In general , new acquisition of pneumococci nonsusceptible to penicillin , erythromycin , clindamycin , penicillin plus erythromycin , and multiple drugs ( 3 antibiotics ) was significantly lower in the PCV13 group compared with the PCV7 group ; the main serotypes contributing to this significant decrease were serotype 19F , present in PCV13 and PCV7 , and serotypes 6A and 19A , present in PCV13 only .