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Updated: Aug 19, 2026
Investigating the Effects of Probiotics on Pneumococcal Colonization Using an In Vitro Adherence Assay
Published on: April 28, 2014
Impact of amoxicillin on pneumococcal colonization compared with other therapies for acute otitis media
Philip Toltzis1, Michael Dul, Mary Ann O'Riordan
1Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University School of Medicine, Cleveland, OH, USA.
Background:
This study compared the effects of 4 outpatient antibiotic regimens on colonization by penicillin-susceptible and -nonsusceptible pneumococci to assess their relative potential to promote colonization with Streptococcus pneumoniae with reduced susceptibility to penicillin.
Methods:
Children presenting with acute otitis media were randomized to receive amoxicillin, cefprozil, ceftriaxone or azithromycin. Nasopharyngeal specimens were collected on days 0, 3-5, 10-14 and 28-30 and assessed for the presence of S. pneumoniae. At each visit, the proportions of penicillin-susceptible and -nonsusceptible pneumococci were compared among treatment groups.
Results:
Among 1009 enrollees, the prevalence of colonization by S. pneumoniae at baseline was 23.5%, of which 41.1% were penicillin-nonsusceptible. Colonization by nonsusceptible pneumococci was unaltered during the observation period in all treatment groups, with no detectable differences among groups at each visit. By contrast, there was a substantial reduction in the prevalence of colonization by penicillin-susceptible organisms, most notably in subjects treated with amoxicillin. This resulted in a proportional shift toward resistant organism colonization in all groups, with this shift being significantly more pronounced among amoxicillin recipients than in the other groups at 10-12 days (P < 0.02 for each comparison with amoxicillin).
Conclusions:
Treatment with amoxicillin for acute otitis media resulted in a larger shift toward nonsusceptible organism colonization among those children still colonized postexposure than did treatment with 3 comparison agents. This phenomenon raises theoretical concerns that at the population level, amoxicillin produces conditions that promote the dissemination of the nonsusceptible phenotype more readily than other outpatient antibiotics. Confirmation of these results requires further study.
Insights
Amoxicillin treatment for acute otitis media in children led to a greater increase in penicillin-nonsusceptible Streptococcus pneumoniae colonization compared to other antibiotics. This suggests amoxicillin may promote the spread of resistant bacteria.
Area of Science:
- Infectious Diseases
- Microbiology
- Pharmacology
Background:
- Pneumococcal infections, particularly acute otitis media (AOM), are common in children.
- Antibiotic resistance in Streptococcus pneumoniae (S. pneumoniae) is a growing public health concern.
- Understanding how different antibiotic regimens affect the carriage of antibiotic-susceptible and -nonsusceptible S. pneumoniae is crucial for antimicrobial stewardship.
Purpose of the Study:
- To compare the impact of four outpatient antibiotic treatments on nasopharyngeal colonization by penicillin-susceptible and -nonsusceptible S. pneumoniae.
- To evaluate the relative potential of amoxicillin, cefprozil, ceftriaxone, and azithromycin to promote colonization with S. pneumoniae exhibiting reduced penicillin susceptibility.
Main Methods:
- A randomized trial involving 1009 children with AOM.
- Nasopharyngeal specimens were collected at multiple time points (days 0, 3-5, 10-14, 28-30) to assess S. pneumoniae colonization.
- Proportions of penicillin-susceptible and -nonsusceptible S. pneumoniae were compared across treatment groups.
Main Results:
- Baseline S. pneumoniae colonization was 23.5%, with 41.1% being penicillin-nonsusceptible.
- All antibiotic groups showed a reduction in penicillin-susceptible S. pneumoniae.
- A significant proportional increase in penicillin-nonsusceptible S. pneumoniae colonization was observed in all groups, most pronounced in the amoxicillin group.
Conclusions:
- Amoxicillin treatment for AOM resulted in a greater shift toward nonsusceptible S. pneumoniae colonization compared to cefprozil, ceftriaxone, and azithromycin.
- These findings suggest that amoxicillin may foster conditions promoting the dissemination of penicillin-nonsusceptible S. pneumoniae at a population level.
- Further research is needed to confirm these observations and their clinical implications for antibiotic resistance patterns.
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Risk Factors
Various factors influence the likelihood of developing pneumonia. Age plays a crucial role, with infants, children under two, and individuals over 65 at increased risk due to their...