Clinical implications of macrolide resistance in community-acquired respiratory tract infections

The impact of long-term azithromycin on antibiotic resistance in HIV-associated chronic lung disease

Selection for resistance to azithromycin (AZM) and other antibiotics such as tetracyclines and lincosamides remains a concern with long-term AZM use for treatment of chronic lung diseases (CLD). We investigated the impact of 48 weeks of AZM on the carriage and antibiotic resistance of common respiratory bacteria among children with HIV-associated CLD. Nasopharyngeal (NP) swabs and sputa were collected at baseline, 48 and 72 weeks from participants with HIV-associated CLD randomised to receive weekly AZM or placebo for 48 weeks and followed post-intervention until 72 weeks. The primary outcomes were prevalence and antibiotic resistance of Streptococcus pneumoniae (SP), Staphylococcus aureus (SA), Haemophilus influenzae (HI) and Moraxella catarrhalis (MC) at these timepoints. Mixed-effects logistic regression and Fisher's exact test were used to compare carriage and resistance, respectively. Of 347 (174 AZM, 173 placebo) participants (median age 15 years (IQR 13-18), female 49%), NP carriage was significantly lower in the AZM (n=159) compared to placebo (n=153) arm for SP (18% versus 41%, p<0.001), HI (7% versus 16%, p=0.01) and MC (4% versus 11%, p=0.02); SP resistance to AZM (62% (18 out of 29) versus 13% (8 out of 63), p<0.0001) or tetracycline (60% (18 out of 29) versus 21% (13 out of 63), p<0.0001) was higher in the AZM arm. Carriage of SA resistant to AZM (91% (31 out of 34) versus 3% (1 out of 31), p<0.0001), tetracycline (35% (12 out of 34) versus 13% (4 out of 31), p=0.05) and clindamycin (79% (27 out of 34) versus 3% (1 out of 31), p<0.0001) was also significantly higher in the AZM arm and persisted at 72 weeks. Similar findings were observed for sputa. The persistence of antibiotic resistance and its clinical relevance for future infectious episodes requiring treatment needs further investigation.

Streptococcus pneumoniae and chronic endobronchial infections in childhood

Streptococcus pneumoniae (pneumococcus) is the main cause of bacterial pneumonia worldwide and has been studied extensively in this context. However, its role in chronic endobronchial infections and accompanying lower airway neutrophilic infiltration has received little attention. Severe and recurrent pneumonia are risk factors for chronic suppurative lung disease (CSLD) and bronchiectasis; the latter causes considerable morbidity and, in some populations, premature death in children and adults. Protracted bacterial bronchitis (PBB) is another chronic endobronchial infection associated with substantial morbidity. In some children, PBB may progress to bronchiectasis. Although nontypeable Haemophilus influenzae is the main pathogen in PBB, CSLD and bronchiectasis, pneumococci are isolated commonly from the lower airways of children with these diagnoses. Here we review what is known currently about pneumococci in PBB, CSLD and bronchiectasis, including the importance of pneumococcal nasopharyngeal colonization and how persistence in the lower airways may contribute to the pathogenesis of these chronic pulmonary disorders. Antibiotic treatments, particularly long-term azithromycin therapy, are discussed together with antibiotic resistance and the impact of pneumococcal conjugate vaccines. Important areas requiring further investigation are identified, including immune responses associated with pneumococcal lower airway infection, alone and in combination with other respiratory pathogens, and microarray serotyping to improve detection of carriage and infection by multiple serotypes. Genome wide association studies of pneumococci from the upper and lower airways will help identify virulence and resistance determinants, including potential therapeutic targets and vaccine antigens to treat and prevent endobronchial infections. Much work is needed, but the benefits will be substantial.

Bronchiectasis in Children: Current Concepts in Immunology and Microbiology

Bronchiectasis is a complex chronic respiratory condition traditionally characterized by chronic infection, airway inflammation, and progressive decline in lung function. Early diagnosis and intensive treatment protocols can stabilize or even improve the clinical prognosis of children with bronchiectasis. However, understanding the host immunologic mechanisms that contribute to recurrent infection and prolonged inflammation has been identified as an important area of research that would contribute substantially to effective prevention strategies for children at risk of bronchiectasis. This review will focus on the current understanding of the role of the host immune response and important pathogens in the pathogenesis of bronchiectasis (not associated with cystic fibrosis) in children.

