Bacteriological efficacies of three macrolides compared with those of amoxicillin-clavulanate against Streptococcus pneumoniae and Haemophilus influenzae

Azithromycin for acute lower respiratory tract infections

BACKGROUND

Acute lower respiratory tract infections (LRTI) range from acute bronchitis and acute exacerbations of chronic bronchitis to pneumonia. Approximately five million people die from acute respiratory tract infections annually. Among these, pneumonia represents the most frequent cause of mortality, hospitalisation and medical consultation. Azithromycin is a macrolide antibiotic, structurally modified from erythromycin and noted for its activity against some gram-negative organisms associated with respiratory tract infections, particularly Haemophilus influenzae (H. influenzae).

OBJECTIVES

To compare the effectiveness of azithromycin to amoxycillin or amoxycillin/clavulanic acid (amoxyclav) in the treatment of LRTI, in terms of clinical failure, incidence of adverse events and microbial eradication.

SEARCH METHODS

We searched CENTRAL (2014, Issue 10), MEDLINE (January 1966 to October week 4, 2014) and EMBASE (January 1974 to November 2014).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs, comparing azithromycin to amoxycillin or amoxycillin/clavulanic acid in participants with clinical evidence of an acute LRTI, such as acute bronchitis, pneumonia and acute exacerbation of chronic bronchitis.

DATA COLLECTION AND ANALYSIS

The review authors independently assessed all potential studies identified from the searches for methodological quality. We extracted and analysed relevant data separately. We resolved discrepancies through discussion. We initially pooled all types of acute LRTI in the meta-analyses. We investigated the heterogeneity of results using the forest plot and Chi(2) test. We also used the index of the I(2) statistic to measure inconsistent results among trials. We conducted subgroup and sensitivity analyses.

MAIN RESULTS

We included 16 trials involving 2648 participants. We were able to analyse 15 of the trials with 2496 participants. The pooled analysis of all the trials showed that there was no significant difference in the incidence of clinical failure on about days 10 to 14 between the two groups (risk ratio (RR), random-effects 1.09; 95% confidence interval (CI) 0.64 to 1.85). A subgroup analysis in trials with acute bronchitis participants showed significantly lower clinical failure in the azithromycin group compared to amoxycillin or amoxyclav (RR random-effects 0.63; 95% CI 0.45 to 0.88). A sensitivity analysis showed a non-significant reduction in clinical failure in azithromycin-treated participants (RR 0.55; 95% CI 0.25 to 1.21) in three adequately concealed studies, compared to RR 1.32; 95% CI 0.70 to 2.49 in 12 studies with inadequate concealment. Twelve trials reported the incidence of microbial eradication and there was no significant difference between the two groups (RR 0.95; 95% CI 0.87 to 1.03). The reduction of adverse events in the azithromycin group was RR 0.76 (95% CI 0.57 to 1.00).

AUTHORS' CONCLUSIONS

There is unclear evidence that azithromycin is superior to amoxycillin or amoxyclav in treating acute LRTI. In patients with acute bronchitis of a suspected bacterial cause, azithromycin tends to be more effective in terms of lower incidence of treatment failure and adverse events than amoxycillin or amoxyclav. However, most studies were of unclear methodological quality and had small sample sizes; future trials of high methodological quality and adequate sizes are needed.

Effectiveness of azithromycin in aspiration pneumonia: a prospective observational study

Background

Aspiration pneumonia is an urgent health concern with high mortality and long hospitalization in industrialized and aging countries. However, there is no information about the effectiveness of azithromycin (AZM) for the treatment of aspiration pneumonia. This study investigated if AZM is effective for the treatment of aspiration pneumonia.

Methods

Patients with aspiration pneumonia with no risk of multidrug-resistant pathogens were included in this prospective study at Kishiwada City Hospital from December 2011 to June 2013. Patients were divided into the ampicillin/sulbactam (ABPC/SBT) and AZM (intravenous injection) groups. The success rates of 1^st-line antibiotic therapy, mortality, length of hospital stay, and total antibiotic costs were compared.

