Moraxella catarrhalis-specific Th1 cells in BAL fluids of chronic obstructive pulmonary disease patients

In chronic obstructive pulmonary disease (COPD) patients airway mucosa is infiltrated by macrophages and T lymphocytes, potentially reactive to pathogens. We studied the antigen-specificity and the effector functions of in vivo activated T lymphocytes isolated from BAL (Bronchoalveolar lavage) of 5 Moraxella catarrhalis (Mc)-infected and 5 Mc-non-infected COPD patients. Mc-specific T cells were detected only in BAL or peripheral blood of Moraxella catarrhalis-infected patients. The majority of BAL Mc-specific T cells expressed the T helper type 1 (Th1) cytokine profile with high cytotoxic and pro-apoptotic activity. Upon antigen stimulation, all Mc-specific T clones were able to help the immunoglobulin production by autologous B cells and the MMP (Matrix MetalloProteinase)-12 activity by monocytes. Our results suggest a role for Th1-driven response to Moraxella catarrhalis in the genesis of COPD.

Natural materno-fetal transfer of antibodies to PspA and to PsaA

PspA and PsaA are Streptococcus pneumoniae surface proteins and potential pneumococcal vaccine antigens. The aim of this study was to characterize the transplacental transfer of antibodies to PspA and to PsaA. Paired mother and cord blood sera were obtained at delivery from 28 women. Concentrations of antibodies against PspA, PsaA, tetanus toxoid (vaccine-induced antibodies) and P6-outer membrane protein (OMP) of nontypeable Haemophilus influenzae were determined by ELISA. Antibodies to PspA of the IgG, IgG1 and IgG2 antibodies were also determined. The geometric mean percentage (GM%) of the paired infant:mother antibody were calculated.

RESULTS

The GM% of the infant:mother antibody concentrations against PspA, PsaA and P6-OMP antibodies were 64.7% (3.3 micro g/ml in infants vs. 5.1 micro g/ml in mothers), 50.4% (6.8 micro g/ml vs. 13.5 micro g/ml) and 66.7% (5.6 micro g/ml vs. 8.4 micro g/ml), respectively; the GM% of antibodies against tetanus toxoid was 104.5% (4.6 micro g/ml vs. 4.4 micro g/ml). Transplacental transfer of IgG1 was more efficient than that of IgG2 (approximately 120%vs. 65%). A transplacental transfer of antibodies to PspA and to PsaA exist. Moreover, these data suggest an active placental transfer of IgG1 antibodies to PspA since the concentration of these antibodies were consistently higher in cord sera than in the mother's sera.

Cancer cachexia is mediated in part by the induction of IL-6-like cytokines from the spleen

The development of cancer cachexia has been linked to cytokines related to interleukin6 (IL-6). We examined the kinetics of IL-6, IL-11, oncostatinM (OSM) and leukaemia inhibitory factor (LIF) induction in the splenocytes of tumour-bearing mice. Using a lung carcinoma line, which grows in C57BL/6J mice, we observed that when the tumour grew and cachexia was observed, the splenocytes produced IL-6, IL-11, and OSM, but not LIF. Cytokine expression was observed within 1 week (day 3 for IL-6 and IL-11, and day 1 for OSM) of administration of tumour cells, and was observed in splenocytes without tumour metastases to the spleen. Cytokine expression preceded cachexia (determined by changes in serum triglyceride levels and decrease in epididymal fat-pad weights) development by over 1 week. Exogenous administration of IL-11 resulted in the accelerated onset of cachexia, compared to control protein treatment, but without an effect on the tumour burden. In vivo treatment with a neutralizing dose of anti-OSM antibody inhibited the triglyceride dysregulation only until the synthesis of IL-6 and IL-11 began in the spleen (day 3). Afterward, IL-6 and IL-11 induced lipid catabolism in the absence of functional OSM. We conclude from the data described above that cachexia developed due to a systemic cytokine response induced by a tumour burden, and that IL-6-like cytokines contributed independently to lipid hypercatabolism in the aetiology of cancer cachexia.

Nontypeable Haemophilus influenzae in the lower respiratory tract of patients with chronic bronchitis

The frequency of colonization and intracellular localization of nontypeable Haemophilus influenzae (NTHi) in the lower respiratory tract was determined in healthy adults and in clinically stable and acutely ill chronic bronchitis (CB) patients. NTHi was recovered from bronchial wash or bronchial brush specimens in 6 of 23 (26%) stable CB patients and in 1 of 15 (7%) CB patients with a respiratory exacerbation. No NTHi (0 of 26) was recovered from lower tract specimens of healthy adults undergoing anesthesia for elective surgery. Molecular typing of NTHi strains revealed that five of nine patients with stable CB had different strains in upper respiratory tract and bronchial wash/brush specimens collected simultaneously. Four stable patients with CB had different strains recovered on repeat bronchoscopy. These results demonstrate the frequent colonization of the lower airways of stable CB patients with multiple strains of NTHi. Bronchial biopsies also were examined for intracellular NTHi by in situ hybridization and immunofluorescence microscopy. Intracellular NTHi were found in 0 of 7 healthy adults, 8 of 24 patients with clinically stable CB, and 13 of 15 acutely ill CB patients. This observation suggests a role for intracellular infection by NTHi in the pathogenesis of exacerbations of CB.

Molecular typing of paired bacterial isolates from the adenoid and lateral wall of the nose in children undergoing adenoidectomy: implications in acute rhinosinusitis

OBJECTIVE

Recent studies have suggested that the origin of bacteria that enter the lateral wall of the nose and paranasal sinuses arise from the nasopharynx. The purpose of this study was to compare the molecular biological profiles of potential pathogens found in the nasopharynx and lateral wall of the nose concomittantly in children undergoing surgery for upper respiratory tract disease.

STUDY DESIGN AND SETTING

Fifty-two children undergoing adenoidectomy for either tonsillectomy or adenoidectomy (hypertrophy) or otitis media with effusion were studied. Bacterial cultures were taken from the crypts of the adenoids and from the lateral wall of the nose under endoscopic control after sterilization of the vestibule and inferior turbinate. Routine cultures of these areas were performed in the bacteriology laboratory of the Children's Hospital of Buffalo.

RESULTS

Bacterial pathogens were isolated from 79% of adenoids and 46% of lateral walls of the nose. Molecular typing of pairs of nontypable Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis revealed that in 16 of 18 pairs (89%) the identical strain was present in both sites simultaneously.

