The hidden impact of antibacterial resistance in respiratory tract infection. Clinical failures: the tip of the iceberg?

Efficacy of high doses of penicillin versus amoxicillin in the treatment of uncomplicated community acquired pneumonia in adults. A non-inferiority controlled clinical trial

Introduction

Community-acquired pneumonia (CAP) is treated with penicillin in some northern European countries.

Objectives

To evaluate whether high-dose penicillin V is as effective as high-dose amoxicillin for the treatment of non-severe CAP.

Design

Multicentre, parallel, double-blind, controlled, randomized clinical trial.

Setting

31 primary care centers in Spain.

Participants

Patients from 18 to 75 years of age with no significant associated comorbidity and with symptoms of lower respiratory tract infection and radiological confirmation of CAP were randomized to receive either penicillin V 1.6 million units, or amoxicillin 1000 mg three times per day for 10 days.

Main measurements

The main outcome was clinical cure at 14 days, and the primary hypothesis was that penicillin V would be non-inferior to amoxicillin with regard to this outcome, with a margin of 15% for the difference in proportions. EudraCT register 2012-003511-63.

Results

A total of 43 subjects (amoxicillin: 28; penicillin: 15) were randomized. Clinical cure was observed in 10 (90.9%) patients assigned to penicillin and in 25 (100%) patients assigned to amoxicillin with a difference of −9.1% (95% CI, −41.3% to 6.4%; p = .951) for non-inferiority. In the intention-to-treat analysis, amoxicillin was found to be 28.6% superior to penicillin (95% CI, 7.3–58.1%; p = .009 for superiority). The number of adverse events was similar in both groups.

Conclusions

There was a trend favoring high-dose amoxicillin versus high-dose penicillin in adults with uncomplicated CAP. The main limitation of this trial was the low statistical power due to the low number of patients included.

Efficacy of high doses of oral penicillin versus amoxicillin in the treatment of adults with non-severe pneumonia attended in the community: study protocol for a randomised controlled trial

Background

Streptococcus pneumoniae is the bacterial agent which most frequently causes pneumonia. In some Scandinavian countries, this infection is treated with penicillin V since the resistances of pneumococci to this antibiotic are low. Four reasons justify the undertaking of this study; firstly, the cut-off points which determine whether a pneumococcus is susceptible or resistant to penicillin have changed in 2008 and according to some studies published recently the pneumococcal resistances to penicillin in Spain have fallen drastically, with only 0.9% of the strains being resistant to oral penicillin (minimum inhibitory concentration>2 μg/ml); secondly, there is no correlation between pneumococcal infection by a strain resistant to penicillin and therapeutic failure in pneumonia; thirdly, the use of narrow-spectrum antibiotics is urgently needed because of the dearth of new antimicrobials and the link observed between consumption of broad-spectrum antibiotics and emergence and spread of antibacterial resistance; and fourthly, no clinical study comparing amoxicillin and penicillin V in pneumonia in adults has been published. Our aim is to determine whether high-dose penicillin V is as effective as high-dose amoxicillin for the treatment of uncomplicated community-acquired pneumonia.

Methods

We will perform a parallel group, randomised, double-blind, trial in primary healthcare centres in Spain. Patients aged 18 to 65 without significant associated comorbidity attending the physician with signs and symptoms of lower respiratory tract infection and radiological confirmation of the diagnosis of pneumonia will be randomly assigned to either penicillin V 1.6 million units thrice-daily during 10 days or amoxicillin 1,000 mg thrice-daily during 10 days. The main outcome will be clinical cure at 14 days, defined as absence of fever, resolution or improvement of cough, improvement of general wellbeing and resolution or reduction of crackles indicating that no other antimicrobial treatment will be necessary. Any clinical result other than the anterior will be considered as treatment failure. A total of 210 patients will be recruited to detect a non-inferiority margin of 15% between the two treatments with a minimum power of 80% considering an alpha error of 2.5% for a unilateral hypothesis and maximum possible losses of 15%.

Discussion

This pragmatic trial addresses the long-standing hypothesis that the administration of high doses of a narrow-spectrum antibiotic (penicillin V) in patients with non-severe pneumonia attended in the community is not less effective than high doses of amoxicillin (treatment currently recommended) in patients under the age of 65 years.

Trial registration

EudraCT number 2012-003511-63.

Trends in antibacterial resistance among Streptococcus pneumoniae isolated in the USA: update from PROTEKT US Years 1-4

Background

The increasing prevalence of resistance to established antibiotics among key bacterial respiratory tract pathogens, such as Streptococcus pneumoniae, is a major healthcare problem in the USA. The PROTEKT US study is a longitudinal surveillance study designed to monitor the susceptibility of key respiratory tract pathogens in the USA to a range of commonly used antimicrobials. Here, we assess the geographic and temporal trends in antibacterial resistance of S. pneumoniae isolates from patients with community-acquired respiratory tract infections collected between Year 1 (2000–2001) and Year 4 (2003–2004) of PROTEKT US.

Methods

Antibacterial minimum inhibitory concentrations were determined centrally using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method; susceptibility was defined according to CLSI interpretive criteria. Macrolide resistance genotypes were determined by polymerase chain reaction.