Results

There were 81 and 36 patients in the ABPC/SBT and AZM groups, respectively. There was no significant difference in the success rate of 1^st-line antibiotics between the groups (74.1% vs. 75.0%, respectively, P = 1.000). Mortality and hospitalization periods did not differ between the 2 groups (11.1% vs. 8.3%, P = 0.753, and 22.3 ± 7.3 days vs. 20.5 ± 8.1 days, P = 0.654, respectively). However, the total antibiotic costs were significantly lower in the AZM group than the ABPC/SBT group (2.19 ± 1.65 × 10,000 yen vs. 2.94 ± 1.67 × 10,000 yen, respectively, P = 0.034). The febrile period of the ABPC/SBT group was significantly shorter than that of the AZM group (P = 0.025).

Conclusions

In this small prospective non-randomized observational study, we found no statistically significant differences in mortality or antibiotic failure in patients receiving AZM compared to ABPC/SBT for the treatment of patients with aspiration pneumonia who require hospital admission and have no risk of drug-resistant pathogens. Therefore, AZM may be another first choice of antibiotic treatment for patients with aspiration pneumonia when they have no risk of multidrug-resistant pathogens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0685-y) contains supplementary material, which is available to authorized users.

Azithromycin for acute lower respiratory tract infections

BACKGROUND

Acute lower respiratory tract infections (LRTI) range from acute bronchitis and acute exacerbations of chronic bronchitis to pneumonia. Approximately five million people die of acute respiratory tract infections annually. Among these, pneumonia represents the most frequent cause of mortality, hospitalization and medical consultation. Azithromycin is a new macrolide antibiotic, structurally modified from erythromycin and noted for its activity against some gram-negative organisms associated with respiratory tract infections, particularly Haemophilus influenzae (H. influenzae).

OBJECTIVES

To compare the effectiveness of azithromycin to amoxycillin or amoxycillin/clavulanic acid (amoxyclav) in the treatment of LRTI, in terms of clinical failure, incidence of adverse events and microbial eradication.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007 Issue 2), MEDLINE (January 1966 to July 2007), and EMBASE (January 1974 to July 2007).

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials, comparing azithromycin to amoxycillin or amoxycillin/clavulanic acid in participants with clinical evidence of acute LRTI: acute bronchitis, pneumonia, and acute exacerbation of chronic bronchitis were studied.

DATA COLLECTION AND ANALYSIS

The criteria for assessing study quality were generation of allocation sequence, concealment of treatment allocation, blinding, and completeness of the trial. All types of acute LRTI were initially pooled in the meta-analyses. The heterogeneity of results was investigated by the forest plot and Chi-square test. Index of I-square (I(2)) was also used to measure inconsistent results among trials. Subgroup and sensitivity analyses were conducted.

MAIN RESULTS

Fifteen trials were analysed. The pooled analysis of all trials showed that there was no significant difference in the incidence of clinical failure on about day 10 to 14 between the two groups (relative risk (RR), random-effects 1.09; 95% confidence interval (CI) 0.64 to 1.85). Sensitivity analysis showed a reduction of clinical failure in azithromycin-treated participants (RR 0.55; 95% CI 0.25 to 1.21) in three adequately concealed studies, compared to RR 1.32; 95% CI 0.70 to 2.49 in 12 studies with inadequate concealment. Twelve trials reported the incidence of microbial eradication and there was no significant difference between the two groups (RR 0.95; 95% CI 0.87 to 1.03). The reduction of adverse events in the azithromycin group was RR 0.76 (95% CI 0.57 to 1.00).

AUTHORS' CONCLUSIONS

There is unclear evidence that azithromycin is superior to amoxicillin or amoxyclav in treating acute LRTI. In patients with acute bronchitis of a suspected bacterial cause, azithromycin tends to be more effective in terms of lower incidence of treatment failure and adverse events than amoxicillin or amoxyclav. Future trials of high methodological quality are needed.

