IRON MILK MEDIUM METHOD FOR RECOVERING CLOSTRIDIUM-PERFRINGENS FROM SHELLFISH - COLLABORATIVE STUDY

Eleven laboratories participated in a collaborative study analyzing sh ellfish (oysters, Crassostrea gigas) for the detection and enumeration of Clostridium perfringens by the iron milk medium (IMM) method. The IMM method was compared to AOAC Official Method 976.30. Shellfish were artificially inoculated with C. perfringens cells (vegetative and spo res) at low(1 x 10(3) colony forming units [cfu]/g), medium (1 x 10(4) cfu/g), and high (1 x 10(6) cfu/g) levels. Negative controls (zero le vel) were analyzed by each laboratory. C. perfringens FD-1,the strain involved in a foodborne illness, was used. Blind duplicates of each in oculum level were analyzed, giving a total of 16 samples per laborator y. The selectivity of IMM relies solely on the rapid growth of C. perf ringens at 45 degrees C indicated by stormy fermentation reaction with in 18 h. C. perfringens is detected and enumerated using the most prob able number technique. A statistical evaluation of the data found no s ignificant differences between the estimates from the 2 methods. The I MM method for detection of C. perfringens from shellfish has been adop ted first action by AOAC INTERNATIONAL.