When P. aeruginosa is isolated from a normally sterile site (blood, bone, deep collections), it is generally considered dangerous, and almost always requires treatment. [ citation needed ] However, P. aeruginosa is frequently isolated from nonsterile sites (mouth swabs, sputum , etc.), and, under these circumstances, it may represent colonization and not infection. The isolation of P. aeruginosa from nonsterile specimens should, therefore, be interpreted cautiously, and the advice of a microbiologist or infectious diseases physician/pharmacist should be sought prior to starting treatment. Often, no treatment is needed.
β proteobacteria: P. acidovorans , P. alliicola , P. antimicrobica , P. avenae , P. butanovorae , P. caryophylli , P. cattleyae , P. cepacia , P. cocovenenans , P. delafieldii , P. facilis , P. flava , P. gladioli , P. glathei , P. glumae , P. graminis , P. huttiensis , P. indigofera , P. lanceolata , P. lemoignei , P. mallei , P. mephitica , P. mixta , P. palleronii , P. phenazinium , P. pickettii , P. plantarii , P. pseudoflava , P. pseudomallei , P. pyrrocinia , P. rubrilineans , P. rubrisubalbicans , P. saccharophila , P. solanacearum , P. spinosa , P. syzygii , P. taeniospiralis , P. terrigena , P. testosteroni .
Infections in humans due to P. aeruginosa can be divided into opportunistic infections and those infections occurring in a healthy host. P. aeruginosa infections occur when the immune system is breached, either locally or systemically. Human hands infrequently are colonized with P. aeruginosa; however hospitalization increases the likelihood of finding the bacteria on intact skin. Therefore skin colonization can lead to bacteremia from catheter-related infection, or gastrointestinal colonization can lead to aspiration and pneumonia. Splashing of water from a contaminated sink, or droplets suctioned from a colonized endotrachial tube, can easily facilitate spread of P. aeruginosa . In the normal host, P. aeruginosa , in the proper setting can cause locally invasive disease. Large inocula of the bacteria can overwhelm normal defenses and lead to infection.