A collaborative assay of mycoplasma reference antisera

A total of 29 Mycoplasma and Acholeplasma antiserum reagents produced in mules and horses by the Baltimore Biological Laboratory and by Huntingdon Research Centre, under the auspices of National Institutes of Health, Bethesda, USA, were tested for potency and specificity, by a great variety of serological techniques, at the FAO/WHO Collaborating centre for Animal Mycoplasmas, University of Aarhus, Denmark. Subsequently, the antisera were subjected to a collaborative assay in which 20 workers from 15 different laboratories participated under the auspices of the International Research Programme on Comparative Mycoplasmology, International Organization for Mycoplasmology (IOM). Each antiserum was tested for homologous and heterologous reactivity by the growth inhibition (GI) and metabolism inhibition (MI) tests in at least two different laboratories. In addition, nine antiserum reagents were subjected in the lyophilized state to accelerated thermal degradation tests. The overall picture of the results obtained with the GI test was that of a remarkable degree of agreement among observations made in the different laboratories and with those originally reported by the Collaborating Centre. Results obtained with the MI test generally showed greater variation from one laboratory to another and, to some extent, on repeated testing of a serum in the same laboratory. From the combined results of the two tests the potencies of nine antisera were considered to be below acceptable levels for reference reagents. The potency of the remaining 20 antisera ranged from satisfactory to very high levels. Additionally these sera proved highly specific in both tests. The results of the thermal degradation tests carried out on about one-third of the serum reagents showed the stability of these reagents to be very satisfactory and to satisfy international requirements. It was concluded that although the antisera tested could not be established as standard reference reagents they should be regarded as working reagents. In this capacity they have already proved extremely useful in a great many mycoplasma laboratories all over the world.