Comparative bacteriological efficacy of pharmacokinetically enhanced amoxicillin-clavulanate against Streptococcus pneumoniae with elevated amoxicillin MICs and Haemophilus influenzae

A new pharmacokinetically enhanced formulation of amoxicillin-clavulanate (2,000 mg of amoxicillin/125 mg of clavulanate twice a day; ratio 16:1) has been designed, with sustained-release technology, to allow coverage of bacterial strains with amoxicillin-clavulanic acid MICs of at least 4/2 mug/ml. The bacteriological efficacy of amoxicillin-clavulanate, 2,000/125 mg twice a day, ratio 16:1, was compared in a rat model of respiratory tract infection versus four other amoxicillin-clavulanate formulations: 8:1 three times a day (1,000/125 mg), 7:1 three times a day (875/125 mg), 7:1 twice a day (875/125 mg), and 4:1 three times a day (500/125 mg); levofloxacin (500 mg once a day); and azithromycin (1,000 mg on day 1 followed thereafter by 500 mg once a day). Bacterial strains included Streptococcus pneumoniae, with amoxicillin-clavulanic acid MICs of 2/1 (one strain), 4/2, or 8/4 microg/ml (three strains each), and Haemophilus influenzae, one beta-lactamase-positive strain and one beta-lactamase-negative, ampicillin-resistant strain. Animals were infected by intrabronchial instillation. Antibacterial treatment commenced 24 h postinfection, with doses delivered by computer-controlled intravenous infusion to approximate the concentrations achieved in human plasma following oral administration. Plasma concentrations in the rat corresponded closely with target human concentrations for all antimicrobials tested. Amoxicillin-clavulanate, 2,000/125 mg twice a day, ratio 16:1, was effective against all S. pneumoniae strains tested, including those with amoxicillin-clavulanic acid MICs of up to 8/4 microg/ml and against beta-lactamase-producing and beta-lactamase-negative ampicillin-resistant H. influenzae. These results demonstrate the bacteriological efficacy of pharmacokinetically enhanced amoxicillin-clavulanate 2,000/125 mg twice a day (ratio 16:1) against S. pneumoniae with amoxicillin-clavulanic acid MICs of at least 4/2 microg/ml and support clavulanate 125 mg twice a day as sufficient to protect against beta-lactamase in this rat model.

Azithromycin for acute lower respiratory tract infections

BACKGROUND

The spectrum of acute lower respiratory tract infection ranges from acute bronchitis and acute exacerbations of chronic bronchitis to pneumonia. Annually approximately five million people die of acute respiratory tract infections. Among these, pneumonia represents the most frequent cause of mortality, hospitalization and medical consultation. Azithromycin is a new macrolide antibiotic, structurally modified from erythromycin and is noted for its activity against some gram-negative organisms associated with respiratory tract infections, particularly Haemophilus influenzae (H. influenzae).

OBJECTIVES

To compare the effectiveness of azithromycin to amoxycillin or amoxycillin/clavulanic acid (amoxyclav) in the treatment of LRTI, in terms of clinical failure, incidence of adverse events and microbial eradication.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2003), MEDLINE (January 1966 to January Week 3, 2004), and EMBASE (January 1988 to 2003).

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials, which compared azithromycin to amoxycillin or amoxycillin/clavulanic acid in patients with clinical evidence of acute LRTI: acute bronchitis, pneumonia, and acute exacerbation of chronic bronchitis were studied.

DATA COLLECTION AND ANALYSIS

The criteria for assessing study quality were generation of allocation sequence, concealment of treatment allocation, blinding, and completeness of the trial. All types of acute lower respiratory tract infections were initially pooled in the meta-analyses. Funnel plot was used to examine publication bias. The heterogeneity of results was investigated by the forest plot and Chi-square test. Index of I(2) was also used to measure inconsistency results among trials. Subgroup analysis was conducted for age, types of respiratory tract infection and types of antibiotic in control groups. Sensitivity analysis was conducted under the condition of trial size and concealment of treatment allocation.

MAIN RESULTS

Fourteen trials with 2,521 enrolled patients used 2,416 patients in the analysis. A total of 1,350 patients received azithromycin and 1,066 received amoxicillin or amoxicillin-clavulanic acid. The pooled analysis of all trials showed that there was no significant difference in the incidence of clinical failure on about day 10 to 14 after therapy started between the two groups (relative risk (RR) (random effects) 0.96; 95% CI 0.58 to 1.57). Sensitivity analysis showed that a reduction of clinical failure in azithromycin-treated patients (RR 0.52; 95% CI 0.24 to 1.12) in three adequately concealed studies, compared to RR 1.14 (95% CI 0.62 to 2.08) in eleven studies with inadequate concealment. Eleven trials reported the incidence of microbial eradication and there was no significant difference between the two groups (RR 0.98; 95% CI 0.91 to 1.07). The reduction of adverse events in azithromycin group was RR 0.75 (95% CI 0.56 to 1.00).

