Real-time polymerase chain reaction assays for the detection of members of the Mycoplasma mycoides cluster

Abstract

AIM: To develop real-time PCR assays for the detection and differentiation of members of the Mycoplasma mycoides cluster.

METHODS: Five real-time PCR assays were designed to allow differentiation of members of the M. mycoides cluster: an assay for detection of the M. mycoides subspecies, viz M. mycoides subsp mycoides large colony (MmmLC), M. mycoides subsp capri (Mmc), and M. mycoides subsp mycoides small colony (MmmSC); one for the detection of the M. capricolum subspecies, viz M. capricolum subsp capricolum (Mcc), M. capricolum subsp capripneumoniae (Mccp), and Mycoplasma sp bovine group 7 (BG7); and three for the specifi c detection of MmmSC, Mccp, and BG7. A panel of 74 Mycoplasma isolates from various geographical origins and a panel of 21 other bacterial isolates were used to evaluate the sensitivity and specificity of the assays.

RESULTS: The assays displayed 100% analytical sensitivity in detecting all target Mycoplasma isolates. The analytical detection limit for the assays to detect the M. mycoides subspecies, M. capricolum subspecies, and MmmSC was determined to be 100 fg of genomic DNA, while the Mccp and BG7 assays had a detection limit of 100 fg and 10 fg of genomic DNA, respectively. The M. mycoides subspecies assay had a detection limit of 10³ (SD 10²) cfu/ml milk, 10⁴ (SD 10⁴) cfu per swab, and 10³ (SD 10³) cfu/g lung in inoculated samples. The assays displayed 100% specificity when applied to non-target bacterial isolates and to 110 culture-negative milk samples.

CONCLUSIONS: The assays were highly sensitive and specific, and provide accurate detection and differentiation of the members of the M. mycoides cluster.

KEY WORDs:

• Mycoplasma mycoides cluster
• real-time PCR
• diagnostic assays

Acknowledgements

We would like to sincerely thank Mr Trevor Taylor (AAHL, Australia), Dr. Göran Bölske (National Veterinary Institute, Sweden), Professor Joachim Frey (Institute of Veterinary Bacteriology, Switzerland), and Dr Marc Marenda (École Nationale Vétérinaire de Toulouse, France) for kindly providing gifts of DNA. This work was funded by the Ministry of Agriculture and Forestry.