Increasing antibiotic resistance among otitis media pathogens and their susceptibility to oral agents based on pharmacodynamic parameters

Assessment of ototoxicity of tea tree oil in a chinchilla animal model

OBJECTIVE

The aim of the present study is to examine the effects of tea tree oil on hearing function and cochlear morphology after intratympanic administration in a chinchilla animal model.

METHODS

Nine chinchillas received intratympanic injection of 3% tea tree oil dissolved in olive oil in one ear, whereas the contralateral control ear received olive oil only. Outcome measures included auditory brainstem responses conducted before treatment and at 10 days and 30 days following the injection. Post-mortem cochlear morphology was assessed using scanning electron microscopy.

RESULTS

At 10 and 30 days following the injection, there was no significant change in auditory brain response thresholds at 8, 16, 20 or 25kHz. Scanning electron microscopy imaging showed no damage to auditory hair cells.

CONCLUSION

Tea tree oil (3%) does not appear to be ototoxic in a chinchilla animal model. Future preclinical and clinical studies are required to establish the effectiveness of TTO in treating otitis.

Antimicrobial resistance trends among community-acquired respiratory tract pathogens in Greece, 2009-2012

The aim of the present study was to determine the antimicrobial resistance trends of respiratory tract pathogens isolated from patients with community-acquired respiratory tract infections (CARTIs) in Crete, Greece, over a 4-year period (2009-2012). A total of 588 community-acquired respiratory pathogens were isolated during the study period. Streptococcus pneumoniae was the most common organism responsible for 44.4% of CARTIs, followed by Haemophilus influenzae (44.2%) and Moraxella catarrhalis (11.4%). Among S. pneumoniae, the prevalence of isolates with intermediate- and high-level resistance to penicillin was 27.2% and 12.3%, respectively. Macrolide resistance slightly decreased from 29.4% over the period 2009-2010 to 28.8% over the period 2011-2012. Multiresistance was observed among 56 (54.4%) penicillin nonsusceptible isolates. A nonsignificant increase in resistance of H. influenzae isolates was noted for β -lactams, cotrimoxazole, and tetracycline. Among the 67 M. catarrhalis tested, 32 produced beta-lactamase and were resistant to ampicillin. Macrolide resistance decreased over the study period. All isolates were susceptible to amoxicillin + clavulanic acid, chloramphenicol, rifampicin, and the fluoroquinolones. Although a decreasing trend in the prevalence of resistance of the three most common pathogens involved in CARTIs was noted, continuous surveillance of antimicrobial susceptibility at the local and national level remains important, in order to guide appropriate empirical antimicrobial therapy.

Risks of population antimicrobial resistance associated with chronic macrolide use for inflammatory airway diseases

Macrolide antibiotics have established efficacy in the management of cystic fibrosis and diffuse panbronchiolitis-uncommon lung diseases with substantial morbidity and the potential for rapid progression to death. Emerging evidence suggests benefits of maintenance macrolide treatment in more indolent respiratory diseases including chronic obstructive pulmonary disease and non-cystic fibrosis bronchiectasis. In view of the greater patient population affected by these disorders (and potential for macrolide use to spread to disorders such as chronic cough), widespread use of macrolides, particularly azithromycin, has the potential to substantially influence antimicrobial resistance rates of a range of respiratory microbes. In this Personal View, I explore theories around population (rather than patient) macrolide resistance, appraise evidence linking macrolide use with development of resistance, and highlight the risks posed by injudicious broadening of their use, particularly of azithromycin. These risks are weighed against the potential benefits of macrolides in less aggressive inflammatory airway disorders. A far-sighted approach to maintenance macrolide use in non-cystic fibrosis inflammatory airway diseases is needed, which minimises risks of adversely affecting community macrolide resistance: combining preferential use of erythromycin and restriction of macrolide use to those patients at greatest risk represents an appropriately cautious management approach.

Evaluation of a rapid immunochromatographic ODK-0901 test for detection of pneumococcal antigen in middle ear fluids and nasopharyngeal secretions

Since the incidence of penicillin-resistant Streptococcus pneumoniae has been increasing at an astonishing rate throughout the world, the need for accurate and rapid identification of pneumococci has become increasingly important to determine the appropriate antimicrobial treatment. We have evaluated an immunochromatographic test (ODK-0901) that detects pneumococcal antigens using 264 middle ear fluids (MEFs) and 268 nasopharyngeal secretions (NPSs). A sample was defined to contain S. pneumoniae when optochin and bile sensitive alpha hemolytic streptococcal colonies were isolated by culture. The sensitivity and specificity of the ODK-0901 test were 81.4% and 80.5%, respectively, for MEFs from patients with acute otitis media (AOM). In addition, the sensitivity and specificity were 75.2% and 88.8%, respectively, for NPSs from patients with acute rhinosinusitis. The ODK-0901 test may provide a rapid and highly sensitive evaluation of the presence of S. pneumoniae and thus may be a promising method of identifying pneumococci in MEFs and NPSs.

Antimicrobial-resistant Streptococcus pneumoniae: trends and management

Management of pneumococcal infections has been challenged by the development of resistance and, more recently, the unexpected spread of resistant clones of serotypes, such as 19A, following the introduction of a conjugate pneumococcal vaccine for use in children in 2000. High-dose penicillin G and many other agents continue to be efficacious parenterally for pneumonia and bacteremia. However, treatment options for meningitis and for infections treated with oral agents, particularly in children, have been limited by resistance. Empiric treatment guidelines should reflect the emerging threats from increased drug resistance. Compliance with guidelines by physicians and patients is important to prevent further development of resistance as new classes of agents are unlikely to be available in the next decade.

Serotype distribution and penicillin resistance of Streptococcus pneumoniae isolates from middle ear fluids of pediatric patients with acute otitis media in Japan

Out of 175 pneumococcal isolates from middle ear fluids, 26.3% were penicillin-resistant S. pneumoniae (PRSP). Serotypes 19F and 23F occurred most frequently among PRSP strains. The 7-valent pneumococcal conjugate vaccine (PCV) showed better coverage of PRSP strains (87.0%). The 7-valent PCV may reduce the prevalence of PRSP in Japan.

Determination of pneumococcal serotypes/genotypes in nasopharyngeal secretions of otitis media children by multiplex PCR

The appropriate clinical applications of pneumococcal polysaccharide vaccines against recent increases in antimicrobial resistant Streptococcus pneumoniae (S. pneumoniae) urgently require accurate analytical methodologies for determining and characterizing the serotypes. The results of current immunological determinations of serotypes with anti-capsular polysaccharide-specific sera are difficult to interpret in terms of quellung changes of the pneumococci. In this study, we applied the multiplex PCR technique for the rapid identification of pneumococci and simultaneous rapid determinations of their serotypes and genotypes that directly correlated with antimicrobial susceptibilities from nasopharyngeal secretions (NPS). Serogroups 6, 19F and 23F were the predominant capsular types of S. pnuemoniae in the NPS samples. Strains of serotypes 19F and 23F frequently had mutations in pbp1a, pbp2x and pbp2b and expressed ermB and mefA; they also were mostly resistant to both penicillin G (PCG) and clarithromycin (CAM). Two NPS samples contained the strain of serotype 19F together with the strain of serotype 23F, although only the strain of serotype 19F was identified by a conventional bacterial culture. Pneumococci were identified in six NPS samples and their serotypes determined by the multiplex PCR, while a conventional bacterial culture failed to identify the pathogens. Our findings suggest that PCR-based serotyping and genotyping can provide an accurate and rapid distribution of pneumococcal serotypes and antimicrobial resistance. The relatively minor populations in the nasopharynx may be determined using molecular techniques.

