Review--animal waste used as livestock feed: dangers to human health

A Preliminary Study: Antibiotic Resistance Patterns of Escherichia coli and Enterococcus Species from Wildlife Species Subjected to Supplementary Feeding on Various South African Farms

Simple Summary

Supplementary feeding of wildlife allows more opportunity for disease and antibiotic resistant genes to be transferred directly between species due to increased herd density, more frequent direct contact at feeding and water points and increased human contact. The feed itself can also be a direct source of antibiotic compounds and of antibiotic resistant bacteria. This study aimed to determine whether the practice of wildlife supplementary feeding could have an influence on the antibiotic resistance of the bacteria harboured by the supplementary fed wildlife, and thus play a potential role in the dissemination of antibiotic resistance throughout nature. Overall, the E. coli and Enterococcus isolates from the supplementary fed wildlife were found to be more frequently resistant to the selection of antibiotics than from those which were not supplementary fed. Game farmers should be knowledgeable of the ingredients that are used in the game feed that is used to feed both their livestock and wildlife, as certain feed ingredients, such as antibiotics or bone meal, can have a detrimental effect on health and safety. Game farmers should also be aware that farm history can have an impact on the animals which graze on the pastures with regards to antibiotic resistance transfer.

Abstract

Studies have shown that antibiotic resistance among wild animals is becoming a public health concern, owing to increased contact and co-habitation with domestic animals that, in turn, results in increased human contact, indirectly and directly. This type of farming practice intensifies the likelihood of antibiotic resistant traits in microorganisms transferring between ecosystems which are linked via various transfer vectors, such as rivers and birds. This study aimed to determine whether the practice of wildlife supplementary feeding could have an influence on the antibiotic resistance of the bacteria harboured by the supplementary fed wildlife, and thus play a potential role in the dissemination of antibiotic resistance throughout nature. Escherichia coli and Enterococcus were isolated from the faeces of various wildlife species from seven different farms across South Africa. The Kirby-Bauer disk diffusion method was used according to the Clinical and Laboratory Standards Institute 2018 guidelines. The E. coli (F: 57%; N = 75% susceptible) and Enterococcus (F: 67%; N = 78% susceptible) isolates from the supplementary fed (F) wildlife were in general, found to be more frequently resistant to the selection of antibiotics than from those which were not supplementary fed (N), particularly towards tetracycline (E. coli F: 56%; N: 71%/Enterococcus F: 53%; N: 89% susceptible), ampicillin (F: 82%; N = 95% susceptible) and sulphafurazole (F: 68%; N = 98% susceptible). Interestingly, high resistance towards streptomycin was observed in the bacteria from both the supplementary fed (7% susceptible) and non-supplementary fed (6% susceptible) wildlife isolates. No resistance was found towards chloramphenicol and ceftazidime.

Developing control points for halal slaughtering of poultry

Halal (permissible or lawful) poultry meat production must meet industry, economic, and production needs, and government health requirements without compromising the Islamic religious requirements derived from the Qur'an and the Hadiths (the actions and sayings of the Prophet Muhammad, peace and blessings be upon him). Halal certification authorities may vary in their interpretation of these teachings, which leads to differences in halal slaughter requirements. The current study proposes 6 control points (CP) for halal poultry meat production based on the most commonly used halal production systems. CP 1 describes what is allowed and prohibited, such as blood and animal manure, and feed ingredients for halal poultry meat production. CP 2 describes the requirements for humane handling during lairage. CP 3 describes different methods for immobilizing poultry, when immobilization is used, such as water bath stunning. CP 4 describes the importance of intention, details of the halal slaughter, and the equipment permitted. CP 5 and CP 6 describe the requirements after the neck cut has been made such as the time needed before the carcasses can enter the scalding tank, and the potential for meat adulteration with fecal residues and blood. It is important to note that the proposed halal CP program is presented as a starting point for any individual halal certifying body to improve its practices.

