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1.
The antibacterial effects of a combination of tiamulin and chlortetracycline in vitro against a number of field isolates of Pasteurella multocida, Haemophilus pleuropneumoniae and Bordetella bronchiseptica were examined. There was a marked synergism between the two antibiotics against all eight isolates of P multocida, against seven of nine isolates of H pleuropneumoniae and against the single strain of B bronchiseptica tested. Two field trials were carried out on a herd with a history of complicated enzootic pneumonia where the presence of Mycoplasma hyopneumoniae and P multocida had been established and subsequently the presence of H pleuropneumoniae was discovered. Feed containing tiamulin at 100 ppm combined with chlortetracycline at 300 ppm was given for seven days to pigs affected with pneumonia, and the results were compared with untreated controls and pigs receiving chlortetracycline at 300 ppm. There was a follow-up observation period of three weeks when all groups received unmedicated feed. During the medication period the combination treated groups showed a statistically significant increase in average daily weight gain of 156 g (20.4 per cent) and in feed conversion efficiency of 0.576 (20.8 per cent) and a numerical improvement in average disease score in comparison with the untreated controls. These improvements were approximately double those observed in the groups treated with 300 ppm chlortetracycline which showed improvements of 93 g (12.2 per cent) in average daily gain and 0.301 (10.9 per cent) in feed conversion efficiency. During the following three weeks most of the initial gains were lost, probably owing to the reinfection of the treated groups by the untreated controls.  相似文献   

2.
The in vitro antimicrobial activities of aditoprim (AP), a new dihydrofolate reductase (DHFR) inhibitor, trimethoprim (TMP), sulfadimethoxine (SDM), sulfamethoxazole (SMX), and combinations of these drugs against some porcine respiratory tract pathogens were determined by use of an agar dilution method. The minimal inhibitory concentrations (MIC) of these agents were determined twice against Bordetella bronchiseptica (n = 10), Pasteurella multocida (n = 10), and Actinobacillus pleuropneumoniae (n = 20) strains isolated from pigs suffering from atrophic rhinitis or pleuropneumonia. All B bronchiseptica strains were resistant to AP and TMP. The MIC50 values of AP and TMP for P multocida were 0.25 and 0.06 microgram/ml, respectively, and for A pleuropneumoniae, 1 and 0.25 microgram/ml, respectively. The MIC50 values of SDM and SMX for B bronchiseptica were 4 and 1 micrograms/ml, respectively; for P multocida, 16 and 8 micrograms/ml, respectively; and for A pleuropneumoniae, 16 and 8 micrograms/ml, respectively. The investigated combinations of the DHFR inhibitors and the selected sulfonamides had synergism for the A pleuropneumoniae strains; the MIC90 values of the combinations were less than or equal to 0.06 microgram/ml. Potentiation was not observed for the B bronchiseptica and the P multocida isolates. The MIC of the combinations against B bronchiseptica and P multocida corresponded respectively to the concentrations of the sulfonamides and the DHFR inhibitors in the combinations. For A pleuropneumoniae, 2 types of strains were used (25% of serotype 2 and 75% of serotype 9). Type-2 strains had lower susceptibility than type-9 strains to AP and TMP as well as to SDM and SMX (at least a fourfold difference in MIC between the 2 types of strains).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
Associations between pathogens in healthy pigs and pigs with pneumonia   总被引：2，自引：0，他引：2  
The aim of this study was to evaluate the associations between different pathogens in the development of pneumonia and bronchopneumonia in pigs. Samples of bronchoalveolar lavage fluid from 100 pigs showing no clinical signs and 239 pigs with clinical signs of respiratory disease were examined for Mycoplasma hyopneumoniae, Mycoplasma hyorhinis, US-type porcine respiratory and reproductive syndrome virus (PRRSV), EU-type PRRSV, porcine circovirus type 2 (pcv-2), influenza virus type A, alpha-haemolytic Streptococcus species, beta-haemolytic Streptococcus species, Pasteurella multocida, Bordetella bronchiseptica, Haemophilus parasuis and Actinobacillus pleuropneumoniae. These potential pathogens were detected more frequently in the pigs with respiratory problems than in the pigs with no clinical signs. pcv-2 and alpha-haemolytic streptococci were the pathogens most frequently detected; A pleuropneumoniae was isolated in only two cases. There were more often associations between the organisms in the pigs with clinical signs than in the healthy pigs. In particular, alpha-haemolytic streptococci and M hyopneumoniae were both associated with the presence of M hyorhinis, EU-type PRRSV, P multocida and B bronchiseptica, and alpha-haemolytic streptococci also occurred more often in pigs that were already infected with other pathogens. P multocida and B bronchiseptica were both significantly associated with M hyopneumoniae, alpha-haemolytic streptococci, EU-type PRRSV and US-type PRRSV.  相似文献   

