Fleming A, Kumar H V, Joyner C, Reynolds A, Nayduch D
Department of Biology, Georgia Southern University, Statesboro, GA, U.S.A.
Med Vet Entomol. 2014 Dec;28(4):364-71. doi: 10.1111/mve.12056. Epub 2014 Apr 9.
The house fly Musca domestica L. (Diptera: Muscidae) harbours and transmits a variety of human enteropathogens including Escherichia coli (Enterobacteriales: Enterobacteriaceae) O157:H7. Interactions between ingested bacteria and the fly gut directly impact bacterial persistence, survival and ultimately fly vector competence. We assessed the temporospatial fate of green fluorescent protein (GFP)-expressing E. coli O157:H7 (GFP-ECO157) in house flies along with fly antimicrobial responses up to 12 h post-ingestion. In flies fed GFP-ECO157, culture and microscopy revealed a steady decrease in bacterial load over 12 h, which is likely to be attributable to the combined effects of immobilization within the peritrophic matrix, lysis and peristaltic excretion. However, flies can putatively transmit this pathogen in excreta because intact bacteria were observed in the crop and rectum. Quantitative reverse-transcriptase polymerase chain reaction analysis of antimicrobial peptides (AMPs) and lysozyme gene expression showed minimal upregulation in both the gut and carcass of house flies fed GFP-ECO157. However, these genes were upregulated in fly heads and salivary glands, and effector proteins were detected in the gut in some flies. Collectively, these data indicate that house flies can serve as reservoirs of E. coli O157:H7 for up to 12 h, and factors in addition to AMPs and lysozyme may contribute to bacteria destruction in the gut.
家蝇（Musca domestica L.，双翅目：蝇科）携带并传播多种人类肠道病原体，包括大肠杆菌（肠杆菌目：肠杆菌科）O157:H7。摄入的细菌与家蝇肠道之间的相互作用直接影响细菌的持久性、存活率以及最终家蝇的传播能力。我们评估了表达绿色荧光蛋白（GFP）的大肠杆菌O157:H7（GFP-ECO157）在家蝇体内的时空命运，以及摄入后长达12小时的家蝇抗菌反应。在用GFP-ECO157喂食的家蝇中，培养和显微镜观察显示，细菌载量在12小时内稳步下降，这可能归因于被固定在围食膜内、裂解和蠕动排泄的综合作用。然而，家蝇可能会通过排泄物传播这种病原体，因为在嗉囊和直肠中观察到了完整的细菌。对抗菌肽（AMPs）和溶菌酶基因表达的定量逆转录聚合酶链反应分析表明，在用GFP-ECO157喂食的家蝇的肠道和胴体中，上调幅度最小。然而，这些基因在蝇头和唾液腺中上调，并且在一些家蝇的肠道中检测到了效应蛋白。总体而言，这些数据表明，家蝇可在长达12小时内作为大肠杆菌O157:H7的宿主，并且除了AMPs和溶菌酶之外的因素可能有助于肠道内细菌的破坏。
