Antimicrobial factors and bacterial correlation in chronic otitis media with effusion

The immunoregulatory and allergy-associated cytokines in the aetiology of the otitis media with effusion

Inflammation in the middle ear mucosa, which can be provoked by different primary factors such as bacterial and viral infection, local allergic reactions and reflux, is the crucial event in the pathogenesis of otitis media with effusion (OME). Unresolved acute inflammatory responses or defective immunoregulation of middle inflammation can promote chronic inflammatory processes and stimulate the chronic condition of OME. Cytokines are the central molecular regulators of middle ear inflammation and can switch the acute phase of inflammation in the chronic stage and induce molecular-pathological processes leading to the histopathological changes accompanying OME. In this review we present cytokines identified in otitis media, immunoregulatory [interleukin (IL)-2, IL-10, transforming growth factor-beta]) and allergy associated (IL-4, IL-5, granulocyte-macrophage colony-stimulating factor), as crucial molecular regulators, responsible for chronic inflammation in the middle ear and the chronic condition of OME.

Experimental studies on round window structure: function and permeability

Current research and an overall review of 12 years of round window membrane studies is presented. The approach, rationale, and concepts that have evolved from the studies are described. An ultrastructural study of the round window membrane of rhesus monkeys disclosed three basic layers: an outer epithelium, a middle core of connective tissue, and an inner epithelium. Morphologic evidence in monkeys, cats, and chinchillas suggests that these layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear. Cationic ferritin, horseradish peroxidase, 1-micron latex spheres, and neomycin-gold spheres placed in the middle ear of these experimental animals were observed to traverse the round window membrane through pinocytotic vesicles. Three-micron latex spheres and anionic ferritin were not incorporated by the membrane. Cationic ferritin and 1-micron latex spheres placed in perilymph were incorporated by the inner epithelial cells, suggesting absorptive capabilities of the round window membrane. Cationic ferritin was observed within the mesothelial cells underlying the scala tympani side of the basilar membrane, suggesting a role for these cells in the inner-ear defense system. A review of the subject and a general perspective from the author's viewpoint are discussed.

Prognosis and endotoxin contents in middle ear effusions in cases after acute otitis media

We analysed the endotoxin content of middle ear effusion (MEE) from patients after acute otitis media, by a Limulus assay. Endotoxin was positive in 70% of the cases treated with antibiotics at an acute event for more than 5 days, while the incidence of bacteria was only 22%. One month after the sample collection, cases with a high concentration of endotoxin in MEE still tended to have effusion. These results suggest that endotoxin in MEE cannot be easily inactivated and may be involved in the development of acute otitis media into chronic otitis media with effusions.

Normal distribution of lysozyme- and lactoferrin-secreting cells in the chinchilla tubotympanum

The distribution of the antibacterial enzyme lysozyme- and lactoferrin-secreting cells in the tubotympanum of normal chinchillas was studied using an immunohistochemical technique. The middle ear mucosa contained lysozyme-secreting cells and lactoferrin-secreting cells. The former were localized primarily in the columnar epithelium area and the latter primarily in the cuboidal epithelium area (that contains serous cells) of the transitional zone. In the eustachian tube, the lysozyme was localized in goblet cells of the mucosal epithelium and mucous cells of the glands, while lactoferrin was localized in serous cells of the glands. Our results indicate that secretory lysozyme and lactoferrin are secreted by different cell types (mucous or serous), supporting the notion of heterogeneity of the secretory cells of the tubotympanum. This finding is consistent with the concept that antibacterial enzyme secretion is an integral part of the normal mucosal defense system in the tubotympanum.

Recurrent acute otitis media--prophylactic penicillin treatment: a prospective study. Part I

Recurrent acute otitis media (RAOM) is a distressing clinical manifestation of middle ear pathology, mainly expressed in the first two years of life. In this controlled study, prophylactic treatment by phenoxymethyl penicillin reduced significantly the frequency of RAOM in 60 children, as compared to 48 children who received a short ampicillin course only on the occasion of an acute otitis media episode. The importance of breastfeeding, age at initial episode, the type of treatment given and the pertinent literature is discussed. A working hypothesis of this prophylactic treatment is suggested.

