Amoxicillin middle ear fluid penetration and pharmacokinetics in children with acute otitis media

Challenges for global antibiotic regimen planning and establishing antimicrobial resistance targets: implications for the WHO Essential Medicines List and AWaRe antibiotic book dosing

SUMMARYThe World Health Organisation's 2022 AWaRe Book provides guidance for the use of 39 antibiotics to treat 35 infections in primary healthcare and hospital facilities. We review the evidence underpinning suggested dosing regimens. Few (n = 18) population pharmacokinetic studies exist for key oral AWaRe antibiotics, largely conducted in homogenous and unrepresentative populations hindering robust estimates of drug exposures. Databases of minimum inhibitory concentration distributions are limited, especially for community pathogen-antibiotic combinations. Minimum inhibitory concentration data sources are not routinely reported and lack regional diversity and community representation. Of studies defining a pharmacodynamic target for ß-lactams (n = 80), 42 (52.5%) differed from traditionally accepted 30%-50% time above minimum inhibitory concentration targets. Heterogeneity in model systems and pharmacodynamic endpoints is common, and models generally use intravenous ß-lactams. One-size-fits-all pharmacodynamic targets are used for regimen planning despite complexity in drug-pathogen-disease combinations. We present solutions to enable the development of global evidence-based antibiotic dosing guidance that provides adequate treatment in the context of the increasing prevalence of antimicrobial resistance and, moreover, minimizes the emergence of resistance.

A new strategy for the treatment of middle ear infection using ciprofloxacin/amoxicillin-loaded ethyl cellulose/polyhydroxybutyrate nanofibers

A middle ear infection occurs due to the presence of several microorganisms behind the eardrum (tympanic membrane) and is very challenging to treat due to its unique location and requires a well-designed treatment. If not treated properly, the infection can result in severe symptoms and unavoidable side effects. In this study, excellent biocompatible ethyl cellulose (EC) and biodegradable polyhydroxybutyrate (PHB) biopolymer were used to fabricate drug-loaded nanofiber scaffolds using an electrospinning technique to overcome antibiotic overdose and insufficient efficacy of drug release during treatment. PHB polymer was produced from Halomonas sp., and the purity of PHB was found to around be 90 %. Additionally, ciprofloxacin (CIP) and amoxicillin (AMX) are highly preferable since both drugs are highly effective against gram-negative and gram-positive bacteria to treat several infections. Obtained smooth nanofibers were between 116.24 and 171.82 nm in diameter and the addition of PHB polymer and antibiotics improved the morphology of the nanofiber scaffolds. Thermal properties of the nanofiber scaffolds were tested and the highest Tg temperature resulted at 229 °C. The mechanical properties of the scaffolds were tested, and the highest tensile strength resulted in 4.65 ± 6.33 MPa. Also, drug-loaded scaffolds were treated against the most common microorganisms that cause the infection, such as S.aureus, E.coli, and P.aeruginosa, and resulted in inhibition zones between 10 and 21 mm. MTT assay was performed by culturing human adipose-derived mesenchymal stem cells (hAD MSCs) on the scaffolds. The morphology of the hAD MSCs' attachment was tested with SEM analysis and hAD MSCs were able to attach, spread, and live on each scaffold even on the day of 7. The cumulative drug release kinetics of CIP and AMX from drug-loaded scaffolds were analysed in phosphate-buffered saline (pH: 7.4) within different time intervals of up to 14 days using a UV spectrophotometer. Furthermore, the drug release showed that the First-Order and Korsmeyer-Peppas models were the most suitable kinetic models. Animal testing was performed on SD rats, matrix and collagen deposition occurred on days 5 and 10, which were observed using Hematoxylin-eosin and Masson's trichrome staining. At the highest drug concentration, a better repair effect was observed. Results were promising and showed potential for novel treatment.

High-Dose vs Standard-Dose Amoxicillin Plus Clavulanate for Adults With Acute Sinusitis: A Randomized Clinical Trial

IMPORTANCE

Acute bacterial sinusitis is common, but currently recommended antibiotic treatment provides minimal benefit.

OBJECTIVE

To confirm the previous finding that high-dose amoxicillin plus clavulanate (with double the amount of amoxicillin) may be superior to standard-dose amoxicillin plus clavulanate in adults.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind, comparative-effectiveness randomized clinical trial was conducted from February 26, 2018, through May 10, 2020, at the academic primary care internal medicine and pediatrics practice of Albany Medical Center, located in Cohoes, New York. Participants included adults aged 18 years or older who were prescribed amoxicillin plus clavulanate for acute bacterial sinusitis diagnosed in accordance with the Infectious Diseases Society of America guidelines.

INTERVENTIONS

Amoxicillin 875 mg with clavulanate 125 mg plus either placebo (standard dose) or amoxicillin 875 mg (high dose) twice a day for 7 days.

MAIN OUTCOMES AND MEASURES

The primary efficacy outcome was a global rating of "a lot better" or "no symptoms" at the end of 3 days of treatment using a Global Rating of Improvement scale, with outcomes ranging from 1 (a lot worse) to 6 (no symptoms). The primary adverse effect outcome was severe diarrhea at 3 or 10 days after the start of treatment.

RESULTS

At an unplanned interim analysis prompted by COVID-19 restrictions, 157 of a projected 240 participants had been enrolled (mean age, 48.5 [range, 18.7-84.0] years; 117 women [74.5%]), with 79 randomized to the standard dose and 78 to the high dose; 9 and 12, respectively, withdrew or were lost to follow-up before the assessment of the primary outcome. At day 3, 31 of 70 participants (44.3%) in the standard-dose group reported a global rating of "a lot better" or "no symptoms," as did 24 of 66 (36.4%) in the high-dose group, for a difference of -7.9% (95% CI, -24.4% to 8.5%; P = .35). The study was, therefore, stopped for futility. Diarrhea was common in both groups by day 3, with any diarrhea reported in 29 of 71 participants (40.8%) receiving the standard dose and 28 of 65 (43.1%) receiving the high dose and severe diarrhea reported in 5 of 71 (7.0%) and 5 of 65 (7.7%), respectively.

CONCLUSIONS AND RELEVANCE

The results of this randomized clinical trial suggest that adults treated for clinically diagnosed acute sinusitis did not appear to benefit from taking high-dose compared with standard-dose amoxicillin plus clavulanate.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03431337.

Comprehensive Detection of Respiratory Bacterial and Viral Pathogens in the Middle Ear Fluid and Nasopharynx of Pediatric Patients With Acute Otitis Media

BACKGROUND

Acute otitis media (AOM) is a common ear infection caused by respiratory viruses and bacteria of the nasopharynx. The present study aimed to detect various respiratory viruses and bacteria in middle ear fluid (MEF) and nasopharyngeal aspirates (NPA) using polymerase chain reaction (PCR).

METHODS

We collected MEF and NPA samples from 122 pediatric patients with AOM. Real-time PCR detected 11 types of respiratory viruses (respiratory syncytial virus A/B, parainfluenza virus 1/2/3, human metapneumovirus, influenza virus A/B, adenovirus, human bocavirus and rhino virus) and 7 types of bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Streptococcus pyogenes, Legionella pneumophila and Moraxella catarrhalis). MEF specimens were also examined using bacterial culture.

RESULTS

At least 1 respiratory viral or bacterial pathogen was detected in MEF of 120 cases (98%) by viral and bacterial PCR and of 93 cases (76%) by viral PCR and bacterial culture. Respiratory viruses were detected in NPA of 84 cases (69%) and MEF of 67 cases (55%). The most common virus detected in MEF was respiratory syncytial virus (21%), followed by parainfluenza virus (15%). All the viruses present in MEF were also detected in NPA specimens. Bacteria were detected by PCR in MEF of 109 cases (89%); H. influenzae was the most frequently detected (65%).

CONCLUSIONS

In many cases, pediatric AOM was found to constitute a respiratory polymicrobial infection. Multiplex PCR was useful to detect multiple respiratory viruses and bacteria in AOM. To understand intractable AOM, further studies regarding the clinical features of each viral and bacterial coinfection are required.

