: The present study was conducted to determine the antibiotic susceptibilities of local Mycoplasma hyopneumoniae (Mhp) and Mycoplasma hyorhinis (Mhr) filed isolates. Minimum inhibitory concentrations (MICs) of Mhp and Mhr field isolates (twelve each) obtained from enzootic pneumonia-like lung lesions during 2009-2011 from Korea were determined using the broth microdilution method. Tylvalosin showed the highest activity against Mhp and Mhr field isolates, with MIC 90 values of 0.06 µg/mL and 0.12 µg/mL, respectively. Therefore, Korean Mhp and Mhr isolates are highly susceptible to tylvalosin.Keywords : Mycoplasma hyopneumoniae, Mycoplasma hyorhinis, antimicrobials, minimum inhibitory concentration, porcine enzootic pneumonia Swine mycoplasma Mycoplasma hyopneumoniae (Mhp) and Mycoplasma hyorhinis (Mhr) are respiratory pathogens in pigs. They are associated with enzootic pneumonia (EP) and porcine respiratory disease complex (PRDC) causing huge loses to the porcine industry. Currently commercial vaccines are available only against Mhp; however, their protection ability is not complete [7]. Therefore, use of antimicrobials often becomes necessary to limit the disease in the event of outbreak or as an additional measure to prevent mycoplasma disease. Although considerable data have been obtained on the in vitro antibiotic susceptibility of Mhp and Mhr around the world [6,[8][9][10][11], there are few reports about their susceptibility, and to our knowledge, there is no recent information on antibiotic susceptibility of these mycoplasmas from Korea. In the present study, minimum inhibitory concentrations (MICs) of Korea Mhp and Mhr isolates to tylvalosin and other commonly used antibiotics (tiamulin, lincomycin, tilmicosin and chlortetracycline) was determined.The reference strains used in this study were Mhp (ATCC 25934) and Mhr (ATCC 27717) (American Type Culture Collection, USA). Field isolates (twelve each) of Mhp and Mhr which were obtained from EP-like lung lesions during 2009-2011 were used in this study [1,2]. Each of these isolates was identified by multiplex polymerase chain reaction (mPCR) [3] and passaged 6 times before using in the antimicrobial assay. Both Mycoplasma species were propagated in Friis broth [4] and used at final concentration of approximately 1 × 10 5 CCU/mL. The antimicrobials chlortetracycline, tiamulin and tilmicosin were obtained from Sigma (USA). The lincomycin and tylvalosin were obtained from Dong Bang (Korea) and ECO Animal Health (UK), respectively. The antimicrobials were prepared by binary micro dilution method, in 96-well micro plate (ranging between 64 and 0.0038 µg/mL; SPL Life Sciences, Korea). MICs-were determined using the broth microdilution method as described by Hannan et al. [5]. Readings were taken after incubation of 7 days at 37 o C, and the lowest concentration of antimicrobial inhibiting color change from red to yellow/orange of the medium was defined as MIC of the drug.The results of the in vitro antimicrobial testing for mycoplasma field isolates and t...

The present field trial compared two combined vaccines of porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae, each administered in herd with subclinical PCV2d infection and enzootic pneumonia. One vaccine was a bivalent containing PCV2a and M. hyopneumoniae and the other was a trivalent vaccine containing PCV2a and 2b (PCV2a/b), and M. hyopneumoniae. The defining difference between these two vaccines was the inclusion or absence of PCV2b antigen. A total of 480, 21day-old pigs were randomly allocated to one of four treatment groups (120 pigs per group, male = 60 and female = 60). These groups included; one-dose trivalent-vaccinated, two-dose trivalent-vaccinated, one-dose bivalent-vaccinated, and unvaccinated. The one- and two-dose trivalent vaccinated pigs exhibited significantly better growth performance when compared with those vaccinated with the bivalent vaccine. The one- and two-dose trivalent vaccinated pigs also reduced the amount of PCV2d loads in the blood and feces, and resulted in a lower M. hyopneumoniae load in the larynx when compared with one-dose bivalent vaccinated pigs. Statistical differences were not observed between the one- and two-dose trivalent-vaccinated groups in terms of growth performance, serology, amount of PCV2d loads in the blood and feces, amount of M. hyopneumoniae load in larynx, and pathological lesions. The results of the present study will provide swine practitioners and producer with comparative clinical field data to select the proper vaccine and vaccination regiment for herds suffering from subclinical PCV2d infection and enzootic pneumonia.

Background: This field trial was designed to evaluate the efficacy of a new trivalent vaccine containing porcine circovirus type 2a and 2b (PCV2a/b), and Mycoplasma hyopneumoniae at three independent locations. Methods: Three farms were selected based on their history of PCV2 and M. hyopneumoniae co-infection. Each farm housed a total of 60, 3-day-old pigs that were randomly allocated to one of three treatment groups. Pigs were administered the trivalent vaccine intramuscularly with either a 1.0 ml dose at 3 and 24 days of age or a 2.0 ml dose at 21 days of age in accordance with the manufacturer's recommendations.Results: Clinically, the average daily weight gain of the one-dose and two-dose vaccinated groups within all three farms was significantly higher (p < 0.05) than those of unvaccinated animals during the growing (70-112 days of age), finishing (112-175 days of age) and overall (3-175 days of age) stages of production. One-dose and twodose vaccinated animals elicited neutralizing antibodies and interferon-γ-secreting cells (IFN-γ-SC), which reduced the amount of PCV2 in terms of blood load and reduced the severity of lymphoid lesions when compared with unvaccinated animals. Similarly, one-dose and two-dose vaccinated animals elicited IFN-γ-SC, which reduced the amount of M. hyopneumoniae in terms of laryngeal load and reduced the severity of lung lesions. Conclusions:The intramuscular administration of either one or two doses of trivalent vaccine was not significantly different in any of the evaluated parameters. The results of field trial demonstrated that the trivalent vaccine was efficacious in the protection of swine herds where PCV2d and M. hyopneumoniae were in active circulation.

No abstract