REVIEWERS' CONCLUSIONS

There is unclear evidence that azithromycin is superior to amoxicillin or amoxicillin-clavulanic acid in treating acute LRTI. Future trials with high methodological quality are needed.

An ex-vivo pharmacodynamic study comparing bactericidal activity of amoxicillin/sulbactam, azithromycin, doxycycline and levofloxacin against Streptococcus pneumoniae

We designed a 4-way crossover, ex-vivo pharmacodynamic study to compare the bactericidal rate of amoxicillin/sulbactam (AMX-SUL), azithromycin (AZM), doxycycline (DOX) and levofloxacin (LVX) against Streptococcus pneumoniae ATCC 49619. Six volunteers were randomized to receive alternatively a single tablet of the above drugs. Venous blood samples were obtained immediately before and at 2, 4 and 6 h after dose to perform time-kill studies and to determine antibiotic levels in serum. AMX-SUL was the only drug showing bactericidal activity with the sera obtained at every time after dose, as defined by a > or = 3-log10 cfu/ml decrease in the viable cell counts compared to the original inoculum after a 24-h incubation. AZM was only inhibitory at 2h after dose (i.e. a 1.3-log10 cfu/ml decrease in the viable cell counts) and proved bactericidal at 4 and 6 h post-dose. LVX proved bactericidal with the 2-h serum, was only inhibitory with the 4-h serum (e.g. a 1.5-log10 cfu/ml decrease) and was unable to avoid bacterial growth at 6 h post-dose. Bacterial growth was observed with DOX at every time after dose. This study may shed light on the understanding of breakthrough pneumococcal bacteremia during the course of oral therapy with AZM in patients with community-acquired nia (CAP), as well as the increasing treatment failures observed with LVX, and the selection of bacterial resistance during therapy reported with both drugs. It also provides the basis for a "warning signal" on the use of oral DOX and confirms the efficacy of AMX-SUL.

Amoxicillin/clavulanic acid: a review of its use in the management of paediatric patients with acute otitis media

Amoxicillin/clavulanic acid (Augmentin), Augmentin ES-600 is a well established, orally administered combination of amoxicillin (a semisynthetic antibacterial agent) and clavulanic acid (a beta-lactamase inhibitor). Amoxicillin/clavulanic acid shows good activity against the main pathogens associated with acute otitis media (AOM), including penicillin-susceptible and -intermediate strains of Streptococcus pneumoniae, and beta-lactamase producing strains of Haemophilus influenzae and Moraxella catarrhalis. It has moderate activity against penicillin-resistant S. pneumoniae; a high-dose formulation has been developed with the aim of providing better coverage for penicillin-resistant strains. Amoxicillin/clavulanic acid (conventional formulations, mostly 40/10 mg/kg/day in three divided doses) produced clinical response rates similar to those of oral cephalosporin comparators and similar to or significantly greater than those for intramuscular ceftriaxone in randomised trials in paediatric patients with AOM (mean age approximately 2 to 5 years). Clinical response rates were generally similar for amoxicillin/clavulanic acid and macrolide comparators (mean patient age approximately 1 to 6 years), although significantly better clinical and bacteriological responses were seen versus azithromycin in one randomised trial (mean patient age approximately 1 year). The high-dose formulation of amoxicillin/clavulanic acid (90/6.4 mg/kg/day in two divided doses) eradicated a high proportion of penicillin-resistant S. pneumoniae (penicillin MICs 2 or 4 mg/L) in a large noncomparative trial in children with AOM (upper limit of the US indication for S. pneumoniae is 2 mg/L). Amoxicillin/clavulanic acid is generally well tolerated. A low total incidence of adverse events (3.6%) and no serious events were reported from a large paediatric postmarketing study. The most frequently reported adverse events in children are mild gastrointestinal disturbances. Diarrhoea is generally less frequent with twice-daily than with three-times-daily treatment. The new high-dose formulation showed similar tolerability to a conventional twice-daily formulation (45/6.4 mg/kg/day) in a well controlled trial.