Subversion of host immune responses by otopathogens during otitis media

Otitis media (OM) is one of the most common ear diseases affecting humans. Children are at greater risk and suffer most frequently from OM, which can cause serious deterioration in the quality of life. OM is generally classified into two main types: acute and chronic OM (AOM and COM). AOM is characterized by tympanic membrane swelling or otorrhea and is accompanied by signs or symptoms of ear infection. In COM, there is a tympanic membrane perforation and purulent discharge. The most common pathogens that cause AOM are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis whereas Pseudomonas aeruginosa and Staphylococcus aureus are commonly associated with COM. Innate and adaptive immune responses provide protection against OM. However, pathogens employ a wide arsenal of weapons to evade potent immune responses and these mechanisms likely contribute to AOM and COM. Immunologic evasion is multifactorial, and involves damage to host mucociliary tract, genetic polymorphisms within otopathogens, the number and variety of different otopathogens in the nasopharynx as well as the interaction between the host's innate and adaptive immune responses. Otopathogens utilize host mucin production, phase variation, biofilm production, glycans, as well as neutrophil and eosinophilic extracellular traps to induce OM. The objective of this review article is to discuss our current understanding about the mechanisms through which otopathogens escape host immunity to induce OM. A better knowledge about the molecular mechanisms leading to subversion of host immune responses will provide novel clues to develop effective treatment modalities for OM.

Characteristics of children with refractory acute otitis media treated at the pediatric emergency department

INTRODUCTION

Refractory acute otitis media (rAOM) is defined as the persistence of signs and symptoms of AOM for more than 48 to 72 hours after the initiation of antibiotic treatment. These patients are often referred to the pediatric emergency department (PED). We sought to study rAOM cases referred to our PED, and to evaluate their clinical characteristics and response to our local management guidelines.

METHODS

A retrospective chart review of all children treated for rAOM between 1/2012-3/2014 was performed. Data recorded included demographics, clinical presentation, antibiotic treatments, need for surgery, and culture results.

RESULTS

A total of 255 patients were included with a mean age of 19 months. Prior to admission, all the children had received at least one course of antibiotics. Amoxicillin was the most common first-line antibiotic prescribed while amoxicillin-clavulanic acid was the most common second and third-line antibiotic given. Intravenous ceftriaxone was the treatment administered at the PED. Myringotomy and pressure equalizing tube (PET) insertion were required in 60% of cases. Middle ear cultures (55 ears) were positive for Streptococcus pneumoniae in two, and Moraxella catarrhalis in only one culture. There were no differences between the mean age of children who had PET insertion and those who did not with regards to fever, rhinorrhea, and preschool or school attendance. Children presenting with otorrhea were less likely to undergo surgery (P = 0.013).

CONCLUSIONS

This is the first study evaluating the established local practice guideline with regards to clinical characteristics and need for surgical management. We showed that myringotomy and PET insertion due to antibiotic failure is commonly performed for cases of rAOM. The majority of the middle ear cultures were sterile.

High-dose versus standard-dose amoxicillin/clavulanate for clinically-diagnosed acute bacterial sinusitis: A randomized clinical trial

Background

The recommended treatment for acute bacterial sinusitis in adults, amoxicillin with clavulanate, provides only modest benefit.

Objective

To see if a higher dose of amoxicillin will lead to more rapid improvement.

Design, setting, and participants

Double-blind randomized trial in which, from November 2014 through February 2017, we enrolled 315 adult outpatients diagnosed with acute sinusitis in accordance with Infectious Disease Society of America guidelines.

Interventions

Standard-dose (SD) immediate-release (IR) amoxicillin/clavulanate 875 /125 mg (n = 159) vs. high-dose (HD) (n = 156). The original HD formulation, 2000 mg of extended-release (ER) amoxicillin with 125 mg of IR clavulanate twice a day, became unavailable half way through the study. The IRB then approved a revised protocol after patient 180 to provide 1750 mg of IR amoxicillin twice a day in the HD formulation and to compare Time Period 1 (ER) with Time Period 2 (IR).

Main measure

The primary outcome was the percentage in each group reporting a major improvement—defined as a global assessment of sinusitis symptoms as “a lot better” or “no symptoms”—after 3 days of treatment.

Key results

Major improvement after 3 days was reported during Period 1 by 38.8% of ER HD versus 37.9% of SD patients (P = 0.91) and during Period 2 by 52.4% of IR HD versus 34.4% of SD patients, an effect size of 18% (95% CI 0.75 to 35%, P = 0.04). No significant differences in efficacy were seen at Day 10. The major side effect, severe diarrhea at Day 3, was reported during Period 1 by 7.4% of HD and 5.7% of SD patients (P = 0.66) and during Period 2 by 15.8% of HD and 4.8% of SD patients (P = 0.048).

Conclusions

Adults with clinically diagnosed acute bacterial sinusitis were more likely to improve rapidly when treated with IR HD than with SD but not when treated with ER HD. They were also more likely to suffer severe diarrhea. Further study is needed to confirm these findings.

Trial registration

ClinicalTrials.gov Identifier: NCT02340000.

Did the accuracy of oral amoxicillin dosing of children improve after British National Formulary dose revisions in 2014? National cross-sectional survey in England

OBJECTIVES

Inaccurate antibiotic dosing can lead to treatment failure, fuel antimicrobial resistance and increase side effects. The British National Formulary for Children (BNFC) guidance recommends oral antibiotic dosing according to age bands as a proxy for weight. Recommended doses of amoxicillin for children were increased in 2014 'after widespread concerns of under dosing'. However, the impact of dose changes on British children of different weights is unknown, particularly given the rising prevalence of childhood obesity in the UK. We aimed to estimate the accuracy of oral amoxicillin dosing in British children before and after the revised BNFC guidance in 2014.

SETTING AND PARTICIPANTS

We used data on age and weights for 1556 British children (aged 2-18 years) from a nationally representative cross-sectional survey, the Health Survey for England 2013.

INTERVENTIONS

We calculated the doses each child would receive using the BNFC age band guidance, before and after the 2014 changes, against the 'gold standard' weight-based dose of amoxicillin, as per its summary of product characteristics.

PRIMARY OUTCOME MEASURE

Assuming children of different weights were equally likely to receive antibiotics, we calculated the percentage of the children who would be at risk of misdosing by the BNFC age bands.

RESULTS

Before 2014, 54.6% of children receiving oral amoxicillin would have been underdosed and no child would have received more than the recommended dose. After the BNFC guidance changed in 2014, the number of children estimated as underdosed dropped to 5.8%, but 0.5% of the children would have received too high a dose.

CONCLUSIONS

Changes to the BNFC age-banded amoxicillin doses in 2014 have significantly reduced the proportion of children who are likely to be underdosed, with only a minimal rise in the number of those above the recommended range.

Controversies in the Medical Management of Persistent and Recurrent Acute Otitis Media Recommendations of a Clinical Advisory Committee

Streptococcus pneumoniae is the predominant bacterial pathogen associated with acute otitis media (AOM), causing an estimated 7 million cases annually in the United States. Bacterial resistance should be considered when selecting an antimicrobial agent for otitis media. Significant increases in drug-resistant S pneumoniae are documented worldwide, and less than 50% of S pneumoniae strains are fully susceptible to penicillin in some regions of the United States. Although amoxicillin is recommended for uncomplicated AOM, treatment guidelines should be flexible and adaptable, taking into consideration local and regional susceptibility patterns, the age of the patient, the frequency of prior infections, and the response to prior therapy. Resistant organisms are more prevalent in children younger than 2 years of age and in those who have recurrent or persistent AOM. Overdiagnosing AOM, selecting inappropriate empiric therapy, or both, leads to overuse and misuse of antibiotics and causes increased drug resistance. This article reviews persistent and recurrent AOM and discusses the pitfalls of diagnosis and the practical limitations of current treatment recommendations.

