Attenuation of veterinary antibiotics in full-scale vermicomposting of swine manure via the housefly larvae (Musca domestica)

Abstract

Animal waste from concentrated swine farms is widely considered to be a source of environmental pollution, and the introduction of veterinary antibiotics in animal manure to ecosystems is rapidly becoming a major public health concern. A housefly larvae (Musca domestica) vermireactor has been increasingly adopted for swine manure value-added bioconversion and pollution control, but few studies have investigated its efficiency on antibiotic attenuation during manure vermicomposting. In this study we explored the capacity and related attenuation mechanisms of antibiotic degradation and its linkage with waste reduction by field sampling during a typical cycle (6 days) of full-scale larvae manure vermicomposting. Nine antibiotics were dramatically removed during the 6-day vermicomposting process, including tetracyclines, sulfonamides, and fluoroquinolones. Of these, oxytetracycline and ciprofloxacin exhibited the greater reduction rate of 23.8 and 32.9 mg m−2, respectively. Environmental temperature, pH, and total phosphorus were negatively linked to the level of residual antibiotics, while organic matter, total Kjeldahl nitrogen, microbial respiration intensity, and moisture exhibited a positive effect. Pyrosequencing data revealed that the dominant phyla related to Firmicutes, Bacteroidetes, and Proteobacteria accelerated manure biodegradation likely through enzyme catalytic reactions, which may enhance antibiotic attenuation during vermicomposting.

Housefly Larva Vermicomposting Efficiently Attenuates Antibiotic Resistance Genes in Swine Manure, with Concomitant Bacterial Population Changes

“…The housefly larva vermicomposting processes consisted of several stages in series: (i) seed pupation and eclosion, (ii) housefly oviposition, (iii) larval inoculation in unprocessed manure and vermicomposting, (iv) separation of larval residues, and (v) seed sifting and breeding (9). The unprocessed manure, with a surface density of 11.0 kg m Ϫ2 , was evenly spread on the surface of cement block pools (7.2 ϫ 2.5 ϫ 0.2 m) in greenhouse-assisted larva vermireactors prior to larva inoculation (10). The thickness of the unprocessed manure was approximately 5 cm, and juvenile larvae (12 h old) were applied to the surface of the manure with an average population density of 580,000 m Ϫ2 .…”

“…The life cycle of vermicomposting with inoculated larvae is 5 (summer) to 10 (winter) days, depending on the ambient temperature. After vermicomposting, more than half of the total weight of the added manure was reduced, and the associated total antimicrobial mass was also significantly attenuated (10). The mass reduction was primarily due to moisture removal and organic biodegradation by larval metabolism and growth.…”

“…The mass reduction was primarily due to moisture removal and organic biodegradation by larval metabolism and growth. Detailed information about these larva vermireactors, housefly oviposition, and larva residue separation processes has been reported previously (7,9,10). Field sampling and physicochemical measurements.…”

“…Three replicates of each sample from both the control and treatment collection points were randomly sampled from three different cement block pools. Details of the sampling protocols have been reported previously (10). The pH and temperature of the interior of the manure stockpiles during vermicomposting and/or control composting were recorded on site.…”

“…The internal standard calibration method was used to quantify the analytes (18), and the method detection limit was determined to be 0.5 to 14.1 g kg Ϫ1 for manure samples. The detailed protocols for the antimicrobial analyses can be found in our previous study (10).…”