What are Narrow Spectrum Antibiotics

What are Narrow-Spectrum Antibiotics? (Explained)

by | Updated: Apr 18, 2024

Antibiotics have become an integral part of human life in the fight against bacterial infections. They are classified according to the spectrum of bacteria they target.

As the medical field continues to improve health outcomes, antibiotics are further divided into broad and narrow-spectrum antibiotics. The difference is that broad-spectrum antibiotics can eradicate several strains of bacteria, while narrow-spectrum antibiotics focus on specific bacteria.

Our focus today will mainly be on the narrow spectrum; read on to learn more.

What are Narrow-Spectrum Antibiotics?

As the name suggests, the narrow spectrum antibiotics narrow the treatment to a specific bacterium. These medications focus on specific infections when the causative organism is known.

Compared to broad-spetrum antibiotics, they will not kill as many bacterial organisms but eliminate the particular organisms caused by that illness.

Antibiotics mechanisms of action illustration

Types of Narrow-Spectrum Antibiotics

As clinical trials and developments are going on, we currently have 17 products with seven small molecules and ten biologics. Some types of medication used in narrow-spectrum treatment options include:

  • Azithromycin
  • Clarithromycin
  • Erythromycin
  • Clindamycin

However, as research continues, we will continue to add more medication specific to treating these bacterial illnesses.

Advantages of Narrow-Spectrum Antibiotics

There are some primary advantages to using narrow-spectrum antibiotics, including the following:

  1. Specific illness treatment
  2. Reduces antibiotic resistance

Specific Illness Treatment

Once a test is run on a patient, they identify the specific illness they are suffering from. For diseases with narrow-spectrum treatment antibiotics, the patient is given medication that only focuses on destroying that bacterium.

It ensures that the patient is not subjected to medication that will destroy other bacteria as it treats the one that is causing the illness.

Reduces Antibiotic Resistance

With broad-spectrum antibiotics, there is a known risk of antibiotic resistance. How is this the case?

Antibiotics treat a wide range of illnesses, and continued use may result in the body gaining resistance to antibiotics. It is because a patient given broad-spectrum antibiotics eliminates most of the bacteria in the body.

In this process, they destroy the bacteria causing the illness. With a narrow spectrum, they are out only to kill the specific bacteria, reducing instances of antibiotic resistance by the body.

Disadvantages of Narrow-Spectrum Antibiotics

As much as the treatment with a narrow-spectrum antibiotic appears straightforward, it is faced with the challenges of bacterial distinction. This is especially true in cases where a particular illness is caused by multiple, while others by polymicrobial.

In such a case, the narrow-spectrum antibiotics might not be as effective. In a case where a patient is experiencing severe symptoms, go further to determine what specific bacteria might lead to blood infections and sepsis. It may lead to increased mortality as you require further tests to run on the patient.

Therefore, research and developments around narrow-spectrum bacteria aim to ensure that people get the fastest treatment within the shortest period to reduce mortality and, in turn, improve patient outcome results.

Broad-Spectrum vs. Narrow-Spectrum Antibiotics

Broad-spectrum antibiotics are antibiotics that treat a wide range of bacteria. It includes the treatment of both gram-positive and gram-negative bacteria. They are majorly used when the case is unidentified.

A situation that this is highly applied is when a patient visits the doctor and is severely unwell. The doctor will run the first test. Once they identify the patient is suffering from a bacterial infection, they will highly recommend a broad-spectrum antibiotic as they do not know the exact cause of the infection.

This immediate treatment action reduces mortality, blood infections, and sepsis.

Narrow-spectrum antibiotics are applied when the bacteria causing the illness is known to the doctor. It is the preferred treatment therapy as it has reduced bacteria-related risks.

Narrow-Spectrum Antibiotics for Tuberculosis

Tuberculosis has, over the years, been one of the leading causes of infections. There is continuous research to understand the bacterium and treatment. A few narrow-spectrum antibiotics are used to treat tuberculosis, including:

  • Isoniazid
  • Pyrazinamide
  • Ethambutol.

However, the most common approach for TB treatment is the trial antibiotic. It is where the patient is subjected to treatment with broad-spectrum antibiotics drugs.

The assumption in this is that if a different bacterium causes respiratory issues, it will respond to the treatment. If it is not, there is an active TB bacteria and the need to employ the narrow-spectrum approach. However, research in this field is ongoing.

Narrow-Spectrum Antibiotics for C. Diff

C. diff is a toxic-producing bacteria that causes colon inflammation. For this particular illness, there has been a breakthrough in identifying a narrow-spectrum antibiotic that leaves the safe bacteria on its quest to destroy C. diff.

The medication used in this case is mostly fidaxomicin. Initially, there was a significant reliance on the broad spectrum. However, it significantly contributes to drug resistance and reinfections.

Narrow-Spectrum Antibiotics for Community-Acquired Pneumonia

Community-acquired pneumonia in cases where it is less severe, narrow-spectrum antibiotics are recommended. It is also as effective as the broad spectrum, however.

The uptake for this treatment has been relatively low as many doctors still prefer the broad spectrum with no significant concerns over the narrow-spectrum approach.

Final Thoughts

Narrow-spectrum antibiotics should be viewed as one of the best inventions for the future of health. The risks associated with broad-spectrum antibiotics are high and cannot be ignored. The first would be drug resistance.

The first risk of drug resistance by the body would mean a high mortality rate when a person suffers from a severe infection, as the broad spectrum would be the first treatment option. Continuous treatment with a broad spectrum also poses the risk of reinfection.

It is because the drugs are not particular to the specific causative bacteria of the current illness and might be missed in the treatment process.

Even as research on narrow-spectrum antibiotics continues, there is an underlying advantage of the breakthrough in treatment for many bacterial infections. Optimal treatment outcomes are the objectives.

As always, consult with your healthcare practitioner, as there are risks and benefits to every treatment plan.

Dr. Diana Rangaves, PharmD

Written by:

Dr. Diana Rangaves, PharmD
Dr. Diana Rangaves is a pharmacist, philanthropist, and ethics professor turned writer. An accomplished educator and award-winning teacher, her work has been published in numerous medical books and scholarly articles.


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