CONCLUSIONS

These results support the concept that when potential bacterial pathogens that may cause acute bacterial rhinosinusitis are found concomitantly in the nasopharynx and lateral wall of the nose, they are usually identical.

Activation of NF-kappa B by nontypeable Hemophilus influenzae is mediated by toll-like receptor 2-TAK1-dependent NIK-IKK alpha /beta-I kappa B alpha and MKK3/6-p38 MAP kinase signaling pathways in epithelial cells

Nontypeable Hemophilus influenzae (NTHi) is an important human pathogen in both children and adults. In children, it causes otitis media, the most common childhood infection and the leading cause of conductive hearing loss in the United States. In adults, it causes lower respiratory tract infections in the setting of chronic obstructive pulmonary disease, the fourth leading cause of death in the United States. The molecular mechanisms underlying the pathogenesis of NTHi-induced infections remain undefined, but they may involve activation of NF-kappa B, a transcriptional activator of multiple host defense genes involved in immune and inflammatory responses. Here, we show that NTHi strongly activates NF-kappa B in human epithelial cells via two distinct signaling pathways, NF-kappa B translocation-dependent and -independent pathways. The NF-kappa B translocation-dependent pathway involves activation of NF-kappa B inducing kinase (NIK)--IKK alpha/beta complex leading to I kappa B alpha phosphorylation and degradation, whereas the NF-kappa B translocation-independent pathway involves activation of MKK3/6--p38 mitogen-activated protein (MAP) kinase pathway. Bifurcation of NTHi-induced NIK-IKK alpha/beta-I kappa B alpha and MKK3/6--p38 MAP kinase pathways may occur at transforming growth factor-beta activated kinase 1 (TAK1). Furthermore, we show that toll-like receptor 2 (TLR2) is required for NTHi-induced NF-kappa B activation. In addition, several key inflammatory mediators including IL-1 beta, IL-8, and tumor necrosis factor-alpha are up-regulated by NTHi. Finally, P6, a 16-kDa lipoprotein highly conserved in the outer membrane of all NTHi and H. influenzae type b strains, appears to also activate NF-kappa B via similar signaling pathways. Taken together, our results demonstrate that NTHi activates NF-kappa B via TLR2-TAK1-dependent NIK--IKK alpha/beta-I kappa B alpha and MKK3/6--p38 MAP kinase signaling pathways. These studies may bring new insights into molecular pathogenesis of NTHi-induced infections and open up new therapeutic targets for these diseases.

Conservation of outer membrane protein E among strains of Moraxella catarrhalis

Outer membrane protein E (OMP E) is a 50-kDa protein of Moraxella catarrhalis which has several features that suggest that the protein may be an effective vaccine antigen. To assess the conservation of OMP E among strains of M. catarrhalis, 22 isolates were studied with eight monoclonal antibodies which recognize epitopes on different regions of the protein. Eighteen of 22 strains were reactive with all eight antibodies. The sequences of ompE from 16 strains of M. catarrhalis were determined, including the 4 strains which were nonreactive with selected monoclonal antibodies. Analysis of sequences indicate a high degree of conservation among strains, with sequence differences clustered in limited regions of the gene. To assess the stability of ompE during colonization of the human respiratory tract, the sequences of ompE of isolates collected from patients colonized with the same strain for 3 to 9 months were determined. The sequences remained unchanged. These results indicate that OMP E is highly conserved among strains of M. catarrhalis, and preliminary studies indicate that the gene which encodes OMP E remains stable during colonization of the human respiratory tract.

Bacterial infection in chronic obstructive pulmonary disease in 2000: a state-of-the-art review

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States. The precise role of bacterial infection in the course and pathogenesis of COPD has been a source of controversy for decades. Chronic bacterial colonization of the lower airways contributes to airway inflammation; more research is needed to test the hypothesis that this bacterial colonization accelerates the progressive decline in lung function seen in COPD (the vicious circle hypothesis). The course of COPD is characterized by intermittent exacerbations of the disease. Studies of samples obtained by bronchoscopy with the protected specimen brush, analysis of the human immune response with appropriate immunoassays, and antibiotic trials reveal that approximately half of exacerbations are caused by bacteria. Nontypeable Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae are the most common causes of exacerbations, while Chlamydia pneumoniae causes a small proportion. The role of Haemophilus parainfluenzae and gram-negative bacilli remains to be established. Recent progress in studies of the molecular mechanisms of pathogenesis of infection in the human respiratory tract and in vaccine development guided by such studies promises to lead to novel ways to treat and prevent bacterial infections in COPD.

Antibodies to loop 6 of the P2 porin protein of nontypeable Haemophilus influenzae are bactericidal against multiple strains

The P2 porin protein is the most abundant protein in the outer membrane of nontypeable Haemophilus influenzae (NTHI). Analysis of sequences of P2 from different strains reveals the presence of both heterogeneous and conserved surface-exposed loops of the P2 molecule among strains. The present study was undertaken to test the hypothesis that antibodies to a conserved surface-exposed loop are bactericidal for multiple strains of NTHI and could thus form the basis of vaccines to prevent infection due to NTHI. Polyclonal antiserum to a peptide corresponding to loop 6 was raised and was immunopurified over a loop 6 peptide column. Analysis of the antibodies to whole organisms and peptides corresponding to each of the eight loops of P2 by immunoassays revealed that the antibodies were highly specific for loop 6 of P2. The immunopurified antibodies bound to P2 of 14 of 15 strains in immunoblot assays. These antibodies to loop 6 demonstrated complement-mediated bactericidal killing of 8 of 15 strains. These results support the concept of using conserved regions of the P2 protein as a vaccine antigen.

Airway inflammation and etiology of acute exacerbations of chronic bronchitis

STUDY OBJECTIVES

The etiologic role of bacterial pathogens isolated from sputum culture in 40 to 50% of acute exacerbations of chronic bronchitis (AECB) is controversial. If bacterial pathogens cause these AECB, they should be associated with greater neutrophilic airway inflammation than pathogen-negative exacerbations.

