Safety and effect on anti-Chlamydia pneumoniae antibody titres of a 1 month course of daily azithromycin in adults with coronary artery disease

Antibiotics for secondary prevention of coronary heart disease

BACKGROUND

Coronary heart disease is the leading cause of mortality worldwide with approximately 7.4 million deaths each year. People with established coronary heart disease have a high risk of subsequent cardiovascular events including myocardial infarction, stroke, and cardiovascular death. Antibiotics might prevent such outcomes due to their antibacterial, antiinflammatory, and antioxidative effects. However, a randomised clinical trial and several observational studies have suggested that antibiotics may increase the risk of cardiovascular events and mortality. Furthermore, several non-Cochrane Reviews, that are now outdated, have assessed the effects of antibiotics for coronary heart disease and have shown conflicting results. No previous systematic review using Cochrane methodology has assessed the effects of antibiotics for coronary heart disease.

OBJECTIVES

We assessed the benefits and harms of antibiotics compared with placebo or no intervention for the secondary prevention of coronary heart disease.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, SCI-EXPANDED, and BIOSIS in December 2019 in order to identify relevant trials. Additionally, we searched TRIP, Google Scholar, and nine trial registries in December 2019. We also contacted 11 pharmaceutical companies and searched the reference lists of included trials, previous systematic reviews, and other types of reviews.

SELECTION CRITERIA

Randomised clinical trials assessing the effects of antibiotics versus placebo or no intervention for secondary prevention of coronary heart disease in adult participants (≥18 years). Trials were included irrespective of setting, blinding, publication status, publication year, language, and reporting of our outcomes.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted data. Our primary outcomes were all-cause mortality, serious adverse event according to the International Conference on Harmonization - Good Clinical Practice (ICH-GCP), and quality of life. Our secondary outcomes were cardiovascular mortality, myocardial infarction, stroke, and sudden cardiac death. Our primary time point of interest was at maximum follow-up. Additionally, we extracted outcome data at 24±6 months follow-up. We assessed the risks of systematic errors using Cochrane 'Rosk of bias' tool. We calculated risk ratios (RRs) with 95% confidence intervals (CIs) for dichotomous outcomes. We calculated absolute risk reduction (ARR) or increase (ARI) and number needed to treat for an additional beneficial outcome (NNTB) or for an additional harmful outcome (NNTH) if the outcome result showed a beneficial or harmful effect, respectively. The certainty of the body of evidence was assessed by GRADE.

MAIN RESULTS

We included 38 trials randomising a total of 26,638 participants (mean age 61.6 years), with 23/38 trials reporting data on 26,078 participants that could be meta-analysed. Three trials were at low risk of bias and the 35 remaining trials were at high risk of bias. Trials assessing the effects of macrolides (28 trials; 22,059 participants) and quinolones (two trials; 4162 participants) contributed with the vast majority of the data. Meta-analyses at maximum follow-up showed that antibiotics versus placebo or no intervention seemed to increase the risk of all-cause mortality (RR 1.06; 95% CI 0.99 to 1.13; P = 0.07; I² = 0%; ARI 0.48%; NNTH 208; 25,774 participants; 20 trials; high certainty of evidence), stroke (RR 1.14; 95% CI 1.00 to 1.29; P = 0.04; I² = 0%; ARI 0.73%; NNTH 138; 14,774 participants; 9 trials; high certainty of evidence), and probably also cardiovascular mortality (RR 1.11; 95% CI 0.98 to 1.25; P = 0.11; I²= 0%; 4674 participants; 2 trials; moderate certainty of evidence). Little to no difference was observed when assessing the risk of myocardial infarction (RR 0.95; 95% CI 0.88 to 1.03; P = 0.23; I² = 0%; 25,523 participants; 17 trials; high certainty of evidence). No evidence of a difference was observed when assessing sudden cardiac death (RR 1.08; 95% CI 0.90 to 1.31; P = 0.41; I² = 0%; 4520 participants; 2 trials; moderate certainty of evidence). Meta-analyses at 24±6 months follow-up showed that antibiotics versus placebo or no intervention increased the risk of all-cause mortality (RR 1.25; 95% CI 1.06 to 1.48; P = 0.007; I² = 0%; ARI 1.26%; NNTH 79 (95% CI 335 to 42); 9517 participants; 6 trials; high certainty of evidence), cardiovascular mortality (RR 1.50; 95% CI 1.17 to 1.91; P = 0.001; I² = 0%; ARI 1.12%; NNTH 89 (95% CI 261 to 49); 9044 participants; 5 trials; high certainty of evidence), and probably also sudden cardiac death (RR 1.77; 95% CI 1.28 to 2.44; P = 0.0005; I² = 0%; ARI 1.9%; NNTH 53 (95% CI 145 to 28); 4520 participants; 2 trials; moderate certainty of evidence). No evidence of a difference was observed when assessing the risk of myocardial infarction (RR 0.95; 95% CI 0.82 to 1.11; P = 0.53; I² = 43%; 9457 participants; 5 trials; moderate certainty of evidence) and stroke (RR 1.17; 95% CI 0.90 to 1.52; P = 0.24; I² = 0%; 9457 participants; 5 trials; high certainty of evidence). Meta-analyses of trials at low risk of bias differed from the overall analyses when assessing cardiovascular mortality at maximum follow-up. For all other outcomes, meta-analyses of trials at low risk of bias did not differ from the overall analyses. None of the trials specifically assessed serious adverse event according to ICH-GCP. No data were found on quality of life.