4.
The minimal inhibitory concentrations (MIC) of five tetracyclines and ten other antimicrobial agents were determined for four porcine bacterial respiratory tract pathogens by the agar dilution method. For the following oxytetracycline-susceptible strains, the MIC50 ranges of the tetracyclines were: P. multocida (n = 17) 0.25-0.5 micrograms/ml; B. bronchiseptica (n = 20) 0.25-1.0 micrograms/ml; H. pleuropneumoniae (n = 20) 0.25-0.5 micrograms/ml; S. suis Type 2 (n = 20) 0.06-0.25 micrograms/ml. For 19 oxytetracycline-resistant P. multocida strains the MIC50 of the tetracyclines varied from 64 micrograms/ml for oxytetracycline to 0.5 micrograms/ml for minocycline. Strikingly, minocycline showed no cross-resistance with oxytetracycline, tetracycline, chlortetracycline and doxycycline in P. multocida and in H. pleuropneumoniae. Moreover, in susceptible strains minocycline showed the highest in vitro activity followed by doxycycline. Low MIC50 values were observed for chloramphenicol, ampicillin, flumequine, ofloxacin and ciprofloxacin against P. multocida and H. pleuropneumoniae. B. bronchiseptica was moderately susceptible or resistant to these compounds. As expected tiamulin, lincomycin, tylosin and spiramycin were not active against H. pleuropneumoniae. Except for flumequine, the MIC50 values of nine antimicrobial agents were low for S. suis Type 2. Six strains of this species showed resistance to the macrolides and lincomycin.  相似文献   

5.
The objective of this study was to compare the detection rate of bacterial agents in bronchoalveolar lavage fluid (BALF), taken without visual control, to that in affected lung tissue obtained from the same pig at necropsy. BALF and affected lung tissue were examined for Mycoplasma hyopneumoniae using PCR, and standard cultural methods were used for Actinobacillus pleuropneumoniae, Bordetella bronchiseptica, Haemophilus parasuis, Pasteurella multocida and Streptococcus suis. All pigs with a history of respiratory symptoms were submitted as live animals for routine diagnostic examination. In each animal the site of lavage, marked by injecting methylene blue, differed from the site of pneumonic lesions. M. hyopneumoniae was detected more frequently in lung tissue than in BALF in cases with moderate or severe lung lesions. The detection rates of M. hyopneumoniae were higher in the BALF of pigs with mild lesions. Cultural examination of BALF was at least as satisfactory as affected lung tissue for detecting B. bronchiseptica, H. parasuis and P. multocida.  相似文献   

6.
The aim of this study was to investigate the incidence and influence of different causative organisms involved in the development of pneumonia and bronchopneumonia in pigs. Bronchoalveolar lavage fluid (BALF) from 339 pigs was examined molecular-biologically and culturally. The evaluation considered the following pathogens: Mycoplasma (M.) hyopneumoniae, Mycoplasma (M.) hyorhinis, PRRSV (US-Type), PRRSV (EU-Type), PCV-2, Influenzavirus Type A, alpha-haemolytic Streptococci, beta-haemolytic Streptococci, Pasteurella (P.) multocida, Bordetella (B.) bronchiseptica, Haemophilus (H.) parasuis and Actinobacillus (A.) pleuropneumoniae. This was followed by a pathological-anatomical examination in 168 pigs. Pathological-anatomical examination was evaluated for possible interstitial pneumonia, catarrhal-purulent bronchopneumonia and pleuritis. alpha-haemolytic Streptococci, PCV-2, H. parasuis, M. hyorhinis, M. hyopneumoniae, B. bronchiseptica, PRRSV (US-Type), P. multocida, PRRSV (EU-Type) and Influenzavirus Type A were evident in descending incidence in the BALF. A. pleuropneumoniae were only isolated culturally in two cases in the BALF. The frequency and semiquantitative detection rate in the bacteriological culture of alpha-haemolytic Steptococci, M. hyopneumoniae, P. multocida and B. bronchiseptica correlated significantly with the ascertained clinical evaluation score and the pathological-anatomical examination score. M. hyorhinis and Influenzavirus Type A only correlated with the severity degree of clinical appearance, while PCV-2 and PRRSV (US-Type) correlated with the frequency of pathological-anatomical changes. The higher the clinical score, the higher was the number of animals ascertained with five or more different pathogens. The more different causal agents were isolated in the BALF of one animal, the higher was the average pathological-anatomical examination score. For the diagnosis of pneumonia, especially when analysing facultative pathogens or secondary pathogens, a useful interpretation of analysis results is only possible in connection with a clinical and pathological evaluation.  相似文献   

