The effects of temperature and innate immunity on transmission of Campylobacter jejuni (Campylobacterales: Campylobacteraceae) between life stages of Musca domestica (Diptera: Muscidae)

Pathogens associated with houseflies from different areas within a New York State dairy

Houseflies (Musca domestica) are nonbiting muscoids of importance because they can be mechanical vectors of many kinds of pathogens such as bacteria, protozoa, viruses, and helminth eggs. This study aimed to evaluate the bacterial communities associated with houseflies captured in 3 different areas on a dairy farm located in New York State. Variations in the bacterial community were also evaluated based on the flies' sex and external or internal location where the bacteria were isolated. A total of 101 flies were collected: 27 flies from the sick pen, 42 from calf hutches, and 32 from the milking parlor. A total of 485 organisms were isolated, 233 (48.0%) from 53 female flies and 252 (52.0%) from 48 male flies. Most (74%) bacteria were found in the internal parts of the flies, with only 26% isolated from the external surfaces. The number of isolates detected per fly ranged between 1 and 11. A total of 392 bacteria were identified at the species level. We isolated 26 species reported to be bovine contagious or environmental mastitis pathogens. Within the group of organisms considered contagious, we isolated Staphylococcus aureus and Mycoplasma arginini. This was the first time that a Mycoplasma species was isolated from houseflies. We identified 5 organisms considered foodborne pathogens that affect human health: Salmonella spp., Escherichia coli, Staph. aureus, Bacillus cereus, and Bacillus subtilis. Four of the organisms isolated in this study were also linked with milk spoilage, including Pseudomonas aeruginosa, Bacillus cereus, Bacillus licheniformis, and Paenibacillus lactis. This study confirmed that houseflies carry a high bacterial diversity, including organisms associated with animal infections, organisms that could be a concern for public health, or organisms that could negatively affect milk quality.

Potential bacterial biomarkers for insect colonization in forensic cases: preliminary quantitative data on Wohlfahrtiimonas chitiniclastica and Ignatzschineria indica dynamics

For the last decades, forensic microbiology became an emerging complementary tool in criminalistics. Although the insect-microbe interactions regarding pathogen transmission were extensively studied, only scarce information is available on bacterial transfer from necrophagous insects to host tissues. Our data provides the first report on the occurrence of Wohlfahrtiimonas chitiniclastica and Ignatzschineria indica in Lucilia illustris Meigen, 1826 (Diptera: Calliphoridae), and the quantitative dynamics of the two bacterial species along the insect life-stages and transfer to beef and pork host tissues using qPCR gyrase b specific primers. The content of both bacterial species increased along the insect life stages. W. chitiniclastica was detected in all developmental stages independent of the feeding substrate. I. indica was measurable with 10² gene copies ng⁻¹ DNA threshold starting from the third instar larvae when feeding on beef, and from the egg stage with a 10²× higher representation when using the pork substrate. The transfer of bacterial species to both tissues occurred after 3 colonization days except for I. indica that was visible in beef liver only during day 5. Considering the utilization of pork tissues as human analogues, these quantitative microbial dynamics data provides first insect-specific bacterial candidates as potential colonization biomarkers in forensic investigations.

A systematic review of human pathogens carried by the housefly (Musca domestica L.)

BACKGROUND

The synanthropic house fly, Musca domestica (Diptera: Muscidae), is a mechanical vector of pathogens (bacteria, fungi, viruses, and parasites), some of which cause serious diseases in humans and domestic animals. In the present study, a systematic review was done on the types and prevalence of human pathogens carried by the house fly.

METHODS

Major health-related electronic databases including PubMed, PubMed Central, Google Scholar, and Science Direct were searched (Last update 31/11/2017) for relevant literature on pathogens that have been isolated from the house fly.

RESULTS

Of the 1718 titles produced by bibliographic search, 99 were included in the review. Among the titles included, 69, 15, 3, 4, 1 and 7 described bacterial, fungi, bacteria+fungi, parasites, parasite+bacteria, and viral pathogens, respectively. Most of the house flies were captured in/around human habitation and animal farms. Pathogens were frequently isolated from body surfaces of the flies. Over 130 pathogens, predominantly bacteria (including some serious and life-threatening species) were identified from the house flies. Numerous publications also reported antimicrobial resistant bacteria and fungi isolated from house flies.

CONCLUSIONS

This review showed that house flies carry a large number of pathogens which can cause serious infections in humans and animals. More studies are needed to identify new pathogens carried by the house fly.