In vitro activity of bioactive extracts from rare actinomycetes against multi-drug resistant Streptococcus pneumoniae

AIMS

In this study, we investigated the in vitro potential of the bioactive extracts from five putatively novel species of actinomycetes isolated from the Indian hot desert against multi-drug resistant (MDR) Streptococcus pneumoniae.

METHODS AND RESULTS

The antimicrobial activity of 10 different extracts was evaluated against S. pneumoniae strains with, erm(B) and mef(E) genes as well as fluoroquinolone-resistant (FQ(R) ) strains using the micro-broth dilution method. Of these 10 extracts, four exhibited good to excellent anti-S. pneumoniae activity with minimum inhibitory concentrations (MICs) ranging from 0·125 to 8 μg ml(-1) . The time-kill kinetics study showed that these extracts killed the pathogens in 2-8 h. In vitro cell-free transcription/translation of luciferase gene using S30 bacterial extract and TNT mammalian ribosome indicated that they inhibited bacterial ribosomes at much lower concentrations than those required to inhibit the mammalian ribosomes.

CONCLUSIONS

This study demonstrates that these are potent concentration-dependent bactericidal metabolites with 16-fold higher in vitro activity than levofloxacin against MDR S. pneumoniae.

SIGNIFICANCE AND IMPACT OF THE STUDY

Metabolites from actinomycetes can be excellent inhibitors of MDR S. pneumoniae. Considering the in vitro efficacy of these crude extracts against S. pneumoniae MDR spp., once purified these can be used against streptococcal pathogens causing community-acquired pneumonia.

Antimicrobial stewardship in pediatrics: focusing on the challenges clinicians face

Background

Antimicrobial use is very common in hospitalized children. An assessment of clinician’s prevailing knowledge and clinical approach to prescribing antimicrobials is helpful in order to develop the best strategies for successful stewardship programs. The objectives of the study were to determine fundamental knowledge of principles, approach to antimicrobial use through the clinical vignettes and to identify perceived challenges in decreasing antimicrobial use.

Methods

A questionnaire was developed by subject matter experts and pretested to ensure validity. Using a cross-sectional prospective design, the questionnaire was completed anonymously by staff and trainee physicians at a single tertiary care pediatric hospital between late November 2011 and February 2012.

Results

Of 159 eligible physicians, 86 (54.1%) responded, of which 77 (46 staff and 31 trainees) reported regularly prescribing antimicrobials. The majority of physicians had modest knowledge of factors that would increase risk of resistance however, less than 20% had correct knowledge of local resistance patterns for common bacteria. Almost half of physicians correctly answered the clinical vignettes. Over half of trainees and one third of staff relied most on online manuals for information regarding antimicrobials to assist prescription decision-making. Overall, physicians perceived that discontinuing empiric antimicrobials was the most difficult to achieve to decrease antibiotic use.

Conclusions

Our results highlight several challenges that pediatric practioners face with respect to knowledge and approach to antimicrobial prescribing. Pediatric stewardship programs could in this setting focus on discontinuing antimicrobials appropriately and promoting local antibiograms in the proper clinical setting to decrease overall use of antimicrobials.

A novel ketolide, RBx 14255, with activity against multidrug-resistant Streptococcus pneumoniae

We present here the novel ketolide RBx 14255, a semisynthetic macrolide derivative obtained by the derivatization of clarithromycin, for its in vitro and in vivo activities against sensitive and macrolide-resistant Streptococcus pneumoniae. RBx 14255 showed excellent in vitro activity against macrolide-resistant S. pneumoniae, including an in-house-generated telithromycin-resistant strain (S. pneumoniae 3390 NDDR). RBx 14255 also showed potent protein synthesis inhibition against telithromycin-resistant S. pneumoniae 3390 NDDR. The binding affinity of RBx 14255 toward ribosomes was found to be more than that for other tested drugs. The in vivo efficacy of RBx 14255 was determined in murine pulmonary infection induced by intranasal inoculation of S. pneumoniae ATCC 6303 and systemic infection with S. pneumoniae 3390 NDDR strains. The 50% effective dose (ED50) of RBx 14255 against S. pneumoniae ATCC 6303 in a murine pulmonary infection model was 3.12 mg/kg of body weight. In addition, RBx 14255 resulted in 100% survival of mice with systemic infection caused by macrolide-resistant S. pneumoniae 3390 NDDR at 100 mg/kg four times daily (QID) and at 50 mg/kg QID. RBx 14255 showed favorable pharmacokinetic properties that were comparable to those of telithromycin.

