Survey of Brucellosis in Slaughtered Hogs

Abstract

Submaxillary lymph nodes were obtained from hogs slaughtered in one of the large packing plants in Chicago. Samples were obtained each week for a period of 6 months. The lymph nodes were removed from the carcass immediately after the initial Bureau of Animal Industry inspection of head glands. Each specimen was removed with sterile instruments and placed in an individual sterile screw-capped glass jar. Upon return to the laboratory, the samples were promptly cultured. Each node was trimmed of fat and excess tissue, seared in a flame, sectioned, and the cut surface serrated and streaked directly on the surface of trypticase-soy agar medium. Sterile instruments were used throughout. The inoculated plates were incubated at 370 C. in an atmosphere of 10 percent added C02. In cultures heavily overgrown with other organisms, Brucella cannot be detected. Hence, all plates showing an overgrowth were discarded and not included in the series. During the entire investigation, 152 plates were discarded for this reason. Plates streaked with nodes from which Brucella was not recovered have in most instances remained sterile or contained only scattered colonies of ubiquitous bacteria. Plates yielding Brucella have uniformly contained numerous colonies of the organism.