Haemophilus aegyptius
1. Classification
a. Higher order taxa Bacteria, Proteobacteria, Gamma Proteobacteria, Pasteurellales, Pasteurellacease, Haemophilus (1)
b. Species Haemophilus Influenzae (1)
2. Description and significance
Haemophilus influenzae biogroup aegyptius is a Gram-negative bacterium with an elongated rod shape (2). H. aegyptius is normally found living in human epithelial cell linings (10), where it exhibits colonization and adherence to epithelial cells with large clusters of elongated chains of cells (2). As a biogroup, H. influenzae biogroup aegyptius has traits that differ from Haemophilus influenzae (H. influenzae), including the severity of virulence and lack of genes that encode for a polysaccharide capsule (3) in H. influenzae biogroup aegyptius. For over a century since its first discovery, H. influenzae biogroup aegyptius had only been known to cause conjunctivitis. However, in 1995, the HaeBPF strain of H. influenzae biogroup aegyptius (3) was identified in patients with Brazilian Purpuric Fever (BPF) (4). BPF has symptoms that are similar to that of meningococcal sepsis, which include an infection that results in high fever, vomiting, abdominal pain, and hemorrhagic skin lesions (5). Researchers have spent over two decades learning about the transformation of H. influenzae biogroup aegyptius from causing mild conjunctivitis to deadly BPF. However, much is still unknown about the organism’s virulence factors (6). Because of this, studies have been focused on understanding the mechanism of pathogenesis and developing preventative measures and treatments for BPF.
3. Genome structure
The Haemophilus influenzae biogroup aegyptius genome, or F3031 genome, contains 77% shared sequences with other H. influenzae genomes (4). The Hae accessory genome sequences were delineated and 163 protein-coding genes were characterized as adhesins and fimbrial operons (3). The Haemophilus influenzae biogroup aegyptius genome includes 3031 plasmids, and sequences coding for pilin proteins (6).
Unique genes sequences to the genome of H. influenzae biogroup aegyptius are: the bpf001 and bpf002 genes, which are associated with Brazilian Purpuric Fever (BPF) (4), and the Haemophilus adhesin A gene (HadA) (7). bpf001 and bpf002 code for proteins that enhance epithelial cell entry, correlating with cell invasion of human respiratory epithelial cells during the pathogenesis of BPF (4). The HadA gene codes for an adhesion protein that is associated with adherence to extracellular matrix proteins of human cells during the onset of BPF (7).
There has been evidence of exchange of the Las gene between H. influenzae biogroup aegyptius and Neisseria meningitidis, a bacterium that causes brain and spinal cord inflammation (5).
4. Cell structure
Unique to the H. influenzae biogroup aegyptius’s cell structure is an oliogomeric coiled-coil adhesion (Oca) adhesion called HadA (Haemophilus adhesion A), an adhesion protein. HadA allows bacterial aggregation when present in liquid culture, possibly through intrinsic hydrophilic properties and promotion of bacterial attachment to and invasion of host cells (7). These phenotypic properties of HadA are associated with cell invasion in the pathogenesis of Brazilian Purpuric Fever (BPF).
During interaction with epithelial cells, H. influenzae biogroup aegyptius exhibits colonization and adherence to epithelial cells with large clusters of elongated chains of bacterial cells. This clustering of H. influenzae biogroup aegyptius is unlike H. influenzae, which organizes by an even distribution as individual coccobacilli on epithelial cells (2).
5. Metabolic processes
Haemophilus influenzae biogroup aegyptius has metabolic characteristics similar to H. influenzae in metabolizing sugars. H. influenzae metabolizes fructose using phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) (8). When there is a scarcity in available fructose, H. influenzae transports and metabolizes fucose using fuculokinase, which is coded by an operon unique to H. influenzae (9).
A notable difference of H. influenzae biogroup aegyptius, compared to other H. influenzae strains, is its inability to ferment xylose and its inability to produce indole (9). Inability to produce indole is an implication that H. influenzae biogroup aegyptius lacks the enzyme tryptophanase (9), which is present in other H. influenza strains. H. influenzae biogroup aegyptius also exhibits urease activity, but lacks ornithine decarboxylase activity (2).
6. Ecology
H. influenzae biogroup aegyptius is normally found as an inhabitant of human epithelial cell linings (10) such as the oropharynx (1) and the epithelial layer of the eyes, where it presents as conjunctivitis (4). The manifestation of H. influenzae biogroup aegyptius has been identified as the disease-causing agent of BPF (11) in children and adults.
7. Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
7. Key microorganisms
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8. Current Research
Include information about how this microbe (or related microbes) are currently being studied and for what purpose
9. References
It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.