DESIGN

This hypothesis was tested by comparing levels of interleukin (IL)-8, tumor necrosis factor (TNF)-alpha, and neutrophil elastase (NE) in 81 sputum samples obtained from 45 patients with AECB. Four groups were compared. In the first three groups, nontypable Haemophilus influenzae (n = 20), Haemophilus parainfluenzae (n = 27), and Moraxella catarrhalis (n = 14) were isolated as sole pathogens, respectively. In the fourth group, only normal flora was isolated (n = 20). Paired samples, obtained from individual patients at different times, that differed in their culture results were also compared.

SETTING

An outpatient research clinic at a Veterans Affairs Medical Center.

PATIENTS

These patients were participating in a prospective, longitudinal study of the dynamics of bacterial infection in chronic bronchitis, for which they were seen in the study clinic on a monthly basis as well as when they were experiencing symptoms suggestive of AECB.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

H influenzae exacerbations were associated with significantly higher sputum IL-8, TNF-alpha, and NE. M catarrhalis exacerbations demonstrated significantly higher sputum TNF-alpha and NE when compared to pathogen-negative exacerbations. H parainfluenzae-associated exacerbations had an inflammatory profile similar to pathogen-negative exacerbations. Sputum elastase level distinguished bacterial from nonbacterial AECB and correlated with clinical severity of the AECB.

CONCLUSIONS

Increased airway inflammation associated with isolation of H influenzae and M catarrhalis supports an etiologic role of these pathogens in AECB.

Antigenic structure of outer membrane protein E of Moraxella catarrhalis and construction and characterization of mutants

Outer membrane protein E (OMP E) is a 50-kDa protein of Moraxella catarrhalis which possesses several characteristics indicating that the protein will be an effective vaccine antigen. To study the antigenic structure of OMP E, eight monoclonal antibodies were developed and characterized. Three of the antibodies recognized epitopes which are present on the bacterial surface. Fusion peptides corresponding to overlapping regions of OMP E were constructed, and immunoblot assays were performed to localize the areas of the molecule bound by the monoclonal antibodies. These studies identified a surface-exposed epitope in the region of amino acids 80 through 180. To further study the protein, two mutants which lack OMP E were constructed. In bactericidal assays, the mutants were more readily killed by normal human serum compared to the isogenic parent strains. These results indicate that OMP E is involved in the expression of serum resistance of M. catarrhalis.

Constitutive expression of IL-6-LIKE cytokines in normal bone marrow: implications for pathophysiology of myeloma

Myeloma is a neoplasm thought to "home" to bone marrow. However, evidence for bone-marrow-specific receptors or adhesion molecules expressed on myeloma cells is scanty. Initial myeloma expansion is thought to be due to IL-6 and/or related cytokines. Previous determinations of cytokine expression in bone marrow were performed on bone marrow stromal lines; these findings may not reflect the constitutive pattern of expression in situ. Intracytoplasmic staining for IL-6-like cytokines revealed constitutive expression of some factors in the bone marrow of normal mice, but not spleens. Spleens of myeloma-transplanted SCID mice expressed IL-6-like cytokines, indicative of induction of expression by myeloma. Some cytokines expressed in bone marrow induced myeloma proliferation in the presence of dexamethasone, demonstrating dependence of the myeloma on these cytokines. Our data imply that, rather than "homing" to bone marrow, myeloma cells proliferated within marrow cavities more than in other organs because of growth factors constitutively expressed by bone marrow cells. As myeloma progressed, we observed the induction of growth factor expression in spleen cells. Furthermore, because cytokines other than IL-6 may induce myeloma cell proliferation, therapy aimed at neutralizing IL-6 may not be the most effective method to treat this disease. These findings have implications for both the pathophysiology and therapy of multiple myeloma.

The role of bacteria in exacerbations of COPD. A constructive view

The role of infection in exacerbations of COPD remains controversial and incompletely understood. Although some investigators believe that bacteria are not important for patients with exacerbation, we disagree and believe that patients with at least two of the three cardinal symptoms of exacerbation should receive antibiotic therapy. With an open-minded view of the area, we review the data, showing that bacteriologic studies, pathologic investigations, and clinical trials all support roles for bacteria and antibiotic therapy in this disease. Still, many questions remain, and future studies will be needed to better define the mechanisms of bacterial invasion in the bronchitic patient and to develop effective vaccines to prevent exacerbations. In the meantime, we must rely on antibiotic therapy, and we will need prospective studies to corroborate preliminary findings showing that different patients may require different therapies; thus, patient subsetting may be vital in the selection of antibiotic therapy for exacerbations of COPD.

Immune response to surface protein A of Streptococcus pneumoniae and to high-molecular-weight outer membrane protein A of Moraxella catarrhalis in children with acute otitis media

The immune response was evaluated in 11 children with Streptococcus pneumoniae and in 9 children with Moraxella catarrhalis otitis media. The age of the children had a range of 4-32 months. The mean IgG, IgM, and IgA antibody responses to surface protein A (PspA) of S. pneumoniae in sera from children at the acute and convalescent stages were 4864 versus 5831 ng/mL, P<.05, 1075 versus 3752 ng/mL, P<.05, and 67 versus 93 ng/mL, nonsignificant (NS), respectively. The mean IgG, IgM, and IgA antibody responses to the high-molecular-weight outer membrane protein (UspA) of M. catarrhalis in sera from children at acute and convalescent stages were 710 versus 935 mg/mL, NS; 1895 versus 2646 ng/mL, NS; and 121 versus 204 ng/mL, P<.05, respectively. These data show that PspA and UspA are immunogenic in children after otitis media.

Bacterial otitis media: pathogenetic considerations

A variety of exciting and important new observations regarding the pathogenesis of nontypable H. influenzae infection have been made in the past decade. The interactions between mucin and OMPs show a high degree of specificity. Multiple adhesins have been identified on the bacterial surface. Colonization of the upper respiratory tract is a dynamic process. Immunodominant, antigenically heterogeneous OMPs are the targets of strain-specific immune responses, accounting in part for the recurrent nature of OM in otitis-prone children. The LOS of nontypable H. influenzae displays a remarkable degree of antigenic and phase variation and may be involved in molecular mimicry of host antigens. Finally nontypable H. influenzae not only lives on the mucosal surface but also clearly has been demonstrated to enter epithelial cells and remain viable in intracellular and intercellular locations in the human upper respiratory tract. These areas of investigation have important implications in understanding the pathogenesis of OM. Elucidating mechanisms of pathogenesis will be important in guiding development of novel ways to prevent OM.

