The association of pili with the emergence and replacement of the major antibiotic resistant pneumococcal clones
Abstract
Background: The aim of this study was to evaluate the presence of pilus islet 1 (PI-1) and to determine its Glade type in pneumococcal isolates with reduced susceptibility to penicillin (penicillin non-susceptible pneumococci - PNSP) and/or resistant to macrolides isolated prior to and after the introduction of pneumococcal conjugate vaccines (PCVs) in the Czech Republic. Methods: Clinical isolates of serotypes 9V (n = 68) and 19A (n = 89) were examined.
Isolates were characterised by multilocus sequence typing (MLST). The presence of PI-1 was determined by screening for the sortase B, C, and D genes located within PI-1.
In the presence of PI-1 pilus, Glade types were classified by PCR. Results: In the pre-PCV period (2000-2007), the prevalence of PNSP was 3.9% and 2.7% of isolates were resistant to erythromycin.
During 2012-2015 (post-PCV period), the rates of PNSP remained stable (3.6%), but resistance to erythromycin increased to 8.3%. While in 2000 -2007, resistance to antibiotics was associated mainly with serotype 9V, in 2012-2015, it was replaced by serotype 19A.
PI-1 positive isolates were seen in both serotypes. All isolates (68) of serotype 9V belonged to the Spain( 9V)-3 (CC156) clone and carried PI-1 of Glade type I while 96.5% (56/58) of isolates of 19A serotype belonged to the Netherlands (15B)-37 (CC199) clone and carried PI-1 of Glade type II.
Conclusions: Both major antibiotic resistant clones carried PI-1, although they differ in the Glade type. Thus the role of PI-1 should be evaluated in further studies and potentially considered in the spread of antibiotic resistant clones.