HAEMOPHILUS INFLUENZAE

Haemophilus influenzae formerly called Pfeiffer's bacillus or Bacillus influenzae, is non-motile bacteria Gram-negative rod-shaped first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the family Pasteurellaceae, is generally aerobic, but can grow up to be facultative anaerobes. H. influenzae was mistakenly considered to be the cause of influenza until 1933, when the etiology of the flu virus becomes apparent .. However, H. influenzae is responsible for a variety of clinical disease.

H. influenzae is the first free living organism to have its entire genome sequenced. Sequencing projects have been completed and published in 1995.

Serotypes  
In 1930, two major categories of H. influenzae defined: the strains of unencapsulated and encapsulated strains. Encapsulated strains are classified by their distinct capsular antigen. There are six generally recognized types of H. influenzae encapsulated: a, b, c, d, e, and f. Genetic diversity among strains of unencapsulated greater than in the encapsulated group. unencapsulated strains termed nontypable (NTHI) because they are less capsular serotypes, but they can be classified by multi-locus sequence typing. Pathogenesis of infection H. influenzae is not completely understood, despite the presence of capsules are packaged in a type b (Hib), a serotype causing conditions such as epiglottitis, known to be a major factor in virulence. capsules allows them to resist phagocytosis and complement-mediated lysis in non-immune host. Unencapsulated strains are almost always less invasive, but they can produce an inflammatory response in humans that can cause many symptoms. Vaccination with Hib conjugate vaccine is effective in preventing Hib infection. Several vaccines are now available for routine use against Hib, but not yet available vaccine against NTHI. 

Disease  
Most strains of H. influenzae opportunistic pathogens - that is, they usually stay in their place without causing disease, but cause problems only when other factors (such as viral infection or reduced immune function) create an opportunity.
Naturally-acquired disease caused by H. influenzae seems to occur in humans only. In infants and young children, H. influenzae type b (Hib) causes bacteremia, pneumonia, and acute bacterial meningitis. Sometimes, it causes cellulitis, osteomyelitis, epiglottitis, and infectious arthritis. Because the routine use of Hib conjugate vaccine in the United States since 1990, the incidence of invasive Hib disease has decreased to 1.3/100, 000 in children. However, Hib remains a major cause of lower respiratory tract infections in infants and children in developing countries where the vaccine is not widely used. Unencapsulated H. influenzae causes ear infections (otitis media), eye infections (conjunctivitis), and sinusitis in children and is associated with pneumonia.

Diagnosis 
 H. influenzae Gram stain sputum samples, appearing as Gram-negative bacilli-Cocco. Clinical diagnosis of H. influenzae is usually done by a bacterial culture or latex particle agglutination. The diagnosis is considered confirmed when the organisms isolated from sterile body sites. In this case, H. influenzae cultured from the nasopharyngeal cavity or sputum will not show disease H. influenzae because the site is occupied in disease-free individuals. However, H. influenzae isolated from cerebrospinal fluid or blood will show H. influenzae infection.

Culture 
 bacterial culture of H. influenzae performed on the plate so that, should the Chocolate agar plates by adding X (hemin) & V (NAD) factor at 37 ° C in a CO2 incubator enriched blood agar growth is. achieved as a phenomenon only satellite in the vicinity of other bacteria. Colonies of H. influenzae colonies appear as convex, smooth, pale, gray or transparent. Gram stained and microscopic observation of specimens of H. influenzae will show Gram-negative coccobacilli, without special arrangements. The organism can be cultured further characterized using catalase and oxidase tests, which must both be positive. Further serological polysaccharide capsule is required to distinguish and differentiate between b H. influenzae and non-encapsulated species. 

Although highly specific, bacterial culture of H. influenzae has no sensitivity. The use of antibiotics prior to sample collection greatly reduces the isolation level by killing the bacteria before identification is possible. In addition to this, H. influenzae is a bacterium with exacting culture, and culture of each modification procedure can greatly reduce the level of isolation. Poor quality of laboratories in developing countries has resulted in poor isolation rate of H. influenzae.
H. influenzae will grow in zones of hemolytic Staphylococcus aureus in Blood To plate. The hemolysis of cells by Staph. Staphylococcus release of nutrients essential for growth of H. influenzae. H. influenzae will not grow beyond the zone of hemolytic Staph. due to lack of nutrients in areas aureus.


Latex particle agglutination  
Latex particle agglutination test (LAT) is more sensitive methods for detecting H. influenzae from culture. Because this method relies on the antigen rather than viable bacteria, the results are not compromised by previous antibiotic use. He also has the added benefit of being much faster than culture methods. However, antibiotic sensitivity not possible with the LAT, so that parallel cultures required.




Molecular Methods  
Polymerase chain reaction (PCR) assay has been shown to be more sensitive than either test or culture and LAT are very specific, however,. PCR has not become routine in clinical settings. Counter-current immunoelectrophoresis has been proven as an effective diagnostic method of research, but most have been replaced with the PCR. 

Interaction with Streptococcus pneumoniae 
 Both H. influenzae and S. pneumoniae can be found in the human upper respiratory system. A study reveals that competition in the laboratory, in petri dishes, S. pneumoniae is always controlled by H. influenzae by attacking with hydrogen peroxide and stripping of the surface molecules of H. influenzae needs to survive.
When both bacteria are placed together into the nasal cavity, within 2 weeks, only H. influenzae survive. When both are placed separately into the nasal cavity, respectively survive. After examining the upper respiratory tissues from rats exposed to both types of bacteria, a very large number of neutrophils (immune cells) are found. In mice exposed to only one bacteria, the cells were not present.
Laboratory tests showed that neutrophils exposed to H. influenzae die more aggressive in attacking S. pneumoniae than unexposed neutrophils. Exposure to H. influenzae die no effect on H. influenzae life. 

Two scenarios may be responsible for this response:  

1. When H. influenzae is attacked by S. pneumoniae, signals the immune system to attack S. Pneumoniae   
2. The combination of the two species together trigger the immune system response that did not set out either by individual species. 

It is unclear why H. influenzae is not affected by the immune response. 

Treatment  
Haemophilus influenzae produce beta-lactamase, and is also capable of modifying the penicillin binding proteins, so it has a resistance to the penicillin family of antibiotics. In severe cases of cefotaxime and ceftriaxone are the antibiotics chosen, delivered directly into the bloodstream, and for less severe cases of the association and sulbaktam ampicillin, second-and third-generation cephalosporins, or fluoroquinolones. macrolide antibiotics (eg clarithromycin) can be used in patients with a history of allergy to beta-lactam antibiotics. 

Sequencing  
H. influenzae is the first free living organism to have its entire genome sequenced. Haemophilus selected as one of the project leader, Nobel laureate Hamilton Smith, has worked there for decades and are able to provide high-quality DNA libraries. genome consists of 1,830,140 base pairs of DNA in a single circular chromosome containing 1740 protein-coding genes, 58 transfer RNA genes tRNA, and 18 RNA genes. The method used is the whole genome shotgun sequencing. Sequencing project, completed and published in Science in 1995, performed at The Institute for Genomic Research. 

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