The role of Musca domestica and milk in transmitting pathogenic multidrug-resistant Escherichia coli and associated phylogroups to neonatal calves

Escherichia coli, as a global source of antimicrobial resistance, is a serious veterinary and public health concern. The transmission of pathogenic multidrug-resistant (MDR) E. coli within diarrheic calves and its correlation with Musca domestica and milk strains have been investigated. In total, 110, 80, and 26 E. coli strains were obtained from 70 rectal swabs from diarrheic calves, 60 milk samples and 20 M. domestica, respectively. Molecular pathotyping of E. coli revealed the presence of pathogenic E. coli with a higher percentage of shigatoxigenic strains within diarrheic calves and M. domestica at 46.4% and 34.6%, respectively. Phenotypic antimicrobial resistance revealed higher β-lactams resistance except for cefquinome that exhibited low resistance in M.domestica and milk strains at 30.8% and 30%, respectively. The extended-spectrum cephalosporin (ESC) resistant strains were detected within fecal, M. domestica, and milk strains at 69.1%, 73.1%, and 71.3%, respectively. All E. coli strains isolated from M. domestica exhibited MDR, while fecal and milk strains were harboring MDR at 99.1% and 85%, respectively. Molecular detection of resistant genes revealed the predominance of the bla_TEM gene, while none of these strains harbored the bla_OXA gene. The highest percentages for bla_CTXM and bla_CMYII genes were detected in M. domestica strains at 53.8% and 61.5%, respectively. Regarding colistin resistance, the mcr-1 gene was detected only in fecal and milk strains at 35.5% and 15%, respectively. A high frequency of phylogroup B2 was detected within fecal and M. domestica strains, while milk strains were mainly assigned to the B1 phylogroup. Pathogenic E. coli strains with the same phenotypic and genotypic antimicrobial resistance and phylogroups were identified for both diarrheic calves and M. domestica, suggesting that the possible role of M. domestica in disseminating pathogenic strains and antimicrobial resistance in dairy farms.

Antimicrobial functional divergence of the cecropin antibacterial peptide gene family in Musca domestica

BACKGROUND

It has been reported that there are more than ten antimicrobial peptides (AMPs) belonging to the cecropin family in Musca domestica; however, few of them have been identified, and the functions of the other molecules are poorly understood.

METHODS

Sequences of the M. domestica cecropin family of genes were cloned from cDNA template, which was reverse-transcribed from total mRNA isolated from third-instar larvae of M. domestica that were challenged with pathogens. Sequence analysis was performed using DNAMAN comprehensive analysis software, and a molecular phylogenetic tree of the cecropin family was constructed using the Neighbour-Joining method in MEGA v.5.0 according to the mature peptide sequences. Antibacterial activity of the synthetic M. domestica cecropin protein was detected and the minimum inhibitory concentration (MIC) values were determined using broth microdilution techniques. Time-killing assays were performed on the Gram-negative bacteria, Acinetobacter baumannii, at the logarithmic or stabilizing stages of growth, and its morphological changes when treated with Cec4 were assessed by scanning electron microscopy (SEM) and detection of leakage of 260 nm absorbing material.

RESULTS

Eleven cecropin family genes, namely Cec01, Cec02 and Cec1-9, show homology to the Cec form in a multigene family on the Scaffold18749 of M. domestica. In comparing the encoded cecropin protein sequences, most of them have the basic characteristics of the cecropin family, containing 19 conservative amino acid residues. To our knowledge, this is the first experimental demonstration that most genes in the Cec family are functional. Cec02, Cec1, Cec2, Cec5 and Cec7 have similar antibacterial spectra and antibacterial effects against Gram-negative bacteria, while Cec4 displays a more broad-spectrum of antimicrobial activity and has a very strong effect on A. baumannii. Cec4 eliminated A. baumannii in a rapid and concentration-dependent manner, with antibacterial effects within 24 h at 1× MIC and 2× MIC. Furthermore, SEM analysis and the leakage of 260 nm absorbing material detection indicated that Cec4 sterilized the bacteria through the disruption of cell membrane integrity.

CONCLUSIONS

Although there are more than ten cecropin genes related to M. domestica, some of them have no preferred antibacterial activity other than Cec4 against A. baumannii.

