Gram positive: Most streptococci, Streptococcus pneumoniae, Streptococcus anginosus group, Enterococcus faecalis, Listeria monocytogenes

Gram negative: Pasturella multocida, E.Coli (but most strains are now resistant), H.influenzae (resistance increasing globally)

Anaerobic: Actinomyces, Prevotella melaninogenica, Peptostreptococci