Clinical optochin resistant Streptococcus pneumoniae and Streptococcus pseudopneumoniae strains in Tunisia

  • Sonia Ktari Laboratory of Microbiology, Medical School of Sfax, Tunisia
  • Nour El Houda Ben Ayed Habib Bourguiba University Hospital, Sfax, Tunisia
  • Sonda Maalej Habib Bourguiba University Hospital, Sfax, Tunisia
  • Basma Mnif Habib Bourguiba University Hospital, Sfax, Tunisia
  • Faouzia Rhimi Habib Bourguiba University Hospital, Sfax, Tunisia
  • Adnene Hammami Habib Bourguiba University Hospital, Sfax, Tunisia
Keywords: S. pneumoniae, S. pseudopneumoniae, optochin resistance, bile solubility, molecular techniques

Abstract

Introduction: Streptococcus pneumoniae can be responsible for severe human infections. Optochin resistance has been a potential cause of misidentification of pneumococcus and other members of the mitis group. Hence, rapid and easy optochin resistant (Optr) S. pneumoniae identification is essential.

Methodology: Atypical pneumococci were characterized using optochin susceptibility, bile solubility based on spectrophotometric reading, serotyping, pulsed field gel electrophoresis (PFGE), 16S rRNA sequencing and PCR-based assays targeting pneumococcal genes lytA, ply, pspA, cpsA, Spn9802 and Spn9828.

Results: Optical density values for the bile solubility test suggest the identification of four OptrS. pneumoniae and one Streptococcus pseudopneumoniae. All Optr pneumococci harbored cpsA, lytA, ply, Spn9802, Spn9828 and pspA genes. Only ply, spn9802 and Spn9828 genes were detected in S. pseudopneumoniae. The 16S rRNA sequencing differentiates between these two species. OptrS. pneumoniae strains belonged to different genotypes and serotypes (14, 19A, 3 and 9V). Three OptrS. pneumoniae isolates were typed as pspA family 2, while one belonged to pspA family 1. Sequencing of the atpA and atpC gene of the Optr variants revealed three mutations in the ATPase a-subunit (L99I, M23V and V52I) and one mutation in ATPase c-subunit (V48I).

Conclusions: Our data indicate that bile OD-values provides an accurate, fast and easy method to discriminate between OptrS. pneumoniae and other Streptococcus mitis group. Moreover molecular techniques, confirming the bile test, can be used in order to prevent these atypical pneumococci and alert clinical microbiologists of the presence of these strains in the community.

Author Biographies

Nour El Houda Ben Ayed, Habib Bourguiba University Hospital, Sfax, Tunisia

Laboratory of Microbiology, Dr

Sonda Maalej, Habib Bourguiba University Hospital, Sfax, Tunisia

Laboratory of Microbiology, Dr

Basma Mnif, Habib Bourguiba University Hospital, Sfax, Tunisia

Laboratory of Microbiology, Professor

Faouzia Rhimi, Habib Bourguiba University Hospital, Sfax, Tunisia

Laboratory of Microbiology, Professor

Adnene Hammami, Habib Bourguiba University Hospital, Sfax, Tunisia

Laboratory of Microbiology, Professor

Published
2021-05-31
How to Cite
1.
Ktari S, Ben Ayed NEH, Maalej S, Mnif B, Rhimi F, Hammami A (2021) Clinical optochin resistant Streptococcus pneumoniae and Streptococcus pseudopneumoniae strains in Tunisia. J Infect Dev Ctries 15:672-677. doi: 10.3855/jidc.13106
Section
Original Articles