Abstract
DNA amplification techniques offer considerable promise for the identification of Mycoplasma mycoides cluster members. They avoid antigenic cross-reactivity and variability that hamper serological methods. Many sets of primers, specific of these different members and of Mycoplasma putrefaciens, have been proposed. To assess the reliability of some of these PCR tests in routine laboratory diagnostic use, 230 field strains supposed to belong to this group were simultaneously identified by PCR and an antigenic method. The results were well correlated to antigenic identification for M. putrefaciens, but PCR failed to identify respectively 74% and 52% of M. mycoides subsp. mycoides Large Colony type and M. capricolum subsp. capricolum strains. Any identification of M. mycoides subsp. mycoides Small Colony type must be confirmed by two different tests. Difficulties in defining the M. species bovine serogroup 7 were also encountered with both the PCR and immunological methods. The occurrence of putative variable antigen(s) on the mycoplasma surface may explain part of the identification difficulties encountered with the immunological methods.
Highlights
The so-called Mycoplasma mycoides (M. mycoides) cluster [7] consists of very closely related mycoplasmas, belonging phylogenically to the spiroplasma group [35], and that are of great concern in ruminant production
III): – 5 strains isolated from goats and bovines but not belonging to the M. mycoides cluster and currently serologically unclassifiable; – 3 strains with atypical cross-reacting schemes with the different M. mycoides cluster polyclonal anti-sera used; – 23 strains identified as MmmSC with a polyclonal sera and the monoclonal antibody 3F3; – 65 strains with the double serological valence M. capricolum subsp. capricolum (Mcc)/M. species bovine serogroup 7 (Msp7) or strictly similar to the Msp7 strain PG50; – 96 strains with the double serological valence MmmLC/M. mycoides subsp. capri (Mmc); – 38 strains of M. putrefaciens
P: positive; D: doubtful; N: negative. a Strains isolated from goats and bovines but not belonging to the M. mycoides cluster and serologically unclassifiable until now. b Strains with an atypical cross-reacting scheme with the M. mycoides cluster polyclonal anti-sera used. c Strains cross-reacting with the anti-Mcc and/or the anti-Msp7 polyclonal sera. d Strains cross-reacting with the anti-MmmLC and/or the anti-Mmc polyclonal sera. e Strains identified as MmmSC with polyclonal sera and monoclonal antibody 3F3 [4]. f Atypical amplification profile. g Reactions range from doubtful to very ambiguous and vary in intensity with different assays
Summary
The so-called Mycoplasma mycoides (M. mycoides) cluster [7] consists of very closely related mycoplasmas, belonging phylogenically to the spiroplasma group [35], and that are of great concern in ruminant production This group comprises the following species, subspecies and types: M. mycoides subsp. M. putrefaciens (causing mastitis and arthritis), M. cottewii, and M. yeatsii (pathogenic activity unknown) [8] are three antigenically distinct species found in goats and are not regarded as members of the classical M. mycoides cluster. Classifying the members of M. mycoides cluster has always been problematic: (i) Extensive and complex cross-reactions occur between subspecies or types, and acute antigenic identification of CBPP and CCPP agents has been achieved only through the use of specific monoclonal antibodies [4, 32]; (ii) High antigenic heterogeneity within some types or subspecies (MmmLC, Mcc) hampers identification [6, 18, 27]; (iii) The definitive taxonomy of the M. mycoides cluster has not yet been established and discrepancies have recently appeared between their taxonomy and phylogeny. To evaluate the selected primers, 230 field strains presumed belonging to, or closely related to, the M. mycoides cluster were identified using both PCR and antigenic methods
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