Eur J Clin Microbiol Infect Dis. 2015 Nov 12. [Epub ahead of print]

The mystery of the fourth clone: comparative genomic analysis of four non-typeable Streptococcus pneumoniae strains with different susceptibilities to optochin.

Ikryannikova LN1, Ischenko DS2, Lominadze GG3, Kanygina AV2, Karpova IY2, Kostryukova ES2, Mayansky NA3,Skvortsov VS4, Ilina EN2, Govorun VM2.

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Abstract

Optochin-resistant pneumococci can be rarely caught in clinical microbiology laboratories because of the routine identification of all such strains as viridans group non-pneumococci. We were lucky to find four non-typeable Streptococcus pneumoniae clones demonstrating the different susceptibilities to optochin: one of them (Spn_13856) was resistant to optochin, while the other three (Spn_1719, Spn_27, and Spn_2298) were susceptible. Whole genome nucleotide sequences of these strains were compared to reveal the differences between the optochin-resistant and optochin-susceptible strains. Two adjacent genes coding maltose O-acetyltransferase and uridine phosphorylase which were presented in the genomes of all optochin-susceptible strains and missed in the optochin-resistant strain were revealed. Non-synonymous substitutions in 14 protein-coding genes were discovered, including the Ala49Ser mutation in the C-subunit of the F0 part of the ATP synthase rotor usually associated with pneumococcal optochin resistance. Modeling of a process of optochin interaction with the F0 part of the ATP synthase rotor indicates that the complex of optochin with "domain C" composed by wild-type C-subunits is more stable than the same complex composed of Ala49Ser mutant C-subunits.

PMID: 26563895 [PubMed - as supplied by publisher]