Methodological assessment and detection base line based prediction of Salmonella carriage level in catering and public service employees in Yulin

ObjectiveTo predict the carriage level of Salmonella in catering and public service employees in Yulin in Guangxi based on the base line and methodological assessment of Salmonella detection process.

MethodThe selective enrichment broth (SBG) and selective plates (CAS, XLD, DHL) were used to establish Salmonella screening techniques process. Statistical parameters were obtained through the detections of stock strains and 408 stool samples of the employees for the evaluation of the sensitivity, specificity and positive predictive value of different combination process (SBG+CAS/XLD/DHL) in the detection of Salmonella. The Salmonella carriage level in catering and public service employees in Yulin from 2014 to 2017 were adjusted and predicted according to the sensitivity of SBG-DHL in Salmonella isolation.

ResultsReference stock strain detection showed that the sensitivity and specificity of CAS, XLD and DHL were 100.00% and 96.67%, 100.00% and 83.33%, 83.33% and 50.00%, respectively. A total of 22 Salmonella strains were isolated from 408 stool samples by using combined plates, the positive rate was 5.39%. The sensitivity and positive predictive rates were 95.45% and 89.23% for CAS, 86.36% and 27.72% for XLD, 68.18% and 16.15% for DHL, 100.00% and 29.27% for CAS+XLD, respectively. A Salmonella Rissen isolate with both hydrogen sulfide-negative and positive clones was isolated from an asymptomatic carrier by CAS and XLD. Through the calibration and prediction, the annual rate of Salmonella carriage was 3.35% in the employees from 2014 to 2017. Accordingly, we predicted that the Salmonella carriage rate was 3 350/100 000 in catering and public service employees in Yulin of Guangxi.

ConclusionThe sensitivity and positive predictive rate of Salmonella detection can be used as the indicators for evaluation of detection quality and methodologies. Big data confirmed that the high Salmonella carriage arte was persistent in catering and public service employees in southern China. It is necessary to strengthen the screening of asymptomatic Salmonella carriers to reduce the recessive spread of food-borne pathogenic bacteria.