Activity of faropenem against middle ear fluid pathogens from children with acute otitis media in Costa Rica and Israel

Faropenem was tested against 1,188 middle ear fluid pathogens from children in Israel and Costa Rica. Against Streptococcus pneumoniae and Haemophilus influenzae, faropenem was the most active beta-lactam, with activity that was similar to or greater than of the other oral antimicrobial classes studied. Faropenem was also active against Moraxella catarrhalis and Streptococcus pyogenes.

An open-label, double tympanocentesis study of levofloxacin therapy in children with, or at high risk for, recurrent or persistent acute otitis media

BACKGROUND

Levofloxacin has excellent activity against common respiratory pathogens and therefore is likely to be effective in treating children with persistent or recurrent otitis media.

OBJECTIVE

The objective of this study was to assess the efficacy and safety of levofloxacin treatment in the eradication of bacterial pathogens from the middle ear fluid (MEF) of children with, or at high risk for, persistent or recurrent otitis media.

METHODS

An open-label multicenter trial was conducted that involved tympanocentesis at entry and selectively 3 to 5 days after starting levofloxacin (10 mg/kg twice a day for 10 days).

RESULTS

: Two hundred five children (80% < or =2 years) were enrolled. One child did not have a confirmed diagnosis of acute otitis media and did not return for follow-up visits. Of the remaining 204 children, 94 (46%) had bilateral infection and 63 (31%) were receiving antimicrobials immediately before entry. One hundred five isolates of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Streptococcus. pyogenes were recovered in pure or mixed cultures. All isolates were susceptible to levofloxacin. During-treatment bacterial eradication from MEF occurred in 88% (78 of 89) of bacteriologically evaluable patients, including 90% (65 of 72) of children < or =24 months of age. Bacteria initially isolated from MEF were eradicated in 31 of 37 (84%) children infected with S. pneumoniae and in 54 of 54 (100%) children infected with H. influenzae. Overall, clinical success rate after therapy was 94% for the total study population and 92% for the bacteriologically evaluable population. Levofloxacin was well tolerated. Vomiting (4%) was the most common treatment-limiting adverse event.

CONCLUSIONS

Levofloxacin was safe and effective in treating and eradicating common bacterial pathogens from MEF in children with, or at risk for, recurrent or persistent otitis media.

Single-dose azithromycin for the treatment of children with acute otitis media

Azithromycin is an azalide with in vitro activity against otitis media pathogens, good middle ear penetration and a prolonged half-life. A total of four clinical trials have evaluated the clinical success rate, safety and compliance of single-dose azithromycin (30 mg/kg) in the treatment of children with otitis media. Among all the patients treated with single-dose azithromycin (30 mg/kg), and presented previously in four published clinical trials, end-of-treatment clinical success was 88% (544 out of 619) and maintained clinical success at the end-of-study was 82% (498 out of 610). Three of the four studies included a mandatory baseline tympanocentesis. The overall end-of-treatment and end-of-study clinical success rates among all culture-positive patients was 84% (222 out of 263) and 80% (210 out of 263), respectively. Per pathogen end-of-treatment clinical success rates observed were 91% (125 out of 137) among patients with Streptococcus pneumoniae, 77% (75 out of 97) among patients with Haemophilus influenzae, 100% (14 out of 14) among patients with Moraxella catarrhalis, 64% (seven out of 11) among patients with baseline Streptococcus pyogenes and 25% (one out of four) among patients with a S. pneumoniae and H. influenzae mixed infection. Clinical success was observed in 90% (106 out of 118) of patients with baseline macrolide-susceptible S. pneumoniae and in 67% (14 out of 21) among patients with baseline macrolide-resistant S. pneumoniae (p = 0.01). Adverse events were uncommon, mostly mild and transitory gastrointestinal complaints, and in the two larger comparative trials, were less frequent than the rates observed with the comparator agents. Compliance was excellent (99-100%). Single-dose azithromycin (30 mg/kg) represents an alternative for the treatment of pediatric patients with uncomplicated acute otitis media, particularly in those geographic regions where high-level S. pneumoniae macrolide resistance is uncommon, and for those patients that require directly observed therapy or when compliance may be a problem.

Penicillin resistance is not extrapolable to amoxicillin resistance in Streptococcus pneumoniae isolated from middle ear fluid in children with acute otitis media

OBJECTIVES

We evaluated the in vitro antibacterial activity of amoxicillin against penicillin-susceptible and -nonsusceptible Streptococcus pneumoniae strains isolated from children with acute otitis media (AOM).

METHODS

Children more than 3 months of age with AOM who were seen in the Dr Sótero del Rio and Luis Calvo Mackenna Hospitals in Santiago, Chile, between July 1998 and December 2002 were subjected to tympanic puncture for middle ear fluid culture. The penicillin and amoxicillin susceptibilities of the S pneumoniae isolates were determined by epsilometer test (E test).

RESULTS

A bacterial pathogen was isolated in 432 of 543 children (80%) as follows: S pneumoniae, 40%; Haemophilus influenzae, 29%; Moraxella catarrhalis, 7%; and Streptococcus pyogenes, 4%. Penicillin-susceptible S pneumoniae strains were less common than amoxicillin-susceptible strains (60% versus 95%; odds ratio [OR], 0.08; 95% confidence interval [CI], 0.04 to 0.18). Both intermediate- and high-resistance strains were more common for penicillin (22% versus 4.5%; OR, 5.6; 95% CI, 2.5 to 12.7) than for amoxicillin (18% versus 0.5%; OR, 41.3; 95% CI, 6.0 to 821).

CONCLUSIONS

Penicillin resistance is not extrapolable to amoxicillin among S pneumoniae strains isolated from middle ear fluid of children with AOM. Our results support the recommendation to evaluate the minimal inhibitory concentrations of penicillin-nonsusceptible S pneumoniae for amoxicillin and to continue use of this antimicrobial as a first-line antimicrobial choice for children with AOM.

Cefdinir pharmacokinetics and tolerability in children receiving 25 mg/kg once daily

BACKGROUND

Of several oral cephalosporins, cefdinir is recommended as an alternative therapy for children with acute otitis media who have type 1 hypersensitivity to beta-lactams. Because the current cefdinir dosage of 14 mg/kg/d is approved for treatment of acute otitis media caused by penicillin-susceptible Streptococcus pneumoniae, we hypothesized that a 25-mg/kg dose given daily would be more effective for nonsusceptible S. pneumoniae.