Occurrence of Multidrug Resistant Extended Spectrum Beta-Lactamase-Producing Bacteria on Iceberg Lettuce Retailed for Human Consumption

Antibiotic resistance in bacteria is a global problem exacerbated by the dissemination of resistant bacteria via uncooked food, such as green leafy vegetables. New strains of bacteria are emerging on a daily basis with novel expanded antibiotic resistance profiles. In this pilot study, we examined the occurrence of antibiotic resistant bacteria against five classes of antibiotics on iceberg lettuce retailed in local convenience stores in Rochester, Michigan. In this study, 138 morphologically distinct bacterial colonies from 9 iceberg lettuce samples were randomly picked and tested for antibiotic resistance. Among these isolates, the vast majority (86%) demonstrated resistance to cefotaxime, and among the resistant bacteria, the majority showed multiple drug resistance, particularly against cefotaxime, chloramphenicol, and tetracycline. Three bacterial isolates (2.17%) out of 138 were extended spectrum beta-lactamase (ESBL) producers. Two ESBL producers (T1 and T5) were identified as Klebsiella pneumoniae, an opportunistic pathogen with transferable sulfhydryl variable- (SHV-) and TEM-type ESBLs, respectively. The DNA sequence analysis of the bla SHV detected in K. pneumoniae isolate T1 revealed 99% relatedness to bla SHV genes found in clinical isolates. This implies that iceberg lettuce is a potential reservoir of newly emerging and evolving antibiotic resistant bacteria and its consumption poses serious threat to human health.

Determining thermal inactivation of Escherichia coli O157:H7 in fresh compost by simulating early phases of the composting process

A three-strain mixture of Escherichia coli O157:H7 was inoculated into fresh dairy compost (ca. 10(7) CFU/g) with 40 or 50% moisture and was placed in an environmental chamber (ca. 70% humidity) that was programmed to ramp from room temperature to selected composting temperatures in 2 and 5 days to simulate the early composting phase. The surviving E. coli O157:H7 population was analyzed by direct plating and enrichment. Optimal and suboptimal compost mixes, with carbon/nitrogen (C/N) ratios of 25:1 and 16:1, respectively, were compared in this study. In the optimal compost mix, E. coli O157:H7 survived for 72, 48, and 24 h in compost with 40% moisture and for 72, 24, and 24 h with 50% moisture at 50, 55, and 60°C, respectively, following 2 days of come-up time (rate of heating up). However, in the suboptimal compost mix, the pathogen survived for 288, 72, and 48 h in compost with 40% moisture and for 240, 72, 24 h in compost with 50% moisture at the same temperatures, respectively. Pathogen survival was longer, with 5 days of come-up time compared with 2 days of come-up. Overall, E. coli O157:H7 was inactivated faster in the compost with 50% moisture than in the compost with 40% at 55 and 60°C. Both moisture and come-up time were significant factors affecting Weibull model parameters. Our results suggest that slow come-up time at the beginning of composting can extend pathogen survival during composting. Additionally, both the C/N ratio and the initial moisture level in the compost mix affect the rate of pathogen inactivation as well.

Thermal inactivation of heat-shocked Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in dairy compost

Thermal resistance of heat-shocked Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes was compared with that of non-heat-shocked (control) strains in finished dairy compost. A three-strain mixture of each pathogen was heat shocked at 47.5°C for 1 h and inoculated into the compost at a final concentration of 10(7) CFU/g. The inoculated compost was placed inside an environmental chamber set at 50, 55, or 60°C with humidity at ca. 70%. The heat-shocked E. coli O157:H7, Salmonella, and L. monocytogenes survived better (P < 0.05) at 50°C, with reductions of 2.7, 3.2, and 3.9 log CFU/g within 4 h compared with reductions of 3.6, 4.5, and 5.1 log CFU/g, respectively, in control cultures. The heat-shocked cultures of E. coli O157:H7, Salmonella, and L. monocytogenes had 1.2-, 1.9-, and 2.3-log reductions, respectively, within 1 h at 55°C, whereas the corresponding control cultures had 4-, 5.6-, and 4.8-log reductions, respectively. At 60°C, a rapid population reduction was observed during the come-up time of 14 min in control cultures of E. coli O157:H7, Salmonella, and L. monocytogenes with 4.9-, 4.8-, and 2.3-log reductions, respectively, compared with 2.6-, 2.4-, 1.7-log reductions, respectively, in heat-shocked cultures. L. monocytogenes survival curves for all three temperatures had extensive tailing. The double Weibull distribution model was a good fit for the survival curves of pathogens, with differences in the shape parameter of heat-shocked and control cultures. Our results suggest that the heat-shocked pathogens may have extended survival at lethal temperatures attained during the composting process.

