Collagenase enzyme activity of 38 Pseudomonas aeruginosa strains and 38 strains of Escherichia coli from various pathological sources was measured by a simple method. This method uses plates with collagen gel. The rate of gel lysis is proportional to the collagenase concentration. The method is simple and requires no special materials or equipment. From the 38 P. aeruginosa strains, 34 were collagenase positive. All 38 strains of E. coli were collagenase negative. Collagenase, e.g.,

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... ptidase A, hydrolyzes native collagen under physiological conditions. Collagenase in both bacterial and mammalian tissues has been extensively studied. Its presence in human synovia (5, 18), gingiva (2), granulocytes, and skin (4) has also been thoroughly investigated. The most extensive work has been carried out on the bacterial collagenases. These are found, in particular, in Clostridium histolyticum, Clostridium perfringens, Clostridium capitorale, Pseudomonas aeruginosa, and Mycobacterium tuberculosis. The study of bacterial collagenase is significant since this enzyme attacks collagen and reticulin in muscles. Reticulum is a complex of proteins containing collagen; when attacked by collagenase, only collagen is split. The removal of reticulin around capillaries and small vessels can produce both hemorrhage and thrombosis (4). The purpose of this study was to examine collagenase activity in P. aeruginosa. The importance of P. aeruginosa in human disease is well known, especially in nosocomial infections and in patients being treated with corticosteroids, radiation therapy, antineoplastic drugs, and prolonged antimicrobial therapy. P. aeruginosa produces a variety of extracellular substances that may play a role in the disease process. Of particular interest are the proteolytic enzymes. Some of these enzymes attack coiled polypeptide chains but are inactive against undenatured collagen molecules. True collagenolytic activity can be demonstrated only when undenatured collagen is used. The following methods have been reported for determining the activity of collagenase: viscometric (17), ninhydrin determination (12, 15), radioactive collagen substrates (10, 19) , and collagen gel plates (8, 11). Our group used collagen gel plates with standards that can quantitatively determine collagenase in various sources (9). Bacterial strains. The 38 strains of P. aeruginosa and 38 strains of E. coli were obtained from pathological body fluids such as urine, pus, blood, and sputum. Preparation of crude enzymes. Batches of 100 ml of tryptic soy broth (Difco Laboratories, Detroit, Mich.) were inoculated with each of the strains and incubated ca. 40 h. The medium was then passed through a bacteriological filter (model 9.EK; Seitz Filter Original Kreuznach Grosse), and 4 * Corresponding author. activity of bacteria.