METHODS

We performed pharmacokinetic analyses on 37 infants and children who were given cefdinir in dosages of 14 or 25 mg/kg once daily for 10 days, for the treatment of respiratory and skin or skin structure infections. Cefdinir plasma concentrations were determined with validated liquid chromatology, and pharmacokinetics and pharmacodynamics were determined in relation to the minimum inhibitory concentration values of S. pneumoniae.

RESULTS

The maximal plasma concentrations and area-under-the-curve values were significantly higher after the 25-mg/kg in relation to the minimum inhibitory concentration values for S. pneumoniae strains. The pharmacodynamics measure of bacteriologic effectiveness was <40% of the dosing interval (ie, 24 hours), indicating that many of the penicillin-nonsusceptible S. pneumoniae causing acute otitis media would not be effectively treated. Diarrhea occurred in 20% of the 39 subjects that received the larger dosage of cefdinir.

CONCLUSION

A cefdinir dosage of 25 mg/kg daily would be ineffective for treatment of acute otitis media caused by penicillin-nonsusceptible S. pneumoniae strain.

Management of acute bacterial rhinosinusitis: current issues and future perspectives

Acute bacterial rhinosinusitis (ABRS), which manifests as an inflammation of at least one of the paranasal sinuses, is a major public health issue in developed countries. Diagnosis and treatment of ABRS can pose significant challenges in clinical practice, including difficulty in differentiation between viral and bacterial infection and a lack of simple, reliable and convenient methods for definitive diagnosis. Treatment choice is also a challenge because a decision is typically made empirically; therefore, the selection of therapy should be based on knowledge of local patterns of antimicrobial resistance, spectrum of activity against the most common ABRS pathogens (including those that are resistant to penicillins and macrolides) and pharmacodynamic potency. Current guidelines for diagnosis and treatment of ABRS in various countries share some similarities but also have important differences. Criteria for making the clinical diagnosis of sinusitis vary only slightly from country to country, while recommendations of therapy reflect the local impact of bacterial resistance.

Evaluation of serotypes of Streptococcus pneumoniae isolated from otitis media patients by multiplex polymerase chain reaction

The increasing difficulty in the management of pneumococcal acute otitis media in parallel with increases in antimicrobial-resistant strains has led to much interest in pneumococcal capsular types for the adoption of effective prevention by vaccines. This study shows that multiplex polymerase chain reaction is a valuable and expeditious method for the capsular typing of pneumococci. The multiplex polymerase chain reaction method accurately detects the majority of serotypes and serogroups frequently isolated from pediatric patients with acute otitis media, allowing the characterization of the colonization patterns for further implications of pneumococcal vaccines.

Otitis media: re-evaluation of diagnosis and treatment in the era of antimicrobial resistance, pneumococcal conjugate vaccine, and evolving morbidity

The changing susceptibility of bacterial otopathogens is only one aspect of the evolving concepts regarding pathogenesis, immunoprophylaxis, pharmacodynamics, and sequelae of acute otitis media that mandates new insights for achieving a successful outcome. 2004 guidelines by the American Academy of Pediatrics for the treatment of acute otitis media provide one perspective that proposes a rethinking of the routine use of antimicrobial therapy with the hope of preventing further increases in bacterial resistance among otopathogens. The goals of this article are to incorporate the advances in diagnosis, treatment, prevention, and management of sequelae into strategies that optimize the outcome of acute otitis media and limit further emergence of resistant otopathogens.

Large dosage amoxicillin/clavulanate, compared with azithromycin, for the treatment of bacterial acute otitis media in children

BACKGROUND

A large dosage pediatric formulation of amoxicillin/clavulanate with an improved pharmacokinetic/pharmacodynamic profile was developed to eradicate many penicillin-resistant strains of Streptococcus pneumoniae and Haemophilus influenzae (including beta-lactamase-producing strains).

METHODS

This randomized, investigator-blinded, multicenter trial examined treatment of bacterial acute otitis media (AOM) in children 6-30 months of age with amoxicillin/clavulanate (90/6.4 mg/kg/d in 2 divided doses for 10 days) versus azithromycin (10 mg/kg for 1 day followed by 5 mg/kg/d for 4 days). Tympanocentesis was performed at entry for bacteriologic assessment, at the on-therapy visit (day 4-6) to determine bacterial eradication and at any time before the end-of-therapy visit (day 12-14) if the child was categorized as experiencing clinical failure. Clinical assessments were performed at the on-therapy, end-of-therapy and follow-up (day 21-25) visits.

RESULTS

We enrolled 730 children; AOM pathogens were isolated at baseline for 249 of the amoxicillin/clavulanate group and 245 of the azithromycin group. For children with AOM pathogens at baseline, clinical success rates at the end-of-therapy visit were 90.5% for amoxicillin/clavulanate versus 80.9% for azithromycin (P < 0.01), and those at the on-therapy and follow-up visits were 94.9% versus 88.0% and 80.3% versus 71.1%, respectively (all P < 0.05). At the on-therapy visit, pretherapy pathogens were eradicated for 94.2% of children receiving amoxicillin/clavulanate versus 70.3% of those receiving azithromycin (P < 0.001). Amoxicillin/clavulanate eradicated 96.0% of S. pneumoniae (92.0% of fully penicillin-resistant S. pneumoniae) and 89.7% of H. influenzae (85.7% [6 of 7 cases] of beta-lactamase-positive H. influenzae). Corresponding rates for azithromycin were 80.4% (54.5%) for S. pneumoniae and 49.1% (100% [1 of 1 case]) for H. influenzae (all P < 0.01 for between-drug comparisons).

CONCLUSION

Amoxicillin/clavulanate was clinically and bacteriologically more effective than azithromycin among children with bacterial AOM, including cases caused by penicillin-resistant S. pneumoniae and beta-lactamase-positive H. influenzae.

Effect of pneumococcal vaccination on quality of life in children with recurrent acute otitis media: a randomized, controlled trial

BACKGROUND

Limited effectiveness of current treatment strategies for recurrent acute otitis media (RAOM) and increasing antibiotic resistance have diverted attention to prevention of AOM by vaccination. Pneumococcal vaccination for AOM seems to have only modest clinical efficacy. Thus far, the effects on health-related quality of life (HRQoL) or functional health status (FHS) have not been studied.

OBJECTIVE

To assess the effect of vaccination on HRQoL or FHS.

METHODS

In a double-blind, randomized, controlled trial, 383 children 1 to 7 years old with RAOM were vaccinated with either heptavalent pneumococcal conjugate vaccine followed by pneumococcal polysaccharide vaccine (pneumococcal group: n = 190) or with hepatitis A or B vaccines (control group: n = 193). Parents completed validated Dutch versions of 8 HRQoL and FHS instruments assessing generic FHS (Rand, Functional Status Questionnaire specific, and Functional Status Questionnaire generic), otitis media-specific FHS (OM-6), otitis media-specific child HRQoL (Numerical Rating Scale for Child), family functioning (Family Functioning Questionnaire), and otitis media-specific caregiver HRQoL (Numerical Rating Scale for Caregiver). Scores were compared at baseline and at 14 and 26 months' follow-up.

