Naturally acquired turbinate atrophy in rabbits was associated with Pasteurella multocida infection. Several in vitro and in vivo studies were conducted to document toxin production from P. multocida isolates and to determine the relation of toxin to atrophic rhinitis in rabbits. Ten isolates of P. multocida serotype A:12 were obtained from adult New Zealand White rabbits with noninduced atrophic rhinitis. Specific-pathogen-free rabbits inoculated intranasally with isolates of P. multocida developed rhinitis and turbinate atrophy. However, inoculation with filtrates of the same bacteria failed to induce turbinate atrophy. Cytotoxicity was observed in assays, using bovine embryonic turbinate cell cultures with extracts of P. multocida, but not in agar overlay cytotoxicity assays, using bovine embryonic turbinate, bovine embryonic lung, or Vero cell cultures, or in a sandwich ELISA, using monoclonal antibodies to purified P. multocida toxin. Thus, turbinate atrophy was experimentally reproduced in rabbits with isolates of P. multocida, but toxin was only detected in vitro by cell culture assay of P. multocida extracts.

To assess the role of enterotoxigenic (ETEC), verotoxigenic (VTEC), and necrotoxigenic (NTEC) Escherichia coli in cattle with diarrhea, 1,524 colonies of E coli isolated from 197 calves with diarrhea and from 112 healthy controls were investigated for production of heat-labile and heat-stable enterotoxins, verotoxins, and cytotoxic necrotizing factors (CNF1 and CNF2). The ETEC were isolated from only 2 (1%) calves with diarrhea and from 5 (4%) healthy controls. In contrast, VTEC and NTEC that produced CNF2 were frequently identified. The VTEC were isolated from 18 (9%) calves with diarrhea and from 21 (19%) healthy cattle (P < 0.05), whereas NTEC that produced CNF2 were detected in 39 (20%) ill calves and in 38 (34%) controls (P < 0.01). Therefore, VTEC and NTEC that produced CNF2 were isolated significantly more frequently from healthy than diseased calves. Serogroups to which VTEC belonged differed considerably from the O groups involved with NTEC. Although, VTEC belonged to 18 serogroups, only 4 (O26, O103, O113, and O157) accounted for 56% (25 of 45) of verotoxigenic strains. The NTEC that produced CNF2 belonged to 26 serogroups; however, 64% (69 of 108) were from 6 serogroups (O1, O3, O15, O55, O88, and O123). Our results are compatible with cattle being a reservoir of VTEC that are pathogenic for human beings and with ETEC being an unusual cause of bovine colibacillosis in Galicia (northwestern Spain). Furthermore, results of this study indicate that VTEC and NTEC that produced CNF2 may be part of the normal intestinal flora of cattle.

Two hundred ninety-six Eschericbia coli isolates from feces or intestines of calves with diarrhea were hybridized with 7 gene probes. One probe (the eae probe) was derived from the eae gene coding for a protein involved in the effacement of the enterocyte microvilli by the group of bacteria called attaching and effacing E coli (AEEC), and 2 probes were derived from genes coding for the Shiga-like toxins (SLT) 1 and 2 produced by the verocytotoxic E coli (VTEC). The other 4 probes were derived from DNA sequences associated with the adhesive properties of enteroadherent E coli (EAEC) to cultured cells (the EAF probe for the localized adherence pattern, probes F1845 and AIDA-1 for the diffuse adherence pattern, and the Agg probe for the aggregative adherence pattern). Hybridization results for the eae probe were in agreement, for all but 1 of the 8 isolates, with previously published phenotypic results of microvilli effacement. The latter was previously reported as effacing the microvilli of calf enterocytes, but was eae probe-negative. Two classes of isolates hybridized with the eae probe. Members of a first class (60 isolates) additionally produced a positive signal with 1 or both of the SLT probes (VTEC-AEEC isolates). Isolates hy- bridizing with the eae and the SLT1 probes were the most frequent: 56 isolates (ie, 93% of all VTEC-AEEC). Members of the second class (10 isolates) failed to hybridize with either SLT probe (non-VTEC-AEEC isolates). Most isolates of these 2 classes belong to only 4 serogroups: O5, O26, O111, and O118. In addition to these 2 AEEC classes, a VTEC class (20 isolates) was observed. Such isolates were positive with 1 or both SLT probes, but were negative with the eae probe. All but 1 isolate belonged to serogroups not found among the AEEC isolates. Only 7 of all AEEC and VTEC isolates were positive with the EAF, the F1845, or the AIDA-1 probe, and none were positive with the Agg probe. On the other hand, 32 non-VTEC, non-AEEC isolates were positive with the F1845 probe only, 2 were positive with the EAF probe only, and 1 was positive with the AIDA-1 probe only, thus constituting a possible class of EAEC isolates from cattle. The eae gene and the gene coding for the SLT1 are, thus, associated in most AEEC isolates from cattle. The isolates with other hybridization results VTEC and EAEC isolates) need more work to be clearly defined.

Microscopic examination of the nasal mucosa of clinically normal specific-pathogen-free pigs and of toxicogenic type-D Pasteurella multocida toxin challenge-exposed specific-pathogen-free pigs indicated that the surface epithelium in pigs of both groups was microscopically normal; erosions or appreciable inflammatory changes were not evident. In pigs of both groups and in aU 3 regions of the nasal cavity, the endothelial lining of all blood vessels appeared normal without detectable changes to the walls at postinoculation day 10. Vascular injury in the cartilage or the bone was not discernible in control or challenge-exposed pigs. There were marked differences in the osseous structures of the conchae when the 2 groups were compared. In control pigs, active bone formation and remodeling were observed, and the septal cartilage was normal. In toxin challenge-exposed pigs, there likewise was normal bone formation and remodeling in the vestibular region, and the septal cartilage was normal. In marked contrast, conspicuous changes were observed in the osseous core of the conchae of the respiratory and, sometimes, the olfactory regions. These changes consisted of bone necrosis and resorption by large numbers of osteoclasts with variable replacement by dense mesenchymal stroma, which resulted in conchal atrophy. In the absence of any discernible damage or injury (angiopathy) to the nasal vessels, it appears that the action of the dermonecrotoxin of P multocida serotype D is on the most active osteoblasts and the associated organic matrix of the bone, with subsequent disruption of normal bone formation and remodeling of the nasal conchae.

To evaluate the effect of ketoprofen on fecal output during secretory diarrhea, 16 calves were given approximately 200 micrograms of heat-stable Escherichia coli enterotoxin by suckling on 2 occasions. On one day, treatment was not administered. On the other day, either 3 mg of ketoprofen/kg of body weight (n = 8) or 6 mg of ketoprofen/kg (n = 8) was administered 1 hour before and 3 hours after administration of enterotoxin. Fecal output was no different after 8 or 24 hours from calves given 3 mg/kg, but fecal output was less at 8 hours and 24 hours for calves given 6 mg/kg (P = 0.0588), compared with the control day.