Distribution and Molecular Typing (MLST) of Non-O157 Diarrheagenic Escherichia coli Isolated from Retail Foods in South China

Abstract:

To investigate the distribution and characteristics of non-O157 diarrheagenic Escherichia coli (DEC) contamination in retail foods in south China, food samples from 12 cities in this region were collected randomly and examined using the GB/T 4789.36-2003 method, and the molecular identification of DEC was conducted using multiplex polymerase chain reaction. In addition, multilocus sequence typing (MLST) and the paper disk method were used to analyze the genetic characteristics and drug resistance of DEC strains. The results showed that DEC was detected in 164 samples from 1000 food samples, with a total contamination rate of 16.4%. Severe contaminations were found in meat and aquatic products. Of the five DEC pathotypes tested, enteropathogenic E. coli showed the highest detection rate (8.0%), followed by enterotoxigenic E. coli (6.2%), enteroinvasive E. coli (3.4%), and Shiga toxin-producing E. coli (0.4%). A total of 207 DEC isolates was obtained, and the MLST results showed 58 different sequence types (STs), including 44 reported STs and 14 novel STs. Cluster analysis indicated that eight clonal complexes (CCs) were obtained in these isolates, among which CC10 was the largest. The DEC isolates showed high resistance to tetracycline (72.5%), trimethoprim-sulfamethoxazole (66.2%), cephalothin (50.7%), ampicillin (56.5%), and chloramphenicol (48.3%). The results of this study indicate that related agencies should strengthen the monitoring of non-O157 DEC to reduce the risk of outbreaks of foodborne diseases.