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SUMMARY: Among a large number of strains of aerobic sporing bacilli only Bacillus cereus, B. mycoides and, to a lesser extent, B. anthracis were able to produce turbidity and formation of a curd in saline extract of egg-yolk. None of the other species tested, namely, B. alvei, B. alcalophilus, B. brevis, B. carotarum, B. Circulans, B. coagulans, B. fusifomnis, B. licheniformis, B. macerans, B. megatherium, B. pumilus, B. polgmgxa, B. orpheecs, B. repens and B. subtilis caused any opalescence in the yolk medium. The yolk reaction was due to the action of phospholipinase produced by the organisms. As in the case of Cl. we&hii a-toxin, the yolk curd-forming activity of B. cereus and B. mycoides also was associated with haemolytic activity. The substances responsible for these activities appear to be sirhilar, and may be identical. The yolk reaction has proved useful for the rapid identification of B. cereus, as it is more specific than any of the other distinguishing tests hitherto employed. The three positive organisms, B. cereus, B. mycoides and B. anthracis, have been considered by previous workers on the grounds of morphology and antigenic structure to be closely related. Nagler (1989) described the effect of CZ. welchii cultures and toxic filtrates on human serum in producing an opalescence and curding (Nagler reaction) ; later Macfarlane, Oakley & Anderson (1941) found that egg-yolk saline (a lecithovitellin emulsion) is even more sensitive than human serum (the lecithovitellin (L.v.) reaction). Macfarlane & Knight (1941) then showed that the production of oialescence in egg-yolk emulsion was due to the action of a lecithinase, which split phosphocholine from lecithin, in the CZ. welchii toxic filtrates which was probably identical with the a-toxin. Since then, the Nagler reaction and the lecitho-vitellin (L.v.) reaction have been extensively used for the titration of a-toxin of CZ. welchii (Nagler, 1939; van Heyningen, 1941 a) and for the rapid identification of certain clostridia (Hayward, 1941(Hayward, , 1948.It is interesting that Nagler (1989) observed a non-pathogenic aerobic sporebearing bacillus which caused an opalescence in human serum like that caused by CZ. welchii; but the effect was not inhibited by CZ. welchii antitoxin. Crook (1942) and Hayward (1943) also mentioned that some aerobic bacteria caused similar opalescence. In the light of these observations we have sought for similar enzymes in the aerobic spore-bearing bacilli. The work started with a survey of the Bacillus group to ascertain which of them produced an eggyolk reaction. A test of 260 identified strains, comprising 24 species, showed that only B. cereus, B. mycoides and some strains of B. anthracis were positive.In comparison with other characteristics generally used for the differentiation of the BaeilZzcs group, the yolk reaction seems to be much more selective. One can hardly find any other characteristics which are confined to only two or three species of this very large group of organisms, and the test deserves the ...

SUMMARY : Bacillus cereus and B. mycoides produce lecithinases which split lecithin into phosphorylcholine and a diglyceride in the same way as the lecithinase (a-toxin) of Clostridium welchii. These enzymes also possess most of the biological activities associated with Cl. welchii a-toxin, e.g. produce the Nagler reaction and the egg-yolk reaction, lyse red blood cells, and are dermonecrotizing and lethal.The enzymes are activated by Ca and Mg ions, but inhibited by Nay K, NH, ferric and Al ions. Optimal enzyme activity requires the presence of Ca ions within a narrow range of concentration of 1-4 x 1 0 -S~. It is interesting that at this concentration of Ca ion lecithin flocculates most readily from its emulsion. The enzyme thus seems to have a maximal affinity for lecithin when the latter adsorbs an optimal amount of Ca ion in reaching its isoelectric point.Like the Cl. welchii lecithinase, the B. cereus lecithinase is fairly resistant to heat. The lysis of red blood cells and the hydrolysis of free lecithin by B. cereus lecithinase was strongly inhibited by normal sera of all the animals tested. But when lecithin was bound in egg-yolk lipoproteins, its hydrolysis by the enzyme was unaffected by normal serum. Specific serum, on the other hand, was capable of inhibiting the hydrolysis of both free lecithin and protein-bound lecithin. The B. cereus and B. mycoides lecithinases are immunologically related, but they are not so related to Cl. welchii lecithinase.

A study was made in liquid medium over 7 days at 37° C. of the inhibitory action of nineteen antibacterial, antifungal and antiprotozoal drugs on twenty strains ofM. gallisepticum, eight other avian mycoplasmata, six mammalian mycoplasmata, two saprophytic mycoplasmata and the L-form ofStreptobacillus moniliformis(L–1).The twenty strains ofM. gallisepticumfrom Britain and other countries showed a similar range of drug sensitivity except where resistant strains were included. Tylosin and demethylchlortetracycline appeared to have the highest inhibitory action, followed by erythromycin, spiramycin, tetracycline, chlortetracycline, oxytetracycline and ethidium bromide. A ‘Zone Phenomenon’ frequently occurred with sodium aurothiomalate, inhibition often being observed between 0·1 and 2·0 μg./ml. Polymixin and nystatin had no inhibitory effect on the growth of any mycoplasmata tested. With the exception of erythromycin and streptomycin in some cases, the pattern of sensitivity observed with the mycoplasmata of diverse origin was similar to that ofM. gallisepticum, most strains, however, being somewhat more resistant thanM. gallisepticumto many of the drugs.

PLATES LXV-LXVIIE A R L Y electron-microscope studies of metal-shadowed preparations of avian infectious bronchitis virus (IBV) revealed that the virus particle had a diameter of 60-120 nm (Reagan et al., 1948;Reagan and Brueckner, 1952). Later, negative staining showed it to differ from Newcastle disease virus in having less densely packed and more loosely attached surface projections that gave a strawberry-like appearance (Chu, 1964). Berry et al. (1964) confirmed that the projections of IBV are morphologically distinct from those of the myxoviruses, and reported that the diameter of the virus particle was 80-120 nm. Domermuth and Edwards (1957) examined ultrathin sections of IBV-infected chorio-allantoic membranes and observed intracytoplasmic particles having a doughnut-like appearance and measuring 178-200 nm in diameter. Viruses isolated from the respiratory tracts of persons with common colds have been described as " avian infectious bronchitislike " on account of their morphology in negatively stained preparations (Almeida and Tyrrell, 1967). However, differences in internal structure have been reported between the avian and human viruses present in ultrathin sections of infected chorio-allantoic membrane and human embryo kidney tissue culture cells respectively .