P. aeruginosa can use a wide range of sources to obtain nutrients for growth, and can survive in different levels of oxygen, meaning it can live almost anywhere. It can grow in liquid and as a layer of cells on a surface, called a biofilm, helping it to thrive in both natural and artificial settings. It is commonly found in water, soil, fruit and vegetables.

Infections are usually acquired by touching contaminated fluids and objects. The abundance of P. aeruginosa makes prevention of infection challenging. P. aeruginosa can be a particular issue in some hospital settings especially those with vulnerable patients, as it can contaminate medical equipment such as catheters and ventilation devices.

Drug-resistant P. aeruginosa infections are a global threat. Having spread around the world, P. aeruginosa is estimated to cause around 7% of all healthcare-associated infections, and nearly a quarter of all infections are acquired in intensive care units. It is a leading cause of death in patients with cystic fibrosis. Patients with chronic obstructive pulmonary disease also suffer recurrent exacerbations of Pseudomonas infections.

Several outbreaks of P. aeruginosa have been attributed to contaminated water systems in hospitals, with sinks, drains and toilets in healthcare settings becoming contaminated and infecting patients. This can occur through direct contact, sprays, splashes or through inhalation.

Like other Gram-negative bacteria, P. aeruginosa is naturally resistant to antibiotics because of its protective outer layer, which blocks drugs from entering the bacterial cell. Even if antibiotics do manage to penetrate this outer layer, P. aeruginosa can pump them back out again using numerous efflux pumps.

Moreover, P. aeruginosa has acquired many different drug resistance mechanisms. This can occur through the mutation of genes, such as those encoding proteins targeted by antibiotics, making it harder for drugs to bind to them, or ones that increase the production of efflux pumps, which can decrease the entry of antibiotics into the cell. It can also acquire resistant genes from other bacteria. One way P. aeruginosa does this is by acquiring genes which produce enzymes that inactivate and/or destroy many different classes of antibiotics. Of special concern is the marked rise of P. aeruginosa strains resistant to carbapenems, a class of last-resort antibiotics, because in this case safe and efficacious treatment options are very limited.