Streptococcus pseudopneumoniae

Streptococcus pseudopneumoniae is a gram-positive coccus that may cause pneumonia in humans. It was first described in 2004. The organism is often mistaken for S. pneumoniae and its clinical importance is as yet uncertain. It seems likely that most cases of S. pseudopneumoniae pneumonia are misdiagnosed as S. pneumoniae.
The bacterium has a number of features that allows it to be distinguished from S. pneumoniae:

There is no pneumococcal capsule.
It is not soluble in bile.
It is sensitive to optochin when incubated in ambient air, but appears resistant or to have indeterminate susceptibility when incubated in 5% carbon dioxide.
Commercial DNA probe hybridization tests are falsely positive.

Penicillin is the treatment of choice. Most reported isolates are resistant to erythromycin and to tetracycline.