Development of a bispecific Nanobody anti-F17 fimbria as a potential therapeutic tool.

Pathogenic strains of Escherichia coli F17+ are associated with various intestinal and extra-intestinal pathologies, including diarrhea, and result in significant animal mortality. These infections rely on the expression of virulence factors, such as F17 fimbriae, for adhesion. F17 fimbriae form a protective layer on the surface of E. coli bacteria, consisting of a major structural subunit, F17A, and a minor functional subunit, F17G. Because of the evolution of bacterial resistance, conventional antibiotic treatments have limited efficacy. Therefore, there is a pressing need to develop novel therapeutic tools. In this study, we cloned and produced the F17G protein. We then immunized a camel with the purified F17G protein and constructed a VHH library consisting of 2 × 109 clones. The library was then screened against F17G protein using phage display technology. Through this process, we identified an anti-F17G nanobody that was subsequently linked, via a linker, to an anti-F17A nanobody, resulting in the creation of an effective bispecific nanobody. Comprehensive characterization of this bispecific nanobody demonstrated excellent production, specific binding capacity to both recombinant forms of the two F17 antigens and the E. coli F17+ strain, remarkable stability in camel serum, and superior resistance to pepsin protease. The successful generation of this bispecific nanobody with excellent production, specific binding capacity and stability highlights its potential as a valuable tool for fighting infections caused by pathogenic E. coli F17+ strain.

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%.

Factors affecting the milk yield and composition over lactation of prolific D'man ewes in Tunisian oases.

This work aimed to investigate milk potentiality and the influence of some non-genetic factors both on milk yield production and composition in prolific D'man sheep. Observations were performed in eighty lactating D'man ewes maintained under an intensive oases system in Southern Tunisia. Daily milk yield was determined at 7-day intervals using oxytocin + hand milking method. Chemical milk composition was determined by Lactoscan. Total productions over lactation (milk, fat, and protein) were estimated using the Fleischmann method. Daily milk yield averaged 1.64 ± 0.02 l. It increased to a plateau from the third to the fourth week of lactation, and decreased gradually to the tenth week. D'man ewes produced 128.91 ± 3.14 l of milk, 9.23 ± 0.26 kg of fat, and 5.26 ± 0.12 kg of total proteins. Overall, milk contained 16.17% of total solids, 7.08% of fat, 4.04% of proteins, 4.32% of lactose, 9.09% of solids-not-fat, and 0.73% of ash. Lambing season affected the daily milk yield and milk composition, where fat and total proteins were highest in autumn. Total solids, lactose, solids-not-fat, and ash were higher in winter than in autumn and summer. Ewes reared multiple lambs produced more milk than those reared singles. Dams nursing triplets or more had the highest milk total proteins, and the lowest total solids and fat levels. Adult ewes produced more milk compared to younger and older ewes, and their milk contained higher total solids, fat, and ash levels than milk from young ewes. Ewes with asymmetric udder produced less and more concentrated milk than ewes with symmetrical udder. Daily milk yield was negatively correlated to total solids, fat, and total proteins amounts. In contrast, litter survival at weaning was positively correlated to the amounts of total milk, fat, and total proteins.

Passive transfer of maternal immunity in the dromedary (Camelus dromedarius), involvement of heavy chain antibodies.

In many mammalian species, newborns are agammaglobulinemic; thus, colostrum and milk are the main sources of early protective antibodies. These antibodies are produced in the mother's serum and transferred to mammalian glands a few days before parturition. Here, we have studied the transfer of immunity from a she-camel immunized with human serum albumin (HSA) to her calf via colostrum and milk. Our results show that HSA-specific antibodies are produced in the mother's serum and are subsequently transferred to her colostrum. These specific antibodies are then transferred by suckling to the calf. The calf serum did not contain HSA-reactive antibodies at parturition and before the first feed, after suckling, a rise in reactivity was observed peaking at 24 h postpartum. The involvement of heavy chain antibodies (HCAbs) in the process of immunity transfer was also examined, and it was found that they were also transferred from the colostrum to the calf serum like conventional antibodies.

A survey of chemical and nutritional characteristics of halophytes plants used by camels in Southern Tunisia.

The camel (Camelus dromedarius) is well adapted to the utilization of vegetation of low nutritional value in its natural habitat zone, thanks to its aptitude to vary food and to search plants that are rich in water content and that can make up for its nutritional deficits, particularly as concerns mineral elements. Therefore, a survey was carried out to determine camels pasture quality, dietary preference and to characterize the chemical characteristics and nutritional value of different halophytes plants in a region of Southern Tunisia during spring season. Laboratory analysis were conducted on fourteen vegetable species appertained to seven different botanical families: Chenopodiaceae, Graminaceae, Tamaricaceae, Zygophyllaceae, Asteraceae, Frankeniaceae and Plumbaginaceae. Data obtained indicate an high variability of nutritional content of halophytes plants preferred by camels, specially for dry matter, crude protein, fiber fractions, ash and mineral elements.