Use of Bioluminescent Escherichia coli to Determine Retention During the Life Cycle of the Housefly, Musca domestica (Diptera: Muscidae, L)

Abstract

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.

Ingested Salmonella enterica, Cronobacter sakazakii, Escherichia coli O157:H7, and Listeria monocytogenes: transmission dynamics from adult house flies to their eggs and first filial (F1) generation adults

“…Although E. coli O157:H7 was present in samples containing pooled house fly eggs, this pathogen did not persist throughout metamorphosis. This finding was opposite to other studies that have reported the ingestion of non-pathogenic E. coli by house fly larva and their persistence throughout pupae and newly emerged adults [ 48 , 49 ]. However, in this study we did not quantify the amount of E. coli O157:H7 present in the larval rearing substrate; hence, the levels of this pathogen that were likely to be ingested by house fly larvae were unknown and probably low enough to avoid their persistence through the house fly life cycle.…”

Temporospatial fate of bacteria and immune effector expression in house flies fed GFP‐Escherichia coliO157:H7

“…Taken in conjunction with previous data (Kobayashi et al ., ; Sasaki et al ., ), this indicates that house flies potentially serve as significant reservoirs of this pathogen for at least 12 h. Interestingly, recent work by Schuster et al . () has shown that house fly larvae that fed on E. coli ‐contaminated substrate carried bacteria trans‐stadially and newly eclosed flies harboured as many as 50 CFU. The possibility of trans‐stadial survival of E. coli O157:H7 deserves further study as this would complicate the epidemiological picture.…”

Muscoid Diptera as potential vectors of bacterial agents on dairy farms in the northern region of Paraná, Brazil

“…In the absence of a preferential substrate, the flies search for alternative substrates (D'ALMEIDA; MELLO, 1996). Moreover, adult flies can retain pathogenic bacteria acquired in the larval phase (SCHUSTER et al, 2013).…”