Phenotypic and Molecular Characterization of Penicillin and Macrolide-Resistant Streptococcus pneumoniae Serotypes Among Pediatric Patients in Addis Ababa, Ethiopia

Abstract

Background

In several countries, introduction of the pneumococcal conjugate vaccine (PCV) has led to a decline in antimicrobial-resistant pneumococcal disease but has also resulted in a concomitant increase in antimicrobial-resistant, non-vaccine serotypes of Streptococcus pneumoniae. We sought to determine the magnitude of penicillin and macrolide resistance among pneumococcal serotypes and the mechanisms of macrolide resistance in Ethiopia, 5 years after the introduction of PCV10 in the country.

Methods

Susceptibility to penicillin and erythromycin of 119 pneumococcal isolates collected from pediatric patients aged 0–15 years in Addis Ababa, Ethiopia, was tested using disc diffusion, and minimum inhibitory concentration (MIC) was also determined by Etest. Pneumococcal serotypes were determined by sequencing the cpsB gene and using Quellung reaction. Polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism analysis were used to detect and differentiate the macrolide resistance genes erm(B), mef(A), and mef(B).

Results

Among the 119 isolates, 2.5% (3/119) were resistant to penicillin, while 58% (69/119) were intermediate. Resistance to erythromycin was observed in 33.6% (40/119) of the isolates with the highest level of resistance among isolates from middle ear discharge, i.e., 53.3% (8/15). Half (19/40) of the erythromycin resistant isolates were serotype 19A and among serotype 19A isolates, the majority i.e., 54.3% (19/35) were resistant to erythromycin. The most common macrolide resistance determinant was mef(E) with a prevalence of 50% (20/40).

Conclusion

Five years after introduction of PCV10 in Ethiopia, we observed that the prevalence of penicillin-resistant S. pneumoniae was low. However, there was a high level of macrolide resistance which was mostly in serotype 19A, and the resistance was mainly mediated by efflux pumps. Introduction of PCV13 (which covers serotype 19A) would significantly improve coverage of the macrolide-resistant serotypes. Continued surveillance of pneumococcal serotype distribution and their antibiotic resistance pattern in Ethiopia is warranted.

Keywords:

• efflux pump
• erythromycin
• mef(E)
• PCV10
• penicillin
• serotype 19A
• Streptococcus pneumoniae

Acknowledgments

We wish to express our sincere gratitude to all children and guardians who participated in the study, and to the physicians and nurses who participated in patient recruitment and sample collection.

Ethics Approval and Consent to Participate

The study procedures were in accordance with the Helsinki Declaration. The study was approved by the AHRI/All Africa Leprosy Rehabilitation and Training Hospital (ALERT) Ethics Review Committee, Addis Ababa University Institutional Review Board, Yekatit 12 Medical College Ethics Committee and the National Research Ethics Review Committee (No. 310/194/2017). The parents and/or guardians of all participants gave written informed consent.

Author Contributions

All authors made substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; took part in drafting the article or revising it critically for important intellectual content; agreed to submit to the current journal; gave final approval of the version to be published; and agree to be accountable for all aspects of the work.

Disclosure

Dr Abel Abera Negash reported grants from VLIR-UOS during the conduct of the study. The authors reported no other potential conflicts of interest for this work.