Treatment of experimental acute otitis media with ibuprofen and ampicillin

Biofilm formation by Streptococcus pneumoniae strains and effects of human serum albumin, ibuprofen, N-acetyl-l-cysteine, amoxicillin, erythromycin, and levofloxacin

Streptococcus pneumoniae ability to produce biofilms may induce persistent infections and difficulties for eradication in vivo. We investigated the ability of 11 pneumococcal strains (serotypes 3, 6B, 9V, 19F, and 23F) to form biofilms on polystyrene plates at 16 and 24 h. The extent of biofilm was greater at 24 h in 10 strains, being the highest magnitude for serotype 3 strains. Human serum albumin at 25,000 microg/mL and ibuprofen at 128 microg/mL significantly reduced biofilm formation in 7 and 5 strains, respectively. Amoxicillin, erythromycin, and levofloxacin at supra-MIC concentrations were very active against planktonic cells of 3 selected strains but lower on biofilm-associated organisms in 2 strains and null against the third. Although N-acetyl-l-cysteine had very little activity against both planktonic and biofilm-forming organisms, when combined with the 3 antibiotics, a slightly enhanced activity against biofilm-embedded organisms in 1 strain and combined with amoxicillin in another one was observed.

The role of inflammatory mediators in the pathogenesis of otitis media and sequelae

This review deals with the characteristics of various inflammatory mediators identified in the middle ear during otitis media and in cholesteatoma. The role of each inflammatory mediator in the pathogenesis of otitis media and cholesteatoma has been discussed. Further, the relation of each inflammatory mediator to the pathophysiology of the middle and inner ear along with its mechanisms of pathological change has been described. The mechanisms of hearing loss including sensorineural hearing loss (SNHL) as a sequela of otitis media are also discussed. The passage of inflammatory mediators through the round window membrane into the scala tympani is indicated. In an experimental animal model, an application of cytokines and lipopolysaccharide (LPS), a bacterial toxin, on the round window membrane induced sensorineural hearing loss as identified through auditory brainstem response threshold shifts. An increase in permeability of the blood-labyrinth barrier (BLB) was observed following application of these inflammatory mediators and LPS. The leakage of the blood components into the lateral wall of the cochlea through an increase in BLB permeability appears to be related to the sensorineural hearing loss by hindering K⁺ recycling through the lateral wall disrupting the ion homeostasis of the endolymph. Further studies on the roles of various inflammatory mediators and bacterial toxins in inducing the sensorineumral hearing loss in otitis media should be pursued.

Expressions of cyclooxygenase 1 and 2 in endotoxin-induced otitis media with effusion in the rat

OBJECTIVE

Recently, a selective COX-2 inhibitor was developed and used for reducing the levels of inflammation-inducing prostaglandin (PG) whilst not inhibiting the release of protective PG by COX-1. COX-1 may be the critical isoform required for the production of PG with a homeostatic function, whereas COX-2 may be the main contributor to PG production in inflammation. The purpose of this study was to investigate COX-1 and 2 expressions in experimental endotoxin-induced OME in rats and to quantify their temporal expressions.

METHODS

In a rat model, lipopolysaccharides (LPS) were inoculated into the middle ear cavity. Middle ear mucosa and temporal bone were samples at 0, 1, 3, 6, and 12h, and on days 1, 3 and 7 after instilling either LPS or sterile PBS. RT-PCR, Western blotting and immunohistochemical staining were performed to determine the expressions of COX-1 and COX-2.

RESULTS

COX-1 mRNA and protein were detected in normal middle ear mucosa but their levels did not change after endotoxin instillation. However, COX-2 was not identified in normal middle ear mucosa, but COX-2 mRNA was maximally increased at 6h after endotoxin instillation and COX-2 protein was maximally increased at 12h. COX-2 expression, by immunohistochemical staining, was identified only at 12h after endotoxin injection.

CONCLUSIONS

In this study, the basal expressions of COX-1 and COX-2 mRNA and protein in middle ear mucosa, as well as their regulations by endotoxin were investigated. COX-1 was not induced in middle ear mucosa by endotoxin whereas COX-2 was induced within 12h of stimulation. Our findings indicate that COX-2 inhibitor administration for the relief of inflammation should be considered within 12h of the initiation of an inflammatory process. These findings may provide an understanding of the mechanisms regulating PG formation in infection of the middle ear cavity.

