What is the appropriate treatment for suspected melioidosis due to VITEK (VITEK, a microbial identification system) misidentification of Burkholderia pseudomallei?

Treatment of Suspected Melioidosis Due to VITEK Misidentification of Burkholderia pseudomallei

For suspected melioidosis due to VITEK misidentification of Burkholderia pseudomallei, treatment should begin immediately with intravenous meropenem or imipenem for at least 14 days, followed by oral trimethoprim-sulfamethoxazole for 3-6 months. 1, 2

Understanding the Problem of Misidentification

• VITEK 2 and other commercial identification systems frequently misidentify B. pseudomallei as Burkholderia cepacia complex or other related species, with accuracy rates as low as 87% for B. pseudomallei identification 3
• Biochemical features of B. pseudomallei strains can affect correct identification, with certain combinations of test results leading to misidentification as B. cepacia complex 4
• Confirmation of suspected B. pseudomallei should be performed using more reliable methods such as latex agglutination tests, PCR for type III secretion system gene clusters, or 16S rRNA sequencing 5, 6

Initial Intensive Phase Treatment

First-line Options:

• Carbapenems (preferred for severe cases) 1, 2

  • Meropenem or imipenem for at least 14 days 7, 1
  • Demonstrated better clinical outcomes than ceftazidime in severe melioidosis cases 1, 2
  • All clinical B. pseudomallei isolates show consistent susceptibility to carbapenems 1

• Alternative: Ceftazidime 7, 2

  • 100 mg/kg/day for at least 14 days 8
  • May be used if carbapenems are not available 2

Extended Treatment Considerations:

• Longer intensive treatment is required for 1, 2:
  • Critical illness
  • Extensive pulmonary disease
  • Deep-seated collections or organ abscesses
  • Osteomyelitis
  • Septic arthritis
  • Neurologic melioidosis

Eradication Phase Treatment

• Trimethoprim-sulfamethoxazole (TMP-SMX) 2, 8

  • Standard dosing: Double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) twice daily 2
  • Duration: 3-6 months 2, 8
  • TMP-SMX monotherapy for 20 weeks has been shown to be as effective as combination therapy 8

• Alternatives if TMP-SMX is not tolerated or contraindicated 2, 8:

  • Amoxicillin-clavulanate
  • Doxycycline

Special Considerations

• B. pseudomallei is inherently resistant to many antibiotics, including penicillin, ampicillin, first- and second-generation cephalosporins, gentamicin, streptomycin, and polymyxin 1, 8
• Selective culture media (such as Ashdown's agar) significantly increases the yield of B. pseudomallei from clinical specimens and is highly cost-effective in endemic areas 9
• When treating suspected melioidosis based on VITEK identification, continue treatment until confirmation by more reliable methods, as delays in appropriate therapy can lead to poor outcomes 7, 6

Clinical Pearls and Pitfalls

• Common pitfall: Relying solely on automated identification systems like VITEK 2 for definitive identification of B. pseudomallei 3, 6
• Important caveat: Patients from Southeast Asia with respiratory symptoms and upper zone infiltrates on chest X-rays should be investigated for melioidosis 7
• Clinical pearl: Consider melioidosis in patients with risk factors (travel to endemic areas, exposure to soil or water in tropical regions) even if initial identification suggests a different Burkholderia species 7
• Treatment pitfall: Avoid empiric treatment with antibiotics that B. pseudomallei is inherently resistant to, such as aminoglycosides or polymyxins 1, 8