7.
In vitro activity of tiamulin against porcine mycoplasmas   总被引：1，自引：0，他引：1  
The activity of tiamulin against Mycoplasma hyopneumoniae, M flocculare, M hyorhinis and M hyosynoviae grown in liquid medium was assessed in vitro. With the first three of these mycoplasmas, the activity of tylosin and oxytetracycline was observed in parallel. Tiamulin was more active against M hyopneumoniae and M flocculare, but there was less disparity between the three antibiotics with the strain of M hyorhinis tested. Tiamulin was notably more active against M hyosynoviae than against M hyopneumoniae. It was more difficult to suppress M hyopneumoniae than the other mycoplasmas with tiamulin. This persistence of M hyopneumoniae was more striking when M hyopneumoniae and M hyosynoviae were tested in parallel.  相似文献   

8.
The in vitro efficacy of tiamulin was compared to that of tylosin against 7 bovine, 7 ovine and 3 caprine mycoplasma strains isolated from various organs and belonging to different species, as well as 7 ureaplasma strains cultured from cattle, sheep, swine, chickens and turkeys. The minimal mycoplasmacidal concentrations of tiamulin varied between 0.01 and 10.0 μg ml?1, while tylosin proved to be active in concentrations of 0.5 and 100.0 μg ml?1. Five of mycoplasma strains showed identical sensitivities to both antibiotics while all other strains, including the ureaplasmas, were sensitive to tiamulin at concentrations 5–5000-times lower than tylosin.  相似文献   

9.
The aim of this study was to compare the in vitro antimicrobial activity of the veterinary fluoroquinolones against a panel of recently isolated porcine and bovine bacterial pathogens. The study used enrofloxacin as a benchmark against which other agents were compared, being the most common fluoroquinolone used in treatment of bovine and porcine infections. The activity of ciprofloxacin was also assessed as it is the main metabolite of enrofloxacin in cattle. Enrofloxacin and ciprofloxacin generally showed higher antibacterial activity, in terms of MIC(50) values, for most pathogen species when compared with marbofloxacin, difloxacin, danofloxacin and norfloxacin. Ciprofloxacin showed significantly greater in vitro antibacterial activity than enrofloxacin against M. haemolytica, P. multocida and E. coli, whereas enrofloxacin showed greater activity than ciprofloxacin against S. aureus. Marbofloxacin was significantly more active than enrofloxacin against M. haemolytica, E. coli and B. bronchiseptica but less active against P. multocida, S. aureus, coagulase negative Staphylococci, S. dysgalactiae, S. uberis, A. pleuropneumoniae and S. suis. Danofloxacin was significantly less active than enrofloxacin against P. multocida, E. coli, S. uberis, A. pleuropneumoniae and S. suis. Enrofloxacin and its metabolite ciprofloxacin showed the highest in vitro activities against most bovine pathogens tested and the porcine pathogens also showed a high degree of sensitivity to enrofloxacin. These data facilitate further pharmacokinetic/pharmacodynamic comparison of fluoroquinolones currently used in veterinary medicine.  相似文献   

10.
A commercial doxycycline formulation was administered in drinking water to 12 pigs at the recommended dose of 10 mg/kg daily for 5 days. The mean plasma concentration at steady-state was 1.37 +/- 1.21 microg/mL, which was reached at 68 +/- 27.2 h postadministration. Absorption and elimination half-life values were 7.20 +/- 2.42 and 7.01 +/- 2.10 h, respectively. Most plasma concentrations during dosing were higher than the minimum inhibitory concentrations (MICs) described for the main porcine bacterial pathogens of the respiratory tract (Pasteurella multocida, Actinobacillus pleuropneumoniae, Bordetella bronchiseptica and Mycoplasma hyopneumoniae). It is concluded that when pigs were treated with doxycycline in drinking water at the recommended rate, therapeutically effective concentrations were achieved throughout the treatment period, supporting the clinical use of this tetracycline in the control of respiratory infections. However, inter-animal differences were marked.  相似文献   

