Activity of new macrolides against Bordetella pertussis and Bordetella parapertussis

Occupational Health Update: Evaluation and Management of Exposures and Postexposure Prophylaxis

Health care personnel (HCP) are at risk of exposure to infectious agents depending on their job duties and other factors. Risks include percutaneous exposure to blood-borne pathogens via sharp injuries (eg, human immunodeficiency virus, hepatitis B virus, hepatitis C virus); exposure by direct contact, droplet, or airborne transmission of pathogens through direct patient care (eg, pertussis, invasive meningococcus infections, tuberculosis); and through indirect contact transmission related to the contaminated health care environment (eg, Clostridioides difficile). Occupational health programs must effectively identify and respond to potential exposures and provide guidance to HCP on postexposure prophylaxis.

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.

Neurologic alterations in an HIV adult patient with pertussis: a case report

Background

Pertussis is a highly contagious disease of public health interest caused by the bacterium Bordetella pertussis. Although its incidence has decreased substantially after the introduction of a vaccination, the burden of the disease remains high. Although the paroxysmal phase is highly disabling, complications are uncommon and more prevalent in children than in adults. The most frequent neurological complication is encephalopathy, but seizures, paresis, paraplegia, ataxias, aphasias, and decerebration postures have also been described. The complication of decerebration postures has not been previously reported in adults.

Case presentation

We present a video case of an adult HIV patient with severe coughing paroxysms, post-tussive emesis and syncope, whose workup confirmed the diagnosis of a B. pertussis respiratory infection. During hospitalization, he had fluctuant encephalopathy and post-tussive decerebration postures following paroxysms. He was treated with antibiotic therapy and finally sent home without residual neurological deficits.

Conclusion

This case illustrates the biological plausibility of neurologic complications of pertussis in adults, which, albeit rare, can cause important morbidities. Future research should explore whether there are differences in the clinical presentation, risk factors and pathophysiology of the disease among adults or interventions aimed at preventing or treating pertussis encephalopathy.

Occupational Health Update: Focus on Preventing the Acquisition of Infections with Pre-exposure Prophylaxis and Postexposure Prophylaxis

Health care personnel are commonly exposed to infectious agents via sharp injuries (eg, human immunodeficiency virus, hepatitis B virus, and hepatitis C virus), direct patient care (eg, pertussis and meningococcus), and the contaminated environment (eg, Clostridium difficile). An effective occupational program is a key aspect of preventing acquisition of an infection by offering the following: (1) education of health care personnel regarding proper handling of sharps, early identification and isolation of potentially infectious patients, and hand hygiene; (2) assuring immunity to vaccine-preventable diseases; and, (3) immediate availability of a medical evaluation after a nonprotected exposure to an infectious disease.

Pertussis post-exposure prophylaxis among household contacts: a cost-utility analysis

Background

Recent pertussis outbreaks have prompted re-examination of post-exposure prophylaxis (PEP) strategies, when immunization is not immediately protective. Chemoprophylaxis is recommended to household contacts; however there are concerns of clinical failure and significant adverse events, especially with erythromycin among infants who have the highest disease burden. Newer macrolides offer fewer side effects at higher drug costs. We sought to determine the cost-effectiveness of PEP strategies from the health care payer perspective.

Methods

A Markov model was constructed to examine 4 mutually exclusive strategies: erythromycin, azithromycin, clarithromycin, or no intervention, stratified by age group of contacts (“infant”, “child”, and “adult”). Transition probabilities, costs and quality-adjusted life years (QALYs) were derived from the literature. Chronic neurologic sequelae were modeled over a lifetime, with costs and QALYs discounted at 5%. Associated health outcomes and costs were compared, and incremental cost-effectiveness ratios (ICER) were calculated in 2012 Canadian dollars. Deterministic and probabilistic sensitivity analyses were performed to evaluate the degree of uncertainty in the results.

Findings

Azithromycin offered the highest QALYs in all scenarios. While this was the dominant strategy among infants, it produced an ICER of $16,963 per QALY among children and $2,415 per QALY among adults. Total QALYs with azithromycin were 19.7 for a 5-kg infant, 19.4 for a 10-year-old child, and 18.8 for a 30-year-old adult. The costs of azithromycin PEP among infants, children and adults were $1,976, $132 and $90, respectively. While results were sensitive to changes in PEP effectiveness (11% to 87%), disease transmission (variable among age groups) and hospitalization costs ($379 to $59,644), the choice of strategy remained unchanged.