RESULTS

At baseline, the average AOM incidence in the pneumococcal and control group was 5.0 (SD: 2.8) and 4.9 (SD: 2.6) episodes per year, respectively, with 38.4% and 36.8% having suffered from > or =6 episodes per year. AOM frequency decreased 4.4 episodes per year in both groups, with a considerable and comparable improvement in HRQoL and FHS. No substantial differences in HRQoL or FHS were found between the pneumococcal and the control group at baseline or at 14 or 26 months' follow-up.

CONCLUSION

Pneumococcal vaccination has no beneficial effect compared with control vaccination on either HRQoL or FHS in children 1 to 7 years old with RAOM.

Seven valent pneumococcal conjugate vaccine immunization in two Boston communities: changes in serotypes and antimicrobial susceptibility among Streptococcus pneumoniae isolates

BACKGROUND

Seven valent pneumococcal conjugate vaccine (PCV7) was licensed and introduced in 2000 for universal administration of children younger than 2 years of age and for selective immunization of children 2-5 years of age.

SPECIFIC AIMS

To identify changes in colonization and antimicrobial susceptibility among Streptococcus pneumoniae organisms after introduction of PCV7.

METHODS

Infants and children ages 2-24 months were enrolled in surveillance study of nasopharyngeal carriage of S. pneumoniae. Nasopharyngeal cultures for S. pneumoniae were performed at all well child visits and illness visits of children with acute otitis media. S. pneumoniae organisms were serotyped, and antimicrobial susceptibilities to penicillin, amoxicillin, trimethoprim-sulfamethoxazole and azithromycin were performed.

RESULTS

During the 3-year period (October 2000 through September 2003), nasopharyngeal colonization with vaccine serotypes declined from 22% to 2%, and nonvaccine serotypes increased from 7% to 16%. Rates of antibiotic resistance of S. pneumoniae isolates to penicillin, amoxicillin, azithromycin and trimethoprim-sulfamethoxazole were 29.3, 2.2, 26.5 and 28.1%, respectively.

CONCLUSIONS

PCV7 immunization produces a marked decline in vaccine serotypes carried in the nasopharynx of young children, with a coincident rise in the prevalence of nonvaccine serotypes. Important shifts in antimicrobial susceptibility have not been observed to date.

Developing community-specific recommendations for first-line treatment of acute otitis media: is high-dose amoxicillin necessary?

OBJECTIVES

National recommendations are to use high-dose amoxicillin (80-90 mg/kg per day) to treat uncomplicated acute otitis media (AOM) in children who are at high risk for infection with nonsusceptible Streptococcus pneumoniae (NSSP). However, high-dose treatment may not be necessary if the local prevalence of NSSP is low. The objective of this study was to estimate the local prevalence of NSSP in children with acute upper respiratory illnesses and to develop community-specific recommendations for first-line empiric treatment of AOM.

METHODS

We conducted a cross-sectional prevalence study in the offices of 7 community pediatricians in St Louis, Missouri. S pneumoniae was isolated from nasopharyngeal swabs collected from children who were younger than 7 years and had AOM, nonspecific upper respiratory infection, cough, acute sinusitis, or pharyngitis. Children were excluded from the study when they had received an antibiotic in the previous 4-week period. Parents and providers completed a brief questionnaire to assess risk factors for carriage of NSSP. On the basis of National Clinical Chemistry Laboratory Standards, isolates with a penicillin minimum inhibitory concentration > or =0.12 microg/mL were considered to be nonsusceptible to penicillin (NSSP), and isolates with a penicillin minimum inhibitory concentration >2 microg/mL were categorized as nonsusceptible to standard-dose amoxicillin (35-45 mg/kg per day; NSSP-A).

RESULTS

S pneumoniae was isolated from the nasopharynx of 85 (40%) of 212 study patients (95% confidence interval [CI]: 33%-47%); 41 (48%) of 85 isolates were NSSP (95% CI: 37%-59%), and 6 (7%) were NSSP-A (95% CI: 1.5%-13%). Among the 212 study patients, the prevalence of NSSP was 19% (95% CI: 14%-25%), and the prevalence of NSSP-A was 3% (95% CI: 0.6%-5%). Carriage of NSSP was increased in child care attendees compared with nonattendees (29% vs 14%; odds ratio: 2.6; 95% CI: 1.3-5.2).

CONCLUSIONS

In our community, although the prevalence of NSSP among isolates of S pneumoniae identified from the nasopharynx of symptomatic children is high (48%), the probability of NSSP-A infection among symptomatic children is <5%. Our data support a recommendation to treat most children who have uncomplicated AOM with standard-dose amoxicillin. Children who attend child care or have recently received an antibiotic may require treatment with high-dose amoxicillin. Other communities may benefit from a similar assessment of the prevalence of NSSP and NSSP-A.

Antimicrobial resistance of Streptococcus pneumoniae and Haemophilus influenzae in Sao Paulo, Brazil from 1996 to 2000

This study was undertaken to assess the in vitro activity of several antimicrobial agents against Brazilian isolates of Streptococcus pneumoniae and Haemophilus influenzae from 1996 to 2000. The antibiotics used were penicillin, amoxicillin/clavulanic acid (A/C), ampicillin, amoxicillin, cefaclor, cefdinir, cefixime, cefprozil, ceftriaxone, cefuroxime, azithromycin, clarithromycin, erythromycin, ciprofloxacin, levofloxacin, ofloxacin, chloramphenicol, clindamycin, doxycycline and trimethoprim/sulphamethoxazole (T/S). MICs were determined by the National Committee for Clinical Laboratory Standards (NCCLS) method and interpreted using NCCLS and PK/PD breakpoints. For S. pneumoniae 80.0% were penicillin susceptible, 18.3% intermediate, 1.7% resistant; most active agents were amoxicillin, A/C, ceftriaxone and levofloxacin; T/S was the least active agent. Beta-lactamase was produced by 13.7% of H. influenzae. All were susceptible to A/C, cefdinir, cefixime, ceftriaxone and quinolones. The least active agents were T/S and macrolides.

Mechanisms of resistance among respiratory tract pathogens

Antimicrobial resistance among respiratory tract pathogens represents a significant health care threat. Identifying the antimicrobial agents that remain effective in the presence of resistance, and knowing why, requires a thorough understanding of the mechanisms of action of the various agents as well as the mechanisms of resistance demonstrated among respiratory tract pathogens. The primary goal of antimicrobial therapy is to eradicate the pathogen, via killing or inhibiting bacteria, from the site of infection; the defenses of the body are required for killing any remaining bacteria. Targeting a cellular process or function specific to bacteria and not to the host limits the toxicity to patients. Currently, there are four general cellular targets to which antimicrobials are targeted: cell wall formation and maintenance, protein synthesis, DNA replication, and folic acid metabolism. Resistance mechanisms among respiratory tract pathogens have been demonstrated for all four targets. In general, the mechanisms of resistance used by these pathogens fall into one of three categories: enzymatic inactivation of the antimicrobial, prevention of intracellular accumulation, and modification of the target site to which agents bind to exert an antimicrobial effect. Resistance to some agents can be overcome by modifying the dosage regimens (e.g., using high-dose therapy) or inhibiting the resistance mechanism (e.g., b-lactamase inhibitors), whereas other mechanisms of resistance can only be overcome by using an agent from a different class. Understanding the mechanisms of action of the various agents and the mechanisms of resistance used by respiratory tract pathogens can help clinicians identify the agents that will increase the likelihood of achieving optimal outcomes.