Haemophilus influenzae in chronic bronchitis

Colonization of the adult respiratory tract with nontypable Haemophilus influenzae is a dynamic process with new strains being acquired and replacing old strains periodically. The organism is a common cause of exacerbations of chronic bronchitis based on 3 lines of evidence: quantitative culture of the lower airways obtained by protected specimen brush, antibiotic trials, and serological studies. Nontypable H. influenzae expresses multiple adhesin molecules that mediate adherence to the respiratory tract mucosa. Recent studies have established that the bacterium penetrates the mucosal surface and survives intracellularly and in the interstitium of the submucosa. The organism shows a remarkable degree of antigenic diversity on its surface, including phase variation of lipooligosaccharide, antigenic heterogeneity of surface proteins, point mutations in genes encoding surface proteins and horizontal transfer of genes. These strategies facilitate evasion of the human immune response. Substantial progress has been made in identifying vaccine antigens to prevent infections caused by nontypable H. influenzae.

Purification and characterization of outer membrane protein P6, a vaccine antigen of non-typeable Haemophilus influenzae

Outer membrane protein P6 is a promising vaccine antigen with potential to prevent infections caused by non-typeable Haemophilus influenzae. A convenient and reliable method for the purification of P6 and an assessment of the purity, yield, protein structure, antigenicity and immunogenicity of the purified protein are described. The method begins with intact H. influenzae and utilizes a series of incubations and centrifugations using a single buffer to remove all cell components with the exception of the peptidoglycan to which the P6 is associated. P6 is dissociated from the complex with heat and the insoluble peptidoglycan is removed by centrifugation. The procedure yields highly purified P6. Contamination with lipooligosaccharide is less than 0.025 endotoxin U per microgr P6. The yield of P6 is approximately 2 mg of P6 per l H. influenzae culture. The purified P6 retains both the secondary and tertiary structure as measured by circular dichroism and analysis with monoclonal antibodies. The purified P6 is immunogenic in animals. A convenient method for purifying P6 which retains antigenicity and immunogenicity will be an important tool for future studies of the vaccine potential of P6.

Investigation of mucosal immunisation in pulmonary clearance of Moraxella (Branhamella) catarrhalis

Moraxella (Branhamella) catarrhalis is a common cause of otitis media in children and respiratory infection in adults with chronic obstructive pulmonary disease. To identify immune responses that may facilitate the development of a mucosal vaccine, a mouse model to study pulmonary responses was established. Regimes involving intra-Peyer's patch, intratracheal and intranasal routes of immunisation with killed M. catarrhalis were investigated. A mucosal immunisation regime of a primary intra-Peyer's patch immunisation with an intratracheal boost resulted in significantly enhanced pulmonary clearance of bacteria compared to controls following an intratracheal challenge with live bacteria. Additional intratracheal boosts did not induce further enhancement of clearance. Intra-Peyer's patch immunisation alone, intratracheal and intranasal immunisations did not induce enhanced clearance. The levels of specific IgG and IgA in serum and bronchoalveolar lavage fluid correlated with pulmonary clearance. The present study showed that mucosal immunisation induced enhanced pulmonary clearance of M. catarrhalis following live bacterial challenge. This mucosal immunisation model has demonstrated that a mucosal vaccine, particularly an oral vaccine, would be feasible.

Analysis of antigenic structure and human immune response to outer membrane protein CD of Moraxella catarrhalis

Moraxella catarrhalis is an important cause of otitis media in children and lower respiratory tract infections in adults with chronic obstructive pulmonary disease (COPD). Outer membrane protein CD (OMP CD) is a 45-kDa protein which is a potential vaccine antigen to prevent infections caused by M. catarrhalis. Eight monoclonal antibodies were used to study the antigenic structure of the OMP CD molecule by assaying recombinant peptides corresponding to the sequence of the protein. This approach identified two surface-exposed epitopes, including one near the amino terminus (amino acids 25 to 44) and one in the central region of the molecule (amino acids 261 to 331). Assays with serum and sputum supernatants of adults with COPD revealed variable levels of antibodies to OMP CD among individuals. To determine which portions of the OMP CD molecule were recognized by human antibodies, three human serum samples were studied with six recombinant peptides which span the sequence of OMP CD. All three sera contained immunoglobulin G antibodies which recognized exclusively the peptide corresponding to amino acids 203 to 260 by immunoblot assay. Adsorption experiments with whole bacteria established that some of the human antibodies are directed at surface-exposed epitopes on OMP CD. We conclude that OMP CD is a highly conserved molecule which contains at least two separate epitopes which are exposed on the bacterial surface. While individual adults with COPD show variability in the immune response to OMP CD, a specific region of the OMP CD molecule (amino acids 203 to 260) is important as a target of the human immune response.

Immunization of mice with P6 of nontypeable Haemophilus influenzae: kinetics of the antibody response and IgG subclasses

The kinetics of the anti-P6 antibody response was characterized in three strains of mice of different haplotypes (Balb/c; H-2d, C3H/H; H-2k, SJL/J; H-2s). Anti-P6 antibodies were measured on a weekly basis by enzyme-linked immunosorbent assay (ELISA). The primary response peaked 2 or 3 weeks after the initial injection with 40 microg of purified P6. The response remained at a plateau for 8-10 weeks. A maximum titer of 1:1,638,400 was attained and then steadily declined. To study the ability of P6 to generate a recall response, we opted to boost the vaccinated mice with a known subimmunogenic dose of live nontypeable Haemophilus influenzae (NTHI) bacteria. After the anti-P6 antibody titers in the primed animals had stayed at baseline levels for 2 weeks, the mice were injected intraperitonealy with 10(8) cfu of NTHI in sterile saline. This challenge with live NTHI bacteria induced a very rapid and strong secondary antibody response in all mice. Finally, we demonstrated that these murine anti-P6 sera were 100% bactericidal against three strains of NTHI when tested in a complement dependant bactericidal assay.

