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Ornithobacterium rhinotracheale (ORT) has been associated with avian respiratory disease. On coinfection with other pathogens, ORT can cause serious health problems in avian species, leading to financial losses. To monitor the serologic prevalence of ORT in chicken flocks in China, 1,280 sera were collected to determine ORT antibodies among 64 flocks from 15 provinces of China using a commercial ELISA kit. The overall seroprevalence of ORT among the birds tested was 44.06%. In younger chickens, the serum positive rate was lower than that in older chickens, and with increased age, the serum positive rates increased. Older chickens had not only higher positive rates but also higher antibody levels. These data indicated that ORT infections were common in China. Because an ORT vaccine is currently not available, good disease management and biosecurity measures are required for effective disease control., (Copyright © 2020. Published by Elsevier Inc.)

Neuraminidases (sialidases) are virulence factors of several poultry pathogens. Ornithobacterium rhinotracheale is a well known poultry pathogen causing respiratory disease in chickens and turkeys all over the world. We investigated whether O. rhinotracheale has neuraminidase enzymatic activity (NEAC). We tested NEAC in 47 O. rhinotracheale strains isolated from turkeys and chickens in eight countries. All strains showed relatively strong NEAC and considerable levels of NEAC were detected also in "cell-free supernatants" of their pelleted cells. Zymography using neuraminidase-specific chromogenic substrate indicated that a protein with molecular mass of ~40kDa and isoelectric point (pI) of ~8.0 is a putative neuraminidase of O. rhinotracheale. Notably, the genome of the type strain of O. rhinotracheale, DSM 15997 contains a gene (Ornrh_1957) encoding a putative neuraminidase with such Mw (39.5 kDa) and pI (8.5). We sequenced a corresponding genomic region of 20 O. rhinotracheale strains and found five distinct types of the neuraminidase gene (termed nanO) sequences. Most diversified nanO sequence was found in two strains isolated from chickens in Hungary in 1995. Their nanO sequences differ from that of the type strain (LMG 9086(T)) in 27 nucleotides. O. rhinotracheale neuraminidase showed capacity to cleave sialic acid from chicken and turkey glycoproteins. It cleaved sialic acid from SAα(2-6)gal moiety of their serum proteins, including immunoglobulin G (IgG) and transferrin. O. rhinotracheale also desialylated chicken and turkey tracheal mucus glycoprotens with SAα(2-3)gal moieties. This study provides the first evidence that O. rhinotracheale has neuraminidase which can desialylate glycoproteins of its natural hosts., (Copyright © 2012 Elsevier B.V. All rights reserved.)