In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to two ketolides (HMR 3004 and HMR 3647), four macrolides (azithromycin, clarithromycin, erythromycin A, and roxithromycin), and two ansamycins (rifampin and rifapentine)

A Comparative Insight on the Newly Emerging Rifamycins: Rifametane, Rifalazil, TNP-2092 and TNP-2198

Rifamycins are considered a milestone for tuberculosis (TB) treatment because of their proficient sterilizing ability. Currently, available TB treatments are complicated and need a long duration, which ultimately leads to failure of patient compliance. Some new rifamycin derivatives, i.e., rifametane, TNP-2092 (rifamycin-quinolizinonehybrid), and TNP-2198 (rifamycin-nitromidazole hybrid) are under clinical trials, which are attempting to overcome the problems associated with TB treatment. The undertaken review is intended to compare the pharmacokinetics, pharmacodynamics and safety profiles of these rifamycins, including rifalazil, another derivative terminated in phase II trials, and already approved rifamycins. The emerging resistance of microbes is an imperative consideration associated with antibiotics. Resistance development potential of microbial strains against rifamycins and an overview of chemistry, as well as structure-activity relationship (SAR) of rifamycins, are briefly described. Moreover, issues associated with rifamycins are discussed as well. We expect that newly emerging rifamycins shall appear as potential tools for TB treatment in the near future.

Pharmacotherapy for Bordetella pertussis infection. I. A synthesis of laboratory sciences

There is considerable history and practice experience both with laboratory susceptibility testing for Bordetella pertussis and clinical treatment. This two-part narrative review provides a synthesis of the laboratory and clinical sciences as they apply to this bacterium and the clinical consequences of treating infection. It is generally held that antibiotic susceptibility testing for B. pertussis is not sufficiently standardised, but there has not been an urgent need to consolidate the same given the lack global experience with major resistance profiles. Experience in China, however, has provided concern for high-level macrolide resistance. The nature of and frequency of such resistance has raised the bar for reconsideration of susceptibility testing given that first-line treatment may be regionally compromised. Disk diffusion and Etest susceptibility testing can be recommended for screening resistance among individual isolates of B. pertussis and on an ad hoc manner. Disk diffusion, Etest and/or critical agar dilution testing can be recommended for large-scale studies. Standards for inoculum, growth atmosphere, timing of interpretation, preferred testing media and controls can be extrapolated from the publications to date. Such methods should be able to detect high-level resistance to several antibiotics, but especially macrolides. Concern for intermediate-susceptible categories requires consideration as well as the correlation with bacteriological and clinical outcomes. Provisional standards can be applied at this time, and modification or fine-tuning of any such standards are open to future investigation.

Widespread Bordetella parapertussis Infections-Wisconsin, 2011-2012: Clinical and Epidemiologic Features and Antibiotic Use for Treatment and Prevention

BACKGROUND

During October 2011-December 2012, concurrent with a statewide pertussis outbreak, 443 Bordetella parapertussis infections were reported among Wisconsin residents. We examined clinical features of patients with parapertussis and the effect of antibiotic use for treatment and prevention.

METHODS

Patients with polymerase chain reaction results positive for B. parapertussis reported during October 2011-May 2012 were interviewed regarding presence and durations of pertussis-like symptoms and receipt of azithromycin treatment. Data regarding acute cough illnesses and receipt of azithromycin prophylaxis among parapertussis patient household members (HHMs) were also collected. Using multivariate repeated measures log-binomial regression analysis, we examined associations of treatment receipt by the HHM with the earliest illness onset and prophylaxis receipt among other HHMs with the presence of any secondary cough illnesses in the household.

RESULTS

Among 218 patients with parapertussis, pertussis-like symptoms were frequently reported. Illness durations were significantly shorter among patients with treatment initiated 0-6 days after cough onset, compared with nonrecipients (median durations: 10 vs 19 days, P = .002). Among 361 HHMs from 120 households, compared with nonrecipients, prompt prophylaxis of HHMs was associated with no secondary cough illnesses (relative risk: 0.16; 95% confidence interval, .04-.69).

CONCLUSIONS

Bordetella parapertussis infection causes pertussis-like illness that might be misclassified as pertussis if B. parapertussis testing is not performed. Prompt treatment might shorten illness duration, and prompt HHM prophylaxis might prevent secondary illnesses. Further study is needed to evaluate antibiotic effectiveness for preventing parapertussis and to determine risks and benefits of antibiotic use.

