Bordetella avium Virulence Measured In Vivo and In Vitro

Abstract

Bordetella avium causes an upper-respiratory-tract disease called bordetellosis in birds. Bordetellosis shares many of the clinical and histopathological features of disease caused in mammals byBordetella pertussis and Bordetella bronchiseptica. In this study we determined several parameters of infection in the domestic turkey, Meleagris galapavo, and compared these in vivo findings with an in vitro measure of adherence using turkey tracheal rings. In the in vivo experiments, we determined the effects of age, group size, infection duration, and interindividual spread of B. avium. Also, the effect of host genetic background on susceptibility was tested in the five major commercial turkey lines by infecting each with the parental B. avium strain and three B. avium insertion mutants. The mutant strains lacked either motility, the ability to agglutinate guinea pig erythrocytes, or the ability to produce dermonecrotic toxin. The susceptibilities of 1-day-old and 1-week-old turkeys to B. avium were the same, and challenge group size (5, 8, or 10 birds) had no effect upon the 50% infectious dose. Two weeks between inoculation and tracheal culture was optimal, since an avirulent mutant (unable to produce dermonecrotic toxin) persisted for a shorter time. Communicability of the B. aviumparental strain between confined birds was modest, but a nonmotile mutant was less able to spread between birds. There were no host-associated differences in susceptibility to the parental strain and the three B. avium mutant strains just mentioned: in all turkey lines tested, the dermonecrotic toxin- and hemagglutination-negative mutants were avirulent whereas the nonmotile mutants showed no loss of virulence. Interestingly, the ability of a strain to cause disease in vivo correlated completely with its ability to adhere to ciliated tracheal cells in vitro.

The effect of treatment on pathogen virulence

“…For example, trypanosomes and malarial parasites undergo antigenic variation within single infections. Heightened virulence has been found to prolong the period of infectiousness in lizard malaria Plasmodium mexicanum (Eisen and Schall, 2000), myxoma virus in rabbits (Fenner and Ratcliffe, 1965;Anderson and May, 1991), canine parvovirus (Meunier et al, 1985), Bordetella avium (Temple et al, 1998), hepatitis B virus (Fong et al, 1994) and influenza (Van dergoot et al, 2003). We explore the case in which the recovery rate r is a decreasing (or at least nonincreasing) function of the virulence parameter v. (Note that a recovery rate that increases with the virulence could be subsumed into the increasing mortality rate d without loss of generality.…”

Establishment of a Bordetella avium challenge model in turkeys

“…Additionally, the results of the preliminary in vitro trials contradict this speculation. It is known from BA that ability to adhere to the tracheal mucosa in tracheal organ cultures is correlated to virulence in vivo (Temple et al, 1998).…”

“…The isolate was identified as BA by polymerase chain reaction (Savelkoul et al, 1993;Register & Yersin, 2005). Virulence-associated properties such as ciliostatic effects and ability to adhere to the tracheal mucosa were determined using tracheal organ cultures of 26-day-old turkey embryos (Temple et al, 1998). In comparison to 10 other BA strains, strain 1860 showed high potency in these parameters (data not shown).…”

“…Some investigations about pathogenesis and clinical outcome of BA infection (Saif, et al, 1980;Gray et al, 1983;Temple et al, 1998) and immune response to the pathogen (Suresh et al, 1994) have been done in earlier studies. In these studies, turkey poults were infected within the first seven days of life.…”

Biofilm formation and cellulose expression by Bordetella avium 197N, the causative agent of bordetellosis in birds and an opportunistic respiratory pathogen in humans

“…Antibiotic susceptibility was assessed using antibiotic disks (MAST, UK). Kanamycin (Km) sensitivity [10] was confirmed using LB plates containing 100 µg.ml -1 Km incubated at 28°C for 48 hr.…”