Are penicillins effective against gram-positive bacteria? Can't take sulfa, fluoroquinolones, or cephalosporins.

Penicillin are ok. Penicillins are effective against gram + organism(G+), however you will need a culture to properly identify the bacteria.there is different type of penicillin base antibiotics and they can treat a variety of infections caused by(G+), such as otitis, pharyngitis, skin infection, etc. Again it will depend on the type of infection as well as the organism you are treating. Can also use tetracycline.