Efficacy of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) on developmental stages of house fly, Musca domestica

The housefly, Musca domestica is a major domestic, medical and veterinary pest. The management of these flies reliance on insecticide, causes environmental constraints, insecticide resistance and residues in the meat, skin. Therefore one of the eco-friendly alternate methods is by using biological agents such as entomopathogenic nematodes (EPN). In the present study evaluated the survival of EPN species Steinernema feltiae, Heterorhabditis indica, S. carpocapsae, S. glaseri and S. abbasi in poultry manure and also their efficacy against different developmental stages of house fly. After exposing to poultry manure, S. feltiae showed more survival as followed by H. indica, S. carpocapsae, S. glaseri and S. abbasi in all exposition period. When the exposition period extended to 96 h, all nematode species survivability was drastically reduced. After exposing these nematodes to poultry manure at 24 h their virulence capacity against wax moth, Galleria mellonella showed all the nematode species were able cause 100% mortality. However their progeny production was significantly reduced. Fly eggs and pupae were refractory to these nematode infection. Petri dish without artificial diet assay showed that, second and 3rd-instar larvae were highly susceptible to EPNs as compared to larvae provided with artificial diet. H. indica showed high virulence capacity compared to other nematodes tested. Poultry manure assay revealed that, H. indica and S. carpocapsae caused minimal mortality where as S. feltiae, S. glaseri and S. abbasi did not cause any mortality. This may be because of poor survival and limited movement of nematodes in poultry manure which may be due to ammonia, other toxic substances in poultry manure. The decrease in larval mortality in manure suggests that biocontrol of housefly by using EPNs is unlikely.

Redox homeostasis and reactive oxygen species scavengers shift during ontogenetic phase changes in apple

The change from juvenile to adult phase is a universal phenomenon in perennial plants such as apple. To validate the changes in hydrogen peroxide (H2O2) levels and scavenging during ontogenesis in apple seedlings, the H2O2 contents, its scavenging capacity, and the expression of related genes, as well as miR156 levels, were measured in leaf samples from different nodes in seedlings of 'Zisai Pearl' (Malus asiatica)×'Red Fuji' (M. domestica). Then in vitro shoots were treated with redox modulating chemicals to verify the response of miR156 to redox alteration. The expression of miR156 decreased gradually during ontogenesis, indicating a progressive loss of juvenility. During the phase changes, H2O2 and ascorbate contents, the ratio of ascorbate to dehydroascorbate, the ascorbate peroxidase, catalase and glutathione reductase activities, and the expressions of some MdGR and MdAPX gene family members increased remarkably. However, the glutathione content and glutathione to glutathione disulfide ratio declined. In chemicals treated in vitro shoots, the changes in miR156 levels were coordinated with GSH contents and GSH/GSSG ratio but not H2O2 contents. Conclusively, the relative reductive thiol redox status is critical for the maintenance of juvenility and the reductive ascorbate redox environment was elevated and sustained during the reproductive phase.

Rapid discrimination of maggots utilising ATR-FTIR spectroscopy

Entomological evidence is used in forensic investigations to indicate time since death. The species and age of maggots or flies that are present at the scene can be used when estimating how much time has passed since death. Current methods that are used to identify species and developmental stage of larvae and fly samples are highly subjective, costly and often time consuming processes and require the expertise of an entomologist or species identification via DNA analysis. The use of vibrational spectroscopy, as an alternative identification method, would allow for a quicker, cheaper and less subjective technique and would allow entomological evidence to be used more commonly in the forensic process. This proof of principle study shows the potential for using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) as a rapid tool for differentiating between various species of larvae, such as those commonly found at crime scenes. The proposed regime would provide a rapid and valuable tool resulting in reduced time for both species identification and life cycle determination, particularly in forensic situations.

Comparative gene expression analysis of Dtg, a novel target gene of Dpp signaling pathway in the early Drosophila melanogaster embryo

In the early Drosophila melanogaster embryo, Dpp, a secreted molecule that belongs to the TGF-β superfamily of growth factors, activates a set of downstream genes to subdivide the dorsal region into amnioserosa and dorsal epidermis. Here, we examined the expression pattern and transcriptional regulation of Dtg, a new target gene of Dpp signaling pathway that is required for proper amnioserosa differentiation. We showed that the expression of Dtg was controlled by Dpp and characterized a 524-bp enhancer that mediated expression in the dorsal midline, as well as, in the differentiated amnioserosa in transgenic reporter embryos. This enhancer contained a highly conserved region of 48-bp in which bioinformatic predictions and in vitro assays identified three Mad binding motifs. Mutational analysis revealed that these three motifs were necessary for proper expression of a reporter gene in transgenic embryos, suggesting that short and highly conserved genomic sequences may be indicative of functional regulatory regions in D. melanogaster genes. Dtg orthologs were not detected in basal lineages of Dipterans, which unlike D. melanogaster develop two extra-embryonic membranes, amnion and serosa, nevertheless Dtg orthologs were identified in the transcriptome of Musca domestica, in which dorsal ectoderm patterning leads to the formation of a single extra-embryonic membrane. These results suggest that Dtg was recruited as a new component of the network that controls dorsal ectoderm patterning in the lineage leading to higher Cyclorrhaphan flies, such as D. melanogaster and M. domestica.