Pathogen Series | No. 02
Pseudomonas aeruginosa, Carbapenem-resistant
Environmental Persistence, Healthcare Significance
and the Role of UV Disinfection
Pseudomonas infection is caused by strains of bacteria found widely in the environment such in soil and water; the most common type causing infections in humans is called Pseudomonas aeruginosa. This is an opportunistic pathogen that causes infections in the blood, lungs (pneumonia), or other parts of the body after surgery, causing an estimated 51,000 healthcare-associated infections (HAI) in the United States annually. Those most at risk of acquiring P. aeruginosa infections are those on ventilators, have catheters in situ or those with burns or surgical wounds.
P. aeruginosa infections are associated with high morbidity and mortality rates especially in hospitalized patients with weakened immune systems, because it is very difficult to treat. Recent research on bloodstream infections showed that patients with a Pseudomonas infection had a higher mortality rate than patients with infections caused by other Gram-negative bacilli. P. aeruginosa is often diffi cult to treat because of its intrinsic (natural) resistance to many commonly used antimicrobial drugs; ≈13% of isolates causing HAI are multidrug resistant (MDR). Therefore car bapenems have become important antimicrobial drugs for clinical management of serious P. aeruginosa infections. However, there are more strains carrying carbapenemases (see Enterobacteriacae for description of carbepenemases).
P. aeruginosa is notorious for causing water related problems in health care settings and is highlighted as a problematic organism because of its ability to form biofilm (A biofilm is a surface bound community of organisms residing within a polymeric matrix). This makes the organism in the environ ment very difficult to kill with antiseptics because many of them are unable to penetrate the biofilm. In a study using silicone and Teflon tubing, biofilm was eradicated using UV-C. 10cm Teflon and silicone tubes and 20 cm Teflon tubes were contaminated with P. aeruginosa and biofilms allowed to form. The tubes were sampled from the total inner surface of the tubes and a reduction in colony counts were between 96-100%. Colony counts on the control samples were between 105–109 CFU ml−1. The applied UV-C doses were between 15 and 300 min. Disinfection (100%) was obtained in 10 cm Teflon tubes exposed for 30 min and a 20 cm Teflon tube exposed for 300 min. The disinfection rate was 96% for the 20 cm tube if the dose was reduced to 30 min. Differences between the tubes were dependent on the differences in length and the type of material. The UV-C light was transmitted six times more efficiently in Teflon than in silicone tubes of equal length (10 cm). The germicidal effect to obtain a 99.99% killing rate for the biofilm (∼78 J m−2) is comparable to that for the planktonic bacterium. Jimmy Bak, Søren D. Ladefoged, Michael Tvede, Tanja Begovic & Annette Gregersen (2010) Disinfection of Pseudomonas aeruginosa biofilm contaminated tube lumens with ultraviolet C light emitting diodes, Biofouling, 26:1, 31-38
Pathogen Size
1-5 μm long
General Description
Gram negative bacillus (rod shaped)
Infection Risk From Environment
HIGH
Survives On Surfaces
6 hours - 16 months, on dry floor - 5 weeks*
Frequently Isolated From
Augmented Care Units
UV Relevence
Pseudomonas aeruginosa is one of the microorganisms most frequently evaluated in published UV-C disinfection research due to its clinical significance as a healthcare-associated pathogen and its ability to persist in moist hospital environments. It is also included within BS 8628 as one of the representative microorganisms used when assessing the microbiological performance of automated whole-room UV disinfection systems. Numerous peer-reviewed studies have investigated the susceptibility of P. aeruginosa to UV-C irradiation under controlled laboratory conditions. In clinical practice, the effectiveness of UV disinfection depends on a range of operational factors, including device positioning, shadowing, exposure time and surface accessibility. Consequently, real-world validation is an important component of ensuring that representative environmental surfaces receive the intended UV exposure.
Further Reading
* Kramer, Schwebke & Kampf (2006) Kramer A, Schwebke I, Kampf G. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infectious Diseases. 2006;6(1):130. doi: 10.1186/1471-2334-6-130
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