11.
Microorganisms associated with pneumonia in slaughter weight swine.   总被引：2，自引：1，他引：1       下载免费PDF全文
The lungs of 334 pigs were obtained from two slaughter plants in Minnesota and examined in detail. Macroscopic and microscopic evaluation, direct fluorescence for Mycoplasma hyopneumoniae and bacterial culture were done on all of them and a subsample of 50 were selected for virus culture. Mycoplasma hyopneumoniae, Pasteurella multocida and Haemophilus spp. were detected in 24.0%, 34.1% and 27.0% of the lungs, commonly in conjunction with each other. One isolate of Haemophilus pleuropneumoniae serotype 2 was detected and this represents the first report of its presence in the United States. No virus was detected in any of the lungs. Lungs with both M. hyopneumoniae and Pasteurella multocida had the greatest amount of macroscopic pneumonia (9.8% of the lung). Lungs with M. hyopneumoniae or P. multocida alone had 4.9% and 5.2% of the lung involved with pneumonia respectively. Lungs with Haemophilus sp. Taxon "minor group" had 3.8% of the lung involved which was not significantly different from lungs with none of these organisms being detected (1.6%). There was a positive correlation between the extent of M. hyopneumoniae infection, as scored by FAT and the amount of macroscopic pneumonia present (r = 0.46; P less than 0.001). Likewise, there was a positive correlation between the estimated concentration of P. multocida present, as scored by the relative number of colonies on blood agar and the amount of macroscopic pneumonia present (r = 0.60; P less than 0.001). Microscopically, the amount of lymphoreticular proliferation, polymorphonuclear cells and alveolar macrophages were evaluated.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
目的建立可以同时检测猪胸膜肺炎放线杆菌、多杀性巴氏杆菌和副猪嗜血杆菌的快速而可靠的PCR检测方法。方法和结果根据胸膜肺炎放线杆菌的Apx-VIA基因序列、多杀性巴氏杆菌和副猪嗜血杆菌的16SrRNA基因序列设计5条引物。猪胸膜肺炎放线杆菌、多杀性巴氏杆菌和副猪嗜血杆菌模板的PCR扩增产物大小分别为342bp,485bp和1258bp。复合PCR对1～12型猪胸膜肺炎放线杆菌标准株,6株多杀性巴氏杆菌标准株,1～15型副猪嗜血杆菌以及25株经生化鉴定确认为上述三种细菌的分离株的基因组DNA作为模板进行检测,均获得预期大小的扩增产物。以猪放线杆菌、吲哚放线杆菌等14种常见细菌作为阴性对照进行PCR检测,结果仅有支气管败血波氏杆菌产生了可以和上述三个特异性条带明显区分的PCR产物。复合PCR针对胸膜肺炎放线杆菌、多杀性巴氏杆菌和副猪嗜血杆菌的敏感性分别为14pg、34pg和37pg。结论本研究建立的复合PCR特异性好,敏感性高,可以用于猪胸膜肺炎放线杆菌、多杀性巴氏杆菌和副猪嗜血杆菌的快速检测。  相似文献   

13.
The anti-mycoplasma effects of the ionophores (lasalocid sodium, monensin and nigericin) were compared with that of tylosin tartrate and tiamulin in vitro. Forty-four strains representing 14 avian and 10 mammalian Mycoplasma species and serotypes and 5 Acholeplasma species were tested. The ionophores showed average minimal inhibitory concentration (MIC) values between 3.65 and 4.93 micrograms ml-1 for all strains, the MIC values for glucose-fermenting strains were between 2.26 and 3.75 micrograms ml-1, significantly lower than for arginine-hydrolysing strains (9.27-13.12 micrograms ml-1). These values were significantly higher than those obtained with tylosin tartrate (0.45 micrograms ml-1) or tiamulin (0.13 micrograms ml-1). The ionophores were more efficacious against acholeplasmas (0.06-0.25 micrograms ml-1) than against mycoplasmas.  相似文献   

