Detection of natural Mycoplasma pulmonis infection in rats and mice by an enzyme linked immunosorbent assay (ELISA).

A total of 2,194 rats and mice representing 10 rat and nine mouse strains from eight commercial breeding facilities and 19 research institutions were tested for Mycoplasma pulmonis antibodies of the IgG and IgM classes by an enzyme-linked immunosorbent assay (ELISA). Cultural data also were obtained from 1,139 of these animals and histopathological data from 410. Reliability of the IgG ELISA for detection of infection in rats and mice was found to be excellent. Virtually no rat or mouse colony was culturally negative and IgG ELISA positive, or vice versa. However, discrepancies between ELISA and cultural results were observed in individual animals. Discrepancies occurred significantly more often with the IgM than IgG ELISA and more so in mice than in rats, particularly in barrier-maintained animals. Agreement of the IgG and IgM ELISA with culture in barrier-maintained rats was 100% and 94%, respectively and in barrier-maintained mice 87% and 69%, respectively. Available evidence suggested that some of the discrepancies in mice could be due to either active or previous low level infection or failure to culture multiple sites. However, the greatly reduce correlation of the IgM ELISA and culture in mice was incompletely understood, and in the absence of other evidence of infection must be interpreted with caution. Even though the present study was not designed to determine comprehensive incidence figures, the results indicated widespread Mycoplasma pulmonis infection both in conventional and "barrier-maintained" colonies as demonstrated by ELISA a well as cultural isolation.