Abstract
Gallibacterium anatis is a common cause of reproductive tract infection in chickens, which leads to reduced egg production and increased mortality. This study was undertaken to investigate prevalence of G. anatis in 12 poultry flocks originating from Iranian provinces with leading chicken production and to determine genetic diversity, antimicrobial resistance, and the presence of major antigens of the isolates investigated. Out of the 120 chicken tracheal samples collected and tested, 84 (70%) were positive for G. anatis. Genotyping by Pulse Field Gel Electrophoresis and genome sequencing revealed a total of 24 pulsotypes for 71 strains (at a 87% similarity level) and seven genome clusters comprising 21 strains (97% similarity level), respectively. The combination of the two typing methods confirmed the presence of several genotypes originating from a common ancestor affecting poultry yet also suggested that identical clones were shared among chickens within farms and between different farms. The latter finding is to our knowledge the first example of clonal presence of G. anatis in epidemiologically unrelated farms. The 21 sequenced strains were characterized against a panel of commonly used antibiotics and showed lowered sensitivity to tetracycline (76.2%) and enrofloxacin (90.5%). The widespread presence of multiresistant G. anatis isolates calls for non-antibiotic prophylactics. Three major immunogen genes, gtxA, Gab_1309 and Gab_2312 were detected in the isolates indicating these antigens likely represent effective vaccine targets. A conserved sequence of the gtxA gene across a range of epidemiologically independent strains suggests the use of GtxA for future vaccine development purposes.
Highlights
The human consumption of poultry meat and eggs has increased rapidly during the past century in Europe and the USA, and in developing countries [1]
GtxA is composed of two domains, a C-terminal is responsible for hemolytic function and a N-terminal domain required for complete hemolytic activity [13]
Isolation and identification of G. anatis from chicken production systems in Iran Culture‐based identification Among the 120 samples tested by culture-based identification, 84 samples showed positive growth of bacteria with a G. anatis-suspect colony morphology and strong beta-hemolysis
Summary
The human consumption of poultry meat and eggs has increased rapidly during the past century in Europe and the USA, and in developing countries [1]. Three types of chicken enterprises including broiler and Gallibacterium anatis is distributed globally as an important opportunistic pathogen in different poultry production systems [3]. G. anatis has been associated with a wide range of lesions and reproductive tract disorders including salpingitis and peritonitis, and is considered a highly important opportunistic pathogen that can lead to lowered egg production and increased mortality [5]. To counteract the negative effects of antimicrobially resistant G. anatis strains, efficient prophylactic measures appear to be the logical alternative to antibiotics to prevent and control G. anatis infections in poultry production systems. A pan-genomic reverse vaccinology (RV) approach has previously been applied to identify novel and potentially broadly protective immunogens from G. anatis that resulted in a selection of five proteins GtxA, FlfA, Gab_2156, Gab_1309 and Gab_2312 [10]. Gab_1309 is a membrane protein related to metalloendopeptidases; Gab_2312 is an autotransporter adhesin and Gab_2156 is a F17-like fimbrial subunit [16]
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