Is attachment of bacteria to the epithelial cells of the nasopharynx the key to otitis media?

Bacterial adherence to mucosal epithelium in the upper airways has less significance than believed

BACKGROUND

Bacterial adherence to the upper airway epithelium is considered to be an important phenomenon in the pathogenesis of infections. However, the evidence for the hypothesis that bacterial adherence to mucosal epithelial cells has significance for pathogenesis of mucosal infections is based on studies using indirect techniques. We could find no biopsy studies with direct ocular observations of significant numbers of bacteria adhering to upper airway mucosal epithelial cells either in health or during disease.

RESULTS

We studied specimens from healthy and infected tonsillar epithelium and specimens from the soft palate epithelium obtained by surgery. The specimens were examined by TEM. In the vast majority of specimens, we found no bacteria adhering to the epithelial cells in the mucosal line regardless of whether the patient was infected or not. Bacteria adhering to shed epithelial cells were seen in higher numbers. Furthermore, as bacteria are small compared to epithelial cells, we calculated the risk of overlooking every adhered bacteria in a section if bacterial adherence was such a significant phenomenon as earlier suggested. We found this risk to be very small.

CONCLUSION

We conclude that bacterial adherence to mucosal surface epithelial cells is not a significant phenomenon, either in healthy mucosa in the upper airways or during infection. This is also in line with our earlier results, where we have shown that the site for the infectious process in pharyngotonsillitis is in the secretion on the tonsillar mucosal surface.

Identification of a Haemophilus influenzae 5'-nucleotidase protein: cloning of the nucA gene and immunogenicity and characterization of the NucA protein

We report on the identification of a surface-exposed, highly conserved, immunogenic nontypeable Haemophilus influenzae (NTHi) protein, which elicits cross-reactive bactericidal antibodies against NTHi. The protein was extracted from NTHi strain P860295 with KSCN and purified; it migrated as a single band on a sodium dodecyl sulfate-polyacrylamide gel with an apparent molecular mass of 63 kDa. Mouse antiserum generated against the purified protein was reactive on whole-cell enzyme-linked immunosorbent assay (ELISA) with seven NTHi strains and type b Eagan and Whittier strains and exhibited bactericidal activity to homologous and heterologous NTHi strains. However, the protein is made in small amounts in NTHi as corroborated by immunoelectron microscopy. To further study this protein, we cloned, sequenced, and expressed it recombinantly in Escherichia coli. The recombinant protein is localized in the periplasm of E. coli and has been purified to homogeneity. Both the recombinant and native proteins possess 5'-nucleotidase activity; hence, the protein has been called NucA. Mouse antiserum directed against the recombinant NucA protein was reactive on Western immunoblots and whole-cell ELISA with all H. influenzae strains tested including Eagan and was bactericidal for two heterologous strains tested. The antiserum also resulted in a log reduction in bacteremia, in an infant-rat protection study with H. influenzae type b as the challenge strain. These features suggest that NucA is a potential subunit vaccine candidate against NTHi disease.

Predictive Value of an Adherence Test for Acute Otitis Media

The predictive value of an in vitro adherence test of the bacterium Streptococcus pneumoniae for the development of recurrent otitis media was calculated 5 years after the initial test. Nasopharyngeal cells from 56 children suffering from acute otitis media (AOM) and from healthy children were tested for adherence of a standard pneumococcal type (capsular serotype 6). The average adherence of the bacteria to epithelial cells from the group suffering from AOM was greater than the average adherence in the control group ( p < 0.005), both when adherence was counted microscopically and radioactively. Subjects were followed up periodically over a 5-year period. Four out of 5 healthy children who had high mean adherence values experienced AOM during the 5 years, and 1 child classified as AOM-prone was found to be healthy. Based on the retrospective data, the positive predictive value of this test was 98.2%, and the negative predictive value was 90.7%.

