Haemophilus influenzae infection: Difference between revisions
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{{ | {{Taxobox | ||
{{CMG}} | | 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 | |||
}} | |||
{{Haemophilus influenzae infection}} | |||
{{About1|Haemophilus influenzae}} | |||
'''For patient information about Haemophilus influenzae infection, click [[Haemophilus influenzae infection (patient information)|here]] | Haemophilus influenzae type b (Hib) vaccine, click [[Haemophilus influenzae Type b (Hib) Vaccine (patient information)|here]].'''<br><br> | |||
{{CMG}} ; {{AE}} {{ADG}} <br> | |||
{{SK}} Hib disease | {{SK}} Hib disease | ||
==Overview== | |||
[[Haemophilus influenzae|H.influenzae]] is a [[gram-negative]], [[Coccobacillus|cocco-bacillary]], [[Facultative anaerobic organism|facultatively anaerobic]] pathogenic bacterium that can cause infections in people of all ages ranging from mild, such as an ear infection, to severe, such as a bloodstream infection. It is a normal [[commensal]] of [[nose]] and [[throat]] and does not cause any infection under normal situations. But when the host [[Defence mechanism|defense mechanisms]] are weakened it invades the [[epithelium]] and [[Disseminated disease|disseminate]]<nowiki/>s to other parts of the body where it causes [[infection]].<ref name="urlPinkbook | Hib | Epidemiology of Vaccine Preventable Diseases | CDC">{{cite web |url=https://www.cdc.gov/vaccines/pubs/pinkbook/hib.html |title=Pinkbook | Hib | Epidemiology of Vaccine Preventable Diseases | CDC |format= |work= |accessdate=}}</ref> | |||
== | ==Causes== | ||
*[[Haemophilus influenzae|Haemophilus influenza]] infections are caused by the bacterium [[Haemophilus influenza]]. | |||
*It is a is a [[gram-negative]], [[Coccobacillus|cocco-bacillary]], [[Facultative anaerobic organism|facultatively anaerobic]] bacterium. | |||
*Based on their distinct capsular antigens they are grouped into capsular (typeable) and non-capsulate (nontypeable) | |||
*There are six identifiable types of [[Haemophilus influenzae|H.influenza]] (a, b, c, d, e, and f) | |||
*[[H. influenza infection|H. influenza type b]] is the most common type among capsular H.influeza. | |||
*These bacteria are a normal [[commensal]] of throat and nose. However, the [[bacteria]] can sometimes move to other parts of the body and cause infection. | |||
[[ | |||
[[Haemophilus influenzae | ==Classification== | ||
[[Haemophilus influenzae|H. influenzae]], including Hib, can cause many different kinds of [[infections]]. These infections can range from mild ear infections to severe diseases, like bloodstream infections. When the bacteria invade parts of the body, like [[spinal fluid]] or [[blood]], this is known as "invasive disease." Invasive disease is usually severe and can sometimes result in death.<br> | |||
The most common types of invasive disease caused by H.influenza are: | |||
*[[Pneumonia]] | |||
*[[Bacteremia]] | |||
*[[Meningitis]] | |||
*[[Epiglottitis]] | |||
*[[Cellulitis]] | |||
*Infectious [[arthritis]] | |||
The most common types of non-invasive disease caused by H.influenza are: | |||
*[[Otitis media]] | |||
*[[Conjunctivitis]] | |||
<small> | |||
{{Family tree/start}} | |||
{{Family tree | | | | | | | | | | | | | | | | | | | | | | | A01 | | | | | | | | | | | | |A01= '''[[H influenza infection]]'''}} | |||
{{Family tree | | | | | | | | | | |,|-|-|-|-|-|-|-|-|-|-|-|-|^|-|-|-|-|-|-|-|-|-|-|-|-|-|.| | }} | |||
{{Family tree | | | | | | | | | | C01 | | | | | | | | | | | | | | | | | | | | | | | | | C02 |C01= Infection due to capsulated [[Haemophilus influenzae|H influenzae]](Invasive)| C02= Infection due to non-capsulated [[Haemophilus influenzae|H influenzae]](Non-invasive)}} | |||
{{Family tree | | |,|-|-|-|v|-|-|-|^|-|-|-|v|-|-|-|v|-|-|-|v|-|-|-|.| | | | | |,|-|-|-|-|^|-|-|-|-|.|}} | |||
{{Family tree | | D01 | | D02 | | | | | | D03 | | D04 | | D05 | | D06 | | | | D07 | | | | | | | | D08 |D01= [[Meningitis]] |D02=[[Cellulitis]]|D03=[[Epiglottitis]] |D04= [[Pneumonia]]|D05=[[Pericarditis]]|D06=[[Septic arthritis]]|D07=[[otitis media]]|D08=[[Conjunctivitis]]}} | |||
{{Family tree/end}}</small> | |||