Simultaneous respiratory tract colonization by multiple strains of nontypeable haemophilus influenzae in chronic obstructive pulmonary disease: implications for antibiotic therapy

Nontypeable Haemophilus influenzae often causes exacerbations of chronic obstructive pulmonary disease (COPD), and these exacerbations are frequently treated with oral antibiotics. The goals of this study were to determine the frequency of the simultaneous presence of multiple strains of H. influenzae in sputum and to measure the MICs of antibiotics for the isolates. In a prospective study, adults with COPD were seen monthly. Sputum cultures were obtained, and individual colonies were subjected to genomic DNA typing and MIC determinations. Multiple strains of H. influenzae were present simultaneously in the sputum of 26.3% of adults with COPD. In 64.5% of these, MICs of >/=1 antibiotic varied by >/=4-fold among the strains. Therefore, multiple strains of H. influenzae are frequently present simultaneously in the sputum of adults with COPD, and the antimicrobial susceptibility of different strains in the same sputum sometimes differs.

Enhancement of pulmonary clearance of Moraxella (Branhamella) catarrhalis following immunization with outer membrane protein CD in a mouse model

Moraxella (Branhamella) catarrhalis is an important human respiratory tract pathogen. Outer membrane protein (OMP) CD is highly conserved among strains and has characteristics that indicate it may be an effective vaccine antigen. This study investigated the effect of immunization with OMP CD on pulmonary clearance following intratracheal challenge of mice with M. catarrhalis. Two routes of immunization were studied: mucosal immunization (intra-Peyer's patch followed by intratracheal boost) and intramuscular immunization with OMP CD. Both resulted in enhanced pulmonary clearance of M. catarrhalis compared with sham-immunized controls. Immunization with OMP CD induced specific antibodies in serum and bronchoalveolar lavage fluid and induced a specific lymphocyte proliferative response in T cells from mesenteric lymph nodes from mice mucosally immunized with OMP CD. On the basis of these results, OMP CD should undergo continued testing to determine whether it will induce a protective immune response in humans.

Serum antibodies specific to CD outer membrane protein of Moraxella catarrhalis, P6 outer membrane protein of non-typeable Haemophilus influenzae and capsular polysaccharides of Streptococcus pneumoniae in children with otitis media with effusion

We measured the levels of serum IgG antibodies to CD outer membrane protein of Moraxella catarrhalis, P6 outer membrane protein of non-typeable Haemophilus influenzae and capsular polysaccharides of Streptococcus pneumoniae in 168 children with otitis media with effusion (OME) who were followed prospectively, using ELISA. Serum IgG antibodies to CD, P6 and pneumococcal capsular polysaccharides were detected in all samples. The anti-pneumococcal polysaccharides antibody level was highest, followed by the anti-P6 antibody level and anti-CD antibody was lowest (median:interquartile ranges were 45.9:19.1-100 microg/ml, 15.6:9.70-23.2 microg/ml and 1.06:0.73-1.87 microg/ml, respectively). In children aged 0-6 years, there were positive correlations among the antibody levels (anti-CD vs anti-P6, r=0.325, p <0.001; anti-CD vs anti-polysaccharide, r=0.397, p <0.0001; anti-P6 vs anti-polysaccharide, r=0.175, p=0.057). However, no relationship was seen in children aged 7-15 years. Children were classified according to severity of OME during the 1-year follow-up. In children aged 0-6 years, the severity of OME correlated inversely with the levels of anti-CD antibody (r=-.23, p=0.012), of anti-P6 antibody (r=-0.292, p=0.0015), and of anti-pneumococcal polysaccharides antibody (r=-0.25, p=0.0064). However, no correlation was found between antibody levels and severity of OME in children aged 7-15 years. These data suggest that persistence and/or recurrence of OME may be due to an insufficient serum antibody response to middle ear pathogens in young children.

Human milk lactoferrin inactivates two putative colonization factors expressed by Haemophilus influenzae

Haemophilus influenzae is a major cause of otitis media and other respiratory tract disease in children. The pathogenesis of disease begins with colonization of the upper respiratory mucosa, a process that involves evasion of local immune mechanisms and adherence to epithelial cells. Several studies have demonstrated that human milk is protective against H. influenzae colonization and disease. In the present study, we examined the effect of human milk on the H. influenzae IgA1 protease and Hap adhesin, two autotransported proteins that are presumed to facilitate colonization. Our results demonstrated that human milk lactoferrin efficiently extracted the IgA1 protease preprotein from the bacterial outer membrane. In addition, lactoferrin specifically degraded the Hap adhesin and abolished Hap-mediated adherence. Extraction of IgA1 protease and degradation of Hap were localized to the N-lobe of the bilobed lactoferrin molecule and were inhibited by serine protease inhibitors, suggesting that the lactoferrin N-lobe may contain serine protease activity. Additional experiments revealed no effect of lactoferrin on the H. influenzae P2, P5, and P6 outer-membrane proteins, which are distinguished from IgA1 protease and Hap by the lack of an N-terminal passenger domain or an extracellular linker region. These results suggest that human milk lactoferrin may attenuate the pathogenic potential of H. influenzae by selectively inactivating IgA1 protease and Hap, thereby interfering with colonization. Future studies should examine the therapeutic potential of lactoferrin, perhaps as a supplement in infant formulas.

Outer-membrane antigen expression by Moraxella (Branhamella) catarrhalis influences pulmonary clearance

Moraxella (Branhamella) catarrhalis is a common respiratory tract pathogen in man. The bacterium shows a strong tendency to form aggregates in vitro. A variant strain of M. catarrhalis that showed a reduced tendency to form aggregates was selected by successive in-vitro passage in broth culture from which aggregates had settled. The non-clumping variant strain showed alteration in expression of outer-membrane antigens, including the HMW-OMP, an outer-membrane protein of c. 200 kDa, outer-membrane protein CD and lipo-oligosaccharide. A mouse model for pulmonary challenge with M. catarrhalis revealed significant differences in the rate of clearance of the isogenic variant strains from the lung. The parent strain caused enhanced recruitment of neutrophils to the lung and more rapid clearance of bacteria from the lungs in comparison to the non-clumping variant. It is concluded that alteration of expression of surface molecules by M. catarrhalis has a significant impact in an in-vivo model of pulmonary clearance.

Comparison between cefprozil and penicillin to eradicate pharyngeal colonization of group A beta-hemolytic streptococci

BACKGROUND

Our objective was to perform a prospective, randomized, double blinded study of cefprozil and penicillin therapy to eradicate group A beta-hemolytic streptococci (GABHS) in children who were bacteriologic failures after receiving a standard 10-day course of penicillin treatment for GABHS pharyngitis.