Results

A total of 39,495 S. pneumoniae isolates were collected during 2000–2004. The percentage of isolates resistant to erythromycin, penicillin, levofloxacin, and telithromycin were 29.3%, 21.2%, 0.9%, and 0.02%, respectively, over the 4 years, with marked regional variability. The proportion of isolates exhibiting multidrug resistance (includes isolates known as penicillin-resistant S. pneumoniae and isolates resistant to ≥ 2 of the following antibiotics: penicillin; second-generation cephalosporins, e.g. cefuroxime; macrolides; tetracyclines; and trimethoprim-sulfamethoxazole) remained stable at ~30% over the study period. Overall mef(A) was the most common macrolide resistance mechanism. The proportion of mef(A) isolates decreased from 68.8% to 62.3% between Year 1 and Year 4, while the percentage of isolates carrying both erm(B) and mef(A) increased from 9.7% to 18.4%. Over 99% of the erm(B)+mef(A)-positive isolates collected over Years 1–4 exhibited multidrug resistance. Higher than previously reported levels of macrolide resistance were found for mef(A)-positive isolates.

Conclusion

Over the first 4 years of PROTEKT US, penicillin and erythromycin resistance among pneumococcal isolates has remained high. Although macrolide resistance rates have stabilized, the prevalence of clonal isolates, with a combined erm(B) and mef(A) genotype together with high-level macrolide and multidrug resistance, is increasing, and their spread may have serious health implications. Telithromycin and levofloxacin both showed potent in vitro activity against S. pneumoniae isolates irrespective of macrolide resistance genotype.

Azithromycin extended release: a review of its use in the treatment of acute bacterial sinusitis and community-acquired pneumonia in the US

Azithromycin is a macrolide antibacterial agent. The novel microspheres oral extended-release formulation (Zmax) is the first antibacterial drug approved in the US for administration as a single dose in adult patients with mild to moderate acute bacterial sinusitis (ABS) or community-acquired pneumonia (CAP). It has a broad spectrum of in vitro antibacterial activity against Gram-positive, Gram-negative and atypical pathogens that cause ABS and CAP infections (including Streptococcus pneumoniae), and achieves good tissue penetration. Azithromycin extended release is an effective and generally well tolerated treatment in patients with ABS or CAP. The clinical cure rates of a single 2.0 g dose of azithromycin extended release were noninferior to those obtained with a 10-day regimen of levofloxacin in patients with ABS, and with 7-day regimens of clarithromycin extended release or levofloxacin in patients with CAP. With a pharmacodynamic and pharmacokinetic profile well suited to administration as a single-dose regimen that may offer the advantage of improved compliance and convenience compared with once-daily longer-course regimens, azithromycin extended release is a new option in the empirical treatment of adult patients with mild or moderate ABS or CAP in the US.

Community-acquired pneumonia: defining quality care

BACKGROUND

Community-acquired pneumonia (CAP) is one of 3 initial conditions for which the Joint Commission for Accreditation of Healthcare Organizations and the Centers for Medicare & Medicaid Services have defined quality measures. Eight "core measures" of pneumonia care have been targeted for reporting by U.S. hospitals to facilitate performance monitoring.

METHODS

A review of the literature supporting the core measures was performed.

RESULTS

Indicators encouraging influenza vaccination and appropriate antibiotic selection had the most robust evidence. Rapid delivery of antibiotics also showed significant reduction in mortality, though the actual timing (4 versus 8 hours) varied between studies. Other measures, such as performance of blood cultures, pneumococcal vaccination, smoking cessation, and oxygenation assessment, demonstrated less obvious clinical benefit.

CONCLUSIONS

There is inherent value in setting standards of care for high-impact conditions such as CAP, but these standards should be chosen on the basis of high-quality research. Public reporting of the current measures is problematic, as it implies they represent best practices for CAP despite relatively weak evidence.

Penicillin resistance and serotyping of Streptococcus pneumoniae in Latin America

Streptococcus pneumoniae (Strep. pneumoniae) is the main cause of bacterial pneumonia in children less than 5 years of age, with high mortality rates in developing countries. In 1993, the Regional System for Vaccines Group (SIREVA) of the pan-American Health Organisation (PAHO) began a study involving six Latin American countries to identify serotypes and their representativity in the new conjugated vaccines, and to determine the degree of resistance to penicillin. Serotypes 14 (highest resistance level), 5, 1, 6A/B, 23F, 7F, 9V, 19F, 18C, 19A, 9N, were prevalent in the region, with some differences among countries. Although resistance to penicillin ranged from 2% (Brazil) to 21.1% (Mexico), studies have shown that pneumonia caused by Strep. pneumoniae with diminished sensitivity to penillin can be treated with this antibiotic. Only 58% of the serotypes isolated in the region studied were represented in the seven-valent vaccine. Continual surveillance is essential to determine which formulation of conjugated vaccine will be suitable for use in Latin America.

Telithromycin in the treatment of pneumococcal community-acquired respiratory tract infections: a review

OBJECTIVES

A pooled analysis of 14 Phase III studies was performed to establish the clinical and bacteriologic efficacy of telithromycin 800 mg once daily in the treatment of pneumococcal community-acquired respiratory tract infections (RTIs).

METHODS

Data were examined from 5534 adult/adolescent patients with community-acquired pneumonia (CAP), acute exacerbations of chronic bronchitis (AECB), or acute bacterial sinusitis, who had received telithromycin for 5-10 days or a comparator antibacterial.

