Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Feb 4;23(1):36.
doi: 10.1186/s12866-023-02784-2.

Antibiotic resistance pattern, capsular types, and molecular characterization of invasive isolates of Streptococcus pneumoniae in the south of Tunisia from 2012 to 2018

Sonia Ktari  1   2 , Nourelhouda Ben Ayed  3   4 , Imen Ben Rbeh  3 , Nourhène Garbi  5 , Sonda Maalej  3   4 , Basma Mnif  3   4 , Faouzia Rhimi  3   4 , Adnene Hammami  6   3   4
Affiliations

Antibiotic resistance pattern, capsular types, and molecular characterization of invasive isolates of Streptococcus pneumoniae in the south of Tunisia from 2012 to 2018

Sonia Ktari et al. BMC Microbiol. .

Abstract

Background: Streptococcus pneumoniae remains a leading cause of morbidity and mortality worldwide. In this study, we sought to analyze serotype distributions, antibiotic resistance, and genetic relationships of 106 clinical invasive pneumococcal isolates recovered in Tunisia between 2012 and 2018, prior to the routine use of pneumococcal conjugate vaccines (PCV).

Methods: We used multiplex PCR, the disk diffusion method and/or E-test, and multi-locus sequence typing (MLST).

Results: The most frequent serotypes were 14 (17%), 19F (14.2%), and 3 (11.3%). Of the 106 S. pneumoniae isolates, 67.9% were penicillin non-susceptible (29.4% were resistant), 45.3% were amoxicillin non-susceptible (17% were resistant), and 16% were cefotaxime non-susceptible. For antibiotics other than β-lactams, resistance rates to erythromycin, tetracycline, cotrimoxazole, and chloramphenicol were 62.3, 33, 22.6, and 4.7%, respectively. Two isolates were non-susceptible to levofloxacin. Among 66 erythromycin-resistant pneumococci, 77.3% exhibited the cMLSB phenotype, and 87.9% carried ermB gene. All tetracycline-resistant strains harbored the tetM gene. The potential coverage by 7-, 10-, and 13-valent pneumococcal conjugate vaccines were 55.7, 57.5, and 81.1%, respectively. A multilocus sequence typing analysis revealed great diversity. Fifty different sequence types (STs) were identified. These STs were assigned to 10 clonal complexes and 32 singletons. The most common STs were 179, 2918, 386, and 3772 - related mainly to 19F, 14, 6B/C, and 19A serotypes, respectively.

Conclusions: This study demonstrated that the majority of the serotypes of invasive pneumococci in the Tunisian population were 14, 19F, and 3. Moreover, we noted a high degree of genetic diversity among invasive S. pneumoniae isolates. The highest proportions of antibiotic non-susceptible isolates were for penicillin, erythromycin, and tetracycline. Further molecular characteristics are required to monitor the genetic variations and to follow the emergence of resistant pneumococci for the post-vaccination era in Tunisia.

Keywords: Antibiotic resistance; Clonal complex; Invasive pneumococcal disease; MLST; Serotype.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Serotype distribution of invasive S. pneumoniae isolates
Fig. 2
Fig. 2
Serotype distribution between meningitis and non-meningitis invasive pneumococcal Disease
Fig. 3
Fig. 3
Minimal spanning4 tree of MLST for invasive S. pneumoniae iso lates over the 7 –year period. Each circle represents an ST. The area of each circle corresponds to the number of isolates. The numbering shown between the connected nodes indicates the number of loci between the MLST profiles
See this image and copyright information in PMC

References

    1. Shetty AK, Maldonado YA. Current trends in Streptococcus pneumoniae infections and their treatment. Curr Pediatr Rep. 2013;1:158–169. doi: 10.1007/s40124-013-0021-9. - DOI
    1. World Health Organization . Surveillance vaccine preventable. Pneumococcus. 2018.
    1. Torné AN, Dias JG, Quinten C, Hruba F, Busana MC, Lopalco PL, et al. European enhanced surveillance of invasive pneumococcal disease in 2010: data from 26 European countries in the post-heptavalent conjugate vaccine era. Vaccine. 2014;32:3644–3650. doi: 10.1016/j.vaccine.2014.04.066. - DOI - PubMed
    1. Kaplan SL, Mason EO. Management of Infections due to antibiotic-resistant Streptococcus pneumoniae. Clin Microbiol Rev. 1998;11:628–644. doi: 10.1128/CMR.11.4.628. - DOI - PMC - PubMed
    1. Schroeder MR, Stephens DS. Macrolide resistance in Streptococcus pneumoniae. Front Cell Infect Microbiol. 2016;6. 10.3389/fcimb.2016.00098. - PMC - PubMed

Publication types