Organism

Streptococcus pneumoniae, resistant

Streptococcus pneumoniae is a gram-positive diplococcus that was generally susceptible to all classes of antimicrobial agents in the 1970s.

With increased usage of antibiotics in patients with viral infections, S. pneumoniae has acquired genetic material that encodes resistance to many commonly used antibiotics.

It has developed resistance to beta-lactamases (45%) at altered penicillin-binding protein sites, to macrolides (40%) with a macrolide efflux pump ( mef genes) and erythromycin-ribosomal methylases ( erm genes) sites, to lincosamines (14%), to tetracycline, to folate-inhibitors (14–21%), and to fluoroquinolones (1–2%) with mutations in genes that code for DNA gyrase and topoisomerase IV sites. Emergence of the multidrug-resistant S. pneumoniae serotype 19A is due in part to routine use of protein-conjugated pneumococcal vaccine in the US, since this serotype is not included in the vaccine.