High-temperature thermal destruction of poultry derived wastes for energy recovery in Australia

The high-temperature thermal destruction of poultry derived wastes (e.g., manure and bedding) for energy recovery is viable in Australia when considering resource availability and equivalent commercial-scale experience in the UK. In this work, we identified and examined the opportunities and risks associated with common thermal destruction techniques, including: volume of waste, costs, technological risks and environmental impacts. Typical poultry waste streams were characterised based on compositional analysis, thermodynamic equilibrium modelling and non-isothermal thermogravimetric analysis coupled with mass spectrometry (TG-MS). Poultry waste is highly variable but otherwise comparable with other biomass fuels. The major technical and operating challenges are associated with this variability in terms of: moisture content, presence of inorganic species and type of litter. This variability is subject to a range of parameters including: type and age of bird, and geographical and seasonal inconsistencies. There are environmental and health considerations associated with combustion and gasification due to the formation of: NO(X), SO(X), H(2)S and HCl gas. Mitigation of these emissions is achievable through correct plant design and operation, however, with significant economic penalty. Based on our analysis and literature data, we present cost estimates for generic poultry-waste-fired power plants with throughputs of 2 and 8 tonnes/h.

The use of composting for the treatment of animal by-products: Experiments at lab scale

Animal by-products (ABP), containing mainly rabbit and chicken carcasses were composted at laboratory scale. Results indicate that if proper conditions are used, wastes can be successfully composted and stabilised meeting current European hygienisation standards regarding the disposal of this type of wastes. During the process, temperatures above 60 degrees C were easily reached and maintained for 2 days at least, due to the high energy potential of these materials. However, care must be taken to ensure that these temperatures are reached in the entire reactor to guarantee proper hygienisation of the material. These high temperatures may bring about operational problems such as moisture losses due to very high airflows required for their control. Biological activity indices, such as respiration index (RI) and oxygen uptake rate (OUR) used for the monitoring of the process, were able to indicate potential and actual conditions within the composting reactor, respectively.

What do we feed to food-production animals? A review of animal feed ingredients and their potential impacts on human health

OBJECTIVE

Animal feeding practices in the United States have changed considerably over the past century. As large-scale, concentrated production methods have become the predominant model for animal husbandry, animal feeds have been modified to include ingredients ranging from rendered animals and animal waste to antibiotics and organoarsenicals. In this article we review current U.S. animal feeding practices and etiologic agents that have been detected in animal feed. Evidence that current feeding practices may lead to adverse human health impacts is also evaluated.

DATA SOURCES

We reviewed published veterinary and human-health literature regarding animal feeding practices, etiologic agents present in feed, and human health effects along with proceedings from animal feed workshops.

DATA EXTRACTION

Data were extracted from peer-reviewed articles and books identified using PubMed, Agricola, U.S. Department of Agriculture, Food and Drug Administration, and Centers for Disease Control and Prevention databases.

DATA SYNTHESIS

Findings emphasize that current animal feeding practices can result in the presence of bacteria, antibiotic-resistant bacteria, prions, arsenicals, and dioxins in feed and animal-based food products. Despite a range of potential human health impacts that could ensue, there are significant data gaps that prevent comprehensive assessments of human health risks associated with animal feed. Limited data are collected at the federal or state level concerning the amounts of specific ingredients used in animal feed, and there are insufficient surveillance systems to monitor etiologic agents "from farm to fork."

