Airborne Transmission of Melioidosis to Humans from Environmental Aerosols Contaminated with B. pseudomallei

Abstract

Melioidosis results from an infection with the soil-borne pathogen Burkholderia pseudomallei, and cases of melioidosis usually cluster after rains or a typhoon. In an endemic area of Taiwan, B. pseudomallei is primarily geographically distributed in cropped fields in the northwest of this area, whereas melioidosis cases are distributed in a densely populated district in the southeast. We hypothesized that contaminated cropped fields generated aerosols contaminated with B. pseudomallei, which were carried by a northwesterly wind to the densely populated southeastern district. We collected soil and aerosol samples from a 72 km2 area of land, including the melioidosis-clustered area and its surroundings. Aerosols that contained B. pseudomallei-specific TTSS (type III secretion system) ORF2 DNA were well distributed in the endemic area but were rare in the surrounding areas during the rainy season. The concentration of this specific DNA in aerosols was positively correlated with the incidence of melioidosis and the appearance of a northwesterly wind. Moreover, the isolation rate in the superficial layers of the contaminated cropped field in the northwest was correlated with PCR positivity for aerosols collected from the southeast over a 2-year period. According to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) analyses, PFGE Type Ia (ST58) was the predominant pattern linking the molecular association among soil, aerosol and human isolates. Thus, the airborne transmission of melioidosis moves from the contaminated soil to aerosols and/or to humans in this endemic area.

Predicted global distribution of Burkholderia pseudomallei and burden of melioidosis

“…Skin inoculation is considered the main route of infection in agricultural workers in developing countries 14 . Recent evidence also suggests that inhalation of B. pseudomallei during extreme weather events 15,16 and ingestion of B. pseudomallei contaminated water are also important routes of infection 17 . High-risk groups include patients with diabetes mellitus, chronic kidney disease and excessive alcohol intake 12,18 .…”

Melioidosis: A Neglected Cause of Community-Acquired Pneumonia

“…Recent work in Taiwan has shown that northwesterly winds during typhoon season were associated with melioidosis incidence and detection of B. pseudomallei-specific DNA in aerosols. 30 Water appears to serve as a vehicle to spread B. pseudomallei contamination. Interestingly, a study from Laos also noted an association between humidity and pediatric melioidosis cases, although the reasons for this are yet unclear.…”

Multilocus Sequence Typing of Clinical Isolates of Burkholderia pseudomallei Collected in Hainan, a Tropical Island of Southern China

“…Burkholderia pseudomallei infection may be acquired through inhalation, subcutaneous inoculation, or direct exposure of wounded skin to contaminated material. [10][11][12][13] Clinical presentations of melioidosis are highly variable, and can manifest as asymptomatic infection, localized skin abscesses, acute or chronic pneumonia, genitourinary, bone, and joint infections, or severe systemic sepsis with or without multiple abscesses in internal organs. Septic shock cases have a greater than 90% mortality rate.…”