Surveillance for Transmission and antibiotic Adverse Events Among Neonates and Adults Exposed to a Healthcare Worker With Pertussis

Background:

During a hospital obstetric rotation, a medical student demonstrated classic symptoms of pertussis. The diagnosis was confirmed by isolation ofBordetella pertussis. Because this exposure occurred in a high-risk hospital setting, control measures were undertaken to prevent transmission and illness.

Objectives:

To identify secondary cases of pertussis, to determine compliance with chemoprophylaxis recommendations, and to monitor for adverse events associated with chemoprophylaxis following a hospital exposure to pertussis.

Patients:

More than 500 individuals were potentially exposed, including 168 neonates; antimicrobial chemoprophylaxis was administered to 281 individuals. Fifty-eight neonates and 194 adults began azithromycin chemoprophylaxis; 18 neonates and 2 adults began erythromycin chemoprophylaxis.

Methods:

Active surveillance was instituted for (1) secondary cases of pertussis among healthcare coworkers, obstetric patients, their neonates, and labor companions and (2) antibiotic compliance and tolerance.

Results:

No secondary cases of pertussis were confirmed by laboratory tests; however, 26 suspected cases and 5 clinically compatible cases were identified. Antibiotic courses were completed by 95% of the individuals who initiated therapy. Neonates taking azithromycin had statistically significantly less gastrointestinal distress compared with neonates taking erythromycin (12% vs 50%;P= .002); there were no cases of infantile hypertrophic pyloric stenosis.

Conclusions:

Although it was not possible to assess the effectiveness of the antibiotic regimens, the lack of laboratory-confirmed secondary cases suggests control measures were successful. Data from the 58 neonates who received azithromycin suggest it may be well tolerated in this age group.

The First Macrolide-Resistant Bordetella pertussis Strains Isolated From Iranian Patients

Background:

Whooping cough was considered as one of the major causes of childhood morbidity and mortality worldwide. Resistant isolates of Bordetella pertussis to macrolides in some countries have been recently reported.

Objectives:

Recent reports on macrolide-resistant B. pertussis isolates and lack of evidence for such resistance in clinical isolates of the Iranian patients led the authors of the current study to study antibiotic susceptibility of the collected isolates in the country. Susceptibility of the B. pertussis isolates to three antibiotics was studied. Relatedness of the strains recovered in this research was also examined.

Materials and Methods:

The antibacterial activities of erythromycin, azithromycin, and clarithromycin antibiotics against the recovered isolates of 779 nasopharyngeal swabs were examined using MIC (Minimum Inhibitory Concentration) method. Relationship of the strains was characterized by Pulsed-field Gel Electrophoresis (PFGE).

Results:

Among the specimens, 11 cases (1.4%) were culture-positive. Among these isolates, only two isolates had high MIC values for erythromycin and clarithromycin. Pulsed-field gel electrophoresis analysis of the isolates revealed 6 PFGE profiles (A-F) among which three and two isolates had the same patterns in profiles A and B, respectively.

Conclusions:

Azithromycin can be a good drug of choice to treat patients infected by B. pertussis in Iran. Clonal relationship of the isolates showed that the same B. pertussis strains were isolated from different patients in Iran.

[Cases of pertussis among healthcare workers in a maternity ward: management of a health alert]

Pertussis is a highly contagious acute respiratory tract infection, with a poor prognosis in non-vaccinated new-borns.

OBJECTIVES

The authors had for aim to investigate an epidemic of 5 pertussis cases among health care workers (HCW) in our maternity ward with potential exposure of new-borns and to evaluate HCW compliance and experience gain.

METHODS

A retrospective study was made using a questionnaire with HCW on preventive measures taken (antibiotic prophylaxis with erythromycin and wearing a mask).

RESULTS

Two hundred and thirty-eight patients were warned of a potential pertussis contamination. No nosocomial case was detected among patients or their new borns. Ten proved or probable cases were identified among 101 HCW having answered (N=101/210, 48%). Sixty percent of HCW people followed the antibiotic treatment and 85% wore a mask among whom 46% adequately. Non-compliance factors were mainly related to adverse effects (41%), delayed information (41%), and false vaccine protection (22%). Crisis communication was felt as unsatisfactory for 72% of HCW and recommendations not adapted for 39% of the staff.

CONCLUSION

This survey points out the difficulty of managing a pertussis alert in a medical ward.

