View source for Mycobacterium tuberculosis

* ''Mycobacterium tuberculosis'' causes '''tuberculosis'''
* Most commonly '''pulmonary TB''' but extrapulmonary tuberculosis is possible (including adenitis, gastrointestinal TB, pericarditis, meningitis)
* Standard treatment for susceptible TB is '''RIPE x2mo then RI x4mo'''

== Background ==
=== Microbiology ===
* Fastidious [[Has Gram stain::acid-fast]] [[Has shape::bacillus]]

=== Epidemiology ===
* Reinfection accounts for ~40% of active tuberculosis in endemic countries
* Latent tuberculosis in ~30% of the global population

== Clinical Presentation ==
=== Classification ===
* Primary vs. reactivation vs. reinfection
* Latent vs. active

=== Primary tuberculosis ===
* Primary tuberculosis is usually asymptomatic
* Possible presentations include mild URTI with cough and/or fever
* May be seen on CXR as infiltrate in mid-lung zones with hilar adenopathy
* Ghon complex, especially in children
* May progress in children and the immunocompromised patients
* Immunological phenomena
** Erythema nodosum
** Phlyctenular conjunctivitis
** Erythema induratum

=== Pulmonary tuberculosis ===
* Subacute or [[chronic cough]] (at least 2 to 3 weeks) eventually becoming productive and occasionally involving [[hemoptysis]]
** Should be suspected in any patient with '''cough and [[HIV]] infection'''
* Constitutional symptoms, with fevers, night sweats, and unexplained weight loss
* Usually from reactivation of [[latent tuberculosis infection]], and usually reactivates in lung apices
* May transiently improve with partially-active antibiotics such as [[fluoroquinolones]]

=== Extra-pulmonary tuberculosis ===
* Pleural tuberculosis is most common extrapulmonary site
* [[Scrofula]] (cervical lymph node infection) next-most common
* [[Tuberculous meningitis]]
* [[Tuberculous pericarditis]]
* Renal tuberculosis
* Abdominal tuberculosis
* Gastrointestinal tuberculosis

=== Latent tuberculosis ===
* Refers to chronic latent infection contained within granulomas that may reactivate in the future
* Refer to [[Latent tuberculosis infection]]

== Investigations ==
* Radiography: chest x-ray with or without CT chest
* Microbiology:
** Samples can include routine or induced sputum (x3) or bronchoscopy, or tissue sample
** Spontaneous sputum should include at least one morning sputum, ideally
** Acid-fast bacillus culture of sputum x3 is about 70% sensitive, and PCR (ANTB) x1 is about 75% sensitive

== Management ==
* Standard HREZ x2mo then HR x4mo
** Isoniazid 5mg/kg/d, max 300mg daily
** Rifampin 10mg/kg/d
** Pyrazinamide 25mg/kg/d, max 2g daily
** Ethambutol 20mg/kg/d, max 1.2g daily
** Pyridoxine 25 mg po daily
* Airborne precautions until:
** Treated for at least 2 weeks
** 3x negative sputum smears
*** Collected at 8- to 24-hour intervals, including one early morning collection
** Improvement in symptoms

=== Immune reconstitution inflammatory syndrome (IRIS) ===

=== Drug-induced liver injury (DILI) ===
* Most common complication leading to treatment interruption, with a mortality of 6-12% if drugs are not stopped
* Rif &gt; INH &gt; PZA
* Most patients can have the same TB drugs reintroduced without recurrence of DILI, though recurrence can be delayed
* Procedure
** Hold if ALT &gt;120 and symptoms, if ALT &gt;200 even without symptoms, or bili &gt;2x ULN
** Switch to second-line meds
** Reintroduce the original drugs once AST &amp; ALT are &lt;2x ULN
** Only rechallenge with pyrazinamide if it was a mild case

=== Adherence to Treatment ===
* Refer to [http://www.letstalktb.org/ Let's Talk TB]

== Further Reading ==
* [https://www.canada.ca/en/public-health/services/infectious-diseases/canadian-tuberculosis-standards-7th-edition.htmlCanadian  Tuberculosis Standards, 7th Edition (2014)] 

{{DISPLAYTITLE:''Mycobacterium tuberculosis''}}
[[Category:TB]]
[[Category:Mycobacteria]]