Interpretation

Pertussis PEP is a cost-effective strategy compared with no intervention and plays an important role in contact management, potentially in outbreak situations. From a healthcare payer perspective, azithromycin is the optimal strategy among all contact groups.

Pertussis immunisation in adolescents and adults –Bordetella pertussisepidemiology should guide vaccination recommendations

Pertussis, or whooping cough, is an infectious disease that is caused by Bordetella pertussis, affects all age groups and is vaccine preventable. Recently, an increase in reported cases of pertussis in adolescents and adults has been noted in many countries despite high immunisation rates in children. Today pertussis outnumbers all other paediatric vaccine-preventable diseases in some countries. This observation can best be explained by an increased awareness of the disease, the availability of new diagnostic tests and, perhaps, suboptimal efficacy of some pertussis vaccines. In general, B. pertussis infections in adolescents and adults are of concern as they are the most important source of transmission of B. pertussis infections to young, unprotected infants. Many studies with diphtheria and tetanus toxoid, acellular pertussis component combination vaccines, specifically designed for use in adolescents and adults, have been performed and excellent tolerability and immunogenicity have been demonstrated. With the availability of two such products, booster doses in adolescents have been introduced in Canada, Austria, Australia, France, Germany and the US, and many other countries are considering similar expansion of their immunisation programmes at present. In addition, universal immunisation of adults (Austria, every 10 years) or targeting high risk groups (e.g., parents of newborns and other care-givers to children; Germany) have been recommended. If lifelong regular booster doses against pertussis were to be recommended and universal implementation was obtained, the authors believe that the morbidity of pertussis and its spread to infants can be dramatically reduced, and it is possible that the circulation of B. pertussis could be eliminated.

Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies

Bordetella respiratory infections are common in people (B. pertussis) and in animals (B. bronchiseptica). During the last two decades, much has been learned about the virulence determinants, pathogenesis, and immunity of Bordetella. Clinically, the full spectrum of disease due to B. pertussis infection is now understood, and infections in adolescents and adults are recognized as the reservoir for cyclic outbreaks of disease. DTaP vaccines, which are less reactogenic than DTP vaccines, are now in general use in many developed countries, and it is expected that the expansion of their use to adolescents and adults will have a significant impact on reducing pertussis and perhaps decrease the circulation of B. pertussis. Future studies should seek to determine the cause of the unique cough which is associated with Bordetella respiratory infections. It is also hoped that data gathered from molecular Bordetella research will lead to a new generation of DTaP vaccines which provide greater efficacy than is provided by today's vaccines.

Azithromycin prophylaxis during a hospitalwide outbreak of a pertussis-like illness

A questionnaire regarding tolerability and adherence was administered for 5 days to hospital employees who received azithromycin prophylaxis during a hospitalwide outbreak of a pertussis-like illness. Analysis of the 239 responses from those having received prophylactic azithromycin determined that it was well tolerated and accounted for a minimal loss of days worked; 81.5% were fully adherent with the regimen.

Efficacy and safety of clarithromycin versus erythromycin for the treatment of pertussis: a prospective, randomized, single blind trial

BACKGROUND

Pertussis is still a prevalent public health problem, and antibiotic therapy may decrease disease severity and limit communicability. Erythromycin is the recommended antibiotic for treatment and prophylaxis of pertussis; however, side effects of erythromycin limit its usefulness in some patients. Clarithromycin, a newer macrolide, has good in vitro activity against Bordetella pertussis and a better side effect profile.

GOALS OF THE STUDY

To compare the microbiologic and clinical efficacy and the clinical safety of a 7-day course of clarithromycin vs. a 14-day course of erythromycin in children with pertussis.

DESIGN

Prospective, randomized, single blind (investigator), parallel group trial.

