Tuberculolsis Flashcards
what two-subspecies cause tuberculosis?
- mycobacterium tuberculosis- common, human
- mycobacterium bovis- rare, humans, cattle, deer, elk
- bacillus
- do not show up on gram stain
- require a special stain: Acid fast stain; ziehl-neelsen stain
- grow on special media
mycobacterium tuberculosis
Risk factors for TB
HIV infection
- Markedly increases risk of acquiring TB
- risk of TB increases with degree of T-cell suppresion (lower CD4 count)
Contact
- with a known infectious case of TB
-Immigration from a country where TB is endemic
-immunosuppressed
-injection drug users
-residents and employees of: prisons and jails, nursing homes, hospitals, HIV hospices, homeless shelters
Transmission of TB
- Small droplet particles
- air infectious even after person leaves
- close contact increases risk
- one case will infect 80% of susceptible contacts
- human crowding marked risk factors
clinical manifestations of TB?
Constitutional symptoms
- anorexia
- fatigue
- weight loss
- afternoon fever
- night sweats
Focal symptoms
- productive cough
- hemptysis
- chest pain
- hoarsness
physical exam findings in TB
- may be no findings despite extensive disase
- chest dullness to percussion
- rales
- tubular breath sounds
- whispered pectoriloquy
- distant hollow breath sounds (amphoric)
Radiographic manifestations of pulmonary TB?
- Patchy or nodular infiltrates in upper lobes
- cavity formation
- hilar adenopathy
- segmental or lobar infiltrate
- atelectasis
- pleural effusion
- miliary TB
extrapulmonary manifestations of tuberculosis?
- Meningitis
- bone- osteomylitis (long bones, spine- “Pott’s disease”
- Gastrointestinal
- renal
- genital- esp. female GU tract
- scofula- isolated lymph node in neck
diagnosis of TB?
- tuberculin skin test
- interferon gamma release assays
- sputum smear
- culture
- HIV infected persons
- contacts of patients with TB disease
- other immunocompromise (>15 mg prednisone/day)
- fibrotic change on CXR- old TB
5mm of induration
High pretest probablility cutoff
- No known risk factors
- age 4 or greater
15mm of induration
Low pretest probability
- recent immigrants from high prevalence areas
- injection drug users
- children < 4 years
- children and adolescents exposed to high risk adults
- residents and employees of prisons/jails, nursing homes, hospitals, underlying medical conditions etc
10mm of induration
what could cause a false negative tuberculin skin test
- general illness
- steroid therapy
- immunosuppression
- long duration of infection
- malnutrition
what causes false positives in tuberculosis?
- non-tuberculosis mycobacteria
- BCG vaccine does not cause more than 10mm of induration and a positive ppd should not be attributed to the BCG vaccine
- whole blood assay
- measures immune response to M. tb antigens
- no response to non-tuberculosis mycobacteria or BCG
- less subjective than TST
- not standardized for children < 5
- may be falsely negative in active disease; expensive
Quantiferon Gold active TB disease
indications for a sputum smear in TB?
- when PPD or IGRA is positive and CXR is abnormal
- not needed when PPD or IGRA positive and CXR is normal
- requires three specimens from separate days
- induced with saline under infection control precautions
- if patient cannot cooperate- gastic aspirates, or bronchioalveolar lavage
- requires about 10,000organisms/ ml to be psitive
Sputum smear
- Done is specialized labs on an body fluid or tissue
- gold standard
- special media- lowenstein jensen
- takes 1-8 weeks to grow
- molecular probes increase turnaround time
Culture
dx of TB
first line agents of TB?
- Isoniazid (INH)
- rifampim (RIF)
- pyrazinamide (PZA)
- ethambutol (EMB)
- streptomycin (STM)
Adverse events of Isoniazid?
- Rash, increased ALT/AST
- hepatitis, peripheral neruopathy (interferes with Vitamin B6 metabolism; presents with numbness and tingling
- mild CNS effects
- drug interactions: Dilantin, disulfuram
how should you monitor isoniazid?
- Baseline LFTS (monthly or more if abn or symptoms)
- hepatitis (risk increases with age, the risk increases with alcohol consumption)
- Vitamin B6- prevents neuropathy
Adverse effects of rifampin
- GI upset
- drug interactions
- hepatitis
- bleeding
- flu-like symptoms
- rash
- renal failure
- fever
- orange body fluids
monitoring of rifampin?
baseline LFTS, CPC, plts- adults
monthly if more abn or symtoms
adverse effects of Pyrazinamide
- Hepatitis
- rash
- GI upset
- joint aches
- hyperuricemia
- gout
monitoring of pyrazinamide?
- uric acid, LFTs baseline
- montly if abn or symptoms
- may make glucose control more difficult in diabetics
adverse effects of ethambutol and monitoring?
- optic neuritis
- rash
Monitoring
- baseline and monthly tests of visual acuity and color vision
adverse events and monitoring of streptomycin?
- ototoxicity
- renal toxicity
monitoring
- baseline hearing and renal function, repeat monthly
- avoid or reduce dose in adults > 60 yrs
- injectable only
Second line Tb agents
- rifapentene (related to rifampin)
- fluroquinolones
- ethionamide
- amikacin
- linezolid
mainly used with drug resistant TB
treatment of active TB in the initial 2 months and subsequent 4 months
Initial 2 months (given daily for 2 weeks per week for 6 weeks)
- INH
- RIF
- PZA
- EMB* OR STM*
Subsequent 4 months (given 2x per week)
- INH
- RIF
6 month duration
monitoring treatment of active disease?
- check sputum smear every two weeks until negative
- send isolate for susceptiblity testing
- if smear do not convert to negative suspect non-adherence or drug resistance
treatmet of latent LTBI?
Isoniaziad
- adults 300mg daily
- children 10mg/kg/day once daily
- 9 months duration
- pyridoxine (vitamin b6) if dietary risk
alternative treatment of latent TB
Rifampin daily for 4-6 months
INH + rifapentene (once weekly 3 months, DOT only)
Monitoring of latent TB infection
Monitoring
- adults- liver panel at baseline and prn during therapy
- children- Liver panel only if symptoms
Do not repeat PPD - will be positive for life
- Remain infectious until sputum converts to negative
- should remain at home
- wear mask when in public/clinic vistis
active disease
not infectious
no quarantine. or isolation precautions
latent TB
negative chest X-ray, asymptomatic
prevention of TB?
- screen all at risk patients with PPD
- identify cases of active disease
- trace contacts
- give close contacts prophylactic antibiotics
- treat cases of LTBI
- old fashion public health nursing
