Ann Hermansson

A rat model for pneumococcal otitis media

The middle ears of 29 male Sprague-Dawley rats were injected with viable pneumococci, type 3 or 6A, and changes were monitored by otomicroscopy and analysis of bacterial samples from middle ear effusions, blood, and the nasopharynx. Depending on the type of pneumococci and its concentration, three responses were noted: otitis media with purulent effusion, otitis media with serous effusion, or no reaction. The mortality rate was low and the animals recovered without permanent deterioration or otomicroscopically discernable change. The results of this study show the rat to be a suitable animal model for the study of bacterial otitis media.

Acute mastoiditis in children aged 0-16 years—A national study of 678 cases in Sweden comparing different age groups

OBJECTIVE To compare the characteristics of acute mastoiditis in children in different age groups in order to identify risk groups and risk factors for acute mastoiditis. METHODS Records for all children aged 0-16 years treated for acute mastoiditis during 1993-2007 at 33 Ear, Nose and Throat departments in Sweden were reviewed retrospectively according to defined criteria for acute mastoiditis. RESULTS A total of 678 cases fulfilled the inclusion criteria. Acute mastoiditis was most common in children younger than two years of age and this group was characterized by less prior history of other diseases and ear diseases, fewer visits to health care centers and less antibiotic treatment before admission, shorter duration of symptoms before admission, hospitalization for fewer days and lower frequency of complications and mastoidectomies. These children also showed a higher incidence of clinical findings, increased inflammatory markers such as fever and heightened counts of C-reactive protein and white blood cells compared with older children. They also tested positive for significantly more samples of Streptococcus pneumoniae while the older children more often exhibited growth of Streptococcus pyogenes or Pseudomonas aeruginosa or no microbial growth. CONCLUSIONS The characteristics of pediatric acute mastoiditis differed significantly between age groups. Acute mastoiditis was most common in children younger than two years of age. They showed more rapid progress of symptoms and more distinct signs of acute mastoiditis. This is probably the reason why parents rapidly seek medical care for small children and hospital treatment thus starts earlier in the youngest children, which may in turn explain the excellent outcome. This study showed that younger children have neither more severe acute mastoiditis nor more complications than older ones. The differences between age groups suggest that there are distinctions in the pathophysiology behind the onset and course of acute mastoiditis in younger and older children.

Nontypeable and encapsulated Haemophilus influenzae yield different clinical courses of experimental otitis media

Middle ears of male Sprague-Dawley rats were injected with suspensions of thirteen Haemophilus influenzae strains of different sero- and biotypes and at various concentrations. Systemic and local changes were monitored by clinical observations, otomicroscopy, and analysis of bacterial samples from blood and middle ears. Two patterns of response were recognized, a nontypeable and an encapsulated pattern. The nontypeable H. influenzae middle ear infection required a high bacterial dose and was well past its peak 8 days after challenge, when the encapsulated H. influenzae otitis media was still purulent. The most severe infections were caused by H. influenzae type b strains. The overall mortality rate was zero and the animals recovered without permanent deterioration or otomicroscopically discernable changes. The results of this study show the rat to be a suitable animal model for the study of H. influenzae otitis media.

The Tympanic Membrane and Middle Ear Mucosa during Non-typeable Haemophilus influenzae and Haemophilus influenzae type b Acute Otitis Media: A Study in the Rat

Non-typeable Haemophilus influenzae (NTHi) and encapsulated Haemophilus influenzae type b (Hib) were inoculated into the middle ears of Sprague-Dawley rats. Tympanic membrane (TM) status was assessed otomicroscopically and specimens from various middle ear areas were prepared for light microscopy at various times during the acute phase and up to 6 months after inoculation. Irrespective of bacteria strain, acute otitis media (AOM) was present in all ears 4 days after inoculation. The Hib-infected ears showed initially a severe course of AOM, but all were otomicroscopically resolved by day 12, at which time a few NTHi-inoculated ears still exhibited middle ear effusion. The TMs infected with Hib had normalized without scar formation, whereas NTHi induced a persistent thickening of the TMs in half of all cases. The middle ear mucosa of NTHi-infected ears initially showed vigorous activity among the goblet cells, but the mucosa normalized after the acute phase. Hib, by contrast, induced prominent changes in the middle ear mucosa. Initially, no goblet cell granules or ciliated cells could be observed in the mucosa. Later on, the epithelium contained large, active goblet cells. Glands appeared beneath the mucosa which persisted as streaks of epithelial cells throughout the study period. The findings show that NTHi and Hib both induce AOM but with differing clinical courses, and affect different targets in the middle ear.

Effective Treatment of Experimental Acute Otitis Media by Application of Volatile Fluids into the Ear Canal

Essential oils are volatile and can have good antimicrobial activity. We compared the effects of oil of basil (Ocimum basilicum) and essential oil components (thymol, carvacrol, and salicylaldehyde) to those of a placebo when placed in the ear canal of rats with experimental acute otitis media caused by pneumococci or Haemophilus influenzae. Progress was monitored by otomicroscopic examination and middle ear cultures. The treatment with oil of basil or essential oil components cured or healed 56%-81% of rats infected with H. influenzae and 6%-75% of rats infected with pneumococci, compared with 5.6%-6% of rats in the placebo group. Essential oils or their components placed in the ear canal can provide effective treatment of acute otitis media.

Moraxella catarrhalis-induced purulent otitis media in the rat middle ear. Structure, protection, and serum antibodies.

