What are natural penicillins (narrow-spectrum beta-lactam antibiotics)?

From the Guidelines

Natural penicillins are narrow-spectrum beta-lactam antibiotics.

Characteristics of Natural Penicillins

• They have a narrow spectrum of activity 1
• They are inexpensive and have a long-standing proven efficacy 1
• They are effective against Group A beta-hemolytic streptococcal (GAS) infections 1
• No resistance to penicillin has been documented in GAS 1

Examples of Natural Penicillins

• Penicillin V: an oral form of penicillin 1
• Benzathine penicillin: an injectable form of penicillin 1

Clinical Use of Natural Penicillins

• They are the treatment of choice for GAS tonsillopharyngitis 1
• They are used for primary prevention of acute rheumatic fever 1
• They are used for secondary prevention of rheumatic fever in individuals who have had a previous attack 1

From the Research

Definition and Characteristics of Natural Penicillins

• Natural penicillins are a class of narrow-spectrum beta-lactam antibiotics, with benzylpenicillin (penicillin G) being the first natural penicillin discovered 2.
• They have potent activity against Gram-positive pathogens, Gram-negative cocci, and some spirochaetes and actinomycetes 2.
• Natural penicillins are bactericidal, well distributed, and highly efficacious against susceptible organisms 3.

Spectrum of Activity

• Natural penicillins are effective against streptococcal and staphylococcal infections, as well as some Gram-negative bacteria such as Neisseria gonorrhoeae and certain strains of Escherichia coli 4, 2.
• However, the emergence of resistant bacterial strains, including penicillinase-producing staphylococci, has limited the usefulness of natural penicillins in recent years 4, 2.

Development of Penicillins

• The discovery of 6-aminopenicillanic acid nucleus led to the synthesis of ampicillin and other aminopenicillins, which have improved oral bioavailability and superior activity against certain Gram-negative bacteria 2.
• The development of penicillinase-resistant penicillins, such as methicillin and nafcillin, was prompted by the emergence of penicillinase-producing staphylococci 4, 2.
• The combination of a beta-lactamase inhibitor with a penicillin has resulted in further extension of their antibacterial spectra 4, 2.