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Understanding antibiotic resistance
Understanding antibiotic resistance

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2.1 Classification

There are numerous different antibiotics, some of which are naturally occurring while others are semi- or fully synthetic. Don’t worry if you don’t understand these terms, as they will be explained later. One of the most useful ways of classifying antibiotics is by chemical structure because structurally similar antibiotics tend to have similar antibacterial activity.

Examples of common antibiotic classes are shown in Table 1.

Table 1 Common classes of antibiotic
Antibiotic classExampleCellular process targeted*Effect on bacteria**
ß-Lactams (penicillins)ampicillinbacterial cell wall synthesisbactericidal
ß-Lactams (cephalosporins)cephazolinbacterial cell wall synthesisbactericidal
ß-Lactams (carbapenems)imipenembacterial cell wall synthesisbactericidal
Glycopeptidesvancomycinbacterial cell wall synthesisbactericidal
Aminoglycosidesstreptomycinprotein synthesisbactericidal
Macrolidesazithromycin protein synthesisbacteriostatic
Tetracyclinestetracyclineprotein synthesisbacteriostatic
Oxazolidinoneslinezolidprotein synthesisbacteriostatic
FluoroquinolonesciprofloxacinDNA synthesisbactericidal
RifamycinsrifampicinRNA synthesisbactericidal
Not applicabletrimethoprimmetabolic reactionsbactericidal
(Source: OpenStax College Microbiology, n.d.)


* You will learn more about these cellular processes in Week 2.


** Common effect but partly depends on the concentration at which the antibiotic is used.