Single dose azithromycin for the treatment of uncomplicated otitis media

Three clinical trials have examined the efficacy and safety of single dose azithromycin (30 mg/kg) in children with uncomplicated acute otitis media (AOM). In the first trial, a small pilot study, the clinical and microbiologic efficacy of single dose azithromycin was comparable with that of 3-day azithromycin or single dose ceftriaxone. A second, non-comparative trial confirmed the clinical and microbiologic efficacy of the single dose regimen. The third study, a large double blind, double dummy trial, demonstrated comparable clinical success rates between single dose azithromycin and 10-day standard amoxicillin/clavulanate. The incidence of drug-related adverse events in patients treated with single dose azithromycin was low in all three trials and similar to rates that have been reported for other antimicrobial agents used for the treatment of patients with AOM. In the amoxicillin/clavulanate trial, compliance with single dose azithromycin was significantly better than with the amoxicillin/clavulanate regimen (P < 0.001). We conclude that a single dose of azithromycin (30 mg/kg) is safe and effective for the treatment of uncomplicated AOM in children.

Management of recurrent and persistent acute otitis media: new options with familiar antibiotics

Recurrent and persistent acute otitis media (AOM) is a common problem, affecting close to 20% of children in their first years of life. It presents a therapeutic challenge to physicians, particularly as beta-lactamase-producing Haemophilus influenzae, as well as penicillin- and, more recently, macrolide-resistant Streptococcus pneumoniae are often responsible for AOM in these patients. Intramuscular ceftriaxone (50 mg/kg, once daily for 3 days) has been shown to be effective in treating nonresponsive AOM, but there have been relatively few clinical trials exploring oral antibiotic regimens. Higher doses of commonly used antibiotics (amoxicillin-clavulanate ratio, 14:1 ratio and azithromycin 60 mg/kg divided into three equal once daily doses) have demonstrated high rates of clinical success. These studies will be discussed together with a review of the clinical and microbiologic characteristics of this disease. We will also address the impact that the pneumococcal conjugate vaccine may have on the microbiology of recurrent and persistent AOM.

Antimicrobial resistance among pediatric respiratory tract infections: clinical challenges

Considerable development of antimicrobial resistance has occurred in the major pediatric bacterial pathogens, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. However, most of the respiratory infections that children suffer are viral and self-limiting, and only a small percentage of them will develop secondary bacterial infections with the pathogens listed. The challenge for rational antibiotic use is to determine which patients can be treated conservatively and which require antimicrobial intervention to avoid prolonged discomfort or development of permanent sequelae. The basis for rational use of antibiotic in the era of resistance in these major pathogens is to avoid overuse of antimicrobial agents, tailor treatment to identified pathogens as much as possible, and base empiric treatment on the disease being treated and the susceptibility of the probable pathogens at breakpoints based on pharmacokinetic and pharmacodynamic parameters. With appropriate dosing regimens based on these parameters and despite development of resistance, amoxicillin is still one of the most active oral agents against S. pneumoniae and non-beta-lactamase producing strains of H. influenzae, whereas amoxicillin-clavulanate is active against beta-lactamase-producing strains of H. influenzae and M. catarrhalis. Parenteral ceftriaxone and oral and parenteral fluoroquinolones are active against all 3 species, but fluoroquinolones should be used with utmost caution when all other options have been considered because of concerns about toxicity and development of resistance. Introduction of a 7-valent conjugate pneumococcal vaccine in the United States in 2000 reduced the prevalence of invasive pneumococcal disease in children younger than 2 years old, but, as of 2001, had not had a major impact on decreasing antimicrobial resistance.

Microbiology of otitis media in Costa Rican children, 1999 through 2001

BACKGROUND

Because of the increasing number of resistant middle ear pathogens and the impact of the new conjugate Streptococcus pneumoniae vaccine, an active surveillance of the microbiology and susceptibility pattern of middle ear pathogens is required.

OBJECTIVE

To study the microbiology and susceptibility pattern of middle ear pathogens obtained from Costa Rican children with acute otitis media (AOM), recurrent otitis media (ROM) and therapeutic failure otitis media (FOM).

METHODS

Between 1999 and 2001 middle ear fluid (MEF) was collected from 276 Costa Rican patients. S. pneumoniae serotyping and pulsed field gel electrophoresis analysis was done on available strains.

RESULTS

Among the total study population, 102 were AOM patients, 98 were ROM patients and 76 were FOM patients. Overall S. pneumoniae (88 strains) was the most common pathogen isolated followed by Haemophilus influenzae (41 strains) and Streptococcus pyogenes (10 strains). H. influenzae was the most common agent in FOM patients (P = 0.015). Beta-lactamase production was observed in 3 of 41 (7%) H. influenzae strains and 3 of 3 (100%) Moraxella catarrhalis strains. Penicillin-nonsusceptible S. pneumoniae strains were more common in FOM (64%) and ROM (63%) patients than in AOM (42%) patients (P = 0.05). S. pneumoniae serotype 19F was the most prevalent serotype, mainly within one distinct clone.

CONCLUSIONS

Overall S. pneumoniae serotype 19F was the most common isolate from the middle ear fluid of Costa Rican children. Beta-lactamase-negative H. influenzae was the most prevalent in the subpopulation of patients with FOM. S. pyogenes was the third most common isolate and M. catarrhalis was uncommon.

Accurate diagnosis and appropriate treatment of acute bacterial rhinosinusitis: minimizing bacterial resistance

BACKGROUND

Antimicrobial resistance in respiratory pathogens has become a common clinical problem that has serious public health implications. Inappropriate use of antibiotics for the treatment of viral upper respiratory tract infections (URTIs) has contributed to the development of resistant microorganisms. Health care providers can help control the spread of resistance by limiting the use of antimicrobial agents to infections that meet clinical guidelines for a bacterial cause.

OBJECTIVE

This article examines the means of accurately diagnosing and appropriately treating acute bacterial rhinosinusitis (ABRS) in an effort to control increasing levels of resistance.

METHODS

This article discusses current treatment guidelines that provide the evidenced-based rationale for choosing the most appropriate antimicrobial agents for suspected ABRS in adults and children. An evidence-based approach can help minimize the public health threat posed by the continuing increase in microbial resistance.

RESULTS

Although definitive clinical criteria that differentiate between ABRS and viral URTI are lacking, careful evaluation of the duration and severity of symptoms provides a rational basis for diagnosing ABRS in primary care settings.

