Detection of antibodies to Pseudomonas aeruginosa in serum and oral fluid from patients with cystic fibrosis

Culture independent markers of nontuberculous mycobacterial (NTM) lung infection and disease in the cystic fibrosis airway

Nontuberculous mycobacteria (NTM) are opportunistic pathogens that affect a relatively small but significant portion of the people with cystic fibrosis (CF), and may cause increased morbidity and mortality in this population. Cultures from the airway are the only test currently in clinical use for detecting NTM. Culture techniques used in clinical laboratories are insensitive and poorly suited for population screening or to follow progression of disease or treatment response. The lack of sensitive and quantitative markers of NTM in the airway impedes patient care and clinical trial design, and has limited our understanding of patterns of acquisition, latency and pathogenesis of disease. Culture-independent markers of NTM infection have the potential to overcome many of the limitations of standard NTM cultures, especially the very slow growth, inability to quantitate bacterial burden, and low sensitivity due to required decontamination procedures. A range of markers have been identified in sputum, saliva, breath, blood, urine, as well as radiographic studies. Proposed markers to detect presence of NTM or transition to NTM disease include bacterial cell wall products and DNA, as well as markers of host immune response such as immunoglobulins and the gene expression of circulating leukocytes. In all cases the sensitivity of culture-independent markers is greater than standard cultures; however, most do not discriminate between various NTM species. Thus, each marker may be best suited for a specific clinical application, or combined with other markers and traditional cultures to improve diagnosis and monitoring of treatment response.

Specificity of Immunoglobulin Response to Nontuberculous Mycobacteria Infection in People with Cystic Fibrosis

Nontuberculous mycobacteria (NTM) infections are increasingly prevalent in chronic lung diseases, including cystic fibrosis (CF). Mycobacterium abscessus is of particular concern due to relatively greater virulence and intrinsic antimicrobial resistance. Airway culture identification, the standard method for detecting pulmonary infection, is hindered by low sensitivity, long culture times, and reliance on sputum production or lavage. A culture-independent test for detecting NTM infection could complement, or replace, sputum culture, which is becoming more difficult to obtain with reduced sputum production by people with CF (pwCF) on highly effective modulator therapy. We describe an assay for the detection of plasma anti-M. abscessus antibodies of pwCF to antigens from M. abscessus lysates. Anti-M. abscessus IgG and IgA, but not IgM, discriminated with high specificity subjects infected with M. abscessus from those infected by M. avium complex, and from those with distant or no NTM infections. The IgG3 subclass predominated with minor contributions by other subclasses. Both aqueous and organic soluble antigens were recognized by plasma IgG. A validation cohort measuring IgG and IgG3 identified M. abscessus positive subjects, and elevated IgG was sustained over several years. These studies show the benefit of M. abscessus cell lysates to detect plasma IgG of subjects with CF and M. abscessus infections. Subclass analysis suggests that IgG3 is the predominant subtype in these subjects with chronic bacterial infections suggesting a defect in class maturation. Serodiagnosis could be useful to monitor M. abscessus group infections in chronic lung disease as an adjunct or alternative to culture. IMPORTANCE Lung infections with nontuberculous mycobacteria (NTM), and particularly Mycobacterium abscessus, a pathogen with high antibiotic resistance, are of great concern due to poor clinical outcomes and challenging detection in people with cystic fibrosis and other diseases. Standard detection methods are insensitive and increasingly difficult. We describe the measurement of NTM-specific antibodies from plasma to identify subjects infected with M. abscessus. The assay is sensitive and provides information on the immune response to NTM infections. This assay could be used to help identify subjects with NTM pulmonary infections and track disease progression, either alone or in conjunction with other tests.

Dissociation of systemic and mucosal autoimmunity in cystic fibrosis

BACKGROUND

Pseudomonas aeruginosa accounts for ~80% of cystic fibrosis (CF) airway infection. It shows a remarkable correlation with presence of autoantibody to bactericidal/permeability-increasing protein (BPI), which is not understood. In this study, we sought to better understand the characteristics of systemic and mucosal autoimmunity and their relation to humoral immunity to P. aeruginosa.