Otitis media

Otitis media (OM) or middle ear inflammation is a spectrum of diseases, including acute otitis media (AOM), otitis media with effusion (OME; 'glue ear') and chronic suppurative otitis media (CSOM). OM is among the most common diseases in young children worldwide. Although OM may resolve spontaneously without complications, it can be associated with hearing loss and life-long sequelae. In developing countries, CSOM is a leading cause of hearing loss. OM can be of bacterial or viral origin; during 'colds', viruses can ascend through the Eustachian tube to the middle ear and pave the way for bacterial otopathogens that reside in the nasopharynx. Diagnosis depends on typical signs and symptoms, such as acute ear pain and bulging of the tympanic membrane (eardrum) for AOM and hearing loss for OME; diagnostic modalities include (pneumatic) otoscopy, tympanometry and audiometry. Symptomatic management of ear pain and fever is the mainstay of AOM treatment, reserving antibiotics for children with severe, persistent or recurrent infections. Management of OME largely consists of watchful waiting, with ventilation (tympanostomy) tubes primarily for children with chronic effusions and hearing loss, developmental delays or learning difficulties. The role of hearing aids to alleviate symptoms of hearing loss in the management of OME needs further study. Insertion of ventilation tubes and adenoidectomy are common operations for recurrent AOM to prevent recurrences, but their effectiveness is still debated. Despite reports of a decline in the incidence of OM over the past decade, attributed to the implementation of clinical guidelines that promote accurate diagnosis and judicious use of antibiotics and to pneumococcal conjugate vaccination, OM continues to be a leading cause for medical consultation, antibiotic prescription and surgery in high-income countries.

Middle Ear and Eustachian Tube Mucosal Immunology

Mucosal immune responses within the middle ear and eustachian tube generally provide an effective and efficient response to the presence of microbial pathogens, with approximately 80% of clinically recognizable middle ear infections resolved within 7 days. Particularly for young children aged less than 3 years of age, the proximity and direct connection of the middle ear, via the eustachian tube, to the nasopharynx provide increased risk of commensal bacteria and upper respiratory tract viruses infecting the middle ear. Mucosal immunological defense in the middle ear and eustachian tube utilizes a number of mechanisms, including physicochemical barriers of mucus and the mucosal epithelial cells and innate immune responses such as inflammation, cellular infiltration, effusion, and antimicrobial protein secretions, in addition to adaptive host immune responses. Recent advances in otopathogen recognition via microbial pattern recognition receptors and elucidation of complex signaling cascades have improved understanding of the coordination and regulation of the middle ear mucosal response. These advances support vaccine development aiming to reduce the risk of otitis media in children.

Concentration of amoxicillin in maternal serum, cord blood, amniotic fluid and the placenta after vaginal administration

OBJECTIVE

The aim of this study was to assess the amoxicillin concentration in maternal serum, cord blood, amniotic fluid and the placenta, 2 h following vaginal administration and the factors influencing the drug level.

METHODS

Twenty-eight full-term pregnant women who qualified for elective cesarean delivery were included in the study. Vaginal suppositories containing 250 mg of amoxicillin were administered 2 h prior to the operation. Amoxicillin levels were determined using the diffusion microbial assay.

RESULTS

The amoxicillin level in amniotic fluid was significantly higher in comparison to that of maternal serum, cord blood or the placenta. Maternal age positively and gestational weight gain negatively correlated with the amoxicillin concentration in maternal serum. The maternal serum hemoglobin level and red blood cell count were positively correlated with amoxicillin concentration in the amniotic fluid. Neonatal birth weight was positively correlated with maternal serum and cord blood amoxicillin levels. Hypertensive women had significantly higher amoxicillin concentrations in amniotic fluid, and women with thrombocytopenia presented significantly higher cord blood amoxicillin concentrations.

CONCLUSIONS

Amoxicillin presented poor concentration in maternal-fetal compartments after vaginal administration, but the factors influencing the drug level in different compartments require further investigation.

Beta- lactam antibiotics stimulate biofilm formation in non-typeable haemophilus influenzae by up-regulating carbohydrate metabolism

Non-typeable Haemophilus influenzae (NTHi) is a common acute otitis media pathogen, with an incidence that is increased by previous antibiotic treatment. NTHi is also an emerging causative agent of other chronic infections in humans, some linked to morbidity, and all of which impose substantial treatment costs. In this study we explore the possibility that antibiotic exposure may stimulate biofilm formation by NTHi bacteria. We discovered that sub-inhibitory concentrations of beta-lactam antibiotic (i.e., amounts that partially inhibit bacterial growth) stimulated the biofilm-forming ability of NTHi strains, an effect that was strain and antibiotic dependent. When exposed to sub-inhibitory concentrations of beta-lactam antibiotics NTHi strains produced tightly packed biofilms with decreased numbers of culturable bacteria but increased biomass. The ratio of protein per unit weight of biofilm decreased as a result of antibiotic exposure. Antibiotic-stimulated biofilms had altered ultrastructure, and genes involved in glycogen production and transporter function were up regulated in response to antibiotic exposure. Down-regulated genes were linked to multiple metabolic processes but not those involved in stress response. Antibiotic-stimulated biofilm bacteria were more resistant to a lethal dose (10 µg/mL) of cefuroxime. Our results suggest that beta-lactam antibiotic exposure may act as a signaling molecule that promotes transformation into the biofilm phenotype. Loss of viable bacteria, increase in biofilm biomass and decreased protein production coupled with a concomitant up-regulation of genes involved with glycogen production might result in a biofilm of sessile, metabolically inactive bacteria sustained by stored glycogen. These biofilms may protect surviving bacteria from subsequent antibiotic challenges, and act as a reservoir of viable bacteria once antibiotic exposure has ended.

Dose optimisation of antibiotics in children: application of pharmacokinetics/pharmacodynamics in paediatrics

The judicious use of antibiotics to combat infections in children relies upon appropriate selection of an agent, dose and duration to maximise efficacy and to minimise toxicity. Critical to dose optimisation is an understanding of the pharmacokinetics and pharmacodynamics of available drugs. Optimal dosing strategies may take advantage of pharmacokinetic/pharmacodynamic (PK/PD) principles so that antibiotic dosing can be individualised to assure effective bacterial killing in patients who have altered pharmacokinetics or who have infections with less susceptible or resistant organisms. This review will outline the fundamentals of antimicrobial pharmacokinetics/pharmacodynamics through discussion of antibacterial agents most often used in children. We aim to highlight the importance of dose optimisation in paediatrics and describe non-conventional dosing strategies that can take advantage of PK/PD principles at the bedside.

Evaluation of Antimicrobial Treatments in Children with Acute Otitis Media in Spain: A Pharmacokinetic-Pharmacodynamic (PK/PD) Approach

Pharmacokinetic/pharmacodynamic (PK/PD) principles are priceless tools for evaluating the effectiveness of different antimicrobial treatments for different infections. However, very few studies deal with pediatric dosages and take into account the unbound drug serum levels. Our study is focused on the most frequent antibiotic dosing schedules used in Spain for the treatment of acute otitis media (AOM) in children, where high rates of penicillin and macrolide resistance exist among pneumococcal isolates. Pharmacokinetic parameters of antibiotics in children where obtained from the literature. The minimum inhibitory concentrations (MIC90) of antibiotics for pediatric strains of Streptococcus pneumoniae and Haemophilus influenzae were obtained from the SAUCE 2 project. Only ceftriaxone (50 mg/kg single intramuscular dose) and high doses of co-amoxiclav (27-33 mg/kg q8h) provided adequate efficacy indexes (tss(%)>MIC) for both S. pneumoniae and H. influenzae in AOM in children. These results are consistent with MEF (medium ear fluid) levels obtained from the literature. Our results confirm the utility of serum unbound levels to predict efficacy of antibiotics in children with AOM.

Viral-bacterial interactions in acute otitis media

Acute otitis media (AOM) is a polymicrobial disease, which usually occurs as a complication of viral upper respiratory tract infection (URI). While respiratory viruses alone may cause viral AOM, they increase the risk of bacterial middle ear infection and worsen clinical outcomes of bacterial AOM. URI viruses alter Eustachian tube (ET) function via decreased mucociliary action, altered mucus secretion and increased expression of inflammatory mediators among other mechanisms. Transient reduction in protective functions of the ET allows colonizing bacteria of the nasopharynx to ascend into the middle ear and cause AOM. Advances in research help us to better understand the host responses to viral URI, the mechanisms of viral-bacterial interactions in the nasopharynx and the development of AOM. In this review, we present current knowledge regarding viral-bacterial interactions in the pathogenesis and clinical course of AOM. We focus on the common respiratory viruses and their established role in AOM.

