Haemophilus influenzae

Description and Significance

Haemophilus influenzae is a bacterial inflection in the blood stream. It was first isolated by Pfeiffer during the 1890’s around the influenza pandemic tie period. Haemophilus influenzae grows best around 35-37 degree with a pH level of 7.6 and a specific growth factor that can be found in the blood stream. In labs this bacteria can be grown under aerobic conditions with 5 % CO2 tension in the atmosphere. Since 1988 a more serious strain of bacteria H. influenzae type b had been abolish in the U.S. due to effective vaccine development. H. influenzae type b causes meningitis, which is an inflection in the membrane around the brain and epiglottitis which is infection around the throat and trachea. In general H. Influenzae bacteria lives in the upper respiratory tract which can be transmitted by close contact with patients. This bacterial infection can also be air born transmitted through sneezing.

Genome Structure

H. influenzae became the first free-living organism with its entire genome sequenced. Its genome consists of 1,830,140 base pairs of DNA and contains 1740 genes. The linear DNA sequence of bacterial chromosome gives information, identifying all potential open reading frames, intergenic sequences, and their orgainzation within the genome. (5) The genome of these bacteria contains information on the genetic basis for each influencing host. The H. influenzae genome sequence provides the starting opint for significant research on bacterial metabolism, host adaptation, and virulence. Analysis of the genetics of biosynthesis and biology of LPS (lipopolysaccharide) in H influenzae indicated shows that LPS has complex cell surface glycolipid. (5) The saccharide portion of H. influenzae LPS is involve in host cell interaction and the lipid A portion of the molecule, the endotoxin, iitiates the cytokina casade as part of the host response to infection.

Cell Structure and metabolism

Haemophilus influenzae is a small gram negative bacteria which is about 1x 0.3um in size and it also lack the presence of flagella and pili, which means it lack mobility. (6) Some of these bacteria contain polysaccharide capsule which function as protection and colonization. These bacteria resemble other gram negative bacteria in structure, composition and endotoxic activity. The cell wall has an ultra structure composed of multiple wavy outer membranes and a poorly defined plasma membrane with an intervening electron transparent space. The outer cell wall has vesicular structure which is morphologically identical to lipopolysaccharide vesicles and are excreted into the surroundings. “Encapsulated strains express one of six structurally and antigenically distinct polysaccharide capsules, designated serotypes a to f.” (5) This bacteria is generally aerobic, but can grow as a facultative anaerobe.