Genetic Characterization of Escherichia coli O157:H7 Strains Isolated from the One-Humped Camel (Camelus dromedarius) by Using Microarray DNA Technology

Monomer and Oligomer Transition of Zinc Phthalocyanine Is Key for Photobleaching in Photodynamic Therapy

Photodynamic therapy (PDT) is recognized as a powerful method to inactivate cells. However, the photosensitizer (PS), a key component of PDT, has suffered from undesired photobleaching. Photobleaching reduces reactive oxygen species (ROS) yields, leading to the compromise of and even the loss of the photodynamic effect of the PS. Therefore, much effort has been devoted to minimizing photobleaching in order to ensure that there is no loss of photodynamic efficacy. Here, we report that a type of PS aggregate showed neither photobleaching nor photodynamic action. Upon direct contact with bacteria, the PS aggregate was found to fall apart into PS monomers and thus possessed photodynamic inactivation against bacteria. Interestingly, the disassembly of the bound PS aggregate in the presence of bacteria was intensified by illumination, generating more PS monomers and leading to an enhanced antibacterial photodynamic effect. This demonstrated that on a bacterial surface, the PS aggregate photo-inactivated bacteria via PS monomer during irradiation, where the photodynamic efficiency was retained without photobleaching. Further mechanistic studies showed that PS monomers disrupted bacterial membranes and affected the expression of genes related to cell wall synthesis, bacterial membrane integrity, and oxidative stress. The results obtained here are applicable to other types of PSs in PDT.

An efficient metal-organic framework-based drug delivery platform for synergistic antibacterial activity and osteogenesis

Bone implants for clinical application should be endowed with antibacterial activity, biocompatibility, and even osteogenesis-promoting properties. In this work, metal-organic framework (MOF) based drug delivery platform was used to modify titanium implants for improved clinical applicability. Methyl Vanillate@Zeolitic Imidazolate Framework-8 (MV@ZIF-8) was immobilized on the polydopamine (PDA) modified titanium. The sustainable release of the Zn²⁺ and MV causes substantial oxidative damage to Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The increased reactive oxygen species (ROS) significantly up-regulates the expression of oxidative stress and DNA damage response genes. Meanwhile, the structural disruption of lipid membranes caused by the ROS, the damage caused by Zinc active sites and the damage accelerated by the MV are both involved in inhibiting bacterial proliferation. The up-regulated expression of the osteogenic-related genes and proteins indicated that the MV@ZIF-8 could effectively promote the osteogenic differentiation of the human bone mesenchymal stem cells (hBMSCs). RNA sequencing and Western blotting analysis revealed that the MV@ZIF-8 coating activates the canonical Wnt/β-catenin signaling pathway through the regulation of tumor necrosis factor (TNF) pathway, thereby promoting the osteogenic differentiation of the hBMSCs. This work demonstrates a promising application of the MOF-based drug delivery platform in bone tissue engineering.

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.

Characterization and antimicrobial susceptibility of Escherichia coli isolated from healthy farm animals in Tunisia

Healthy animals can constitute a reservoir for Escherichia coli potentially dangerous for humans. Our objectives were to investigate virulence genes in E. coli isolated from healthy animals in southern Tunisia and to determine their resistance to antimicrobials of high importance in humans and animals. 126 fecal samples were collected from healthy animals (cattle, sheep, goats, chicken, camel, bustard and rabbit) and assayed by PCR for virulence genes and by disk diffusion for antimicrobial resistance. STEC were isolated most frequently from goats (27.7%), sheep (20%) and cattle (14.2%). ExPEC prevalence of iucD (41.6%), papC (27.7%), sfa (13.8%), afa8 (13.8%) and iron (72.2%) was highest in camels. Prevalence of the ExPEC associated genes iss and cnf and the EPEC defining gene eae was highest in rabbits (53.3, 13.3, and 53.3%, respectively). The genes defining enterotoxigenic, enteroinvasive and enteroaggregative E. coli were not detected and faeG was found only in camels (5.5%). The most common phylogenetic groups were B1 (54.5%) and B2 (16.6%). Virulence gene profiles varied greatly between animal species. Overall, antimicrobial resistance was not highly prevalent, the highest resistance being observed against tetracycline, 43.9%.

