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We aimed to assess the prevalence of nasopharyngeal pneumococcal carriage and to determine serotype distribution, antibiotic susceptibility patterns, and evolutionary dynamics of Streptococcus pneumoniae isolates in healthy under-five children. Nasopharyngeal swabs were collected from healthy children over three survey periods between 2020 and 2022. All pneumococcal isolates were serotyped and tested for antimicrobial susceptibility. A total of 309 S. pneumoniae isolates were collected, with an overall prevalence of nasopharyngeal pneumococcal carriage of 24.4% (CI95%: [22-26.8%]). These isolates were classified into 25 different serotypes. The most common serotypes were 14 (14.9%), 19F (12%), 6B (10.4%), and 23F (7.4%), which are covered by the PCV10 vaccine, as well as 19A (8.4%) and 6A (7.8%), which are covered by the PCV13 vaccine. A significant decrease in the proportion of serotype 19F ( p = 0.001) and an increase in serotypes 19A ( p = 0.034) and 6A ( p = 0.029) were observed between the three survey periods. Multidrug resistance (MDR) was noted for 56.6% of the isolates. A significant association with antimicrobial resistance was observed for the most frequent serotypes, mainly serotype 19A. In conclusion, one-quarter of healthy under-five children in Tunisia carried S. pneumoniae in their nasopharynx. A dominance of vaccine serotypes significantly associated with antimicrobial resistance was recorded.

Introduction: In the lack of updated Tunisian epidemiological data, we sought to describe the epidemiology of Group B Streptococcus (GBS) in pregnant women and newborns., Materials and Methods: A retrospective analysis of GBS neonatal invasive infections and a cross-sectional study evaluating the prevalence of maternal GBS colonization were conducted. GBS isolates were tested for antimicrobial susceptibility, serotyped, and assessed for the appurtenance to the hypervirulent ST17 clone., Results: Of 98 neonates with GBS, early-onset GBS disease (EOD) comprised 83.7 and 16.3% were late-onset GBS disease (LOD). The prevalence of maternal GBS colonization was 27%. All GBS isolates were susceptible to penicillin. Serotype III predominated (42.6%) for neonatal invasive infections. GBS isolates belonging to the ST17 sequence type were found only as serotype III., Conclusion: This study documents the frequency of GBS EOD, the high rate of maternal GBS colonization, and the predominance of the hypervirulent clone type III/ST17 in infants.