Burkholderia cepacia complex (BCC)

 Burkholderia cepacia (aka Pseudomonas cepacia) is a Gram-negative, aerobic, non-fermenting bacillus that is clinically important as an opportunistic pathogen, particularly in patients with cystic fibrosis (CF) and chronic granulomatous disease (CGD). It is also a phytopathogen and causes rots in allium bulbs especially stored onions (Burkholder, 1950).

The lipase in particular which is extracellular has industrial applications in biodiesel production and detergents because it is highly thermostable and generally resistant to chemical damage.

Pseudomonas cepacia is the former name of an organism now classified within the Burkholderia cepacia complex (BCC).

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1. Taxonomy and Nomenclature

• Former name: Pseudomonas cepacia

• Current classification: Burkholderia cepacia complex (BCC)

• Family: Burkholderiaceae

• Genus: Burkholderia

The Burkholderia cepacia complex comprises multiple genetically distinct but phenotypically similar species, including B. cenocepacia, B. multivorans, and others. These species vary in virulence and clinical outcomes.

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2. Microbiological Characteristics

• Gram stain: Gram-negative rods

• Oxygen requirement: Strictly aerobic

• Motility: Motile (polar flagella)

• Spores: Non-spore forming

• Capsule: Variable; contributes to virulence

• Metabolism:

  • Non-lactose fermenter

  • Oxidase positive

  • Catalase positive

Growth Characteristics

• Grows on ordinary laboratory media

• On MacConkey agar: Non-lactose-fermenting colonies

• Selective media (e.g., BCSA – Burkholderia cepacia selective agar) used in CF labs

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3. Environmental Reservoirs

Burkholderia cepacia is widely distributed in nature:

• Soil and water

• Plants (notably onions—hence “cepacia”). It was originally identified by Burkholder as the cause of onion rot in stored bulbs.

• Hospital environments:

  • Disinfectants

  • Intravenous fluids

  • Nebulizer solutions

  • Medical devices

Its ability to survive in nutrient-poor and antiseptic environments makes it a significant nosocomial pathogen.

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4. Virulence Factors

Key virulence mechanisms include:

• Lipopolysaccharide (LPS): Induces inflammation and endotoxin effects

• Biofilm formation: Promotes persistence and antibiotic resistance

• Proteases and lipases: Tissue damage. 

• Quorum sensing systems: Regulate virulence gene expression

• Intrinsic antibiotic resistance mechanisms: Efflux pumps, β-lactamases

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5. Clinical Significance

A. Cystic Fibrosis (CF)

Burkholderia cepacia is a major pathogen in CF patients:

• Colonizes the respiratory tract

• Associated with:

  • Accelerated decline in lung function

  • Increased hospitalization

  • Poor post-lung transplant outcomes

Cepacia Syndrome

A severe, often fatal complication characterized by:

• Necrotizing pneumonia

• Bacteremia

• Sepsis

• Rapid respiratory failure

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B. Chronic Granulomatous Disease (CGD)

• Causes severe infections due to defective NADPH oxidase

• One of the catalase-positive organisms classically associated with CGD

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C. Other Opportunistic Infections

Primarily in immunocompromised or hospitalized patients:

• Pneumonia

• Bacteremia

• Urinary tract infections

• Wound and burn infections

• Septic arthritis (rare)

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6. Laboratory Diagnosis

Specimen Types

• Sputum (especially in CF patients)

• Blood cultures

• Wound swabs

• Urine

Identification

• Culture with biochemical testing

• Non-fermenting Gram-negative bacillus

• Confirmed by:

  • Molecular methods (PCR, MALDI-TOF)

  • Selective media in CF settings

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7. Antibiotic Resistance

A defining feature of Burkholderia cepacia is marked intrinsic and acquired antibiotic resistance.

Commonly Resistant To:

• Aminoglycosides

• First- and second-generation cephalosporins

• Polymyxins (including colistin)

• Many β-lactams

Potentially Effective Agents (variable susceptibility):

• Trimethoprim–sulfamethoxazole (drug of choice)

• Ceftazidime

• Meropenem

• Minocycline

• Fluoroquinolones

Susceptibility testing is essential, as resistance patterns vary widely.

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8. Infection Control and Epidemiology

• Highly transmissible between CF patients

• Spread via:

  • Direct contact

  • Respiratory droplets

  • Contaminated equipment

Infection Control Measures:

• Strict hand hygiene

• Patient segregation in CF clinics

• Equipment sterilization

• Surveillance cultures

Because of its impact on outcomes, colonization with B. cepacia may exclude CF patients from lung transplantation programs.

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9. Differentiation from Pseudomonas aeruginosa

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10. Key Exam and Clinical Points

• Formerly called Pseudomonas cepacia

• Now part of Burkholderia cepacia complex

• Non-fermenting, aerobic, Gram-negative rod

• Important pathogen in cystic fibrosis and CGD

• Causes cepacia syndrome

• Notoriously multidrug resistant

• Can survive in disinfectants and hospital solutions

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Biotechnology Applications

Lipase: The lipase is thermostable which makes it an interesting protein for biotechnology. The lipase has been explored from an industrial perspective (Bornscheuer et al., 1994) in an immobilised form (Pencreac’h et al. 2000). It has potential in biodiesel production and has been used to produce a fuel from soybean oil (Noureddini et al., 2005).

Summary

Pseudomonas cepacia (now Burkholderia cepacia complex) is an environmentally resilient, opportunistic Gram-negative pathogen with particular importance in cystic fibrosis and immunocompromised patients. Its high intrinsic antibiotic resistance, ability to persist in hospital environments, and association with severe respiratory disease make it a significant clinical and infection-control challenge.

References

Pencreac’h, G., Leullier, M., & Baratti, J. C. (1997). Properties of free and immobilized lipase from Pseudomonas cepacia. Biotechnology and Bioengineering, 56(2), pp.181-189