An extracellular protease from Pseudomonas aeruginosa having collagenase activity was assayed in vivo. The lethality of the enzyme for white female mice was determined by use of intravenous, intraperitoneal, intranasal, and subcutaneous routes, respectively. The collagenase exhibited the following 72-hr mean lethal dose values: intranasally, 55 collagenase units; intraperitoneally, 148 collagenase units; and intravenously, 288 collagenase units. In the concentrations tested, no lethality was obtained when the subcutaneous route was employed. Gross and microscopic studies revealed that the collagenase was capable of eliciting a variety of tissue responses in mice depending upon its route of administration. Intranasal instillation resulted in confluent pulmonary hemorrhage, whereas intraperitoneal injections resulted in severe abdominal hemorrhage with foci on the intestinal serosa. Intravenous injections elicited abdominal hemorrhage and petechial hemorrhage with focal necrosis of the lungs, whereas subcutaneous injections resulted in necrotic, ulcerating lesions.

No abstract

Tracheal intubation of viable Pseudomonas aeruginosa ATCC 19660 into the lungs of mice had no significant effect on the animals even with administration of organisms as high as 5.0 X 10(9) CFU. Animals treated with a single injection of an antineoplastic drug were, however, susceptible to bacterial challenge into the lungs. LD50 values of 4.1 X 10(7), 4.8 X 10(7), and 1.0 X 10(8) CFU were obtained when animals were simultaneously infected and treated with methotrexate, vincristine sulfate, or cytosine arabinoside, respectively.

Electron microscopy of sectioned cells of Pseudomonas aeruginosa treated with a double fixative in N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid revealed a number of membranous inclusions varying in size and morphology. One round, electron transparent form was frequently observed which did not routinely appear to be attached to the cytoplasmic membrane and varied in size from 120 to 300 nm in diameter. However, in one case, several tubular structures between an inclusion and the cytoplasmic membrane was observed. On rare occasions, a large and unusual multilayered inclusion consisting of three thick and distinct layers was also encountered. In addition, two small mesosomal structures were singly observed in cells and were situated proximal to the cytoplasmic membrane. One type appeared to consist of a single thin membrane, whereas the other type consisted of a delicate, multilayered structure.

Peroral administration of viable Pseudomonas aeruginosa into the stomach of mice resulted in an acute systemic infection, with death occurring within 72 h. One strain, ATCC 19660, a non-encapsulated form of P. aeruginosa, had a median lethal dose of 5.3 X 10(6) colony-forming units, whereas two encapsulated strains, ATCC 17933 and 17934, had median lethal dose values of 5.0 x 10(7) and 5.6 x 10(7) colony-forming units, respectively. Each strain required fewer organisms to establish a lethal infection via the stomach than by intravenous or intraperitoneal routes. The non-encapsulated strain, ATCC 19660, did not cause any diarrhea in the infected animals, whereas the two encapsulated strains, although less virulent, caused diarrhea when administered perorally. No signs of necrosis were noted within the gastrointestinal tract; however, hematogenous spread of the organism resulted in a vasculitis associated with the pulmonary vessels and bacterial invasion of the renal tissues. Treatment of animals with antineoplastic drugs 24 h before or simultaneously with peroral challenge resulted in an increased susceptibility to infection.