Background Also called melioidosis or Whitmore's disease Microbiology Oxidase positive, indole negative Gram-negative bacillus with "safety pin " appearance (i.e. bipolar staining)
Non-hemolytic Colonies start small, smooth, cream-coloured with a metallic sheen, but become dry and wrinkly after 1 to 2 days of incubation
Inherently resistant to polymixins Epidemiology Humans and animals
Important cause of death in south-east Asia and northern Australia
Up to 80% seroprevalence in Thailand, mostly asymptomatic
More cases during the rainy season
Sporadic cases elsewhere, including the Middle East, Africa, and the Americas
May have latent disease with reactivation much later
Acquired by percutaneous inoculation, inhalation (esp. lab workers), and ingestion
Risk factors for clinical disease
Diabetes
Heavy alcohol use
Chronic lung disease
Chronic kidney disease
Treatment with glucocorticoids
Cancer
Thalassemia Clinical Manifestations Incubation period 9 days (range 1 to 21 days)
Presentations can vary from asymptomatic, skin ulcers, abscesses, latent infection, chronic pneumonia (similar to TB), or fulminant shock1 2 Pneumonia (50%)Genitourinary infection (15%)
Skin infection (15%), with ulcers, nodules, or abscesses
Primary bacteremia (10%)
Septic arthritis/OM (3-5%)
Neuro (3-5%)
Disseminated infections can involve liver, spleen, lung, and prostate
About 50% of clinical cases have bacteremia , and 20% of cases will develop septic shock
Can occasionally lay latent and reactivate decades after exposure Prognosis and Complications 50% mortality even with high-quality care Diagnosis Culture
Blood, throat, and urine cultures should be taken from all patients with suspected melioidosis
Grows on blood agar, MacConkey, etc. (i.e. not a fastidious organism)
Can use selective colistin or polymyxin B, since it is inherently resistant
On sheep blood agar, grows as small, smooth, cream-coloured colony with metallic sheen
May develop a dry and wrinkled appearance after 1 to 2 days of incubation
MALDI-ToF may misidentify it as Burkholderia thailandensis , and automated biochemical tests may misidentify it as Chromobacterium violaceum
Other methods
PCR
Immunofluorescence and latex agglutination
Serology (acute/convalescent) Management Intrinsic resistance to many antibiotics, including colistin , primarily using efflux pumps
Treat with induction followed by eradication therapy
Others: amoxicillin-clavulanic acid Prevention Laboratory Safety Biosafety risk group 3 Lab workers can have aerosol exposure if aerosol-generating procedure done outside of a BSC, bite/scratch from infected lab animals, or needlestick/percutaneous exposure
Those at higher risk include: not wearing proper PPE, diabetes , chronic liver disease , chronic kidney disease , alcohol abuse , chronic corticosteroid use, hematologic malignancy , neutropenia or neutrophil dysfunction, chronic lung disease , thalassemia , or other immunosuppression
May need prophylaxis in high-risk patients
Monitor with serology at baseline, weeks 1 2 4 and 6 post-exposure
Needs to be sent to CDC via NML References
^ Bart J. Currie, Linda Ward, Allen C. Cheng. David Joseph Diemert. The Epidemiology and Clinical Spectrum of Melioidosis: 540 Cases from the 20 Year Darwin Prospective Study. PLoS Neglected Tropical Diseases . 2010;4(11):e900. doi :10.1371/journal.pntd.0000900 . ^ E. M. Meumann, A. C. Cheng, L. Ward, B. J. Currie. Clinical Features and Epidemiology of Melioidosis Pneumonia: Results From a 21-Year Study and Review of the Literature. Clinical Infectious Diseases . 2011;54(3):362-369. doi :10.1093/cid/cir808 .
