Haemophilus influenzae
929532
220861374
2008-06-21T23:32:53Z
DOI bot
6652755
Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]].
{{Infobox Disease
| Name = Haemophilus influenzae
| ICD10 = {{ICD10|A|49|2|a|40}}
| ICD9 = {{ICD9|041.5}}
| ICDO =
| Image =
| Caption =
| OMIM =
| OMIM_mult =
| MedlinePlus = 000612
| MedlinePlus_mult= (Meningitis)
| eMedicineSubj = search
| eMedicineTopic = Haemophilus%20influenzae
| DiseasesDB = 5570
}}
{{Taxobox
| color = lightgrey
| name = ''Haemophilus influenzae''
| image = Haemophilus influenzae 01.jpg
| image_width = 200px
| image_caption = ''H. influenzae'' on a [[Blood agar#Blood agar types|blood agar]] plate.
| regnum = [[Bacterium|Bacteria]]
| phylum = [[Proteobacteria]]
| classis = [[Gamma Proteobacteria]]
| ordo = [[Pasteurellaceae|Pasteurellales]]
| familia = [[Pasteurellaceae]]
| genus = ''[[Haemophilus]]''
| species = '''''H. influenzae'''''
| binomial = ''Haemophilus influenzae''
| binomial_authority = (Lehmann & Neumann 1896)<br>Winslow ''et al.'' 1917
}}
{{redirect|Hib|the university college|Bergen University College}}
'''''Haemophilus influenzae''''', formerly called '''Pfeiffer's bacillus''' or '''''Bacillus influenzae''''', is a non-motile [[Gram-negative]] [[coccobacillus]] first described in [[1892]] by [[Richard Friedrich Johannes Pfeiffer|Richard Pfeiffer]] during an [[influenza]] [[pandemic]]. A member of the ''[[Pasteurellaceae]]'' family it is generally [[aerobic organism|aerobic]], but can grow as a [[facultative anaerobe]].<ref name= KuhnertChristensen>{{cite book | author = Kuhnert P; Christensen H (editors). | title = Pasteurellaceae: Biology, Genomics and Molecular Aspects | publisher = Caister Academic Press | year = 2008 | id = ISBN 978-1-904455-34-9 }}</ref> ''H. influenzae'' was mistakenly considered to be the cause of the common flu until 1933, when the viral [[etiology]] of the flu became apparent. Still, ''H. influenzae'' is responsible for a wide range of clinical diseases.
''H. influenzae'' was the first free-living organism to have its entire genome sequenced. Haemophilus was chosen because one of the project leaders, Nobel laureate [[Hamilton Smith]], had been working on it for decades and was able to provide high-quality DNA libraries. The genome consists of 1,830,140 base pairs of DNA in a single circular chromosome that contains 1740 protein-coding genes, 58 transfer RNA genes [[tRNA]], and 18 other RNA genes. The sequencing method used was [[Whole-genome_shotgun|Whole genome shotgun]]. The sequencing project, completed and published in ''[[Science (journal)|Science]]'' in 1995, was conducted at [[The Institute for Genomic Research]].<ref name=Fleichmann_1995>{{cite journal |author=Fleischmann R, Adams M, White O, Clayton R, Kirkness E, Kerlavage A, Bult C, Tomb J, Dougherty B, Merrick J |title=Whole-genome random sequencing and assembly of Haemophilus influenzae Rd |journal=Science |volume=269 |issue=5223 |pages=496–512 |year=1995 |pmid=7542800| doi=10.1126/science.7542800 |url=http://www.sciencemag.org/cgi/content/abstract/269/5223/496 }}</ref>
==Serotypes==
In 1930, 2 major categories of ''H. influenzae'' were defined: the unencapsulated strains and the encapsulated strains. The [[pathogenesis]] of ''H. influenzae'' infections is not completely understood, although the presence of the encapsulated type b (Hib) is known to be the major factor in virulence. Their capsule allows them to resist [[phagocytosis]] and complement-mediated [[lysis]] in the non-immune host. Unencapsulated strains are less invasive, but they are able to induce an [[inflammatory]] response that causes disease, such as [[epiglottitis]]. Vaccination with Hib conjugate [[vaccine]]s is effective in preventing infection, and several vaccines are now available for routine use.