Shiga toxin-producing Escherichia coli (STEC) isolated from fecal samples of African dromedary camels

Shiga toxin-producing Escherichia coli (STEC) cause gastrointestinal illnesses including non-bloody or bloody diarrhoea, haemorrhagic colitis (HC), and the haemolytic uremic syndrome (HUS). To investigate the occurrence of STEC among grazing dromedaries from Kenya, E. coli isolated from fecal matter collected from 163 dromedaries on a large ranch were screened for the presence of stx1 and stx2. STEC strains were isolated and serotyped. Isolates were subjected to PCR for the subtyping of stx genes and for the detection of eae and ehx. In addition, whole genome sequencing (WGS) was carried out to detect further virulence genes and to determine the multilocus sequence types (MLST). Antimicrobial resistance profiles were determined by disk diffusion. STEC was isolated from 20 (12.3%) of the fecal samples. Thereof, nine (45%) isolates were STEC O156:H25, three (15%) isolates typed STEC O43:H2. The remaining isolates occurred as single serotypes or were O non-typeable. Eleven (55%) of the isolates harboured stx2a, nine (45%) eae, and 14 (70%) ehx, respectively. WGS revealed the presence of iss in 16 (80%), subAB in four (20%) and astA in two (10%) of the isolates, Furthermore, espA, tccP, nleA, nleB, tccP, and tir were found exclusively among STEC O156:H25. Eleven different sequence types (ST) were detected. The most prominent was ST300/ST5343, which comprised STEC O156:H25. All STEC isolates were pan susceptible to a panel of 16 antimicrobial agents. Overall, the results indicate that dromedary camels in Kenya may be reservoirs of STEC, including serotypes possessing virulence markers associated to disease in humans, such as STEC O156:H25. STEC in camels may represent a health hazard for humans with close contact to camels or to consumers of camel derived foodstuffs, such as unpasteurised camel milk.

A Review of Zoonotic Pathogens of Dromedary Camels

Dromedary, or one-humped, camels Camelus dromedarius are an almost exclusively domesticated species that are common in arid areas as both beasts of burden and production animals for meat and milk. Currently, there are approximately 30 million dromedary camels, with highest numbers in Africa and the Middle East. The hardiness of camels in arid regions has made humans more dependent on them, especially as a stable protein source. Camels also carry and may transmit disease-causing agents to humans and other animals. The ability for camels to act as a point source or vector for disease is a concern due to increasing human demands for meat, lack of biosafety and biosecurity protocols in many regions, and a growth in the interface with wildlife as camel herds become sympatric with non-domestic species. We conducted a literature review of camel-borne zoonotic diseases and found that the majority of publications (65%) focused on Middle East respiratory syndrome (MERS), brucellosis, Echinococcus granulosus, and Rift Valley fever. The high fatality from MERS outbreaks during 2012-2016 elicited an immediate response from the research community as demonstrated by a surge of MERS-related publications. However, we contend that other camel-borne diseases such as Yersinia pestis, Coxiella burnetii, and Crimean-Congo hemorrhagic fever are just as important to include in surveillance efforts. Camel populations, particularly in sub-Saharan Africa, are increasing exponentially in response to prolonged droughts, and thus, the risk of zoonoses increases as well. In this review, we provide an overview of the major zoonotic diseases present in dromedary camels, their risk to humans, and recommendations to minimize spillover events.

Oral immunization with a plant-derived chimeric protein in mice: Toward the development of a multipotent edible vaccine against E. coli O157: H7 and ETEC

