A Previously Unreported Serotype of Avian Mycoplasma

Abstract

A new serotype of avian Mycoplasma (PPLO) was characterized and identified as Iowa 695. The original isolate was obtained in 1955 from pipped turkey-poult air-sac lesions. Additional isolations (22) were obtained from poult air-sac lesions, chicken trachea, oviduct, and embryonating eggs. Egg transmission is apparently significant. Cultures of Iowa 695 serotype form smooth, entire colonies, 0.1-0.3 mm in diameter, with discrete elevated centers on the medium used. It readily ferments dextrose and maltose, but not lactose. Culture sediment has afforded hemagglutination of chicken and turkey erythrocytes to as high as 1:640 dilution of the antigen. The HA activity is less stable than that of the S6 serotype, however. Isolates of 695 do not cause hemolysis of horse erythrocytes incorporated into solid medium. The new serotype is consistently pathogenic for chicken embryos inoculated via yolk sac at 7 days of age, causing deaths with hepatitis and splenomegaly within 5-8 days of inoculation. Isolates of 695 are capable of producing marked inflammatory reactions when inoculated into the tendon sheaths of the hock and foot-pad regions of chicks and poults. Repeated attempts have shown the inability of Iowa 695 isolates to produce sinusitis in experimentally inoculated poults, but an occasional air-sac lesion was noted. The significance of association of the Iowa 695 serotype with air-sac lesions in pipped turkey embryos is not known. Hemagglutination inhibition and tube agglutination studies have shown that the Iowa 695 serotype is sharply different from the other 8 reported serotypes of avian Mycoplasma.