CONCLUSIONS

Once a diagnosis of ABRS has been made, empiric antibiotic therapy may be justified. When it is, the first-line agent should be the narrowest spectrum antibiotic that would be expected to eradicate the most common causative organisms. The antibiotic selection process should take into account prevailing patterns of resistance and the presence of risk factors for infection with resistant pathogens, as well as published evidence-based guidelines.

Can acute otitis media caused by Haemophilus influenzae be distinguished from that caused by Streptococcus pneumoniae?

BACKGROUND

Previous limited data suggest that acute otitis media (AOM) caused by Streptococcus pneumoniae can present as a more severe disease than that caused by Haemophilus influenzae or Moraxella catarrhalis, as expressed by both tympanic membrane and systemic findings.

OBJECTIVES

To evaluate the severity of disease and impact of various pathogens, age, disease history and previous antibiotic therapy in children with AOM by using a comprehensive clinical/otologic score.

PATIENTS AND METHODS

The study group consisted of 372 children ages 3 to 36 months with AOM seen at the pediatric emergency room during 1996 through 2001. All patients had tympanocentesis and middle ear fluid culture performed at enrollment. Clinical status was determined by a clinical/otologic score evaluating severity (0 = absent to 3 = severe) of tympanic membrane findings (redness and bulging) and patient's fever, irritability and ear tugging. Maximal severity score was 15.

RESULTS

There were 138 (37%) H. influenzae, 76 (21%) S. pneumoniae, 64 (17%) mixed infections (H. influenzae + S. pneumoniae) and 94 (25%) culture-negative cases. The overall clinical/otologic score was higher in culture-positive than in culture-negative patients (9.27 +/- 2.75 vs.8.38 +/- 3.08, P = 0.01). When analyzed by age groups, this difference was significant only for the youngest age group (3 to 6 months, P = 0.05). The severity scores for AOM caused by H. influenzae and S. pneumoniae were significantly higher than in the culture-negative AOM when tympanic membrane redness and bulging were analyzed separately. No differences were recorded in clinical/otologic scores between different pathogens (9.49 +/- 2.86, 9.03 +/- 2.72 and 9.09 +/- 2.54 for H. influenzae, S. pneumoniae and H. influenzae + S. pneumoniae, respectively). The mean clinical/otologic score was higher in culture-positive than in culture-negative patients without relationship to previous antibiotic treatment or number of previous AOM episodes.

CONCLUSIONS

(1) The clinical/otologic score of culture-positive young infants was higher than that of culture-negative infants; (2) the severity of tympanic membrane redness and bulging were the most indicative factors discriminating between a bacterial and nonbacterial etiology of AOM; and (3) the use of a clinical/otologic score could not discriminate among various bacterial etiologies of AOM.

Resistant Haemophilus influenzae in community-acquired respiratory tract infections: a role for cefixime

An increase in Haemophilus influenzae resistance has been documented around the world during the last 30 years. Resistance is due to the production of beta-lactamases, and/or changes to penicillin-binding protein (PBP) targets. The resistance problem has led to the need for new therapeutic strategies aimed at maintaining effective management of both upper respiratory tract infections (URTIs) and lower respiratory tract infections (LRTIs). Among antimicrobial agents tested, third-generation cephalosporins have been shown to possess excellent in vitro activity against beta-lactamase-positive and -negative isolates, corresponding with proven clinical efficacy in a wide range of RTIs. The role of H. influenzae in RTIs is outlined, changing trends in epidemiological surveillance studies monitored and implications for therapy, based upon results of clinical trials discussed.

Microbiologic findings and risk factors for antimicrobial resistance at myringotomy for tympanostomy tube placement--a prospective study of 601 children in Toronto

CONTEXT

There is limited information on the identity and antibiotic susceptibility of bacterial pathogens in children with chronic otitis media whose repeated antibiotic use may place them at increased risk of antibiotic-resistant bacteria.

OBJECTIVE

To determine, at myringotomy for tympanostomy tube placement, (1) the prevalence of bacteria, (2) the extent and patterns of antibiotic resistance, and (3) the risk factors associated with the presence and resistant status of pathogens.

DESIGN

Prospective, multi-site, cohort study.

SETTING AND PATIENTS

Children undergoing myringotomy for tympanostomy tube placement between November 1, 1999 and March 31, 2000 in seven hospitals in Toronto, Ontario, were identified. If fluid was present, aspirates were submitted for bacteriologic testing. A follow-up telephone questionnaire was administered to patient caregivers in order to identify risk factors for the presence of (1) culturable pathogens and (2) resistant pathogens.

MAIN OUTCOME MEASURES

The identification and prevalence of bacteria cultured from the middle ears of subjects, and the degree of nonsusceptibility to commonly prescribed antibiotics.

RESULTS

Among 601 patients (mean age 3.9 years, 60.7% male), both a telephone interview (n=544) and an ear specimen (n=527) were obtained for 478. Pathogens were found in middle ear effusions of 37% of the children in the study; including at least one 'definite' pathogen in 189 children (31.4%), and a further 32 children (5.3%) with at least one 'possible' pathogen. Definite pathogens included Haemophilus influenzae in 17% of the children, followed by Moraxella catarrhalis (9%) and Streptococcus pneumoniae (6%); ampicillin nonsusceptibility was found in 40, 100 and 24%, respectively. Overall, 123 children (20.5%) were found to have definite pathogens with resistance to ampicillin/penicillin, trimethoprim-sulfamethoxazole, or clarithromycin/erythromycin. Patient characteristics included premature birth and/or long length of stay in the nursery (23%), first infection before the age of 6 months (26%), put to bed with a bottle (28%), household smoker (34%), in out-of-home child care (38%), history of eczema, bronchiolitis and/or asthma (39%), and use of pacifiers (40%). Household characteristics were smoking (34%), married/common law parents (85%), and 60% had completed college or university; in 26% both parents were born outside of Canada; 73% of children were Caucasian. Of the 75% who responded to the question regarding income, 42% had household income over $60,000 (CAN). Risk factors for the presence of a pathogen and for a resistant pathogen in multivariate analysis included younger age, lower maternal education, day care centre attendance, no previous adenoidectomy and bilateral, primarily winter infections as well as amoxicillin use in the previous 6 months.

CONCLUSION

Modifiable risk factors for otitis media including household smoking and pacifier use are present in many children undergoing tympanostomy tube placement; child care centre attendees are over-represented. Multiple antibiotic courses were commonly prescribed prior to surgery. H. influenzae and M. catarrhalis are important pathogens and therapy in clinical failures should be directed against them. The 7-valent protein conjugate polysaccharide vaccine (Prevnar) would have covered 73% of the serotypes of S. pneumoniae isolated in this study.

To bridge a quality chasm: connect with the guidelines

ISSUES AND PURPOSE

A wide chasm exists between the care we have and the care we could have. This article will inform nurses about the pediatric quality "chasm" by identifying practice variations from evidence-based guidelines for common childhood conditions.

