Bacterial invasion and intracellular viability Analysis of the capability of mutants to enter avian macrophages was carried out using an invasion assay in the avian macrophage HD-11 cell line. Results showed no significant differences between mutant strains and the parent strains E058 and U17, with the invasion ratios varying from 0.24–0.26 (P>0.05). To determine whether the iron uptake systems are required for intracellular survival, we compared the CFU of the wild-types and isogenic mutants recovered at 2, 4, 6, 12, and 24 hours post infection (h.p.i.). We observed similar intracellular bacterial
proliferation rates, with rates of 62–65% at 2 h.p.i., which then decreased to a rate of approximately 50% at 4 h.p.i.. Rates fell sharply to approximately 10% at 6 h.p.i.. The numbers of recovered CFU at 12 and 24 h.p.i. were below detectable levels. selleck chemicals Since
iron acquisition systems are assumed to be functionally redundant, this may permit intracellular survival in the absence of one or several systems. Further, there may be TonB-independent transport systems that could compensate for the mutations in the intracellular environment. Histopathological lesions caused by iron acquisition Atezolizumab in vitro defective mutants in chickens Histopathological lesions in chickens challenged Adenylyl cyclase with virulent wild-type strains or iron acquisition defective mutants were compared. The lesions in the tested organs were graded according to the lesion severity and character (Table 1). The pathological characteristics of the tested visceral organs from chickens challenged with wild-type strains were as follows. In the heart sections, unequal-sized focal necrotic lesions were present in the disintegrated muscle fibers, and fibrous exudates appeared in the epicardium (Figure 3A and Figure 3F). The
liver sections showed that inflammatory cell infiltrations were present in the hepatic lobule, and numerous small fat granule vacuoles were observed in the cytoplasm (Figure 4A and Figure 4F). The lung sections revealed numerous inflammatory exudates in the bronchial cavity (data not show). However, no obvious pathological lesions were observed in the heart or liver sections of birds challenged with any of the mutant strains, except for the Δ chuT mutants (Figure 3 and Figure 4). The ΔchuT mutants caused lesions in both the heart and liver of the challenged birds that were equivalent to the wild-type strains. This was in accordance with the results obtained in chicken colonization and persistence assays, from which the chuT mutation did not affect the virulence of the wild-type strains (Figure 1).