Evidence for clonal expansion after antibiotic selection pressure: Pneumococcal multilocus sequence types before and after mass azithromycin treatments

Jeremy D. Keenan, Keith P. Klugman, Lesley McGee, Jorge E. Vidal, Sopio Chochua, Paulina Hawkins, Vicky Cevallos, Teshome Gebre, Zerihun Tadesse, Paul M. Emerson, James H. Jorgensen, Bruce D. Gaynor, Thomas M. Lietman

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Background. A clinical trial of mass azithromycin distributions for trachoma created a convenient experiment to test the hypothesis that antibiotic use selects for clonal expansion of preexisting resistant bacterial strains. Methods. Twelve communities in Ethiopia received mass azithromycin distributions every 3 months for 1 year. A random sample of 10 children aged 0-9 years from each community was monitored by means of nasopharyngeal swab sampling before mass azithromycin distribution and after 4 mass treatments. Swab specimens were tested for Streptococcus pneumoniae, and isolates underwent multilocus sequence typing. Results. Of 82 pneumococcal isolates identified before treatment, 4 (5%) exhibited azithromycin resistance, representing 3 different sequence types (STs): 177, 6449, and 6494. The proportion of isolates that were classified as one of these 3 STs and were resistant to azithromycin increased after 4 mass azithromycin treatments (14 of 96 isolates [15%]; P =. 04). Using a classification index, we found evidence for a relationship between ST and macrolide resistance after mass treatments (P <. 0001). The diversity of STs - as calculated by the unbiased Simpson index - decreased significantly after mass azithromycin treatment (P =. 045). Conclusions. Resistant clones present before mass azithromycin treatments increased in frequency after treatment, consistent with the theory that antibiotic selection pressure results in clonal expansion of existing resistant strains.

Original languageEnglish (US)
Pages (from-to)988-994
Number of pages7
JournalJournal of Infectious Diseases
Volume211
Issue number6
DOIs
StatePublished - Mar 15 2015

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Keywords

  • Africa
  • MLST
  • Streptococcus pneumoniae
  • clonal expansion
  • multilocus sequence typing

ASJC Scopus subject areas

  • Immunology and Allergy
  • Infectious Diseases

Cite this

Keenan, J. D., Klugman, K. P., McGee, L., Vidal, J. E., Chochua, S., Hawkins, P., Cevallos, V., Gebre, T., Tadesse, Z., Emerson, P. M., Jorgensen, J. H., Gaynor, B. D., & Lietman, T. M. (2015). Evidence for clonal expansion after antibiotic selection pressure: Pneumococcal multilocus sequence types before and after mass azithromycin treatments. Journal of Infectious Diseases, 211(6), 988-994. https://doi.org/10.1093/infdis/jiu552