Pneumococcal surface adhesin A (PsaA) is a surface-exposed common 37-kilodalton multi-functional lipoprotein detected on all known serotypes of Streptococcus pneumoniae. This lipoprotein belongs to the ABC-type transport protein complex that transports Mn2+; it is also an adhesin that plays a major role in pneumococcal attachment to the host cell and virulence.