When Tara helps Cameron, she give him the antibiotic "Vancomycin", then a few minutes later she referred to the antibiotic as "Penicillin".
Tara instructs the SOA crew to give Hayes Vancomycin then later says the penicillin will kill the infection. Vancomycin is a glycopeptide, not a penicillin.
Oral Vancomycin is only used for killing intestinal C. diff infections and also won't "kill anything" since it covers mostly gram positive bacteria-also treating with Vancomycin when not needed puts the person at risk for Vancomycin Resistant Enterococcus infections in the future- vancomycin is mostly used to kill MRSA.
When Tara goes to the clubhouse to help Cameron Hayes, who has been shot, she gives him the antibiotic Vancomycin in pill form. Oral Vancomycin only treats infections within the gut. It would not work for other infections.