A comparison of four methods for detecting beta-lactamase in anaerobic bacteria

Four methods for detecting beta-lactamase activity in anaerobic bacteria were evaluated and compared to a nitrocefin saturated filter paper test. The methods studied were Cefinase, PADAC, Beta Lactam, and the slide iodometric technique. Fifty anaerobes were tested including species of Bacteroides, Fusobacterium, and Clostridium. The percentages of agreement with the nitrocefin test are: Cefinase 100%, PADAC 96%, slide iodometric 78%, and Beta Lactam 72%. Positive nitrocefin tests have been shown to correlate with a penicillin MIC greater than 0.78 micrograms/ml.