AUTHORS' CONCLUSIONS

Our present review indicates that antibiotics (macrolides or quinolones) for secondary prevention of coronary heart disease seem harmful when assessing the risk of all-cause mortality, cardiovascular mortality, and stroke at maximum follow-up and all-cause mortality, cardiovascular mortality, and sudden cardiac death at 24±6 months follow-up. Current evidence does, therefore, not support the clinical use of macrolides and quinolones for the secondary prevention of coronary heart disease. Future trials on the safety of macrolides or quinolones for the secondary prevention in patients with coronary heart disease do not seem ethical. In general, randomised clinical trials assessing the effects of antibiotics, especially macrolides and quinolones, need longer follow-up so that late-occurring adverse events can also be assessed.

Adverse events in people taking macrolide antibiotics versus placebo for any indication

BACKGROUND

Macrolide antibiotics (macrolides) are among the most commonly prescribed antibiotics worldwide and are used for a wide range of infections. However, macrolides also expose people to the risk of adverse events. The current understanding of adverse events is mostly derived from observational studies, which are subject to bias because it is hard to distinguish events caused by antibiotics from events caused by the diseases being treated. Because adverse events are treatment-specific, rather than disease-specific, it is possible to increase the number of adverse events available for analysis by combining randomised controlled trials (RCTs) of the same treatment across different diseases.

OBJECTIVES

To quantify the incidences of reported adverse events in people taking macrolide antibiotics compared to placebo for any indication.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which includes the Cochrane Acute Respiratory Infections Group Specialised Register (2018, Issue 4); MEDLINE (Ovid, from 1946 to 8 May 2018); Embase (from 2010 to 8 May 2018); CINAHL (from 1981 to 8 May 2018); LILACS (from 1982 to 8 May 2018); and Web of Science (from 1955 to 8 May 2018). We searched clinical trial registries for current and completed trials (9 May 2018) and checked the reference lists of included studies and of previous Cochrane Reviews on macrolides.

SELECTION CRITERIA

We included RCTs that compared a macrolide antibiotic to placebo for any indication. We included trials using any of the four most commonly used macrolide antibiotics: azithromycin, clarithromycin, erythromycin, or roxithromycin. Macrolides could be administered by any route. Concomitant medications were permitted provided they were equally available to both treatment and comparison groups.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and collected data. We assessed the risk of bias of all included studies and the quality of evidence for each outcome of interest. We analysed specific adverse events, deaths, and subsequent carriage of macrolide-resistant bacteria separately. The study participant was the unit of analysis for each adverse event. Any specific adverse events that occurred in 5% or more of any group were reported. We undertook a meta-analysis when three or more included studies reported a specific adverse event.

