Judul: Surveillance, Identification, and Characterization of Burkholderia pseudomallei Infection in Macaques and Orangutans.
Abstrak: Burkholderia pseudomallei is a Gram-negative bacterium responsible for causing melioidosis in a wide range of species. It may infect susceptible hosts through cutaneous, ingestion, or inhalation routes. The disease has a moderate to high case fatality rate, and the causative microorganism is categorized as Tier 1 Select Agent by the United States CDC. Concerns regarding melioidosis were raised among nonhuman primate (NHP) researchers in Indonesia, following a fatal melioidosis case in a cynomolgus macaque (Macaca fascicularis) in a primate research center and fatal cases in orangutans. Those incidents were the driving force to conduct surveillance in primate populations. Serosurveillance was conducted on cynomolgus (Macaca fascicularis) and pig-tailed macaques (Macaca nemestrina) in several facilities breeding facilities in West Java and Banten, Indonesia: Jonggol, Darmaga, Lodaya, and Tinjil Island facilities. The serosurveillance was conducted using a panel of enzyme-linked immunosorbent assays targeting immunoglobulins G toward B. pseudomallei proteins: purified lipopolysaccharide (LPS) and recombinant proteins of alkyl hydroperoxide reductase subunit C (AhpC), hemolysin coregulated protein (Hcp1), and putative outer membrane porin protein (OmpH). Demographic factor analysis showed that species and breeding location were significant factors that were associated with seropositivity. Cynomolgus macaques and Jonggol facility have significantly association with seropositivity towards B. pseudomallei antigenic proteins. Enclosures in Jonggol are designed with soil flooring that may act as the reservoir of B. pseudomallei. Wet season and the observed grass-plucking behavior in those macaques may have contributed to the exposure to B. pseudomallei in the deeper layer of the soil. Pig-tailed macaques are predicted to be less-susceptible to the bacteria, since they showed lower immune response even though being reared in the same facility as some seropositive cynomolgus macaques. An evaluation of the immunoassay panel showed that there were strong and positive correlations of the recombinant protein assays (AhpC, Hcp1, and OmpH), whereas antibody level in LPS assay was higher but showed no correlation to the results of other assays. This may suggest that the development of antibody towards B. pseudomallei LPS is quicker and stronger, since LPS is a strong T-cell independent antigen. It may explain the reason that some animals had high level of antibody to LPS but not to other antigens. Even though the seropositivity ranges from 13-88% in several facilities, the presence of immunoglobulin G against B. pseudomallei does not necessarily mean that the macaques were currently having melioidosis, as the antibodies may reflect asymptomatic infection or a resolved infection. Efforts to culture throat, oral, wound, nasal, and rectal swabs of seropositive macaques resulted in no positive culture for B. pseudomallei. Based on previous reports by other researchers, macaques (including Macaca mulatta, Macaca fascicularis, and Macaca nemestrina) have been considered as animal species with moderate to high resistance towards melioidosis. Negative culture from seropositive animals in this study may indicate that those animals have been exposed to B. pseudomallei, but do not develop melioidosis, or the condition has been resolved. Environmental sampling from soil in several breeding facilities also resulted in no culturable B. pseudomallei, but the number of samples and area coverage was not adequate to represent the very large area of
Keyword: Burkholderia pseudomallei, melioidosis, nonhuman primates, surveillance