In vitro antibiotic susceptibility of field isolates of Mycoplasma synoviae in Argentina.

Minimum inhibitory concentrations (MICs) were determined in vitro for 7 antibiotics (aivlosin, enrofloxacine, tylosin, tiamulin, kitasamycin, chlortetracycline, and oxytetracycline) against eight recent local Argentinean isolates and two standard strains of Mycoplasma synoviae. Aivlosin (3-acetyl-4"-isovaleryl tylosin tartrate), tylosin, and tiamulin showed the lowest MICs with MIC90s of 0.006, 0.012, and 0.05 microg/ml, respectively. Except one strain that showed resistant values to chlortetracycline (> or = 12.5 microg/ml), all the analyzed strains were susceptible in different degrees to all the antibiotics tested. In this study, the improved activity of the tylosin-derived drug, aivlosin, was confirmed because it showed, in most strains, MIC values half those for tylosin.

Isolation and identification of mycoplasma strains from various species of wild rodents.

Attempts were made to isolate mycoplasmas from respiratory and urogenital tracts of 35 apparently healthy wild rodents comprising 7 species under 4 genera. Mycoplasmas were isolated from nasal and oral cavities, tracheas, vaginas and penises of the wild rats: ricefield rats (Rattus argentiventer), roof rats (R. rattus) and Polynesian rats (R. exulans), but none was isolated from brown rats (R. norvegicus), house mice (Mus musculus), smithi's voles (Eothenomys smithi) and soft-furred field rats (Millardia meltada). These mycoplasma strains were identified as Mycoplasma pulmonis and M. arthritidis on the basis of their biological and serological properties.