METHODS

Children from 1 month to 16 years of age presenting with a clinically defined pertussis syndrome were eligible for the study. After obtaining informed written consent, we randomized patients to receive either clarithromycin (7.5 mg/kg/dose twice a day for 7 days) or erythromycin (13.3 mg/kg/dose three times a day for 14 days). Nasopharyngeal cultures for B. pertussis were performed at enrollment and after end of treatment. Clinical assessments were performed at enrollment, at end of treatment and at a 1-month follow-up visit. Adverse event data were collected throughout the study.

RESULTS

The clarithromycin (n = 76) and erythromycin (n = 77) groups were well-matched for age and previous pertussis immunization. Microbiologic eradication and clinical cure rates were 100% (31 of 31) for clarithromycin and 96% (22 of 23) for erythromycin. The clarithromycin group had significantly fewer adverse events [45% (34 of 76) for clarithromycin vs. 62% (48 of 77) for erythromycin; P = 0.035], and compliance with the medication regimen was significantly higher in these patients.

CONCLUSIONS

A 7-day regimen of clarithromycin and a 14-day course of erythromycin were equally effective for treatment of pertussis. Clarithromycin was better tolerated than conventional erythromycin therapy.

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)

When tested by agar dilution on Mueller-Hinton agar supplemented with 5% horse blood, the ketolides HMR 3004 and HMR 3647 were slightly more active (MIC at which 90% of the isolates were inhibited [MIC90], 0.03 microg/ml) against Bordetella pertussis than azithromycin, clarithromycin, erythromycin A, and roxithromycin. Azithromycin (MIC90, 0.06 microg/ml) was the most active compound against B. parapertussis. Rifampin and rifapentine were considerably less active.

Macrolide antibiotics

This article is an extensive review of current information available on the macrolide antibiotics. This includes antimicrobial spectrum, pharmacology, complications and side effects, and pediatric use of these drugs. These are important antibiotics, but careful selection of patients must be made and the physician must be alert for evidence of drug-drug interactions, which are not uncommon with several members of this class.

Frontiers of occupational health. New vaccines, new prophylactic regimens, and management of the HIV-infected worker

New prophylactic or treatment options are available for a number of infectious diseases that may be transmitted in the health care setting. Infectious diseases that can now be prevented by vaccination of the employee include hepatitis A, pertussis, hepatitis B, and primary varicella. New prophylactic or treatment regimens are available for Neisseria meningitidis, Streptococcus pyogenes, and Bordetella pertussis; treatment of multidrug-resistant tuberculosis is also discussed. Finally, management of the HIV-infected health care worker is reviewed.

Comparison of Etest and agar dilution for testing the activity of three macrolides against Bordetella parapertussis

Agar dilution and Etest using Mueller-Hinton II agar supplemented with 5% whole defibrinated horse blood were compared for testing the activities of azithromycin, clarithromycin, and erythromycin against 34 clinical isolates of the fastidious species Bordetella parapertussis. There was good overall agreement (100.0% within +/- 1 log2 dilution step) between both methods. The Etest offers an excellent and convenient alternative to agar dilution for testing the activities of macrolides against B. parapertussis.

Efficacy of short-term treatment of pertussis with clarithromycin and azithromycin

The recommended treatment for pertussis is erythromycin, 40 to 50 mg/kg per day for 2 weeks. The newly developed macrolides, clarithromycin and azithromycin, have been demonstrated to be superior to erythromycin because of improved absorption and a longer half-life. As a result, we conducted two separate comparison studies to evaluate the efficacies of clarithromycin, 10 mg/kg per day, twice a day for 7 days, and azithromycin, 10 mg/kg per day, once a day for 5 days, compared with the standard erythromycin regimen. A total of 17 patients, including 10 infants 1 year of age or less, for whom pertussis had been confirmed by culture, were allocated to receive either clarithromycin or azithromycin treatment, and each patient was matched (age, sex, and immunization status) with historical control subjects who had been treated with erythromycin. Eradication rates examined at 1 week after treatment were as follows: 9 of 9 with clarithromycin versus 16 of 18 with erythromycin (psi M-H = 1.13), and 8 of 8 with azithromycin versus 13 of 16 with erythromycin (psi M-H = 1.23). No bacterial relapse after treatment was detected in either group. All isolated strains of Bordetella pertussis were susceptible to clarithromycin, azithromycin, and erythromycin, and no change in drug susceptibility has been confirmed for the past 20 years in Japan. Because of the very low incidence of pertussis resulting from widespread use of acellular pertussis vaccination, this study did not enroll a large number of patients; however we conclude that short-term treatment with clarithromycin or azithromycin is expected to be equal or superior to the standard long-term erythromycin regimen for pertussis.