Cyclooxygenase 2 expression in otitis media with effusion

OBJECTIVES

To study whether cyclooxygenase 2 (COX-2) plays a role in the development of otitis media with effusion (OME).

STUDY DESIGN/METHODS

An experimental model of endotoxin-induced OME was used in healthy BALB/c mice. Solutions of Salmonella typhimurium endotoxin were injected into the middle ears of the mice, and COX-2 expression in the middle ears was studied using reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization (ISH).

RESULTS

Analysis by RT-PCR showed that COX-2 expression in the middle ear increased in a dose-dependent fashion after injection of endotoxin. ISH demonstrated that COX-2 had distinct expression patterns in the epithelium of middle ears with endotoxin-induced OME. COX-2 expression, however, was not detected in normal middle ears.

CONCLUSIONS

COX-2 expression may be one factor contributing to the development of OME.

Studies in otitis media: Children's Hospital of Pittsburgh-University of Pittsburgh progress report--2004

OBJECTIVES/HYPOTHESIS

The present Progress Report has summarized the key otitis media clinical trials and laboratory studies conducted since 1969 by investigators at the Children's Hospital of Pittsburgh-University of Pittsburgh (Pittsburgh, PA).

STUDY DESIGN

Review.

METHODS

Included in the discussion are the following: 1) studies of the epidemiology and risk factors; 2) anatomy and pathology of the eustachian tube-middle ear from human temporal bone histopathological specimens; 3) physiology and pathophysiology of the eustachian tube-middle ear in humans and animal models; 4) pathogenesis; 5) otitis media in special populations (e.g., patients with cleft palate, Native Americans, patients with Down syndrome); 6) microbiology; 7) diagnosis; 8) outcomes of randomized clinical trials that evaluated efficacy of nonsurgical and surgical methods of treatment and prevention; 9) studies of certain complications and sequelae (e.g., effect of middle-ear effusion on hearing, early child development, and the vestibular system; chronic suppurative otitis media). Also included are relevant summary tables and 256 references.

Effect of 10 pharmacologic probes on mRNA levels of inducible nitric oxide synthetase and selected inflammatory cytokines in a rat model of acute otitis media

Ten drugs were screened for their ability to decrease inflammatory mediator (IL-6, inducible nitric oxide synthetase [iNOS], IL-1beta and monocyte chemotactic protein [MCP-1]) expression in a rat model of acute otitis media caused by Streptococcus pneumoniae. Six adult rats were randomly assigned to each of 12 groups corresponding to uninfected controls and treatments with saline, aminoguanidine, anisomycin, dexamethasone, ketorolac, L-N(G)-nitroarginine methylester, methylprednisolone, mycophenolic acid, pentoxiphylline, tacrolimus or WEB2086. Forty-eight h after the start of treatment, the ears of the animals in the 11 treatment groups were challenged with S. pneumoniae. Forty-eight h later, all animals were killed and middle ear mucosa was harvested and assayed for RNA message. Messages for IL-6, iNOS and MCP-1 were significantly increased as a result of infection. Most treatments decreased MCP-1 and four decreased IL-6 and iNOS. Tacrolimus and dexamethasone decreased IL-6, iNOS and MCP-1. These results show that pharmacological agents can modify the expression of inflammatory mediators in this model and may have clinically relevant effects.

Upregulation of messenger RNA for inflammatory cytokines in middle ear mucosa in a rat model of acute otitis media