==Diseases==
Most strains of ''H. influenzae'' are opportunistic pathogens - that is, they usually live in their host without causing disease, but cause problems only when other factors (such as a viral infection or reduced immune function) create an opportunity. There are six generally recognized types of ''H. influenzae'': a, b, c, d, e, and f.<ref name=Sherris>{{cite book | author = Ryan KJ; Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | publisher = McGraw Hill | year = 2004 | pages= pp. 396–401| id = ISBN 0838585299 }}</ref>
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]]. Occasionally, it causes [[cellulitis]], [[osteomyelitis]], [[epiglottitis]], and joint infections. Due to routine use of the Hib conjugate vaccine in the U.S. 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 vaccine is not widely used. Unencapsulated ''H. influenzae'' (non-B type) causes ear ([[otitis media]]) and eye ([[conjunctivitis]]) infections and [[sinusitis]] in children, and is associated with [[pneumonia]].
==Diagnosis==
Clinical diagnosis of ''H. influenzae'' is typically performed by bacterial culture or latex particle agglutination. Diagnosis is considered confirmed when the organism is isolated from a sterile body site. In this respect, ''H. influenzae'' cultured from the nasopharyngeal cavity or sputum would not indicate ''H. influenzae'' disease because these sites are colonized in disease free individuals.<ref name= Puri_1999>{{cite journal |author= Puri J, Talwar V, Juneja M, Agarwal KN, Gupta HC |title= Prevalence of anti-microbial resistance among respiratory isolates of Haemophilus influenzae |journal= Indian Pediatr |volume=36 |pages= 1029–32|year=1999|pmid= 10745313 }}</ref> However ''H. influenzae'' isolated from cerebrospinal fluid or blood would indicate a ''H. influenzae'' infection.
===Culture===
Bacterial culture of ''H. influenzae'' is performed on [[Nutrient_agar|nutrient agar]], preferably [[Chocolate agar]], plate with added [[Hemin|X ]] & [[Nicotinamide_adenine_dinucleotide|V]] factors at 37̊C in an enriched CO2 incubator.<ref> {{Citation | title = Generic protocol for population-based surveillance of Haemophilus influenzae type B | year = 1997 | publisher = World Health Organization | id = WHO/VRD/GEN/95.05}}</ref> Blood agar growth is only achieved as a satellite phenomenon around other bacteria. Colonies of ''H. influenzae'' appear as convex, smooth, pale, grey or transparent colonies. [[Gram_stain|Gram-stained]] and microscopic observation of a specimen of ''H. influenzae'' will show Gram-negative, coccobacilli, with no specific arrangement. The cultured organism can be further characterized using [[catalase]] and [[oxidase]] tests, both of which should be positive. Further serological is necessary to distinguish the capsular polysaccharide and differentiate between ''H. influenzae'' B and non-encapsulated species.
Although highly specific, bacterial culture of ''H. influenzae'' lacks in sensitivity. Use of antibiotics prior to sample collection greatly reduces the isolation rate by killing the bacteria before identification is possible.<ref name= John_1991>{{cite journal |author= John TJ, Cherian T, Steinhoff MC, Simoes EA, John M |title= Etiology of acute respiratory infections in children in tropical southern India |journal= Rev Infect Dis |volume=13 |pages= Suppl 6:S463–9 |year=1991 |pmid= 1862277 }}</ref> Beyond this, ''H. influenzae'' is a finicky bacterium to culture, and any modification of culture procedures can greatly reduce isolation rates. Poor quality of laboratories in developing countries has resulted in poor isolation rates of ''H. influenzae''.
===Latex particle agglutination===
Latex particle agglutination test (LAT) is a more sensitive method to detect ''H. influenzae'' than culture.<ref name= Kennedy_2007>{{cite journal |author= Kennedy WA, Chang SJ, Purdy K, LE T, Kilgore PE, Kim JS et al |title= Incidence of bacterial meningitis in Asia using enhanced CSF testing: polymerase chain reaction, latex agglutination and culture |journal= Epidemiol Infect |volume=135 |pages= 1217–26 |year=2007 |pmid= 17274856 |doi= 10.1017/S0950268806007734 }}</ref> Because the method relies on antigen rather than viable bacteria, the results are not disrupted by prior antibiotic use. It also has the added benefit of being much quicker than culture methods. However, antibiotic sensitivity is not possible with LAT, so a parallel culture is necessary.