Dirithromycin: a new macrolide

OBJECTIVE

To review the clinical microbiology and therapeutic use of dirithromycin, emphasizing comparative data between dirithromycin and the standard macrolide erythromycin, as well as clarithromycin and azithromycin.

DATA SOURCES

A MEDLINE search of English-language literature during the years 1966-1996, and an extensive review of journals were conducted to prepare this article.

DATA EXTRACTION

The data on pharmacokinetics, adverse effects, and drug interactions were obtained from open and controlled studies. Controlled single- or double-blind studies were evaluated to assess the efficacy of dirithromycin in the treatment of various upper and lower respiratory tract infections, as well as skin and soft tissue infections.

DATA SYNTHESIS

The spectrum of activity of dirithromycin is similar to that of erythromycin, clarithromycin, or azithromycin, with some notable exceptions. Dirithromycin was more active in vitro against Campylobacter jejuni and Borrelia burgdorferi than was erythromycin or clarithromycin, but in general demonstrated less activity than erythromycin, clarithromycin, or azithromycin against a majority of microorganisms. The pharmacokinetic profile of dirithromycin offers the advantages of once-daily dosing and high and prolonged tissue concentrations; dosing adjustments are not needed in the elderly or in patients with renal or mild hepatic impairment. Clinical efficacy and bacteriologic eradication rates with dirithromycin and erythromycin are comparable for the treatment of respiratory and skin and soft tissue infections due to susceptible pathogens. Dirithromycin appears to have adverse effect profiles similar to those of the other macrolides, with reported problems most often related to the gastrointestinal tract. Dirithromycin does not seem to cause clinically important interactions with drugs such as theophylline, oral contraceptives, cyclosporine, or terfenadine.

CONCLUSIONS

Dirithromycin offers some attractive pharmacokinetic properties. The long elimination half-life of dirithromycin allows once-daily dosing and higher and more prolonged tissue concentrations than are achievable with erythromycin. The spectrum of activity, adverse effect profile, clinical efficacy, and bacteriologic eradication rate of dirithromycin may be similar to those of erythromycin. No significant drug interactions with dirithromycin have been reported. Based on available data, dirithromycin may not offer any unique clinical advantage over clarithromycin or azithromycin. Future clinical trials may reveal a special role for dirithromycin in patient care.

In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to four fluoroquinolones (levofloxacin, d-ofloxacin, ofloxacin, and ciprofloxacin), cefpirome, and meropenem

The in vitro activities of levofloxacin, ofloxacin, d-ofloxacin, ciprofloxacin, cefpirome, and meropenem against 34 clinical isolates each of Bordetella pertussis and Bordetella parapertussis were determined by agar dilution on Mueller-Hinton agar supplemented with 5% horse blood. Levofloxacin was as active as ciprofloxacin against both species (MIC, 0.06 microgram/ml) and more active than ofloxacin and d-ofloxacin. Cefpirome was more active against B. pertussis (MIC, 1.0 microgram/ml) than against B. parapertussis (MIC, > 2 micrograms/ml), while the reverse was true for meropenem (MIC, 2.0 micrograms/ml against B. pertussis and 1.0 microgram/ml against B. parapertussis).

Comparison of media for agar dilution susceptibility testing of Bordetella pertussis and Bordetella parapertussis

Antimicrobial susceptibility testing of the fastidious species Bordetella pertussis and Bordetella parapertussis is not standardized. In an attempt to find the optimal medium for agar dilution testing, the activity of erythromycin against Bordetella pertussis and Bordetella parapertussis (34 isolates each) was assessed using homologous broth/agar combinations of Bordet-Gengou, charcoal, Iso-Sensitest (Oxoid) and Mueller-Hinton media. Each medium was supplemented with 5% and 20% whole defibrinated horse blood. Mueller-Hinton medium supplemented with 5% horse blood performed best overall.