Antibiotics for treatment of resistant gram-positive coccal infections

Vancomycin is considered the workhorse for the treatment of most drug-resistant gram-positive bacterial infections. However, concerns have been raised regarding the increasing rates of vancomycin-resistant enterococci and the clinical shortcomings of vancomycin in the treatment of invasive Staphylococcus aureus infections. Resources have been committed to the development of antimicrobial agents with activity against these organisms. This review will focus on the newer antibacterial agents that have been developed for the treatment of resistant gram-positive pathogens. Included in this review are the agents: quinupristin-dalfopristin, linezolid, daptomycin, telithromycin, and tigecycline.

Telithromycin new product overview

Community-acquired respiratory tract infections (CARTIs), including community-acquired pneumonia, acute exacerbations of chronic bronchitis, and acute bacterial sinusitis, contribute substantially to health care costs in the United States. Although many prescriptions for antibiotics are written each year for the treatment of CARTIs, most are prescribed on an empiric basis. Concerns about the increasing prevalence of antimicrobial resistance and the changing pattern of pathogens isolated from subjects with CARTIs have raised questions about the empiric treatment paradigm. When choosing appropriate antimicrobial therapy for CARTIs, physicians must consider not only the spectrum of activity of antibiotics but also the potential risk of resistance. Telithromycin is the first member of the ketolide class, a new family of antimicrobials structurally related to the macrolides, to be approved by the US Food and Drug Administration for the treatment of CARTIs. The spectrum of activity of telithromycin includes common typical and atypical causative pathogens associated with community-acquired respiratory tract infections, including antibiotic-resistant strains of Streptococcus pneumoniae. Clinical trials have shown that telithromycin is as effective as traditionally used antimicrobial agents in the treatment of mild-to-moderate community-acquired pneumonia, acute exacerbations of chronic bronchitis, and acute bacterial sinusitis.

The ketolides: a critical review

Ketolides are a new class of macrolides designed particularly to combat respiratory tract pathogens that have acquired resistance to macrolides. The ketolides are semi-synthetic derivatives of the 14-membered macrolide erythromycin A, and retain the erythromycin macrolactone ring structure as well as the D-desosamine sugar attached at position 5. The defining characteristic of the ketolides is the removal of the neutral sugar, L-cladinose from the 3 position of the ring and the subsequent oxidation of the 3-hydroxyl to a 3-keto functional group. The ketolides presently under development additionally contain an 11, 12 cyclic carbamate linkage in place of the two hydroxyl groups of erythromycin A and an arylalkyl or an arylallyl chain, imparting in vitro activity equal to or better than the newer macrolides. Telithromycin is the first member of this new class to be approved for clinical use, while ABT-773 is presently in phase III of development. Ketolides have a mechanism of action very similar to erythromycin A from which they have been derived. They potently inhibit protein synthesis by interacting close to the peptidyl transferase site of the bacterial 50S ribosomal subunit. Ketolides bind to ribosomes with higher affinity than macrolides. The ketolides exhibit good activity against Gram-positive aerobes and some Gram-negative aerobes, and have excellent activity against drug-resistant Streptococcus pneumoniae, including macrolide-resistant (mefA and ermB strains of S. pneumoniae). Ketolides such as telithromycin display excellent pharmacokinetics allowing once daily dose administration and extensive tissue distribution relative to serum. Evidence suggests the ketolides are primarily metabolised in the liver and that elimination is by a combination of biliary, hepatic and urinary excretion. Pharmacodynamically, ketolides display an element of concentration dependent killing unlike macrolides which are considered time dependent killers. Clinical trial data are only available for telithromycin and have focused on respiratory infections including community-acquired pneumonia, acute exacerbations of chronic bronchitis, sinusitis and streptococcal pharyngitis. Bacteriological and clinical cure rates have been similar to comparators. Limited data suggest very good eradication of macrolide-resistant and penicillin-resistant S. pneumoniae. As a class, the macrolides are well tolerated and can be used safely. Limited clinical trial data suggest that ketolides have similar safety profiles to the newer macrolides. Telithromycin interacts with the cytochrome P450 enzyme system (specifically CYP 3A4) in a reversible fashion and limited clinically significant drug interactions occur. In summary, clinical trials support the clinical efficacy of the ketolides in upper and lower respiratory tract infections caused by typical and atypical pathogens including strains resistant to penicillins and macrolides. Considerations such as local epidemiology, patterns of resistance and ketolide adverse effects, drug interactions and cost relative to existing agents will define the role of these agents. The addition of the ketolides in the era of antibacterial resistance provides clinicians with more options in the treatment of respiratory infections.