Otitis media

Otitis media represents a broad spectrum of disease, which include acute otitis media and otitis media with effusion. As immunization with the pneumococcal conjugate vaccine has become more widespread, the microbiological landscape of otitis media has changed, which affects the treatment options facing clinicians worldwide. This review discusses the diagnosis and medical management of acute and chronic suppurative otitis media, the changes noted over the past decade, and briefly expounds on the surgical management of their severe complications.

Presence of viral nucleic acids in the middle ear: acute otitis media pathogen or bystander?

Viruses play an important role in acute otitis media (AOM) pathogenesis, and live viruses may cause AOM in the absence of pathogenic bacteria. Detection of AOM pathogens generally relies on bacterial culture of middle ear fluid. When viral culture is used and live viruses are detected in the middle ear fluid of children with AOM, the viruses are generally accepted as AOM pathogens. Because viral culture is not sensitive and does not detect the comprehensive spectrum of respiratory viruses, polymerase chain reaction assays are commonly used to detect viral nucleic acids in the middle ear fluid. Although polymerase chain reaction assays have greatly increased the viral detection rate, new questions arise on the significance of viral nucleic acids detected in the middle ear because nucleic acids of multiple viruses are detected simultaneously, and nucleic acids of specific viruses are detected repeatedly and in a high proportion of asymptomatic children. This article first reviews the role of live viruses in AOM and presents the point-counterpoint arguments on whether viral nucleic acids in the middle ear represent an AOM pathogen or a bystander status. Although there is evidence to support both directions, helpful information for interpretation of the data and future research direction is outlined.

Pharmacokinetic/pharmacodynamic evaluation of amoxicillin, amoxicillin/clavulanate and ceftriaxone in the treatment of paediatric acute otitis media in Spain

INTRODUCTION

Acute otitis media is the most common respiratory tract infection in infancy and early childhood that is managed with antimicrobial agents. Ninety-three per cent of the cases diagnosed in Spain are treated with antibiotics, and Streptococcus pneumoniae and untypeable Haemophilus influenzae are the most frequently isolated pathogens. The aim of this work was to evaluate the usefulness of amoxicillin, amoxicillin/clavulanate and ceftriaxone for the empirical treatment of acute otitis media, looking at the pharmacokinetic variability and the antimicrobial susceptibility of paediatric strains of the two main pathogens responsible for AOM in Spain, Streptococcus pneumoniae and Haemophilus influenzae.

METHODS

Free-drug plasma concentrations were simulated and the probability of target attainment at each minimum inhibitory concentration and the cumulative fraction of response (CFR) were determined. Microbiological susceptibility information was extracted from SAUCE 3 surveillance.

RESULTS

CFR with amoxicillin varied from 83% to 96% against S. pneumoniae and from 78% to 86% against H. influenzae. CFR was always >85% with amoxicillin/clavulanate. With the 3-day ceftriaxone regimen, the probability of achieving free concentrations above MIC at 72 hours significantly increased compared to the single dose, with which CFR ranged from 70% to 84%.

CONCLUSIONS

High-dose amoxicillin (at least 80 mg/kg/day) should be the first-line therapy in uncomplicated infections, whereas amoxicillin/clavulanate (40 mg/kg/day) should be the choice when additional coverage for H. influenzae is desired. Administration of 3 daily doses of ceftriaxone increases bacteriological eradication probability when compared with one-day regimen, although additional clinical evaluations are necessary to establish the best target attainment with ceftriaxone.

Immunopathogenesis of polymicrobial otitis media

OM, or inflammation of the middle ear, is a highly prevalent infection in children worldwide. OM is a multifactorial disease with multiple risk factors, including preceding or concurrent viral URT infection. Hence, OM is also a polymicrobial disease. The mechanisms by which viruses predispose to bacterial OM are replete; however, all are predicated on the general principle of compromise of primary host airway defenses. Thus, despite an as-yet incomplete understanding of the molecular mechanisms involved in bacterial superinfection of a virus-compromised respiratory tract, the URT viruses are known to induce histopathology of airway mucosal epithelium, up-regulate expression of eukaryotic receptors used for bacterial adherence, alter the biochemical and rheological properties of airway mucus, and affect innate and acquired host immune functions, among others. Although discussed here in the context of OM, during preceding or concurrent viral infection of the human respiratory tract, viral impairment of airway defenses and the resulting predisposition to subsequent bacterial coinfection are also known to be operational in the mid and lower airway as well.

Clinical and microbiological impact of human bocavirus on children with acute otitis media

Human Bocavirus (HBoV) as a newly discovered parvovirus has been commonly detected in respiratory tract infections. However, its role in acute otitis media (AOM) has not been well studied. We examined HBoV in Japanese children with AOM and evaluated the virus prevalence together with clinical manifestations and bacterial findings. Overall, 222 nasopharyngeal swabs and 176 middle ear fluids (MEF) samples were collected from 222 children with AOM (median age, 19 months) between May 2006 and April 2007. HBoV detection was performed by PCR and bacterial isolation by standard culture methods. HBoV was found in the nasopharyngeal aspirates of 14 children (6.3%) and in the MEF of six children (2.7%). When HBoV detection results were evaluated with clinical characteristics of children, resolution time of AOM was significantly longer (p=0.04), and rate of fever symptom was also higher in HBoV-positive group (p=0.04). Furthermore, we found positive correlation between detection of HBoV and Streptococcus pneumoniae in the MEF (p=0.004). Nevertheless, nasopharyngeal proportion of S. pneumoniae was similar between virus positive and negative groups. Furthermore, S. pneumoniae was detected as a single pathogen in all MEF of HBoV-positive cases but one, while it presents mixed with other pathogenic bacteria in nasopharynx. In conclusion, HBoV may worsen the clinical symptoms and prolong the clinical outcome of AOM in pediatric population. Finally, HBoV may prime the secondary bacterial infection in the middle ear in favor of S. pneumoniae.

Variations in amoxicillin pharmacokinetic/pharmacodynamic parameters may explain treatment failures in acute otitis media

Pharmacokinetic/pharmacodynamic (PK/PD) modeling and Monte Carlo simulations suggest that amoxicillin should rarely fail as therapy for Streptococcus pneumoniae and Haemophilus influenzae acute otitis media (AOM) infections except when the S. pneumoniae are highly penicillin resistant or the H. influenzae are beta-lactamase producing. However, important and not infrequent exceptions to this expectation have been described. The objective of this review was to define the biologic variations in amoxicillin PK/PD parameters for the treatment of AOM in children and assess whether these variations could explain why the commonly employed amoxicillin PK/PD model is imperfect in predicting outcome for every patient in this clinical setting. To this end, a literature search of MEDLINE (1966-2006) and EMBASE (1974-2006) was conducted to identify studies that evaluated ampicillin or amoxicillin intestinal absorption, serum concentrations, and/or middle ear fluid (MEF) concentrations. Analysis of studies identified for review showed that the intestinal bioavailability of amoxicillin depends on passive diffusion and a saturable 'pump' mechanism that produces variable serum concentrations of the antibacterial agent. Indeed, substantial differences from patient to patient in serum (5- to 30-fold) and MEF (up to 20-fold) concentrations of amoxicillin occur following oral administration, and 15-35% of children have no detectable amoxicillin in MEF. These findings suggest that variability in PK/PD parameters may impact amoxicillin concentrations in serum and MEF, possibly explaining some AOM treatment failures.

Laterality of acute otitis media: different clinical and microbiologic characteristics

BACKGROUND

A large individual patient data meta-analysis recently showed that children aged less than 2 years with bilateral, as compared with unilateral, acute otitis media (AOM) were at higher risk for persistent symptoms without antibiotic treatment. Prior studies have shown a propensity for children with bilateral AOM to be infected with bacterial pathogens, specifically Haemophilus influenzae. The objectives of this study were to further characterize risk factors for bilateral AOM and to assess the propensity for specific viral and bacterial pathogens to predispose to bilateral versus unilateral AOM.

