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The immunochemical analysis of isolated and purified antigens A and B obtained from P. aeruginosa, strains 868 (serogroup O3 according to Lányi or immunotype 3/7 according to Fisher) and 170015 (serogroup O7 or immunotype 2), was carried out. Rabbit antisera to proteins A and B, as well as to the initial aqueous extracts and partially purified aqueous extracts, were obtained. Cross activity between the protein antigens of different strains was established by the methods of immunodiffusion and two-dimensional immunoelectrophoresis. Isolated proteins A and B contained both common and specific antigenic determinants detected by the method of two-dimensional immunoelectrophoresis. The immunization of rabbits with proteins A and B was found to stimulate the synthesis of protective, probably species-specific, antibodies.
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The specific features of the submicroscopic structure of the causative agents of melioidosis and glanders, grown in culture media and at the initial stages of experimental infection in guinea pigs and golden hamsters, were studied with the use of electronic cytochemistry and immunocytochemistry. P. pseudomallei and P. mallei were found to be capsule-forming bacteria. According to the data obtained with the use of electronic cytochemistry, the basis of the capsular substance P. pseudomallei and P. mallei is formed by polysaccharide biopolymers protecting these bacteria from phagocytosis.
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[This corrects the article on p. 1301 in vol. 50.].
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[This corrects the article on p. 383 in vol. 52.].
BACKGROUND: We observed an interaction in animals inoculated concomitantly with Staphylococcus aureus and Pseudomonas aeruginosa during a study of the efficacy of surfactants for disinfection of orthopaedic wounds. This led us to investigate whether synergy could be demonstrated between Staphylococcus aureus and Pseudomonas aeruginosa in a rat model of complex orthopaedic wounds. METHODS: A wire was implanted into the spinous process of a lumbar vertebra of Sprague-Dawley rats through a dorsal incision. Animals were divided into two groups: group one was inoculated with either Staphylococcus aureus or Pseudomonas aeruginosa, and group two received a polymicrobial inoculation with both test organisms in varying concentrations. After inoculation, the wounds were irrigated and closed. On postoperative day 14, all animals were killed and specimens from the wounds were cultured. The number of colony-forming units (CFU) of Staphylococcus aureus or Pseudomonas aeruginosa needed to cause infection in 50% of the animals (ID50) was determined with use of the Reed-Muench method. The infection rate associated with each inoculum combination was calculated, and the two groups were compared. RESULTS: The ID50 was 2.8 x 10(4) CFU for Staphylococcus aureus and 4.8 x 10(5) CFU for Pseudomonas aeruginosa. The combination of 10(3) CFU of Staphylococcus aureus with low concentrations (10(2), 10(3), or 10(4) CFU) of Pseudomonas aeruginosa yielded infection rates that were higher than those found with either organism alone at the same concentrations. The combination of 10(3) CFU of Staphylococcus aureus and 10(3) CFU of Pseudomonas aeruginosa yielded a 75% infection rate, which was significantly higher (p = 0.004) than that associated with 10(3) CFU of either organism alone. As the Pseudomonas aeruginosa concentration was increased (to 10(5), 10(6), and 10(7) CFU), this trend reversed, and the infection rate decreased to 33% (p = 0.004). Low concentrations of Pseudomonas aeruginosa (0 to 10(5) CFU) combined with 10(6) CFU of Staphylococcus aureus yielded infection rates ranging from 83% to 100%. At the higher concentrations of Pseudomonas aeruginosa (10(6) and 10(7) CFU), however, the infection rate again decreased, to 33% (p = 0.005). Only Staphylococcus aureus was isolated from the cultures of the specimens from the animals that had received a polymicrobial inoculum. CONCLUSIONS: Synergy between Staphylococcus aureus and Pseudomonas aeruginosa was demonstrated when low levels of each organism were present in the wound. As the Pseudomonas aeruginosa concentration was increased, the infection rates fell well below what would be anticipated, suggesting that low concentrations of Pseudomonas aeruginosa enhance the ability of Staphylococcus aureus to cause infection in this orthopaedic wound model. At the same time, the presence of Staphylococcus aureus in the ratios tested decreased the rate of infection by Pseudomonas aeruginosa. CLINICAL RELEVANCE: Staphylococcus aureus is a pathogen commonly seen in orthopaedic patients. The pathogenicity of Staphylococcus aureus was shown to be increased in the presence of anaerobic bacteria. This study is the first one that we are aware of that demonstrated synergy between Staphylococcus aureus and Pseudomonas aeruginosa, at low concentrations, in a wound model while at the same time showing that Staphylococcus aureus lowers the rate of Pseudomonas aeruginosa infection.
BACKGROUND: Pseudomonas is regarded as a particularly lethal bacterial isolate. High mortality rates have been reported in episodes of Pseudomonas sepsis when associated with visceral infections as seen in immunosuppressed, hospitalized patients. In comparison, lower mortality rates have been reported with catheter-associated Pseudomonas bacteraemia in non-dialysis patients. The purpose of this study was to determine the risk factors and the outcomes for episodes of Pseudomonas bacteraemia associated with the use of tunnelled cuffed haemodialysis catheters (TCCs) in a chronic out-patient population. METHODS: We performed a prospective observational study in seven chronic haemodialysis units over a 2.5 year period. Patients who were diagnosed as having their initial TCC-associated bacteraemia within the study period were followed for 3 months. All episodes of Pseudomonas TCC bacteraemia were identified, and univariate analyses were performed to compare Pseudomonas bacteraemia with non-Pseudomonas bacteraemia. RESULTS: During the study period, 219 episodes of TCC bacteraemia were identified; 18 had a Pseudomonas isolate (8%). Pseudomonas bacteraemia episodes were associated with a significantly higher risk of not receiving appropriate initial antibiotics (odds ratio = 3.6, P = 0.02). There were no deaths in the Pseudomonas bacteraemia group, whereas 19% died in the non-Pseudomonas group. The TCC was removed in 89% of Pseudomonas bacteraemias. There were no significant risk factors for acquiring a Pseudomonas isolate, and no difference in recurrent bacteraemia or infectious complication rates between the groups. CONCLUSIONS: In haemodialysis patients with a TCC-associated Pseudomonas bacteraemia, outcomes are remarkably good. This may be because the source of Pseudomonas infection was removed in most cases. Initial antibiotic coverage lacking anti-Pseudomonas activity was not associated with increased mortality.
Pneumococcal otitis media was induced bilaterally, and Pseudomonas was inoculated unilaterally into the middle ears of 36 chinchillas to study the pathogenesis of chronic suppurative otitis media. Half of the animals were treated with penicillin prior to Pseudomonas inoculation (day 7, late Pseudomonas), and half were inoculated with Pseudomonas before penicillin treatment (day 3, early Pseudomonas). A third group of 18 chinchillas received unilateral Pseudomonas inoculation without pneumococcus or penicillin (control). Animals with early Pseudomonas were significantly less susceptible to Pseudomonas infection in the Pseudomonas-inoculated ear than animals with late Pseudomonas and controls. Susceptibility to Pseudomonas infection in the contralateral ears, which were not inoculated with Pseudomonas, was significantly lower in early Pseudomonas and control animals than in late Pseudomonas animals. Increased susceptibility in the late Pseudomonas group might have been due to altered nasopharyngeal microflora or persisting eustachian tube dysfunction--factors that may be important in the pathogenesis of chronic suppurative otitis media in humans.