METHODS

Children and adolescents 2 to 18 years of age were eligible for the study. From 3 to 7 days after completing oral penicillin therapy for pharyngitis caused by GABHS, the study was explained, informed consent was obtained, a history and physical examination were completed and a throat culture was performed. Children with throat cultures positive for GABHS were randomized to receive either cefprozil or penicillin for 10 days. Children who were bacteriologic failures after administration of the first study drug were crossed over to receive the alternate drug.

RESULTS

Of 180 enrolled children 66 (37%) had throat cultures positive for GABHS. Seventeen were excluded from the study, leaving 49 who completed the protocol. Of the 49 participants 26 received cefprozil initially whereas 23 received penicillin. GABHS were eradicated from the pharynx of 73% of children who received cefprozil as the first antibiotic compared with 39% of penicillin recipients (chi square, 5.748, 0.01 < P < 0.025). After crossover of failures, the final efficacy rate for cefprozil was 65% compared with 36.7% for penicillin (chi square, 5.523, 0.01 < P < 0.025).

CONCLUSIONS

Cefprozil was more effective than penicillin in treating children who were bacteriologic failures after a standard 10-day course of oral penicillin.

Mechanisms of recurrent otitis media: importance of the immune response to bacterial surface antigens

Otitis-prone children experience recurrent episodes of otitis media due to nontypeable H. influenzae (NTHI). A protective immune response occurs following infection, but this immune response is specific for the infecting strain, leaving the child susceptible to infection by other strains of NTHI. Little is known about the mechanism by which a strain-specific antibody response occurs to nonencapsulated bacteria. To explore the mechanism by which this strain-specific response occurs, animals were inoculated with whole bacterial cells and the antibody response was studied. The antibody response was predominantly directed to a highly strain-specific, immunodominant surface loop on the major outer membrane protein. This exquisitely restricted immune response leaves the host susceptible to recurrent infections by many strains of NTHI. The ability of the bacterium to direct the host to make a strain-specific antibody response has important implications in understanding the immune response to otitis media due to NTHI and in designing strategies for vaccine development.

Human immune response to nontypeable Haemophilus influenzae in chronic bronchitis

Nontypeable Haemophilus influenzae (NTHI) causes recurrent respiratory tract infections in patients with chronic bronchitis. To elucidate the human immune response to NTHI, sera from 2 patients with exacerbations of chronic bronchitis due to NTHI were characterized. Both patients developed new bactericidal antibodies following infection. Immunoblot assays with homologous strains revealed antibodies to many antigens, with minimal difference between pre- and postexacerbation sera. By contrast, whole cell radioimmunoprecipitation, which detects antibodies exclusively to epitopes exposed on the bacterial surface, revealed that both patients made new antibodies to a limited number of antigens following infection, including P2, the major outer membrane protein of NTHI. Adsorption experiments showed that strain-specific, surface-exposed epitopes on the P2 molecule are targets for bactericidal antibodies. These results indicate that new bactericidal antibodies following infection by NTHI recognize antigenically heterogeneous surface-exposed epitopes on P2 and other surface proteins of NTHI.

Analysis of isolates recovered from multiple sites of the nasopharynx of children colonized by nontypeable Haemophilus influenzae

To determine whether the nasopharynx of children is colonized by a single or multiple strains of nontypeable Haemophilus influenzae, cultures were obtained from six nasopharyngeal sites in five children. For each child, all isolates yielded identical polymerase chain reaction fingerprints. The results indicate that these children were colonized in the nasopharynx with a single strain of nontypeable Haemophilus influenzae at one time.

Antigenic heterogeneity and molecular analysis of CopB of Moraxella (Branhamella) catarrhalis

Outer membrane protein (OMP) CopB, an iron-repressible 81-kDa major OMP of Moraxella (Branhamella) catarrhalis has been a major focus of investigation. To assess CopB as a potential vaccine antigen, we elucidated the degree of antigenic and sequence heterogeneity in this protein among strains of M. catarrhalis. Two monoclonal antibodies, 1F5 and 2.9F, which bind to surface-exposed epitopes on CopB recognized 60 and 70% of the strains, respectively. The degree of sequence heterogeneity in CopB was assessed by cloning and sequencing the CopB gene from two different strains of M. catarrhalis and comparing with the published sequence. There was 92 to 96% homology between the sequences at the nucleotide level and 90 to 95% homology at the amino acid level. The variability in the protein sequence is confined mainly to three moderately variable regions. Restriction fragment length polymorphism (RFLP) analysis of the CopB genes obtained from 20 diverse strains by PCR was performed. Ninety percent of the potential restriction sites in the constant regions and 47% of the potential restriction sites in the variable regions were present in the 20 strains, indicating that the pattern of variable and constant areas in the CopB gene is a general pattern among strains of M. catarrhalis. We conclude that the CopB gene is largely conserved among strains of M. catarrhalis and contains discrete regions which show moderate heterogeneity among strains.

Antigenic characterization and analysis of the human immune response to outer membrane protein E of Branhamella catarrhalis

Outer membrane protein E (OMP E) is a 50-kDa major OMP of Branhamella catarrhalis. Polyclonal antisera and four monoclonal antibodies (MAbs) to OMP E were generated to study its antigenic structure. All antibodies recognized epitopes in all 19 B. catarrhalis strains tested by immunoblot assays. By flow cytometry, it was determined that MAbs 1B3 and 9G10d recognized epitopes which are expressed on the surface of the intact bacterium, while MAbs IC11 and 7C10 recognized epitopes which were buried within the outer membrane. A competitive enzyme-linked immunosorbent assay showed that MAbs 1B3 and 9G10d recognize the same or closely related epitopes. Proteinase K treatment of whole bacterial cells revealed that MAbs 1B3 and 9G10d recognize a surface-exposed epitope located in the 17-kDa region towards the amino terminus of OMP E. The human serum and mucosal antibody responses to OMP E in adults with chronic bronchitis were studied. A majority of these patients had immunoglobulin A to OMP E in sputum supernatants. None of ten adults who experienced lower respiratory tract infections due to B. catarrhalis demonstrated a clear-cut rise in antibody titer to OMP E in serum or sputum supernatant. This study has demonstrated that OMP E has at least one surface-exposed epitope which is highly conserved among strains of B. catarrhalis and which is located in the amino-terminal 184 amino acids of the molecule.