METHODS

We performed a secondary data analysis on 1216 cases of AOM diagnosed and treated at our institution: 566 subjects underwent tympanocentesis and middle ear fluid (MEF) culture. We compared subjects with bilateral and unilateral AOM for demographic characteristics, clinical findings, parent/clinician perception of AOM severity, and MEF study results for bacteria and viruses.

RESULTS

When compared with children who have unilateral AOM, children with bilateral AOM were more likely to be younger (P < 0.001), have H. influenzae isolated from one or both MEFs (P < 0.0001), and have more severe inflammation of the tympanic membrane on otoscopic examination (P < 0.0001).

CONCLUSION

Compared with children who have unilateral AOM, children with bilateral AOM are more likely to have bacteria in the MEF and have more severe inflammation of the tympanic membrane. This may help explain why children with bilateral AOM are more likely to experience persistent symptoms without antibiotic treatment. Laterality of AOM should be considered when discussing treatment options with parents.

Role of respiratory syncytial virus in acute otitis media: implications for vaccine development

We summarize herein the results of various virologic studies of acute otitis media (AOM) conducted at our site over a 10-year period. Among 566 children with AOM, respiratory syncytial virus (RSV) was the most common virus identified in either middle ear fluid or nasal wash; it was found in 16% of all children and 38% of virus-positive children. Seventy-one percent of the children with RSV were 1 year of age or older, which was significantly older than all other viruses combined (P=0.045). RSV infection was associated with the common bacterial pathogens causing AOM. Past efforts to develop vaccines for RSV have emphasized prevention of lower respiratory tract infection in infants, which is a more serious problem but less common than AOM. Our results suggest that RSV vaccines that work only against infection in older children may have value in preventing AOM, the most common pediatric disease.

What is new in otitis media?

The "wait and see" approach in acute otitis media (AOM), consisting of postponing the antibiotic administration for a few days, has been advocated mainly to counteract the increased bacterial resistance in respiratory infections. This approach is not justified in children less than 2 years of age and this for several reasons. First, AOM is an acute inflammation of the middle ear caused in about 70% of cases by bacteria. Redness and bulging of the tympanic membrane are characteristic findings in bacterial AOM. Second, AOM is associated with long-term dysfunction of the inflamed eustachian tube (ET), particularly in children less than 2 years of age. In this age group, the small calibre of the ET together with its horizontal direction result in impaired clearance, ventilation and protection of the middle ear. Third, recent prospective studies have shown poor long-term prognosis of AOM in children below 2 years with at least 50% of recurrences and persisting otitis media with effusion (OME) in about 35% 6 months after AOM. Viruses elicit AOM in about 30% of children. A prolonged course of AOM has been observed when bacterial and viral infections are combined because viral infection is also associated with ET dysfunction in young children. Bacterial and viral testing of the nasopharyngeal aspirate is an excellent tool both for initial treatment and recurrence of AOM. Antibiotic treatment of AOM is mandatory in children less than 2 years of age to decrease inflammation in the middle ear but also of the ET particularly during the first episode. The best choice is amoxicillin because of its superior penetration in the middle ear. Streptococci pneumoniae with intermediary bacterial resistance to penicillin are particularly associated with recurrent AOM. Therefore the dosage of amoxicillin should be 90 mg/kg per day in three doses. In recurrent AOM with beta-lactamase-producing bacilli, amoxicillin should be associated with clavulanic acid at a dose of 6.4 mg/kg per day. The duration of the treatment is not established yet but 10 days is reasonable for a first episode of AOM. OME may be a precursor initiating AOM but also a complication thereof. OME needs a watchful waiting approach. When associated with deafness for 2-3 months in children over 2 years of age, an antibiotic should be given according to the results of the bacterial resistance in the nasopharyngeal aspirate. The high rate of complications of tympanostomy tube insertion outweighs the beneficial effect on hearing loss. The poor results of this procedure are due to the absence of effects on ET dysfunction. Pneumococcal vaccination has little beneficial effects on recurrent AOM and its use in infants needs further studies. Treatment with amoxicillin is indicated in all children younger than 2 years with a first episode of AOM presenting with redness and bulging of the tympanic membrane. Combined amoxicillin and clavulanic acid should be given in patients with beta-lactamase-producing bacteria. The duration of treatment is estimated to be at least 10 days depending on the findings by pneumo-otoscopy and tympanometry. Bacterial and viral testing of the nasopharyngeal aspirate is highly recommended particularly in children in day care centres as well as for regular follow-up. The high recurrence rate is due to the long-lasting dysfunction of the eustachian tube and the immune immaturity of children less than 2 years of age.

Searching for the Holy Grail of acute otitis media

Use of PCV7 causes a major shift in the microbiology of AOM towards H influenzae, but the search for the Holy Grail of AOM still remains elusive

Microbiology of acute otitis media in children with tympanostomy tubes: prevalences of bacteria and viruses

Background. Bacteria are found in 50%–90% of cases of acute otitis media (AOM) with or without otorrhea, and viruses are found in 20%–49% of cases. However, for at least 15% of patients with AOM, the microbiological etiology is never determined. Our aim was to specify the full etiology of acute middle ear infection by using modern microbiological methods concomitantly for bacterial and viral detection.

Methods. The subjects were 79 young children having AOM with new onset (<48 h) of otorrhea through a tympanostomy tube. Middle ear fluid samples were suctioned from the middle ear through the tympanostomy tube. Bacteria were sought by culture and polymerase chain reaction; viruses were analyzed by culture, antigen detection, and polymerase chain reaction.

Results. At least 1 respiratory tract pathogen was noted in 76 children (96%). Bacteria were found in 73 cases (92%), and viruses were found in 55 (70%). In 52 patients (66%), both bacteria and viruses were found. Bacteria typical of AOM were detected in 86% of patients. Picornaviruses accounted for 60% of all viral findings.

Conclusions. In the great majority of children, AOM is a coinfection with bacteria and viruses. The patent tympanostomy tube does not change the spectrum of causative agents in AOM. A microbiological etiology can be established in practically all cases.

Viral upper respiratory tract infections in young children with emphasis on acute otitis media

Viral upper respiratory infection is the most common reason for seeking medical care for children. Recurrent viral respiratory infections and subsequent complications (e.g. acute otitis media (AOM)) are a burden for children, their families and society. Over the past decade, our knowledge on the significance of respiratory viruses has broadened remarkably. Viruses cause large variety of respiratory diseases and cause alone diseases, which previously have been assumed to be bacterial only (e.g. AOM and pneumonia). Methods for detection analysis of respiratory viruses are developing making both the diagnosis and epidemiological investigations of respiratory infections easier. Accurate diagnosis of respiratory infections and awareness of possible viral etiology could reduce the use of antibiotics. Etiologic studies of viral infections are becoming increasingly important, with the emergence of new antiviral drugs and vaccines.

New formulations of amoxicillin/clavulanic acid: a pharmacokinetic and pharmacodynamic review

The pharmacokinetic properties of amoxicillin and clavulanic acid when used alone or in combination are extensively reviewed and discussed in this article. The reported data support a nonlinear absorption process for amoxicillin. Saturable transport mechanisms, limited solubility and the existence of an absorption window are possibly involved in the gastrointestinal absorption of this antibacterial, all leading to a decrease in the peak plasma concentration (Cmax)/dose ratio, a prolongation of the time to reach Cmax, and broad variability for high doses of amoxicillin. Data available in the literature also suggest a possible interaction between amoxicillin and clavulanic acid that might decrease the absolute bioavailability of clavulanic acid. In the present review the intrinsic pharmacodynamics of each drug, together with the synergism produced by the amoxicillin/clavulanic acid association, are also reviewed and analysed. Not only beta-lactamase-producing strains, but also Streptococcus pneumoniae strains, seem to be more efficiently eradicated by the association of amoxicillin and clavulanic acid, and a relevant post-antibacterial effect and post-beta-lactamase inhibitor effect are likely to operate when amoxicillin is administered together with clavulanic acid. The principles of pharmacokinetic/pharmacodynamic analysis applied to amoxicillin are reviewed, with special emphasis being placed on the results obtained from in vitro studies and animal models regarding the new pharmacokinetically enhanced formulation. Theoretical considerations concerning the efficacy of this formulation provided by the application of pharmacokinetic/pharmacodynamic analysis to the scarce pharmacokinetic data available are also included. The broad pharmacokinetic variability of both amoxicillin and clavulanic acid, particularly when administered together and at high doses of amoxicillin, is highlighted and the interest in considering this aspect to improve predictions based on pharmacokinetic/pharmacodynamic analyses for the new formulations is indicated. Methodological recommendations such as the Monte Carlo simulation are proposed in order to obtain more realistic predictions in clinical practice.