RESULTS

Streptococcus pneumoniae was identified in 704/2060 (34.2%) bacteriologically evaluable patients. The respective per-protocol clinical cure rates for telithromycin and comparators were 94.3% and 90.0% (CAP); 81.5% and 78.9% (AECB); 90.1% and 87.5% (acute sinusitis); 92.7% and 87.6% (all indications). Clinical cure rates were 28/34 (82.4%) and 5/7, respectively, for penicillin-resistant infections, and 44/52 (84.6%) and 11/14, respectively, for erythromycin-resistant infections. Of 82 patients with pneumococcal bacteremia, 74 (90.2%) were clinically cured after telithromycin treatment, including 5/7 and 8/10 with penicillin- or erythromycin-resistant strains, respectively. Adverse events considered possibly related to study medication were reported by 1071/4045 (26.5%) telithromycin and 505/1715 (29.4%) comparator recipients. These events were generally of mild/moderate severity, and mainly gastrointestinal in nature.

CONCLUSIONS

As S. pneumoniae is the leading bacterial cause of community-acquired RTIs, and antibacterial resistance is increasing among this species, these findings support the use of telithromycin as first-line therapy in this setting.

Emergence and spread of Streptococcus pneumoniae with erm(B) and mef(A) resistance

Streptococcus pneumoniae isolates (N = 31,001) were collected from patients with community-acquired respiratory tract infections during the PROTEKT US surveillance study (2000–2003). While the macrolide (erythromycin) resistance rate remained stable at ≈29%, the prevalence of resistant isolates containing both erm(B) and mef(A) increased from 9.7% in year 1 to 16.4% in year 3, with substantial regional variability. Almost all (99.2%) dual erm(B)+mef(A) macrolide-resistant isolates exhibited multidrug resistance, whereas 98.6% and 99.0% were levofloxacin- and telithromycin-susceptible, respectively. These strains were most commonly isolated from the ear or middle-ear fluid of children. Of 152 representative erm(B)+mef(A) isolates, >90% were clonally related to the multidrug-resistant international Taiwan^19F-14 clonal complex 271 (CC271). Of 366 erm(B)+mef(A) isolates from the PROTEKT global study (1999–2003), 83.3% were CC271, with the highest prevalence seen in South Africa, South Korea, and the United States. This study confirms the increasing global emergence and rapidly increasing US prevalence of this multidrug-resistant pneumococcal clone.

Amoxicillin/clavulanic acid 2000mg/125mg extended release (XR): a review of its use in the treatment of respiratory tract infections in adults

Amoxicillin/clavulanic acid 2000mg/125mg extended release (Augmentin XR), referred to herein as amoxicillin/clavulanic acid XR, is a pharmacokinetically enhanced formulation designed to provide more effective therapy in adults and adolescents than conventional formulations against community-acquired respiratory tract pathogens, particularly Streptococcus pneumoniae, with reduced susceptibility to amoxicillin. Amoxicillin/clavulanic acid XR maintains plasma amoxicillin concentrations above 4 microg/mL for a mean of 49% of the dosing interval indicating that it would be highly effective against S. pneumoniae strains with minimum inhibitory concentrations (MICs) above the National Committee for Clinical Laboratory Standard's amoxicillin +/- clavulanic acid susceptibility breakpoint of < or =2 microg/mL. Amoxicillin/clavulanic acid XR is at least as effective as conventional amoxicillin/clavulanic acid formulations, levofloxacin and clarithromycin in treating community-acquired pneumonia, acute bacterial sinusitis or acute exacerbations of chronic bronchitis, and has a tolerability profile comparable to that of conventional amoxicillin/clavulanic acid formulations. While the incidence of amoxicillin- or multidrug-resistant S. pneumoniae is not currently sufficient in most regions to warrant the routine empirical use of amoxicillin/clavulanic acid XR, the drug would be extremely useful in those regions with a high incidence of resistant pathogens or in selected patients (i.e. those with S. pneumoniae isolates having amoxicillin MICs > or =2 microg/mL but < or =4 microg/mL).

Increasing prevalence of multidrug-resistant Streptococcus pneumoniae in the United States over a 10-year period: Alexander Project

The Alexander Project is a global surveillance study conducted from 1992 to 2001. Minimum inhibitory concentrations and percent resistance to a panel of antimicrobial agents were determined according to National Committee for Clinical Laboratory Standards methodology. Resistance to penicillin (PEN-R) and erythromycin (ERY-R) have increased in the period 1992-2001 by 3.9 and 4.5 times to 20.7% and 27.9%, respectively. Joint PEN-ERY-R has increased 4.9 times, up to 15.3%. In 1992, 57.1% of all PEN-R isolates were also ERY-R, whereas in 2001, 75.8% were ERY-R. Resistance to only 1 antibiotic increased slightly, from 8% in 1992 to 12% in 2001, whereas resistance to more than 1 antibiotic increased 4.3 times, from 6.4% in 1992 to 27.8% of all strains in 2001. Multidrug-resistant pneumococci are an increasingly common finding in the United States. Three of four PEN-R isolates are also multiresistant. The rate of growth of multidrug resistance is higher than that of single antibiotic resistance.

Role of beta-lactam agents in the treatment of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a common illness associated with high rates of morbidity and mortality worldwide. The beta-lactam antibacterial agents have been the mainstay of therapy for CAP for over four decades and remain as first-line therapy. However, the impact of the substantial prevalence of resistance seen among the common respiratory pathogens, particularly penicillin and macrolide resistance among Streptococcus pneumoniae, is now an area for concern. CAP treatment guidelines often recommend the use of a macrolide or fluoroquinolone in conjunction with, or as an alternative to, beta-lactam agents, but whether this is necessary is uncertain. This review outlines the historical use of beta-lactam antibacterial agents in the treatment of CAP along with their ongoing therapeutic utility.

