Antimicrobial Susceptibility of Pasteurella Multocida Type D from Missouri Swine

Abstract

Atrophic rhinitis (AR) is a significant disease and management problem to swine producers worldwide. 1,9 For some time, Bordetella bronchiseptica was considered to be the primary etiologic agent of AR. 7,10 However, current evidence indicates that toxigenic strains of Pasteurella multocida type D may also play a role in this disease process. 1,9 Pasteurella multocida type D is a fastidious microorganism, and often, when taken from turbinates, it will not initially grow on standard blood agar (trypticase soy with 5% defibrinated sheep blood), a thus requiring mouse inoculation to recover the isolate. Because Bordetella bronchiseptica is readily recovered from swine with AR and P. multocida is not, the role of P. multocida has not been fully appreciated.The use of a selective medium 2 has greatly enhanced the recovery of P. multocida type D from nasal turbinates without the necessity of mouse inoculation.The purpose of this paper is to report the antimicrobial susceptibility of P. multocida type D from Missouri swine as determined by a microdilution test procedure+ Pasteurella multocida type D was isolated from the nasal turbinates of pigs referred to the University of Missouri Veterinary Medical Diagnostic Laboratory from November 1986 to April 1988. Samples were obtained aseptically from affected portions of the turbinates after sectioning of the snouts. Swabs were inoculated to SBA (trypticase soy agar-5% defribrinated sheep blood) a MacConkey agar (supplemented with 1% dextrose) b and a selective Columbia Blood Inhibitory agar. 2 Briefly, the medium was prepared with Columbia blood agar base supplemented with 5% defibrinated sheep blood, and it contained a final concentration of 2 µg/ml neomycin and 3.5 µg/ ml of bacitracin. a,c,d The plates were streaked for isolation and incubated aerobically at 35 C for 24-48 hours. Bacterial growth was identified by standard methods. 3 Pasteurella multocida type D was determined by cross-streaking the subcultured isolate on fresh trypticase soy blood agar with Staphylococcus aureus and observing for the presence or absence of capsule formation. Isolates resistant to hyaluronidase activity of the S. aureus were classified as P. multocida type D. 4 Microdilution antimicrobial susceptibility testing was accomplished using Ca++-and Mg++-supplemented Mueller-Hinton (MH) broth and a 96-well customized Sensititre microdilution tray. e 5 The antimicrobial agents and concentration ranges (&ml) are listed as follows: ampicillin 0.25-32, trimethoprim/sulfamethoxazole 0.25/4.75-32/608, cephalothin 0.5-64, penicillin 0.125-l6, spectinomycin 0.75-96, sulfachlorpyridazine 12.5-400, sulfadimethoxine 12.5-400, oxytetracycline 0.25-32, tylosin 0.31-40, erythromycin 0.125-16, gentamicin 0.25-16, and kanamycin 0.5-32.Several colonies of P. multocida were picked to trypticase soy broth a and incubated at 35 C to achieve a nephelometer reading (API standardized reader) f of 0.5 (McFarland scale). A 10-µ1 inoculum was then transferred to 10 ml of Ca++ Mg++ supplemented MH broth and mixed. e An au...

Comparison of MICs of ceftiofur and other antimicrobial agents against bacterial pathogens of swine from the United States, Canada, and Denmark

“…Ampicillin demonstrated excellent activity against P. multocida, ␤-hemolytic streptococci, and S. suis (MIC 90 s, Յ0.03, Յ0.03, and 0.13 g/ml, respec-tively) and moderate activity against S. typhimurium (MIC 90 s, 2.0 g/ml). These results are in agreement with previously reported MICs (10,33,34). Fales et al (10) found the MIC 90 of ampicillin to be Յ0.25 g/ml for P. multocida.…”

“…These results are in agreement with previously reported MICs (10,33,34). Fales et al (10) found the MIC 90 of ampicillin to be Յ0.25 g/ml for P. multocida. Turgeon et al (34,35) found that Ն90% of strains of S. suis were inhibited by 0.12 g of ampicillin per ml.…”

“…Some minimal activity was observed against P. multocida strains from the United States when they were assessed separately (MIC 90 s, 256.0 g/ml). These results agree with those from previous reports with sulfonamides against swine pathogens (8)(9)(10)16). While sulfamethazine was found to be inactive against most of the strains tested, the potentiated sulfonamide tested was found to have good activity against most of the strains tested.…”

Pleuropneumonia in Missouri Swine

“…24 Lung of each specimen was cultured for P. multocida, A. pleuropneumoniae, and S. cholerae-suis as previously described. 3,[5][6][7]23 Lung was cultured for Mycoplasma spp. as previously described in specimens with typical gross lesions.…”

“…This may be especially true of those swine that had received antibiotics, because there are differences in the antimicrobial susceptibility patterns of these bacteria. [5][6][7] The isolation and identification of A. pleuropneumoniae requires special bacteriologic media and techniques. 3,22 Actinobacillus pleuropneumoniae has been isolated by dilution techniques from Table 2.…”