Roxithromycin. An update of its antimicrobial activity, pharmacokinetic properties and therapeutic use

Roxithromycin is a derivative of the macrolide antibacterial erythromycin with in vitro antibacterial activity resembling that of the parent compound. The drug has activity against some Staphylococcus spp., many Streptococcus spp., Moraxella (Branhamella) catarrhalis, Mycoplasma pneumoniae, Legionella pneumophila and Chlamydia trachomatis as well as many less common organisms. Measured using recently proposed guidelines, roxithromycin has in vitro activity against Haemophilus influenzae. In comparison with that of its parent compound, the pharmacokinetic profile of roxithromycin is characterised by high plasma, tissue and body fluid concentrations and a long half-life permitting an extended dosage interval. Roxithromycin has proven clinical efficacy in upper and lower respiratory infections, skin and soft tissue infections, urogenital infections and orodental infections, and appears to be as effective as more established treatments including erythromycin, amoxicillin/clavulanic acid and cefaclor. The drug has also shown promise in a variety of more specialised indications including opportunistic infections in human immunodeficiency virus (HIV)-positive patients and as part of a Helicobacter pylori eradication regimen. Roxithromycin is very well tolerated with an overall incidence of adverse events of approximately 4%. Thus, roxithromycin is an attractive therapeutic alternative in its established indications, especially when the option of once-daily administration is considered.

Clarithromycin clinical pharmacokinetics

Clarithromycin is a semisynthetic macrolide antibiotic, structurally related to erythromycin. It has a more favourable pharmacokinetic profile than erythromycin, thus allowing twice-daily administration and possibly increasing compliance among outpatients. Clarithromycin is well absorbed from the gastrointestinal tract and its systemic bioavailability (about 55%) is reduced because of first-pass metabolism. It undergoes rapid biodegradation to produce the microbiologically active 14-hydroxy-(R)-metabolite. The maximum serum concentrations of clarithromycin and its 14-hydroxy metabolite, following single oral doses, are dose proportional and appear within 3 hours. With multiple doses, steady-state concentrations are attained after 5 doses and the maximal serum concentrations of clarithromycin and of the 14-hydroxy derivative appear within 2 hours after the last dose. Clarithromycin is well distributed throughout the body and achieves higher concentrations in tissues than in the blood. Also, the 14-hydroxy metabolite exhibits high tissue concentrations, with values about one-third of the parent compound concentrations. The presence of food appears to have no clinically significant effect on clarithromycin pharmacokinetics. The main metabolic pathways are oxidative N-demethylation and hydroxylation, which are saturable and result in nonlinear pharmacokinetics. The primary metabolite (14-hydroxy derivative) is mainly excreted in the urine with the parent compound. A reduction in urinary clearance in the elderly and in patients with renal impairment is associated with an increase in area under the plasma concentration-time curve, peak plasma concentrations and elimination half-life. Mild hepatic impairment does not significantly modify clarithromycin pharmacokinetics. In conclusion, clarithromycin, because of its antibacterial activity and pharmacokinetic properties, appears to be a useful alternative to other macrolides in the treatment of community acquired infections.

Clarithromycin in the treatment of skin and skin structure infections: two multicenter clinical studies. Clarithromycin Study Group

BACKGROUND

Clarithromycin is a new macrolide analog of erythromycin with activity against a number of dermatologic pathogens.

METHODS

The efficacy and safety of clarithromycin, 250 mg bid, were compared with those of reference drugs, cefadroxil and erythromycin, in two multicenter studies: (1) a randomized, double-blind 45-center study, in which clarithromycin or cefadroxil 500 mg bid was given for 5-14 days; and (2) a single-blind 31-center study, in which clarithromycin or erythromycin, 250 mg qid, was given for < or = 14 days.

RESULTS

In the first study, efficacy and safety were evaluated in 299 and 538 patients, respectively. In the second study, the numbers were 141 and 261 patients, respectively. Overall, clarithromycin was as effective and safe as cefadroxil and erythromycin.

CONCLUSIONS

Clarithromycin provides an alternative therapy to cefadroxil and erythromycin for skin and skin structure infections, especially in beta-lactam allergic patients.

