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. 2023 Aug 21:14:1244366.
doi: 10.3389/fmicb.2023.1244366. eCollection 2023.

Serotype distribution, antimicrobial susceptibility and molecular epidemiology of invasive Streptococcus pneumoniae in the nine-year period in Serbia

Natasa Opavski  1 , Milos Jovicevic  1 , Jovana Kabic  1 , Dusan Kekic  1 , Zorica Vasiljevic  2 , Tanja Tosic  3 , Deana Medic  4   5 , Suzana Laban  6 , Lazar Ranin  1 , Ina Gajic  1
Affiliations

Serotype distribution, antimicrobial susceptibility and molecular epidemiology of invasive Streptococcus pneumoniae in the nine-year period in Serbia

Natasa Opavski et al. Front Microbiol. .

Abstract

Streptococcus pneumoniae is one of the leading bacterial pathogens that can cause severe invasive diseases. The aim of the study was to characterize invasive isolates of S. pneumoniae obtained during the nine-year period in Serbia before the introduction of the pneumococcal conjugate vaccines (PCVs) into routine vaccination programs by determining: serotype distribution, the prevalence and genetic basis of antimicrobial resistance, and genetic relatedness of the circulating pneumococcal clones. A total of 490 invasive S. pneumoniae isolates were included in this study. The serotype, antimicrobial susceptibility, and ST of the strains were determined by the Quellung reaction, disk- and gradient-diffusion methods, and multilocus sequence typing (MLST), respectively. The most common serotypes in this study were 3, 19F, 14, 6B, 6A, 19A, and 23F. The serotype coverages of PCV10 and PCV13 in children less than 2 years were 71.3 and 86.1%, respectively, while PPV23 coverage in adults was in the range of 85-96%, depending on the age group. Penicillin and ceftriaxone-non-susceptible isolates account for 47.6 and 16.5% of all isolates, respectively. Macrolide non-susceptibility was detected in 40.4% of isolates, while the rate of multidrug- and extensive-drug resistance was 20.0 and 16.9%, respectively. The MLST analysis of 158 pneumococci identified 60 different STs belonging to the 16 Clonal Complexes (CCs) (consisting of 42 STs) and 18 singletons. The most common CC/ST were ST1377, CC320, CC15, CC273, CC156, CC473, CC81, and CC180. Results obtained in this study indicate that the pre-vaccine pneumococcal population in Serbia is characterized by high penicillin and macrolides non-susceptibility, worrisome rates of MDR and XDR, as well as a high degree of genetic diversity. These findings provide a basis for further investigation of the changes in serotypes and genotypes that can be expected after the routine introduction of PCVs.

Keywords: Serbia; Streptococcus pneumoniae; antimicrobial susceptibility; molecular epidemiology; serotype.

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Conflict of interest statement

NO acts as a principal investigator for investigator-initiated sponsored research related to the topic conducted on behalf of the Faculty of Medicine, University of Belgrade, for which the Faculty obtained a research grant from Merck Sharp and Dohme doo. There are no patents, products in development, or marketed products associated with this research. We fully adhere to Frontiers policies on data and material sharing. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Figures

Figure 1
Figure 1
Distribution of serotypes and PCV10 and PCV13 coverage among pneumococci recovered from IPD during 2010–2018 in Serbia.
Figure 2
Figure 2
A minimum spanning tree of MLST for 158 invasive Streptococcus pneumoniae isolates over the nine-year period. Each circle represents a Sequence Type (ST), and the circle’s color represents the detected serotype. The area of each circle corresponds to the number of isolates. The numbering shown between the connected nodes indicates the differences in loci between the MLST profiles, and pastel zones between some groups of circles indicate that these profiles belong to the same clonal complex (CC).
See this image and copyright information in PMC

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