METHODS

Antibody titers and isotypes to BPI and P. aeruginosa were characterized in sera and bronchoalveolar lavage (BAL) of adult and pediatric CF patients (n = 131), by ELISA and/or immunoblot.

RESULTS

Serum BPI autoantibodies were common (~43%) in adult while rare (≪5%) in pediatric (≤18 yrs) CF patients. Serum BPI IgG autoantibodies were of high avidity and strongly correlated with anti-P. aeruginosa IgG responses. A parallel relationship was observed with IgA, but not IgG, responses in adult and pediatric CF patient in the BAL. Thus, BAL IgA anti-BPI antibodies were independent of age and correlated with the presence of BPI cleavage in BAL.

CONCLUSIONS

IgG and IgA autoreactivity to BPI in CF patients was demonstrated in serum and BAL, respectively, and correlated with the isotype of the antibody response to P. aeruginosa. The co-occurrence of anti-BPI and anti-P. aeruginosa IgA in the BAL, but not serum, of pediatric CF patients suggests that BPI tolerance is broken in the P. aeruginosa-infected airway and that serologic IgG autoantibodies are later induced, potentially through a separate pathway. The relationship between P. aeruginosa, BPI cleavage, and IgA autoantibodies in the BAL suggests a role for cryptic epitope generation in the breaking of tolerance.

Graphene Oxide Quantum Dots Assisted Construction of Fluorescent Aptasensor for Rapid Detection of Pseudomonas aeruginosa in Food Samples

We engineered an ingenious fluorescent aptasensor for detection of Pseudomonas aeruginosa ( P. aeruginosa) according to the DNA hybridization and fluorescence resonance energy transfer. In the absence of target bacteria, 5-carboxyfluorescein-labeled complementary DNA (FAM-cDNA) hybridizes with the partial sequences of aptamer and the fluorescence of FAM can be quenched by graphene oxide quantum dots (GOQDs). Upon the addition of target bacteria, the aptamer as a biorecognition element is bound with P. aeruginosa specifically. FAM-cDNA prefers to hybridize with the aptamer, resulting in the desorption of FAM-cDNA from GOQDs, thus recovering the fluorescence of FAM. The aptasensor shows a wide linear response to P. aeruginosa in the concentration range of 1.28 × 10³-2.00 × 10⁷ cfu/mL with acceptable selectivity. The detection limit is 100 cfu/mL. The whole process can be finished in 2 h. Moreover, the platform is successfully applied to detect P. aeruginosa in drinking water, orange juice, and popsicle samples.

Detection methods for Pseudomonas aeruginosa: history and future perspective

The current review summarized and analyzed the development of detection techniques forPseudomonas aeruginosaover the past 50 years.

Efficacy of species-specific protein antibiotics in a murine model of acute Pseudomonas aeruginosa lung infection

Protein antibiotics, known as bacteriocins, are widely produced by bacteria for intraspecies competition. The potency and targeted action of bacteriocins suggests that they could be developed into clinically useful antibiotics against highly drug resistant Gram-negative pathogens for which there are few therapeutic options. Here we show that Pseudomonas aeruginosa specific bacteriocins, known as pyocins, show strong efficacy in a murine model of P. aeruginosa lung infection, with the concentration of pyocin S5 required to afford protection from a lethal infection at least 100-fold lower than the most commonly used inhaled antibiotic tobramycin. Additionally, pyocins are stable in the lung, poorly immunogenic at high concentrations and efficacy is maintained in the presence of pyocin specific antibodies after repeated pyocin administration. Bacteriocin encoding genes are frequently found in microbial genomes and could therefore offer a ready supply of highly targeted and potent antibiotics active against problematic Gram-negative pathogens.

