Locally Acquired Melioidosis Linked to Environment - Mississippi, 2020-2023

Abstract

Melioidosis, caused by Burkholderia pseudomallei, is a rare but potentially fatal bacterial disease endemic to tropical and subtropical regions worldwide. It is typically acquired through contact with contaminated soil or fresh water. Before this investigation, B. pseudomallei was not known to have been isolated from the environment in the continental United States. Here, we report on three patients living in the same Mississippi Gulf Coast county who presented with melioidosis within a 3-year period. They were infected by the same Western Hemisphere B. pseudomallei strain that was discovered in three environmental samples collected from the property of one of the patients. These findings indicate local acquisition of melioidosis from the environment in the Mississippi Gulf Coast region.

Figure 1.. Clinical Course and Investigation Timeline for Patients 1, 2, and 3.

Shown is the timeline of events starting with symptom onset in Patient 1 in July 2020 and progressing to the ongoing Centers for Disease Control and Prevention (CDC) and Mississippi State Department of Health (MSDH) investigation with regard to melioidosis in Patient 3. CT denotes computed tomography, ICU intensive care unit, MPHL Mississippi Public Health Laboratory, MRI magnetic resonance imaging, PCR polymerase chain reaction, and PICC peripherally inserted central catheter.

Figure 2.. Thoracic Imaging in Patients 1, 2, and 3.

In Patient 1, a chest radiograph (Panel A) on hospital day 0 showed multilobar pneumonia and areas of subsegmental atelectasis. In Patient 2, CT without contrast material (Panel B) on hospital day 0 of the first hospitalization showed a 6.5-cm left apical, pleural-based, masslike consolidation with associated bulky hilar and mediastinal lymphadenopathy that aroused concern for necrotizing pneumonia or cancer. (R denotes right, and L denotes left.) In Patient 3, MRI of the thoracic spine (Panel C) showed T7–T8 discitis or osteomyelitis with prevertebral and left epidural abscess resulting in mass effect on the thecal sac and cord (the site from which an abscess swab was obtained for culture and tested positive for B. pseudomallei).

Figure 3.. Whole-Genome Sequencing Analysis.

Panel A shows a phylogenetic tree of all B. pseudomallei genomes included in the National Center for Biotechnology Information (NCBI) RefSeq database (1741 genomes) with the addition of six new isolate genomes from this study (shown as a red node within the dashed red circle). For isolates with known geographic origin, the country was associated with the respective genome, and geographic regions were linked according to definitions listed in The World Factbook (https://www.cia.gov/the-world-factbook) as of December 30, 2022. Scale units denote substitutions per core single-nucleotide polymorphism (SNP) site. Panel B depicts a subpanel phylogeny of refined (recombination sites removed) mutation-only core SNP sites of genomes related to the six isolates from this study (labeled in red), which includes the clinical isolates of the three patients (shown as MS2020a clinical, MS2022a clinical, and MS2023a clinical) and the isolates recovered from the environmental samples (shown as MS2022d W13 water, MS2022g S22 soil, and MS2022j S27 soil). Tree “leaves” list the strain or isolate identifier first, followed by the RefSeq accession in parentheses and geographic information. The notation “ex” in geographic information denotes travel history. Genomes with known geographic data are shown in the colors identical to those used in the large comprehensive panel. Scale units denote mutation-only core SNP substitutions (164,171 sites) per genome alignment site (5,706,452). ClonalFrameML posterior means for R/theta (relative rate of recombination to mutation), 1/delta (inverse mean DNA import length), and nu (mean divergence of imported DNA) were 0.949388, 0.00130988, and 0.00534356, respectively.