Vaccination for the prevention of acute otitis media: proof of concept and current challenges

Mouse models for the study of mucosal vaccination against otitis media

Otitis media (OM) is one of the most common infectious diseases in humans. The pathogenesis of OM involves nasopharyngeal (NP) colonization and retrograde ascension of the pathogen up the Eustachian tube into the middle ear (ME). Due to increasing rates of antibiotic resistance, there is an urgent need for vaccines to prevent infections caused by the most common causes of bacterial OM, including nontypeable Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis. Current vaccine strategies aim to diminish bacterial NP carriage, thereby reducing the likelihood of developing acute OM. To be effective, vaccination should induce local mucosal immunity both in the ME and in the NP. Studies in animal models have demonstrated that the intranasal route of vaccination is particularly effective at inducing immune responses in the nasal passage and ME for protection against OM. The mouse is increasingly used in these models, because of the availability of murine reagents and the existence of technology to manipulate murine models of disease immunologically and genetically. Previous studies confirmed the suitability of the mouse as a model for inflammatory processes in acute OM. Here, we discuss various murine models of OM and review the applicability of these models to assess the efficacy of mucosal vaccination and the mechanisms responsible for protection. In addition, we discuss various mucosal vaccine antigens, mucosal adjuvants and mucosal delivery systems.

Intranasal vaccination of neonatal mice with polysaccharide conjugate vaccine for protection against pneumococcal otitis media

Streptococcus pneumoniae is the leading bacterial cause of acute otitis media (OM) in young children, and can often produce invasive disease. Typical intramuscular routes of vaccination are poorly protective against development of OM. In the present study, we intranasally (i.n.) inoculated neonatal 1-week-old mice with pneumococcal polysaccharide conjugate vaccine using IL-12 as a mucosal adjuvant. The protective efficacy of this treatment was tested by challenging immunized infant (3-week-old) mice with bacteria to induce OM and invasive disease. i.n. vaccination was found to enhance levels of specific antibodies in middle ear (ME) washes and sera from wild-type (but not IFN-gamma(-/-)) mice. Immunization in the presence of IL-12 resulted in enhanced clearance of S. pneumoniae from the ME. Opsonization of bacteria with ME wash fluids or sera from immunized mice caused increased bacterial clearance from the ME of naïve mice. In addition, immunized mice demonstrated 89% survival after OM-induced invasive pneumococcal infection, compared to 22% survival in unvaccinated mice. These results indicate that i.n. vaccination of neonatal mice in the presence of IL-12 is able to enhance IFN-gamma dependent ME mucosal and systemic immune responses to pneumococci and efficiently protect against both OM and invasive infection.

Current concepts in antibiotic resistance

PURPOSE OF REVIEW

Although antibiotic resistance is not often considered an exciting topic for pediatric surgical subspecialists, we face the consequences of increasing antibiotic resistance daily in our clinical practice. By the very nature that our patients are often referred to us after extended periods of medical therapy, antibiotic resistance becomes a significant factor in management of patients both medically and surgically. Antibiotic resistance is increasing, and a number of organisms demonstrate multiple-drug resistance. The purpose of this review is to outline the scope of antibiotic resistance as it relates to pediatric otolaryngology. Specifically, the mechanisms of resistance, the pharmacodynamics involved, and selected infections are discussed.

RECENT FINDINGS

The children particularly at risk for infections with resistant organisms are those 2 years of age or younger with exposure to daycare and treatment with antimicrobials within the last 30 days. Although there is increasing resistance to antibiotics commonly used for outpatient infections such as otitis media, sinusitis, and tonsillitis, many of the first-line therapies still show significant therapeutic advantage. Vaccines to pneumococcal bacteria have been shown to decrease severe infections. However, there has been only a slight decline in the number of outpatient otolaryngologic infections after vaccination.

SUMMARY

Therefore, children who have received multiple courses of antibiotics, are 2 years of age or younger, attend daycare, or have received antimicrobial therapy within the last 30 days may need high-dose therapy or antimicrobial therapy with an increased spectrum of coverage. Those children with infections that do not respond clinically to appropriate therapy should be treated with the suspicion of multiple-drug resistant strains being present. Continued surveillance of resistance patterns within individual communities, especially areas served by children's hospitals, are important, as there are distinct local and regional differences in antimicrobial resistance.