Bacterial and Polymorphonuclear Leukocyte Contribution to Middle Ear Inflammation in Chronic Otitis Media with Effusion

Bacteria can be cultured from approximately one third of chronic middle ear effusions, yet the contribution of these bacteria to the pathogenesis of chronic otitis media with effusion (OME) is not clear due to the absence of signs and symptoms of acute infection in most children with this disease. To explore the role of bacteria in chronic OME, lysozyme, lactoferrin, serum complement factors C3 and C5a, and polymorphonuclear leukocyte (PMNL) chemotaxin content was measured in 21 chronic middle ear effusion samples. Concentrations of lysozyme, lactoferrin, and chemotaxin were significantly higher in culture-positive than in sterile effusions. Lysozyme appeared to be contributed by both PMNL and non-PMNL sources in the middle ear space. These non-PMNL sources, presumably middle ear epithelial cells, accounted for 50% to 80% of the lysozyme variation in middle ear effusion. Although C3 and C5a were present in effusion, chemotaxin content correlated poorly with the C3 and C5a content, suggesting that chemotaxins were derived from bacterial peptides rather than from complement activation products. These results suggest that bacteria contribute to chronic middle ear inflammation with effusion. The eradication of bacteria from chronic middle ear effusion might disrupt the host responses which maintain chronic OME.

Secretory otitis media: microbiology of the middle ear and the nasopharynx

Specimens for bacterial culture were obtained from 117 children with secretory otitis media (SOM). From the nasopharynx Streptococcus pneumoniae, Haemophilus influenzae, Branhamella catarrhalis and group A streptococci were isolated in 79% of the patients. Of 168 ear exudates, 30 yielded growth (18%) from 26 of the patients (22%). Pneumococcal capsular polysaccharides could not be detected in exudates assayed by counterimmunoelectrophoresis. The recovery rate of bacteria from the ear exudates was significantly higher in patients with positive than with negative nasopharyngeal culture (p less than 0.05). The nasopharyngeal pathogens invading the middle ear in SOM seem to survive there for a period of time and are then replaced by other strains according to the fluctuation of the nasopharyngeal flora where approximately 40% of the strains were eliminated and replaced by other strains over a period of 12 to 13 days.

Biochemical and immunochemical characteristics of middle ear effusions in relation to bacteriological findings

Experimental otitis media was produced in chinchillas by eustachian tube obstruction or pneumococcal infection. Sequential changes in the histology of the middle ear mucosa and enzyme profile of the middle ear effusions (MEE) were studied. In serous otitis media (SOM) which followed tubal obstruction, the subepithelial space was widened by edema and capillary dilatation, and the middle ear space was filled with serous fluid. Slight hyperplasia of epithelial cells was also observed. The subepithelial space remained widened with mild fibrous change and capillary dilatation, and slight hyperplasia of epithelial cells persisted 42 days after obstruction. In purulent otitis media (POM), which followed inoculation of pneumococci into the middle ears, metaplasia of the epithelial layer from flat to columnar cells was observed. The subepithelial space was widened with loose fibrous connective tissue proliferation, vascular dilatation and inflammatory cell infiltration. Both lactate dehydrogenase (LDH) and lysozyme levels in MEE were higher in the POM group than in the SOM group. When bacterial enzymes, hyaluronidase and lipase activity were measured in MEE and plotted together with the percentage of positive culture of the MEE at different times after the experimental infection, the enzyme activities decreased with the clearing of bacteria and along with the resorption of inflammatory changes of middle ear mucosa evidenced by histology. In human MEE studies, immunoglobulins (IgG, IgA, IgM) of MEE were higher than in serum except IgM in serous MEE. The IgG content of MEE in the culture-negative group was higher than in the culture-positive group. Possible mechanisms for this difference were discussed.

Evaluation of countercurrent immunoelectrophoresis as a diagnostic tool in bacterial otitis media

The diagnostic efficiency of countercurrent immunoelectrophoresis (CIE) and correlation of clinical and bacteriological data were studied in 184 middle ear effusions (MEE) from 125 patients diagnosed as acute primary, acute recurrent otitis media, and chronic MEE. Significant differences between stage of otitis media (OM), patient age and type of MEE were found. Streptococcus pneumoniae was isolated in 22% of the overall MEE, 26% in the acute primary and 26% in acute recurrent OM. Among the S. pneumoniae isolates, 82.5% were detected by CIE and culture, 15% only by culture and 2.5% only by CIE. Most S. pneumoniae isolates identified by culture and CIE were in a purulent MEE (64%) while those identified by culture only were in a mucoid MEE (67%). Haemophilus influenzae overall incidence was 29%; 13% of them produced beta-lactamase and only 4% were serotype b. The H. influenzae serotype b strains were detected by culture as well as CIE, so the overall effectiveness of CIE for S. pneumoniae and H. influenzae serotype b was 19.5% and 22 to 23% for acute primary and recurrent OM. Sterile cultures were obtained in 37.5% of the overall MEE. The CIE seems to be a useful screening test, culture remaining the method for definitive bacterial identification in MEE.

