Natural antibodies in Pseudomonas aeruginosa infections

Studying 347 sera of 49 patients suffering from Pseudomonas aeruginosa infection the mean titre value (MTV) calculated from the exponent of the binary logarithm of natural antibody (NA) titres, was found suitable to characterize the humoral immune status. As long as the organism is in equilibrium with the infection, the NA level rises. In septic shock, before death or at the development of a massive infection, the NA titre decreases rapidly. The decrease may be due partly to the permeability increasing effect of endotoxin and antigen-antibody reactions exerted on the capillaries. Consequently, in the most severe phase of sepsis, when bacteria enter the circulation less NA is available to fight against them. This might be a cause of the still very high lethality of septic shock due to Gram-negative bacteria. Finally, when applying the MTV one always has to consider that despite its advantages it gives less information than the Backhausz immunogram.     

Cooperation and virulence in acute Pseudomonas aeruginosa infections

Background  

Efficient host exploitation by parasites is frequently likely to depend on cooperative behaviour. Under these conditions, mixed-strain infections are predicted to show lower virulence (host mortality) than are single-clone infections, due to competition favouring non-contributing social 'cheats' whose presence will reduce within-host growth. We tested this hypothesis using the cooperative production of iron-scavenging siderophores by the pathogenic bacterium Pseudomonas aeruginosa in an insect host.     

Therapeutic approaches for combating Pseudomonas aeruginosa infections

Pseudomonas aeruginosa is an opportunistic pathogen responsible for acute hospital-acquired infections. This review described various therapeutic approaches to treat infections caused by P. aeruginosa, including conventional therapy, novel antibiotic treatments and treatments other than antibiotics. Most of the developments are still in research that will provide novel treatment options in future.     

Pseudomonas aeruginosa infections are prevented in cystic fibrosis patients by avian antibodies binding Pseudomonas aeruginosa flagellin

Pseudomonas aeruginosa (PA) is the main cause of morbidity and mortality in cystic fibrosis (CF) patients. CF patients with chronic PA infections have a more rapid deterioration of their lung function and the bacteria become impossible to eradicate from the lungs. Antibiotic resistance among PA strains in CF patients is steadily increasing. Specific chicken (IgY) antibodies against PA have been shown to have potential to prevent PA infections in CF. Anti-Pseudomonas IgY reduces PA adhesion to epithelia, but the mechanism has not been fully elucidated. To gain further insight into the prophylactic effect of these antibodies, the immunoreactivity was investigated by 2D electrophoresis of PA strains, immunoblotting and MALDI-TOF-MS. To confirm the identity of the proteins, the tryptic peptides were analyzed by MALDI-TOF-MS to accurately measure their monoisotopic masses as well as determine their amino acid sequences. In order to facilitate fragmentation of the peptides they were N-terminally or C-terminally labeled. Several strains were investigated and anti-Pseudomonas IgY was immunoreactive against all of these strains, which strengthens its potential as a prophylactic treatment against PA. Flagellin was identified as the major antigen. Flagellin is the main protein of the flagella and is crucial for establishing infections in hosts as well as being involved in PA chemotaxis, motility, adhesion and inflammation. Furthermore, secreted flagellin elicits an inflammatory response. In conclusion, anti-Pseudomonas IgY binds flagellin, which may prevent PA infections in CF patients by hindering host invasion.     

The Pseudomonas aeruginosa opportunistic pathogen and human infections

Pseudomonas aeruginosa, a Gram-negative environmental species and an opportunistic microorganism, establishes itself in vulnerable patients, such as those with cystic fibrosis or hospitalized in intensive care units. It has become a major cause of nosocomial infections worldwide (about 10% of all such infections in most European Union hospitals) and a serious threat to Public Health. The overuse and misuse of antibiotics have also led to the selection of resistant strains against which very few therapeutic options exist. How an environmental species can cause human infections remains a key question that still needs elucidation despite the incredibly high progress that has been made in the P. aeruginosa biology over the past decades. The workshop belonging to Current trends in Biomedicine series, which was held under the sponsorship of the Universidad International de Andalucia between the 8th and the 10th November 2010 brought in the most recent advances in the environmental life of P. aeruginosa, the human P. aeruginosa infections, the new animal models to study Pseudomonas infections, the new genetic aspects including metabolomics, genomics and bioinformatics and the community lifestyle named biofilm that accounts for P. aeruginosa persistence in humans. This workshop organized by Soeren Molin (Danemark), Juan-Luis Ramos (Spain) and Sophie de Bentzmann (France) gathered 46 researchers coming from 11 European and American countries in a small format and was hosted in the 'Sede Antonio Machado' in Baeza. It was organized in seven sessions covering animal models for P. aeruginosa pathogenesis, resistance to drugs, regulatory potency including small RNA, two component systems, extracytoplasmic function sigma factors and trancriptional regulators, new therapies emerging from dissection of molecular mechanisms, and evolutionary mechanisms of P. aeruginosa strains in patients.     

