Efficacy of clarithromycin against Streptococcus pneumoniae expressing mef(A)-mediated resistance

Amphiphilic p-sulfonatocalix[6]arene based self-assembled nanostructures for enhanced clarithromycin activity against resistant Streptococcus Pneumoniae

Amphiphilic calixarenes are preferred to generate nano-cargos for drugs due to their stability, possibilities for modification and intrinsic host cavities. Here we are reporting the synthesis of amphiphilic calixarene and its evaluation as drug delivery system. Water soluble amphiphilic p-sulfonatocalix[6]arene was synthesized through sulfonation and lipophilic conjugation on its upper and lower rims respectively. The synthesized amphiphile self-assembled into nanostructures in the presence of Clarithromycin and FITC as model hydrophobic drugs followed by a wide range of characterization. Clarithromycin loaded self-assembled nanostructures was screened for its bactericidal potential in resistant S. pneumonia through various in-vitro assays. The amphiphilic calixarene self-assembled into polydispersed nanostructures with 136.45 ± 2.41 nm mean diameter and -49.93 ± 0.35 mV surface charges. The amphiphile was capable to load Clarithromycin (57.54 ± 1.88 %) and fluorescent dye and was highly stable. Clarithromycin loaded nanostructures revealed significant biofilm and bacterial growth inhibition and cell destruction properties. Results authenticate calixarene amphiphile as an efficient nano-carrier for improving Clarithromycin efficacy.

Tigecycline displays in vivo bactericidal activity against extended-spectrum-β-lactamase-producing Enterobacteriaceae after 72-hour exposure period

Progressively enhanced activity of a humanized tigecycline (TGC) regimen was noted over 3 days against an extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli isolate and an ESBL-producing Klebsiella pneumoniae isolate. Bacterial density reduction approximated 3 log(10) approaching bactericidal activity at 72 h. This level of activity has not been previously noted for compounds such as tetracyclines, normally considered bacteriostatic antimicrobials. Extended regimen studies in vivo may aid in better delineation of antimicrobial effects, producing improved correlation with clinical outcomes.

Macrolide and ketolide resistance with Streptococcus pneumoniae

Antimicrobial agents in the macrolide family have long been considered drugs of potential utility in the management of infections caused by Streptococcus pneumoniae. However, with the emergence of macrolide resistance, the clinical value of macrolides in pneumococcal infections is threatened. In part, as a consequence of the development of macrolide resistance, recently the first agent in the ketolide antimicrobial class, telithromycin, was developed and introduced into clinical practice. The ketolides are macrolide antimicrobials whose chemistry has been modified so as avoid the effects of the most common mechanisms of macrolide resistance with S pneumoniae. This discussion reviews the current state of resistance to macrolides and ketolides with S pneumoniae in North America.

Drug-resistant pneumococcal pneumonia: clinical relevance and approach to management

Community-acquired pneumonia is the most common infectious disease that causes death, with Streptococcus pneumoniae remaining the leading causative pathogen. The worldwide incidence of infections caused by pneumococci resistant to penicillin, macrolides, and other antimicrobial agents has increased at an alarming rate during the past 2 decades. Yet, these agents are still used as first-line empirical therapy in the outpatient setting. There are several reasons for this, including the infrequency of making a pathogen-specific diagnosis, the failure of studies to demonstrate the relevance of resistance, and the infrequency with which clinicians recognize clinical failures. Despite this, there is mounting evidence that supports the practice of using high doses of some antimicrobial agents, a more active antimicrobial agent within a class, or switching to another class of antimicrobial agents when a patient is identified as being at an increased risk of infection with a resistant pneumococcus. There is now information that will allow the physician to identify not only the patient at risk for infection with a resistant pneumococcus but also the antimicrobial class and, in some cases, the agent within the class to which the organism is more likely to be resistant. This will allow clinicians to better define optimal therapy for patients with community-acquired pneumonia.

Efficacy of pulsatile amoxicillin and clarithromycin dosing alone and in combination in a murine pneumococcal pneumonia model

OBJECTIVES

Amoxicillin and clarithromycin have been proven to be effective in the treatment of community-acquired pneumonia. This study investigated the in vivo bactericidal efficacy of a novel, pulsatile dosing strategy for amoxicillin and clarithromycin, when used as monotherapy and combination therapy.

METHODS

A neutropenic murine pneumonia model was used to assess the bactericidal activity of amoxicillin and clarithromycin, when the same total daily dose was administered as a traditional regimen (every 8 h and every 12 h, respectively) or as a pulsatile regimen (four doses of antibiotic given every 2 h over the first 6 h of the day) against three isolates of Streptococcus pneumoniae of varying resistance profiles. The three isolates consisted of SP21 (macrolide and penicillin susceptible), SP100 [mef(A) gene], and SP107 [mef(A) + erm(B) genes].

RESULTS

Pulsatile dosing showed similar reductions in bacterial density for amoxicillin and clarithromycin when either drug was given alone compared with traditional dosing regimens against all three bacterial isolates. When amoxicillin and clarithromycin were combined, improved activity was found compared with monotherapy. Overall, when comparing the different combination regimens, the pulsatile regimens provided similar activity compared with the traditional regimens. For one isolate, SP107, pulsatile amoxicillin combination regimens were less effective compared with traditionally dosed amoxicillin combination regimens.

CONCLUSIONS

Pulsatile dosing resulted in comparable bactericidal activity against the three isolates tested and may represent an alternative dosing strategy, which may help to alleviate problems with patient adherence to drug therapy.

Immunomodulatory effects of macrolides: implications for practicing clinicians

Macrolides are regarded as the drugs of choice for the treatment of diffuse panbronchiolitis (DPB) due to their favorable effects on patient outcomes. These drugs decrease sputum production, thereby improving pulmonary function. Moreover, these effects are independent of dosing with respect to clarithromycin, erythromycin, and roxithromycin. The marked success of macrolides in this disease is a direct effect of impeding the inflammatory cascade. With their abilities to reduce the secretion of proinflammatory cytokines, ameliorate the infiltration of inflammatory cells into the airways, and reduce mucus secretion, macrolides are able to improve pulmonary function and quality of life in patients with chronic inflammatory diseases of the airways. Although prolonged use of macrolides raises concerns of increased adverse effects, data do not support such occurrences. With respect to concerns of resistance, it should be noted that in Japan, where macrolides are part of the treatment for DPB, these agents continue to be used effectively as antimicrobial agents. Therefore, the potential benefits of the immunomodulatory effects of macrolides in other conditions such as cystic fibrosis, chronic sinusitis, asthma, and chronic bronchitis are under investigation.