The most bacterial cause of infectious diseases associated with diarrhea are enterotoxigenic and enterohemorrhagic Escherichia coli (ETEC and EHEC, respectively). These strains use colonization factors for the attachment to the human intestinal mucosa, followed by enterotoxins production that could induce more host damage. The Heat-labile enterotoxin (LT) and colonization factors (CFs) are momentous factors for the pathogenesis of ETEC. Also, Intimin and Shiga like toxin (STX) are the main pathogenic factors expressed by EHEC. Because of mucosal surfaces are the major entry site for these pathogens, oral immunization with providing the protective secretary IgA antibody (sIgA) responses in the mucosa, could prevent the bacterial adherence to the intestine. In this study oral immunogenicity of a synthetic recombinant protein containing StxB, Intimin, CfaB and LtB (SICL) was investigated. For specific expression in canola seeds, the optimized gene was cloned in to plant expression vector containing the Fatty Acid Elongase (FAE) promoter. The evaluation of the expression level in canola seeds was approximately 0.4% of total soluble protein (TSP). Following to oral immunization of mice, serum IgG and fecal IgA antibody responses induced. Caco-2 cell binding assay with ETEC shows that the sera from immunized mice could neutralize the attachment properties of toxigenic E. coli. The reduction of bacterial shedding after the challenge of immunized mice with E. coli O157:H7 was significant. The sera from immunized mice in the rabbit ileal loop experiment exhibited a significant decrease in the fluid accumulation compared to the control. The results indicate efficacy of the recombinant chimeric protein SICL in transgenic canola seed as an effective immunogen, which elicits both systemic and mucosal immune responses as well as protection against EHEC and ETEC adherence and toxicity.

DNA Microarray for Rapid Detection and Identification of Food and Water Borne Bacteria: From Dry to Wet Lab

Background:

A rapid, accurate, flexible and reliable diagnostic method may significantly decrease the costs of diagnosis and treatment. Designing an appropriate microarray chip reduces noises and probable biases in the final result.

Objective:

The aim of this study was to design and construct a DNA Microarray Chip for a rapid detection and identification of 10 important bacterial agents.

Method:

In the present survey, 10 unique genomic regions relating to 10 pathogenic bacterial agents including Escherichia coli (E.coli), Shigella boydii, Sh.dysenteriae, Sh.flexneri, Sh.sonnei, Salmonella typhi, S.typhimurium, Brucella sp., Legionella pneumophila, and Vibrio cholera were selected for designing specific long oligo microarray probes. For this reason, the in-silico operations including utilization of the NCBI RefSeq database, Servers of PanSeq and Gview, AlleleID 7.7 and Oligo Analyzer 3.1 was done. On the other hand, the in-vitro part of the study comprised stages of robotic microarray chip probe spotting, bacterial DNAs extraction and DNA labeling, hybridization and microarray chip scanning. In wet lab section, different tools and apparatus such as Nexterion® Slide E, Qarray^mini spotter, NimbleGen kit, TrayMix^TM S4, and Innoscan 710 were used.

Results:

A DNA microarray chip including 10 long oligo microarray probes was designed and constructed for detection and identification of 10 pathogenic bacteria.

Conclusion:

The DNA microarray chip was capable to identify all 10 bacterial agents tested simultaneously. The presence of a professional bioinformatician as a probe designer is needed to design appropriate multifunctional microarray probes to increase the accuracy of the outcomes.

Prevalence of Escherichia coli O157:H7 and Salmonella in camels, cattle, goats, and sheep harvested for meat in Riyadh

Escherichia coli O157:H7 and Salmonella are significant foodborne pathogens that can be found in the feces and on the hides of meat animals. When hides are removed during the harvest process, the carcass and subsequent meat products can become contaminated. Camels, cattle, sheep, and goats are harvested for meat in Riyadh, Saudi Arabia. The prevalence of E. coli O157:H7 and Salmonella are unknown in these animals, and it is assumed that if the animals carry the pathogens in their feces or on their hides, meat products are likely to become contaminated. To this end, a minimum of 206 samples each from hides and feces of camels, cattle, goats, and sheep were collected over the course of 8 months and tested for E. coli O157:H7 and Salmonella. It was found that E. coli O157:H7 was present in feces (10.7, 1.4, 2.4, and 2.4%) and on hides (17.9, 8.2, 2.9, and 9.2%) of cattle, goats, camels, and sheep, respectively. The prevalence of Salmonella was 11.2, 13.5, 23.2, and 18.8% in feces and 80.2, 51.2 67.6, and 60.2% on hides of cattle, goats, camels, and sheep, respectively. The prevalence of E coli O157:H7 was nearly zero in all samples collected in June and July, while Salmonella did not exhibit any seasonal variation. These results constitute the first comprehensive study of E. coli O157:H7 and Salmonella prevalence in Saudi Arabian meat animals at harvest.