Semi-synthetic derivatives of erythromycin

Semi-synthetic derivatives of erythromycin have played an important role in antimicrobial chemotherapy. First generation derivatives such as 2'-esters and acid-addition salts significantly improved the chemical stability and oral bioavailability of erythromycin. A second generation of erythronolide-modified derivatives: roxithromycin, clarithromycin, azithromycin, dirithromycin and flurithromycin, have been synthesized and have exhibited significant improvements in pharmacokinetic and/or microbiological features. In addition, erythromycin itself has expanded its utility as an effective antibiotic against a variety of newly emerged pathogens. As a result of these developments, macrolide antibiotics have enjoyed a resurgence in clinical interest and use during the past half-dozen years, and semi-synthetic derivatives of erythromycin should continue to be important contributors to this macrolide renaissance. Despite these recent successes, other useful niches for macrolide antibiotics will remain unfilled. Consequently, the search for new semi-synthetic derivatives of erythromycin possessing even better antimicrobial properties should be pursued.

Azithromycin. A review of its antimicrobial activity, pharmacokinetic properties and clinical efficacy

Azithromycin is an acid stable orally administered macrolide antimicrobial drug, structurally related to erythromycin, with a similar spectrum of antimicrobial activity. Azithromycin is marginally less active than erythromycin in vitro against Gram-positive organisms, although this is of doubtful clinical significance as susceptibility concentrations fall within the range of achievable tissue azithromycin concentrations. In contrast, azithromycin appears to be more active than erythromycin against many Gram-negative pathogens and several other pathogens, notably Haemophilus influenzae, H. parainfluenzae, Moraxella catarrhalis, Neisseria gonorrhoeae, Urea-plasma urealyticum and Borrelia burgdorferi. Like erythromycin and other macrolides, the activity of azithromycin is unaffected by the production of beta-lactamase. However, erythromycin-resistant organisms are also resistant to azithromycin. Following oral administration, serum concentrations of azithromycin are lower than those of erythromycin, but this reflects the rapid and extensive movement of the drug from the circulation into intracellular compartments resulting in tissue concentrations exceeding those commonly seen with erythromycin. Azithromycin is subsequently slowly released, reflecting its long terminal phase elimination half-life relative to that of erythromycin. These factors allow for a single dose or single daily dose regimen in most infections, with the potential for increased compliance among outpatients where a more frequent antimicrobial regimen might traditionally be indicated. The potential disadvantage of low azithromycin serum concentrations, however, is that breakthrough bacteraemia may occur in patients who are severely ill; nevertheless, animal studies suggest that tissue concentrations of azithromycin are more important than those in serum when treating respiratory and other infections. The clinical efficacy of azithromycin has been confirmed in the treatment of infections of the lower and upper respiratory tracts (the latter including paediatric patients), skin and soft tissues (again including paediatric patients), in uncomplicated urethritis/cervicitis associated with N. gonorrhoeae, Chlamydia trachomatis or U. urealyticum and in the treatment of early Lyme disease. Azithromycin was as effective as erythromycin and other commonly used drugs including clarithromycin, beta-lactams (penicillins and cephalosporins), and quinolone and tetracycline antibiotics in some of the above infections. Some patients with acute exacerbations of chronic bronchitis due to H. influenzae may be refractory to therapy with azithromycin (as is the case with erythromycin) indicating the need for physician vigilance, although it should be noted that azithromycin is of equivalent efficacy to amoxicillin in the treatment of such patients. In the therapy of urethritis/cervicitis associated with C. trachomatis, N. gonorrhoea or U. urealyticum, a single dose azithromycin regimen offers a distinct advantage over currently available pharmacological options, while providing effective therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Clarithromycin: review of a new macrolide antibiotic with improved microbiologic spectrum and favorable pharmacokinetic and adverse effect profiles

OBJECTIVE

To compare the new macrolide antibiotic clarithromycin with erythromycin in terms of in vitro activity, pharmacokinetics, pharmacodynamics, clinical efficacy, and toxicity.

DATA IDENTIFICATION

An English-language literature search employing MEDLINE (1987-91), Index Medicus (1987-91), Program and Abstracts of the 30th Interscience Conference on Antimicrobial Agents and Chemotherapy (1990), Program and Abstracts of the 31st Interscience Conference on Antimicrobial Agents and Chemotherapy (1991), and bibliographic reviews of related textbooks and review articles.