Middle-ear disease in children exposed prenatally to polychlorinated biphenyls and polychlorinated dibenzofurans

During 1978 and 1979, an episode of poisoning from ingestion of rice oil contaminated with polychlorinated biphenyls and polychlorinated dibenzofurans occurred in central Taiwan. We followed-up children who had been born between June 1978 and March 1985, as well as matched unexposed children. The mothers of exposed children had consumed contaminated oils before the children were born. In 1993, otolaryngologists examined the middle ear of each child with a pneumatic otoscope, and they measured the middle-ear pressure by tympanometry with a Rion RS20 impedance audiometer. The exposed children had a significantly higher prevalence of middle-ear diseases than their matched controls. The exposed children who had ear diseases had higher serum levels of 2,3,4,7,8-pentachloro- and 1,2,3,4,7,8-hexachloro-dibenzofurans than the children who did not have similar diseases. Therefore, in this study, children exposed to polychlorinated biphenyls and polychlorinated dibenzofurans had a higher incidence of middle-ear diseases than their controls.

Pacifiers and dental structure as risk factors for otitis media

The purpose of the study was to examine the relationship between ear infections and dentition, sucking habits, pacifier sucking and atopic and allergic diseases in a historic cohort survey. The series comprised 944 5-year-old children representing about 3/4 of the whole age cohort. The parents completed a questionnaire that asked for details of the children's ear infections, sucking habits and atopic or allergic diseases diagnosed by a physician. The dental status was examined by the child's own local dentist. The children who had used a pacifier had a greater risk of having recurrent attacks of acute otitis media in their history than those who had not used a pacifier (risk ratio (RR), 1.43; 95% confidence interval (CI), 1.06-1.93; P = 0.02). Mouth breathing was significantly associated with acute otitis media (RR, 1.87; CI, 1.28-2.73; P = 0.01), as was open bite (RR, 1.36; CI, 1.01-1.84; P = 0.04), but no other mode of malocclusion. The population attributable risk of otitis media caused by pacifier amounted to a total of 478 attacks or 0.7 per child. The association between otitis media and the use of a pacifier remained even after adjusting for mouth breathing and the measures of malocclusion. Neither thumb sucking nor atopic eczema showed such an association.

The nasopharynx, eustachian tube and otitis media

It has been classically hypothesized that a mass in the nasopharynx causes an obstacle to air flow through the eustachian tube, thereby creating a negative pressure in the middle ear followed by an effusion. However, examination of the relevant data concerning the supposed obstruction of the eustachian tube by nasopharyngeal carcinomas, choanal polyps and adenoids does not seem to support this cause and effect relationship. Evidence points to other more sophisticated mechanisms which cause negative pressure and an effusion in pathological middle ear conditions. While the hypothesis of a nasopharyngeal mass as the usual obstructive cause of middle ear effusion is hard to maintain, evidence does exist to support the origin of middle ear infection, as seen in acute and secretory otitis media, as being associated, at times, with an ascending infection from the nasopharynx.

Changes in adherence of respiratory pathogens to HEp-2 cells induced by subinhibitory concentrations of sparfloxacin, ciprofloxacin, and trimethoprim

Preincubation with subinhibitory concentrations of sparfloxacin, ciprofloxacin, and trimethoprim decreased the adherence of the respiratory pathogens Klebsiella pneumoniae, Haemophilus influenzae, and Moraxella (Branhamella) catarrhalis to human larynx carcinoma HEp-2 cells. Subinhibitory concentrations of sparfloxacin did not change the adherence of Pseudomonas aeruginosa or Streptococcus pneumoniae 15.62, but adhesion of S. pneumoniae 15.42 was significantly enhanced by subinhibitory antimicrobial concentrations.

