Bacteria That Cause Lung Infections Appear to Trigger Immune Defense by ‘Swimming’

Bacteria That Cause Lung Infections Appear to Trigger Immune Defense by ‘Swimming’

The swimming-like movement of Pseudomonas aeruginosa is what induces the release of neutrophil extracellular traps (NETs) to defend against this opportunistic bacteria, a study published in the journal PLOS Pathogens found.

This discovery suggests that targeting genes that control the movement of the flagellum, the tail-like structure that enables the bacteria to swim or move, could be a new therapeutic approach against P. aeruginosa, a pathogen that poses serious problems for people with health conditions such as bronchiectasis.

Neutrophils are cells of the immune system that constitute the first line of defense against invading pathogens. They use various mechanisms to neutralize pathogens, including the formation of NETs. However, factors that trigger NET formation are largely unknown to date.

To identify possible influences, a team of researchers led by Dr. Balázs Rada of the University of Georgia, monitored P. aeruginosa at various phases of growth, and found that NET formation was mostly triggered in the bacteria’s exponential growth phase (an early middle phase of a microbe infection). Its ability to induce NET production dramatically decreased at later stages of growth.

Bacteria deficient in flagellum were not able to trigger NET formation, the researchers saw. This observation led them to conclude that the flagellum is the primary bacteria component responsible for inducing NET production.

Interestingly, when researchers used purified flagellin, the main component of the flagellum, they discovered that NET formation was not stimulated. Similarly, bacterial strains that had immobile or paralyzed flagella were not able to induce NET formation.

“…Flagellar motility [in biology, the ability to move], not flagellum binding to neutrophils per se, mediates NET release induced by flagellated bacteria,” the researchers concluded in their study, “Swimming Motility Mediates the Formation of Neutrophil Extracellular Traps Induced by Flagellated Pseudomonas aeruginosa.

This is the first study that identifies the movement of the bacterial flagellum as a trigger of immune response.

P. aeruginosa is an opportunistic pathogen, which mainly causes lung infections in patients with compromised immune systems, such as patients with bronchiectasis, cystic fibrosis, and chronic obstructive pulmonary disease (COPD). It is a serious clinical problem.

This study provides novel insight into NET formation induced by Paeruginosa, and sheds light onto the interaction between the body’s immune system and pathogenic bacteria that constitute a threat in many respiratory diseases.