Discovery, characterization and in vivo activity of pyocin SD2, a protein antibiotic from Pseudomonas aeruginosa

Increasing rates of antibiotic resistance among Gram-negative pathogens such as Pseudomonas aeruginosa means alternative approaches to antibiotic development are urgently required. Pyocins, produced by P. aeruginosa for intraspecies competition, are highly potent protein antibiotics known to actively translocate across the outer membrane of P. aeruginosa. Understanding and exploiting the mechanisms by which pyocins target, penetrate and kill P. aeruginosa is a promising approach to antibiotic development. In this work we show the therapeutic potential of a newly identified tRNase pyocin, pyocin SD2, by demonstrating its activity in vivo in a murine model of P. aeruginosa lung infection. In addition, we propose a mechanism of cell targeting and translocation for pyocin SD2 across the P. aeruginosa outer membrane. Pyocin SD2 is concentrated at the cell surface, via binding to the common polysaccharide antigen (CPA) of P. aeruginosa lipopolysaccharide (LPS), from where it can efficiently locate its outer membrane receptor FpvAI. This strategy of utilizing both the CPA and a protein receptor for cell targeting is common among pyocins as we show that pyocins S2, S5 and SD3 also bind to the CPA. Additional data indicate a key role for an unstructured N-terminal region of pyocin SD2 in the subsequent translocation of the pyocin into the cell. These results greatly improve our understanding of how pyocins target and translocate across the outer membrane of P. aeruginosa. This knowledge could be useful for the development of novel anti-pseudomonal therapeutics and will also support the development of pyocin SD2 as a therapeutic in its own right.

Single-Nucleotide Polymorphisms Found in the migA and wbpX Glycosyltransferase Genes Account for the Intrinsic Lipopolysaccharide Defects Exhibited by Pseudomonas aeruginosa PA14

Pseudomonas aeruginosa PA14 is widely used by researchers in many laboratories because of its enhanced virulence over strain PAO1 in a wide range of hosts. Although lipopolysaccharide (LPS) is an important virulence factor of all P. aeruginosa strains, the LPS of PA14 has not been characterized fully. A recent study showed that the structure of its O-specific antigen (OSA) belongs to serotype O19. We found that the OSA gene cluster of PA14 shares ∼99% identity with those of the O10/O19 group. These two serotypes share the same O-unit structure, except for an O-acetyl substitution in one of the sugars in O10. Here we showed that both PA14 and O19 LPS cross-reacted with the O10-specific monoclonal antibody MF76-2 in Western blots. Analysis by SDS-PAGE and silver staining showed that PA14 LPS exhibited modal chain lengths that were different from those of O19 LPS, in that only "very long" and "short" chain lengths were observed, while "medium" and "long" chain lengths were not detected. Two other novel observations included the lack of the uncapped core oligosaccharide epitope and of common polysaccharide antigen (CPA) LPS. The lack of the uncapped core oligosaccharide was caused by point mutations in the glycosyltransferase gene migA, while the CPA-negative phenotype was correlated with a single amino acid substitution, G20R, in the glycosyltransferase WbpX. Additionally, we showed that restoring CPA biosynthesis in PA14 significantly stimulated mature biofilm formation after 72 h, while outer membrane vesicle production was not affected.

IMPORTANCE

P. aeruginosa PA14 is a clinical isolate that has become an important reference strain used by many researchers worldwide. LPS of PA14 has not been characterized fully, and hence, confusion about its phenotype exists in the literature. In the present study, we set out to characterize the O-specific antigen (OSA), the common polysaccharide antigen (CPA), and the core oligosaccharide produced by PA14. We present evidence that PA14 produces an LPS consisting of "very-long-chain" and some "short-chain" OSA belonging to the O19 serotype but is devoid of CPA and the uncapped core oligosaccharide epitope. These intrinsic defects in PA14 LPS were due to single-nucleotide polymorphisms (SNPs) in the genes that encode glycosyltransferases in the corresponding biosynthesis pathways. Since sugars in CPA and the uncapped core are receptors for different bacteriocins and pyocins, the lack of CPA and an intact core may contribute to the increased virulence of PA14. Restoring CPA production in PA14 was found to stimulate mature biofilm formation.