Spanish primary healthcare physicians' knowledge of resistance of respiratory germs and antimicrobial treatment in acute bronchitis

OBJECTIVES

To determine what Spanish primary healthcare physicians consider the rates of pneumococcal resistance to be, the type of antimicrobial treatment they would prescribe on suspicion of high resistance and ascertain in which cases of acute bronchitis these physicians would initiate antibiotic treatment.

METHODS

A cross-sectional, observational study was performed with a questionnaire distributed to 1368 physicians on their opinion on the degree of resistance of pneumococci to penicillins and macrolides in Spain. They were also asked which treatment they would recommend in penicillin-resistant pneumococcal infection and to indicate their degree of agreement regarding the use of antibiotics in different clinical situations of acute bronchitis.

RESULTS

843 physicians completed and returned the questionnaire, a response rate of 59.1%. Of the 750 physicians who answered the question concerning pneumococcal resistance, 312 stated resistance to be >30% (41.6%) while only 90 felt it to be <15% (12%). 153 physicians reported resistance to macrolides to be >30% (23%). In cases with suspicion of penicillin-resistant pneumococci, the clinicians stated they would prescribe quinolones (321, 40.3%) and macrolides (251, 31.5%). Of the 784 physicians who answered the questions on bronchitis, 662 preferred antibiotic therapy in acute bronchitis with purulent sputum (84.6%), 610 on uncertain diagnosis (77.8%), 569 in patients with fever over 38 degrees C (72.6%) and 210 on patient request (26.8%).

CONCLUSION

Primary healthcare physicians in Spain are more concerned about pneumococcal resistance to penicillins than to macrolides although 35% of the strains isolated are resistant to the latter while only 10% are resistant to aminopenicillins. Furthermore, many physicians believe macrolides to be effective against pneumococcal infections. Despite their lack of efficacy in the treatment of acute bronchitis, many physicians prescribe antibiotics, mainly in cases with purulent expectoration, thus justifying the high consumption of antimicrobial agents in this disease.

Building in efficacy: developing solutions to combat drug-resistant S. pneumoniae

The development of our understanding of the pharmacokinetic (PK) and pharmacodynamic (PD) principles that determine antimicrobial efficacy has advanced substantially over the last 10 years. We are now in a position to use PK/PD principles to set targets for antimicrobial design and optimisation so that we can predict eradication of specific pathogens or resistant variants when agents are used clinically. Optimisation of PK/PD parameters to enable the treatment of resistant pathogens with oral agents may not be possible with many current agents, such as some cephalosporins, macrolides and fluoroquinolones. Aminopenicillins, however, such as amoxicillin, have linear PK and have a good safety profile even at high doses. The new pharmacokinetically enhanced oral formulation of amoxicillin/clavulanate, 2000/125 mg twice daily, was designed using PK/PD principles to be able to eradicate Streptococcus pneumoniae with amoxicillin MICs of up to and including 4 mg/L, which includes most penicillin-resistant isolates. For amoxicillin and amoxicillin/clavulanate, a time above MIC (T > MIC) of 35-40% of the dosing interval (based on blood levels) is predictive of high bacteriological efficacy. This target was met by the design of a unique bilayer tablet incorporating 437.5 mg of sustained-release sodium amoxicillin in one layer plus 562.5 mg of immediate-release amoxicillin trihydrate and 62.5 mg of clavulanate potassium in the second layer, with two tablets administered for each dose. This unique design extends the bacterial killing time by increasing the T > MIC to 49% of the dosing interval against pathogens with MICs of 4 mg/L, and 60% of the dosing interval against pathogens with MICs of 2 mg/L. Based on these results, this new amoxicillin/clavulanate formulation should be highly effective in treating respiratory tract infections due to drug-resistant S. pneumoniae as well as beta-lactamase-producing pathogens, such as Haemophilus influenzae and Moraxella catarrhalis.

Performance in practice: bacteriological efficacy in patients with drug-resistant S. pneumoniae

Using pharmacokinetic/pharmacodynamic principles, pharmacokinetically enhanced amoxicillin/clavulanate 2000/125 mg twice daily was designed to provide adequate levels of amoxicillin over the 12-h dosing interval to eradicate penicillin-resistant Streptococcus pneumoniae (PRSP, penicillin MICs > or = 2 mg/L) with amoxicillin MICs of at least 4 mg/L. The clinical efficacy of amoxicillin/clavulanate 2000/125 mg was evaluated in patients with respiratory tract infections caused by S. pneumoniae, including isolates with elevated penicillin (2-8 mg/L) MICs. Data from 10 clinical studies were combined: seven randomised (1:1), double-blind, controlled trials (efficacy intent-to-treat [ITT]N = 3376): amoxicillin/clavulanate 2000/125 mg twice daily vs. levofloxacin 500 mg once daily in acute bacterial sinusitis (ABS); levofloxacin 500 mg once daily in acute exacerbations of chronic bronchitis (AECB); clarithromycin 500 mg twice daily in AECB; amoxicillin/clavulanate 875/125 mg twice daily/three times daily and 1000/125 mg three times daily in community-acquired pneumonia (CAP) and three noncomparative studies (efficacy ITT N = 3024): two in ABS, one in CAP. The bacteriological per-protocol (PP) population at follow up (days 14-39) comprised 1295 patients for amoxicillin/clavulanate 2000/125 mg and 241 for comparators. With amoxicillin/clavulanate 2000/125 mg at follow-up, outcome was successful (clinical success and eradication/presumed eradication) in 85/90 (94.4%) patients with S. pneumoniae in comparative studies and 421/445 (94.6%) in noncomparative studies, and with comparators 58/70 (82.9%) were successes. In the amoxicillin/clavulanate 2000/125 mg group at follow up, 52/552 S. pneumoniae isolates were resistant to penicillin. At follow up, 50/52 (96.2%) patients with PRSP were successes, including 6/7 with amoxicillin MICs of 4 mg/L and 7/8 with amoxicillin MICs of 8 mg/L. Success rates for amoxicillin/clavulanate 2000/125 mg against PRSP were similar for CAP (96.0%[24/25]), AECB (100%[3/3]) and ABS (95.8%[23/24]). There were six PRSP isolates in the comparator group (two isolates were from one patient), and three of five patients in this group were successes. In conclusion, amoxicillin/clavulanate 2000/125 mg demonstrated combined clinical/bacteriological success against 50/52 patients with PRSP, including 13/15 strains with amoxicillin MICs of 4-8 mg/L. These results for the pharmacokinetic-enhanced formulation of amoxicillin/clavulanate 2000/125 mg are in line with the high efficacy against PRSP predicted using pharmacokinetic/pharmacodynamic parameters.

