Hemophilus Influenzae - Overview of Hemophilus Influenzae

Hemophilus Influenzae

Hemophilus Influenzae is a gram negative, non motile bacillus. It has fastidious growth requirements. It requires enriched media such as blood agar or chocolate agar for their growth because accessory growth factors known as factor X and V present in blood are essential for their growth. Optimum temperature for their growth is 35-37 degree. Antigenic structure consists of 3 major surface antigens capsular polysaccharide, outer membrane protein, lipo polysaccharide. Type b polysaccharide has a unique chemical structure containing polyribosyl ribitol phosphate which induces IgG, IgM, IgA antibodies which are bactericidal, opsonic & protective. Virulence factors are capsular polysaccharide which resist phagocytosis, pili which helps in the attachment of organism to epithelial cells, outer membrane proteins which contribute to adhesion and invasion of host tissues, IgA1 protease that specifically cleaves the heavy chain of IgA1. They are commensal in the nasopharynx or oropharynx.

Infections caused by Haemophilus influenzae B are Meningitis, Acute epiglottitis, Pneumonia, Bronchitis& Suppurative lesions. H.influenzae is killed by heat 55 degree C for 30mins, refrigeration at 4 degree C, disinfectants& drying. The specimens to be collected for laboratory diagnosis are CSF, Blood, Throat swab, Sputum, Pus, aspirates from joints, middle ear, sinuses etc. These specimens can be sent for direct microscopy such as Gram staining, Immunofluorescence and quelling reaction, CIE or it can be sent for Culture. It can be treated by using Sulphonamides, Chlorampnenicol, Cefotaxime, ceftazidime. But Amoxycillin-clavunate or Clarithromycin is more effective. Prophylaxis is purified type b polysaccharide vaccine used in children, Haemophilus influenzae B PRP vaccine used in young children.

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