STUDY SELECTION

Eighty-five articles were selected. Clinical trials with clarithromycin have been limited, and emphasis was placed on trials reported in the Program and Abstracts of the 30th Interscience Conference on Antimicrobial Agents and Chemotherapy and Program and Abstracts of the 31st Interscience Conference on Antimicrobial Agents and Chemotherapy.

DATA EXTRACTION

Articles were assessed for study quality and specific information addressing the stated purpose. In articles reporting the results of clinical trials, emphasis was placed on comparative efficacy and toxicity.

RESULTS OF DATA ANALYSIS

A review of 24 human trials suggests that clarithromycin is equally effective as erythromycin, penicillin VK, ampicillin, or amoxicillin for treatment of a variety of upper and lower respiratory tract or skin infections. Clarithromycin also appears to be better tolerated than these agents, with a lower incidence of gastrointestinal adverse effects. Limited clinical studies in patients with Mycobacterium leprae or Mycobacterium avium-intracellulare complex (MAI) suggest that clarithromycin may prove to be efficacious and well tolerated in the treatment of these infections.

CONCLUSIONS

Clarithromycin is as effective in vivo as erythromycin, with less gastrointestinal irritation. Additionally, clarithromycin appears to expand the traditional spectrum of macrolide antibiotics, with promising activity against M. leprae and MAI.

Clarithromycin. A review of its antimicrobial activity, pharmacokinetic properties and therapeutic potential

Clarithromycin is an acid-stable orally administered macrolide antimicrobial drug, structurally related to erythromycin. It has a broad spectrum of antimicrobial activity, similar to that of erythromycin and inhibits a range of Gram-positive and Gram-negative organisms, atypical pathogens and some anaerobes. Significantly, clarithromycin demonstrates greater in vitro activity than erythromycin against certain pathogens including Bacteroides melaninogenicus, Chlamydia pneumoniae, Chlamydia trachomatis, Mycobacterium chelonae subspecies--chelonae and--abscessus, Mycobacterium leprae, Mycobacterium marinum, Mycobacterium avium complex, Legionella spp. and, when combined with its 14-hydroxy metabolite, against Haemophilus influenzae. However, bacterial strains resistant to erythromycin are also generally resistant to clarithromycin. The antimicrobial activity of clarithromycin appears to be enhanced by the formation in vivo of the microbiologically active 14-hydroxy metabolite. In combination, additive or synergistic activity against a variety of pathogens including Haemophilus influenzae, Moraxella catarrhalis, Legionella species (principally Legionella pneumophila) and various staphylococci and streptococci has been demonstrated. Clarithromycin has a superior pharmacokinetic profile to that of erythromycin, allowing the benefits of twice daily administration with the potential for increased compliance among outpatients where a more frequent regimen for erythromycin might otherwise be indicated. The clinical efficacy of clarithromycin has been confirmed in the treatment of infections of the lower and upper respiratory tracts (including those associated with atypical pathogens), skin/soft tissues, and in paediatrics. Clarithromycin was as effective as erythromycin and other appropriate drugs including beta-lactams (penicillins and cephalosporins) in some of the above infections. A most promising indication for clarithromycin appears to be in the treatment of immunocompromised patients infected with M. avium complex, M. chelonae sp. and Toxoplasma sp. Small initial trials in this setting reveal clarithromycin alone or in combination with other antimicrobials to be effective in the eradication or amelioration of these infections. Noncomparative studies have provided preliminary evidence for the effectiveness of clarithromycin in the treatment of infections of the urogenital tract, oromaxillofacial and ophthalmic areas. However, the promising in vitro and preliminary in vivo activity of clarithromycin against Mycobacterium leprae and Helicobacter pylori warrant further clinical trials to assess its efficacy in patients with these infections. Despite the improved pharmacokinetic profile and in vitro antimicrobial activity of clarithromycin over erythromycin, comparative studies of patients with community-acquired infections reveal the 2 drugs to be of equivalent efficacy. However, clarithromycin demonstrates greater tolerability, principally by inducing fewer gastrointestinal disturbances.(ABSTRACT TRUNCATED AT 400 WORDS)