==Pathophysiology== | |||
The pathogenesis of H.influenzae infections can be described as follows:<ref name="pmid27508518">{{cite journal |vauthors=Duell BL, Su YC, Riesbeck K |title=Host-pathogen interactions of nontypeable Haemophilus influenzae: from commensal to pathogen |journal=FEBS Lett. |volume=590 |issue=21 |pages=3840–3853 |year=2016 |pmid=27508518 |doi=10.1002/1873-3468.12351 |url=}}</ref><ref name="pmid27527818">{{cite journal |vauthors=Close RM, Pearson C, Cohn J |title=Vaccine-preventable disease and the under-utilization of immunizations in complex humanitarian emergencies |journal=Vaccine |volume=34 |issue=39 |pages=4649–55 |year=2016 |pmid=27527818 |doi=10.1016/j.vaccine.2016.08.025 |url=}}</ref> | |||
===Transmission=== | |||
*Transmission is by direct contact or by inhalation of respiratory tract droplets. | |||
*[[Neonates]] can acquire the infection by [[aspiration]] of [[amniotic fluid]] or contact with genital tract secretions containing the bacteria. | |||
===Incubation period=== | |||
The [[incubation period]] (time between exposure and first symptoms) of [[Haemophilus influenzae|H. influenzae]] disease is not certain but could be as short as 7 days. | |||
===Seeding=== | |||
*A larger bacterial load or the presence of a concomitant viral infection can potentiate the infection. | |||
*The colonizing bacteria invade the mucosa and [[Bacteremia|enter the bloodstream]]. | |||
*The spread of bacteria by direct extension to the eustachian tubes causes [[otitis media]]. | |||
*Spread to the sinuses leads to [[Sinusitis|sinusitis.]] | |||
*Spread down the respiratory tract results in [[bronchitis]] and [[pneumonia]]. | |||
*[[Eustachian tube dysfunction]], antecedent viral upper respiratory tract infection ([[Upper respiratory tract infection|URT]]I), foreign bodies, and mucosal irritants, including smoking, can promote infection. | |||
*In patients with underlying [[chronic obstructive pulmonary disease]] ([[Chronic obstructive pulmonary disease|COPD]]) or [[cystic fibrosis]] ([[Cystic fibrosis|CF]]), non-typeable [[Haemophilus influenzae|H influenza]] frequently colonizes the [[Lower respiratory tract|lower respiratory trac]]<nowiki/>t and can exacerbate the disease. | |||
===Pathogenesis=== | |||
*The [[capsule]] of [[Hemophilus influenza infection|H influenza]] plays a key role in the pathogenesis of the all the capsulated H influenza infections. | |||
*The [[antiphagocytic]] nature of the Hib capsule makes it resistant to natural host phagocytic defense mechanisms and facilitating bacterial proliferation. | |||
*After proliferation, the bacterial load disseminates to various sites, including [[meninges]], [[subcutaneous tissue]], [[joints]], [[Pleurae|pleura]], [[pericardium]], and [[lungs]] triggering an inflammatory response and subsequently activating the [[complement system]]. | |||
*Capsulated H influenza can penetrate the normal epithelium and are therefore responsible for invasive infections. | |||
*Non-capsulated are non-invasive but can still induce the inflammatory response similar to that of capsulated organisms | |||
*The Hib [[conjugate vaccine]] induces protection by inducing antibodies against the PRP capsule. | |||
*The Hib conjugate vaccine does not provide protection against Non-typable H influenza strains. Since the widespread use of the Hib conjugate vaccine, Non-typable H influenza strains has become more of a pathogen. | |||
== | ==References== | ||
{{reflist|2}} | |||
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Latest revision as of 21:56, 29 July 2020
Haemophilus influenzae | ||||||||||||||
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![]() H. influenzae on a blood agar plate.
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Scientific classification | ||||||||||||||
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Binomial name | ||||||||||||||
Haemophilus influenzae (Lehmann & Neumann 1896) Winslow et al. 1917 |
Haemophilus influenzae infection Main page |
For patient information about Haemophilus influenzae infection, click here | Haemophilus influenzae type b (Hib) vaccine, click here.