CONCLUSIONS

Nurses are accountable for providing state-of-the-art, evidence-based care to children. The pediatric quality chasm calls for nurses to stand up and speak out for children, to use and develop tools that activate the best scientific knowledge, and to empower parents to make it happen.

PRACTICE IMPLICATIONS

Advocacy and patient-centered care are nurses' means to partner with parents and collaborate with colleagues to connect with the guidelines and bridge the quality chasm.

Bacterial eradication in the treatment of otitis media

Drugs differ in their ability to eradicate various pathogens from the middle-ear cavity during acute otitis media (AOM), and these differences clearly affect clinical outcome. Outcome is derived from differences in the association between concentrations of the drugs at the site of infection and the antimicrobial effect (termed pharmacodynamics). These differences are even more marked in the present era of antimicrobial resistance. However, since AOM is a self-limiting disease in most cases, difference in clinical outcome is more difficult to ascertain than that of bacteriological outcome, which is measured within 3-5 days. A favourable clinical outcome regardless of the bacteriological effect of the drug can result in false optimism when less-effective antibiotic drugs are used. Inappropriate study design and manipulation of clinical results add to this confusion. In this review we attempt to highlight the evidence regarding bacteriological response to antibiotics in AOM and to draw attention to potential flaws that may mislead clinicians.

Treatment of acute otitis media consensus recommendations

The objective of this paper is to provide consensus recommendations for the management of acute otitis media (AOM) that pediatricians can incorporate into their daily practices. These recommendations were developed during a roundtable meeting that convened clinicians versed in the management of AOM. This meeting was sponsored by an educational grant from SmithKline Beecham Pharmaceuticals. In addition, clinical studies on AOM identified via MEDLINE search were considered in the development of these recommendations. The Drug-Resistant Streptococcus pneumoniae Therapeutic Working Group guidelines for the management of AOM are reviewed in detail. All of the articles identified from the data sources were evaluated and all information deemed relevant was included in this review. AOM is one of the most common infectious diseases affecting infants and children and one of the leading causes of office visits and antibiotic prescriptions for this population. The incidence of AOM has increased during the past 25 years, probably the result of an increased utilization of day care facilities in the United States. The predominant pathogens in AOM include S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The high prevalence of drug-resistant S. pneumoniae and beta-lactamase-producing organisms presents a clinical challenge for practitioners in the selection of empiric antimicrobial therapy. Pharmacokinetic/pharmacodynamic principles should be considered in addition to minimum inhibitory concentrations in selecting antibiotics for AOM. Amoxicillin at conventional or high doses (80-90 mg/kg/day) remains an appropriate choice for first-line therapy for AOM. For patients in whom amoxicillin is unsuccessful, second-line therapy should have demonstrated activity against penicillin-resistant S. pneumoniae as well as beta-lactamase-producing pathogens. Appropriate options for second-line therapy include high-dose amoxicillin/clavulanate (90 mg/kg/day based on the amoxicillin component) and ceftriaxone. Cefuroxime has been suggested as a second-line agent in the past, but recent surveillance data suggest it may no longer be active against penicillin-resistant strains of S. pneumoniae. Tympanocentesis is useful for identifying the causative pathogen, and it may be beneficial for patients who have failed multiple courses of antibiotics. The pneumococcal conjugate vaccine recently was approved for use in children and should be administered to all children less than 2 years old and those at risk for recurrent AOM (e.g., day care attendance, siblings with a history of recurrent AOM). Consensus recommendations are provided for the management of AOM, with a focus on antimicrobial therapy. The current challenges in the management of AOM include the need for an increased understanding of epidemiology, increasing resistance among common middle ear pathogens, use of pharmacokinetic/pharmacodynamic principles in designing treatment strategies, and understanding the potential impact of the pneumococcal conjugate vaccine.

Diagnosis and management of acute otitis media in the urgent care setting

The prevalence of otitis media is increasing, which affects health care resource utilization across all segments, including the urgent care setting. One of the greatest challenges in the management of acute otitis media (AOM) is the effective treatment of cases caused by pathogens that are resistant to commonly used antibiotics. Whereas the production of beta-lactamases among strains of Haemophilus influenzae and Moraxella catarrhalis is an important consideration for antimicrobial therapy, the high prevalence of resistance to penicillin and other classes of antibiotics among strains of Streptococcus pneumoniae represents a greater clinical concern. The Centers for Disease Control and Prevention (CDC) recently convened the Drug Resistant S. pneumoniae Therapeutic Working Group to develop evidence-based recommendations for the treatment of AOM in an era of prevalent resistance. The recommendations from this group included amoxicillin as the preferred first-line drug because of the demonstrated activity against penicillin-intermediate and -resistant strains of S. pneumoniae, using higher dosages of up to 90 mg/kg per day in certain settings. For patients in whom initial treatment is unsuccessful after 3 days, the recommended agents included high-dose amoxicillin-clavulanate (for activity against beta-lactamase-producing pathogens), clindamycin, cefuroxime axetil, or 1 to 3 doses of intramuscular ceftriaxone. The principles set forth in these guidelines can assist the therapeutic decisionmaking process for practitioners in the urgent care setting.

Acute upper airway infections

Upper respiratory tract infections are common and important. Although rarely fatal, they are a source of significant morbidity and carry a considerable economic burden. Numerous therapies for the common cold have no effect on symptoms or outcome. Complications such as cough are not improved by over-the-counter preparations, while labelling cough alone as a symptom of asthma may result in unnecessary use of inhaled steroid treatment. Clinical presentation of sore throat does not accurately predict whether the infection is viral or bacterial, while throat culture and rapid antigen tests do not significantly change prescribing practice. Antibiotics have only a limited place in the management of recurrent sore throat due to group A beta-haemolytic streptococcal infection. Routine use of antibiotics in upper respiratory infection enhances parent belief in their effectiveness and increases the likelihood of future consultation in primary care for minor self-limiting illness. Respiratory viruses play a major role in the aetiology of acute otitis media (AOM); prevention includes the use of influenza or RSV vaccination, in addition to reducing other risk factors such as early exposure to respiratory viruses in day-care settings and to environmental tobacco smoke. The use of ventilation tubes (grommets) in secretory otitis media (SOM) remains controversial with conflicting data on developmental outcome and quality of life in young children. New conjugate pneumococcal vaccines appear safe in young children and prevent 6-7% of clinically diagnosed AOM.

Upper respiratory tract infections

Acute respiratory infections accounts for 20-40% of outpatient and 12-35% of inpatient attendance in a general hospital. Upper respiratory tract infections including nasopharyngitis, pharyngitis, tonsillitis and otitis media constitute 87.5% of the total episodes of respiratory infections. The vast majority of acute upper respiratory tract infections are caused by viruses. Common cold is caused by viruses in most circumstances and does not require antimicrobial agent unless it is complicated by acute otitis media with effusion, tonsillitis, sinusitis, and lower respiratory tract infection. Sinusitis is commonly associated with common cold. Most instances of rhinosinusitis are viral and therefore, resolve spontaneously without antimicrobial therapy. The most common bacterial agents causing sinusitis are S. pneumoniae, H. influenzae, M. catarrhalis, S. aureus and S. pyogenes. Amoxycillin is antibacterial of choice. The alternative drugs are cefaclor or cephalexin. The latter becomes first line if sinusitis is recurrent or chronic. Acute pharyngitis is commonly caused by viruses and does not need antibiotics. About 15% of the episodes may be due to Group A beta hemolytic streptococcus (GABS). Early initiation of antibiotics in pharyngitis due to GABS can prevent complications such as acute rheumatic fever. The drug of choice is penicillin for 10-14 days. The alternative medications include oral cephalosporins (cefaclor, cephalexin), amoxicillin or macrolides.

