Veterinaria

Research Article

Detection, Isolation and Identification of M. hyorhinis Isolates and Comparison of their Antimicrobial Susceptibility, Immunogenicity and Virulence

Joyce Wanjiru Maingi a#, Qiyan Xiong b#, Yanna Wei b, Qinghong Ma b, Jia Wang b, Maojun Liu b, Zhixin Feng b, Fangfang Bai b, Endong Bao a*, Guoqing Shao a*

a College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210014, China

b National Center for Engineering Research on Veterinary Bio-products, Nanjing 210014, PR China

Abstract

Mycoplasma hyorhinis (M. hyorhinis) field strains were isolated from the lungs of pig with pneumonic lesions, collected from Chinese slaughterhouses. The samples were designated as 11051207, 10090701, 11081111, 10072902, 100928, 11022402, 11042105 and 10071603 and subjected to antimicrobial susceptibility testing (AST) against 12 antimicrobial agents using broth micro dilution technique. Most of the M. hyorhinis strains were found to be sensitive to macrolide, norfloxacin and tetracycline. Tiamulin was found to have the highest activity with a minimum inhibitory concentration (MIC) of less than 0.06 for all the strains. However, strain 10090701 and 11042105 were not susceptible to gentamicin and kanamycin monosulfate (MIC>32). The level of IgG in the serum of vaccinated mice was quantified by an indirect enzyme linked immunosorbent assay (ELISA) to detect the strain with highest antigenicity. The strains 10090701, 100928, 11081111 and 10072902, especially the strain 10090701, induced higher titer of IgG antibodies than the others. The ability to induce mortality in chicken embryos after experimental inoculation with pure cultures of M. hyorhinis was done to determine the most virulent isolate. The most virulent strain was observed to be 11051207 that caused 100% mortality followed by 100928 and 11081111. The most immunogenic and virulent strains would subsequently be used in future studies on vaccine development and to inoculate swine and assess their ability to achieve M. hyorhinis-induced pathogenesis.

Keywords: Mycoplasma hyorhinis; Isolation; Antimicrobial susceptibility; Immunogenicity; Virulence.

Received: June 05, 2013; Revised: August 12, 2013; Accepted: September 04, 2013

*Corresponding authors: Endong Bao; Email: b_endong@hotmail.com; Guoqing Shao; Email: gqshaojaas@gmail.com

#These authors contributed equally