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Synonyms and keywords: Hib disease
Overview
H.influenzae is a gram-negative, cocco-bacillary, facultatively anaerobic pathogenic bacterium that can cause infections in people of all ages ranging from mild, such as an ear infection, to severe, such as a bloodstream infection. It is a normal commensal of nose and throat and does not cause any infection under normal situations. But when the host defense mechanisms are weakened it invades the epithelium and disseminates to other parts of the body where it causes infection.[1]
Causes
- Haemophilus influenza infections are caused by the bacterium Haemophilus influenza.
- It is a is a gram-negative, cocco-bacillary, facultatively anaerobic bacterium.
- Based on their distinct capsular antigens they are grouped into capsular (typeable) and non-capsulate (nontypeable)
- There are six identifiable types of H.influenza (a, b, c, d, e, and f)
- H. influenza type b is the most common type among capsular H.influeza.
- These bacteria are a normal commensal of throat and nose. However, the bacteria can sometimes move to other parts of the body and cause infection.
Classification
H. influenzae, including Hib, can cause many different kinds of infections. These infections can range from mild ear infections to severe diseases, like bloodstream infections. When the bacteria invade parts of the body, like spinal fluid or blood, this is known as "invasive disease." Invasive disease is usually severe and can sometimes result in death.
The most common types of invasive disease caused by H.influenza are:
- Pneumonia
- Bacteremia
- Meningitis
- Epiglottitis
- Cellulitis
- Infectious arthritis
The most common types of non-invasive disease caused by H.influenza are:
H influenza infection | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Infection due to capsulated H influenzae(Invasive) | Infection due to non-capsulated H influenzae(Non-invasive) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Meningitis | Cellulitis | Epiglottitis | Pneumonia | Pericarditis | Septic arthritis | otitis media | Conjunctivitis | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Pathophysiology
The pathogenesis of H.influenzae infections can be described as follows:[2][3]
Transmission
- Transmission is by direct contact or by inhalation of respiratory tract droplets.
- Neonates can acquire the infection by aspiration of amniotic fluid or contact with genital tract secretions containing the bacteria.
Incubation period
The incubation period (time between exposure and first symptoms) of H. influenzae disease is not certain but could be as short as 7 days.
Seeding
- A larger bacterial load or the presence of a concomitant viral infection can potentiate the infection.
- The colonizing bacteria invade the mucosa and enter the bloodstream.
- The spread of bacteria by direct extension to the eustachian tubes causes otitis media.
- Spread to the sinuses leads to sinusitis.
- Spread down the respiratory tract results in bronchitis and pneumonia.
- Eustachian tube dysfunction, antecedent viral upper respiratory tract infection (URTI), foreign bodies, and mucosal irritants, including smoking, can promote infection.
- In patients with underlying chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF), non-typeable H influenza frequently colonizes the lower respiratory tract and can exacerbate the disease.
Pathogenesis
- The capsule of H influenza plays a key role in the pathogenesis of the all the capsulated H influenza infections.
- The antiphagocytic nature of the Hib capsule makes it resistant to natural host phagocytic defense mechanisms and facilitating bacterial proliferation.
- After proliferation, the bacterial load disseminates to various sites, including meninges, subcutaneous tissue, joints, pleura, pericardium, and lungs triggering an inflammatory response and subsequently activating the complement system.
- Capsulated H influenza can penetrate the normal epithelium and are therefore responsible for invasive infections.
- Non-capsulated are non-invasive but can still induce the inflammatory response similar to that of capsulated organisms
- The Hib conjugate vaccine induces protection by inducing antibodies against the PRP capsule.
- The Hib conjugate vaccine does not provide protection against Non-typable H influenza strains. Since the widespread use of the Hib conjugate vaccine, Non-typable H influenza strains has become more of a pathogen.
References
- ↑ "Pinkbook | Hib | Epidemiology of Vaccine Preventable Diseases | CDC".
- ↑ Duell BL, Su YC, Riesbeck K (2016). "Host-pathogen interactions of nontypeable Haemophilus influenzae: from commensal to pathogen". FEBS Lett. 590 (21): 3840–3853. doi:10.1002/1873-3468.12351. PMID 27508518.
- ↑ Close RM, Pearson C, Cohn J (2016). "Vaccine-preventable disease and the under-utilization of immunizations in complex humanitarian emergencies". Vaccine. 34 (39): 4649–55. doi:10.1016/j.vaccine.2016.08.025. PMID 27527818.