Microbiology Case Study: A 79 Year Old Male with Rheumatic Heart Disease

Case History

The patient is a 79 y/o male with past medical history of rheumatic heart disease, permanent atrial fibrillation, mechanical aortic and mitral valves (2004), status post single chamber pace maker for bradycardia (2010), and prostate adenocarcinoma treated in 2000. He had new MRI compatible pace maker placed on Oct 19, 2017. During follow-up he was noted to have a hematoma over the incision site. He had a revision done on Nov 3, 2017. At that time, the blood from the incision site was sent for culture. 

Laboratory Identification

Gram stain showed moderate amount of polys with no bacteria seen. The isolate was a gram-negative rod that was identified on the MALDI-ToF as Burkholderia multivorans.

 

burkmult1
Image 1: Semi-mucoid, yellow-grey colonies on Chocolate agar and on Blood agar plates.

Discussion

The Burkholderia genus appears as gram-negative medium-sized straight rods, with the exception being B. mallei which is a coccobacillus. The will grow on blood, chocolate, and MacConkey agar. Oxidative-fermentative-base-polymyxin B-bacitracin-lactose (OFPBL) agar can be used to isolate B. cepacia and Ashdown medium can be used to isolate B. pseudomallei. They are non-lactose fermenters on MacConkey, but B. cepacia can turn into a dark pink to red due to oxidation of lactose after 4-7 days.

B. multivorans is a species within the Burkholderia genus, which are normal to plant, soil, and water, but not normally considered common human flora. Formerly of the Pseudomonas genus, B. cepacia, B. mallei, and B. pseudomallei are the most commonly seen as infections in humans. Further, B. cepacia and B. mallei are not typically human pathogens in a healthy human host. Because of the rarity of this genus to infect humans, their pathogenicity is not well known; but, importantly, they are intrinsically resistant to many antibiotics and can thus be associated with hospital acquired infections.

Of this genus, very little literature is present on B. multivorans specifically, and of the literature that does exist, most of it is in relation to cystic fibrosis patients. Taxonomic advances has shown that B. cepacia complex is a cluster of nine closesly related genomic species or genomorvars (1).  B. multivorans represents genomorvar II. Hospital acquired clinical infections from this complex (but perhaps not specifically from this particular genomorvar) has been seen following catheterization, cystoscopy, heart surgery, and with contaminated ventriculoatrial shunt (2). B. multivorans biochemically is oxidase positive, catalase positive, lipase positive, nitrate-reducing, urease positive, resistant to colistin, and can grow at 42C (3, 4).

A recent comparative genomic study showed that B. multivorans is a highly evolutionarily preserved genome with genomic characteristics from the environment and isolated from cystic fibrosis patients to be similar, and that isolates from different continents are also similar (5). Further, a murine model for pulmonary infections showed that B. multivorans could persist in the host by establishing an intracellular presence within macrophages, which could explain the persistence of this pathogen in cystic fibrosis patients (6). Importantly though, due to the conserved and common genomic structure, there rests a possibility for potential vaccination for cystic fibrosis patients against B. multivorans.

The patient was prescribed a single dose of oral Bactrim and then advised to come into the hospital for admission for IV antibiotics. IV ceftazidime was started with pending blood cultures, which are negative at the time of this documentation.

References:

  1. Coenye T. et al. Taxonomy and identification of the Burkholderia cepacia complex. J Clin Microbiol 2001;39:3427-3436.
  2. Pallent LJ. et al. Pseudomonas cepacia as contaminant and infective age. J Hosp Infect 1983;4:9-13.
  3. Henry DA. et al. Phenotypic methods for determining genomovar status of Burkholderia cepacia complex. J Clin Microbiol 2001;39:1073-1078.
  4. Vandamme P. et al. Occurrence of multiple genomovars of Burkholderia cepacia in patients with cystic fibrosis and proposal of Burkholderia multivorans sp. nov. Int J Syst Bacteriol 1997;47:1188-1200.
  5. Peeters C. et al. Comparative genomics of Burkholderia multivorans, a ubiquitous pathogen with a highly conserved genomic structure. PLoS One. 2017, 21; 12 (4): e0176191.
  6. Chu KK. et al. Persistence of Burkholderia multivorans with the Pulmonary Macrophage in the Murine Lung. Infect Immun 2004; 72 (10): 6142-6147.

 

-Jeff Covington, MD, PhD, is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.

Wojewoda-small

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

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