Clinical cure rates in subjects treated with azithromycin for community-acquired respiratory tract infections caused by azithromycin-susceptible or azithromycin-resistant Streptococcus pneumoniae: analysis of Phase 3 clinical trial data

Macrolides Decrease the Proinflammatory Activity of Macrolide-Resistant Streptococcus pneumoniae

Over the past 2 decades, the prevalence of macrolide-resistant Streptococcus pneumoniae (MRSP) has increased considerably, due to widespread macrolide use. Although macrolide usage has been proposed to be associated with treatment failure in patients with pneumococcal diseases, macrolides may be clinically effective for treating these diseases, regardless of the susceptibility of the causative pneumococci to macrolides. As we previously demonstrated that macrolides downregulate the transcription of various genes in MRSP, including the gene encoding the pore-forming toxin pneumolysin, we hypothesized that macrolides affect the proinflammatory activity of MRSP. Using HEK-Blue cell lines, we found that the supernatants from macrolide-treated MRSP cultures induced decreased NF-κB activation in cells expressing Toll-like receptor 2 and nucleotide-binding oligomerization domain 2 compared to the supernatants from untreated MRSP cells, suggesting that macrolides inhibit the release of these ligands from MRSP. Real-time PCR analysis revealed that macrolides significantly downregulated the transcription of various genes encoding peptidoglycan synthesis-, lipoteichoic acid synthesis-, and lipoprotein synthesis-related molecules in MRSP cells. The silkworm larva plasma assay demonstrated that the peptidoglycan concentrations in the supernatants from macrolide-treated MRSP cultures were significantly lower than those from untreated MRSP cultures. Triton X-114 phase separation revealed that lipoprotein expression decreased in macrolide-treated MRSP cells compared to the lipoprotein expression in untreated MRSP cells. Consequently, macrolides may decrease the expression of bacterial ligands of innate immune receptors, resulting in the decreased proinflammatory activity of MRSP. IMPORTANCE To date, the clinical efficacy of macrolides in pneumococcal disease is assumed to be linked to their ability to inhibit the release of pneumolysin. However, our previous study demonstrated that oral administration of macrolides to mice intratracheally infected with macrolide-resistant Streptococcus pneumoniae resulted in decreased levels of pneumolysin and proinflammatory cytokines in bronchoalveolar lavage fluid samples compared to the levels in samples from untreated infected control mice, without affecting the bacterial load in the fluid. This finding suggests that additional mechanisms by which macrolides negatively regulate proinflammatory cytokine production may be involved in their efficacy in vivo. Furthermore, in this study, we demonstrated that macrolides downregulated the transcription of various proinflammatory-component-related genes in S. pneumoniae, which provides an additional explanation for the clinical benefits of macrolides.

Pediatric Antibiotic Stewardship for Community-Acquired Pneumonia: A Pre-Post Intervention Study

We aimed to investigate the effectiveness of an antibiotic stewardship program (ASP) on antibiotic prescription in children with community-acquired pneumonia (CAP). Antibiotic purchasing data were collected for children aged 3 months to 18 years diagnosed with CAP from November 2016 to April 2017 (pre-intervention period) and from November 2017 to April 2018 (post-intervention period). The intervention was a 1-day seminar for primary care pediatricians on the diagnosis and treatment of CAP in children according to national guidelines. There was a substantial decrease in the use of azithromycin after the intervention. In younger children, there was a 42% decrease, alongside an increased use of amoxicillin (P < .001). In older children, there was a smaller, non-statistically significant decrease in the use of azithromycin (P = .45). Our data demonstrate that the implementation of an ASP was associated with a reduction in the use of broad-spectrum antibiotics and macrolides and increased guideline adherence for the safe treatment of CAP.

