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.

Amdinocillin is a novel, semisynthetic penicillin effective against many gram-negative bacteria. The antibacterial activity of amdinocillin is derived from its ability to bind specifically and avidly to Penicillin Binding Protein-2 (PBP 2). Amdinocillin is active alone against many gram-negative organisms. Pseudomonas and non-fermenting gram-negative bacteria, however, are usually resistant. Amdinocillin, in combination with many beta-lactams, exhibits marked synergy against many enterobacteriaceae. No such synergy can be demonstrated for gram-positive organisms or pseudomonas species. Amdinocillin is not beta-lactamase stable. Organisms which produce high levels of plasma-mediated beta-lactamase are resistant to the drug. Used in the treatment of urinary tract infections caused by some strains of E. coli and klebsiella and enterobacter species. Used mainly against Gram negative organisms. Amdinocillin is not available in the United States.

Amdinocillin is a novel, semisynthetic penicillin effective against many gram-negative bacteria. The antibacterial activity of amdinocillin is derived from its ability to bind specifically and avidly to Penicillin Binding Protein-2 (PBP 2). Amdinocillin is active alone against many gram-negative organisms. Pseudomonas and non-fermenting gram-negative bacteria, however, are usually resistant. Amdinocillin, in combination with many beta-lactams, exhibits marked synergy against many enterobacteriaceae. No such synergy can be demonstrated for gram-positive organisms or pseudomonas species. Amdinocillin is not beta-lactamase stable. Organisms which produce high levels of plasma-mediated beta-lactamase are resistant to the drug. Used in the treatment of urinary tract infections caused by some strains of E. coli and klebsiella and enterobacter species. Used mainly against Gram negative organisms. Amdinocillin is not available in the United States.