CONCLUSIONS

Increased funding for integrated veterinary and human health surveillance systems and increased collaboration among feed professionals, animal producers, and veterinary and public health officials is necessary to effectively address these issues.

Effect of river landscape on the sediment concentrations of antibiotics and corresponding antibiotic resistance genes (ARG)

The purpose of this study was to quantify antibiotic resistance genes (ARG) in the sediments of the mixed-landscape Cache La Poudre River, which has previously been studied and shown to have high concentrations of antibiotics related to urban and agricultural activities. River sediments were sampled during two events (high-flow and low-flow) from five sites with varying urban and agricultural impact levels. Polymerase-chain-reaction (PCR) detection assays were conducted for four sulfonamide resistance gene families, using newly designed primers, and five tetracycline resistance gene families, using previously published primers. Sul(I), sul(II), tet(W), and tet(O) gene families were further quantified by real-time quantitative polymerase chain reaction (Q-PCR). Resistance to four classes of antibiotics (tetracyclines, sulfonamides, ionophores, and macrolides) was also investigated using a culture-based approach. The quantities of resistance genes normalized to the 16S gene copy number were significantly different between the sites, with higher resistance gene concentrations at the impacted sites than at the pristine site. Total resistant CFUs were over an order of magnitude lower at the pristine site, but differences were less apparent when normalized to the total CFUs. Six tetracyclines and six sulfonamides were also quantified in the sediments and were found to be highest at sites impacted by urban and agricultural activity, with no antibiotics detected at the pristine sit. To the knowledge of the authors, this study is the first to demonstrate a relationship between urban and agricultural activity and microbial resistance in river sediments using quantitative molecular tools.

Long-term survival of pathogenic and sanitation indicator bacteria in experimental biowaste composts

For economic, agricultural, and environmental reasons, composting is frequently used for organic waste recycling. One approach to limiting the potential risk from bacterial food-borne illnesses is to ensure that soil amendments and organic fertilizers are disinfected. However, more knowledge concerning the microbiological safety of composted substrates other than sludge and manure is necessary. Experimental in-vessel biowaste composts were used to study the survival of seeded Listeria monocytogenes, Salmonella enterica subsp. enterica serotype Enteritidis, and Escherichia coli. Four organic waste mixtures, containing various proportions of paper and cardboard, fruits and vegetables, and green waste, were composted in laboratory reactors with forced aeration. The physicochemical and microbiological parameters were monitored for 12 weeks during composting. The survival of bacteria over a 3-month period at 25 degrees C was assessed with samples collected after different experimental composting times. Strain survival was also monitored in mature sterilized composts. Nonsterile composts did not support pathogen growth, but survival of seeded pathogens was observed. Salmonella serovar Enteritidis survived in all composts, and longer survival (3 months) was observed in mature composts (8 and 12 weeks of composting). Mature biowaste composts may support long-term survival of Salmonella serovar Enteritidis during storage at room temperature. E. coli and L. monocytogenes survival was observed only in 4-week-old composts and never in older composts. Proper composting may prevent long-term survival of E. coli and L. monocytogenes. These results suggest that like composted sewage sludge or manure, domestic waste composts may support pathogen survival. Survival was not related to the physicochemical characteristics of the composts.

