Infectious Disease and Microbiology – Burkholderia Species

Overview

Burkholderia species are aerobic Gram-negative bacilli that can cause opportunistic and healthcare-associated infections. Among the most clinically important organisms are members of the Burkholderia cepacia complex, particularly because of their association with chronic respiratory infection in patients with cystic fibrosis.

Other clinically relevant species include Burkholderia gladioli and organisms historically referred to as B. pickettii.

Important Species

The B. cepacia complex contains several closely related species, including:

• B. cenocepacia

• B. multivorans

• B. dolosa

• B. cepacia

• Several additional species

B. gladioli can also produce respiratory and opportunistic infections.

The organism formerly called Burkholderia pickettii is now generally classified as Ralstonia pickettii.

Microbiology

These organisms are aerobic, nonfermenting Gram-negative bacilli. They are environmentally hardy and can survive under conditions that inhibit many other bacteria.

An important clinical characteristic of the B. cepacia complex is its substantial intrinsic antimicrobial resistance, which can make treatment difficult.

Epidemiology

Burkholderia organisms are widely distributed in the environment, particularly in soil and water.

The B. cepacia complex has special importance in patients with cystic fibrosis (CF). Certain strains can spread from one patient to another, making infection-control measures particularly important in CF clinics and other settings where patients with cystic fibrosis interact.

Healthcare-associated transmission can also occur through contaminated medical products, solutions, or equipment.

Respiratory Infection in Cystic Fibrosis

The B. cepacia complex is best known for causing persistent respiratory colonization and infection in patients with cystic fibrosis.

Clinical manifestations range from relatively stable chronic airway colonization to:

• Bronchitis

• Recurrent pulmonary exacerbations

• Progressive decline in pulmonary function

• Pneumonia

• Bacteremia and sepsis

B. gladioli can produce a similar respiratory infection in susceptible patients.

Cepacia Syndrome

A particularly severe manifestation is sometimes called cepacia syndrome.

This is characterized by rapid clinical deterioration with:

• High fever

• Severe necrotizing pneumonia

• Respiratory failure

• Bacteremia

• Sepsis

The syndrome is especially associated with certain members of the B. cepacia complex and can be life-threatening.

Other Infections

Outside cystic fibrosis, Burkholderia species may cause opportunistic infections such as:

• Wound infections

• Catheter-associated infections

• Bacteremia

• Sepsis

These infections occur particularly in immunocompromised or severely ill hospitalized patients.

Contaminated Medical Products

Organisms historically identified as B. pickettii, now generally classified as Ralstonia pickettii, have been associated with outbreaks of bloodstream infection resulting from contaminated intravenous fluids or other medical products.

Their ability to persist in aqueous environments contributes to their importance in healthcare-associated outbreaks.

Diagnosis

Diagnosis is established primarily through culture of appropriate clinical specimens.

Depending on the clinical syndrome, specimens may include:

• Sputum or other respiratory secretions

• Blood

• Wound material

• Catheter-related specimens

Accurate species identification is particularly important in patients with cystic fibrosis because different members of the B. cepacia complex may differ in epidemiology, transmissibility, resistance, and clinical significance.

Treatment

Treatment can be challenging because B. cepacia complex organisms frequently demonstrate multidrug resistance.

Antimicrobial susceptibility testing should therefore guide definitive treatment whenever possible.

Potentially active agents include:

Ceftazidime

Cefepime

Meropenem

Imipenem

Piperacillin-tazobactam

Ciprofloxacin

Trimethoprim-sulfamethoxazole

Susceptibility varies substantially among isolates.

Combination Therapy

For severe infection, particularly pneumonia, bacteremia, or rapidly progressive disease, combination antimicrobial therapy may be considered based on susceptibility results and specialist guidance.

Isolates recovered from patients with cystic fibrosis may have higher minimum inhibitory concentrations and greater resistance than environmental strains, making individualized susceptibility testing particularly important.

Aminoglycosides

Although aminoglycosides have historically been considered among possible treatment options, members of the B. cepacia complex commonly demonstrate substantial intrinsic resistance. They should therefore not be assumed to be active without susceptibility evidence.

Inhaled Antimicrobial Therapy

In selected patients with chronic pulmonary infection, particularly those with cystic fibrosis, inhaled antimicrobial therapy may sometimes be incorporated into a broader treatment strategy.

Nebulized agents such as tobramycin or meropenem have been studied or used in selected circumstances, although effectiveness depends heavily on the infecting species and its susceptibility pattern.

Prevention

Preventing transmission is especially important in the cystic fibrosis population.

Patients with CF who are not colonized with the B. cepacia complex should avoid close contact with individuals known to be infected or colonized.

Healthcare facilities caring for patients with cystic fibrosis use strict infection-prevention practices and patient segregation measures to reduce person-to-person transmission.

Appropriate handling and quality control of intravenous solutions, medications, and medical equipment are also important for preventing healthcare-associated outbreaks.

High-Yield Clinical Pattern

A patient with cystic fibrosis who develops chronic or rapidly worsening pulmonary infection with a multidrug-resistant Gram-negative nonfermenting bacillus should raise suspicion for the Burkholderia cepacia complex.

Rapid deterioration accompanied by necrotizing pneumonia, bacteremia, and sepsis suggests the severe form known as cepacia syndrome.

Exam Essentials

Genus: Burkholderia

Microbiology: Aerobic, nonfermenting Gram-negative bacilli

Important group: B. cepacia complex

Important species: B. cenocepacia, B. multivorans, B. dolosa, B. cepacia, and B. gladioli

Major association: Cystic fibrosis

Major infection: Chronic respiratory infection and pneumonia

Severe manifestation: Cepacia syndrome

Other infections: Wound infection, catheter-associated bacteremia, and sepsis

Diagnosis: Culture with accurate species identification and susceptibility testing

Treatment: Individualized according to antimicrobial susceptibility; potentially active drugs include TMP-SMX, ceftazidime, meropenem, and other selected agents

Major treatment problem: Multidrug resistance

Prevention: Strict infection-control measures and avoidance of transmission between patients with cystic fibrosis

Important classification pearl: B. pickettii is an older designation; the organism is now generally known as Ralstonia pickettii.