Overcoming Acquired and Native Macrolide Resistance with Bicarbonate

The growing challenge of microbial resistance emphasizes the importance of new antibiotics or reviving strategies for the use of old ones. Macrolide antibiotics are potent bacterial protein synthesis inhibitors with a formidable capacity to treat life-threatening bacterial infections; however, acquired and intrinsic resistance limits their clinical application. In the work presented here, we reveal that bicarbonate is a potent enhancer of the activity of macrolide antibiotics that overcomes both acquired and intrinsic resistance mechanisms. With a focus on azithromycin, a highly prescribed macrolide antibiotic, and using clinically relevant pathogens, we show that physiological concentrations of bicarbonate overcome drug resistance by increasing the intracellular concentration of azithromycin. We demonstrate the potential of bicarbonate as a formulation additive for topical use of azithromycin in treating a murine wound infection caused by Pseudomonas aeruginosa. Further, using a systemic murine model of methicillin-resistant Staphylococcus aureus (MRSA) infection, we demonstrate the potential role of physiological bicarbonate, naturally abundant in the host, to enhance the activity of azithromycin against macrolide-resistant MRSA. In all, our findings suggest that macrolide resistance, observed in the clinical microbiology laboratory using standard culturing techniques, is a poor predictor of efficacy in the clinic and that observed resistance should not necessarily hamper the use of macrolides. Whether as a formulation additive for topical use or as a natural component of host tissues, bicarbonate is a powerful potentiator of macrolides with the capacity to overcome drug resistance in life-threatening bacterial infections.

Community acquired pneumonia among adult patients at an Egyptian university hospital: bacterial etiology, susceptibility profile and evaluation of the response to initial empiric antibiotic therapy

Background

Effective empirical antibiotic therapy for community acquired pneumonia (CAP), based on frequently updated data about the pattern of bacterial distribution and their antimicrobial susceptibilities, is mandatory.

Aim

To identify the bacterial etiology of CAP in adults and their antibiotic susceptibility patterns and to evaluate the response to initial empirical antibiotic therapy in an Egyptian university hospital.

Settings and design

A cross-sectional hospital-based study.

Patients and methods

CAP cases were selected by systemic random sampling from those admitted to the chest department. All were evaluated at admission and 4 days after starting empiric therapy. Typical bacteria were isolated, identified and tested for their antibiotic susceptibility. An indirect IF assay was used to diagnose atypical bacteria. Clinical response to initial empiric antibiotic therapy was clinically, laboratory and radiologically evaluated.

Results

Two hundred and seventy CAP patients were included. Bacteria represented 50.4% of them. Klebsiella pneumoniae was the most prevalent bacterium (10.37%) followed by Streptococcus pneumoniae and P. aeruginosa (7.78% each). Overall, 76.2% of isolates showed a multidrug resistant phenotype: 82.61% (19/23) S. pneumoniae, 89.66 % (26/29) K. pneumoniae, 65.22% (15/23) Pseudomonas aeruginosa, 87.50% (7/8) Escherichia coli and 81.25 % (13/16) Staphylococcus aureus. Broad spectrum β-lactams, especially carbapenems, and moxifloxacin showed in vitro efficacy on most of the tested isolates. Forty-three cases (15.9%) were nonresponders, 37 (86%) of them showed bacterial etiology. The highest rate of nonresponsiveness (30.43%) was observed in cases receiving antipseudomonal/antipneumococcal β-lactam plus a fluoroquinolone for suspected P. aeruginosa infection.

Conclusion

Multidrug resistance in bacteria causing CAP and high frequency of isolation of hospital pathogens are prominent features of this study. Azithromycin containing regimens were associated with the lowest rates of nonresponsiveness. Development and implementation of an antibiotic stewardship program are highly recommended for CAP management.

Mechanism of Macrolide-Induced Inhibition of Pneumolysin Release Involves Impairment of Autolysin Release in Macrolide-Resistant Streptococcus pneumoniae

Streptococcus pneumoniae is a leading cause of community-acquired pneumonia. Over the past 2 decades, macrolide resistance among S. pneumoniae organisms has been increasing steadily and has escalated at an alarming rate worldwide. However, the use of macrolides in the treatment of community-acquired pneumonia has been reported to be effective regardless of the antibiotic susceptibility of the causative pneumococci. Although previous studies suggested that sub-MICs of macrolides inhibit the production of the pneumococcal pore-forming toxin pneumolysin by macrolide-resistant S. pneumoniae (MRSP), the underlying mechanisms of the inhibitory effect have not been fully elucidated. Here, we show that the release of pneumococcal autolysin, which promotes cell lysis and the release of pneumolysin, was inhibited by treatment with azithromycin and erythromycin, whereas replenishing with recombinant autolysin restored the release of pneumolysin from MRSP. Additionally, macrolides significantly downregulated ply transcription followed by a slight decrease of the intracellular pneumolysin level. These findings suggest the mechanisms involved in the inhibition of pneumolysin in MRSP, which may provide an additional explanation for the benefits of macrolides on the outcome of treatment for pneumococcal diseases.

