Selection of Antibiotic Resistance by Azithromycin and Clarithromycin in the Oral Flora

Impact of Azithromycin and Clarithromycin Therapy on Pharyngeal Carriage of Macrolide-Resistant Streptococci Among Healthy Volunteers: A Randomised, Double-Blind, Placebo-Controlled Trial

Status

Completed

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT00354952

Enrollment

203

Registered

2006-07-20

Start date

2002-07-31

Completion date

2003-10-31

Last updated

2006-07-20

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Healthy Volunteers

Keywords

Healthy volunteers, Antibiotic exposure, Resistance selection

Brief summary

Detailed description

Resistance to antibiotics is a major public-health problem and studies linking antibiotic use and resistance have shown an association not a causal effect. Utilizing the newer macrolides, azithromycin and clarithromycin that are commonly prescribed for respiratory infections, we investigated the direct impact of antibiotic exposure on resistance at the individual level. 203 healthy cohorts were treated with azithromycin, clarithromycin, or a placebo in a randomised, double-blind trial. Pharyngeal swabs were collected pre- (day 0) and post-antibiotic administration (days 8, 14, 28, 42, 180) and proportions of macrolide-resistant streptococci (MRS) were determined at each time-point.

Interventions

DRUGMacrolides (azithromycin or clarithromycin)

Study design

Allocation

RANDOMIZED

Intervention model

SINGLE_GROUP

Primary purpose

DIAGNOSTIC

Masking

DOUBLE

Eligibility

Sex/Gender

ALL

Age

18 Years to No maximum

Healthy volunteers

Yes

Inclusion criteria

* healthy adults (≥ 18 years of age) * non-pregnant * free of any respiratory tract infection * not having been administered any antibiotic at least in the past three months

Exclusion criteria

* \<18 years of age * pregnant * having a respiratory tract infection * having been administered any antibiotic at least in the past three months

Design outcomes

Primary

Measure	Time frame
Changes in proportions of macrolide-resistant streptococcal (MRS) carriage in the oropharynx	—

Secondary

Measure	Time frame
Variations in the carriage of macrolide-resistance genes due to macrolide exposure.	—

Countries

Belgium

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Apr 8, 2026