Background: Streptococcus pneumoniae is an important pathogen which cause a wide range of severe infections acquired in the community, such as pneumonia or meningitis, especially in children, old people and immunosuppressed patients. The main virulence factor is its capsule, which is used for the serotyping and vaccine designs.

 

S.pneumoniae is usually treated with antibiotics of the β-lactams, but since the 60s, when the first resistant strain was reported, the treatment of infections caused by this pathogen has been more complicated because of that. S.pneumoniae becomes resistant to β-lactam antibiotics by altering its penicillin-binding proteins (PBPs), which are the target of β-lactams. In Spain the appearance of resistant strains is growing, therefore it is important to characterize them genetically and phenotypically.

 

Objectives: Determine the genetic diversity of S.pneumoniae PBPs belonging to the Denmark14-ST230 PMEN clone which are resistant to penicillin and amoxicillin found in patients with invasive pneumococcal diseases.

 

Methods: Antibiotic susceptibility testing by microdilution Molecular characterization of isolates by Multi Locus Sequence Typing and PCR-RFLP analysis and/or sequencing of PBPs.

 

Results: Seven sequence types related to Denmark14-ST230 were found. Serotype 19A and 19Fshowed higher penicillin and cefotaxime level of resistance than serotype 24F. The same allele and amino acid substitution for PBP1a were described and PBP2b had three different pbp alleles whereas the main amino acid substitutions related to resistance were the same for all isolates; however, PBP2x showed a higher genetic diversity presenting five different alleles and amino acid substitutions.

Conclusions: The emergence and spread of Denmark14-ST230 clone causing invasive pneumococcal disease in Spain is characterized by having a great genetic plasticity and including different recombination events in its capsular operon and their flanking regions including pbp2x.