Diagnosis and treatment of community-acquired pneumonia in adults: 2016 clinical practice guidelines by the Chinese Thoracic Society, Chinese Medical Association

Community‐acquired pneumonia (CAP) in adults is an infectious disease with high morbidity in China and the rest of the world. With the changing pattern in the etiological profile of CAP and advances in medical techniques in diagnosis and treatment over time, Chinese Thoracic Society of Chinese Medical Association updated its CAP guideline in 2016 to address the standard management of CAP in Chinese adults. Extensive and comprehensive literature search was made to collect the data and evidence for experts to review and evaluate the level of evidence. Corresponding recommendations are provided appropriately based on the level of evidence. This updated guideline covers comprehensive topics on CAP, including aetiology, antimicrobial resistance profile, diagnosis, empirical and targeted treatments, adjunctive and supportive therapies, as well as prophylaxis. The recommendations may help clinicians manage CAP patients more effectively and efficiently. CAP in pediatric patients and immunocompromised adults is beyond the scope of this guideline. This guideline is only applicable for the immunocompetent CAP patients aged 18 years and older. The recommendations on selection of antimicrobial agents and the dosing regimens are not mandatory. The clinicians are recommended to prescribe and adjust antimicrobial therapies primarily based on their local etiological profile and results of susceptibility testing, with reference to this guideline.

Implications of Antibiotic Resistance for Patients' Recovery From Common Infections in the Community: A Systematic Review and Meta-analysis

BACKGROUND

Antibiotic use is the main driver for carriage of antibiotic-resistant bacteria. The perception exists that failure of antibiotic treatment due to antibiotic resistance has little clinical impact in the community.

METHODS

We searched MEDLINE, EMBASE, PubMed, Cochrane Central Register of Controlled Trials, and Web of Science from inception to 15 April 2016 without language restriction. We included studies conducted in community settings that reported patient-level data on laboratory-confirmed infections (respiratory tract, urinary tract, skin or soft tissue), antibiotic resistance, and clinical outcomes. Our primary outcome was clinical response failure. Secondary outcomes were reconsultation, further antibiotic prescriptions, symptom duration, and symptom severity. Where possible, we calculated odds ratios with 95% confidence intervals by performing meta-analysis using random effects models.

RESULTS

We included 26 studies (5659 participants). Clinical response failure was significantly more likely in participants with antibiotic-resistant Escherichia coli urinary tract infections (odds ratio [OR] = 4.19; 95% confidence interval [CI] = 3.27-5.37; n = 2432 participants), Streptococcus pneumoniae otitis media (OR = 2.51; 95% CI = 1.29-4.88; n = 921 participants), and S. pneumoniae community-acquired pneumonia (OR = 2.15; 95% CI = 1.32-3.51; n = 916 participants). Clinical heterogeneity precluded primary outcome meta-analysis for Staphylococcus aureus skin or soft-tissue infections.

CONCLUSIONS

Antibiotic resistance significantly impacts on patients' illness burden in the community. Patients with laboratory-confirmed antibiotic-resistant urinary and respiratory-tract infections are more likely to experience delays in clinical recovery after treatment with antibiotics. A better grasp of the risk of antibiotic resistance on outcomes that matter to patients should inform more meaningful discussions between healthcare professionals and patients about antibiotic treatment for common infections.

Variability in Antibiotic Prescribing for Community-Acquired Pneumonia

BACKGROUND AND OBJECTIVES

Published guidelines recommend amoxicillin for most children with community-acquired pneumonia (CAP), yet macrolides and broad-spectrum antibiotics are more commonly prescribed. We aimed to determine the patient and clinician characteristics associated with the prescription of amoxicillin versus macrolide or broad-spectrum antibiotics for CAP.