MAIN RESULTS

We included 183 studies with a total of 252,886 participants (range 40 to 190,238). The indications for macrolide antibiotics varied greatly, with most studies using macrolides for the treatment or prevention of either acute respiratory tract infections, cardiovascular diseases, chronic respiratory diseases, gastrointestinal conditions, or urogynaecological problems. Most trials were conducted in secondary care settings. Azithromycin and erythromycin were more commonly studied than clarithromycin and roxithromycin.Most studies (89%) reported some adverse events or at least stated that no adverse events were observed.Gastrointestinal adverse events were the most commonly reported type of adverse event. Compared to placebo, macrolides caused more diarrhoea (odds ratio (OR) 1.70, 95% confidence interval (CI) 1.34 to 2.16; low-quality evidence); more abdominal pain (OR 1.66, 95% CI 1.22 to 2.26; low-quality evidence); and more nausea (OR 1.61, 95% CI 1.37 to 1.90; moderate-quality evidence). Vomiting (OR 1.27, 95% CI 1.04 to 1.56; moderate-quality evidence) and gastrointestinal disorders not otherwise specified (NOS) (OR 2.16, 95% CI 1.56 to 3.00; moderate-quality evidence) were also reported more often in participants taking macrolides compared to placebo.The number of additional people (absolute difference in risk) who experienced adverse events from macrolides was: gastrointestinal disorders NOS 85/1000; diarrhoea 72/1000; abdominal pain 62/1000; nausea 47/1000; and vomiting 23/1000.The number needed to treat for an additional harmful outcome (NNTH) ranged from 12 (95% CI 8 to 23) for gastrointestinal disorders NOS to 17 (9 to 47) for abdominal pain; 19 (12 to 33) for diarrhoea; 19 (13 to 30) for nausea; and 45 (22 to 295) for vomiting.There was no clear consistent difference in gastrointestinal adverse events between different types of macrolides or route of administration.Taste disturbances were reported more often by participants taking macrolide antibiotics, although there were wide confidence intervals and moderate heterogeneity (OR 4.95, 95% CI 1.64 to 14.93; I² = 46%; low-quality evidence).Compared with participants taking placebo, those taking macrolides experienced hearing loss more often, however only four studies reported this outcome (OR 1.30, 95% CI 1.00 to 1.70; I² = 0%; low-quality evidence).We did not find any evidence that macrolides caused more cardiac disorders (OR 0.87, 95% CI 0.54 to 1.40; very low-quality evidence); hepatobiliary disorders (OR 1.04, 95% CI 0.27 to 4.09; very low-quality evidence); or changes in liver enzymes (OR 1.56, 95% CI 0.73 to 3.37; very low-quality evidence) compared to placebo.We did not find any evidence that appetite loss, dizziness, headache, respiratory symptoms, blood infections, skin and soft tissue infections, itching, or rashes were reported more often by participants treated with macrolides compared to placebo.Macrolides caused less cough (OR 0.57, 95% CI 0.40 to 0.80; moderate-quality evidence) and fewer respiratory tract infections (OR 0.70, 95% CI 0.62 to 0.80; moderate-quality evidence) compared to placebo, probably because these are not adverse events, but rather characteristics of the indications for the antibiotics. Less fever (OR 0.73, 95% 0.54 to 1.00; moderate-quality evidence) was also reported by participants taking macrolides compared to placebo, although these findings were non-significant.There was no increase in mortality in participants taking macrolides compared with placebo (OR 0.96, 95% 0.87 to 1.06; I² = 11%; low-quality evidence).Only 24 studies (13%) provided useful data on macrolide-resistant bacteria. Macrolide-resistant bacteria were more commonly identified among participants immediately after exposure to the antibiotic. However, differences in resistance thereafter were inconsistent.Pharmaceutical companies supplied the trial medication or funding, or both, for 91 trials.

AUTHORS' CONCLUSIONS

The macrolides as a group clearly increased rates of gastrointestinal adverse events. Most trials made at least some statement about adverse events, such as "none were observed". However, few trials clearly listed adverse events as outcomes, reported on the methods used for eliciting adverse events, or even detailed the numbers of people who experienced adverse events in both the intervention and placebo group. This was especially true for the adverse event of bacterial resistance.

On the pathway to better birth outcomes? A systematic review of azithromycin and curable sexually transmitted infections

The WHO recommends the administration of sulfadoxine-pyrimethamine (SP) to all pregnant women living in areas of moderate (stable) to high malaria transmission during scheduled antenatal visits, beginning in the second trimester and continuing to delivery. Malaria parasites have lost sensitivity to SP in many endemic areas, prompting the investigation of alternatives that include azithromycin-based combination (ABC) therapies. Use of ABC therapies may also confer protection against curable sexually transmitted infections and reproductive tract infections (STIs/RTIs). The magnitude of protection at the population level would depend on the efficacy of the azithromycin-based regimen used and the underlying prevalence of curable STIs/RTIs among pregnant women who receive preventive treatment. This systematic review summarizes the efficacy data of azithromycin against curable STIs/RTIs.

Secondary prevention of atherosclerosis through chlamydia pneumoniae eradication (SPACE Trial): a randomised clinical trial in patients with peripheral arterial disease

BACKGROUND

Sero-epidemiological and experimental studies suggest that Chlamydia pneumoniae infections play an important role in the development of atherosclerosis. Clinical trials have shown contradictory results regarding the efficacy of antibiotics to prevent atherosclerosis-related complications in patients with coronary artery disease. Our aim was to study the effect of a short course of azithromycin on the incidence of cardiovascular events and peripheral vascular function in patients with stable peripheral arterial disease (PAD).