Pseudomonas aeruginosa infection in patients with cystic fibrosis: scientific evidence regarding clinical impact, diagnosis, and treatment

Evidence-based techniques have been increasingly used in the creation of clinical guidelines and the development of recommendations for medical practice. The use of levels of evidence allows the reader to identify the quality of scientific information that supports the recommendations made by experts. The objective of this review was to address current concepts related to the clinical impact, diagnosis, and treatment of Pseudomonas aeruginosa infections in patients with cystic fibrosis. For the preparation of this review, the authors defined a group of questions that would be answered in accordance with the principles of PICO-an acronym based on questions regarding the Patients of interest, Intervention being studied, Comparison of the intervention, and Outcome of interest. For each question, a structured review of the literature was performed using the Medline database in order to identify the studies with the methodological design most appropriate to answering the question. The questions were designed so that each of the authors could write a response. A first draft was prepared and discussed by the group. Recommendations were then made on the basis of the level of scientific evidence, in accordance with the classification system devised by the Oxford Centre for Evidence-Based Medicine, as well as the level of agreement among the members of the group.

Inflammatory and immunological biomarkers are not related to survival in adults with Cystic Fibrosis

BACKGROUND

Chronic Pseudomonas aeruginosa pulmonary infection is associated with a decline in lung function and reduced survival in people with Cystic Fibrosis (CF). Damaging inflammatory and immunological mediators released in the lungs can be used as markers of chronic infection, inflammation and lung tissue damage.

METHODS

Clinical samples were collected from CF patients and healthy controls. Serum IgG and IgA anti-Pseudomonas antibodies, sputum IL-8 and TNFα, plasma IL-6 and urine TNFr1 were measured by ELISA. Sputum neutrophil elastase (NE), cathepsin S and cathepsin B were measured by spectrophotometric and fluorogenic assays. The relationship between IgG and IgA, inflammatory mediators and long-term survival was determined.

RESULTS

IgG and IL-6 positively correlated with mortality. However, multivariate analysis demonstrated that after adjusting for FEV(1), IgG was not independently related to mortality. A relationship was observed between IgG and IL-6, TNFα, TNFr1 and between IgA and IL8, cathepsin S and cathepsin B.

CONCLUSIONS

These data indicate that biomarkers of inflammation are not independent predictors of survival in people with CF.

Pseudomonas aeruginosa bacteremia and prostatitis in a patient with cystic fibrosis

Patients with cystic fibrosis (CF) commonly suffer chronic respiratory infections, although systemic dissemination is relatively rare. Acute bacterial prostatitis presents dramatically and is believed to be mostly caused by local migration (with or without instrumentation) of the lower urinary tract and presents with a predictable microbial etiology. We report a case of a 26-year-old man presenting with acute Pseudomonas aeruginosa bacterial prostatitis due to hematogenous propagation from a chronic pulmonary infection.

Genetic and Functional Diversity of Pseudomonas aeruginosa Lipopolysaccharide

Lipopolysccharide (LPS) is an integral component of the Pseudomonas aeruginosa cell envelope, occupying the outer leaflet of the outer membrane in this Gram-negative opportunistic pathogen. It is important for bacterium-host interactions and has been shown to be a major virulence factor for this organism. Structurally, P. aeruginosa LPS is composed of three domains, namely, lipid A, core oligosaccharide, and the distal O antigen (O-Ag). Most P. aeruginosa strains produce two distinct forms of O-Ag, one a homopolymer of D-rhamnose that is a common polysaccharide antigen (CPA, formerly termed A band), and the other a heteropolymer of three to five distinct (and often unique dideoxy) sugars in its repeat units, known as O-specific antigen (OSA, formerly termed B band). Compositional differences in the O units among the OSA from different strains form the basis of the International Antigenic Typing Scheme for classification via serotyping of different strains of P. aeruginosa. The focus of this review is to provide state-of-the-art knowledge on the genetic and resultant functional diversity of LPS produced by P. aeruginosa. The underlying factors contributing to this diversity will be thoroughly discussed and presented in the context of its contributions to host-pathogen interactions and the control/prevention of infection.