CONCLUSIONS

Amoxicillin/clavulanic acid is a well established broad-spectrum antibacterial treatment which is effective and well tolerated in the treatment of AOM in paediatric patients. The high-dose combination should prove valuable in treating AOM caused by penicillin-intermediate and -resistant S. pneumoniae (approved in the US for penicillin MIC < or =2 mg/L). Based on recent recommendations and the available data, high-dose amoxicillin/clavulanic acid can be considered a treatment of choice for recurrent or persistent paediatric AOM (after failure of amoxicillin alone) where involvement of resistant pathogens is suspected.

Treatment of pediatric sinusitis

The successful management of RS in children relies on careful diagnosis, recognition of causative factors, and judicious yet adequate antibiotic usage. Refractory cases will require surgical therapy, with adenoidectomy as the first-line intervention and ESS reserved for those cases refractory to adenoidectomy. This overall approach will improve quality of life and prevent complications in children with RS.

Pharmacokinetics of azithromycin in lung tissue, bronchial washing, and plasma in patients given multiple oral doses of 500 and 1000 mg daily

The present study compares the pharmacokinetics of azithromycin in plasma, lung tissue, and bronchial washing after oral administration of 500 mg (standard dose) versus 1000 mg daily for 3 days. Samples were taken during surgery for lung resection at various time points up to 204 h after the last drug dose, and azithromycin levels were analyzed by HPLC method. Azithromycin was widely distributed within the lower respiratory tract; sustained concentrations of the drug were detectable at the last sampling time (204 h) in lung tissue and bronchial washing, with long terminal half-lives of 132.86 and 74.32 h at 500 mg daily and 133.32 and 70.5 h at 1000 mg daily, respectively. Doubling the drug dose resulted in a remarkable increase in lung area under the curve (AUC, 1318 hx microg g(-1) vs 2502 hx microg g(-1)) and peak tissue concentration (9.13+/-0.53 microg g(-1) vs 17.85+/-2.4 microg g(-1)). In addition to this, enhanced azithromycin penetration from plasma into bronchial secretion and lung tissue was evidenced by the increase in the ratio of AUC(bronchial washing) versus AUC(plasma) (2.96 vs 5.27 at 500 and 1000 mg, respectively) and AUC(lung) versus AUC(plasma) (64.35 vs 97.73 at 500 and 1000 mg, respectively). In conclusion, the exposure of lung and bronchial washing to azithromycin is increased by doubling the dose, which results in favorable pharmacokinetic profile of the drug in the lower respiratory tract.

Review of macrolides and ketolides: focus on respiratory tract infections

The first macrolide, erythromycin A, demonstrated broad-spectrum antimicrobial activity and was used primarily for respiratory and skin and soft tissue infections. Newer 14-, 15- and 16-membered ring macrolides such as clarithromycin and the azalide, azithromycin, have been developed to address the limitations of erythromycin. The main structural component of the macrolides is a large lactone ring that varies in size from 12 to 16 atoms. A new group of 14-membered macrolides known as the ketolides have recently been developed which have a 3-keto in place of the L-cladinose moiety. Macrolides reversibly bind to the 23S rRNA and thus, inhibit protein synthesis by blocking elongation. The ketolides have also been reported to bind to 23S rRNA and their mechanism of action is similar to that of macrolides. Macrolide resistance mechanisms include target site alteration, alteration in antibiotic transport and modification of the antibiotic. The macrolides and ketolides exhibit good activity against gram-positive aerobes and some gram-negative aerobes. Ketolides have excellent activity versus macrolide-resistant Streptococcus spp. Including mefA and ermB producing Streptococcus pneumoniae. The newer macrolides, such as azithromycin and clarithromycin, and the ketolides exhibit greater activity against Haemophilus influenzae than erythromycin. The bioavailability of macrolides ranges from 25 to 85%, with corresponding serum concentrations ranging from 0.4 to 12 mg/L and area under the concentration-time curves from 3 to 115 mg/L x h. Half-lives range from short for erythromycin to medium for clarithromycin, roxithromycin and ketolides, to very long for dirithromycin and azithromycin. All of these agents display large volumes of distribution with excellent uptake into respiratory tissues and fluids relative to serum. The majority of the agents are hepatically metabolised and excretion in the urine is limited, with the exception of clarithromycin. Clinical trials involving the macrolides are available for various respiratory infections. In general, macrolides are the preferred treatment for community-acquired pneumonia and alternative treatment for other respiratory infections. These agents are frequently used in patients with penicillin allergies. The macrolides are well-tolerated agents. Macrolides are divided into 3 groups for likely occurrence of drug-drug interactions: group 1 (e.g. erythromycin) are frequently involved, group 2 (e.g. clarithromycin, roxithromycin) are less commonly involved, whereas drug interactions have not been described for group 3 (e.g. azithromycin, dirithromycin). Few pharmacoeconomic studies involving macrolides are presently available. The ketolides are being developed in an attempt to address the increasingly prevalent problems of macrolide-resistant and multiresistant organisms.