===Molecular Methods===
[[Polymerase chain reaction]] (PCR) assays have been proven to be more sensitive than either LAT or culture tests and highly specific.<ref name= Kennedy_2007>{{cite journal |author= Kennedy WA, Chang SJ, Purdy K, LE T, Kilgore PE, Kim JS et al |title= Incidence of bacterial meningitis in Asia using enhanced CSF testing: polymerase chain reaction, latex agglutination and culture |journal= Epidemiol Infect |volume=135 |pages= 1217–26 |year=2007 |pmid= 17274856 |doi= 10.1017/S0950268806007734 }}</ref>However, PCR assays have not yet become routine in clinical settings. Counter-current immunoelectrophoresis has been shown to be an effect research diagnostic method, but has been largely supplanted by PCR.
==Interaction with ''Streptococcus pneumoniae''==
Both ''H. influenzae'' and ''[[Streptococcus pneumoniae|S. pneumoniae]]'' can be found in the upper respiratory system of humans. A study of competition in a laboratory revealed that, in a petri dish, ''S. pneumoniae'' always overpowered ''H. influenzae'' by attacking it with [[hydrogen peroxide]] and stripping off the surface molecules that ''H. influenzae'' needs for survival.
When both bacteria are placed together into a nasal cavity, within 2 weeks, only ''H. influenzae'' survives. When either is placed separately into a nasal cavity, each one survives. Upon examining the upper respiratory tissue from mice exposed to both bacteria species, an extraordinarily large number of [[neutrophils]] (immune cells) was found. In mice exposed to only one bacteria, the cells were not present.
Lab tests showed that neutrophils exposed to dead ''H. influenzae'' were more aggressive in attacking ''S. pneumoniae'' than unexposed neutrophils. Exposure to dead ''H. influenzae'' had no effect on live ''H. influenzae''.
Two scenarios may be responsible for this response:
# When ''H. influenzae'' is attacked by ''S. pneumoniae'', it signals the immune system to attack the ''S. pneumoniae''
# The combination of the two species together triggers an immune system response that is not set off by either species individually.
it has been shown in cytological studies in immunodeficient patients that HI lives intracellular in epithelial cells in the epipharynx. this can inpart explain frequent reinfections with Hi in this patientgroup. (citation??)
It is unclear why ''H. influenzae'' is not affected by the immune response.<ref name=Lysenko_2005>{{cite journal |author=Lysenko E, Ratner A, Nelson A, Weiser J |title=The role of innate immune responses in the outcome of interspecies competition for colonization of mucosal surfaces |journal=PLoS Pathog |volume=1 |issue=1 |pages=e1 |year=2005 |pmid=16201010 |doi=10.1371/journal.ppat.0010001}}</ref>
==See also==
{{commonscat|Haemophilus influenzae}}
*[[Pasteurellaceae]]
*[[Maurice Hilleman]]
*[[Hattie Alexander]]
*[[Hib vaccine]]
==References==
<!-- ----------------------------------------------------------
See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for a
discussion of different citation methods and how to generate
footnotes using the <ref>, </ref> and <reference /> tags
----------------------------------------------------------- -->
<div class="references-small">
<references />
</div>
==External links==
* [http://www.who.int/vaccines/en/haeflub.shtml Hib information] on the [[World Health Organization]] (WHO) site.
* [http://www.cdc.gov/ncidod/dbmd/diseaseinfo/haeminfluserob_t.htm Fact sheet] on the [[Centers for Disease Control and Prevention]] (CDC) site.
* [http://www.hibaction.org Hib Initiative] - from [[Johns Hopkins University]], [[London School of Hygiene & Tropical Medicine]], [[Centers for Disease Control and Prevention|CDC]] & [[World Health Organization|WHO]]
[[Category:Proteobacteria]]
[[Category: Polysaccharide encapsulated bacteria]]
[[de:Haemophilus influenzae b-Infektion]]
[[es:Haemophilus influenzae]]
[[fr:Haemophilus influenzae]]
[[nl:Haemophilus influenzae]]
[[ja:インフルエンザ菌]]
[[pl:Haemophilus influenzae]]
[[pt:Haemophilus influenzae]]
[[fi:Haemophilus influenzae]]
[[sv:Haemophilus influenzae]]
[[zh:流感嗜血桿菌]]