Pseudomonas aeruginosa

Pseudomonas aeruginosa, or P. aeruginosa, is a gram-negative bacterium that is abundant in the environment.

It tends to opportunistically infect high-risk individuals, and is well known for its multi-drug resistance, making it hard to treat.

P. aeruginosa is an encapsulated, gram-negative, rod bacterium, that’s an obligate aerobe, so it uses oxygen for metabolism through cellular respiration.

It does not ferment lactose and does not make spores; but it’s catalase, citrate, and oxidase positive.

It has a flagellum, kind of like a tail, at one end for motility; and has multiple hair-like appendages, called pili, all over that help with adhesion to other cells.

It also has a number of multidrug efflux pumps that efficiently pump medications out of the bacteria making it resistant to a variety of antibiotics.

In addition it’s able to make beta-lactamases that degrade beta-lactam antibiotics as well as aminoglycoside-modifying enzymes that alter aminoglycoside antibiotics - rendering them ineffective. In short, it’s defenses are strong.

P. aeruginosa is everywhere in the environment - in soil; in the home, and in hospitals - where it’s found on improperly cleaned medical equipment and devices, various surfaces, and on the hands of health care workers.

It can survive for months on dry surfaces and inanimate objects – but particularly loves humid or wet conditions; like hot tubs, contact lens cases, catheters, and medical ventilators.

Transmission can occur when broken skin or mucous membranes come in contact with contaminated surfaces; or when aerosols containing P. aeruginosa are inhaled after an infected person coughs or sneezes.

Now, a P. aeruginosa infection is actually not too common in the general population.

It’s an opportunistic bacterium, meaning that it frequently causes infections in high-risk individuals like those with cystic fibrosis, chronic granulomatous disease, and type 2 diabetes mellitus.

It’s also common among individuals with an immunodeficiency; IV drug abusers, or those with severe burns or deep wounds.

P. aeruginosa produces several virulence factors to help it invade epithelial cells and survive an attack from the immune system.

First, there’s endotoxin, a molecule that’s made up of a lipid and polysaccharide.