Antibiotics are used to prevent and treat bacterial lung infections in people with cystic fibrosis. The type of antibiotic you receive depends on what type of infection you have or are trying to prevent.

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Cystic fibrosis is a genetic disease in which your body produces too much mucus, digestive enzymes (proteins that help your body digest food), and sweat.

It’s caused by a mutation in a gene that codes for a protein called the cystic fibrosis transmembrane conductance regulator (CFTR).

The buildup of mucus in the lungs of people with cystic fibrosis can trap bacteria and other microorganisms. Repeated bacterial infections are one of the hallmark features of cystic fibrosis. Antibiotics are essential for preventing or treating these infections.

Antibiotics are often combined with new treatment options like CFTR modulators. Thanks to advances in cystic fibrosis treatment, about half of people with it now live past 40 years old. This rate will likely continue to rise.

Read on to learn how antibiotics are used as a treatment for cystic fibrosis and which antibiotics are most prescribed.

Learn more about cystic fibrosis.

Antibiotics are a group of medications that kill bacteria. The goal of antibiotic therapy for people with cystic fibrosis is to preserve or improve their lung function by:

  • preventing new infections
  • reducing flare-ups of current infections
  • managing long-term infections

Most people with cystic fibrosis eventually die of respiratory failure from structural damage to the small airways in their lungs. Repeated infections contribute to the breakdown of these structures. Antibiotics play a critical role in slowing down lung damage.

Antibiotics are necessary whenever an infection has caused a noticeable decline in lung function and symptoms such as shortness of breath or wheezing. Flare-ups of bacterial infections or new infections are often treated with oral or intravenous (IV) antibiotics. Inhaled antibiotics are often used for chronic infections.

The Cystic Fibrosis Foundation recommends using inhaled antibiotics after bronchodilators, mucus thinners, and airway clearance techniques to help the medication better reach the deep parts of your lungs.

There are many types of antibiotics available. Doctors and other healthcare professionals prescribe antibiotics based on the specific strand of bacteria you have and whether your infection is short term or long term. The severity of your condition and the specific organism will determine if treatment will be most effective orally, IV, or inhaled.

The most common lung infections in people with cystic fibrosis are S. aureus and Pseudomonas aeruginosa (P. aeruginosa).

Here’s a look at some of the most common antibiotics for these strands of bacteria.

Staphylococcus aureus

The first-line treatment for a new S. aureusinfection is often a combination of:

DrugsDosage (milligrams per kilogram per day)RouteTimes per dayLength (weeks)

100oral3 to 42 to 4
Fusidic acid

25 to 50oral, IV2 to 32 to 4
Rifampicin15 to 20oral, IV22 to 4

The Cystic Fibrosis Foundation lists the following combinations of antibiotics as the most common for treating S. aureus infection:

Amoxicillin and clavulanic acidoral
Cephalexin, cefdiniroral
Sulfamethoxazole and trimethoprimoral
Tetracycline, doxycycline, minocycline, tigecyclineoral, IV, intramuscularly (injection through a muscle)
Clindamycinoral, IV
Linezolidoral, IV
Nafcillin, oxacillinIV
Piperacillin with tazobactamIV
Meropenem, imipenem/cilastatin, doripenem, meropenem-vaborbactam, ertapenemIV

P. aeruginosa

The first-line treatment for new P. aeruginosa infections or flare-ups are usually one of the following:

Ciprofloxacin/tobramycin or colomycinoral/inhaled
Ceftazidime IV
Meropenem IV
Colomycin and amikacin or tobramycininhaled

The Cystic Fibrosis Foundation lists the following as the most common antibiotic combinations for P. aeruginosa infection:

Sulfamethoxazole with trimethoprimoral
Doxycycline, minocyclineoral
Azithromycinoral, IV
Ciprofloxacin, levofloxacinoral, IV
Linezolidoral, IV
Rifampin, combined with other active ingredientsoral, IV
Clindamycinoral, IV
Tobramycin, amikacin, gentamicinIV, inhaled
AztreonamIV, inhaled
ColistimethateIV, inhaled
Piperacillin and tazobactamIV
Ceftazidime, Ceftazidime-avibactamIV
Meropenem, meropenem-vaborbactam, imipenem with cilastatin, doripenemIV
Doxycycline, tigecyclineIV

The next step after you take antibiotics depends on whether you’re taking them for a chronic infection or a sudden infection.

A doctor will want to monitor how well you’re responding to the antibiotic so they can decide if you may need another type of treatment. If oral antibiotics aren’t effective, you may need antibiotics administered through an IV line.

Antibiotics for chronic infections are often inhaled. Inhaling antibiotics instead of taking them orally or through an IV line can help minimize side effects and increase the amount of the antibiotic that’s delivered straight to your lungs.

Inhaled antibiotics fail to eradicate P. aeruginosa infection in about10% to 40% of people who have it.

Antibiotics are important for preventing and treating infections, but they can cause side effects. Some of their potential side effects include:

Learn more about antibiotic side effects.

Bacteria can sometimes mutate so that antibiotics no longer affect them. This is called antibiotic resistance. The continued use of antibiotics increases your chances of developing antibiotic resistance.

Doctors can decrease your chance of developing antibiotic resistance by tailoring your treatment to the specific type of bacteria you have. If you don’t respond to treatment, you may need to change your dosage or change your type of antibiotic.

It’s best to follow directions provided by a healthcare professional and to finish the course of prescribed antibiotics even if you start to feel better to prevent antibiotic resistance.

Researchers continue examining new antibiotics for treating infections in people with cystic fibrosis. There are relatively few inhaled antibiotics currently available. Researchers are continuing to look at new drugs that might help prevent or treat lung infections.

Some of the clinical trials currently underway or are currently recruiting include:

  • inhaled sodium nitrite as an antimicrobial for cystic fibrosis
  • Trikafta/Kaftrio and P. aeruginosa
  • cefiderocol pharmacokinetics in adults with cystic fibrosis
  • imipenem/cilastatin/relebactam pharmacokinetics, safety, and outcomes in adults and adolescents with cystic fibrosis
  • DPI-Tobra-Kind Cyclops® in children with cystic fibrosis

Here are some frequently asked questions people have about antibiotics and cystic fibrosis.

Which antibiotic will my doctor recommend?

Many different types of antibiotics are used to treat and prevent infections in people with cystic fibrosis. The type of antibiotics you take depends on which type of infection you have, which antibiotics you’ve already tried, and whether your infection is chronic.

Do I need to take antibiotics if I’m taking a CFTR modulator?

More long-term studies are needed to see if it’s safe for people taking CFTR modulators to stop taking daily antibiotic therapy. Currently, it’s generally recommended to continue your current treatment regimen.

What are S. aureus and P. aeruginosa infections?

S. aureus and P. aeruginosa are the two most common bacterial infections in people with cystic fibrosis.

S. aureus is normally found on human skin and mucous membranes. Drug-resistant strains can cause severe lung disease in people with cystic fibrosis.

P. aeruginosa is commonly found in soil and water. It’s a major cause of lung infection in people with cystic fibrosis.

Antibiotics are used to treat and prevent lung infections in people with cystic fibrosis. Antibiotics are administered orally, through an IV line, or inhaled. The type of antibiotic a doctor recommends depends on which type of infection you have.

It’s important to follow a doctor’s instructions for any antibiotics you’re prescribed. Not taking antibiotics as prescribed can increase the chance that they’ll not be as effective or increase your chance of antibiotic resistance.