Nonsevere acute otitis media: a clinical trial comparing outcomes of watchful waiting versus immediate antibiotic treatment

OBJECTIVE

The widespread use of antibiotics for treatment of acute otitis media (AOM) has resulted in the emergence of multidrug-resistant pathogens that are difficult to treat. However, it has been shown that most children with nonsevere AOM recover without ABX. The objective of this study was to evaluate the safety, efficacy, acceptability, and costs of a non-ABX intervention for children with nonsevere AOM.

METHODOLOGY

Children 6 months to 12 years old with AOM were screened by using a novel AOM-severity screening index. Parents of children with nonsevere AOM received an educational intervention, and their children were randomized to receive either immediate antibiotics (ABX; amoxicillin plus symptom medication) or watchful waiting (WW; symptom medication only). The investigators, but not the parents, were blinded to enrollment status. Primary outcomes included parent satisfaction with AOM care, resolution of symptoms, AOM failure/recurrence, and nasopharyngeal carriage of Streptococcus pneumoniae strains resistant to ABX. Secondary outcomes included medication-related adverse events, serious adverse events, unanticipated AOM-related office and emergency department visits and telephone calls, the child's absence from day care or school resulting from AOM, the parent's absence from school or work because of their child's AOM, and costs of treatment. Subjects were defined as failing (days 0-12) or recurring (days 13-30) if they experienced a higher AOM-severity score on reexamination.

RESULTS

A total of 223 subjects were recruited: 73% were nonwhite, 57% were <2 years old, 47% attended day care, 82% had experienced prior AOM, and 83% had not been fully immunized with heptavalent pneumococcal vaccine. One hundred twelve were randomized to ABX, and 111 were randomized to WW. Ninety-four percent of the subjects were followed to the 30-day end point. Parent satisfaction with AOM care was not different between the 2 treatment groups at either day 12 or 30. Compared with WW, symptom scores on days 1 to 10 resolved faster in subjects treated with immediate ABX. At day 12, among the immediate-ABX group, 69% of tympanic membranes and 25% of tympanograms were normal, compared with 51% of normal tympanic membranes and 10% of normal tympanograms in the WW group. Parents of children in the ABX group gave their children fewer doses of pain medication than did parents of children in the WW group. Subjects in the ABX group experienced 16% fewer failures than subjects in the WW group. Of the children in the WW group, 66% completed the study without needing ABX. Immediate ABX resulted in eradication of S pneumoniae carriage in the majority of children, but S pneumoniae strains cultured from children in the ABX group at day 12 were more likely to be multidrug-resistant than strains from children in the WW group. More ABX-related adverse events were noted in the ABX group, compared with the WW group. No serious AOM-related adverse events were observed in either group. Office and emergency department visits, phone calls, and days of work/school missed were not different between groups. Prescriptions for ABX were reduced by 73% in the WW group compared with the ABX group. Costs of ABX averaged $47.41 per subject in the ABX group and $11.43 in the WW group.

CONCLUSIONS

Sixty-six percent of subjects in the WW group completed the study without ABX. Parent satisfaction was the same between groups regardless of treatment. Compared with WW, immediate ABX treatment was associated with decreased numbers of treatment failures and improved symptom control but increased ABX-related adverse events and a higher percent carriage of multidrug-resistant S pneumoniae strains in the nasopharynx at the day-12 visit. Key factors in implementing a WW strategy were (a) a method to classify AOM severity; (b) parent education; (c) management of AOM symptoms; (d) access to follow-up care; and (e) use of an effective ABX regimen, when needed. When these caveats are observed, WW may be an acceptable alternative to immediate ABX for some children with nonsevere AOM.

Application of pharmacokinetics and pharmacodynamics to antimicrobial therapy of respiratory tract infections

The pharmacologic field that studies antimicrobial pharmacokinetics and pharmacodynamics (PK/PD) has had a major impact on the choice and dosing regimens used for many antibiotics especially those used in the treatment of respiratory tract infections. PK/PD parameters are particularly important in light of increasing antimicrobial resistance. Drug pharmacokinetic features, such as serum concentrations over time and area under the concentration-time curve, when integrated with minimum inhibitory concentration (MIC) values of antibiotics against pathogens, can predict the probability of bacterial eradication and clinical success. These pharmacokinetic and pharmacodynamic relationships also are important in preventing the selection and spread of resistant strains and have led to the description of the mutation prevention concentration, which is the lowest concentration of antimicrobial that prevents selection of resistant bacteria from high bacterial inocula. b-lactams are time-dependent agents without significant post-antibiotic effects, resulting in bacterial eradication when unbound serum concentrations exceed MICs of these agents against infecting pathogens for >40% to 50% of the dosing interval. Macrolides, azaolides, and lincosamides are time-dependent agents with prolonged post-antibiotic effects, and fluoroquinolones are concentration-dependent agents, resulting in both cases in bacterial eradication when unbound serum area-under-the-curve to MIC ratios exceed 25 to 30. These observations have led to changes in recommended antimicrobial dosing against respiratory pathogens and are used to assess the role of current agents, develop new formulations, and assess potency of new antimicrobials.

High-Dose Versus Standard-Dose Amoxicillin for Acute Otitis Media

BACKGROUND:

Emergence of drug-resistant bacteria has led to a recommendation to use high-dose (HD) amoxicillin (80–90 mg/kg/d) rather than standard-dose (SD) amoxicillin (40–45 mg/kg/d) to treat children with acute otitis media (AOM).

OBJECTIVE:

To compare the efficacy and tolerability of HD versus SD amoxicillin among children with AOM who were considered at low risk for infection with antibiotic-resistant bacteria.

METHODS:

A double-blind, randomized, 3-year clinical trial was conducted using participants who met the following criteria: age >3 mo, weight ≤18 kg, diagnosed with AOM, and candidates for treatment with amoxicillin. The primary endpoint was treatment success at a 3- to 4-day follow-up visit based on the clinical decision to continue the prescribed antibiotic therapy for AOM. Other endpoints included duration of illness, number of office visits and telephone calls related to illness, total number of subsequent AOM episodes, and number of adverse effects.

RESULTS:

The absolute difference in antibiotic failure rate with SD versus HD amoxicillin at the follow-up visit was nonsignificant (95% CI–1.5% to 3.4%; p = 0.78). The mean duration of illness was similar for both doses of amoxicillin (3 ± 2 d). The number of office visits and telephone calls related to illness and the number of subsequent AOM episodes did not differ between the 2 treatment groups. HD amoxicillin did not result in a greater incidence of adverse effects than SD amoxicillin.

CONCLUSIONS:

HD amoxicillin had neither benefit nor detriment compared with SD for AOM in children at low risk for infection with antibiotic-resistant bacteria.

