Evaluation of the chick embryo for the determination of relative virulence of<i>Neisseria meningitidis</i>

Pine, Leo; Quinn, Frederick D.; Ewing, Edwin P.; Birkness, Kristin A.; White, Elizabeth; Stephens, David S.; Ribot, Efrain M.

doi:10.1111/j.1574-6968.1995.tb07695.x

Cited by 3 publications

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

exl , an Exchangeable Genetic Island in Neisseria meningitidis

et al. 2001

View full text Add to dashboard Cite

The genetic structure and evolution of a novel exchangeable meningococcal genomic island was defined for the important human pathogen Neisseria meningitidis. In 125 meningococcal strains tested, one of three unrelated nucleotide sequences, designated exl (exchangeable locus), was found between a gene required for heme utilization, hemO, and col, encoding a putative Escherichia coli collagenase homologue. The 5 boundary of each exl cassette was the stop codon of hemO, whereas the 3 boundary was delineated by a 33-bp repeat containing neisserial uptake sequences located downstream of col. One of the three alternative exl cassettes contained the meningococcal hemoglobin receptor gene, hmbR (exl3). In other meningococcal strains, hmbR was absent from the genome and was replaced by either a nucleotide sequence containing a novel open reading frame, exl2, or a cassette containing exl3. The proteins encoded by exl2 and exl3 had no significant amino acid homology to HmbR but contained six motifs that are also present in the lipoprotein components of the lactoferrin (LbpB), transferrin (TbpB), and hemoglobin-haptoglobin (HpuA) uptake systems. To determine the evolutionary relationships among meningococci carrying hmbR, exl2, or exl3, isolates representing 92 electrophoretic types were examined. hmbR was found throughout the population structure of N. meningitidis (genetic distance, >0.425), whereas exl2 and exl3 were found in clonal groups at genetic distances of <0.2. The commensal neisserial species were identified as reservoirs for all of the exl cassettes found in meningococci. The structure of these cassettes and their correlation with clonal groups emphasize the extensive gene pool and frequent horizontal DNA transfer events that contribute to the evolution and virulence of N. meningitidis.

show abstract

exl , an Exchangeable Genetic Island in Neisseria meningitidis

et al. 2001

View full text Add to dashboard Cite

show abstract

The use of embryonic chicken eggs as an alternative model to evaluate the virulence of Salmonella enterica serovar Gallinarum

et al. 2020

View full text Add to dashboard Cite

Salmonella enterica serovar Gallinarum ( S . Gallinarum) can cause fowl typhoid, a severe systemic disease responsible for considerable economic losses. Chicken pathogenicity test is the traditional method for assessing the virulence of S . Gallinarum. However, this method is limited by several factors, including ethical considerations, costs, and the need for specialized facilities. Hence, we established a chicken embryo lethality assay (ELA) model to determine the virulence of S . Gallinarum. Three virulent and three avirulent representative strains, which were confirmed by the chicken pathogenicity test, were used to perform the ELA. The most significant difference between the virulent and avirulent strains could be observed when 13-day-old embryos were inoculated via the AC route and incubated for 5 days. Based on a 50% embryo lethal dose (ELD 50 ), isolates considered to be virulent had a Log 10 ELD 50 of ≤ 4.0, moderately virulent strains had a Log 10 ELD 50 of 4.0−6.1, and avirulent isolates had a Log 10 ELD 50 of ≥ 6.1. Different abilities to invade the liver of embryos were found between the virulent and avirulent strains by a growth curve experiment in vitro . The maximum colony-forming units (CFU) of the virulent strain was about 10,000 times higher than that of the avirulent strain in the liver at 5 days post infection. The ELA results of 42 field strains showed that thirty-two strains (76.2%) were virulent, nine were moderately virulent (21.4%), and one strain was avirulent (2.4%). In conclusion, these results suggest that the ELA can be used as an alternative method to assess the virulence of S . Gallinarum, which will contribute to the study of virulence genes, virulence evolution, pathogenic mechanisms and vaccine development.

show abstract

Animal Models for Meningococcal Disease

Gorringe

Reddin

Voet

et al.

Meningococcal Vaccines

View full text Add to dashboard Cite

There are many in vitro systems for the study of meningococcal pathogenesis, but it is only in animal models of infection that the interactions of the bacteria with whole tissues and the humoral and cellular immune systems can be assessed. Animal-infection models are also of great importance for the assessment of the protective efficacy of existing and candidate vaccines. However, the relevance of these animal models to human disease and how well protection assessed in them corresponds to protection against human disease, must always be considered. Animal models for pathogenic Neisseria have been previously reviewed (1).

show abstract

Evaluation of the chick embryo for the determination of relative virulence ofNeisseria meningitidis

Cited by 3 publications

References 16 publications

exl , an Exchangeable Genetic Island in Neisseria meningitidis

exl , an Exchangeable Genetic Island in Neisseria meningitidis

The use of embryonic chicken eggs as an alternative model to evaluate the virulence of Salmonella enterica serovar Gallinarum

Animal Models for Meningococcal Disease

Contact Info

Product

Resources

About