Fresh white cheese as a source of Brucella infection

Abstract

Human and animal brucellosis is a disease of public health and economic significancein Iran. The consumption of unpasteurized dairy products is one of the important sources of human brucellosis. Fresh white cheese which is produced locally and sometimes privately in country houses from raw goat and sheep milk is probably the most important way of transmission. Out of 1220 fresh white cheese specimens, 86(7%) were found infected with Brucellamelitensis biotype I. These specimens were collected from retail shops in three highly infected villages over a period of 12 months. The average number of organisms per gram of infected cheese was 2120 after collection, which decreased until the ninth week when no Brucella could be isolated. About 40% of infected cheese became free of Brucella one week after collection and in weekly culture 50% of the specimens continued to be infected up to the third week. At the eighth week, only 1·1 % of the 86 infected cheeses showed infection with B. melitensis. The cheese collected from retail shops had a low pH and during weekly culture in the laboratory, B. melitensis was isolated from the specimens within a wide range of pH (5·0–7·6). The seasonal fluctuation of infected cheese corresponds to human brucellosis inwhich most cases are seen from April through August with the maximum rate in May and June.