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J Med Entomol. 2017 May 1;54(3):726-732. doi: 10.1093/jme/tjw240.

House Flies in the Confined Cattle Environment Carry Non-O157 Shiga Toxin-Producing Escherichia coli.

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Department of Entomology, Kansas State University, 123 Waters Hall, Manhattan, KS 66506 (;;
Department of Diagnostic Medicine and Pathobiology, Kansas State University, 221K Mosier Hall, Manhattan, KS 66506 ( ).
Current address: Department of Biology, Pittsburg State University, 321 Heckert-Wells Hall, Pittsburg, KS 66762.
Department of Entomology, Kansas State University, 123 Waters Hall, Manhattan, KS 66506 (;; ).


Cattle manure is one of the primary larval developmental habitats of house flies, Musca domestica (L.). Cattle serve as asymptomatic reservoirs of Shiga toxin-producing Escherichia coli (STEC), and bacteria are released into the environment in cattle feces. The USDA-FSIS declared seven STEC serogroups (O157, O26, O45, O103, O145, O121, and O111) as adulterants in beef products. In addition, the serogroup O104 was a culprit of a large outbreak in Germany in 2011. Our study aimed to assess the prevalence of seven non-O157 STEC (O26, O45, O145, O103, O121, O111, and O104) serogroups in adult house flies. Flies (n = 463) were collected from nine feedlots and three dairy farms in six states in the United States and individually processed. This involved a culturing approach with immunomagnetic separation followed by multiplex polymerase chain reactions for detection of individual serogroups and virulence traits. The concentration of bacteria on modified Possé agar ranged between 1.0 × 101 and 7.0 × 107 (mean: 1.5 ± 0.3 × 106) CFU/fly. Out of 463 house flies, 159 (34.3%) carried one or more of six E. coli serogroups of interest. However, STEC was found in 1.5% of house flies from feedlots only. These were E. coli O103 and O104 harboring stx1 and ehxA and E. coli O45 with stx1, eae, and ehxA. This is the first study reporting the isolation of non-O157 STEC in house flies from the confined cattle environment and indicating a potential role of this insect as a vector and reservoir of non-O157 STEC in confined beef cattle.


Escherichia coli; Shiga toxin; feedlot; house fly; non-O157 STEC

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