Clinical relevance of antimicrobial resistance in the management of pneumococcal community-acquired pneumonia

Streptococcus pneumoniae remains the most common bacterial cause of community-acquired pneumonia, and these infections are associated with significant morbidity and mortality worldwide. A major concern is the increasing incidence of antibiotic resistance among pneumococcal isolates, which, in the case of certain of the antibiotic classes, has been associated with treatment failure. Yet despite multiple reports of infections with penicillin-resistant pneumococcal isolates, no cases of bacteriologic failure have been documented with the use of penicillin or ampicillin in the treatment of pneumonia caused by penicillin-resistant pneumococci. Current prevalence and levels of penicillin resistance among pneumococal isolates in most areas of the world do not indicate a need for substantial treatment changes with regard to the use of the penicillins. For infections with penicillin-sensitive strains, penicillin or an aminopenicillin in a standard dosage will still be effective for treatment. In the cases of strains with intermediate resistance, beta-lactam agents are still considered appropriate treatment, although higher dosages are recommended. Infections with isolates of high-level penicillin resistance should be treated with alternative agents such as the third-generation cephalosporins or the new antipneumococcal fluoroquinolones. In the case of the cephalosporins, pharmacodynamic/pharmacokinetic parameters help predict which of those agents are likely to be successful, and the less active agents should not be used. Debate continues in the literature with regard to the impact of macrolide resistance on the outcome of pneumococcal pneumonia, with some investigators providing evidence of an "in vivo-in vitro paradox," referring to discordance between reported in vitro resistance and clinical success of macrolides/azalide in vivo. However, several cases of macrolide/azalide treatment failure have been documented, and many clinicians recommend that these agents not be used on their own in areas with a high prevalence and levels of macrolide/azalide resistance. However, evidence is emerging to show beneficial effects on outcome with combination therapy, especially that of a beta-lactam agent and a macrolide given together to sicker, hospitalized patients with pneumococcal pneumonia. In an attempt to prevent the emergence of resistance, it has been recommended by some that the new fluoroquinolones not be used routinely as first-line agents in the treatment of community-acquired pneumonia; instead, they say, these agents should be reserved for patients who are allergic to the commonly used beta-lactam agents, for infections known to be or suspected of being caused by highly resistant strains, and for patients in whom initial therapy has failed.

Initial and follow-up costs by treatment outcome for children with respiratory infections

OBJECTIVE

To estimate the initial and follow-up costs of treatment of respiratory infections among pediatric patients and the relationship between costs and outcomes.

METHODS

A total of 3677 episodes of care from 2328 patients who were <17 years of age and had respiratory or ear infections that were treated with an antibiotic initially. The sample was drawn from the Medical Expenditure Panel Surveys for the years 1996 through 1999. Treatment failure was defined as the receipt of a second antibiotic, different from the first, in a 4-week window. We compared follow-up costs by outcome (treatment failure vs success) using a 2-part model of medical costs. We also performed a paired analysis by selecting 2 episodes, one in which the outcome was failure and the other in which the outcome was success, for patients with at least 1 of each type and computing the difference in costs.

RESULTS

Follow-up costs for provider visits for episodes for which the patient experienced treatment failure were 216 dollars versus 53 dollars for episodes for which the patient did not experience treatment failure. Follow-up drug costs, including the cost of the second antibiotic, were 75 dollars for children who experienced treatment failure versus 23 dollars, respectively. Cost estimates from the paired analysis were similar, confirming that results are not biased by unobserved time-invariant patient characteristics.

CONCLUSION

Children who have respiratory infections and experience treatment failure incur substantially higher costs.

Guidelines for Empiric Antimicrobial Prescribing in Community-Acquired Pneumonia

Empiric antimicrobial prescribing for community-acquired pneumonia remains a challenge, despite the availability of treatment guidelines. A number of key differences exist between North American and European guidelines, mainly in the outpatient setting. The North American approach is to use initial antimicrobial therapy, which provides coverage for Streptococcus pneumoniae plus atypical pathogens. Europeans tend to focus on providing pneumococcal coverage with less emphasis on covering for an atypical pathogen. Ambulatory patients without comorbidity are more likely to receive macrolide therapy in North America, whereas in Europe these patients would probably receive a beta-lactam agent. Major issues that are fundamental to this difference include the importance of providing therapy for atypical pathogens and the clinical significance of macrolide-resistant S pneumoniae. Prospective data are required to evaluate which of these two approaches offers clinical superiority.

