Evaluation of six culture media for supporting the isolation of Brucella abortus and Brucella melitensis

Abstract

Brucellosis is endemic in many developing countries and is caused by many species of the genus Brucella that affect man, domestic and some wild animals, and marine mammals, It is estimated at 500, 000 new human cases of brucellosis annually worldwide Brucellosis is the most important zoonosis and has gained prominence over the years since its discovery on the island of Malta.To facilitate monitoring of culture media, a simple quantitative streaking techniques in spiral plating was used. The procedure evaluates, in quantitative terms, the ability of media to support the formation of colonies by organisms under test. The procedure was named ecometric evaluation.. This study aimed to compare between six media for their degree in supporting the growth of Brucella. These media included Potato infusion agar, Serum Dextrose agar, Tryptose agar, Tryptose Soy agar, Thayer-Martin agar and Blood agar. All media in the study passed the ecometric assessment with different degrees, indicating that most of these formulations would provide an acceptable medium for isolation of Brucella even if the sample contains small numbers of viable organisms. Two isolates were used for conducting the tests, Brucella abortus (animal isolate) and Brucella melitensis (human isolate). , a duplicate of each media was used. A suspension of about 1010 organism's /ml of suspension for each organism under test was inoculated onto each of the media using the ecometric technique The plates were divided to four quarter(A,B,C and D) any quarter represented 25% of cultured 5 lines by full loop of the suspension was streaked 5 times on to medium represent 5% of the culture then incubated at anaeropic incubation by adding 10% CO2 at 37oC for three to five days and at 37oC at aerobic condition. The growth of two isolate on tryptose agar serum dextrose agar thyr.martin agar potatoes agar and blood agar was 100% at anaerobic incubator by adding 10% CO2 at 370C. In aerobic incubation at 370C the growth rates were lower and to varying degrees of 25-100 at B.miletensis and 55-100 at B.abortus. .