E. coli O138:F18 in nine of 10 susceptible and three of 10 resistant pigs. Results of in vitro adhesion assays performed with F18 cells on enterocyte preparations from 24 pigs, showed complete concordance with the F18 genotypes. In conclusion, this study showed a high correlation between the porcine intestinal F18 receptor genotypes and susceptibility to disease. However, pigs of the resistant F18 receptor genotype were not entirely protected against intestinal colonisation by E. coli F18.

Prevalence of serogroups and virulence genes in Escherichia coli associated with postweaning diarrhoea and edema disease in pigs and a comparison of diagnostic approaches.

Identification of Escherichia coli causing porcine postweaning diarrhoea (PWD) or edema disease (ED) requires knowledge regarding the prevalent pathotypes within a given region. This study was undertaken to determine the present distribution of serogroups, hemolytic activity and virulence factor gene profiles among porcine pathogenic E. coli isolates in Denmark and to compare detection of these characteristics as diagnostic approaches. Five hundred and sixty-three E. coli were serogrouped using E. coli O-antisera and investigated for hemolytic activity. Of these, 219 isolates were further characterized using a 5'-nuclease PCR assay detecting genes for adhesion factors, enterotoxins and verocytotoxin 2e (VT2e). Forty-two different serogroups were found. The most prevalent serogroup was O149 accounting for 49.9% of all isolates, followed by O138 (14.9%), O139 (6.9%), O141 (4.1%) and O8 (3.7%). Hemolytic activity was detected in 87.7% of all isolates. Virulence factor genes detected were F4 (44.7%), F18 (39.3%), intimin (1.4%), F6 (0.9%), STb (77.6%), EAST1 (65.8%), LT (61.6%), STa (26.5%) and VT2e (16.4%). Six pathotypes accounted for 65.7% of all isolates investigated. Using possession of virulence factor genes as reference, O-serogrouping employing a selection of antisera representing common pig pathogenic serogroups and detection of hemolysis were evaluated as epidemiological markers for pathogenicity. Both criteria were associated with pathogenicity (P<0.001, for both), however, both methods also resulted in false classifications regarding pathogenicity for 11.9 and 13.2% of isolates, respectively. Detection of adhesion factor genes F4, F18 and intimin is suggested as an operational alternative when diagnosing PWD and ED.