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Gene expression of pro-inflammatory cytokines and chemokines in mouse eye infected with Pseudomonas aeruginosa.

Ocular infection with Pseudomonas aeruginosa triggers extensive host inflammatory response and corneal damage. The purpose of present study was to investigate the gene expression of pro-inflammatory mediators interleukin (IL)-1 beta, IL-6, tumour necrosis factor-alpha (TNF-alpha),macrophage inflammatory protein (MIP)-2 and cytokine-induced neutrophil chemoattractant (KC) in the mouse eye challenged with P. aeruginosa. Scratched mouse corneas were infected with three phenotypes of P. aeruginosa individually. Total RNA was extracted from mouse eyes at 4 h, 8 h,16 h and 24 h post-challenge. Single stranded cDNA was synthesized from total RNA by reverse transcription and then subjected to polymerase chain reaction (PCR) using specific primers for IL-1 beta, IL-6, TNF-alpha, MIP-2 and KC. Results revealed three patterns of cytokines and chemokines expression in response to ocular infection with three phenotypes of P. aeruginosa. Ocular infection with the invasive strain induced the highest levels of IL-1 beta, IL-6, MIP-2 and KC mRNA, followed by the infection with the cytotoxic strain. Ocular infection with the CLARE strain induced the lowest levels of IL-1 beta, IL-6, MIP-2 and KC mRNA. The expression of TNF-alpha mRNA was very low and irregular following P. aeruginosa challenge. These data indicate that over-expression of pro-inflammatory cytokines and chemokines may represent a vigorous immune response and therefore may contribute to corneal damage during P. aeruginosa infection.

Animals↗

Pseudomonas aeruginosa infection in cancer patients.

Pseudomonas aeruginosa is an important cause of infection in immunosuppressed patients, particularly those with cancer. However, it is being recognized with greater frequency in patients who appear to be immunocompetent. Changes in modern lifestyles have led to the appearance of some new manifestations of pseudomonas infection including corneal ulceration and keratitis associated with contact lenses, and hot-tub- or whirlpool-associated folliculitis. These represent additional hazards to patients with cancer. Many studies, both in animals and humans, have contributed to our knowledge of the pathogenesis, immunology, treatment, and prevention of pseudomonas infections. Although the aminoglycosides represented a significant step forward in the treatment of these infections, of greater importance was the discovery of the antipseudomonal penicillins. These antibiotics are more effective than the aminoglycosides in neutropenic patients, who are especially susceptible to pseudomonal infections. The older antipseudomonal penicillins (carbenicillin, tircarcillin) have largely been replaced by newer ones (mezlocillin, azlocillin, pipercillin) which are more potent in vitro against P. aeruginosa. Although the accepted therapeutic practice has been to utilize a penicillin in combination with an aminoglycoside, the introduction of newer beta lactam agents and fluoroquinolones with antipseudomonal properties offers the possibility of other approaches to combination therapy. These include the combination of a penicillin or a cephalosporin or the combination of a quinolone with an aminoglycoside or a betalactam antibiotic. However, the development of newer antimicrobial agents is not likely to be a lasting solution to the problem of pseudomonas infections. Since pseudomonas infection often progresses rapidly, optimal results will always depend upon the prompt initiation of appropriate therapy in febrile patients, particularly those who are at high risk. The use of granulocyte transfusions has proved to be of limited benefit. Early data with the use of monoclonal antibodies is promising, and the results of large-scale trials are eagerly awaited. It is hoped that continuing investigation of pseudomonas vaccines will lead to the discovery of effective prophylaxis for highly susceptible patients. It is also hoped that with the availability of GM-CSF it will become possible to reduce the period of risk for serious infections. Finally, a reduction in the frequency of microbiologically proven P. aeruginosa infections in cancer patients should not lead to the assumption that these organisms do not constitute a problem in such patients anymore. The use of prophylactic antibiotics and prompt empiric antibiotic coverage for therapy has resulted in this decline. Cultures are therefore unlikely to be positive with the same frequency as they were before antimicrobial prophylaxis and empiric antibiotic therapy became standard practice.(ABSTRACT TRUNCATED AT 400 WORDS)

Anti-Bacterial Agents↗

Epidemiology of Pseudomonas aeruginosa infection and the role of contamination of the environment in the Danish Cystic Fibrosis Centre.

