An Investigation of an Acute Gastroenteritis Outbreak: Cronobacter sakazakii, a Potential Cause of Food-Borne Illness.

Wei Yong,Xiaochao Shi,Jie Ding,Junning Wang,Mingming Chen,Guoxiang Xie,Baofu Guo,Xiao Jiang,Yanhua Ye,Tingting Cheng

doi:10.3389/fmicb.2018.02549

Abstract

Whole genome sequencing (WGS) has been widely used in traceability of food-borne outbreaks nowadays. Here, an interesting connection between Cronobacter sakazakii and food-borne acute gastroenteritis (AGE) was noticed. In October 2016, an AGE outbreak affecting 156 cases occurred in a local senior high school. Case-control study including 70 case-patients and 295 controls indicated a strong association between eating supper at school canteen of the outbreak onset and AGE, as revealed by the Odds Ratio (OR: 95.32). Six recovered Cronobacter strains were evaluated and compared using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and WGS. A phylogenetic tree of whole genomic single nucleotide polymorphisms (wgSNPs) were generated to traceback the potential contamination source in this outbreak. C. sakazakii isolates S2 from a patient’s rectal swab and S4 from leftover food sample shared identical PFGE pattern and sequence type (ST73), and clustered tightly together in the SNP phylogenetic tree. C. sakazakii isolates S5 and S6 from food delivery containers were both ST4 but with different PFGE patterns. Cronobacter isolates S1 and S3 from two patients’ rectal swab were sequenced to be C. malonaticus and shared another PFGE pattern (ST567). The interesting feature of this study was the implication of C. sakazakii as a causative agent in food-borne AGE occurring in healthy adults, although C. sakazakii is considered as an opportunistic pathogen and generally affects neonates, infants and immunocompromised adults.

Highlights

Cronobacter spp. is a member of the family Enterobacteriaceae, and is known as emerging opportunistic food-borne pathogen for humans
Combined with other laboratory results and epidemiological analysis which indicated the possible link between C. sakazakii and the outbreak, we strongly suggested that C. sakazakii may lead to intestinal disorders independently and even cause acute gastroenteritis (AGE) outbreaks in some occasions
On the day of outbreak onset, lunch and dinner were both provided by a catering company outside school with the meal cooked, box-packed and delivered to school and distributed by employees in the school canteen

Summary

Introduction

Cronobacter spp. (formerly defined as Enterobacter sakazakii) is a member of the family Enterobacteriaceae, and is known as emerging opportunistic food-borne pathogen for humans. Cronobacter spp. was reported to have the capacity to cause nosocomial outbreaks in neonatal intensive care unit (NICU) in different countries (van Acker et al, 2001; Caubilla-Barron et al, 2007; Hariri et al, 2013) This organism is widely distributed in nature and has been isolated from various environmental sources including PIF production facilities, hospitals, and households (Masaki et al, 2001; Kandhai et al, 2004; Mullane et al, 2007), and from different food categories such as dried food, produce, spice, and even expressed breast milk (Baumgartner et al, 2009; Beuchat et al, 2009; Healy et al, 2010; McMullan et al, 2018). Liu reported that the positive rate of Cronobacter spp. and C. sakazakii was 0.54–0.27% in healthy adults, respectively, slightly lower than 1.2–0.58% in adults with acute diarrheal illness, respectively, and with no statistically difference (Liu et al, 2013)

Methods

Results

Discussion

Conclusion