METHODS

Retrospective cohort study in an outpatient pediatric primary care network from July 1, 2009 to June 30, 2013. Patients prescribed amoxicillin, macrolides, or a broad-spectrum antibiotic (amoxicillin-clavulanic acid, cephalosporin, or fluoroquinolone) for CAP were included. Multivariable logistic regression models were implemented to identify predictors of antibiotic choice for CAP based on patient- and clinician-level characteristics, controlling for practice.

RESULTS

Of 10 414 children, 4239 (40.7%) received amoxicillin, 4430 (42.5%) received macrolides and 1745 (16.8%) received broad-spectrum antibiotics. The factors associated with an increased odds of receipt of macrolides compared with amoxicillin included patient age ≥5 years (adjusted odds ratio [aOR]: 6.18; 95% confidence interval [CI]: 5.53-6.91), previous antibiotic receipt (aOR: 1.79; 95% CI: 1.56-2.04), and private insurance (aOR: 1.47; 95% CI: 1.28-1.70). The predicted probability of a child being prescribed a macrolide ranged significantly between 0.22 and 0.83 across clinics. The nonclinical characteristics associated with an increased odds of receipt of broad-spectrum antibiotics compared with amoxicillin included suburban practice (aOR: 7.50; 95% CI: 4.16-13.55) and private insurance (aOR: 1.42; 95% CI: 1.18-1.71).

CONCLUSIONS

Antibiotic choice for CAP varied widely across practices. Factors unlikely related to the microbiologic etiology of CAP were significant drivers of antibiotic choice. Understanding drivers of off-guideline prescribing can inform targeted antimicrobial stewardship initiatives.

Pneumolysin as a potential therapeutic target in severe pneumococcal disease

Acute pulmonary and cardiac injury remain significant causes of morbidity and mortality in those afflicted with severe pneumococcal disease, with the risk for early mortality often persisting several years beyond clinical recovery. Although remaining to be firmly established in the clinical setting, a considerable body of evidence, mostly derived from murine models of experimental infection, has implicated the pneumococcal, cholesterol-binding, pore-forming toxin, pneumolysin (Ply), in the pathogenesis of lung and myocardial dysfunction. Topics covered in this review include the burden of pneumococcal disease, risk factors, virulence determinants of the pneumococcus, complications of severe disease, antibiotic and adjuvant therapies, as well as the structure of Ply and the role of the toxin in disease pathogenesis. Given the increasing recognition of the clinical potential of Ply-neutralisation strategies, the remaining sections of the review are focused on updates of the types, benefits and limitations of currently available therapies which may attenuate, directly and/or indirectly, the injurious actions of Ply. These include recently described experimental therapies such as various phytochemicals and lipids, and a second group of more conventional agents the members of which remain the subject of ongoing clinical evaluation. This latter group, which is covered more extensively, encompasses macrolides, statins, corticosteroids, and platelet-targeted therapies, particularly aspirin.

What is the clinical relevance of drug-resistant pneumococcus?

PURPOSE OF REVIEW

Pneumococcal infections are a major cause of morbidity and mortality worldwide. In recent years, Streptococcus pneumoniae has shown increasing resistance to a several antibiotics, becoming a worldwide problem. The impact of antibiotic resistance of S. pneumoniae on clinical outcomes is still controversial. The principal reason for this controversy is the existence of several factors related to the patients and to the pathogen that may influence how antibiotic resistance patterns affect clinical outcomes. The aim of this review is to discuss current knowledge of the epidemiological data on antibiotic resistance; we also discuss mechanisms and risk factors for antibiotic resistance.

RECENT FINDINGS

The phenomenon of serotype replacement after the introduction of conjugate pneumococcal vaccinations and the escalation of antibiotic resistance worldwide remains an important issue in terms of their impact on clinical outcomes in pneumococcal disease. Antimicrobial resistance of pneumococcus leads to changes in the clinical presentation of pneumococcal disease, making it more difficult to diagnose and to treat. Consumption of antibiotics in the community is directly proportional to antimicrobial resistance. Carriage of S. pneumoniae and infection with antibiotic-resistant pneumococcus is associated with prior antibiotic therapy, extremes of age, presence of comorbidities (i.e. COPD), attendance at child day care centers, crowded conditions, intra-familial transmission, and nursing home residence.