Optimizing antibacterial therapy for community-acquired respiratory tract infections in children in an era of bacterial resistance

The spread of antibacterial resistance in bacteria that commonly cause childhood community-acquired respiratory tract infections (RTIs), such as acute otitis media, community-acquired pneumonia, and acute pharyngitis, is a major healthcare problem. One of the foremost concerns is the rapid increase in penicillin, macrolide, and multidrug resistance in Streptococcus pneumoniae. There is also a rising prevalence of macrolide resistance in Streptococcus pyogenes in pockets of the United States, and beta-lactamase production in Haemophilus influenzae is widespread. Although data are limited, some evidence suggests that resistance to antibacterials can impair bacteriologic and clinical outcomes in childhood RTIs. Optimizing antibacterial use is important both in the care of individual patients and within strategies to address the wider problem of antibacterial resistance. This involves encouraging judicious antibacterial use (i.e., reducing overuse for viral infection and prophylaxis), and preventing misuse through the wrong choice, dosage, and duration of therapy. Given that initial therapy is usually empiric, antibacterials used to treat community-acquired RTIs in children should ideally have the following properties: an optimal targeted spectrum of activity; high clinical and bacteriologic efficacy against respiratory pathogens, including resistant strains; simple, short-course therapy; and good tolerability and palatability. New antibacterials will continue to have a role in the treatment of RTIs in children, especially where resistance compromises existing therapies.

The clinical significance of macrolide-resistant Streptococcus pneumoniae: it's all relative

Macrolides are currently recommended as first-line agents for the empirical treatment of community-acquired pneumonia. Heavy use of these agents for a variety of indications has resulted in an increasing incidence of macrolide resistance among pneumococcal isolates. Although several case reports and small case series have suggested that in vitro macrolide resistance is associated with treatment failure in cases of pneumococcal pneumonia, other observational data suggest that drug susceptibility testing may not correlate with treatment failure. In this article, we review current information on the mechanisms of macrolide resistance and the pharmacodynamics of macrolide therapy, together with efficacy data from animal models and clinical observations, to begin to gauge the clinical significance of macrolide resistance in Streptococcus pneumoniae. Areas for further investigation are highlighted.

Antibiotic resistant infections due to Streptococcus pneumoniae: impact on therapeutic options and clinical outcome

PURPOSE OF REVIEW

Streptococcus pneumoniae is a major cause of morbidity and mortality in the pediatric population. The development of increasing resistance to multiple classes of antibiotics is making treatment of infections due to this organism much more difficult. The ultimate impact of high-level antibiotic resistance on therapeutic options and clinical outcomes of various pneumococcal infections is unclear and remains to be determined. Use of the conjugate pneumococcal vaccine has markedly decreased invasive pneumococcal disease in children under 5 years of age; however, its impact on decreasing antibiotic resistance is currently unknown.

RECENT FINDINGS

Studies suggest that response to therapy and clinical outcome of infections due to pneumococcal isolates with intermediate resistance to the beta-lactam antibiotics is no different from that of infections due to susceptible isolates. However, evidence is accumulating that infections caused by highly resistant pneumococcal isolates are associated with higher rates of treatment failure and mortality than infections due to susceptible strains.

SUMMARY

Use of a conjugate pneumococcal vaccine in conjunction with educational intervention programs that promote appropriate and judicious antibiotic use is a safe and effective means of decreasing the prevalence of pneumococcal disease in the pediatric population, decreasing the use of broad-spectrum antibiotic agents and potentially decreasing the amount of antibiotic resistance currently being seen.

Oral gemifloxacin once daily for 5 days compared with sequential therapy with i.v. ceftriaxone/oral cefuroxime (maximum of 10 days) in the treatment of hospitalized patients with acute exacerbations of chronic bronchitis

In a randomized, open-label, controlled, multicentre study, the clinical and bacteriological efficacy, safety and tolerability of oral gemifloxacin (320 mg once daily, 5 days) was compared with sequential intravenous (i.v.) ceftriaxone (1 g once daily, maximum 3 days) followed by oral cefuroxime axetil (500 mg twice daily, maximum 7 days) in adult hospitalized patients with acute exacerbations of chronic bronchitis (AECB) (n = 274). The clinical success rates at follow-up (21-28 days post-therapy) in the clinical per-protocol population (the primary endpoint) were 86.8% (105/121) for gemifloxacin vs. 81.3% (91/112) for ceftriaxone/cefuroxime (treatment difference = 5.5,95% CI -3.9,14.9). The corresponding clinical results in the clinical intention-to-treat (ITT) population were 82.6% (114/138) vs. 72.1% (98/136), respectively (treatment difference = 10.5,95% CI 0.7, 20.4).Thus, gemifloxacin had significantly higher clinical success rates than ceftriaxone/cefuroxime. The median time to discharge was 9 days in the gemifloxacin group vs. 11 days in the ceftriaxone/cefuroxime group (P = 0.04, Wilcoxon test). At follow-up, 120/138 (87.0%) gemifloxacin-treated patients had been discharged from hospital, compared with 111/136 (81.6%) ceftriaxone/cefuroxime-treated patients in the clinical ITT population. Both treatments were generally well tolerated and there was no significant difference between the treatment groups in the incidence or type of adverse events reported. A 5-day course of oral gemifloxacin was shown by this study to be at least equivalent to sequential i.v. ceftriaxone/cefuroxime axetil (for up to 10 days) in patients with AECB who require hospital treatment.