Specific binding of Haemophilus influenzae to minor gangliosides of human respiratory epithelial cells

Gangliosides are sialylated glycosphingolipids that serve as receptors for various bacteria. To investigate endogenous gangliosides of human respiratory epithelial cells as potential receptors for Haemophilus influenzae, three strains, including nontypeable H. influenzae (NTHI) 1479, and isogenic fimbriated (f+) and nonfimbriated (f0) H. influenzae type b 770235, were 3H labeled and overlaid on two-dimensional thin-layer chromatography (TLC) plates containing either purified HEp-2 gangliosides or murine brain gangliosides. NTHI 1479 bound exclusively to two distinct minor ganglioside doublets, with mobilities near that of GM1. These minor gangliosides comprised only 14.2 and 9.4% of the total, respectively. NTHI 1479 also bound to a distinct ganglioside of human macrophages whose chromatographic mobilities closely resemble those of one of the NTHI-binding gangliosides of HEp-2 cells. H. influenzae type b 770235 f+ and f0 each bound to a different minor HEp-2 ganglioside doublet, with proportionately weaker affinity for a major ganglioside doublet. Remarkably, none of the three strains bound to any murine brain gangliosides. Moreover, when 80 to 90% of sialic acid residues were enzymatically removed from HEp-2 gangliosides, NTHI 1479 binding was proportionately impaired, compared with untreated controls. Our findings support a role for specific gangliosides of specific cells as receptors for H. influenzae strains. Our findings further demonstrate that individual minor gangliosides possess unique biological properties.

Middle ear mucin glycoprotein: purification and interaction with nontypable Haemophilus influenzae and Moraxella catarrhalis

Nontypable Haemophilus influenzae and Moraxella catarrhalis are important pathogens in children and adults. The mechanisms of their adherence to the epithelial cell surface and colonization are not clear. For the pathogen to adhere to the epithelial cell, it must first attach to and penetrate the mucus barrier. Mucin glycoproteins of the mucus layer generally are thought to be involved in bacterial attachment. To understand the precise mechanisms of middle ear mucin-bacterial interactions, we used an overlay binding assay with a highly purified middle ear mucin and outer membrane proteins of both nontypable H. influenzae and M. catarrhalis. Outer membrane proteins P2 and P5 were identified as the major components that medicate the binding between nontypable H. influenzae and human middle ear mucin. Moreover, the 57 kDa protein, CD, of the outer membrane protein of M. catarrhalis was found to be the only protein binding human middle ear mucin. Finally, it appears that a protein-oligosaccharide interaction is responsible for binding because asialo-mucin does not bind to either of the bacteria. Knowledge of the specific bacterial-mucin interaction may provide an understanding of the bacterial-epithelial cell colonization. Conversely, comprehension of this interaction between bacteria and purified mucin may be a strategy to prevent colonization of potential pathogens that cause otitis media and sinusitis in children.

Middle Ear Mucin Glycoprotein: Purification and Interaction with Nontypable Haemophilus Influenzae and Moraxella Catarrhalis

Nontypable Haemophilus influenzae and Moraxella catarrhalis are important pathogens in children and adults. The mechanisms of their adherence to the epithelial cell surface and colonization are not clear. For the pathogen to adhere to the epithelial cell, it must first attach to and penetrate the mucus barrier. Mucin glycoproteins of the mucus layer generally are thought to be involved in bacterial attachment. To understand the precise mechanisms of middle ear mucin-bacterial interactions, we used an overlay binding assay with a highly purified middle ear mucin and outer membrane proteins of both nontypable H. influenzae and M. catarrhalis. Outer membrane proteins P2 and P5 were identified as the major components that mediate the binding between nontypable H. influenzae and human middle ear mucin. Moreover, the 57 kDa protein, CD, of the outer membrane protein of M. catarrhalis was found to be the only protein binding human middle ear mucin. Finally, it appears that a protein-oligosaccharide interaction is responsible for binding because asialo-mucin does not bind to either of the bacteria. Knowledge of the specific bacterial-mucin interaction may provide an understanding of the bacterial-epithelial cell colonization. Conversely, comprehension of this interaction between bacteria and purified mucin may be a strategy to prevent colonization of potential pathogens that cause otitis media and sinusitis in children.

Importance of an immunodominant surface-exposed loop on outer membrane protein P2 of nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHI) frequently causes recurrent infections of the respiratory tract in humans. Previous indirect evidence suggested that a strain-specific immune response occurs following infection and that this immune response is directed at an immunodominant epitope on the bacterial surface. To test this hypothesis, mice and rabbits were immunized with whole cells of a strain of NTHI and the antiserum was characterized to identify the antigens to which antibodies were directed. All animals made a prominent antibody response to the loop 5 region of the P2 molecule, which is the major outer membrane protein. Rabbit serum showed complement-dependent bactericidal activity. Adsorption of the immune serum with the loop 5 fusion peptide removed bactericidal activity and also abolished reactivity to P2 detected by an immunoblot assay, an enzyme-linked immunosorbent assay, and a radioimmunoprecipitation assay. These data indicate that immunization with whole cells of NTHI results in a prominent antibody response which is directed at epitopes on the loop 5 region of the P2 molecule. Thus, a strain-specific immune response to NTHI occurs as a result of the expression of an immunodominant epitope on the P2 molecule.

Isolation and characterization of the Haemophilus influenzae tolQ, tolR, tolA and tolB genes

The tolQ, R, A and B genes have been isolated from the DNA of Haemophilus influenzae and sequenced. The deduced amino acid (aa) sequence of the H. influenzae TolQ, TolR, TolA and TolB show 67, 63, 41 and 62% identity with Escherichia coli TolQRAB proteins, respectively. These four proteins are involved in transport of colicins and phages across the cell envelope. The translational stop codon of TolB (the last gene in the cluster) is 23 bases upstream of the start codon of the P6 lipoprotein gene. Primer extension and Northern blot analysis revealed that the start of the P6 transcript is within the tolB gene. Nucleotide sequence (nt) analysis of the entire tolQRABP6 region shows a transcriptional terminator immediately downstream of the P6 gene. The tolQRABP6 gene cluster of H. influenzae may thus constitute an operon.