PATIENTS AND METHODS

Five hundred and nine PAD-patients were randomised to receive either a 3-day course of azithromycin (500 mg daily) or placebo, with 2 years of follow-up. C. pneumoniae serology was determined at baseline. Clinical endpoints were death, coronary events (myocardial infarction, unstable angina, and/or coronary revascularization procedures), cerebral events (stroke, TIA, and/or carotid endarterectomy) and peripheral arterial complications (increased PAD-symptoms with decreased ankle-brachial index (ABPI, 0.1-point decrease after 12 months), and/or peripheral revascularization procedures).

RESULTS

Five hundred and nine patients (160 women) with an atherosclerotic risk factor profile were randomised, 257 patients to azithromycin and 252 to placebo. Four hundred and forty nine patients (88%) had intermittent claudication and 60 (12%) had critical limb ischemia. By 24-month follow up, 182 patients (36%) developed 252 complications (45 deaths, 34 coronary events, 34 cerebral events and 139 peripheral arterial complications). C. pneumoniae IgA-titres were associated with the development of cardiovascular events. Nevertheless, the number of complications (131 in the azithromycin group vs. 121 in the placebo group) and the number of patients that developed complications (98 (38%) in the azithromycin vs. 84 (33%) in the placebo group) was comparable in both treatment groups. Life table analysis showed no effect of azithromycin on survival or ABPI.

CONCLUSION

A short-term course of azithromycin offers no benefits for survival or ankle pressure in PAD-patients.

Effect of clarithromycin treatment on Chlamydia pneumoniae in vascular tissue of patients with coronary artery disease: a randomized, double-blind, placebo-controlled trial

Several small clinical trials have indicated that antibiotic treatment of Chlamydia pneumoniae infection is associated with a better outcome in patients with coronary artery disease (CAD). It has not been demonstrated whether antibiotic treatment eradicates C. pneumoniae from vascular tissue. The aim of the present study was to assess the effect of clarithromycin on the presence of C. pneumoniae in the vascular tissue of patients with CAD. Patients who had CAD and who were waiting for coronary artery bypass graft surgery were enrolled in a randomized, double-blind, placebo-controlled trial. Patients were treated with clarithromycin at 500 mg or placebo once daily from the day of inclusion in the study until surgery. Several vascular tissue specimens were obtained during surgery. The presence of C. pneumoniae in vascular tissue specimens was examined by immunohistochemical staining (IHC) and two PCR assays. Chlamydia immunoglobulin G (IgG) titers were determined by an enzyme-linked immunosorbent assay at the time of inclusion in the study and 8 weeks after surgery. A total of 76 patients were included, and 180 vascular tissue specimens were obtained (80 specimens from the group treated with clarithromycin and 100 specimens from the group treated with placebo). Thirty-five patients received clarithromycin (mean duration, 27 days; standard deviation [SD], 12.2 days), and 41 patients received placebo (mean duration, 27 days; SD, 13.9 days). IHC detected the C. pneumoniae major outer membrane protein antigen in 73.8% of the specimens from the group treated with clarithromycin and 77.0% of the specimens from the group treated with placebo (P was not significant). Chlamydia lipopolysaccharide antigen was found in only one specimen from the group that received placebo. C. pneumoniae DNA was not detected in any specimen. Baseline Chlamydia-specific IgG titers were equally distributed in both groups and were not significantly different after treatment. There was no indication of an active C. pneumoniae infection in vascular tissue. Chlamydia-specific IgG titers remained unchanged throughout the study in both the antibiotic- and the placebo-treated patients.

Antibiotics for vascular diseases: a meta-analysis of randomized controlled trials

BACKGROUND

Trials of antibiotic treatment of vascular diseases, in attempts to eradicate possible microbial initiators, have had mixed results. We sought to evaluate the efficacy of antibiotics in treating patients with atherosclerotic vascular diseases, using a meta-analysis.

METHODS

We searched MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials and also used cross-references. Randomized controlled trials of antibiotic treatment of vascular diseases were included. Two independent raters assessed the trials for quality. We performed summary estimates, subgroup analyses and tests for homogeneity.

RESULTS

Twelve trials, with a total of 12,236 patients, were included. Antibiotic treatment resulted in a non-significant reduction in the risk of new vascular events or death (odds ratio (OR), 0.84; 95% confidence interval (CI), 0.67-1.05). There was significant heterogeneity between the sub-groups in type of vascular disease (coronary heart disease, CHD versus non-CHD (p=0.01)). Among the 72 non-CHD patients, a trend appears for treatment benefit in reducing recurrent events or death (OR, 0.22; 95% CI, 0.07-0.66).

