Veterinary Research Forum

Abstract The complete mitochondrial genome sequence of Dermacentor marginatus isolated from Hainan Island, a tropical island in China, has recently been elucidated. This ornate sheep tick is a three-host species, meaning it requires feeding on different hosts throughout its larval, nymph, and adult stages. This broad host range contributes significantly to its role in the transmission of various pathogens including spotted fever group rickettsia. The mitochondrial genome of D. marginatus was sequenced and found to be a circular, double-stranded DNA molecule with a total length of 15,005 bp. The genome exhibited a guanine and cytosine (GC) content of 21.23%, reflecting its unique genetic composition. Annotation of the genome revealed the presence of 37 genes, comprising 22 tRNA genes, 13 mRNA genes as protein-coding genes, (PCGs) and two rRNA genes. Phylogenetic analysis placed D. marginatus closest to D. silvarum from Heilongjiang province in China, clustering with D. sinicus from Hubei province in China. D. marginatus also exhibited proximity to D. species from China and other countries forming a distinct cluster. The availability of the complete mitochondrial genome sequence of D. marginatus marked a notable advancement in deciphering the genetic diversity and evolutionary path of this tick species. The study concentrated on the mitochondrial genome of D. marginatus from Hainan Island, examining its genetic and phylogenetic features, and assessing genomic variations that may influence mitochondrial function and tropical adaptation. The investigation into the genetic adaptations of D. marginatus to its tropical niche yielded vital information for forecasting how tick populations may react to changes in climate and diverse environmental conditions.

Abstract This study was conducted to reveal the phylogenetic background, to detect the genes encoding TEM, SHV and CTX-M-15 extended-spectrum β-lactamases (ESBL), and to analyze their distribution in phylo-groups of 150 Escherichia coli isolates from broiler chickens in Ahvaz (Southwest of Iran). Seventy- five cloacal swabs from healthy birds (fecal isolates), and 75 heart blood samples from birds with colibacillosis (septicemic isolates) were obtained. All isolates were phylotyped and screened for ESBL genes by polymerase chain reaction (PCR). The fecal isolates belonged to four main phylo-groups, including 41 isolates (54.67%) to A, 9 (12.00%) to B1, 5 (6.67%) to B2, and 20 (26.67%) to D. Of septicemic isolates, 37 isolates (49.33%) were classified as phylotype A, 5 (6.67%) as B1, 10 (13.33%) as B2, and 23 (30.67%) as D. In molecular analysis, a total of 72 isolates (35 fecal and 37 septicemic) were identified to harbor ESBL genes, which were distributed in phylo-groups A, B1, B2, and D. Regardless of the type of isolate, bla_CTX-M-15 gene was the most common genotype, followed by bla_TEM and bla_SHV genes. This study suggests that broiler chickens in Iran are infected to ESBL genes- harboring Escherichia coli strains which may be spread to the food chain through fecal contamination of carcasses during slaughtering.