Ke Cw

High prevalence and diversity of pre‐CTXΦ alleles in the environmental Vibrio cholerae O1 and O139 strains in the Zhujiang River estuary

Toxigenic conversion of environmental Vibrio cholerae strains through lysogenic infection by the phage CTXΦ is an important step in the emergence of new pathogenic clones. The precursor form of the CTXΦ phage, pre-CTXΦ, does not carry the cholera toxin gene. During our investigation, we frequently found pre-CTXΦ prophages in non-toxigenic isolates in the serogroups of O1 and O139 strains in the Zhujiang estuary. We observed high amounts of sequence variation of rstR and gIII(CTX) in the pre-CTXΦ alleles as well as in the tcpA sequences within the strains. In addition, a new pre-CTXΦ allele, with a novel rstR sequence type and hybrid RS2, was identified. Our findings show that active, complicated gene recombination and horizontal transfer of pre-CTXΦs occurs within V. cholerae environmental strains, which creates a complex intermediate pool for the generation of toxigenic clones in the estuarine environment.

Characterization of environmental Vibrio cholerae serogroups O1 and O139 in the Pearl River Estuary, China.

Toxigenic isolates of Vibrio cholerae serogroups O1 and O139 from aquatic reservoirs are a key source for recurrent epidemics of cholera in human populations. However, we do not have an optimal understanding of the microbiology of the strains within these reservoirs, particularly outside of the time periods when there are active cholera cases in the surrounding community. The main objective of the present study was to identify and characterize V. cholerae O1 and O139 in the Pearl River Estuary at a time when active disease was not being identified, despite prior occurrence of epidemic cholera in the region. Water samples were collected at 24 sites in the research area at monthly intervals between 2007 and 2010, and screened for the presence of V. cholerae O1 and O139. All isolates were screened for the presence of ctxAB, ompW, toxR, and tcpA genes. Multilocus variable number tandem repeat analysis (MLVA) was used to assess possible relationships among strains. The results show that Vibrio cholerae O1 or O139 was isolated, on average, from 6.7% of the sites screened at each time point. All V. cholerae O1 and O139 isolates were ctxAB negative, and 37% were positive for tcpA. Isolation was most common in the oldest, most urbanized district compared with other districts, and was associated with lower pH. Despite year-to-year variability in isolation rates, there was no evidence of seasonality. MLVA of 27 selected isolates showed evidence of high genetic diversity, with no evidence of clustering by year or geographic location. In this region where cholera has been epidemic in the past, there is evidence of environmental persistence of V. cholerae O1 and O139 strains. However, environmental strains were consistently nontoxigenic, with a high level of genetic diversity; their role as current or future agents of human disease remains uncertain.

First co-infection case of melioidosis and Japanese encephalitis in China

BackgroundMelioidosis is endemic in Southeast Asia and northern Australia. Infection usually follows percutaneous inoculation or inhalation or ingestion of the causative bacterium, Burkholderia pseudomallei, which is present in soil and surface water in endemic regions. Japanese encephalitis (JE) is a vector-borne viral zoonosis caused by Japanese encephalitis virus (JEV), leading to epidemic encephalitis in Southeast Asia. Both B. pseudomallei and JEV have spread dominantly in the Hainan and Guangdong provinces in China. Here we reported the first case of co-infection of B. pseudomallei and JEV, which was discovered in Huizhou in the Guangdong province in June 2016.Case presentationA 52-year-old man was admitted to the hospital with acute febrile illness and headache, diagnosed as respiratory infection, central nervous system (CNS) infection, septicemia, and hepatic dysfunction. Based on B. pseudomallei-positive blood and cerebrospinal fluid (CSF) cultures, the patient was diagnosed with melioidosis and treated aggressively with antibiotics. However, the patient failed to make a full recovery. Further laboratory tests focused on CNS infection were conducted. The co-infection of B. pseudomallei and JEV was confirmed after the positive IgM antibodies of JEV were detected in both CSF and blood. After diagnosis of co-infection with B. pseudomallei and JEV, the patient was provided supportive care in hospital and recovered after approximately 3 weeks.ConclusionGiven the possibility of co-infection of B. pseudomallei and JEV, as well as variable case presentations, it is critical to enhance the awareness, detection, and treatment of co-infection in regard to melioidosis.