Comparison of some adhesive properties of Pseudomonas aeruginosa strains isolated from respiratory and urinary tract infections

The aim of the paper was the comparison of adhesive properties concerning pathogenic potential of P. aeruginosa strains isolated from the patients with respiratory tract infections and from the patients with urinary tract infections. It was stated that P. aeruginosa strains had no haemagglutinating properties when cultured on a solid medium. Bacteria cultured in a liquid medium showed an increase of these properties in 48 h cultures as compared with 24 h cultures. They were not sensitive to heating. The haemagglutinating properties of the most strains were inhibited by D-mannose. These results seem to suggest that in P. aeruginosa strains fimbriae play an important role in adhesion. On the other hand, the mechanism of adhesion is not uniform as shows mannose-sensitivity of some strains and its lack in the other haemagglutinating strains. The most effective agglutination of human erythrocytes seems to be caused by the species specificity of the individual strains isolated from humans. The higher attachment of P. aeruginosa strains isolated from the urinary tract infections than those from respiratory tract infections to "Vero" cells suggests that these two strains populations may differ in their pathogenic potential to various tissues.     

Bacteriophages for the treatment of Pseudomonas aeruginosa infections

Bacteriophages were first identified in 1915 and were used as antimicrobial agents from 1919 onwards. Despite apparent successes and widespread application, early users did not understand the nature of these agents and their efficacy remained controversial. As a result, they were replaced in the west by chemical antibiotics once these became available. However, bacteriophages remained a common therapeutic approach in parts of Eastern Europe where they are still in use. Increasing levels of antibiotic-resistant bacterial infections are now driving demand for novel therapeutic approaches. In cases where antibiotic options are limited or nonexistent, the pressure for new agents is greatest. One of the most prominent areas of concern is multidrug-resistant Gram-negative bacteria. Pseudomonas aeruginosa is a prominent member of this class and is the cause of damaging infections that can be resistant to successful treatment with conventional antibiotics. At the same time, it exhibits a number of properties that make it a suitable target for bacteriophage-based approaches, including growth in biofilms that can hydrolyse following phage infection. Pseudomonas aeruginosa provides a striking example of an infection where clinical need and the availability of a practical therapy coincide.     

Importance of flagella in acute and chronic Pseudomonas aeruginosa infections

Pseudomonas aeruginosa is an environmental microorganism and a causative agent of diverse acute and chronic, biofilm-associated infections. Advancing research-based knowledge on its adaptation to conditions within the human host is bound to reveal novel strategies and targets for therapeutic intervention. Here, we investigated the traits that P. aeruginosa PA14 as well as a virulence attenuated ΔlasR mutant need to survive in selected murine infection models. Experimentally, the genetic programs that the bacteria use to adapt to biofilm-associated versus acute infections were dissected by passaging transposon mutant libraries through mouse lungs (acute) or mouse tumours (biofilm-infection). Adaptive metabolic changes of P. aeruginosa were generally required during both infection processes. Counter-selection against flagella expression was observed during acute lung infections. Obviously, avoidance of flagella-mediated activation of host immunity is advantageous for the wildtype bacteria. For the ΔlasR mutant, loss of flagella did not confer a selective advantage. Apparently, other pathogenesis mechanisms are active in this virulence attenuated strain. In contrast, the infective process of P. aeruginosa in the chronic biofilm model apparently required expression of flagellin. Together, our findings imply that the host immune reactions against the infectious agent are very decisive for acuteness and duration of the infectious disease. They direct disease outcome.     

DNA vaccines against chronic lung infections by Pseudomonas aeruginosa

Vaccines containing outer membrane protein F (OprF) of Pseudomonas aeruginosa are effective in reducing lesion severity in a mouse pulmonary chronic infection model. One OprF-based vaccine, called F/I, contains carboxy oprF sequences fused to oprI in an expression vector. When delivered three times biolistically by gene gun, the F/I vaccine induces protection that is antibody-mediated in outbred mice. To demonstrate the role of F/I-induced antibody-mediated immunity, B-cell-deficient [B(-)] and B-cell-intact [B(+)] mice were immunized with F/I, challenged with Pseudomonas, and examined for lesion severity. As expected, F/I-immunized B(+) mice had fewer and less severe lesions than vector-immunized B(+) mice. However, surprisingly, F/I- and vector-immunized B(-) mice were equally protected to levels similar to F/I-immunized B(+) mice. Examination of immune cell populations and cytokine levels indicated a relative increase in the quantity of CD3+ T-lymphocytes in vector- or F/I-immunized and challenged B(-) mice compared to B(+) mice. These data indicate the protective role played by cell-mediated immunity in B(-) mice, which supports our hypothesis that cell-mediated immunity can play an important role in protection against P. aeruginosa.     

Membrane-bound respiratory chain of Pseudomonas aeruginosa grown aerobically.

The electron transport chain of the gram-negative bacterium Pseudomonas aeruginosa, grown aerobically, contained a number of primary dehydrogenases and respiratory components (soluble flavin, bound flavin, coenzyme Q9, heme b, heme c, and cytochrome o) in membrane particles of the organism. Cytochrome o, about 50% of the b-type cytochrome, seemed to function as a terminal oxidase in the respiratory chain. The electron transport chain of P. aeruginosa grown aerobically was suggested to be lined up in order of primary dehydrogenase, b, c1, c, o, and oxygen.     