Bacteriologic and clinical efficacy of high dose amoxicillin/clavulanate in children with acute otitis media

OBJECTIVES

To determine the bacteriologic and clinical efficacy of high dose amoxicillin/clavulanate (90/6.4 mg/kg/day) against common bacterial pathogens causing acute otitis media (AOM), including penicillin-resistant Streptococcus pneumoniae (PRSP).

METHODS

In this open label multicenter study, 521 infants and children with AOM [mean age, 18.6 months; age < 24 months, n = 375 (72%)] were treated with amoxicillin/clavulanate 90/6.4 mg/kg/day in two divided doses for 10 days. Bilateral otitis media, previous episodes of AOM, antibiotic treatment within 3 months and day-care attendance were recorded in 60.1, 35.7, 50.2 and 38.2% of the children, respectively. Tympanocentesis was performed before the first dose and repeated on Days 4 to 6 for all children with S. pneumoniae at 22 centers and for all children with any pathogen at 3 centers. Clinical response was assessed at end of therapy.

RESULTS

Pathogens were isolated from 355 (68%) of 521 enrolled children; 180 children underwent repeat tympanocentesis and were bacteriologically evaluable. Baseline pathogens were S. pneumoniae (n = 122 enrolled/93 bacteriologically evaluable), Haemophilus influenzae (n = 160/51), both (n = 37/32) and others (n = 36/4). Pathogens were eradicated from 172 (96%) of 180 bacteriologically evaluable children. Overall 122 (98%) of 125 isolates of S. pneumoniae were eradicated, including 31 (91%) of 34 PRSP isolates (penicillin MICs 2 to 4 micrograms/ml). Seventy-eight (94%) of 83 isolates of H. influenzae were eradicated. Symptoms and otoscopic signs of acute inflammation were completely resolved or improved on Days 12 to 15 in 263 (89%) of 295 clinically evaluable children with bacteriologically documented AOM.

CONCLUSIONS

On the basis of bacteriologic outcome on Days 4 to 6 and clinical outcome on Days 12 to 15, we found that high dose amoxicillin/clavulanate (90/6.4 mg/kg/day) was highly efficacious in children with AOM, including those most likely to fail treatment, namely children < 24 months of age and those with infectious caused by PRSP.

Bacterial and viral etiology of acute otitis media in Chilean children

BACKGROUND

Acute otitis media (AOM) is a main cause for antimicrobial prescription in Latin America. Pathogen diversity in different geographic regions underscores the need for updated knowledge on AOM microbiology.

AIM

To prospectively determine the role of bacteria and viruses in Chilean children with AOM.

METHODS

Between July, 1998, and June, 1999, children >3 months with a presumptive diagnosis of AOM were referred to the study ear, nose and throat physician. Middle ear fluid and nasopharyngeal aspirates were obtained from children with confirmed AOM and processed for common bacteria, Mycoplasma pneumoniae, Chlamydia pneumoniae and viruses. Antimicrobial susceptibility patterns and serotypes of Streptococcus pneumoniae strains were determined.

RESULTS

An ear, nose and throat physician confirmed diagnoses for 222 (42%) of 529 children referred with diagnosis of AOM, and 170 children met eligibility criteria for the study. One or more pathogens were detected in 140 of 170 (82%) children. Predominant bacteria were S. pneumoniae (37%), Haemophilus influenzae (24%) and Streptococcus pyogenes (13%). M. catarrhalis was detected in 2 children, C. pneumoniae was found in 1 and M. pneumoniae was not detected. Viruses were detected in 22 children (13%) from nasopharyngeal aspirates, and in 6 of them the same virus was detected in middle ear fluid. Penicillin-resistant (intermediate and high) S. pneumoniae represented 40% of isolates and 10% of H. influenzae were beta-lactamase producers. All 10 penicillin-resistant S. pneumoniae strains were resistant to cefuroxime. Eighteen S. pneumoniae serotypes were detected and 19F was associated with high level penicillin resistance.

CONCLUSION

This study can impact local management of AOM, and it should encourage continuous surveillance of AOM microbiology in Chile and other developing countries.

Measuring and interpreting associations between antibiotic use and penicillin resistance in Streptococcus pneumoniae

Studies of the relationship between antibiotic use and resistance in pneumococci have produced conflicting results, reflecting differences in study design, setting, and measures of association used. Mathematical models of pneumococcal transmission dynamics provide a framework for interpreting and reconciling these studies. The model predicts, and the review of published studies confirms, that treatment often has little effect in increasing an individual's absolute risk of carrying/being infected by penicillin-resistant Streptococcus pneumoniae (PRSP). However, treatment substantially increases a patient's risk of carriage of/infection by PRSP relative to that of penicillin-susceptible S. pneumoniae (PSSP). The appropriate measure of association depends on the question of interest. Antibiotic use can substantially increase the prevalence of risk in the community as a whole, even when there is a small or nonexistent effect of treatment on the absolute risk that a treated individual will carry a resistant organism. Recommendations for the design and analysis of future studies of antibiotic treatment and pneumococcal resistance are proposed.

Influence of Pharmacokinetic and Pharmacodynamic Principles on Antibiotic Selection

When evaluating the efficacy of antibiotics for the treatment of respiratory tract infections, such as community acquired pneumonia and acute exacerbations of chronic bronchitis, assessment of clinical cure may not be the most relevant parameter, as it may not be related to microbiological eradication or to the minimum inhibitory concentration (MIC) of the infecting pathogen. It is more relevant to study the efficacy of the antibiotic in eradicating the bacterial pathogen, because this is frequently related to both the MIC of the pathogen and the antibiotic dosage regimen. Pharmacodynamics correlates the concentration of antibiotic in the blood or at the infection site with its biological effect against the organism (bacteriological eradication). For beta-lactams, the pharmacodynamic parameter that best correlates with eradication is time (T) above MIC (T > MIC); for aminoglycosides and fluoroquinolones, it is the area under the curve at 24 hours (AUC(24))-to-MIC ratio (AUC(24)/MIC). Knowledge of pharmacodynamics allows optimum use of antibiotics; in vitro models, animal models, and retrospective and prospective clinical trials have shown that the use of such knowledge optimizes bacteriological eradication and enhances patient outcome. In the future, pharmacodynamic studies will be used not only to assess optimal ways for antibiotics to eradicate resistant pathogens, but also to investigate the ability of antibiotics to prevent the development of resistance on therapy and to eradicate pathogens from colonizing sites.