Experimental studies of the pathogenesis of Pseudomonas aeruginosa infection: evidence for the in-vivo production of a lethal toxin (Plate V)

Abstract

PLATE V I N a previous report (Stieritz and Holder, 1975) we described an experimental burned-mouse model that was particularly suitable for investigating the pathogenesis of Pseudomonas aeruginosa infection ; early events in the establishment of the infection within the burned host were studied and growth of the organism in vivo was examined by quantitative bacteriological procedures. The results suggested that a lethal toxin was produced at the site of infection in the burned skin, and histological studies supported this hypothesis.Earlier investigators suggested that a lethal, diffusible toxin is produced by P. aeruginosa in the wounds of burned patients (Moncrief and Teplitz, 1964; Alexander, 1971). Furthermore, the degree of toxaemia was found to be related to the concentration of organisms in the burned tissues (Alexander, 1971).Our earlier studies suggested that the mouse model might be useful in the study of infection of burns, and this communication reports further experimental evidence that P. aeruginosa growing in burned tissues produces a lethal toxin. MATERIALS AND METHODS Animals andprocedures.All experiments were performed with female CF1 mice (Carworth Farms) weighing 22-24 g. Animals were housed in wire cages and given food and water ad libitum.The procedure used in producing burns has previously been described (Holder and Jogan, 1971). Anaesthetised mice were given a 10-s burn with an ethanol flame on the shaved back involving approximately 30 % of the total body surface. Immediately thereafter approximately 100 organisms in 0.5 ml of physiological saline (PS) were injected subcutaneously in the burned area. Burned but uninfected control animals received 0.5 ml of sterile PS instead of bacterial suspension. P. aeruginosa. Throughout these studies a single strain, originally isolated from the intestinal tract of a normal CF1 mouse (Stieritz and Holder, 1975), was used.Counts of P. aeruginosa in tissues and organs. Counts in the burned skin, livers and spleens of infected animals were determined, either immediately post rnortern or at the time stated, by the method of Saymen et al. (1972). Results are expressed as the loglo of the count per gram (wet weight) of tissue.

Differential Immunological Phenotypes Are Exhibited After Scald and Flame Burns

“…Therefore, it is appropriate that the predominant models used over the years to study burn injury have used either a flame burn (1) or a scald (2). Partial- and full-thickness burn models have been developed by varying the temperature and/or duration of the burn.…”

Evaluation of Pseudomonas aeruginosa toxin A in experimental rat burn wound sepsis

“…Deaths were consistently caused by invasive infection and hematogenous spread of the infection to various organs including the lung, kidney, spleen, and heart. These inflammatory lesions do not occur in the burned mouse model (9) suggesting that the latter may be a toxic rather than an infectious model. Immunization with toxoid as described here induced moderate but not high levels of antitoxin.…”

Pseudomonas aeruginosa infection and vaccination in the rat

“…Exotoxin A, which like diphtheria toxin inhibits protein synthesis (Igewski, Liu and Kabat, 1977), is produced in vitro by most P. aeruginosa strains (Pollack, Taylor and Callahan, 1977); it is produced within lesions (Saelinger, Snell and Holder, 1977), is cytotoxic for macrophages, and induces liver necrosis (Pavlovskis, Voelker and Schackelford, 1976;Pollack and Anderson, 1978). Although antitoxin neutralises cytotoxity in vitro (Leppla, 1976), the manifestations of pseudomonas infection cannot all be ascribed to toxin, and antitoxin does not protect from a lethal challenge (Snell et al, 1978;Stieritz and Holder, 1978). High antibody levels to exotoxin A and proteases in cystic fibrosis patients were directly related to the severity of the disease (Klinger et al, 1978).…”