Preliminary study on incidence of melioidosis and molecular characteristics of clinical strains of Burkholderia pseudomallei after Typhoon Rammasun attack

Objective To understand the incidence of melioidosis and to study the molecular characteristics of Burkholderia pseudomallei clinical strains after Typhoon Rammasun attack in Hainan island. Methods A 2-month surveillance for melioidosis was carried out in three general hospitals in Hainan after typhoon attack on July 18,2014. General and clinical information of melioidosis cases were collected and analyzed with the methods of descriptive epidemiology and geographic informatics. Clinical isolates of B. pseudomallei were characterized by multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and 4-locus multilocus variable number tandem repeat analysis (MLVA-4) to analyze their relationships and the homology. Results During the investigation, a total of 16 confirmed cases of melioidosis were found, higher than that during the same period in 2013 (7 cases). Among these cases, 12 (75.0%) occurred within 4 weeks after the disaster, and the other 4 occurred within 5-8 weeks. All the cases were from northern Hainan, an area seriously affected by this typhoon. Nine cases were distributed in a zonal area of Wenchang and Haikou, where the eye of the typhoon passed. The common symptoms of the cases included pneumonia (75.0%) and sepsis (68.8%). Eight cases were fatal (50.0%). Molecular typing divided the 16 clinical isolates into 12 sequence types (STs), 13 PFGE patterns and 15 MLVA genotypes, indicating high genetic polymorphism of the strains. Conclusion The clustering of melioidosis cases was observed after Typhoon Rammasun attack in Hainan. Related clinical isolates of B. pseudomallei were genetically diverse, excluding the possibility of bioterrorism attack. Further investigations are needed to clarify the infection cause and its relationship with the activity of typhoon.