Prospective study of serum staphylococcal antibodies in cystic fibrosis

High Prevalence of Staphylococcus aureus Enterotoxin Gene Cluster Superantigens in Cystic Fibrosis Clinical Isolates

BACKGROUND

Staphylococcus aureus is a highly prevalent respiratory pathogen in cystic fibrosis (CF). It is unclear how this organism establishes chronic infections in CF airways. We hypothesized that S. aureus isolates from patients with CF would share common virulence properties that enable chronic infection.

METHODS

77 S. aureus isolates were obtained from 45 de-identified patients with CF at the University of Iowa. We assessed isolates phenotypically and used genotyping assays to determine the presence or absence of 18 superantigens (SAgs).

RESULTS

We observed phenotypic diversity among S. aureus isolates from patients with CF. Genotypic analysis for SAgs revealed 79.8% of CF clinical isolates carried all six members of the enterotoxin gene cluster (EGC). MRSA and MSSA isolates had similar prevalence of SAgs. We additionally observed that EGC SAgs were prevalent in S. aureus isolated from two geographically distinct CF centers.

CONCLUSIONS

S. aureus SAgs belonging to the EGC are highly prevalent in CF clinical isolates. The greater prevalence in these SAgs in CF airway specimens compared to skin isolates suggests that these toxins confer selective advantage in the CF airway.

Host response to Staphylococcus aureus cytotoxins in children with cystic fibrosis

BACKGROUND

Staphylococcus aureus is one of the earliest bacterial pathogens to colonize the lungs of children with cystic fibrosis and is an important contributor to pulmonary exacerbations. The adaptive host response to S. aureus in cystic fibrosis remains inadequately defined and has important implications for pathogenesis and potential interventions. The objectives of this study were to determine the functional antibody response to select staphylococcal exotoxins (LukAB, alpha-hemolysin, and PVL) in children with cystic fibrosis and to evaluate the relationship of this response with pulmonary exacerbations.

METHODS

Fifty children with cystic fibrosis were enrolled and followed prospectively for 12months. Clinical characteristics and serologic profiles were assessed at routine visits and during pulmonary exacerbations, and functional antibody assessments were performed to measure neutralization of LukAB-mediated cytotoxicity.

RESULTS

For each antigen, geometric mean titers were significantly higher if S. aureus was detected at the time of exacerbation. For LukAB, geometric mean titers were significantly higher at exacerbation follow-up compared to titers during the exacerbation, consistent with expression during human disease, and the humoral response capably neutralized LukAB-mediated cytotoxicity. Moreover, the presence of a positive S. aureus culture during a pulmonary exacerbation was associated with 31-fold higher odds of having a LukA titer ≥1:160, suggesting potential diagnostic capability of this assay.

CONCLUSIONS

The leukotoxin LukAB is expressed by S. aureus and recognized by the human adaptive immune response in the setting of pulmonary infection in cystic fibrosis. Anti-LukAB antibodies were not only predictive of positive staphylococcal culture during exacerbation, but also functional in the neutralization of this toxin.

Levels of antibody against 11 Staphylococcus aureus antigens in a healthy population

Serum samples from 151 healthy individuals aged from 15 to 89 years were investigated by enzyme-linked immunosorbent assay (ELISA) for IgG levels against 11 different purified antigens from Staphylococcus aureus. Surface antigens, such as teichoic acid, clumping factors A and B, and bone sialoprotein binding protein, and extracellular proteins, such as alpha-toxin, lipase, enterotoxin A, toxic shock syndrome toxin, scalded-skin syndrome toxin, fibrinogen binding protein, and extracellular adherence protein, were used. The IgG values were analyzed in relation to the state of nasal carriage at the time of sampling. There was great individual variation in antibody levels in both young and elderly healthy subjects. Occurrence of S. aureus in the nares at the time of sampling was correlated with higher antibody levels, while elderly individuals over 65 years of age showed slightly lower levels than younger adults. More individuals than was expected from random probability calculations showed high antibody levels against several antigens, and more individuals than would be expected showed low levels against several antigens. Certain extracellular proteins had more often induced IgG levels of the same magnitude in the same individuals, indicating that among these individuals, there was a tendency to respond to certain antigens in the same way. Most individuals had circulating IgG antibodies to the 11 tested antigens, and some individuals had the tendency to be "good responders" to several antigens, while others were "poor responders." These findings constitute basic knowledge for the development of improved serological diagnostics, immune prophylaxis, individual prognosis tools, and therapy against invasive Staphylococcus aureus infections.

Usefulness of serum IgG4 in the diagnosis and follow up of autoimmune pancreatitis: A systematic literature review and meta-analysis

High circulating serum immunoglobulin G4 (IgG4) levels have been proposed as a marker of autoimmune pancreatitis (AIP). The aim of the present study was to review the data existing in the English literature on the usefulness of the IgG4 serum levels in the diagnosis and follow up of patients with AIP. A total of 159 patients with AIP and 1099 controls were described in seven selected papers reporting the usefulness of serum IgG4 in diagnosing AIP. In total, 304 controls had pancreatic cancer, 96 had autoimmune diseases, and the remaining 699 had other conditions. The summary receiver-operating characteristic curve analysis was carried out by means of Meta-DiSc open-access software. Serum IgG4 showed good accuracy in distinguishing between AIP and the overall controls, pancreatic cancer and other autoimmune diseases (area under the curve [+/- SE]: 0.920 +/- 0.073, 0.914 +/- 0.191, and 0.949 +/- 0.024, respectively). The studies analyzed showed significantly heterogeneous specificity values in each of the three analyses performed. The analysis of the four studies comparing AIP and pancreatic cancers also showed significantly heterogeneous values of sensitivities and odds ratios. Regarding the usefulness of IgG4 as a marker of efficacy of steroid treatment, a decrease in the serum concentrations of IgG4 was found in the four available studies. The serum IgG4 subclass is a good marker of AIP, and its determination should be included in the diagnostic workup of this disease. However, the heterogeneity of the studies published until now means that more studies are necessary in order to better evaluate the true accuracy of IgG4 in discriminating AIP versus other autoimmune diseases.