Synthesis and antibacterial activity of a novel class of 15-membered macrolide antibiotics, "11a-azalides"

An efficient method for the reconstruction of the 9-dihydroerythromycin A macrolactone skeleton has been established. The key steps are oxidative cleavage at the 11,12-position and reconstruction after insertion of an appropriate functionalized amino alcohol. Novel 15-membered macrolides, we named as "11a-azalides", were synthesized based on the above methodology and evaluated for their antibacterial activity. Among them, (13R)-benzyloxymethyl-11a-azalide showed the most potent Streptococcus pneumoniae activity, with improved activity against a representative erythromycin-resistant strain compared to clarithromycin (CAM).

Efficacy of clarithromycin against experimentally induced pneumonia caused by clarithromycin-resistant Haemophilus influenzae in mice

Clarithromycin is a 14-member lactone ring macrolide with potent activity against Haemophilus influenzae, including ampicillin-resistant strains. We evaluated the in vivo efficacy of clarithromycin at 40 mg/day and 100 mg/day for 3 days in the treatment of a murine model of pneumonia using a macrolide-resistant H. influenzae strain, which was also ampicillin resistant. The MIC of clarithromycin was 64 microg/ml. The viable bacterial counts in infected tissues after treatment with 100 mg clarithromycin/kg of body weight were lower than the counts obtained in control and 40-mg/kg clarithromycin-treated mice. The concentrations of macrophage inflammatory protein 2 (MIP-2) and interleukin 1beta (IL-1beta) in bronchoalveolar lavage fluid (BALF) samples from mice treated at both concentrations were lower than in the control group. Pathologically, following infection, clarithromycin-treated mice, particularly at a dose of 100 mg/kg, showed lower numbers of neutrophils in alveolar walls, and inflammatory changes had apparently improved, whereas large aggregates of inflammatory cells were observed within the alveoli of control mice. In addition, we demonstrated that clarithromycin has bacteriological effects against intracellular bacteria at levels below the MIC. Our results indicate that clarithromycin may be useful in vivo for macrolide-resistant H. influenzae, and this phenomenon may be related to the good penetration of clarithromycin into bronchoepithelial cells. We also believe that conventional drug susceptibility tests may not reflect the in vivo effects of clarithromycin.

Clinical efficacy and time to symptom resolution of 5-day telithromycin versus 10-day amoxicillin-clavulanate in the treatment of acute bacterial sinusitis

OBJECTIVE

This study compared the clinical efficacy, time to symptom resolution, and tolerability of a 5-day regimen of telithromycin with a 10-day regimen of high-dose amoxicillin-clavulanate in acute bacterial sinusitis (ABS).

RESEARCH DESIGN AND METHODS

In this multinational (41 centers in Canada, Germany, Greece, Portugal, and Turkey), open-label, noninferiority study, patients >/=18 years old (n=298) with a clinical (>7 days' symptoms) and radiological (air/fluid level, total opacification, mucosal thickening >/=10 mm) diagnosis of ABS were randomized to receive telithromycin 800 mg once daily for 5 days or amoxicillin-clavulanate 875/125 mg twice daily for 10 days. Clinical efficacy and tolerability were assessed at the test-of-cure visit (days 17-21). Time to symptom resolution was based on patients' daily diary assessment of individual symptoms.

RESULTS

The per-protocol clinical success rate (primary endpoint) with telithromycin (88.6% (109/123)) was noninferior to that with amoxicillin-clavulanate (88.8% (111/125)) (95% confidence interval: -8.9 to 8.5). In the modified intention-to-treat (mITT) population, the median time for 50% reduction of total symptom scores was significantly shorter for telithromycin (4 days) vs. amoxicillin-clavulanate (5 days; p=0.044); median times for 75% reduction of total symptom scores were: telithromycin, 7 days; amoxicillin-clavulanate, 8 days (p=0.115). The median time for reduction of total symptom scores to the absent/very mild category (mITT population) was 6 days for telithromycin vs. 8 days for amoxicillin-clavulanate (p=0.04). All treatment-emergent adverse events (TEAEs) were mostly gastrointestinal and occurred in 20.7% (30/145) of telithromycin-treated patients vs. 31.8% (47/148) of amoxicillin-clavulanate-treated patients (p=0.034). One serious AE was reported in the telithromycin group, but it was considered not to be related to treatment.

CONCLUSIONS

This open-label, randomized study demonstrated that treatment of ABS with telithromycin resulted in comparable clinical efficacy, shorter times to symptom resolution, and fewer total TEAEs than treatment with amoxicillin-clavulanate.