The difference of streptococcal, streptococci, etc. - (May/30/2015 )

Hello. I need help about some general things that i don't quite understand.

1. What is the difference between (i only use strepto as example) :

Streptococcal, Streptococci, Streptococcus sp., Streptococcus spp?

2. If i want to identify the species of a lactic acid bacteria, phenotypically, should i use kit API 50 CHL only, or there is another method?

Thank you for your kind attention.

1) these are the different forms of the word; verb, plural, singular (sp = species), singular (spp = plural species).