Management of Staphylococcus Mediated Systemic Infection by Enhancing the Resurging Activity of Co-trimoxazole in Presence of Cryptdin-2

Resurgence of sensitivity of the antibiotics, to which the pathogen had developed resistance in the past, requires special attention for strengthening the reservoir of antimicrobial compounds. Reports in the recent past have suggested that co-trimoxazole (COT) has regained its activity against methicillin resistant Staphylococcus aureus (MRSA). The present study exploited the use of COT in the presence of an antimicrobial peptide (AMP), cryptdin-2 (a murine Paneth cell alpha defensin), in order to reduce the selective pressure of the antibiotic on the pathogen. In vitro antibacterial activity and in vivo efficacy of the combination was ascertained against MRSA induced systemic infection using a murine model. Observations of the present study might help in restoring the regained activity of conventional antibiotics, such as COT, when used in combination with novel antimicrobial molecules like AMPs. This might prove as a viable strategy to eliminate the chances of re-occurrence of resistance due to their multi-prong targeting and synergistically combating infections caused by these resistant pathogens.

Campylobacter jejuni in Musca domestica: An examination of survival and transmission potential in light of the innate immune responses of the house flies

The house fly, Musca domestica, has been implicated as a vector of Campylobacter spp., a major cause of human disease. Little is known whether house flies serve as biological amplifying hosts or mechanical vectors for Campylobacter jejuni. We investigated the period after C. jejuni had been ingested by house flies in which viable C. jejuni colonies could be isolated from whole bodies, the vomitus and the excreta of adult M. domestica and evaluated the activation of innate immune responses of house flies to ingested C. jejuni over time. C. jejuni could be cultured from infected houseflies soon after ingestion but no countable C. jejuni colonies were observed > 24 h postingestion. We detected viable C. jejuni in house fly vomitus and excreta up to 4 h after ingestion, but no viable bacteria were detected ≥ 8 h. Suppression subtractive hybridization identified pathogen-induced gene expression in the intestinal tracts of adult house flies 4-24 h after ingesting C. jejuni. We measured the expression of immune regulatory (thor, JNK, and spheroide) and effector (cecropin, diptericin, attacin, defensing, and lysozyme) genes in C. jejuni-infected and -uninfected house flies using quantitative real time PCR. Some house fly factor, or combination of factors, eliminates C. jejuni within 24 h postingestion. Because C. jejuni is not amplified within the body of the housefly, this insect likely serves as a mechanical vector rather than as a true biological, amplifying vector for C. jejuni, and adds to our understanding of insect-pathogen interactions.

Genome-wide fitness analyses of the foodborne pathogen Campylobacter jejuni in in vitro and in vivo models

Campylobacter is the most common cause of foodborne bacterial illness worldwide. Faecal contamination of meat, especially chicken, during processing represents a key route of transmission to humans. There is a lack of insight into the mechanisms driving C. jejuni growth and survival within hosts and the environment. Here, we report a detailed analysis of C. jejuni fitness across models reflecting stages in its life cycle. Transposon (Tn) gene-inactivation libraries were generated in three C. jejuni strains and the impact on fitness during chicken colonisation, survival in houseflies and under nutrient-rich and -poor conditions at 4 °C and infection of human gut epithelial cells was assessed by Tn-insertion site sequencing (Tn-seq). A total of 331 homologous gene clusters were essential for fitness during in vitro growth in three C. jejuni strains, revealing that a large part of its genome is dedicated to growth. We report novel C. jejuni factors essential throughout its life cycle. Importantly, we identified genes that fulfil important roles across multiple conditions. Our comprehensive screens showed which flagella elements are essential for growth and which are vital to the interaction with host organisms. Future efforts should focus on how to exploit this knowledge to effectively control infections caused by C. jejuni.

Bacterial Communities Associated with Houseflies (Musca domestica L.) Sampled within and between Farms

The housefly feeds and reproduces in animal manure and decaying organic substances and thus lives in intimate association with various microorganisms including human pathogens. In order to understand the variation and association between bacteria and the housefly, we used 16S rRNA gene amplicon sequencing to describe bacterial communities of 90 individual houseflies collected within and between ten dairy farms in Denmark. Analysis of gene sequences showed that the most abundant classes of bacteria found across all sites included Bacilli, Clostridia, Actinobacteria, Flavobacteria, and all classes of Proteobacteria and at the genus level the most abundant genera included Corynebacterium, Lactobacillus, Staphylococcus, Vagococcus, Weissella, Lactococcus, and Aerococcus. Comparison of the microbiota of houseflies revealed a highly diverse microbiota compared to other insect species and with most variation in species richness and diversity found between individuals, but not locations. Our study is the first in-depth amplicon sequencing study of the housefly microbiota, and collectively shows that the microbiota of single houseflies is highly diverse and differs between individuals likely to reflect the lifestyle of the housefly. We suggest that these results should be taken into account when addressing the transmission of pathogens by the housefly and assessing the vector competence variation under natural conditions.