Telithromycin: the first of the ketolides

OBJECTIVE

To review the chemistry, spectrum of activity, pharmacology, clinical efficacy, and safety of telithromycin.

DATA SOURCES

A MEDLINE search from 1966 to December 2000 was performed via OVID and PubMed using the following search terms: HMR 3647, HMR3647, Ketek, RU 66647, and telithromycin. An extensive review of retrieved literature, abstracts from international scientific conferences, and minutes from regulatory authority meetings was also performed.

DATA EXTRACTION

Medicinal chemistry, in vitro, animal, and human trials were reviewed for information on the antimicrobial activity, clinical efficacy, pharmacology, and safety of telithromycin.

DATA SYNTHESIS

Several chemical modifications to the macrolide structure have led to the development of telithromycin, the first ketolide antimicrobial that demonstrates improved activity against penicillin- and macrolide/azalide-resistant Streptococcus pneumoniae due to its unique binding to the ribosomal target site. Although telithromycin may be useful in the treatment of community-acquired respiratory tract infections due to its activity against common typical and atypical pathogens, questions concerning its reliable activity against Haemophilus influenzae need to be addressed. Telithromycin's pharmacokinetics permit once-daily dosing for abbreviated periods and good distribution into lung tissue and phagocytic cells. Clinical and bacteriologic cure rates have been similar to those of comparator agents in human efficacy trials; however, the incidence of adverse gastrointestinal events were generally higher with telithromycin patients. Like other macrolides and many newer fluoroquinolones, telithromycin's ability to prolong the QTc interval is a potential safety issue, especially in elderly patients with predisposing conditions or those who are concurrently receiving drugs that are substrates for CYP2D6 and 3A4. Liver function test elevations demonstrated during clinical trials, although not overtly severe, may warrant monitoring in some patients taking multiple hepatically metabolized/cleared agents.

CONCLUSIONS

Telithromycin offers potential advantages over traditional macrolides/azalides for community-acquired respiratory tract infections caused by macrolide-resistant pathogens. Further studies are needed to elucidate its clinical efficacy against H. influenzae, potential drug interactions, and safety in various subpopulations.

Telithromycin: an oral ketolide for respiratory infections

The ketolides represent a new subclass of antibiotics among the macrolide-lincosamide-streptogramin group. Telithromycin, the first ketolide to be awarded approvable status for clinical use, demonstrates in vitro activity against community-acquired respiratory pathogens including penicillin- and erythromycin-resistant Streptococcus pneumoniae. An extended half-life permits once-daily oral administration. Telithromycin is a substrate for cytochrome P450 (CYP) 3A4 and also inhibits drugs metabolized by CYP3A4. A relatively high frequency of mild-to-moderate gastrointestinal adverse effects has been reported. Similar clinical and microbiologic efficacy has been demonstrated with oral dosing in comparative clinical trials for community-acquired pneumonia, acute sinusitis, acute exacerbations of chronic bronchitis, and pharyngitis. Although limited data on penicillin-resistant S. pneumoniae and erythromycin-resistant Streptococcus pyogenes are available from clinical trials, this drug appears promising for respiratory infections caused by these pathogens.

Current pharmacotherapy of pertussis

Human infection with Bordetella pertussis and Bordetella parapertussis causes significant morbidity and mortality. While universal immunisation represents the mainstay of prevention, the purpose of this review is to summarise the current options for antimicrobial chemotherapy of pertussis. Several chemotherapeutic approaches have an important place in therapy and in infection control. Supportive treatment including nasopharyngeal suction, oxygen and parenteral fluids, is essential for infants < 1 year who are at greatest risk of complications and permanent sequelae. Steroids and beta2-agonists are also used in the management of severe neonatal pertussis. Several antibiotics have been shown to reduce the level of bacterial colonisation of the respiratory tract, however, erythromycin is accepted to be the treatment of choice. Erythromycin reduces severity and duration of disease, even if started during the paroxysmal phase. A 14 day course is recommended although side effects may limit compliance; a recent study indicates that a 7 day course may have similar efficacy in terms of eradication and prevention of relapse. Alternatives to erythromycin are clarithromycin, azithromycin and trimethoprim-sulfamethoxazole. Fluoroquinolones have good in vitro activity against both B. pertussis and B. parapertussis and may be useful in the treatment of adult patients with pertussis, although there are no supporting clinical data at present. Erythromycin prophylaxis is also recommended for close household contacts of patients with pertussis.

