ABSTRACT
Objectives: To analyze the causes of a foodborne outbreak in rural areas of Xinjiang between April 2 and April 5 in 2016. Methods: Cases and the relevant background information were obtained by consulting outpatient records of local health centers and regional people's hospitals and interviewing doctors and residents. All samples were collected by the laboratory test through epidemiological and food hygiene investigations. The χ2 test (Fisher's exact probability method) was used to compare differences in incidence rates. Molecular typing, virulence genes and single nucleotide polymorphisms (SNPS) were analyzed by using Pulsed Field Gel Electrophoresis (PFGE) and Whole Genome Sequencing (WGS). Results: A total of 142 cases were found in this study, with incidence rate at 5.7‰ (142/24 979). Among all cases, the main symptoms were nausea (94%), vomiting (92%) and abdominal pain (67%), and the incubation period was about 2 h (1-7.5 h). There were 16 Staphylococcus aureus isolates identified and all of them could produce A+C+E mixed enterotoxin. PFGE showed 100% homology. WGS further revealed that there were 9 and 1 strains contained by Sequence Type 1 (ST1) and ST5405, respectively. All ST1 strains were in the same clade on the genome tree. Among these, 7 strains shared close proximity (74 SNPs) and 2 strains shared close relationships as well (127 SNPs). The S. aureus isolates that caused the outbreak were introduced by a mutant isolate from the milk supply station. Conclusions: This foodborne outbreak was mainly caused by Staphylococcus aureus contamination.
Subject(s)
Humans , Disease Outbreaks , Electrophoresis, Gel, Pulsed-Field , Foodborne Diseases/epidemiology , Staphylococcus aureus/geneticsABSTRACT
On June 6,2016,an outbreak of suspected cutaneous anthrax was reported by T County CDC,Xinjiang Uygur Autonomous,China.An investigation was carried out to determine the magnitude and risk factors and to recommend control measures.Suspected cases were defined as any villager in T county residents whose skin appeared rash,blisters,ulceration,swelling of black eschar or ulcer between May 1 and June 8.Confirmed case were defined as suspected case plus serological positive,real-time polymerase chain reaction (PCR) positive or Bacillus anthraci isolated.We interviewed clinicians and reviewed medical files in the township and city hospital,and visited all households searching for cases.A case-control study was conducted to investigate the risk factors of human anthrax infection.Three types of specimens were collected and tested by serological detection,real-time polymerase chain reaction (PCR) and bacterial culture.Through epidemiological investigation,15 families purchased beef of a sick cow on May 26,2016.Between 29 May and 3 June,ten people from these families were diagnosed as skin anthrax.Among them,six were confirmed cases and four were suspected cases.The attack rate was 20％.The incubation period was 3 to 7 days with average incubation 5 days.The nain clinical manifestations were hand skin anthrax carbuncle.Case control study showed that the incidences of people who exposing or not exposing to contaminated beefs significantly different,with 53％ and 0％ respectively.Blood serums from six patients showed that specific antibody titer appeared to increase more than 4 times.B.anthraci was isolated from herpes fluid of one patient.B.anthraci nucleic acid was detected from beef collected from four families.The outbreak was caused by the villagers exposed sick cow which infected by B.anthraci.Contaminated beef caused the infections.