Pulsed-field gel electrophoresis (PFGE)molecular subtyping and drug resistance of Salmonella enteritidiss trains isolated in Longyan city
Objective 
To analyze the pulse-field gel electrophoresis (PFGE) patterns and antibiotic resistance of Salmonella enteritidisstrains isolated in Longyan city in order to provide reference for effective control, clinical diagnosis and treatment of outbreaks of food-borne diseases. 
 
 
Methods 
Seventy-seven Salmonella enteritidis strains isolated from food poisoning cases, livestock and poultry meat samples collected for food safety risk monitoring and sporadic cases in 2014 and 2016 were analyzed by PFGE. Antibiotic susceptibility testing was carried out to determine the minimum inhibitory concentrations (MIC) of 16 common antibiotics to 57 strains. 
 
 
Results 
Seventeen PFGE types were identified among the 77 Salmonella strains including three predominant types (P4, P6 and P8) and were grouped into three major pulsotypes (Cluster1-3) at 90% similarity level. The predominant types causing outbreaks of Salmonella enteritidis infection were P8, P6, P4 and P14, which were responsible for five cases of food poisoning.These isolated strains were highly resistant to nalidixic acid (93%), followed by resistance towards ampicillin (74%) and streptomycin (54%). Forty-one strains were resistant to three or more antibiotics (71.93%). 
 
 
Conclusion 
The PFGE types of Salmonella enteritidis strains isolated in Longyan city exhibit polymorphism and are clustered into three major pulsotypes. PFGE molecular typing can provide early-warning of sporadic outbreaks and help to identify the sources of infections in Salmonella enteritidis-related food poisoning. Attentions should be paid to multidrug resistant Salmonella enteritidis. Surveillance for multidrug resistant strains and usage of antibiotics should be strengthened. 
 
 
Key words: 
Salmonella enteritis; PFGE molecular typing; Cluster analysis; Minimum inhibitory concentration; Multidrug resistance