A rat model for acute otitis media has been established and was used to delineate the temporal expression of messenger RNA for key inflammatory cytokines. Inoculation with live Streptococcus pneumoniae induced a rapid expression of tumor necrosis factor alpha (within 6 hours) followed by upregulation of message for interleukin (IL)-6 (peak at 12 to 24 hours, remaining elevated through 120 hours) and IL-10 (peak at 24 hours). Inducible nitric oxide synthase message was also selectively increased following live bacterial inoculation (peak at 12 to 24 hours). Although there was a detectable inflammatory response to killed bacteria, it was minimal, was of short duration, and preceded the peak for live bacteria; only expression of IL-6 was significantly increased in this group (peak at 12 hours, remaining elevated through 72 hours). We interpret this to be due to an inflammatory response to bacterial products (such as lipopolysaccharide) in the heat-killed bacterial inoculum. The phosphate-buffered saline (PBS)-inoculated group exhibited a transient increase of IL-6 message, which indicates that this cytokine is a sensitive marker of the acute response to trauma. Otherwise, PBS invoked only a slight reaction in the mucosa with respect to the other inflammatory mediators being measured.

The role of inflammatory mediators and anti-inflammatory drugs in otitis media

Despite multiple studies, the role of anti-inflammatory drugs in the treatment of AOM and OME is unclear. Although the AHCPR was against the use of steroids in OME, other studies suggest a possible role with potential cost savings and a decrease in the need for surgery in some patients. But the risk-benefit ratio of steroid treatment is unclear. There is some evidence that NSAIDs may decrease otalgia associated with AOM, but no proof that NSAIDs reduce or prevent inflammatory changes in the middle ear associated with AOM and OME.

Eicosanoid synthesis and inactivation in healthy and infected chinchilla middle ears

Otitis media (OM) is an inflammatory reaction of the middle ear (ME) elicited by a variety of stimuli including tubal obstruction, allergy and bacterial infection. The leukotrienes and prostaglandins are among the earliest mediators produced in response to these insults. Their measured levels in human and animal models span a broad range of concentrations. However, their baseline levels and metabolic fates are unknown for the ME. Their dynamics in the ME were examined using the chinchilla animal model, tritiated eicosanoids and a lavage procedure. Prostaglandin levels in the normal ME were 10 times higher than the 34 pg/ear observed for the leukotrienes and thromboxane B2. These levels were significantly increased by the calcium ionophore A23187 and bacterial infection. Leukotrience C4 was the most and prostaglandin E2 the least persistent eicosanoid in the ME. Their residence time in the ME was increased by infection. The rank order of eicosanoid concentrations among comparable studies was surprisingly constant, with prostaglandin E2 the most abundant and the leukotrienes the least. Comparisons of eicosanoid levels from A23187 stimulation and the infectious models sampled at 3 days suggest that the higher levels observed in the infectious models may represent basal eicosanoid production for hyperplastic ME mucosa.

Efficacy of clarithromycin treatment of acute otitis media caused by infection with penicillin-susceptible, -intermediate, and -resistant Streptococcus pneumoniae in the chinchilla

Because of the increasing frequencies of recovery of penicillin-resistant Streptococcus pneumoniae from the middle ears of children with acute otitis media, non-beta-lactam antibiotics are being explored as treatment alternatives to amoxicillin. In this study, the efficacy of a 10-day course of clarithromycin was evaluated with chinchillas. After the pharmacokinetic profiles for clarithromycin were established, 180 animals were assigned to one of three susceptibility groups (n = 60/group; penicillin-susceptible, -intermediate, and -resistant S. pneumoniae), and the right middle ear was infected with the appropriate strain of S. pneumoniae. Equal numbers of animals in each group were treated orally beginning on day 2 with a 10-day course of clarithromycin (15 mg/kg of body weight; given twice a day) or amoxicillin as a control (20 mg/kg twice a day). On days 4, 9, and 13, otomicroscopy and tympanometry were performed, and on day 13, the middle ears were cultured for bacteria. The results showed 100% eradication of the challenge organism in both treatment groups for the susceptible strains of S. pneumoniae. Cultures were negative in 87 and 74% (P > 0.05) of the animals challenged with the intermediate resistant strains and in 100 and 56% (P < 0.05) of the animals challenged with the resistant strains and treated with clarithromycin and amoxicillin, respectively. There were no differences between treatments in the diagnosis of effusion for any group. These results support the use of the chinchilla to evaluate drug efficacy in the treatment of acute otitis media and show clarithromycin to be effective in sterilizing the middle ears of animals challenged with penicillin-susceptible, -intermediate, and -resistant strains of S. pneumoniae.