Routes of Transmission in the Food Chain

More than 250 different foodborne diseases have been described to date, annually affecting about one-third of the world's population. The incidence of foodborne diseases has been underreported and underestimated, and the asymptomatic presentation of some of the illnesses, worldwide heterogeneities in reporting, and the alternative transmission routes of certain pathogens are among the factors that contribute to this. Globalization, centralization of the food supply, transportation of food products progressively farther from their places of origin, and the multitude of steps where contamination may occur have made it increasingly challenging to investigate foodborne and waterborne outbreaks. Certain foodborne pathogens may be transmitted directly from animals to humans, while others are transmitted through vectors, such as insects, or through food handlers, contaminated food products or food-processing surfaces, or transfer from sponges, cloths, or utensils. Additionally, the airborne route may contribute to the transmission of certain foodborne pathogens. Complicating epidemiological investigations, multiple transmission routes have been described for some foodborne pathogens. Two types of transmission barriers, primary and secondary, have been described for foodborne pathogens, each of them providing opportunities for preventing and controlling outbreaks. Primary barriers, the most effective sites of prophylactic intervention, prevent pathogen entry into the environment, while secondary barriers prevent the multiplication and dissemination of pathogens that have already entered the environment. Understanding pathogen dynamics, monitoring transmission, and implementing preventive measures are complicated by the phenomenon of superspreading, which refers to the concept that, at the level of populations, a minority of hosts is responsible for the majority of transmission events.

Engineering the Campylobacter jejuni N-glycan to create an effective chicken vaccine

Campylobacter jejuni is a predominant cause of human gastroenteritis worldwide. Source-attribution studies indicate that chickens are the main reservoir for infection, thus elimination of C. jejuni from poultry would significantly reduce the burden of human disease. We constructed glycoconjugate vaccines combining the conserved C. jejuni N-glycan with a protein carrier, GlycoTag, or fused to the Escherichia coli lipopolysaccharide-core. Vaccination of chickens with the protein-based or E. coli-displayed glycoconjugate showed up to 10-log reduction in C. jejuni colonization and induced N-glycan-specific IgY responses. Moreover, the live E. coli vaccine was cleared prior to C. jejuni challenge and no selection for resistant campylobacter variants was observed. Analyses of the chicken gut communities revealed that the live vaccine did not alter the composition or complexity of the microbiome, thus representing an effective and low-cost strategy to reduce C. jejuni in chickens and its subsequent entry into the food chain.

The Microbiome of Animals: Implications for Conservation Biology

In recent years the human microbiome has become a growing area of research and it is becoming clear that the microbiome of humans plays an important role for human health. Extensive research is now going into cataloging and annotating the functional role of the human microbiome. The ability to explore and describe the microbiome of any species has become possible due to new methods for sequencing. These techniques allow comprehensive surveys of the composition of the microbiome of nonmodel organisms of which relatively little is known. Some attention has been paid to the microbiome of insect species including important vectors of pathogens of human and veterinary importance, agricultural pests, and model species. Together these studies suggest that the microbiome of insects is highly dependent on the environment, species, and populations and affects the fitness of species. These fitness effects can have important implications for the conservation and management of species and populations. Further, these results are important for our understanding of invasion of nonnative species, responses to pathogens, and responses to chemicals and global climate change in the present and future.

Genome-wide characterization and expression profiling of immune genes in the diamondback moth, Plutella xylostella (L.)

The diamondback moth, Plutella xylostella (L.), is a destructive pest that attacks cruciferous crops worldwide. Immune responses are important for interactions between insects and pathogens and information on these underpins the development of strategies for biocontrol-based pest management. Little, however, is known about immune genes and their regulation patterns in P. xylostella. A total of 149 immune-related genes in 20 gene families were identified through comparison of P. xylostella genome with the genomes of other insects. Complete and conserved Toll, IMD and JAK-STAT signaling pathways were found in P. xylostella. Genes involved in pathogen recognition were expanded and more diversified than genes associated with intracellular signal transduction. Gene expression profiles showed that the IMD pathway may regulate expression of antimicrobial peptide (AMP) genes in the midgut, and be related to an observed down-regulation of AMPs in experimental lines of insecticide-resistant P. xylostella. A bacterial feeding study demonstrated that P. xylostella could activate different AMPs in response to bacterial infection. This study has established a framework of comprehensive expression profiles that highlight cues for immune regulation in a major pest. Our work provides a foundation for further studies on the functions of P. xylostella immune genes and mechanisms of innate immunity.