Oral gemifloxacin versus sequential therapy with intravenous ceftriaxone/oral cefuroxime with or without a macrolide in the treatment of patients hospitalized with community-acquired pneumonia: a randomized, open-label, multicenter study of clinical efficacy and tolerability

OBJECTIVE

This study aimed to compare the efficacy and safety of oral gemifloxacin, an enhanced-affinity quinolone, with sequential therapy with IV ceftriaxone followed by oral cefuroxime (with or without a macrolide) in patients hospitalized for community-acquired pneumonia (CAP).

METHODS

A randomized, open-label, multicenter study comprised adults hospitalized with a clinical and radiologic diagnosis of CAP. Patients were randomized 1:1 to receive either (1) oral gemifloxacin 320 mg once daily (7-14 days); or (2) IV ceftriaxone 2 g once daily (1-7 days) followed by oral cefuroxime 500 mg twice daily (1-13 days) for a total of < or = 14 days. Patients receiving ceftriaxone/cefuroxime were allowed concomitant macrolide treatment.

RESULTS

A total of 345 patients were randomized, of whom 341 received at least 1 dose of study medication (gemifloxacin, 169/172; ceftriaxone/cefuroxime, 172/173). Clinical success rates in the clinically evaluable (CE) population at follow-up (day 21-28 post-therapy), the primary end point, were 92.2% (107/116) for gemifloxacin and 93.4% (113/121) for ceftriaxone/cefuroxime (treatment difference, -1.15; 95% CI, -7.73 to 5.43). In patients in Fine risk classes IV and V, the clinical success rate was 87.0% (20/23) for gemifloxacin versus 83.3% (20/24) for ceftriaxone/cefuroxime. No difference in clinical response at follow-up was noted based on macrolide use. Bacteriologic success rates at follow-up in the bacteriologically evaluable (BE) population were 90.6% (58/64) for gemifloxacin and 87.3% (55/63) for ceftriaxone/cefuroxime (treatment difference 3.32; 95% CI, -7.57 to 14.21). The clinical success rate in bacteremic patients at follow-up (BE population) was 100.0%. Both treatments were generally well tolerated. The frequency and types of adverse events were similar between the 2 groups. The most common treatment-related adverse events with gemifloxacin were diarrhea, liver-function adverse events, and rash; with ceftriaxone/cefuroxime, they were diarrhea, elevated hepatic-enzyme activity, and moniliasis.

CONCLUSION

The clinical efficacy and tolerability of oral gemifloxacin 320 mg once daily were similar to those of IV ceftriaxone followed by oral cefuroxime (with or without a macrolide) in the treatment of adult patients hospitalized with moderate to severe CAP. Both treatments were effective in bacteremic patients and those at increased risk of mortality.

Outcome of treatment of respiratory tract infections due to Streptococcus pneumoniae, including drug-resistant strains, with pharmacokinetically enhanced amoxycillin/clavulanate

The efficacy of a new pharmacokinetically enhanced formulation of amoxycillin/clavulanate (AMX/CA) 2000/125 mg, twice daily, designed to provide adequate levels of amoxycillin over the 12-h dosing interval to eradicate penicillin-resistant Streptococcus pneumoniae (PRSP) with amoxycillin (+/-clavulanic acid) MICs of </=4 mg/l, was evaluated in patients with respiratory infections caused by S. pneumoniae, including PRSP (penicillin MICs 2-16 mg/l). Data from nine clinical studies were combined (total intent-to-treat N=5531). Six randomized, double-blind studies used levofloxacin 500 mg od in acute bacterial sinusitis (ABS), levofloxacin 500 mg od in acute exacerbations of chronic bronchitis (AECB), clarithromycin 500 mg bid in AECB, AMX/CA 875/125 mg bid and tid in community-acquired pneumonia (CAP) and AMX/CA 1000/125 mg tid in CAP as comparators. The three remaining studies (two in ABS and one in CAP) were non-comparative. In the AMX/CA 2000/125 mg bid-treated patients evaluable at follow-up (Day 14-39), outcome was successful in 60/64 (93.7%) patients with S. pneumoniae infections in the comparative studies and 348/363 (95.9%) in the non-comparative studies, including 95.6% of all patients and 95.2% of patients whose isolates had AMX/CA MICs of >/=4 mg/l. In the pooled comparator group, the success rate at follow-up was 86.5% (45/52). For PRSP (AMX/CA MICs of 0.5-8 mg/l), the overall success rate was 98.2% (55/56) at follow-up for AMX/CA 2000/125 mg and 50.0% (2/4) for comparators. AMX/CA 2000/125 mg shows efficacy comparable to that of the comparators evaluated against S. pneumoniae infections. Due to its favorable pharmacokinetic/pharmacodynamic profile and promising clinical success, the new AMX/CA 2000/125 mg formulation should be considered for the empirical treatment of respiratory tract infections in regions with a high prevalence of antimicrobial-resistant S. pneumoniae and in patients at high risk of antimicrobial-resistant S. pneumoniae infection as this formulation covers many PRSP that are non-susceptible to amoxycillin (+/-clavulanic acid) (MICs of >/=4 mg/l) as well as common beta-lactamase-producing respiratory pathogens.