To study the effects of viable and heat‐killed Moraxella catarrhalis bacteria on the middle ear mucosa and to evaluate the protection after whole‐cell immunizations, Sprague‐Dawley rats were challenged and rechallenged with four different M. catarrhalis strains. The animals were monitored by clinical observations, bacterial and histological samples from middle ears, and serum IgG levels. Only viable bacteria at a high concentration induced purulent otitis media, which was culture positive in 58% of the cases on day 4. The infection was characterized by a mild acute reaction lasting otomicroscopically about 8 days, together with quantitative and qualitative changes of the goblet cells. Structurally the mucosal effects of the heat‐killed bacteria were less pronounced in the early phase compared to the viable bacteria, but similar at the end of the experiment at 6 months. The intrabullar and subcutaneous immunizations evoked an IgG antibody response in all animals, and the protection rate after immunization was 50% or more. The induced protection was not strain‐specific. The study showed the rat to be a possible alternative for the study of different aspects of M. catarrhalis otitis media, an infection that is clinically and structurally different from that elicited by Streptococcus pneumoniae and Haentophilus influenzae in the rat.

Polyp pathogenesis--a histopathological study in experimental otitis media.

We examined the mucosa of 50 rat middle ears in an experimental model of acute otitis media, in order to obtain information on the mechanisms of polyp formation. The right middle ear of 25 rats was inoculated with type 3 pneumococci, and the left ear served as a control. The animals were killed, the middle ear bulla removed, and the mucosa was dissected from the bone, stained PAS-alcian blue and embedded as a whole-mount. The whole-mounts were examined in a light microscope for polypous mucosal prominences. Serial sections were made of all polyps, and of relevant parts of the mucosa. 15 polyps were found in 11 (44%) of 25 infected ears; none were found in normal control ears. Goblet cell density was increased in polyps and the surrounding epithelium. Epithelial microruptures were seen in areas with widespread intra-epithelial liquid vacuoles and subepithelial accumulation of liquids, luminally migrating inflammatory cells, increased vascularization and edema. Connective tissue of the lamina propria was prolapsed through most ruptures. Some prolapses showed signs of re-epithelialization, while others had a full epithelial lining that resembled a fully developed polyp. Our findings support our earlier theory on nasal polyp pathogenesis, based on the following stages: i) Localized rupture of the epithelial lining. ii) Luminal protrusion of the lamina propria through the epithelial defect. iii) Re-epithelialization of protruded tissue, and formation of a polyp.(ABSTRACT TRUNCATED AT 250 WORDS)

Panel 4: Recent Advances in Otitis Media in Molecular Biology, Biochemistry, Genetics, and Animal Models

Background Otitis media (OM) is the most common childhood bacterial infection and also the leading cause of conductive hearing loss in children. Currently, there is an urgent need for developing novel therapeutic agents for treating OM based on full understanding of molecular pathogenesis in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM. Objective To provide a state-of-the-art review concerning recent advances in OM in the areas of molecular biology, biochemistry, genetics, and animal model studies and to discuss the future directions of OM studies in these areas. Data Sources and Review Methods A structured search of the current literature (since June 2007). The authors searched PubMed for published literature in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM. Results Over the past 4 years, significant progress has been made in the areas of molecular biology, biochemistry, genetics, and animal model studies in OM. These studies brought new insights into our understanding of the molecular and biochemical mechanisms underlying the molecular pathogenesis of OM and helped identify novel therapeutic targets for OM. Conclusions and Implications for Practice Our understanding of the molecular pathogenesis of OM has been significantly advanced, particularly in the areas of inflammation, innate immunity, mucus overproduction, mucosal hyperplasia, middle ear and inner ear interaction, genetics, genome sequencing, and animal model studies. Although these studies are still in their experimental stages, they help identify new potential therapeutic targets. Future preclinical and clinical studies will help to translate these exciting experimental research findings into clinical applications.

Healing of Tympanic Membrane after Myringotomy during Streptococcus Pneumoniae Otitis Media an Otomicroscopic and Histologic Study in the Rat

The purpose of our study was to elucidate the course of healing of the tympanic membrane (TM) when myringotomy was performed during acute otitis media. The early and long-lasting structural changes of the TM were studied in an animal model. Rats were inoculated with Streptococcus pneumoniae (PnC) type 3 in the bulla. When the infection was manifest, myringotomy was performed. On days 4 and 12, and 3 and 6 months after myringotomy, the TM status was checked by otomicroscopy and TMs were prepared for light and electron microscopy. Comparison was made with PnC-infected TMs that were not perforated, as well as myringotomized noninfected TMs. The infection resolved more slowly in myringotomized ears compared to PnC-infected ears that were left untouched. After 6 months, the pars tensa of the myringotomized infected ears was thickened and showed a disorganized collagen structure, compared with myringotomized noninfected ears, in which TMs were normalized. The PnC-infected TMs without myringotomy were completely normalized after 2 months. We conclude that a combination of bacterial infection and myringotomy causes long-lasting changes in TM structure. This impaired structure of the connective tissue could be of importance in chronic middle ear disease as a presumptive site for retraction and perforation of the TM.

Pneumococcal vaccination in children at risk of developing recurrent acute otitis media - a randomized study.

Aim:  Acute otitis media (AOM) is a common childhood disease, which often becomes recurrent (rAOM). A small reduction in AOM episodes has been noted in unselected child cohorts after vaccination with heptavalent conjugate pneumococcal vaccine (PCV7). The purpose of this study was to investigate how vaccination affects young children at risk of developing rAOM.