Pseudomonas aeruginosa, a Bacterium that grows in soil, marshes, and Attacks People with cystic fibrosis , burn victims, individuals with cancer

PSEUDOMONAS

Pseudomonas aeruginosa is a versatile Gram-negative bacterium that grows in soil, marshes, and coastal marine habitats, as well as on plant and animal tissues. People with cystic fibrosis , burn victims, individuals with cancer, and patients requiring extensive stays in intensive care units are particularly at risk of disease resulting from P. aeruginosa infection. It is noted for its environmental versatility, ability to cause disease in particular susceptible individuals, and its resistance to antibiotics.

The most serious complication of cystic fibrosis is respiratory tract infection by the ubiquitous bacterium Pseudomonas aeruginosa . Cancer and burn patients also commonly suffer serious infections by this organism, as do certain other individuals with immune systems deficiencies. Unlike many environmental bacteria, P. aeruginosa has a remarkable capacity to cause disease in susceptible hosts. It has the ability to adapt to and thrive in many ecological niches, from water and soil to plant and animal tissues. The bacterium is capable of utilizing a wide range of organic compounds as food sources, thus giving it an exceptional ability to colonize ecological niches where nutrients are limited. P. aeruginosa can produce a number of toxic proteins which not only cause extensive tissue damage, but also interfere with the human immune system's defense mechanisms. These proteins range from potent toxins that enter and kill host cells at or near the site of colonization to degradative enzymes that permanently disrupt the cell membranes and connective tissues in various organs. This bacterium is also noted for its resistance to many antibiotics.

Members of this genus are classified into five groups based on ribosomal RNA homology. These bacteria are clinically important because they are resistant to most antibiotics and they are capable of surviving in conditions that few other organisms can tolerate. They also produce a slime layer that is resistant to phagocytosis. Pseudomonas is often encountered in hospital and clinical work because it is a major cause of hospital acquired (nosocomial) infections. Its main targets are immunocompromised individuals, burn victims, and individuals on respirators or with indwelling catheters. Additionally, these pathogens colonize the lungs of cystic fibrosis patients, increasing the mortality rate of individuals with the disease. Infection can occur at many sites and can lead to urinary tract infections, sepsis, pneumonia, pharyngitis, and a lot of other problems. Rarely will you find Pseudomonas as a cause of infection in healthy individuals. Its non-invasive nature limits its pathogenic capabilities.

P. aeruginosa

Pseudomonas aeruginosa is the most frequently isolated non-fermenter in the laboratory. It has several features that distinguish it from other species of Pseudomonas :

It can grow at 42 degrees celsius
Produces a bluish pigment (pyocyanin) and a greenish pigment
Characteristic fruity odor

The basis of this organisms pathogenicity involves several toxins and chemicals which the bacterium secretes upon infection. The lipopolysaccharide layer helps the cell adhere to host tissues and prevents leukocytes from ingesting and lysing the organism. Lipases and exotoxins then procede to destroy host cell tissue which then leads to the complications associated with infection. P. aeruginosa prefers to inhabit moist environments but it can survive in a medium as deficient as distilled water. It will also grow on just about any laboratory medium and is beta-hemolytic on blood agar. Treatment of Pseudomonas infection consists of a combination of two antibiotics: for example an anti-pseudomonal penicillin and an aminoglycoside. The best way to reduce the spread of P. aeruginosa in the hospital is to use good aseptic technique on hospital instruments and when in contact with patients.

(under the microscope)

LABORATORY INDICATIONS:

	Oxidase +
	Beta-hemolytic
	Characteristic odor and color
	Motile

OTHER SPECIES

Pseudomonas cepacia is an opportunistic pathogen of cystic fibrosis patients. It also shows substantially greater antibiotic resistance than its relative, P. aeruginosa . However, P. cepacia can be distinguished from other Pseudomonas species because it is lysine positive.