Cells involved in the middle ear defense system

Despite the high incidence and prevalence of otitis media, its pathogenesis is not thoroughly understood. In the last decade, many efforts have been made to provide a better understanding, and abundant information has become available. At the same time the field of immunology has advanced at an extremely rapid pace. We have followed the gradual cellular events in the defense reaction of the middle ear, utilizing eustachian tube obstruction to induce otitis. Seventy-five cats were divided in groups and sacrificed at intervals between one day and six months, and their temporal bones were studied. During an initial phase of inflammation, polymorphonuclears appear at three days in connective tissue; at the same time active fibroblasts synthesize tropocollagen and ground substance while epithelial cells secrete mucus and lysozymes. These cells, together with those involved in the mucociliary transport system and a patent functional eustachian tube, constitute the nonspecific system of defense. The transition cells are the macrophages which appear at one week to interact with T and B cells to produce the specific immune response. Plasma cells appear at two weeks to peak at one month with synthesis of immunoglobulins A, G and M. A secretory immune system is observed. At three and six months, lymphocytes are the predominant cells and occasional accumulations of mononuclears are observed. The reaction involves the entire middle ear, including mucoperiosteum, middle ear muscles and round window membrane. We believe that a better understanding of the middle ear defense system will lead in time to a practical clinical assessment of the immunological status during the evolution of each particular process or disease involving the middle ear, and a more rational approach to the treatment and, hopefully, prevention of chronic ear disease.

Acute gram-negative bacillary infections of middle ear and mastoid

Thirty-three patients with acute purulent otitis media and mastoiditis caused by Gram-negative bacilli are presented. The main features of the disease include: predilection for young male infants, a high rate of complications that include sepsis, mastoiditis and osteomyelitis of the base of the skull. Patients that are diagnosed early respond well to drainage and ventilation of the infected middle ear combined with in vitro effective antibacterial therapy. Patients that receive prior inappropriate antibacterial therapy tend to have prolonged courses and require mastoid surgery. It is suggested that early myringotomy and bacterial cultures be performed in all patients with acute middle ear infections.

Lysozyme activity and immunoglobulins in middle ear effusion fluid in acute purulent otitis media and in otitis media with effusion

147 samples of punctured middle ear effusion fluid from cases of otitis media with effusion and 150 samples from patients with acute purulent otitis media were tested for lysozyme activity. In otitis media with effusion the concentration was 182.0 U/ml, in acute otitis 433.8 U/ml. The lysozyme concentration in otitis media with effusion depended upon the nature of the effusion. Serous fluid showed an activity of 124.8 U/ml and mucoid 311.6 U/ml, respectively. In culture-positive cases of acute otitis media the lysozyme level was 423.4 U/ml. Culture-negative cases showed about the same concentration, 438.3 U/ml. The possible role of lysozyme in defence systems of the middle ear is discussed.

Lymphocyte morphology in mucoid middle ear effusions

Cytologically, the mucoid middle ear effusions could be divided into a lymphocyte-monocyte type and a type where the granulocytes predominated. By alpha-naphthyl-acetate esterase (ANAE) staining procedure the T lymphocytes were found to make up the majority of lymphocytes in the first type, often accompanied by large numbers of ANAE-positive macrophages. In the second type the relative and particularly the absolute numbers of T cells were smaller. The T lymphocytes in aural effusions, distributed in agreement with their normal distribution in blood, could be the basis of possible delayed hypersensitivity immune mechanisms in the middle ear, but definite proof, either demonstrating receptor molecules directed to antigens or a specific response by T cells, is still lacking.

Experimental otitis media with effusion: an immune-complex-mediated response

The possibility that immune complexes cause otitis media with effusion (OME) has been previously proposed. In order to test this hypothesis we developed an animal model in which immune complexes were injected into the middle ears of chinchillas and the animals killed at various time intervals thereafter. Moderate inflammatory changes were seen in animals killed four hours postinjection, whereas intense inflammation was observed in those killed at 24 hours. Inflammatory changes observed included capillary dilatation with increased capillary permeability, migration of polymorphonuclear leukocytes into the sub-mucosa, hemorrhage, and damage to and actual disruption of the subepithelial basement membrane. These changes are consistent with a complement-mediated acute inflammatory reaction. Although no definite conclusion can be made concerning the etiologic role of immune complex in OME, our findings show that immune complexes can cause acute inflammatory changes in the middle ear of the experimental animal.

Microorganisms in chronic otitis media with effusion

A total of 175 effusions obtained from 172 patients suffering from chronic otitis media with effusions was examined for bacterial smear and culture. Eighty percent showed positive bacterial smear, but only 49% yielded positive bacterial culture. The mucoid effusions had positive cultures in only 37%, whereas the bacterial culture rate was higher in serous (59%) and leukocytic (64%) types. The isolation of common pathogens accounted for about 50% of the isolates, and nonpathogens accounted for the remaining 50%. The high incidence of microorganisms in the middle ear effusions in the present series raises the possibility of bacterial contribution in many cases of OME.