Secretory IgA-, IgG- and C3b-coated bacteria in the nasopharynx of otitis-prone and non-otitis-prone children

The proportions of secretory IgA (SIgA)-, IgG- and C3b-coated bacteria obtained from a well-defined area on the posterior wall of the nasopharynx (NPH) close to the Eustachian tube were determined. Samples taken from 25 otitis-prone (OP) and 25 non-otitis-prone (NOP) children with normal serum levels of IgA and IgG were evaluated using an immunofluorescence assay. Both groups harboured significantly more nasopharyngeal bacteria coated with IgG than with SIgA (p < 0.001). The OP children had significantly fewer SIgA-coated bacteria (p < 0.05) but more C3b-coated bacteria (p < 0.01) in the NPH than the NOP children had. No significant difference was noted between the two groups regarding IgG coating. The occurrence of Branhamella catarrhalis in the NHP was more pronounced in the OP group (p < 0.05). No significant differences in the occurrence of other middle ear pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus) or quantitative dominance of pathogens were noted between the two groups. Deficiency in SIgA coating of the nasopharyngeal bacteria may contribute to the otitis-prone condition.

The membranous tonsillitis during infectious mononucleosis is nevertheless of bacterial origin

Samples from the fur covering the palatine tonsils of 10 patients with infectious mononucleosis (IM) were subjected to fluorescence microscopy after staining with acridine orange. Standard aerobic cultures from swabs were set up simultaneously. The fur constituted a mass of variously sized cocci and rods intermingled with granulocytes and cellular detritus. Five patients had growth of beta-haemolytic Streptococci on the tonsils. Bacteria in abundance were found attached to the tonsillar epithelial cells. The B-lymphotrophic Epstein-Barr virus, responsible for the IM infection, causes an immense increase in the bacterial colonization of the tonsillar surfaces, probably due to an increased attachment of bacteria to the tonsillar epithelial cells.

Bacterial attachment in vivo to epithelial cells of the nasopharynx during otitis media with effusion

Epithelial cells were obtained by swabbing the posterior wall of the nasopharynx (NPH) of 15 patients (age one to 6 8/12 years; eight males, seven females) undergoing ENT-surgery under general anaesthesia for otitis media with effusion (OME). Individually matched, ear healthy children served as controls. Bacteria attached to the non-ciliated cells were calculated according to a method described. Furthermore, quantitative and qualitative bacteriological analyses were performed on samples obtained from mucoid middle ear effusion material as well as from the NPH. All patients and controls harboured middle ear pathogens (S. pneumoniae, H. influenzae, B. catarrhalis, or S. aureus) in the NPH. Only 33 per cent of the patients harboured middle ear pathogens in the middle ear effusion and the same pathogen was invariably found in the corresponding NPH. Attachment of bacteria to the non-ciliated cells of the NPH diminished significantly with growing age in the ear healthy control group but not in the OME group. OME is closely correlated to the presence of middle ear pathogens in the NPH and to attachment of bacteria to the epithelial cells in the NPH.

Immunoglobulin- and complement-coated bacteria in middle ear effusions during the early course of acute otitis media

We used an immunofluorescence assay to investigate the content of secretory IgA- (SIgA), IgG-, IgM- and C3b-coated bacteria in middle ear effusions obtained within 12-72 h after the onset of acute symptoms of purulent otitis in 28 patients (37 ears). Simultaneously we analyzed the bacteria, both qualitatively and quantitatively, using standard culturing methods and fluorescein conjugated (FITC) antibodies to Haemophilus influenzae and Streptococcus pneumoniae. The ages of the patients were in the range of 5 months to 17 years; 18 were males and 10 females. 73% of the samples harboured no antibody- or C3b-coated bacteria, and particularly those of young patients (< 20 months). 92% of the samples were culture-positive, while 8% showed dormant bacteria. The predominant species were S. pneumoniae and H. influenzae. In 8% of the samples there was heavy and in 11% slight peripheral SIgA-coating of the 5% showed heavy and 19% slight peripheral IgG-coating. Only 3 samples were intensely opsonized, i.e. the bacteria were coated with IgG and C3b simultaneously. In most cases of acute purulent otitis media, the middle ear cavity of young individuals is not able to coat pathogens with SIgA, IgG, IgM and C3b during the early course of infection.