Although not of the same genus, Stenotrophomonas maltophila (formerly known as Xanthomonas maltophila ) is very similar to the Pseudomonads. This motile bacterium is a cause of nosocomal infections in immunocompromised patients. S. maltophila also harbors significant resistance to many antibiotics considered effective for treating Pseudomonas infections. However, most strains of the bacterium are susceptible to trimethoprim or sulfamethoxazole. S. maltophila can also be distinguished from Pseudomonas species by the lysine and DNAse tests for which it is positive.

Pseudomonas infection: Patient questions

I am taking a particular drug(s) to treat Pseudomonas infection and its not working. Do you have any suggestions for a better treatment?
We are not physicians, we are research scientists, and so I'm afraid we cannot provide you with any advice regarding treatment. Unfortunately, Pseudomonas infection can be difficult to treat in some instances; however we are working to provide new drugs or other therapies to prevent or cure infection. We recommend you bring up any concerns you have with your doctor. Seek a second medical opinion if you feel strongly that you are being treated incorrectly.

Do you have any drugs you've recently developed that can help cure Pseudomonas infection, but aren't available to the public yet? I'd be willing to be involved in a clinical trial or try out the drug ahead of time, as I am desperate for a cure.
It is unethical for us to allow persons access to any developing medicines before they have first undergone safety tests. There may be clinical trials going on that you may be eligible to participate in; however you will have to contact the relevant agency in your respective country to find out more information. We are not a good starting point for such inquiries - your local or national health department/office is likely more suitable. Note that some clinical trials are publicized through Cystic Fibrosis Agencies (due to the susceptibility Cystic Fibrosis patients have for Pseudomonas infection), so you may wish to contact the agency nearest you for more information as well (for example, see the U.S. Cystic Fibrosis Foundation's site at http://www.cff.org/clinical.htm) .

I (or my relative) have a Pseudomonas infection I can't get rid of! Where do I go to for help?
We assume you have already seen your doctor about this, who will likely be prescribing you a treatment. Please follow this treatment carefully, remembering, for example, to always complete all antibiotic pills during a particular treatment (or as prescribed). As we are research scientists, not physicians, we cannot help you with regard to any treatment or giving you medical advice. For such information you are best off seeing a qualified doctor face to face.

Is a person with a Pseudomonas infection at high risk of transmitting their infection to another healthy individual?
No. Pseudomonas infections occur in individuals who have a particular susceptibility to this bacterium - a susceptibility that is not common to most people. The vast majority of people who come in contact with Pseudomonas will not become infected. If you are a healthy individual with no burns, cystic fibrosis disease, or other condition that may compromise your immune system, you should not fear coming into contact with a person who has a Pseudomonas infection. If you have a child (for example) who has a Pseudomonas infection you should not be worried that your child may pass the infection on to other healthy people who have none of the risk factors mentioned above. Also you do not have to worry that you, if a healthy individual, may be the source/cause of a Pseudomonas infection in someone who is infected.

How easily are Pseudomonas infections transmitted? Is it possible for me, as a caregiver, to be the source of this infection that my loved one keeps getting over and over again?
Healthy people do not carry a Pseudomonas infection. The person who became infected with Pseudomonas did not get this from a healthy individual so you do not have to worry that you, as a healthy caregiver, are the cause or source of their Pseudomonas infection.

Where can I find more information about Pseudomonas aeruginosa and the disease it causes?
A good microbiology textbook from your local library or University library will contain some basic information about this bacterium. See your librarian for help. For more detailed information, or information on the latest research, you may wish to do a search of "PubMed" a database of recent medical research papers. You can search PubMed at its website at http://www.ncbi.nlm.nih.gov/entrez using words such as " Pseudomonas aeruginosa ", and perhaps clicking on the "Limits" button to only view recent reviews. Note that such detailed information does require a certain level of background knowledge about microbiology and genetics, and so you must be careful, if you do not have such training, to ensure that you do not misinterpret findings. We recommend that you review any such research information with someone who has background training, or is a physician, to ensure that you are interpreting the research results correctly. You may also wish to contact your local Cystic Fibrosis Foundation office for more information. Cystic Fibrosis patients are particularly susceptible to P. aeruginosa and so such agencies may have additional information that is helpful to you.