Bacterial colonisation with Xanthomonas maltophilia--a retrospective study in a cystic fibrosis patient population

Xanthomonas maltophilia was isolated from 25 of 150 patients with cystic fibrosis during a period of 10 years (1983-1992). Twelve patients harboured X. maltophilia chronically, i.e. repeatedly for more than 6 months. No predisposing factors for the colonisation could be identified by studying the clinical and laboratory data of the patients, including preceding and concurrent bacterial colonisation with other bacteria, antibacterial treatments, pulmonary function and biochemical markers. Up to 2 years after the chronic colonisation was established no clinical deterioration could be verified, but the patients with X. maltophilia generally had a worse lung function at the latest follow-up (2-7 years after colonisation) than controls colonised with Pseudomonas aeruginosa (p < 0.05). Our data imply that X. maltophilia is a pathogen and the colonisation appears to follow the same pattern as the colonisation by P. aeruginosa. The development of resistance to different antibiotics, as revealed by analysis of the inhibition zones, was related to antibacterial treatment courses. X. maltophilia showed reduced sensitivity to the most commonly used antibiotics, ceftazidime and tobramycin.

Antistaphylococcal antibodies in cystic fibrosis

Chronic colonization with Staphylococcus aureus is found in 40-50% of the sputum producing patients with cystic fibrosis treated at Stockholm's Cystic Fibrosis Center, Huddinge University Hospital. 30-40% of these patients had increased ELISA IgG antibody titres against teichoic acid and against alpha-toxin. About half of the number of patients showed increased antibody titres to either antigen during infection. Increased antibody titres against staphylococcal antigens were only found in less than or equal to 10% of patients not chronically colonized with S. aureus (no different from the normal population). The serum titres of antistaphylococcal antibodies were significantly higher in the chronically colonized patients (p less than 0.001). Patients who were also chronically harbouring Pseudomonas aeruginosa had the highest titres of both antibodies. The titres increased with clinical signs of infection and were normalized by antimicrobial chemotherapy. To conclude, the use of ELISA IgG antibodies may prove suitable for routine evaluation of the need for, and control of the efficacy of antistaphylococcal chemotherapy in cystic fibrosis.

Clinical significance of Staphylococcus aureus in cystic fibrosis

Staphylococcus aureus is usually the first bacterial pathogen detected in the respiratory secretions of patients with cystic fibrosis. This review briefly examines the characteristics of this host-parasite relationship in terms of current knowledge about the toxicity of the organism, mechanisms of respiratory tract injury, therapy and prevention. Recent evidence indicates that viral infection plays a role in the initial damage of the respiratory epithelial cells and staphylococcal colonization ensues. Affinity of staphylococcus for cystic fibrosis mucus, mucociliary abnormalities and unknown factors contribute to persistent colonization with this organism causing progressive pulmonary damage and possibly influencing Pseudomonas infection. Most of the evidence today indicates that aggressive antibiotic management directed against S. aureus is warranted in all stages of bronchopulmonary infection in cystic fibrosis. Future efforts to prevent colonization and the toxic and immunopathic consequences of staphylococcal infection are also important. One study is in progress that examines antibiotic prevention in the early stages of cystic fibrosis. Future investigations need to address other strategies including vaccines, antitoxins, anti-inflammatory agents, immunomodulators, and antibiotic regimens.

Staphylococcus aureus capsular types and antibody response to lung infection in patients with cystic fibrosis

Chronic respiratory tract infections caused by Staphylococcus aureus are common in patients with cystic fibrosis (CF). Recently, it was shown in a few CF patients that S. aureus isolates produce capsular polysaccharides (CPs). However, it is not known whether this is a common feature and whether an immune response to CPs in CF is detectable. Therefore, we examined 170 S. aureus isolates from CF patients and healthy individuals for production of CP types 5 and 8 by using monoclonal antibodies. We found that CP-producing staphylococcal isolates were randomly distributed among CF patients and healthy carriers. Eighty-five percent of all isolates produced CPs, 77% of which were type 8. Examination of one sputum sample by an immunofluorescence technique suggested that production of CPs is not an in vitro phenomenon. S. aureus isolates from various sites of a single person often yielded more than one CP type. A random distribution of S. aureus strains with CP type 5 or 8 from the skin and respiratory tracts of patients and from the skin of healthy individuals was found. Antibody response to CP types 5 and 8, measured by enzyme-linked immunosorbent assay, was not elevated in CF patients with chronic S. aureus lung infection in comparison with healthy carriers. On the contrary, in CF patients the ratios of antibodies to CP 8 were significantly lower (P less than 0.005; alpha = 0.025). The ratios of antibodies to CP types did not change when monitored longitudinally over several months. This study suggests that the production of CPs is a universal property of S. aureus and that infected CF patients do not have elevated ratios of antibodies to these antigens.