Online Abstracts Clinical Sciences - Disease Burden in Infants, Children/Youth, and Adults B2 Disease Burden in Infants, Children/Youth, and Adults



Azithromycin is a useful therapeutic, but its long half-life encourages development of azolide/macrolide resistance. We investigated increasing macrolide-resistance among Streptococcus pneumoniae, exploring the association of macrolide-resistance with serotype, clone and azithromycin use.


Between January-2002 to March-2015, 464 invasive pneumococcal isolates were collected and whole-genome sequenced. Azolide/macrolide non-susceptibility was determined by erythromycin disk-diffusion and E-test.


We identified macrolide resistance in 70 (15%) pneumococci; 64% of which harbored ermB, 33% mefA and 1.4% carried both the genetic determinants. Few (n=6 of 265 tested) were identified through 2009; subsequently resistance increased to 46% in 2014, and 60% in 2015. Macrolide-resistant pneumococci exhibited 24 serotypes; 19F (14%), 6B (13%) and 23F (13%) were predominant. PCV10, PCV13, and PCV20 would address 51% (36/70), 56% (39/70), and 63% (44/70), respectively. Macrolide-resistant pneumococci belonged to 26 GPSCs and 42 STs. Dominant lineages were GPSC10 (ST1553, 12894, 14490, 14488), GPSC43 (ST4745, 3214), GPSC101 (ST2854, 1078) and GPSC482 (ST5612). Increased azithromycin consumption showed direct association with increasing macrolide-resistance during this period (r=0.8572, p=0.0031, Spearman correlation coefficient).


Serotype and genotype diversity among macrolide-resistant pneumococci and low proportion addressed by PCVs suggests that a vaccine covering all strains or restricted consumption of azithromycin is needed to reduce transmission of macrolide-resistant strains.