Pseudomonas Bacteria

The Pseudomonas group of bacteria comprises many species characterized by their metabolic diversity and by the wide range of environments they colonize. Some species have medical importance while others are plant pathogens or plant beneficial bacteria. These bacteria are motile; they require oxygen for growth and reproduction but sometimes can use nitrate; they do not form spores.¹

Human Pathogens

Pseudomonas aeruginosa
Courtesy of CDC

Pseudomonas aeruginosa is a ubiquitous environmental bacterium. Considering the vast array of virulence factors and toxins produced by this bacterium, it is surprising that is not a primary pathogen. The main infections it causes are those of the skin and eye, wounds and burns, bones and joints, and chest infections in people with cystic fibrosis.⁵ Acute infections with P. aeruginosa can be life threatening , resulting in severe tissue damage and bloodstream invasion; they are usually difficult to eradicate due to its remarkable tolerance to many antimicrobial drugs. It has been shown that through mutation, the P. aeruginosa is capable of developing resistance to antibiotics that the strain is not inherently resistant to.² Many Pseudomonas species produce a slime layer that is resistant to phagocytosis.⁴

Pseudomonas folliculitis, or hot tub folliculitis is an infection of hair follicles. Outbreaks occur in people after bathing in a contaminated spa, swimming pool, or hot tub. It is also associated with usage of loofah sponges (that remain constantly wet in the shower) and contaminated water in the workplace. It also can be seen in individuals on long-term antibiotic therapy for acne vulgaris.³

Animal Pathogen

Although there are numerous pseudomonads, only one species, Pseudomonas aeruginosa, is an important pathogen in animals. Its natural habitat is water, soil, and decaying vegetation. It causes a wide variety of infections. Often animals and pets carry this bacterium with no evidence of disease. The organism often causes abscesses in rodents and rabbits. The medical concern begins when these abscesses are located in nervous system, liver, or kidneys.⁶

In horses, Pseudomonas aeruginosa causes abortion, corneal and guttural pouch infections; in cattle - mastitis, abortion, and genital infections; in dogs and cats - prostatitis, cystitis, dermatitis, septicemia, ear infection and endocarditis; in sheep - "green wool" and dermatitis; in fowl - septicemia and respiratory infections; in mink - hemorrhagic pneumonia.⁷

Pseudomonas aeruginosa is resistant to some disinfectants, but chlorine-containing disinfectants are affective. With minimal moisture these organisms can survive for long periods on water faucets, utensils, floors, instruments, baths, humidifiers, and medical equipment. Pseudomonas are susceptible to ethylene oxide or heat (boiling for 20 minutes).⁷

Pseudomonas and Plants

Pseudomonas-plant interactions are found everywhere in the plant world. These intereactions fall into two groups: those that are beneficial and those that are harmful to the host plants. Beneficial Pseudomonas play a vital role in maintaining soil quality and plant yield due to a specific ability of some strains to colonize the plant rhizosphere at high densities. They produce secondary metabolites with strong antifungal activities, solubilize phosphates and degrade toxic contaminants (P. putida).⁸

References:
1. Pseudomonas: genomics and molecular biology By Pierre Cornelis
2. Pseudomonas: model organism, pathogen, cell factory By Bernd Rehm
3. VisualDx: Essential Adult Dermatology By Noah Craft, Lindy P Fox, Lowell A Goldsmith
4. Ocular infection By David Seal, Uwe Pleyer
5. Microterrors by Tony Hart.
6. Exotic Small Mammal Care and Husbandry By Ron E. Banks, Julie Sharp, Sonia Doss, Deborah Vanderford
7. Essentials of veterinary bacteriology and mycology By Gordon R. Carter, Darla J. Wise
8. Pseudomonas: model organism, pathogen, cell factory By Bernd Rehm