Burkholderia Cepacia

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MICROBIOLOGY LEGEND

CYCLE 28 – ORGANISM 6

Burkholderia cepacia

Burkholderia cepacia (B. cepacia) is a gram-negative rod that is 1.6-3.2 µm in length and was formerly classified as Pseudomonas. It was discovered in 1949 by Walter Burkholder at Cornell University in rotting onions. B. cepacia is a strict aerobe and a chemo-organotroph with an optimum temperature of 30 to 35⁰C. It is found in soil, water and on plants and can survive longer in wet environments then in dry ones. It is unique in the way that is can be versatile in its uses - plant pathogen, human pathogen, bioremediation agent, and a bio- control agent.

It can be used as a bio-control agent because it produces multiple antibiotics against pathogenic fungi in plants. It is not a toxic fungicide, so it does not pollute the water or soil. B. cepacia has the ability to metabolize almost anything available to it, even chlorinated hydrocarbons. These hydrocarbons are commonly found in commercial pesticides and herbicides. It is possible to add this bacterium to sites that are contaminated by these toxins and clean up the environment. Weed-B-Gone, a common household herbicide, is popular because it does its job and is easily degradable by organisms in the soil. B. cepacia is one of the most effective bacteria at degrading the chemicals.

Unfortunately, the bacterium has problems that need to be handled before widespread usage. One is that is can resist multiple antibiotics and has been found able to grow on penicillin medium. It can mutate quickly and adapt due to its unusually large genome to defend against antibiotics.

Based on phenotypic and genotypic analyses, B cepacia is divided into 9 genomovars that constitute the Burkholderia cepacia complex (BCC). This group of catalase-producing, non-lactose-fermenting bacteria is composed of nine different species, including B. cepacia, B. multivorans, B. cenocepacia, B. vietnamiensis, B. stabilis, B. ambifaria, B. dolosa, B. anthina, and B. pyrrocinia.

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Pathophysiology B cepacia is an organism of low virulence and rarely causes infection in healthy hosts. It is almost always a colonizing bacterium rather than an infecting bacterium, but it is especially important when isolated from body fluids that are ordinarily sterile. The pathophysiology of B. cepacia infection mirrors that of other non-fermentative aerobic bacilli. B. cepacia is generally not a pathogen in the ambulatory setting, but it may colonize and/or infect the respiratory tract of patients with cystic fibrosis. B. cepacia may also cause catheter-related infections in patients with cancer and in those on haemodialysis. B. cepacia nosocomial pneumonia has also been reported, especially in patients who have been treated with fluoroquinolones and ceftazidime antibiotics. Skin and soft-tissue infections, surgical-wound infections, and genitourinary tract infections with B. cepacia have also been reported. B cepacia survives and multiplies in aqueous hospital environments, where it may persist for long periods. Sources of B. cepacia colonization include the following:  Personnel - hands, antiseptic soaps, hand lotion  Respiratory equipment and/or fluids - respirator tubing condensate, ultrasonic nebulizers, inhalation medications  Intravenous lines and/or fluids - intravenous solutions, central venous catheters  Pressure-monitoring devices - pressure transducer fluids  Urine and/or fluids - indwelling Foley catheters, urometers, irrigation solutions

Diagnosis Diagnosis of BCC involves culturing the bacteria from clinical specimens such as sputum or blood. BCC organisms are naturally resistant to many common antibiotics including aminoglycosides and polymyxin. Oxidation-fermentation polymyxin-bacitracin-lactose (OFPBL) agar contains polymyxin (which kills most gram- negative bacteria, including Pseudomonas aeruginosa) and bacitracin (which kills most gram-positive bacteria and Neisseria species). It also contains lactose, and organisms such as BCC that ferment lactose turn the pH indicator yellow, which helps to distinguish it from other organisms that may grow on OFPBL agar, such as Candida species, Pseudomonas fluorescens, Stenotrophomonas species, and Proteus species.

B. cepacia grows as tiny pinpoints on McConkey agar in At 48 hours; B. cepacia displays small non-lactose fermenting 24 hours at 37⁰C. colonies. Some strains appear somewhat purple due to strong lactose oxidation

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Mortality/Morbidity If an intravenous infusate contains high numbers of B. cepacia, direct injection into the bloodstream may induce the signs and symptoms associated with gram-negative bacteraemia. Gram-negative bacteraemia may occur if urologic irrigation fluids that contain B. cepacia are used during an invasive urologic procedure.

Treatment Treatment typically includes multiple antibiotics and may include ceftazidime, doxycycline, piperacillin, meropenem, chloramphenicol and co-trimoxazole (trimethoprim/sulfamethoxazole). Although co-trimoxazole has been generally considered the drug of choice for B. cepacia infections, ceftazidime, doxycycline, piperacillin and meropenem are considered to be viable alternative options in cases where co-trimoxazole cannot be administered because of hypersensitivity reactions, intolerance or resistance.

References 1. Author: Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital 2. Chiarini et. al.(2006). Trends Microbiol. Jun;14(6):277-86 3. Bergey's Manual of Systematic Bacteriology", Vol. 2, Williams and Wilkins, 1989.

Questions 1. Discuss the pathophysiology of B. cepacia. 2. How would you diagnose a case of B. cepacia in your lab? 3. What antibiotics can be used to treat a patient diagnosed with a B. cepacia infection?

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