Molecular characterization, genetic diversity and antibacterial susceptibility of Escherichia coli encoding Shiga toxin 2f in domestic pigeons.

This study aimed to evaluate prevalence, characteristics, genotypic diversity and antibacterial susceptibility of Escherichia coli encoding Shiga toxin 2f in domestic pigeons in different provinces of Iran. A total of 117 faecal samples were collected from pigeons and were subjected to molecular detection of stx2f. In total, 20, 25·8, 21·4 and 9% of pigeons from Tehran, Ferdows, Garmsar and Babol cities carried stx2f+ isolates, respectively. Of the 460 E. coli isolates examined, 43 were stx2f+ and most also carried eae (95·3%) and astA (97·7%) genes. Some of the stx2f+ isolates harboured cnf (9·3%), but all were negative for stx1, stx2 (other subtypes) and ehly. Most Strains (90%) were assigned to B1 phylogroup and possessed Intimin-ß. Fingerprinting of the stx2f+ isolates using either enterobacterial repetitive intergenic consensus sequences (ERIC) or random amplified polymorphic DNA (RAPD)-polymerase chain reaction revealed seven distinct profiles by each method, with one prevailing (65·1 and 46·5%, respectively). By the combination of methods, 10 profiles were recognized. Ten isolates from different profiles were shown to belong to O20, O78 and O115 serogroups, and eight were 100% identical in the stx2f gene sequence. The strains were consistently resistant to amoxicillin and lincospectin and commonly resistant to tetracycline (88·4%) and doxycycline (74·4%). Overall, the results indicate a limited degree of genetic diversity in stx2f-harbouring E. coli from pigeons. Significance and impact of the study: Carriage of stx2f gene tends to be underreported in pigeon Escherichia coli isolates because most routine genetic and phenotypic tests cannot efficiently target this gene or detect the toxin. Nevertheless, pigeons frequently carry E. coli strains that are stx2f-positive, and this situation is not limited to any distinct geographical area. The current results suggest that genetic background of stx2f-encoding E. coli is distinct from most Shiga toxin-producing E. coli strains. However, the factors that contribute to host preferences and pathogenicity remain unclear. These findings have public health significance that should be addressed in future research.

Diagnosis of Mesobuthus eupeus envenomation by skin test: reverse passive Arthus reaction.

While being stung by two large families of scorpions, Buthidae and Scorpionidae have different symptoms and complications, a similar maintenance treatment usually considers as the scorpion species could not be identified easily. Therefore, this study was an attempt to develop an immunologic response for designing a skin sensitivity test that can be used to determine the poisoning. The sensitivity and the specificity of RPA reaction for detecting experimental envenomated mice were evaluated. The inflammatory response for detection of envenomation was obtained by the injection of a solution containing complement, polyelectrolytes and purified monovalent antibodies. As the result, 84.44% sensitivity and 100% specificity recorded 15 min after challenge. Macroscopic findings were also confirmed histologically. No cross-reactions were observed with other species of scorpions and snake venoms. Designed Skin test induced obvious inflammatory reaction without any histological lesions. Besides adding the complement components and polyelectrolyte to the monovalent antibody leads to an increased susceptibility of inflammatory cells in this reaction, resulting in forming a visible inflammation in a short time. According to satisfactory specificity and sensitivity and visible results in about 15 min, non-harmful and cost benefity of reverse passive Arthus test can be used for diagnosis of scorpion envenomation.

The production of monovalent and anti-idiotype antivenom against Mesobuthus eupeus (Scorpionida: Buthidae) venom in rabbits.

The antivenom production against poisonous creatures encounters a number of difficulties. Interestingly, according to the network theory the conventional antigens are not necessarily needed for producing antibodies against the venoms. In this investigation, the antivenom against Mesobuthus eupeus venom was produced based on the aforementioned theory. Polyclonal antibodies against M. eupeus venom were obtained from the immunized rabbits and the specific antibodies were isolated. After separation of Fab2, immunization process and production of the monovalent and anti-idiotype, these antivenoms were analyzed for the determination of their neutralizing power. The level of the produced antibodies in different stages of this study was also measured by ELISA assay. Four hundred and fifty micrograms of the venom can be neutralized by 4.2, 18 and 291 mg of monovalent, polyvalent and anti-idiotype antivenom, respectively. The ELISA results revealed that idiotypic antigens were six times more immunogenic than anti-idiotypes. The anti-idiotype antivenom can be produced on a large scale with minimum venom consumption. In addition, they are non-toxicant in immunized animals and can be used as a vaccine in people at the risk of scorpion stings.