14.
The minimum inhibitory concentrations (MIC) of ciprofloxacin, enrofloxacin, and norfloxacin were tested for approximately ten clinical isolates of each of Actinobacillus pleuropneumoniae, Actinobacillus suis, Actinomyces pyogenes, Corynebacterium pseudotuberculosis, Erysipelothrix rhusiopathiae, Haemophilus parasuis, Haemophilus somnus, Pasteurella haemolytica, Pasteurella multocida, Rhodococcus equi, Streptococcus equi, Streptococcus suis and Streptococcus zooepidemicus. Ciprofloxacin and enrofloxacin had similar activity and were more active than norfloxacin. All isolates had an MIC of 1.0 microgram/mL or less for ciprofloxacin and enrofloxacin, and these drugs had particularly marked activity against the gram-negative bacteria tested.  相似文献   

15.
The 6-chloro analogue of norfloxacin (compound A) administered continuously in the feed at 400 ppm for 21 days markedly reduced the extent and activity of pneumonic lesions in pigs with pneumonia induced experimentally with an homogenate of pneumonic lung and broth cultures of Mycoplasma hyopneumoniae. Norfloxacin at 100 ppm or compound A at 200 ppm in the feed did not reduce the extent of lung lesions, although half the pigs treated with norfloxacin had lesions which appeared histologically to be healing. M hyopneumoniae was detected either by culture or immunofluorescence in the lungs of 60 per cent of the pigs treated with compound A at 400 ppm compared with all the pigs in the other groups. These results were related to the amount of drug in the lungs and body fluids during therapy. Only compound A at 400 ppm produced concentrations in the lungs and bronchial secretions exceeding the minimum inhibitory concentration against M hyopneumoniae. Mycoplasmacidal concentrations were not reached either in the lungs or bronchial secretions which might account partly for the frequent detection of M hyopneumoniae in the lungs after treatment. Drug resistance did not appear to be responsible for the persistence of M hyopneumoniae in vivo since the M hyopneumoniae isolates from the pigs after therapy were sensitive in vitro to both quinolones. As daily weight gain and feed-conversion efficiency improved in all groups of treated pigs compared with the controls, these effects were probably unrelated to the antimycoplasmal activities of the two quinolones.  相似文献   

16.
Mild or subclinical respiratory infections caused by Bordetella bronchiseptica are widespread in pigs despite multiple control efforts. Infection with virulent B. bronchiseptica strains is a common risk factor in the establishment of toxin-producing strains of Pasteurella multocida in the nasal cavity of pigs leading to the disease, atrophic rhinitis (AR). This study was designed to explore the possibility of expressing a protective epitope of P. multocida toxin (PMT) in B. bronchiseptica to create single-component mucosal vaccine to control atrophic rhinitis in pigs. To achieve this, a P. multocida toxin fragment (PMTCE), that was non-toxic and protective against lethal challenge in mice, was cloned into a broad-host-range plasmid, PBBR1MCS2, and introduced into B. bronchiseptica by electroporation. The Pasteurella gene construct was placed under the regulatory control of a promoter region that was separately isolated from B. bronchiseptica and appears to be part of the heat shock protein gene family. B. bronchiseptica harboring the plasmid under antibiotic selection expressed the 80kDa PMTCE as determined by PAGE and Western blot with a PMT-specific monoclonal antibody. When introduced into the respiratory tracts of mice, B. bronchiseptica harboring the plasmid construct was reisolated in declining numbers for 72h post-inoculation. Antibody responses (IgM, IgA and IgG) to B. bronchiseptica were detected in serum and respiratory lavage, but PMTCE-specific antibodies were not detected. While further refinements of PMT expression in B. bronchiseptica are necessary, this study provides a basis for the development of a single-component, live-attenuated vaccine against atrophic rhinitis.  相似文献   

17.
The minimal inhibitory concentrations (MIC) of sulfonamides were determined against Bordetella bronchiseptica (n = 10), Pasteurella multocida (n = 10), Haemophilus pleuropneumoniae (n = 20), and Streptococcus suis (n = 10) strains isolated from pigs with atrophic rhinitis, pneumonia, or meningitis. Sulfonamides tested in an agar dilution method were sulfachloropyridazine, sulfadiazine, sulfadimethoxine, sulfamethazine, sulfadoxine, sulfisoxazole, sulfamerazine, sulfamethoxazole, sulfamethoxypyridazine, sulfanilamide, sulfatroxazole, and sulfisomidine. Results indicated that monotherapy of S suis infections with sulfonamides should not be encouraged because the MIC50 of all sulfonamides investigated was greater than 32 micrograms/ml. The MIC50 of the sulfonamides against B bronchiseptica ranged from 0.5 to 8 micrograms/ml, against P multocida from 2 to 32 micrograms/ml, and against H pleuropneumoniae from 8 to 64 micrograms/ml. The MIC50 of sulfachloropyridazine, sulfadiazine, sulfadimethoxine, sulfamerazine, and sulfamethoxazole for the gram-negative bacteria did not exceed 16 micrograms/ml. Among these compounds, sulfamethoxazole had the highest activity. The frequently prescribed sulfamethazine had an overall low antimicrobial activity.  相似文献   

