Schuster Greta L, Donaldson Janet R, Buntyn Joe O, Duoss Heather A, Callaway Todd R, Carroll Jeff A, Falkenberg Shollie M, Schmidt Ty B
Department of Agriculture, Agribusiness, and Environmental Sciences, Texas A&M-Kingsville, Kingsville, Texas, USA.
Foodborne Pathog Dis. 2013 May;10(5):442-7. doi: 10.1089/fpd.2012.1326. Epub 2013 Mar 28.
Researchers have documented that the housefly (Musca domestica) can serve as a vector for the spread of foodborne pathogens to livestock, food, and humans. Most studies have investigated Musca domestica as a vector only after the fly comes into contact or consumes the pathogen as an adult. The objective of this study was to determine whether the larvae of Musca domestica could ingest Escherichia coli from bovine manure and whether the E. coli could survive the metamorphosis process and be transmitted. Larvae (n=960) were incubated in sterilized bovine manure inoculated with 0, 3, 5, and 8 log10 colony-forming units (CFU)/mL of bioluminescent E. coli for 24 (larvae stage), 48 (larvae stage), 120 (pupae stage), and 192 h (adult stage). Larvae incubated for 24 h in bovine manure possessed 0.0, 2.7, 2.9, and 3.5 log(10) CFU/mL of E. coli, from inoculated with 0, 3, 5, and 8 log(10) CFU/mL of E. coli, respectively. Concentrations of E. coli within the pupae were 0.0, 1.7, 1.9, and 2.2 log(10) CFU/mL for each inoculation concentration, respectively. Flies that emerged from the pupae stage contained 0.0, 1.3, 2.2, and 1.7 log(10) CFU/mL of E. coli from larvae incubated in manure inoculated with concentrations of E. coli, respectively. These results suggest the housefly can emerge with quantities of E. coli. While this was an enteropathogenic E. coli (EPEC), these data may suggest that if the fly is capable of retaining similar concentrations of an enterohemorrhagic E. coli (EHEC), these concentrations may be capable of initiating illness in humans. Furthermore, the E. coli concentration within and on adult flies is related to environmental exposure. It must be noted that larvae were incubated in sterilized bovine manure, and there was no other bacterial competition for the E. coli. Thus, the rate of positive flies and concentrations present when flies emerged may vary under more realistic conditions.
研究人员已记录到家蝇（家蝇属）可作为食源性病原体传播给牲畜、食物和人类的媒介。大多数研究仅在成年家蝇接触或摄食病原体后才将其作为媒介进行调查。本研究的目的是确定家蝇幼虫是否能从牛粪中摄取大肠杆菌，以及大肠杆菌能否在变态过程中存活并传播。将幼虫（n = 960）在接种了0、3、5和8 log10菌落形成单位（CFU）/mL生物发光大肠杆菌的灭菌牛粪中培养24小时（幼虫阶段）、48小时（幼虫阶段）、120小时（蛹阶段）和192小时（成虫阶段）。在牛粪中培养24小时的幼虫，分别接种0、3、5和8 log(10) CFU/mL大肠杆菌后，其体内大肠杆菌浓度分别为0.0、2.7、2.9和3.5 log(10) CFU/mL。对于每种接种浓度，蛹内大肠杆菌浓度分别为0.0、1.7、1.9和2.2 log(10) CFU/mL。从蛹阶段羽化出的苍蝇，分别在接种不同浓度大肠杆菌的牛粪中培养幼虫后，其体内大肠杆菌浓度分别为0.0、1.3、2.2和1.7 log(10) CFU/mL。这些结果表明家蝇羽化时体内可能携带一定数量的大肠杆菌。虽然这是一种肠致病性大肠杆菌（EPEC），但这些数据可能表明，如果家蝇能够保留类似浓度的肠出血性大肠杆菌（EHEC），这些浓度可能会引发人类疾病。此外，成年苍蝇体内和体表的大肠杆菌浓度与环境暴露有关。必须注意的是，幼虫是在灭菌牛粪中培养的，且没有其他细菌与大肠杆菌竞争。因此，在更实际的条件下，羽化时阳性苍蝇的比例和体内大肠杆菌浓度可能会有所不同。
