Ampicillin is a penicillin beta-lactam antibiotic. The following gram-negative and gram-positive bacteria have been shown in in vitro studies to be susceptible to ampicillin: Hemolytic and nonhemolytic streptococci, Streptococcus pneumoniae, Nonpenicillinase-producing staphylococci, Clostridium spp., B. anthracis, Listeria monocytogenes, most strains of enterococci, H. influenzae, N. gonorrhoeae, N. meningitidis, Proteus mirabilis, many strains of Salmonella, Shigella, and E. coli. Ampicillin is indicated in the treatment of bacterial meningitis, septicemia, endocarditis, urinary tract, gastrointestinal, respiratory tract infections caused by susceptible strains of the designated organisms.

Bacampicillin is a penicillin antibiotic. It is a prodrug of ampicillin with improved oral bioavailability. It exerts bactericidal activity via inhibition of bacterial cell wall synthesis by binding one or more of the penicillin binding proteins (PBPs). Spectrobid is used to treat bacterial infections such as tonsillitis, pneumonia (lung infection), bronchitis (inflammation of airway), urinary tract infections, gonorrhea, and infections of the skin. Adverse effects are: anemia, thrombocytopenia, neutropenia, agranulocytosis, seizures, nephrotoxicity, Jarisch-Herxheimer Reaction (fever, chills, sweating, tachycardia, hyperventilation, flushing, and myalgia). Drug interactions: Contraceptives - decreased contraceptive effectiveness; Live Typhoid Vaccine - decreased immunological response to the typhoid vaccine; Probenecid - increased bacampicillin levels.