18.
Three strains of Bordetella bronchiseptica were compared for their ability to assist colonisation of the nasal cavity of gnotobiotic pigs by toxigenic Pasteurella multocida. Toxigenic P multocida (counted in nasal washings) colonised the cavity in large numbers in pigs previously infected with a cytotoxic phase I strain of B bronchiseptica (B58), whereas it colonised only in small numbers in those previously infected with B65, a phenotypic phase III variant of B58. Toxigenic P multocida colonised pigs infected with a non-cytotoxic phase I strain of B bronchiseptica (PV6) in fewer numbers than were seen in pigs infected with the cytotoxic phase I strain but in greater numbers than in pigs infected with the phase III strain. The turbinates of pigs infected with the cytotoxic phase I strain of B bronchiseptica and toxigenic P multocida were most severely affected and those in pigs infected with the non-cytotoxic phase I strain and toxigenic P multocida were moderately reduced in size. The turbinates of pigs infected with the phase III strain and toxigenic P multocida were slightly reduced in size except for one piglet whose turbinates were severely affected. Pigs infected with the non-cytotoxic phase I strain of B bronchiseptica alone showed no signs of atrophy and their turbinates were used to calculate reductions (per cent) in those infected with P multocida. The reduction (per cent) in size of turbinates and total numbers of P multocida isolated from the nasal washings of each pig were linearly related.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

19.
The sensitivity of ten Bordetella bronchiseptica and ten Pasteurella multocida strains, each isolated from cases of atrophic rhinitis (AR), was examined in tube dilution test. Getroxel, chlorquinaldol and oxytetracycline and the former two ones combined with trimethoprim inhibited the growth of both species in vitro. The minimum inhibitory and the minimum bactericidal concentration was less than 0.5 microgram/ml. When efficacy was tested in SPF in the group fed a combination of Getroxel, chlorquinaldol and oxytetracycline (60 mg, 240 mg and 360 mg/kg of feed, respectively), P. multocida disappeared from the nasal cavity by the end of a 30-day treatment. B. bronchiseptica was reisolated in low numbers from 2 out of 9 piglets. The daily body mass gain was by 7.9% higher and the feed conversion rate was by 19% better than in the control group. After slaughter, only mild signs of AR were seen in 3 out of 9 piglets treated with the above-mentioned drug combination, while in the control group severe lesions were observed in 8 out of 9 pigs. In treated commercial herds P. multocida disappeared from the nasal cavity of the piglets by the end of the treatment (42nd day of life), but the B. bronchiseptica strains could not be completely eliminated. Due to the treatment, mortality between 2 and 6 weeks of age decreased by 0.8-7.6%. Daily body mass gain was, on the average, 16.4% higher, the amount of feed needed for 1 kg body mass gain was by 15.3% lower and the duration of fattening was by 30.8 days shorter than in the control groups.  相似文献   

20.
To establish the role of the dermonecrotic toxin (DNT) of Pasteurella multocida in the cause and pathogenesis of atrophic rhinitis, germ-free pigs were inoculated with several strains of P multocida, crude DNT, or purified DNT. In some experiments, the aforementioned inocula were combined with Bordetella bronchiseptica. All DNT-producing P multocida strains induced severe turbinate atrophy. Histologic examination of the remnants of the nasal turbinates revealed intact, but undulated, ciliated epithelium and numerous osteoclasts. Inflammation was minimal or absent. A DNT-producing B bronchiseptica strain induced only mild turbinate atrophy. The lesions were characterized histologically by loss of cilia and ciliated cells and by an infiltration of predominantly mononuclear cells. Bone formation seemed impaired. Turbinate lesions were most severe in pigs infected with a combination of B bronchiseptica and a DNT-producing P multocida strain. Intranasal administration of sterile DNT-containing culture filtrate of P multocida or purified DNT of P multocida did not result in turbinate atrophy. In contrast, turbinate atrophy developed when these preparations were injected IM or when intranasal administration of DNT was preceded by inoculation of B bronchiseptica.  相似文献   

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