Does acetaminophen interfere in the antibiotic treatment of acute otitis media caused by a penicillin-resistant pneumococcus strain? A gerbil model

The possible interference of acetaminophen, combined with antibiotics, in the treatment of acute otitis media (AOM) caused by a penicillin-resistant (minimal inhibitory concentration [MIC], 2 microg/mL), amoxicillin/clavulanic acid- and erythromycin-sensitive pneumococcus was evaluated in a gerbil model. Animals were challenged with approximately 5 x 106 bacteria in each ear through transbullar instillation. Acetaminophen was administered s.c. at 50 mg/kg 30 min before each antibiotic dose. Amoxicillin/clavulanic acid and erythromycin (2.5 and 10 mg/kg) were administered s.c. at 2, 10, and 18 h after inoculation. Samples were obtained from the middle ear (ME) on day 2 after inoculation for bacterial count. The overall results showed no difference between animals that received acetaminophen, with or without antibiotics, and those that did not receive acetaminophen. The antibiotic concentrations in the ME were practically identical in both groups of animals, so acetaminophen did not interfere with the pharmacokinetics of antibiotics in the ME. However, both antibiotics significantly reduced the number of culture-positive and the bacterial concentration in ME samples when compared with antibiotic-untreated animals. Both antibiotics, whether combined with acetaminophen or not, lowered the number of AOM to <25%, but >75% of animals presented otitis media with effusion, and no differences were shown between groups. A high rate of bacterial eradication from the ME correlated with antibiotic serum concentrations being over the MIC of the infecting organism for only >15% of the dose interval and with an ME concentration exceeding the MIC by a factor of 1.7. In this experimental model, acetaminophen had neither a synergistic nor an antagonistic effect on the antibiotics tested.

Diagnosis and treatment of acute otitis media: an assessment

OBJECTIVE

To assess compliance with the Centers for Disease Control and Prevention (CDC) evidence-based guidelines for the judicious use of antimicrobials in children with acute otitis media (AOM).

METHODS

Compliance with CDC's recommended diagnostic criteria and antimicrobial treatments for management of AOM was assessed by chart review and self-report for 29 community pediatricians in St. Louis, Missouri. For each physician, a simple random sample of AOM visits was selected and reviewed by trained reviewers. In addition, each physician completed a questionnaire.

RESULTS

Compliance with recommended diagnostic criteria was 38% (95% confidence interval: 34%-42%; n = 573) by chart audit and 41% (95% confidence interval: 24%-61%; n = 29) by self-report. Antimicrobial selection assessed by chart audit was consistent with CDC guidelines in 68% (95% confidence interval: 64%-72%) of visits for a new infection, 63% (95% confidence interval: 47%-78%) of visits for treatment failure, and 50% (95% confidence interval: 33%-67%) for recurrent disease. Self-reported compliance with treatment guidelines for new infection was 100% (95% confidence interval: 88%-100%) and 83% (95% confidence interval: 64%-94%) for treatment failure. Noncompliance was most frequently attributable to overuse of broad-spectrum antimicrobials. Most patients treated with amoxicillin received a 10-day course (98%). Subtherapeutic dosing occurred in 26% of patients treated with amoxicillin.

CONCLUSIONS

Overdiagnosis of AOM is common. Efforts to improve the judicious use of antimicrobials for AOM should focus on improving diagnostic accuracy, limiting the use of broad-spectrum antimicrobials to cases where they offer clinical benefit, and ensuring that amoxicillin dosing regimens are optimal.

Bacteriologic and clinical efficacy of high dose amoxicillin for therapy of acute otitis media in children

BACKGROUND

High dose (70 to 90 mg/kg/day) amoxicillin is recommended as first line therapy of acute otitis media (AOM) in geographic areas where drug-resistant Streptococcus pneumoniae is prevalent. Information on the bacteriologic efficacy of high dose amoxicillin treatment for AOM is limited.

OBJECTIVES

To evaluate the bacteriologic and clinical efficacy of high dose amoxicillin as first line therapy in AOM.

METHODS

In a prospective study 50 culture-positive patients ages 3 to 22 months (median, 9 months; 77% <1 year) were treated with high dose amoxicillin (80 mg/kg/day three times a day for 10 days) No antibiotics were administered 72 h before enrollment. Twenty-four (48%) patients presented with their first episode of AOM. Middle ear fluid was cultured by tympanocentesis at enrollment and on Days 4 to 6 of therapy. Additional middle ear fluid cultures were obtained if clinical relapse occurred. Bacteriologic failure was defined by positive cultures on Days 4 to 6 and clinical failure by no change or worsening of AOM signs and symptoms and requirement for additional antibiotics during therapy and/or at end of therapy. Patients were followed until Day 28 +/- 2. Susceptibility to penicillin and amoxicillin was measured by E-test.

RESULTS

Sixty-five organisms were recovered at enrollment: Haemophilus influenzae (38), Streptococcus pneumoniae (24), Streptococcus pyogenes (2) and Moraxella catarrhalis (1). Eighteen (75%) S. pneumoniae were nonsusceptible to penicillin (MIC > 0.1 microg/ml). All 24 S. pneumoniae isolates had amoxicillin MIC < or = 2.0 microg/ml. Thirteen (34%) of the 38 H. influenzae were beta-lactamase producers. Eradication was achieved in 41 (82%) patients for 54 of 65 (83%) pathogens: 22 of 24 (92%) S. pneumoniae, 21 of 25 (84%) beta-lactamase-negative H. influenzae, 8 of 13 (62%) beta-lactamase-positive H. influenzae, 2 of 2 S. pyogenes and 1 of 1 M. catarrhalis. Seven organisms not initially present were isolated on Days 4 to 6 in 5 patients: 3 beta-lactamase-positive H. influenzae; 1 beta-lactamase-negative H. influenzae; 2 S. pneumoniae; and 1 M. catarrhalis. In total 14 of 50 (28%) patients failed bacteriologically on Days 4 to 6 (persistence + new infection), of whom 9 (64%) had beta-lactamase-positive H. influenzae. Three (33%) of the 9 patients with bacteriologic failure (2 beta-lactamase-positive H. influenzae, 1 S. pneumoniae) failed also clinically on Days 4 to 6.

CONCLUSIONS

The predominant pathogens isolated from children with AOM failing high dose amoxicillin therapy were beta-lactamase-producing organisms. Because its overall clinical efficacy is good, high dose amoxicillin is still an appropriate choice as first line empiric therapy for AOM, followed by a beta-lactamase-stable drug in the event of failure.

Importance of respiratory viruses in acute otitis media

Acute otitis media is usually considered a simple bacterial infection that is treated with antibiotics. However, ample evidence derived from studies ranging from animal experiments to extensive clinical trials supports a crucial role for respiratory viruses in the etiology and pathogenesis of acute otitis media. Viral infection of the upper respiratory mucosa initiates the whole cascade of events that finally leads to the development of acute otitis media as a complication. The pathogenesis of acute otitis media involves a complex interplay between viruses, bacteria, and the host's inflammatory response. In a substantial number of children, viruses can be found in the middle-ear fluid either alone or together with bacteria, and recent studies indicate that at least some viruses actively invade the middle ear. Viruses appear to enhance the inflammatory process in the middle ear, and they may significantly impair the resolution of otitis media. Prevention of the predisposing viral infection by vaccination against the major viruses would probably be the most effective way to prevent acute otitis media. Alternatively, early treatment of the viral infection with specific antiviral agents would also be effective in reducing the occurrence of acute otitis media.

Patient, physician, and nurse satisfaction with antibiotics

To prospectively evaluate patient (parent), physician, and nurse satisfaction with antibiotics, 12,102 children in 661 pediatric study centers throughout the United States with infections to be treated on an outpatient basis were followed with questionnaires completed by parents and with interviews of patients and their parents. Comprehensive surveys were also completed by participating pediatricians and their nursing staffs of which 11,913 (98.4%) contained adequate information for inclusion in an analysis. Data were combined and analyzed using standard statistical methods. Loracarbef was perceived as being superior to other antibiotics based on cost, palatability, and dosing intervals. Few differences were seen among most antibiotics based on treatment outcome or adverse events. All antibiotics studied offered acceptable efficacy and were well tolerated as judged by physicians, nurses, parents, and children. Slight differences might result in increased compliance for some patients.