CONCLUSIONS

Overall, antibiotic treatment did not significantly reduce occurrence of new vascular events or death. However, further trials are needed to confirm the benefit demonstrated in non-CHD patients.

Chlamydia pneumoniae and coronary artery disease: the antibiotic trials

Parallel with the mounting evidence that atherosclerosis has a major inflammatory component, provoking agents that may initiate and drive this process have been sought. Infectious agents such as Chlamydia pneumoniae have been alleged to be activators of inflammation that may contribute to atherosclerosis and thus coronary artery disease (CAD) and its associated complications. A logical pneumoniae extension of this theory whether treating C pneumoniae infection with antibiotics and/or modulating inflammatory processes can affect CAD and its sequelae. This article discusses the potential role of C pneumoniae in atherosclerosis, its detection, and the rationale for antibiotics. Additionally, it summarizes the current randomized clinical trials of antichlamydial antibiotics in patients with CAD and draws conclusions based on the results.

Chlamydia pneumoniae and atherosclerosis: critical assessment of diagnostic methods and relevance to treatment studies

A number of studies have found that inflammation of the vessel wall plays an essential role in both the initiation and progression of atherosclerosis and erosion and fissure and the eventual rupture of plaques. Chlamydia pneumoniae is one of the infectious agents that have been investigated as possible causes of this inflammation. Initial studies of the association of C. pneumoniae and cardiovascular disease (CVD) were seroepidemiologic, and these were followed by studies in which the organism was identified in vascular tissue from patients with CVD by electron microscopy, PCR and immunocytochemical staining (ICC). C. pneumoniae has also been isolated by culture from vascular tissue in a small number patients. However, no single serologic, PCR, or ICC assay has been used consistently across all studies. The assays used are also not standardized. Recent studies of serologic and PCR assays for diagnosis of C. pneumoniae infection have suggested that there may be substantial interlaboratory variation in the performance of these tests. It now appears that some of the inconsistency of results from study to study may be due, in part, to lack of standardized methods. Although initial seroepidemiologic studies demonstrated a significantly increased risk of adverse cardiac outcome in patients who were seropositive, subsequent prospective studies found either small or no increased risk. In addition to the lack of consistent serologic criteria, recent evaluations have demonstrated inherent problems with performance of the most widely used serologic methods. Most importantly, we do not have a reliable serologic marker for chronic or persistent C. pneumoniae infection.

Prospective study of pathogen burden and risk of myocardial infarction or death

BACKGROUND

We previously demonstrated that the risk of coronary artery disease (CAD) increased in relation to the number of pathogens (the "pathogen burden") in a cross-sectional study. In the present prospective study with a different patient cohort, we evaluated the effect of pathogen burden on the risk of myocardial infarction (MI) or death among CAD patients.

METHODS AND RESULTS

IgG antibodies to cytomegalovirus (CMV), hepatitis A virus (HAV), herpes simplex virus type 1 (HSV1), HSV type 2 (HSV2), Chlamydia pneumoniae and Helicobacter pylori, and C-reactive protein (CRP) levels were tested in baseline blood samples from 890 patients who had significant CAD on angiography. The mean follow-up period was 3 years. The baseline prevalence of antibodies directed against CMV, HAV, HSV1, or HSV2, but not C pneumoniae and H pylori, was significantly higher among patients who subsequently developed MI or death than among control subjects. After adjustment for traditional risk factors, number of diseased vessels, and clinical presentation, relative hazards (95% confidence limits) for MI or death were 2.0 (1. 4 to 3.2) for CMV, 1.6 (1.1 to 2.3) for HAV, and 1.5 (1.0 to 2.2) for HSV2. Increasing pathogen burden was significantly associated with increasing risk of MI or death in a dose-response fashion. Adjusted relative hazards of MI or death associated with pathogen burden were significant among individuals with low or high CRP levels.

CONCLUSIONS

The results suggest that infection plays an important role in incident MI or death and that the risk posed by infection is independently related to the pathogen burden.

The evolving relationship between Chlamydia pneumoniae and atherosclerosis

A body of evidence supports an association between Chlamydia pneumoniae and atherosclerosis. Recent prospective, seroepidemiologic studies have refined estimations of relative risk. Advances in diagnostic testing with the polymerase chain reaction have created a potential opportunity to screen for infected individuals. New insights into the pathogenesis of infection with C. pneumoniae have been reported, many of which are relevant to the development of atherosclerotic plaque. Clinical trials have now been initiated and should provide guidance as to the utility of antibiotics in the treatment or prevention of coronary artery disease.