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Int J Antimicrob Agents. 2018 Oct 5. pii: S0924-8579(18)30282-6. doi: 10.1016/j.ijantimicag.2018.09.023. [Epub ahead of print]

Genetic Diversity of Streptococcus pneumoniae in Tunisia.

Author information

1
Microbiology Laboratory, A. Mami Hospital of Pneumology, UR12/SP18, Ariana, Tunisia; Faculty of Sciences of Tunis - University of Tunis El Manar, Ariana, Tunisia. Electronic address: midouni_basma@outlook.fr.
2
Microbiology Laboratory, A. Mami Hospital of Pneumology, UR12/SP18, Ariana, Tunisia.
3
Microbiology Laboratory, A. Mami Hospital of Pneumology, UR12/SP18, Ariana, Tunisia; Faculty of Sciences of Tunis - University of Tunis El Manar, Ariana, Tunisia.
4
UMR VITROME, AMU, IRD SSA, AP-HM, IHU Méditerranée Infection, Marseille, France.

Abstract

OBJECTIVE:

The objective of this study was to explore the genetic diversity of Streptococcus pneumoniae by using antibiotic susceptibility testing, serotyping and multilocus sequence typing (MLST) in a Tunisian pneumology hospital.

MATERIALS AND METHODS:

We investigated 141 strains of S.pneumoniae isolated between 2009 and 2016 in the Microbiology Laboratory at Pneumology Hospital A. Mami, Tunisia. Antimicrobial susceptibility was tested using the disk diffusion method. The MICs of penicillin G, amoxicillin, and cefotaxime were determined by E-test. Serotyping was inferred from the results of a multiplex PCR method targeting forty serotypes. Sequence types (ST) of S.pneumoniae isolates were determined using MLST technique.

RESULTS:

Among the 141 S. pneumoniae, 69.5% were resistant to erythromycin. The evaluation of susceptibility to ß-lactams showed that 63.8% of the strains were non-susceptible to penicillin, 34% had decreased susceptibility to amoxicillin, and 15% to cefotaxime. We detected 25 serotypes and 10 isolates that were classified as non-typable. The vaccine coverage was 57%, 60.3% and 75.1% for pneumococcal conjugate vaccine 7 (PCV7), PCV10, and PCV13 serotypes, respectively. Overall, 73 STs were identified in this study including 23 that were described for the first time. The most frequent STs were ST179 (n=17), ST3772 (n=14), ST2918 (n=10), ST4003 (n=5) and were related to serotypes 19F, 19A, 14 and 23F, respectively. We classified 110 strains within 45 STs. Three international antibiotic-resistant clones were found, Denmark14-ST230 (n=22), Spain9V-ST156 (n=22) and Portugal19F-ST177 (n=20).

CONCLUSION:

This study emphasizes the clonal and international dissemination of antibiotic-resistant clones of S.pneumoniae. Significant differences in genetic variation were documented by MLST, within the various serotypes identified.

KEYWORDS:

MLST; Resistance; Serotype; Streptococcus pneumoniae

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