Background In recent years, "online ordering takeout food" has become popular among various customer groups such as students and office workers and part of daily life for the residents in Guangzhou. Recent frequent incidents concerning online ordering takeout food safety and hygiene have aroused public concern. However, its microbial contamination is rarely studied.

Objective This study is designed to investigate the microbial contamination status of online ordering takeout food in Guangzhou, and provide evidence for the food safety supervision and further research on online ordering takeout food.

Methods A total of 856 samples of four kinds of takeout food including Chinese box food, sushi, gimbap, and noodle with hot soup were collected through online ordering in 10 districts of Guangzhou in March, June to September, and November of 2017. Examinations of total aerobic bacteria, Escherichia coli, and five common foodborne pathogens (Salmonella, Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, and Vibrio parahaemolyticus) were carried out according to standard microbiological testing methods stipulated by the GB 4789 National Food Safety Standards:Food Microbiological Examination. According to the DBS 44/006-2016 Local Standards of Food Safety in Guangdong Province:Microbial Limits of Non-prepackaged Ready-to-eat Food, the samples were evaluated and categorized as disqualified if the count of any pathogens reached the "unqualified" limit. Base on geographical location and population distribution, the sample sites were divided into suburban and downtown areas, and the results were analyzed.

Results The overall unqualified rate of selected microbial indicators online ordering takeout food samples was 25.70% (220/856), and the most prevalent pathogens were Escherichia coli (17.52%, 150/856), followed by total aerobic bacteria (14.72%, 126/856), and foodborne pathogens (1.17%, 10/856). The unqualified rate was significantly higher in samples from downtown areas (28.78%, 181/629) than in those from suburban areas (17.18%, 39/227) (χ²=11.744, P=0.001). There was a significant difference in the unqualified rate among different food types (χ²=40.481, P=0.001), with the highest prevalence rates of Escherichia coli and total aerobic bacteria found in gimbap (47.96%, 47/98) and Chinese box food (19.93%, 111/557) samples, respectively. A significantly higher unqualified rate was found during summer and autumn (from June to September, 28.67%, 164/572) than during spring and winter (March and November, 19.72%, 56/284) (χ²=7.966, P=0.005).

Conclusion Poor sanitary conditions due to microbial contamination are generally found in online ordering takeout food in Guangzhou. It is urgent for relevant government departments to strengthen the hygienic supervision and monitoring of online ordering takeout food.