Infecção por micoplasma e efeitos inflamatórios em roedores criados em laboratório para pesquisa experimental Infección por micoplasma y efectos inflamatorios en roedores criados en laboratorio para investigación experimental ABSTRACT Mycoplasma pulmonis is the agent of murine respiratory mycoplasmosis and is the most frequently isolated species from laboratory rats. One of the important consequences of its infection is the reduction of breeding rates and significant interferences in the experiments using these animals. Its experimental infection is also considered a model for studying human infection by M. pneumoniae. We have recently reported M. pulmonis infection rates of up to 75% in rodents bred in facilities for experimental research; however, its effect in the animals' immune system was not evaluated. Therefore, the aim of this work was to investigate the effect of M. pulmonis in rats bred at the animal facility of University of Blumenau, by polymerase chain reaction and culture, in order to verify the viability of the use of these animals for experimentation. Inflammatory parameters, such as C-reactive protein (CRP) and alpha-1 acid glycoprotein (A1GP), as well as haematological parameters were determined from blood samples. It was observed a positivity rate of 80% of M. pulmonis infection. It was also noticed that mycoplasma infection was associated with increased CRP and A1GP levels, as well as blood monocytes. Considering that the possibility of mycoplasma infection is a well-known issue, and that the routine examinations and preventive measures have been well standardised internationally for many years, the findings of this study indicate that the use of the evaluated animals is inacceptable for experimental research. It is strongly advisable that laboratories which conduct this kind of research should be assured of the absence of mycoplasma infection in the animals were used.