Penicillin has good antibacterial effect on Streptococcus such as hemolytic Streptococcus, Streptococcus pneumoniae and Staphylococcus that does not produce penicillinase. It has moderate antibacterial effect on enterococci, and Neisseria gonorrhoeae, Neisseria meningitidis, Corynebacterium diphtheriae, Bacillus anthracis, Actinomyces bovis, Streptobacillus candida, Listeria monocytogenes, Leptospira and Treponema pallidum are sensitive to this product. This product also has certain antibacterial activity against Haemophilus influenzae and Bordetella pertussis, and other Gram-negative aerobic or facultative anaerobic bacteria are less sensitive to this product. This product has good antibacterial effect on Clostridium, Peptostreptococcus anaerobic bacteria and melanin-producing Bacteroides, but has poor antibacterial effect on Bacteroides fragilis. Penicillin exerts its bactericidal effect by inhibiting bacterial cell wall synthesis.

This product is a semi-synthetic penicillin, which is acid-resistant and penicillinase-resistant. It has antibacterial activity against Gram-positive cocci and Neisseria. Its antibacterial activity against enzyme-producing strains of Staphylococcus (including Staphylococcus aureus and coagulase-negative Staphylococci) is stronger than that of oxacillin, but its antibacterial effect against penicillin-sensitive Staphylococci and various streptococci is weaker than that of penicillin, and it is ineffective against methicillin-resistant Staphylococci.

Ampicillin sodium is a broad-spectrum semi-synthetic penicillin. This product has a strong antibacterial effect on hemolytic streptococci, Streptococcus pneumoniae and non-penicillinase-producing Staphylococci, which is similar to or slightly inferior to penicillin. Ampicillin also has a good antibacterial effect on viridans streptococci, and is better than penicillin on enterococci and Listeria. This product has antibacterial activity against Corynebacterium diphtheriae, Bacillus anthracis, Actinomyces, Haemophilus influenzae, Bordetella pertussis, Neisseria and anaerobic bacteria except Bacteroides fragilis. Some Proteus mirabilis, Escherichia coli, Salmonella and Shigella are sensitive to this product. Ampicillin exerts its bactericidal effect by inhibiting bacterial cell wall synthesis.

Amoxicillin is a broad-spectrum penicillin antibiotic, which can be used in combination with potassium clavulanate to protect it from hydrolysis by β-lactamase. It has a good effect on enzyme-producing Staphylococcus aureus, Staphylococcus epidermidis, coagulase-negative Staphylococci and enterococci, and also has good antibacterial activity against certain β-lactamase-producing Enterobacteriaceae, Haemophilus influenzae, Moraxella catarrhalis, Bacteroides fragilis, etc.

Potassium clavulanate itself has only weak antibacterial activity, but it has a strong broad-spectrum β-lactamase inhibitory effect. When used in combination with amoxicillin, it can protect it from β-lactamase hydrolysis.

Ampicillin sodium is a broad-spectrum semi-synthetic penicillin. This product has a strong antibacterial effect on hemolytic streptococci, Streptococcus pneumoniae and non-penicillinase-producing Staphylococci, which is similar to or slightly inferior to penicillin. Ampicillin also has a good antibacterial effect on viridans streptococci, and is better than penicillin on enterococci and Listeria. This product has antibacterial activity against Corynebacterium diphtheriae, Bacillus anthracis, Actinomyces, Haemophilus influenzae, Bordetella pertussis, Neisseria and anaerobic bacteria except Bacteroides fragilis. Some Proteus mirabilis, Escherichia coli, Salmonella and Shigella are sensitive to this product. Ampicillin exerts its bactericidal effect by inhibiting bacterial cell wall synthesis.