METHODS: We used transmission electron microscopy (TEM) to investigate post-mortem tissue sections of patients with clinical melioidosis to identify the localisation of a recently identified gut microbiome, B. pseudomallei within host cells. The intranuclear presence of B. pseudomallei was confirmed using transmission electron microscopy (TEM) of experimentally infected guinea pig spleen tissues and Live Z-stack, and ImageJ analysis of fluorescence microscopy analysis of in vitro infection of A549 human lung epithelial cells.
RESULTS: TEM investigations revealed intranuclear localization of B. pseudomallei in cells of infected human lung and guinea pig spleen tissues. We also found that B. pseudomallei induced actin polymerization following infection of A549 human lung epithelial cells. Infected A549 lung epithelial cells using 3D-Laser scanning confocal microscopy (LSCM) and immunofluorescence microscopy confirmed the intranuclear localization of B. pseudomallei.
CONCLUSION: B. pseudomallei was found within the nuclear compartment of host cells. The nucleus may play a role as an occult or transient niche for persistence of intracellular pathogens, potentially leading to recurrrent episodes or recrudescence of infection.
METHODS: We determined the ability of B. pseudomallei to invade and survive intracellularly in A549 human lung epithelial cells, and also investigated the early transcriptional responses using an Illumina HumanHT-12 v4 microarray platform, after three hours of exposure to live B. pseudomallei (BCMS) and its secreted proteins (CCMS).
RESULTS: We found that the ability of B. pseudomallei to invade and survive intracellularly correlated with increase of multiplicity of infection and duration of contact. Activation of host carbohydrate metabolism and apoptosis as well as suppression of amino acid metabolism and innate immune responses both by live bacteria and its secreted proteins were evident. These early events might be linked to initial activation of host genes directed towards bacterial dissemination from lungs to target organs (via proposed in vivo mechanisms) or to escape potential sensing by macrophages.
CONCLUSION: Understanding the early responses of A549 cells toward B. pseudomallei infection provide preliminary insights into the likely pathogenesis mechanisms underlying melioidosis, and could contribute to development of novel intervention strategies to combat B. pseudomallei infections.
OBJECTIVE: We sought to review case reports of melioidosis from Malaysia.
METHODS: We conducted a computerized search of literature resources including PubMed, OVID, Scopus, MEDLINE and the COCHRANE database to identify published case reports from 1975 to 2015. We abstracted information on clinical characteristics, exposure history, comorbid conditions, management and outcome.
RESULTS: Overall, 67 cases were reported with 29 (43%) deaths; the median age was 44 years, and a male preponderance (84%) was noted. Forty-one cases (61%) were bacteremic, and fatal septic shock occurred in 13 (19%) within 24-48 hours of admission; nine of the 13 cases were not specifically treated for melioidosis as confirmatory evidence was available only after death. Diabetes mellitus (n = 36, 54%) was the most common risk factor. Twenty-six cases (39%) had a history of exposure to contaminated soil/water or employment in high-risk occupations. Pneumonia (n = 24, 36%) was the most common primary clinical presentation followed by soft tissue abscess (n = 22, 33%). Other types of clinical presentations were less common-genitourinary (n = 5), neurological (n = 5), osteomyelitis/septic arthritis (n = 4) and skin (n = 2); five cases had no evidence of a focus of infection. With regard to internal foci of infection, abscesses of the subcutaneous tissue (n = 14, 21%) was the most common followed by liver (18%); abscesses of the spleen and lung were the third most common (12% each). Seven of 56 males were reported to have prostatic abscesses. Mycotic pseudoaneurysm occurred in five cases. Only one case of parotid abscess was reported in an adult. Of the 67 cases, 13 were children (≤ 18 years of age) with seven deaths; five of the 13 were neonates presenting primarily with bronchopneumonia, four of whom died. Older children had a similar presentation as adults; no case of parotid abscess was reported among children.
CONCLUSIONS: The clinical patterns of cases reported from Malaysia are consistent for the most part from previous case reports from South and Southeast Asia with regard to common primary presentations of pneumonia and soft tissue abscesses, and diabetes as a major risk factor. Bacteremic melioidosis carried a poor prognosis and septic shock was strong predictor of mortality. Differences included the occurrence of: primary neurological infection was higher in Malaysia compared to reports outside Malaysia; internal foci of infection such as abscesses of the liver, spleen, prostate, and mycotic pseudoaneurysms were higher than previously reported in the region. No parotid abscess was reported among children. Early recognition of the disease is the cornerstone of management. In clinical situations of community-acquired sepsis and/or pneumonia, where laboratory bacteriological confirmation is not possible, empirical treatment with antimicrobials for B. pseudomallei is recommended.