In order to identify the possible reservoirs and routes of cross-infection with Pseudomonas aeruginosa, samples were collected during a six-week period in autumn 1992 from patients, their visiting parents, staff and the inanimate environment of the Danish Cystic Fibrosis (CF) Centre and from a control ward with common paediatric diseases. All the P. aeruginosa strains were phage typed and serotyped. From 240 CF patients, 310 strains of P. aeruginosa were isolated, and of these 283 (91.3%) belonged to the polyagglutinable phenotype, most often with a short phage type (31/188 or 109). P. aeruginosa was isolated from only six (0.6%) of 1000 swabs taken from the environment. These six environmental strains and 20 P. aeruginosa strains from CF patients with identical serotype and phage type were examined with pulsed field gel electrophoresis. None of the patients harboured strains similar to the environmental strains, indicating the present isolation procedure and hygienic precautions were effective in our CF centre, and prevented contamination of the environment with P. aeruginosa.

Bacterial Typing Techniques↗

Pseudomonas aeruginosa: the potential to immunise against infection.

Pseudomonas aeruginosa remains a serious pathogen for specific cohorts of patients where chronic infection is a poor prognostic indicator, such as those with cystic fibrosis, burn wounds or those who are immunocompromised. Significant disease burden is associated with a diverse spectrum of both nosocomial and community-acquired infections. To date, vaccines against P. aeruginosa have shown limited and often conflicting efficacy data, especially against heterologous strains, which are increasingly identified as co-colonisers of biofilms. While few studies have gone beyond Phase II clinical trials, a particular concern is the ability of P. aeruginosa to evade the immune system while provoking an immune response that contributes to the destructive nature of infection. Therefore, vaccine development needs to focus on preventing attachment and colonisation, as well as preventing conversion to a mucoid phenotype that is characteristic of the chronic condition that promotes pathology.

Animals↗

Effect of thermal injury with Pseudomonas aeruginosa infection on pulmonary and systemic bacterial clearance.

BACKGROUND: Despite improvements in burn wound care, infections, particularly pneumonia, remain a major hurdle to recovery from thermal injury. After burns, a variety of systemic immune and inflammatory changes contribute to the risk of infection. Clinically, infection coupled with burn injury seems to adversely affect susceptibility to subsequent infection. METHODS: Using a mouse model of 10% total body surface area, full-thickness, third-degree burns with quantitative bacterial cultures of multiple tissues, the effect of graded intratracheal and intraperitoneal infections with Pseudomonas aeruginosa on the development of infection was assessed. RESULTS: P. aeruginosa infection of blood and lung were demonstrated in burned mice 4 hours after they received 1 to 7.2x10(5) P. aeruginosa intratracheally but not in unburned control mice. Disseminated infection from endogenous bacterial species (Proteus, Enterococcus, Streptococcus) involving the lungs, liver, blood, and subeschar space was observed in mice that received both burns and infection with P. aeruginosa (intraperitoneally and intratracheally) but not with infection or burn alone (p<0.01). After burns, pulmonary bacterial clearance was delayed in association with both pulmonary infection (7.2x10(5) P. aeruginosa intratracheally) and intraperitoneal infection (10(7) P. aeruginosa intraperitoneally). Histologically, diffuse pneumonitis was observed in mice that received burns and infection but not in mice with either infection or burns alone. CONCLUSION: Small thermal injuries coupled with transient infection of the lungs or peritoneum delay the clearance of bacteria from the lungs and contribute to infection of the lungs, liver, burn site, and blood by endogenous organisms. These studies support the synergy of relatively small thermal injuries with infectious exposures in the pathogenesis of pneumonia and systemic infections after burns.

Animals↗

Lipopolysaccharide pseudomonas vaccine: efficacy against pulmonary infection with Pseudomonas aeruginosa.

Pneumonia due to Pseudomonas aeruginosa occurs with increased frequency and high mortality in certain populations of patients. The potential of vaccination with a heptavalent lipopolysaccharide pseudomonas vaccine for specific protection of respiratory tissues from infection with Pseudomonas was evaluated with a guinea pig model of experimental pseudomonas pneumonia. Animals routinely responded to vaccination with a fourfold rise in titer of serum hemagglutinating antibody to Pseudomonas. Of 25 control animals, all but nine died after lung challenge with Pseudomonas, whereas vaccinated animals had a greater survival rate (22 of 25 animals survived; P less than 0.01). Rates of clearance of viable Pseudomonas from lung tissue were significantly greater in vaccinated animals than in controls during the first 6 hr after infection. Both gross and microscopic findings of lung tissue damage from pseudomonas pneumonia were less in vaccinated than in control animals. Thus, lipopolysaccharide pseudomonas vaccine appears to produce a local protective response in respiratory tissue against Pseudomonas.

Animals↗