FAQ 1: What is the basic difference between antibiotics and antimicrobials?


Antibiotic vs Antimicrobial 

Antimicrobials are agents that act across a wide range of organisms including bacteria, viruses, fungal, protozoa, and helminthes. Antibiotics belong to a sub category of that large group and include substances that have the ability to kill and stop the growth of bacteria. This article emphasizes on the differences between these two terms which would be helpful for better understanding.


As mentioned above, the antimicrobials act against a variety of organisms. Some of the antimicrobials act across several organisms such as metronidazole, which inhibits obligate anaerobic bacteria, as well as some protozoa. To be an ideal antimicrobial drug, it should interfere with the vital functions of pathogens, without affecting the host cell.

According to the organism on which they act they are broadly classified as antibacterial, antifungal, antiviral and anti protozoa. They act together with the natural defenses of the body and act on different sites in the target organism such as cell wall, cytoplasmic membrane, protein synthesis and nucleic acid metabolism.


Antibiotic are substances that kill and stop the growth of micro organisms. They act by Interfering with the cell wall synthesis; inhibiting protein synthesis, and by interfering with the nucleic acid metabolism.

They are broadly classified as bacteriostatic, which acts primarily by inhibiting bacterial multiplication, and bactericidal, which acts primarily by killing the bacteria. But this is being used less frequently in the current clinical practice since most bacteriostatic drugs were shown to be bactericidal at high concentrations.

Before starting the antibiotic therapy, it should be based on the likely organisms involved, prevalence of the resistance of the organism, relevant pharmacology, and presence of allergy or host factors that may modify pharmacology, the degree of the severity, urgency and the availability of the culture and sensitivity results. To be an ideal antibiotic, it should be cheaper, freely available with a good compliance of the patient, available in oral forms, the least toxic, and have fewer side effects.

Antibiotics are used to deal with systemic infections, post-operative infections, and during surgical procedures. In surgical practice, antibiotics are generally not used in clean surgeries, except in surgeries that are more than 4 hours of duration, neurosurgeries, cardiothoracic surgeries, implants, and in immune compromised patients. For clean contaminated, contaminated and dirty surgeries, antibiotics are invariably used.

Best route of the administration of the antibiotics are per oral while intravenous and intramuscular routes are used in the case where there are severe infections, septicemia and in instances where the gastro intestinal system is compromised so that the absorption is poor. Adverse effects of the antibiotics vary depending on the category they belong, and they range from mild to severe anaphylactic shock.

What is the difference between Antimicrobial and Antibiotic?

• Antimicrobials act against a wide variety of organisms while antibiotics act only against bacteria.

• Antimicrobials include antibacterial, antifungal, antiviral, anti helminthes and anti protozoa.

• Unlike in most of the antimicrobials, resistance is a problem with antibiotics.

• Adverse effects vary depending on the type of drug.


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