Clarithromycin, a unique macrolide. A pharmacokinetic, microbiological, and clinical overview

The in vitro and in vivo spectrum of antibacterial activity of clarithromycin is summarized and related to its human pharmacokinetics. In vitro studies by several investigators have documented clarithromycin's activity against bacterial agents of respiratory tract infections, skin and soft tissue infections, and sexually transmitted diseases. Clinical cure rates of 52%-83% (pneumonia), 79%-96% (bronchitis), 82%-96% (pharyngitis), 58% (sinusitis), and 78% (skin/skin-structure infections) have been reported in patients receiving clarithromycin in comparative trials. Respective bacteriologic eradication rates in clarithromycin recipients have been reported as 57%-89%, 79%-96%, 88%-100%, 89%, and 90%. In vitro and in vivo studies suggest that clarithromycin, when combined with its major human metabolite, 14-hydroxyclarithromycin, is also effective against Haemophilus influenzae. A New Drug Application claiming efficacy in the treatment of lower respiratory tract infection, sinusitis, pharyngitis, and skin and skin-structure infections caused by susceptible pathogens has been filed with the Food and Drug Administration (FDA). This review summarizes relevant pharmacokinetic, microbiological, and clinical data for clarithromycin.

Clinical microbiology of azithromycin

Azithromycin contains an aza-methyl substitution in the 15-membered aglycone ring and as such it is the prototype antibiotic of the azalide class, similar in mechanism of activity to the macrolides. It demonstrates a broad spectrum of activity against many aerobic and anaerobic Gram-positive species, and also inhibits a number of important aerobic and anaerobic Gram-negative bacteria. Significantly, azithromycin shows good activity against Haemophilus influenzae, an organism against which older macrolide antibiotics have proved disappointing. It is highly effective in inhibiting clinically significant intracellular pathogens such as Chlamydia trachomatis and Legionella. Bactericidal activity is seen for certain streptococci and for H. influenzae. Closely linked with azithromycin's microbiologic activity are its novel pharmacokinetics. Azithromycin moves rapidly from blood to tissue compartments where it remains for prolonged periods. Although serum concentrations remain low, the levels attained in the tissues (often greater than 2 mg/kg) are higher than the minimum inhibitory concentration for many common pathogens, and delivery of drug to infection sites by phagocytic cells contributes to these concentrations. This penetration into eukaryotic and prokaryotic cells may be responsible for azithromycin's expanded spectrum of activity, particularly against intracellular organisms. The use of antibiotic blood levels as breakpoints for susceptibility would appear to be inappropriate in the case of azalides. Rather, levels of drug at the tissue site of infection should be considered as guides to predicting efficacy. The in vitro activity of azithromycin, together with its unique tissue pharmacodynamics, define an agent that should demonstrate utility in infections of the respiratory tract, skin and skin structures, and certain sexually transmitted diseases.

In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to seven fluoroquinolones

The in vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to seven fluoroquinolones were assessed by the agar dilution method. Ciprofloxacin and temafloxacin were the most active compounds (MIC for 90% of isolates tested [MIC90], 0.06 microgram/ml), while enoxacin and pefloxacin were the least active (MIC90, 0.5 microgram/ml). Fleroxacin, lomefloxacin, and ofloxacin showed intermediate activities (MIC90s, 0.125 to 0.25 microgram/ml). These results suggest a possible role for the fluoroquinolones in the treatment of pertussis, at least in adult patients.

In vitro susceptibilities of Bordetella pertussis and Bordetella parapertussis to six new oral cephalosporins

Of six new oral cephalosporins, cefixime and cefpodoxime were the most active (MIC for 90% of isolates tested [MIC90], 16 micrograms/ml) against Bordetella pertussis, followed by cefetamet, cefprozil, and loracarbef (LY163892) (MIC90, 64 micrograms/ml) and ceftibuten (MIC90, 128 micrograms/ml). Against Bordetella parapertussis, loracarbef was more active (MIC90, 32 micrograms/ml) than the other compounds tested (MIC90s, 64 to greater than 128 micrograms/ml). The new oral cephalosporins are unlikely to play a role in pertussis treatment.