Why did the Centers for Disease Control and Prevention recently send an alert about Burkholderia pseudomallei?

A: The Centers for Disease Control and Prevention (CDC) found the same strain of Burkholderia pseudomallei (B. pseudomallei) infecting two patients and in soil and water in and around these patients’ homes in the coastal regions of Mississippi. There was no evidence of a common exposure for these patients. Altogether, this firmly establishes that B. pseudomallei is present in soil and fresh water along the U.S. Gulf Coast. CDC considers this finding an urgent public health incident, as sepsis due to B. pseudomallei has a mortality rate as high as 50%, particularly in individuals who have diabetes.

What is the epidemiology of B. pseudomallei infections?

Infections with B. pseudomallei are rare in the U.S. When they did occur in the past, those infected either obtained the infection while traveling in Northern Australia or Southeast/South Asia or from exposure to contaminated products imported from those regions.

Most patients are exposed to contaminated soil or water, typically through mucous membranes, breaks in the skin, or occasionally ingestion of contaminated food or water. This can result in disseminated infection leading to sepsis. The patient populations most likely to be infected are diabetics, people who abuse alcohol, and immunocompromised individuals. Thankfully, person-to-person spread of B. pseudomallei is unlikely. However, there is no vaccine for this organism either. Preventing exposure to contaminated water or soil by wearing gloves when working with soil and wearing rainboots in flooded areas is essential for at-risk individuals.

How can clinical laboratories diagnose infections with this organism?

B. pseudomallei is an environmental Gram-negative bacilli that can be readily cultured from any number of clinical specimens. Properly identifying it may be challenging, however, because matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and other widely used automated microbial identification systems can misidentify B. pseudomallei. Delays in or misidentification of this organism may in turn result in inappropriate antimicrobial therapy contributing to the high mortality rate associated with it. Clinical laboratories should therefore familiarize themselves with the Laboratory Response Network (LRN)-sentinel laboratory protocol for B. pseudomallei, which describes a simple laboratory test algorithm to rule out the presence of this organism.

What steps are laboratorians required to take if they detect this organism in a clinical specimen?

By statute, the laboratory is required to report the potential isolation of B. pseudomallei to local or state public health authorities because it is a tier 1 biothreat organism. Laboratorians must secure the organism, handle it in a biosafety cabinet, and avoid processes that might create an aerosol of the bacterium. In addition, the lab must submit the organism to a LRN reference laboratory for confirmatory identification. Within 7 days of identification, the laboratory must then document destruction of the organism and specimen from which it was isolated either by autoclaving or incineration.

How serious a threat is B. pseudomallei to the U.S. population?

The evidence that two people acquired B. pseudomallei from the environment in the continental United States heralds its endemicity here. Its emergence may reflect climactic changes creating tropical conditions—an ecological niche where this organism thrives. As mentioned above, person-to-person spread of this organism is rare, so a COVID-19 or monkeypox type event is not in the offing. However, this is still an organism of concern, particularly given the high mortality rate it leads to in diabetic patients, coupled with the increasing incidence of diabetes in the Gulf Coast region, where tropical conditions are present and more severe storm events leading to flooding are anticipated.

Peter H. Gilligan, PhD, D(ABMM), F(AAM), is the retired director of the clinical microbiology and immunology laboratories at the University of North Carolina Hospitals in Chapel Hill and co-author of the LRN sentinel laboratory protocol for Burkholderia. +Email: [email protected]