The Prevalence and Significance of Staphylococcus aureus in Patients with Non–Cystic Fibrosis Bronchiectasis – A Bronchiectasis and NTM Research Registry Study

Posted on October 19, 2021   |   
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This blog post was written by Christina Hunt, BS, RRT, Director of Bronchiectasis and NTM Research and Education.

Non-cystic fibrosis (CF) bronchiectasis is a lung disease characterized by permanent widening of the airways. Patients with bronchiectasis are often burdened by frequent exacerbations (also known as flare-ups) caused by mucus pooling in the airways which can be a host for various types of bacteria. Staphylococcus aureus (staph aureus) is a type of bacteria commonly found in the sputum of patients with bronchiectasis; and yet, little is known about how frequently it is found, which bronchiectasis patients are prone to infection, and the long-term consequences of infection with staph aureus.

Recently, researchers sought to answer these questions by analyzing data the Bronchiectasis and NTM Research Registry (BRR). Data from the Registry was used to compare patients with and without staph aureus to identify any associations between staph aureus infection and pulmonary function tests (breathing tests to determine health and functionality of the lungs), the frequency of exacerbations or “flare-ups”, and the frequency of hospitalizations.

Researchers identified 830 non-CF bronchiectasis patients for the study and placed them into three groups based on status at time of enrollment in the Registry: Group 1) patients with no bacteria known to be associated with worsened outcomes in their sputum; Group 2) patients with staph aureus in their sputum; and Group 3) patients who had other bacteria (e.g., Pseudomonas aeruginosa or Stenotrophomonas) but not staph aureus in their sputum.

Eighty-two percent of participants included in the analyses were female and the mean age was 64 ± 14 years. Most patients (67%) had suffered a flare-up within two years of study enrollment. The average FEV1 (a pulmonary function test value referencing the maximum amount of air forcefully blown out of the lungs in one second) was 70% of predicted, which suggests mild obstructive lung disease. Ninety-four (11.3%) of participants grew staph aureus in their sputum culture at least once during their baseline period, and approximately one third of those patients also grew other bacteria in their sputum culture.

Researchers also found that patients with staph aureus were more likely to: 1) be female, 2) have an exacerbation during the prior two years of the study, and 3) have lower pulmonary function test (PFT) results than the group with no bacteria in their culture (Group 1). Additionally, of the patients in Group 2 (those with staph aureus infections), 33% had methicillin-resistant bacteria (specific bacteria that are resistant to commonly used antibiotics –“MRSA”) , there were however no significant differences between the MRSA (methicillin-resistant staph aureus) and MSSA (methicillin-susceptible staph aureus - treatable with most antibiotics) groups regarding sex, age at enrollment, age at diagnosis, PFT results, or number of flare-ups during the prior two years. No significant difference between the three groups was found regarding the amount of FEV1 decline or outcomes between patients, including hospitalizations and exacerbations.

In summary, based on the BRR data analyzed, it does not appear that Staphylococcus aureus causes worsened outcomes in patients with non-CF bronchiectasis compared to other bacteria. Staph aureus does not tend to increase the likelihood of exacerbations and hospitalizations or worsening of pulmonary function tests. However, the presence of staph aureus could be considered a marker for more severe disease; further research is needed to better examine this theory.