The efficacy and safety of oral pharmacokinetically enhanced amoxycillin–clavulanate 2000/125 mg, twice daily, versus oral amoxycillin–clavulanate 1000/125 mg, three times daily, for the treatment of bacterial community-acquired pneumonia in adults

This double-blind, double-dummy, parallel-group study was designed to show that a pharmacokinetically enhanced formulation of oral amoxycillin-clavulanate (16:1, 2000/125 mg), twice daily, is at least as effective clinically and microbiologically as oral amoxycillin-clavulanate 1000/125 mg, three times daily, in the 10 day treatment of community-acquired pneumonia (CAP) in adults. The pharmacokinetically enhanced formulation is designed to provide higher serum concentrations of amoxycillin for a longer period than standard dosing to achieve coverage of Streptococcus pneumoniae isolates with amoxycillin-clavulanic acid minimum inhibitory concentrations (MICs) up to and including 4 mg/l. A total of 344 patients with CAP from 77 centres received amoxycillin-clavulanate 2000/125 mg twice daily for 10 days (169 patients) or amoxycillin-clavulanate 1000/125 mg three times daily for 10 days (175 patients). The most common pathogen isolated was S. pneumoniae (52.3% of patients, amoxycillin-clavulanate 2000/125 mg group; 46.8% of patients, amoxycillin-clavulanate 1000/125 mg group). In the clinical per-protocol (PP) population at test of cure (days 18-39), the clinical success rate in the amoxycillin-clavulanate 2000/125 mg group was at least as good as in the amoxycillin-clavulanate 1000/125 mg group (91.5 and 93.0%, respectively; 95% CI, -8.3, 5.4). The radiological and bacteriological success rates at test of cure for the PP populations were 92.4 and 90.6% in the amoxycillin-clavulanate 2000/125 mg group and 93.9 and 84.4% in the amoxycillin-clavulanate 1000/125 mg group, respectively. The clinical, bacteriological and radiological success rates at the end of therapy (days 11-17) for the PP populations were all over 85%. Both regimens were well tolerated, with no differences in adverse events between the groups. Amoxycillin-clavulanate 2000/125 mg, twice daily, is well tolerated and at least as effective clinically as amoxycillin-clavulanate 1000/125 mg, three times daily, in patients with CAP and may also be appropriate for the treatment of infections due to S. pneumoniae strains with high-level penicillin resistance.

Efficacy and tolerability of gatifloxacin in community treatment of acute exacerbations of chronic bronchitis

BACKGROUND

Recognizing acute exacerbations of chronic bronchitis (AECB) and selecting appropriate antibiotic treatment for patients who would benefit most is a challenge for community-based physicians.

OBJECTIVE

The Tequin Clinical Experience Study, an open-label, noncomparative, postmarketing trial, assessed the efficacy and tolerability of gatifloxacin, an 8-methoxy fluoroquinolone, in the treatment of AECB in the community-practice setting.

METHODS

Consecutive patients with respiratory tract infections in community-based settings were eligible for participation. Treated patients (N = 2512) included 1107 men (44.1%) and 1405 women (55.9%) aged > or =18 years with a clinical diagnosis of chronic bronchitis. All participants received oral gatifloxacin 400 mg once daily for 7 to 10 days. Clinical response was determined via telephone contact conducted by the investigator or study coordinator using case-report forms or during an office visit after the last dose. The investigator or coordinator collected expectorated or induced sputum specimens that were then smeared on a microscope slide, stored in a tube, and transported to a central reference laboratory for Gram-staining and culture. Of 1388 pretreatment sputum specimens submitted, pathogens were isolated from 424.

RESULTS

The most frequently detected pathogens were Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae. All H. influenzae and 99% of S. pneumoniae isolates tested were susceptible to gatifloxacin. Of the 2267 patients with a determinable clinical response, 2084 (91.9% [95% CI, 90.8%-93.0%]) were cured (all acute symptoms improved or returned to baseline level, no new symptoms present, no additional antibiotic required). The 95.8% cure rate in 166 patients with H. influenzae included 100% of those with beta-lactamase-positive strains. Overall, 89.2% of 111 patients with M. catarrhalis were cured; rates were similar regardless of beta-lactamase production. The clinical cure rate in 74 patients with S. pneumoniae was 98.6% and was independent of the degree of penicillin resistance (minimum inhibitory concentration > or =2.0 microg/ mL). All 6 patients infected with S. pneumoniae fully resistant to penicillin were cured. Gatifloxacin was generally well tolerated, and the majority of adverse events were mild to moderate; only 11 drug-related adverse events in 10 patients (0.4%) were serious. Drug-related nausea (3.0%), dizziness (1.5%), diarrhea (1.2%), and vomiting (0.9%) were the most common adverse events.

CONCLUSIONS

The high clinical cure rate and favorable tolerability support gatifloxacin as a rational choice for the treatment of AECB in patients such as those in this community-based study.

Penicillin-resistant pneumococci-implications for management of community-acquired pneumonia and meningitis

Penicillin-nonsusceptible Streptococcus pneumoniae isolates have become increasingly prevalent worldwide. They are well-known agents of community-acquired infections such as otitis media, pneumonia and bacterial meningitis. Therapy of pneumococcal infections is made difficult by the emergence and spread of bacterial resistance to penicillin and other beta-lactams, as well as other antimicrobials such as macrolides. This article reviews current concepts of epidemiology and the implications of penicillin-nonsusceptible pneumococci for management of community-acquired pneumonia and meningitis.