In vitro activity of clarithromycin against penicillin-susceptible and penicillin-resistant strains of Streptococcus pneumoniae in a pharmacodynamic simulation model

Clarithromycin has shown enhanced activity against Streptococcus pneumoniae, but increased resistance to macrolides has been observed in recent years. Our aim was to investigate its activity against strains of S. pneumoniae with variable susceptibility to this antibiotic and to penicillin. We determined killing curves using the Centriprep-10 pharmacodynamic simulation model, which permits using varying antibiotic concentrations to mimic a pharmacokinetic human profile in serum (corresponding to an oral dose of 500 mg). Four strains of S. pneumoniae were tested. In susceptible strains, clarithromycin showed bactericidal activity (reductions of up to 2.97 log10 cfu/ml of the initial inoculum). In resistant strains, clarithromycin showed a bacteriostatic effect (<1 log10 cfu/ml reduction). Penicillin-susceptible strains showed higher reductions than penicillin-resistant strains. This effect is important owing to the high minimum inhibitory concentration (MIC) of one of the resistant strains (32 microg/ml). More studies are needed to explain this bacteriostatic activity.

Prospective study of the usefulness of sputum Gram stain in the initial approach to community-acquired pneumonia requiring hospitalization

From February 1995 through May 1997, we prospectively studied 533 patients with community-acquired pneumonia requiring hospitalization in order to assess the current usefulness of sputum Gram stain in guiding the etiologic diagnosis and initial antibiotic therapy when applied routinely. Sputum samples of good quality were obtained in 210 (39%) patients, 175 of whom showed a predominant morphotype. Sensitivity and specificity of Gram stain for the diagnosis of pneumococcal pneumonia were 57% and 97%, respectively; the corresponding values for Haemophilus influenzae pneumonia were 82% and 99%. Patients with a predominant morphotype were more frequently treated with monotherapy than were patients without a demonstrative sputum sample (89% vs. 75%; P<.001). Analysis of our data shows that a good-quality sputum sample can be obtained from a substantial number of patients with community-acquired pneumonia. Gram stain was highly specific for the diagnosis of pneumococcal and H. influenzae pneumonia and may be useful in guiding pathogen-oriented antimicrobial therapy.

A review of clinical trials with fluoroquinolones with an emphasis on new agents

This review aims to provide a comparison between the antimicrobial spectra, pharmacokinetics and clinical efficacy of the newer fluoroquinolones with older agents in this class, as well as other antibiotics used to treat lower respiratory and urinary tract infections (LRTIs and UTIs) respectively. Increasing antimicrobial resistance among common uro- and respiratory pathogens has focused attention on the development of fluoroquinolones, which have a broad spectrum of activity and improved tissue penetration. The new and developmental quinolones can be administered on a once-daily basis and exhibit high oral bioavailability, which reduces the need for parenteral therapy in hospitalised patients and may therefore potentially reduce the need for hospitalisation. These attributes, coupled with their expanded spectrum suggest that the newer fluoroquinolones are so far the most ideal agents for the empirical treatment of many common infections.