SUMMARY

Antibiotic-resistant S. pneumoniae is a worldwide problem. The implementation of several strategies including vaccine campaigns, prudent use of current antibiotics, and programs for the surveillance of pneumococcal infections, could limit the increasing resistance of this pathogen to antimicrobials.

Macrolide resistance in pneumococci-is it relevant?

Macrolide antibiotics are widely used for a range of indications, including pneumonia. Both high-level and low-level resistance to macrolides is increasing in pneumococci globally. Macrolide resistance in pneumococci is of limited clinical relevance where ß-lactams remain the mainstay of treatment, such as for moderate/severe pneumonia; however, data suggest that macrolides may not be able to be relied on as monotherapy for serious pneumococcal infections.

Azithromycin Dose To Maximize Efficacy and Suppress Acquired Drug Resistance in Pulmonary Mycobacterium avium Disease

Mycobacterium aviumcomplex is now the leading mycobacterial cause of chronic pneumonia in the United States. Macrolides and ethambutol form the backbone of the regimen used in the treatment of pulmonary disease. However, therapy outcomes remain poor, with microbial cure rates of 4% in cavitary disease. The treatment dose of azithromycin has mostly been borrowed from that used to treat other bacterial pneumonias; there are no formal dose-response studies in pulmonaryM. aviumdisease and the optimal dose is unclear. We utilized population pharmacokinetics and pharmacokinetics/pharmacodynamics-derived azithromycin exposures associated with optimal microbial kill or resistance suppression to perform 10,000 patient Monte Carlo simulations of dose effect studies for daily azithromycin doses of 0.5 to 10 g. The currently recommended dose of 500 mg per day achieved the target exposures in 0% of patients. Exposures associated with optimal kill and resistance suppression were achieved in 87 and 54% of patients, respectively, only by the very high dose of 8 g per day. The azithromycin susceptibility breakpoint above which patients failed therapy on the very high doses of 8 g per day was an MIC of 16 mg/liter, suggesting a critical concentration of 32 mg/liter, which is 8-fold lower than the currently used susceptibility breakpoint of 256 mg/liter. If the standard dose of 500 mg a day were used, then the critical concentration would fall to 2 mg/liter, 128-fold lower than 256 mg/liter. The misclassification of resistant isolates as susceptible could explain the high failure rates of current doses.

Recent Developments in Pediatric Community-Acquired Pneumonia

Community-acquired pneumonia (CAP) is the most common acute infectious cause of death in children worldwide. Consequently, research into the epidemiology, diagnosis, treatment, and prevention of pediatric CAP spans the translational research spectrum. Herein, we aim to review the most significant findings reported by investigators focused on pediatric CAP research that has been reported in 2014 and 2015. Our review focuses on several key areas relevant to the clinical management of CAP. First, we will review recent advances in the understanding of CAP epidemiology worldwide, including the role of vaccination in the prevention of pediatric CAP. We also report on the expanding role of existing and emerging diagnostic technologies in CAP classification and management, as well as advances in optimizing antimicrobial use. Finally, we will review CAP management from the policy and future endeavors standpoint, including the influence of clinical practice guidelines on clinician management and patient outcomes, and future potential research directions that are in the early stages of investigation.

Antibiotic Resistance in Streptococcus pneumoniae after Azithromycin Distribution for Trachoma

Trachoma is caused by Chlamydia trachomatis and is a leading cause of blindness worldwide. Mass distribution of azithromycin (AZM) is part of the strategy for the global elimination of blinding trachoma by 2020. Although resistance to AZM in C. trachomatis has not been reported, there have been concerns about resistance in other organisms when AZM is administered in community settings. We identified studies that measured pneumococcal prevalence and resistance to AZM following mass AZM provision reported up to 2013 in Medline and Web of Science databases. Potential sources of bias were assessed using the Cochrane Risk of Bias Tool. A total of 45 records were screened, of which 8 met the inclusion criteria. We identified two distinct trends of resistance prevalence, which are dependent on frequency of AZM provision and baseline prevalence of resistance. We also demonstrated strong correlation between the prevalence of resistance at baseline and at 2-3 months (r = 0.759). Although resistance to AZM in C. trachomatis has not been reported, resistance to this commonly used macrolide antibiotic in other diseases could compromise treatment. This should be considered when planning long-term trachoma control strategies.