Microdialysis studies of the middle ear distribution kinetics of amoxicillin in the awake chinchilla

This work was performed to develop an experimental animal model for the study of antibiotic drug distribution into middle ear fluid (MEF) and to evaluate its relevance and significance to the clinical treatment of otitis media (OM). Chinchillas were assigned to normal or infected ear groups after Eustachian tube obstruction (ETO) or direct trans-bullar inoculation with type 3 Streptococcus pneumoniae. Following survival surgery to implant microdialysis (MD) probes in the jugular vein and middle ear (ME), amoxicillin was given intravenously (iv) as a bolus or infusion. Drug concentrations in blood and MEF were continuously monitored by microdialysis. The measured concentrations were corrected for probe recovery by simultaneous retrodialysis. Multiple MEF and blood sampling was also performed to validate the animal model and MD sampling technique. Bacterial infection was successfully induced 3-7 days after the inoculation, whereas the control group gave negative bacterial culture results. The beta-lactam antibiotic, amoxicillin, exhibited an elimination half-life of 0.33+/-0.23 h (n = 9) in chinchilla blood, 1.46+/-0.50 h (n = 5) and 1.75+/-0.84 h (n = 4) in MEF of normal and infected ears (p = 0.6), respectively. MEF-to-blood amoxicillin concentration ratios at steady state following iv infusion were 0.26+/-0.06 (n = 5) and 0.28+/-0.11 (n = 4) for normal and infected ears (p = 0.7), respectively. MD allows continuous monitoring of drug concentration-time profiles in blood and MEF in an awake chinchilla model. The concentrations measured by MD were validated by direct sampling. The ratio of the area under the curve (AUC) of drug concentration in MEF versus time to that in blood after iv bolus doses was less than unity, as was the steady-state concentration ratio following constant-rate iv infusion, suggesting an active transport mechanism was involved in the efflux of amoxicillin from the ME of chinchilla. The results of studies involving infected ears were not significantly different from those in normal ears in terms of amoxicillin distribution across the ME mucosal membrane after systemic administration.

Microbiology of acute otitis media recently treated with aminopenicillins

INTRODUCTION

Sparse recent data are available in the United States regarding the pathogens of acute otitis media (AOM) most likely to be recovered from children recently treated with the two most frequently prescribed antibiotics, amoxicillin or amoxicillin/clavulanate (AMC).

METHODS

Of the 704 rural Kentucky children with culture-positive AOM who underwent a single tympanocentesis or culture of otorrhea between 1992 and 1998, 96 pathogens were recovered from 90 children during therapy or within 7 days posttherapy with an aminopenicillin. Identification and susceptibility testing of AOM pathogens were performed by routine National Committee for Clinical Laboratory Standards methods.

RESULTS

Pathogens recovered from children with AOM recently treated (0 to 7 days) with amoxicillin (n = 38) and AMC (n = 58), respectively, were as follows: Haemophilus influenzae (beta-lactamase-negative), 16 and 29%; H. influenzae (beta-lactamase-positive), 11 and 22%; penicillin-susceptible Streptococcus pneumoniae, 26 and 12%; intermediately penicillin-nonsusceptible S. pneumoniae (PNSP), 20 and 10%; resistant PNSP 13 and 17%; Moraxella catarrhalis (beta-lactamase-positive), 13 and 7%; and Streptococcus pyogenes, 3 and 2%. H. influenzae was also isolated from 8 (75%) of 12 children treated with high dose AMC ( approximately 80 mg/kg/day amoxicillin component). Significantly fewer children recently treated with amoxicillin were otitis-prone than those given AMC (24% vs. 74%, P < 0.0001).

CONCLUSIONS

The predominant pathogen recovered from children with AOM recently treated with amoxicillin was S. pneumoniae (59%) rather than beta-lactamase-producing organisms (24%). H. influenzae was the predominant (51%) pathogen, rather than PNSP (27%), recovered from children recently treated with AMC.

Compliance issues related to the selection of antibiotic suspensions for children

OBJECTIVE

To evaluate the palatability, cost and other compliance issues as variables in the selection of antibiotic suspensions for children.

METHODS

Eighty-six physicians and health care personnel randomly sampled amoxicillin (used as a standard for comparison) and 11 other antibiotics, evaluating them in categories of appearance, smell, texture, taste and aftertaste. Overall scoring was then adjusted for cost, duration of therapy and dosing intervals.

RESULTS

Overall taste (palatability) ranking of antibiotics, highest to lowest, was as follows: loracarbef, cefdinir, cefixime, azithromycin, ciprofloxacin, trimethoprim-sulfamethoxazole, clarithromycin, trimethoprim, amoxicillin/clavulanate, cefpodoxime and cefuroxime. Overall rating of antibiotics was greatly influenced by other compliance variables, in order of their impact: cost; duration of therapy (5 vs. 10 days); and dosing intervals. Cost was not judged to be a major factor by most participants unless antibiotic expense was >$50.00 for treatment of otitis media in our hypothetical 2-year-old, 13-kg child. Taking all variables into consideration, final ranking from highest to lowest was azithromycin, cefdinir, loracarbef, cefixime, amoxicillin, trimethoprim-sulfamethoxazole, cefpodoxime, trimethoprim, clarithromycin, ciprofloxacin, cefuroxime and amoxicillin/clavulanate.

CONCLUSIONS

Variables related to compliance for families filling antibiotic prescriptions and children taking these products are important in the selection of antimicrobial therapy. Because final assessment is likely to vary considerably among health care personnel, decisions must be made on an individual basis.

treatment and prevention of otitis media

OBJECTIVE

To review and summarize recent advances in the treatment and prevention of otitis media (OM).

DATA SOURCES

A MEDLINE search (1996-March 2000) was performed to identify relevant primary and review articles. References from these articles were also reviewed if deemed important.

STUDY SELECTION AND DATA EXTRACTION

English-language primary and review articles focusing on the treatment and prevention of acute otitis media (AOM) were included. Studies focusing exclusively on OM with effusion or serous OM and chronic suppurative OM were excluded. Information regarding prevention and drug therapy was reviewed, with an emphasis placed on advances made in the last two years.

DATA SYNTHESIS

Recently, an expert panel of the Centers for Disease Control and Prevention recommended use of only three of 16 systemic antibiotics approved by the Food and Drug Administration for treatment of AOM: amoxicillin, cefuroxime axetil, and ceftriaxone. Controversy exists over the importance of key selection factors used by the expert panel in determining which antibiotics to recommend in a two-step treatment algorithm, that is, in vitro data, pharmacodynamic profiles, and necessity for coverage of drug-resistant Streptococcus pneumoniae at all steps of empiric treatment. Additional antibiotic and patient selection factors useful for individualizing therapy include clinical efficacy, adverse effects, frequency and duration of administration, taste, cost, comorbid infections, and ramifications should bacterial resistance develop to the chosen antibiotic. Presumed or past patient/caregiver adherence (especially when antibiotic failure has occurred) is also paramount in selecting antibiotic therapy. A three-step treatment algorithm for refractory AOM that employs amoxicillin, trimethoprim/sulfamethoxazole (TMP/SMX), or high-dose amoxicillin/clavulanate (depending on the prior dose of and adherence to amoxicillin therapy), and ceftriaxone or tympanocentesis at steps 1, 2, and 3, respectively, appears rational and cost-effective. The recent upsurge in antimicrobial resistance is highlighted, and recommendations are presented for the treatment of AOM and prevention of recurrent otitis media (rAOM).

CONCLUSIONS

Amoxicillin remains the antibiotic of choice for initial empiric treatment of AOM, although the traditional dosage should be increased in patients at risk for drug-resistant S. pneumoniae. In cases refractory to high-dose amoxicillin, TMP/SMX should be prescribed if adherence to prior therapy seemed good or complete, or high-dose amoxicillin/clavulanate if adherence was incomplete or questionable. Ceftriaxone should be reserved as third-line treatment. The increasing prevalence of drug-resistant S. pneumoniae emphasizes the importance of alternative medical approaches for the prevention of OM, as well as judicious antibiotic use in established cases. Removal of modifiable risk factors should be first-line therapy for prevention of rAOM. We support the use of conjugate pneumococcal vaccine per guidelines for prevention of rAOM from the Advisory Committee on Immunization Practice of the Centers for Disease Control and Prevention, with consideration given to influenza vaccine for cases of rAOM that historically worsen during the flu season. Sulfisoxazole prophylaxis should be reserved for children who are immunocompromised, have concurrent disease states exacerbated by AOM, or meet the criteria of rAOM despite conjugate pneumococcal and influenza vaccination. Therapy should be intermittent, beginning at the first sign of an upper respiratory infection, and should continue for 10 days. The invasive nature and risks of anesthesia relegate myringotomy, tympanostomy tubes, and adenoidectomy to last-line therapies for rAOM.