Presence of Enterococcus faecalis in broiler litter and wild bird feces for bacterial source tracking

When Enterococcus faecalis is isolated from fresh feces, its host range appears to be limited to humans and birds. Although E. faecalis is found in human sewage, the extent to which the bacterium is found in broiler litter and in the feces of wild birds is unclear. These results have implications for bacterial source tracking. We determined if media designed for the isolation of fecal enterococci affected this host range, and if E. faecalis was routinely found in broiler litter and in the feces of wild birds. Of five different isolation media, none affected the isolation of E. faecalis. Enterococcus faecalis was routinely found in fresh broiler feces (522 of 1092 isolates; 48%), but rarely in broiler litter (12 of 1452 isolates; <2%). Therefore, broiler litter selects against this bacterium, and broiler litter is an unlikely environmental source of this bacterium. The presence of E. faecalis in eight wild bird species was highly variable. Unless the fecal loading rate from migratory or resident wild birds is high, water samples collected during baseflow conditions with high numbers of E. faecalis may indicate human fecal contamination.

Anaerobic digestion of organic solid poultry slaughterhouse waste--a review

This work reviews the potential of anaerobic digestion for material recovery and energy production from poultry slaughtering by-products and wastes. First, we describe and quantify organic solid by-products and wastes produced in poultry farming and poultry slaughterhouses and discuss their recovery and disposal options. Then we review certain fundamental aspects of anaerobic digestion considered important for the digestion of solid slaughterhouse wastes. Finally, we present an overview of the future potential and current experience of the anaerobic digestion treatment of these materials.

Occurrence and diversity of tetracycline resistance genes in lagoons and groundwater underlying two swine production facilities

In this study, we used PCR typing methods to assess the presence of tetracycline resistance determinants conferring ribosomal protection in waste lagoons and in groundwater underlying two swine farms. All eight classes of genes encoding this mechanism of resistance [tet(O), tet(Q), tet(W), tet(M), tetB(P), tet(S), tet(T), and otrA] were found in total DNA extracted from water of two lagoons. These determinants were found to be seeping into the underlying groundwater and could be detected as far as 250 m downstream from the lagoons. The identities and origin of these genes in groundwater were confirmed by PCR-denaturing gradient gel electrophoresis and sequence analyses. Tetracycline-resistant bacterial isolates from groundwater harbored the tet(M) gene, which was not predominant in the environmental samples and was identical to tet(M) from the lagoons. The presence of this gene in some typical soil inhabitants suggests that the vector of antibiotic resistance gene dissemination is not limited to strains of gastrointestinal origin carrying the gene but can be mobilized into the indigenous soil microbiota. This study demonstrated that tet genes occur in the environment as a direct result of agriculture and suggested that groundwater may be a potential source of antibiotic resistance in the food chain.

Recombinant chicken IFN-gamma expressed in Escherichia coli: analysis of C-terminal truncation and effect on biologic activity

Interferon-gamma (IFN-gamma) possesses potent immunostimulatory properties, and it has recently been shown to have potential therapeutic properties. Recombinant protein technology is frequently used for commercial production of therapeutics, such as IFN. Biologically active recombinant chicken IFN-gamma (rChIFN-gamma) constructs bearing an N-terminal poly-His tag were expressed in Escherichia coli. Preparations of rChIFN-gamma contained varying ratios of a full-length and a truncated protein species (18 and 16 kDa, respectively). Amino acid sequence analysis of the full-length protein corroborated the sequence previously predicted from the cDNA sequence. Full-length rChIFN-gamma contains two cysteine residues at the C-terminus, and these were labeled by reduction and subsequent specific alkylation with fluorescent tag (5-I-AEDANS) to distinguish between full-length and C-terminally truncated forms of rChIFN-gamma. Comparative peptide mapping, amino acid sequencing, and mass spectrometry revealed that the 16 kDa protein was truncated at Lys133. It was also observed that the 18 kDa rChIFN-gamma protein was infrequently contaminated with small quantities of protein truncated at Arg141. A truncated recombinant construct (His1-Lys133) was also expressed in E. coli and had biologic activity comparable with that of the full-length construct. The 3-D structure of rChIFN-gamma was deduced by comparative modeling with bovine and human IFN-gamma crystallographic structures. Analysis of sequences and comparison of structures have revealed that the 3-D structure of rChIFN-gamma is similar to those of bovine and human molecules despite an overall amino acid identity of only 32%.