Abstract:

Objective To study the clinical characteristics of Salmonella infection cases and the serotyping,molecular subtyping and drug resistance of Salmonella isolates in Panzhihua,Sichuan. Methods A total of 90 Salmonella isolates from 4 sentinel hospitals in Panzhihua were collected from 2018 to 2019. According to the National Pathogen Identification Network,serotyping determination,drug resistance determination and pulsed field gel electrophoresis（PFGE）were carried out. Results The 90 Salmonella isolates from clinical cases including 79 intestinal diarrhea cases and 11 extra-intestinal invasion cases were confirmed into 15 serotypes. The most common serotype from intestinal diarrhea cases was Salmonella typhimurium（45 isolates）,followed by Salmonella enteritidis（18 isolates）,Salmonella london（3 isolates）,Salmonella stanley（3 isolates） and Salmonella weltevreden（3 isolates）,while the most common serotype from extra-intestinal invasion cases was Salmonella enteritidis（6 isolates）,followed by Salmonella paratyphi A（2 isolates）,Salmonella typhimurium（1 case）,Salmonella derby（1 case）and Salmonella uzaramo（1 case）. Children under 5-year-old and 20-59-year-old adults were the high risk groups. There were more cases in males than in females,and spring and summer were the common seasons of high incidence of diarrhea. Drug resistance results of Salmonella typhimurium and Salmonella enteritidis had statistical significance（P<0.05）. Salmonella typhimurium isolates were still sensitive to fluoroquinolones and third-generation cephalosporins,while Salmonella enteritidis isolates were highly resistant to fluoroquinolones（nalidixic acid and ciprofloxacin）,and cefotaxime resistance rate was >20%. PFGE showed that Salmonella isolates from diarrhea cases had 3 dominant clusters,2 of which were multiple-drug resistant（MDR）. Salmonella enteritidis,Salmonella london,Salmonella stanley and Salmonella weltevreden isolates only had one drug resistant or sensitive cluster. Conclusions The Salmonella isolates in Panzhihua illustrate serotype diversity and MDR molecular clone. Salmonella typhimurium,Salmonella enteritidis and Salmonella enteritidis,Salmonella paratypli A are the most common serotypes from intestinal diarrhea and extra-intestinal invasion cases,respectively. Improving regional surveillance and sharing the big data of the National Pathogen Identification Network should be strengthened,so that we can have accurate response and early warning of various Salmonella outbreaks.

Key words: Salmonella, Serotype, Molecular clone, Drug resistence, Clinical diagnosis, Multiple-drug resistance