Telithromycin: a new ketolide antimicrobial for treatment of respiratory tract infections

Telithromycin is a new ketolide antimicrobial, specifically developed for the treatment of community-acquired respiratory tract infections. It has a wide spectrum of antibacterial activity against common respiratory pathogens including Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pyogenes. It also has activity against atypical pathogens, such as Chlamydia pneumoniae, Legionella pneumophila and Mycoplasma pneumoniae. Telithromycin maintains activity against beta-lactam and macrolide-resistant respiratory tract pathogens and does not appear to induce cross-resistance to other members of the macrolide-lincosamide-streptogramin (MLS) group of antimicrobials. It demonstrates bactericidal activity against S. pneumoniae and H. influenzae and has a prolonged concentration-dependent post-antibiotic effect (PAE) in vitro. The drug has favourable pharmacokinetics following oral administration. It is well absorbed, achieves good plasma levels and is highly concentrated in pulmonary tissues and white blood cells. In clinical trials, telithromycin given orally at a dose of 800 mg once daily for 5 - 10 days was as effective as comparator antimicrobials for the treatment of adults with community-acquired pneumonia, acute exacerbations of chronic bronchitis, acute maxillary sinusitis and group A-beta-haemolytic streptococcal pharyngitis or tonsillitis. The adverse events and safety profile were similar to comparator antimicrobials. The most common adverse events were diarrhoea, nausea, headache and dizziness. Telithromycin should provide an effective, convenient and well-tolerated once-daily oral therapy for treatment of respiratory infections.

In vitro activities of the ketolides telithromycin (HMR 3647) and HMR 3004 compared to those of clarithromycin against slowly growing mycobacteria at pHs 6.8 and 7.4

The in vitro activities of HMR 3647 (telithromycin) and HMR 3004, two novel semisynthetic ketolides, were investigated and compared with that of the reference macrolide drug, clarithromycin, against 34 strains of slowly growing mycobacteria at pHs 6.8 and 7.4, as determined radiometrically. The MICs at pH 7.4 were about 1 to 2 dilutions lower than those observed at pH 6.8. In terms of the highest to the lowest activity, the three antibiotics could be classified as follows: clarithromycin > HMR 3004 > HMR 3647. Among the species tested, Mycobacterium bovis BCG, M. ulcerans, M. avium, and M. paratuberculosis were moderately susceptible to HMR 3004 and HMR 3647 (MICs at pH 7.4, < or =5.0 and < or =20.0 microg/ml, respectively, versus < or =1.25 microg/ml for clarithromycin), whereas M. tuberculosis, M. africanum, M. bovis, and M. simiae were resistant (MICs, > or =10.0 and > or =40.0 microg/ml, respectively, at pH 7.4). Although not more active than clarithromycin in vitro, the high level of intracellular accumulation of the two ketolides inside phagocytes warrants further screening in experimental animal models.

Azithromycin: indications for the future?

The global challenge of optimally treating bacterial infections is continuously evolving. Azithromycin, the first azalide antibiotic, presents pharmacokinetics and pharmacodynamics that allow for a simple dosing regimen with minimal side effects. Current azithromycin uses include a variety of community-acquired respiratory tract, skin and soft tissue, and sexually transmitted disease infections. Azithromycin has also demonstrated substantial activity against atypical organisms such as Mycobacterium avium complex (MAC) and Chlamydia trachomatis. Due to a never-ending need for new antibiotic therapies, several other potential indications for azithromycin are being researched. This article will present various current research associated with azithromycin's potential use for malaria, trachoma, coronary artery disease (CAD), Pseudomonas aeruginosa infections, erythema migrans, short-term therapy for respiratory infections, typhoid, cryptosporidiosis, pelvic inflammatory disease, acne, Mediterranean spotted fever and MAC. As bacterial and parasite resistance patterns fluctuate globally, azithromycin may be an alternative therapy for the previously mentioned indications, which will also enhance patient compliance and therefore effectively eradicate infection worldwide.

Recent developments in macrolides and ketolides

Emergence of bacterial resistance to macrolide antibiotics, particularly in Gram-positive bacteria, has been observed. Novel macrolides having C-4" carbamate functional groups and ketolides, the 3-keto derivatives of macrolides, have been found to have activities against macrolide-resistant strains. Several potential non-antibacterial activities of macrolides have been reported, such as inhibition of cytokine production, neutrophil attachment to human bronchial epithelial cells and vesicular transport.