Branhamella catarrhalis: epidemiology, surface antigenic structure, and immune response

Over the past decade, Branhamella catarrhalis has emerged as an important human pathogen. The bacterium is a common cause of otitis media in children and of lower respiratory tract infections in adults with chronic obstructive pulmonary disease. B. catarrhalis is exclusively a human pathogen. It colonizes the respiratory tract of a small proportion of adults and a larger proportion of children. Studies involving restriction enzyme analysis of genomic DNA show that colonization is a dynamic process, with the human host eliminating and acquiring new strains frequently. The surface of B. catarrhalis contains outer membrane proteins, lipooligosaccharide, and pili. The genes which encode several outer membrane proteins have been cloned, and some of these proteins are being studied as potential vaccine antigens. Analysis of the immune response has been limited by the lack of an adequate animal model of B. catarrhalis infection. New information regarding outer membrane structure should guide studies of the human immune response to B. catarrhalis. Immunoassays which specifically detect antibodies to determinants exposed on the bacterial surface will elucidate the most relevant immune response. The recognition of B. catarrhalis as an important human pathogen has stimulated research on the epidemiology and surface structures of the bacterium. Future studies to understand the mechanisms of infection and to elucidate the human immune response to infection hold promise of developing new methods to treat and prevent infections caused by B. catarrhalis.

Binding between outer membrane proteins of nontypeable Haemophilus influenzae and human nasopharyngeal mucin

Bacterial colonization of the epithelial cells precedes infection. Mucins of the epithelial cell secretions modulate bacterial colonization. This study was designed to understand the mechanism of mucin-bacterial interactions and in particular binding between nontypeable Haemophilus influenzae and nasopharyngeal mucin(s). In an overlay assay, binding appears to be mediated by outer membrane proteins P2 and P5 of bacteria and sialic acid-containing oligosaccharides of mucin.

A monoclonal antibody to human macrophage gangliosides inhibits macrophage migration

Gangliosides have diverse immunoregulatory properties. The gangliosides endogenous to macrophages may have immunoregulatory properties that distinguish them from other gangliosides. Gangliosides have been indirectly implicated in macrophage migration as putative cell surface receptors for migration inhibitory factor (MIF). In this study, a monoclonal antibody to human macrophage gangliosides (antibody 25F4) was developed and characterized. This is the first report of the development of monoclonal antibodies to gangliosides of macrophages of any species. Thin-layer chromatographic immunostaining indicated that antibody 25F4 recognized major gangliosides of human macrophages but did not recognized those previously identified as containing fucose. Immunofluorescent surface labeling of viable human macrophages indicated that antibody 25F4 recognized a surface-accessible epitope, present on all cells, and that this was abolished with lipid depletion of macrophage membranes. This epitope was not present on several human nonmacrophage cells. Finally, human macrophages pretreated with antibody 25F4 demonstrated striking inhibition of migration of an agarose droplet assay, whereas an irrelevant monoclonal antibody or monoclonal antibodies to nonganglioside surface epitopes of human macrophages had no effect on migration. Migration inhibition occurred even though antibody 25F4 was removed from the extracellular milieu and was not due to formation of cellular aggregates. These studies support a role for human macrophage gangliosides in macrophage migration.

Outer membrane protein CD of Branhamella catarrhalis: sequence conservation in strains recovered from the human respiratory tract

Branhamella catarrhalis causes lower respiratory tract infections in patients with chronic obstructive pulmonary disease. The outer membrane protein CD (OMP-CD) of B. catarrhalis is a major, heat-modifiable OMP. The goals of this study are to characterize the degree of conservation of OMP-CD among strains and to investigate if OMP-CD maintains its homogeneity under the effect of host immune selective pressure. Isolates of B. catarrhalis were collected prospectively from patients with bronchiectasis and chronic bronchitis. We studied the OMP-CD gene by analysis of PCR restriction fragment length polymorphisms (PCR-RFLP) and further determined DNA sequence of the CD gene of eight selected isolates. Five patterns of PCR-RFLP of the OMP-CD gene were observed among all isolates when the gene was digested with Sau3AI. The sequence analysis revealed a high degree of homogeneity in OMP-CD among strains of B. catarrhalis. Three regions of OMP-CD with minimal sequence heterogeneity were identified. The sequences of the OMP-CD gene of isolates collected from patients colonized with the same strain for up to 6 months was identical. These observations establish that the OMP-CD of B. catarrhalis recovered from clinical isolates is highly conserved among strains.

Dynamics of respiratory tract colonization by Branhamella catarrhalis in bronchiectasis

Branhamella catarrhalis is increasingly recognized as a lower respiratory tract pathogen, particularly in chronic lung diseases. This project defines a population of patients in whom the dynamics of colonization and infection caused by this organism could be studied. A method employing pulsed field gel electrophoresis (PFGE) of genomic DNA was developed. Twenty-eight patients with bronchiectasis followed prospectively for 26.8 mo (mean) were seen monthly or bimonthly and at the time of a purulent exacerbation. Quantitative bacterial cultures were performed on sputum obtained at each visit. Six of 28 had B. catarrhalis isolated repeatedly. Viable numbers of B. catarrhalis were similar to other bacterial pathogens. Restriction fragment length polymorphism (RFLP) analysis of chromosomal DNA using PFGE was performed on 37 of the 47 isolates recovered. Each patient was colonized by two to four strains with different RFLP patterns. Duration of colonization by the same strain was 2.3 mo (mean). Strain acquisition did not correlate with exacerbation, antibiotic therapy, or season. We conclude that (1) a subset of bronchiectatic patients is colonized with B. catarrhalis, (2) RFLP is a sensitive tool to study strain acquisition, and (3) acquisition and clearance of B. catarrhalis from the respiratory tract is a dynamic process.

A comparison of survival at different degrees of hemorrhagic shock in germ-free and germ-bearing rats

We have previously reported superior survival after one level of hemorrhagic shock in germ-free (GF) rats compared with germ-bearing (GB) rats. The objective of this study was to determine the effect of the GF state on survival at different degrees of hemorrhagic shock. GF and GB rats were bled to a mean arterial blood pressure of 30 mmHg. Shock was terminated after 10, 20, 40, or 80% of the maximum shed blood volume was reabsorbed spontaneously. Both shock time and time to decompensation were significantly longer in GF rats (p < .05). Comparative survival was greater for GF rats at most levels of shock (p < .01). This superiority in survival was greatest at moderate shock levels and decreased at severe shock levels. There may be several reasons for the increased tolerance of GF animals to hemorrhagic shock such as metabolic or immunologic variations. It is hard to avoid the fact, however, that the most notable difference between the GF and GB rat is the presence or absence of bacteria.