蛋白酶对假单胞菌烧伤感染小鼠模型的实验研究

StraHolder (Abstr. Annu. Meet. Am. Soc. Microbiol. 1977, B118, p. 35) and Pavlovskis and Wretlind (Abstr. Annu. Meet. Am. Soc. Microbiol. 1978, B89, p. 28) have used a mouse burn infection model (13, 38) that resembles human burn wound sepsis to show that protease producers are more virulent than protease-deficient strains. In this model, the burn is nonlethal and infection is reproducibly produced by a small inoculum. Since the in vivo role of a given product of an organism can best be studied by using mutants lacking the ability to produce it, we examined the role of protease in pseudomonas infection by using a protease-producing wild type and its protease-deficient mutants. A similar approach has been used to define virulence factors of salmonella and Staphylococcus aureus in experimental animal infections (9, 19). By examining the protective effect of antiprotease serum in this model, we attempted to define the pathogenic role of protease as well as evaluate the immunoprophylactic potential of antiprotease serum. The results of this study indicate that protease enhances the virulence of pseudomonas and that its deleterious effects can be neutralized to some extent with antiprotease
INFECTION AND IMMUNITY, Apr. 1979, p. 181-187 0019-9567/79/04-0181/07$02.00/0
Vol. 24, No. 1
蛋白酶对假单胞菌烧伤感染小鼠模型的实验研究
Assessment of Protease (Elastase) as a Pseudomonas aeruginosa Virulence Factor in Experimental Mouse Burn Infection
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PAVLOVSKIS AND WRETLIND
INFECT. IMMUN. TABLE 1. Properties of P. aeruginosa strain PAKS1 and its protease-deficient mutants
Extracellular enzyme activities' (U/mg of cell [dry wt])
OLGERTS R. PAVLOVSKIS' * AND BENGT WRETLIND2 Department ofMicrobiology, Naval Medical Research Institute, Bethesda, Maryland 20014,' and Department of Clinical Microbiology, Karolinska Hospital, S-10401 Stockholm, Sweden'
Received for publication 18 January 1979
The data presented indicate that in experimental Pseudomonas aeruginosa infection of mice, protease enhances the virulence of the organism. Anesthetized CBA/Lu mice were subjected to a 15-s flame burn and infected with a wild-type protease-producing strain and two of its protease-deficient mutants. The average bacterial cell mean lethal dose (LD5o) of 3.8 ± 0.3 standard deviation logoi) for mice infected with the protease-producing P. aeruginosa was at least 1 log lower than the LD5o of the protease-deficient mutants (0.02 > P > 0.01). The addition of purified protease to the infecting inoculum of protease-deficient strains reduced the LD50. Although the generation time in vitro was the same for all three bacterial strains used, there were consistently fewer viable bacteria in the blood of mice infected with protease-deficient strains than in those infected with the protease-producing strain. When a protease-deficient strain was mixed with the protease-producing wild-type strain, the number of protease-producing pseudomonas found in the blood remained constant, whereas the number of proteasedeficient organisms increased, suggesting that protease contributed to the invasiveness of the organisms. The survival of mice infected with protease-producing pseudomonas was enhanced by antiprotease serum. Antiprotease serum had no effect in mice infected with protease-deficient mutants. The pathogenesis of Pseudomonas aeruginosa infections has been investigated by examining a variety of extracellular products. Although exotoxin A (2, 3, 23) has been shown to be an important virulence factor in experimental infections (32, 33, 36, 37), other pseudomonas products have been implicated as well (21, 24, 30, 43). The proteolytic enzymes have aroused special interest since Carney et al. (4) presented evidence that they contribute to the invasiveness of the organisms. Despite the accumulating information on the biological activities of pseudomonas proteases (8, 10-12, 14, 15, 17, 18, 25), their roles in infections have not been clarified. Muszynski (31) found a correlation between pseudomonas protease production in vitro and virulence for mice. Others have shown that pseudomonas strains isolated from patients with septicemia produced larger amounts of protease than strains from other sources (A. Davis and J. R. Doubek, Abstr. 265, and A. L. Baltch, P. E. Griffin, and E. Malatino, Abstr. 266, Program Abstr. Intersci. Conf. Antimicrob. Agents Chemother. 15th, Washington, D. C., 1975). In contrast, Wretlind et al. (39) and Hedberg et al. (12) found no significant differences in production of