Automated immunomagnetic separation for the detection of Escherichia coli O157:H7 from spinach.
Escherichia coli O157:H7 is a major cause of foodborne illness and methods for rapid and sensitive detection of this deadly pathogen are needed to protect consumers. The use of immunomagnetic separation (IMS) for capturing and detecting foodborne pathogens has gained popularity, partially due to the introduction of automated and high throughput IMS instrumentation. Three methods for automated IMS that test different sample volumes, Kingfisher mL, Pathatrix Auto, and Pathatrix Ultra, were compared using microbiological detection of E. coli O157:H7 from buffered peptone water (BPW), in the presence of background microbial flora derived from spinach leaves, and from culture enrichments from artificially contaminated spinach leaves. The average efficiencies of capture of E. coli O157:H7 using the three methods were 32.1%, 3.7%, and 1.3%, respectively, in BPW; 43.4%, 8.8%, 2.9%, respectively, in the presence of spinach microbial flora; and 63.0%, 7.0%, and 6.3%, respectively, from artificially contaminated spinach. Despite the large differences in IMS capture efficiencies between the KingFisher and two Pathatrix methods, all three methods allowed the detection of E. coli O157:H7 from spinach that was artificially contaminated with the pathogen at relatively high (25 cfu/30 g sample) and low (1 cfu/30 g sample) levels after 4-6h of culture enrichment. The differences in capture efficiency were compensated for by the differences in sample volume used by the KingFisher mL (1 mL), Pathatrix Auto (50 mL) and Pathatrix Ultra (250 mL) instruments. Thus, despite the reduced capture efficiencies observed for the Pathatrix methods, the large increase in sample volume results in a greater number of captured cells for downstream detection resulting in improved detection sensitivity.
MOST-USDA Joint Research Center for Food Safety, Department of Food Science and Technology & Bor Luh Food Safety Center, Shanghai Jiao Tong University, 800 Dongchuan Rd., Shanghai 200240, China; USDA-MOST Joint Research Center for Food Safety, Molecular Characterization of Foodborne Pathogens Research Unit, United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center (USDA-ARS-ERRC), 600 E. Mermaid Lane, Wyndmoor, PA 19038, United States.
Jing
J
Chen
MOST-USDA Joint Research Center for Food Safety, Department of Food Science and Technology & Bor Luh Food Safety Center, Shanghai Jiao Tong University, 800 Dongchuan Rd., Shanghai 200240, China. Electronic address: xmshi@sjtu.edu.cn.
Xianming
X
Shi
USDA-MOST Joint Research Center for Food Safety, Molecular Characterization of Foodborne Pathogens Research Unit, United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center (USDA-ARS-ERRC), 600 E. Mermaid Lane, Wyndmoor, PA 19038, United States.
Andrew G
AG
Gehring
USDA-MOST Joint Research Center for Food Safety, Molecular Characterization of Foodborne Pathogens Research Unit, United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center (USDA-ARS-ERRC), 600 E. Mermaid Lane, Wyndmoor, PA 19038, United States. Electronic address: george.paoli@ars.usda.gov.
George C
GC
Paoli
D019453:Escherichia coli O157 / Q000302:isolation & purification* / Q000502:physiology; D005516:Food Microbiology / Q000379:methods*; D018189:Immunomagnetic Separation / Q000592:standards*; D012680:Sensitivity and Specificity; D018724:Spinacia oleracea / Q000382:microbiology*
E. coli O157:H7; Immunomagnetic separation; Pathogen detection