What is the treatment for a gram-negative, lactose-negative rod that propels itself through actin polymerization?

Treatment of Burkholderia pseudomallei Infection (Melioidosis)

Ceftazidime, imipenem, or meropenem are the recommended first-line treatments for Burkholderia pseudomallei infection, which propels itself through actin polymerization. 1

Pathogen Identification

Burkholderia pseudomallei is a gram-negative, lactose-negative rod that:

• Uses actin polymerization (via the BimA protein) for intracellular motility 2, 3, 4
• Causes melioidosis, a potentially fatal infection
• Is intrinsically resistant to many antibiotics due to efflux pumps and reduced outer membrane permeability 2
• Can cause various clinical presentations including pneumonia, abscesses, and disseminated infection 5

Treatment Recommendations

Intensive Phase (10-14 days)

For severe infections:

• First choice: Meropenem 1g IV every 8 hours 6, 7
• Alternatives:
  • Imipenem 500mg IV every 6 hours 1
  • Ceftazidime 2g IV every 8 hours 1, 6

Eradication Phase (3-6 months)

After clinical improvement:

• First choice: Trimethoprim-sulfamethoxazole (TMP-SMZ) 160-800mg orally twice daily 1
• Alternative: Doxycycline 100mg orally twice daily 1

Treatment Considerations

1. Severity assessment:

   • For severe infections (septic shock, deep organ abscesses): Use IV carbapenems
   • For localized, mild infections: Consider oral therapy after initial IV treatment

2. Duration of therapy:

   • Intensive phase: 10-14 days of IV therapy
   • Eradication phase: 3-6 months of oral therapy to prevent relapse

3. Combination therapy:

   • Consider adding TMP-SMZ during intensive phase for severe infections
   • For treatment of multidrug-resistant strains, combination therapy may be beneficial 6

4. Source control:

   • Drainage of abscesses is critical for treatment success 6
   • Surgical debridement may be necessary for extensive tissue involvement

Special Considerations

1. Antibiotic resistance:

   • B. pseudomallei is intrinsically resistant to many antibiotics including:
     • First and second-generation cephalosporins
     • Macrolides
     • Aminoglycosides
     • Many penicillins

2. Monitoring:

   • Follow clinical response (fever resolution, hemodynamic stability)
   • Monitor inflammatory markers (CRP, procalcitonin)
   • Repeat cultures to confirm clearance in severe cases

3. Common pitfalls:

   • Premature discontinuation of therapy (leads to relapse)
   • Inadequate source control
   • Failure to recognize the organism (often misidentified as Pseudomonas)
   • Insufficient duration of eradication therapy

Treatment Algorithm

1. Confirm diagnosis:

   • Culture from blood, abscess fluid, or tissue
   • Consider molecular testing for rapid identification

2. Initial treatment:

   • Start meropenem 1g IV every 8 hours or ceftazidime 2g IV every 8 hours
   • Ensure source control through drainage or debridement

3. After clinical improvement (usually 10-14 days):

   • Switch to oral TMP-SMZ for 3-6 months
   • Monitor for relapse

4. If treatment failure:

   • Reassess source control
   • Consider combination therapy
   • Evaluate for drug resistance

The treatment of B. pseudomallei infections requires prolonged therapy due to the organism's ability to persist intracellularly and cause relapsing infection. Early recognition and appropriate antimicrobial therapy are essential to reduce mortality and prevent complications.