Comparative study of the biological characteristics of mucoid and non-mucoid Pseudomonas aeruginosa strains isolated from chronic respiratory infections

Morphological, culture and enzymatic characteristics, as well as virulence, susceptibility to antimicrobial agents and epidemiological markers, were studied for 100 mucoid and 100 non-mucoid Ps. aeruginosa strains isolated from chronic respiratory infections. For 10 mucoid and 10 non-mucoid strains was performed the active protection test in mice, both with inactivated germs (10(9) germs), and LPS extracted by Westphal method. It was ascertained that mucoid Ps. aeruginosa strains differ from non-mucoid strains by the slow growth on culture media, more reduced proteolytic activity (81% as compared to 99%), slow oxidation of carbohydrates (5-7 days), reduced virulence in mice (8%) or avirulence (92%), higher sensitivity to some antibiotics (amikacin, dibekacin, ticarcillin, tetracycline, cefotaxime, ceftriaxone), lysoresistance (74%) and polyagglutinability (67%). The mucoid strains ensure a reduced active protection in mice, 70% of strains did not protect the mice against the infection with virulent homologous strains, while the non-mucoid strains ensured 80%-100% protection.     

Drosophila melanogaster as an animal model for the study of Pseudomonas aeruginosa biofilm infections in vivo

Pseudomonas aeruginosa is an opportunistic pathogen capable of causing both acute and chronic infections in susceptible hosts. Chronic P. aeruginosa infections are thought to be caused by bacterial biofilms. Biofilms are highly structured, multicellular, microbial communities encased in an extracellular matrix that enable long-term survival in the host. The aim of this research was to develop an animal model that would allow an in vivo study of P. aeruginosa biofilm infections in a Drosophila melanogaster host. At 24 h post oral infection of Drosophila, P. aeruginosa biofilms localized to and were visualized in dissected Drosophila crops. These biofilms had a characteristic aggregate structure and an extracellular matrix composed of DNA and exopolysaccharide. P. aeruginosa cells recovered from in vivo grown biofilms had increased antibiotic resistance relative to planktonically grown cells. In vivo, biofilm formation was dependent on expression of the pel exopolysaccharide genes, as a pelB::lux mutant failed to form biofilms. The pelB::lux mutant was significantly more virulent than PAO1, while a hyperbiofilm strain (PAZHI3) demonstrated significantly less virulence than PAO1, as indicated by survival of infected flies at day 14 postinfection. Biofilm formation, by strains PAO1 and PAZHI3, in the crop was associated with induction of diptericin, cecropin A1 and drosomycin antimicrobial peptide gene expression 24 h postinfection. In contrast, infection with the non-biofilm forming strain pelB::lux resulted in decreased AMP gene expression in the fly. In summary, these results provide novel insights into host-pathogen interactions during P. aeruginosa oral infection of Drosophila and highlight the use of Drosophila as an infection model that permits the study of P. aeruginosa biofilms in vivo.     

Pseudomonas aeruginosa infections associated with use of contaminated medicaments.

Pseudomonas aeruginosa was recovered from three hospital-prepared medicaments being used on the wards. Sixty-six patients were studied to observe the effect of using these contaminated medicaments. Psaeruginosa was recovered from 29 patients; in five the strains recovered bore a close resemblance to strains previously isolated from the contaminated medicaments.     

Epidemiology of Pseudomonas aeruginosa infections investigated by pyocin typing.

All strains of Pseudomonas aeruginosa isolated in a large Canadian hospital over a 3-year period were typed by their pyocin production. Smaller collections of P. aeruginosa from other hospitals were also typed. Almost 3000 strains were examined. The typing method did not require use of complex reagents and was successful in subdividing P. aeruginosa into numerous types. No single type was restricted to infections of one particular kind. Infections of all kinds were associated with a wide variety of pyocin types. Extensive crossinfection with one particular pyocin type was observed only in urinary infection of patients with urologic disorders. The four pyocin types that were most frequent in our entire series have been reported as the commonest types causing infections in many other parts of the world.     

Immunological studies of an artificial antigen with specificity of a common polysaccharide antigen of Pseudomonas aeruginosa

Abstract Synthetic d -rhamnan, with the structure of Pseudomonas aeruginosa common polysaccharide antigen (CPA), was conjugated with BSA. The artificial antigen obtained, and the natural antigens, lipopolysaccharides (LPS) of P. aeruginosa and Pseudomonas cerasi with rhamnan chains of the same structure, were studied by ELISA with rabbit antibodies to the d -rhamnan-BSA conjugate and to the P. cerasi O-antigen. Immunological relations between the LPS of P. aeruginosa and P. cerasi determined by CPA as well as between these LPS and d -rhamnan-BSA were revealed by ELISA. O-antiserum to P. cerasi possesses protective activity in the mouse passive protection test when mice are challenged with some P. aeruginosa strains; the antiserum to the d -rhamnan-BSA does not possess protective activity in mice.