7 TB Histo Cocci Flashcards
Number one killer of HIV+ patients
TB
TB is transmitted through …
Airborne droplet nuclei
Expelled with coughing, sneezing, shouting, singing
Transmission occurs when inhaled nuclei reach alveoli
Can a drunk hobo give you TB by coughing on you as you walk past?
No - usually requires prolonged exposure - someone you live with or residents of prisons, nursing homes, etc
95% of TB infections are…
Latent
TB bacteria present in the body without symptoms
Macrophages ingest tubercle bacilli creating barrier shell called a granulomatous - can see on CXR
Unable to transmit infection to others
Latent TB may activate to disease state if pt becomes immunocompromised and granulomas break open
____% initially develop TB disease within 2 years after infection and another ____% develop from latency later (reactivation TB)
5% and 5% - for a total of 10% exposed healthy individuals have lifetime risk of getting active TB
TB only becomes active if immune system unable to fight infection
Without treatment, the risk of developing TB disease once infected is ________ for people with HIV
100x higher
Without treatment, the risk of developing TB disease once infected is ______ for diabetics
3X higher
Main TB risk factors
Immunocompromised (HIV, kids<5, DM, Silicosis, malnutrition, substance abuse, immunosuppressive therapy)
Immigrants from areas with high TB prevalence
Injection Drug Users
Close living quarters (nursing homes, institutions, correctional facilities, hospitals)
Main Sx of TB
Fever
Cough (3+ weeks, +/- productive, +/- hemoptysis)
CP (pleuritic or retrosternal)
Other Sx: weakness, weight loss, anorexia, chills, night sweats, dyspnea
Extrapulmonary TB disease Sx depends on location
Classic physical exam finding for TB
POSTTUSSIVE CRACKLES
PE may be normal
May also have dullness or decreased fremitius if pleural thickening
LAD
Clubbing if more severe
How is the Mantoux TST given?
Intradermal injection, create wheal with 0.1 ml Purified Protein Derivative
Read in 48-72 hours and measure INDURATION, not redness
5 mm is a positive TST response in ..
HIV+ persons Recent contacts of those with active TB Persons with evidence of TB on CXR Immunosuppressed patients (ie chronic steroids) Organ transplant patients
10 mm is a positive TST in …
Recent immigrants from countries with high rates of TB infection
HIV negative IVDUs
Mycobacteriology lab personnel
Residents/employees of high risk congregate settings
Persons with certain high risk medical conditions
Children <4
Children and adolescents exposed to high risk adults
Positive TST result in anyone without risk factors for TB
15 mm
2 step TST is recommended as initial test for …
Health care workers and individuals requiring periodic testing
1st negative, repeat in 1-3 weeks
2nd positive, TB infection present (creates boosted response and is likely due to past exposure)
What might cause a false positive on TST?
BCG (bacillus Calmette-Guerin) vaccine
Test that measures immune response in blood to TB
IGRA: Quantiferon-TB Gold and T-SPOT TB
Blood incubated with TB antigen and response measured
When might you use QuantiFeron-TB Gold instead of TST?
Concerns of patient not returning for reading
Patients who received BCG vaccination
Why don’t we just use the Quantiferon-TB gold test for everyone?
Expensive
CXR findings in Primary active TB
Initial: Hilar LAD or normal
May progress with pleural effusions and/or infiltrates
Cavities seen with progressive pulmonary TB
May also see miliary pattern
CXR helpful but cannot determine active vs inactive disease
Why is calcification a good thing when reviewing CXR of suspected TB patient?
Dense nodules or lesions indicate latent disease, less likely to reactivate
Signs of reactivation of TB on CXR
Cavities, infiltrates, and possible LAD
CXR abnormalities usually appear in ….
Apical/posterior upper lobes (80-90%) or superior areas of lower lobe
What is the Ranke Complex?
Indicates healed primary pulmonary TB
Ghon lesion (Focus): calcified parenchymal granulomatous (tuberculoma)
Ipsilateral calcified hilar lymph nodes
How do you do sputum collection for TB Dx?
3 specimens, at least 8-24 hours apart
At least one first thing in the morning
What are the three methods for analyzing sputum in possible TB cases?
- Smear (acid fast bacilli - AFB) - quick and easy, supports Dx but not confirmatory
- Cytology (nuclei acid amplification - NAA) takes 48 hours, supports Dx but does not confirm
- Culture - GOLD STANDARD; confirms Dx but takes weeks
If Smear and Cytology positive, begin Tx while waiting for Culture
Once TB culture is positive, what do you do?
Drug susceptibility testing
If culture is negative and TB disease still suspected, what do you do?
Treat anyway and monitor response to treatment
If you do a biopsy for TB, what will you see?
Necrotizing (caseating) granulomas
What are these new fangled Xpert MTB/RIF Assays?
Automated NAA test using disposable cartridges - can ID M tuberculosis DNA and rifampin resistance
Takes only 2 hours and requires minimal training but its expensive and doesn’t replace AFB smear or culture
Treatment of Active TB
Isolated, negative pressure inpatient hospital room
Direct Observed Therapy (DOT)
“RIPE” drugs Rifampin Isoniazid Pyrazinamide Ethambutol
Rifampin side effects
Excreted as red-orange compound in tears, sweat, urine
Skin sensitivity
Isoniazid side effects
Hepatotoxicity (monitor LFTs)
Peripheral Neuropathy: Vitamin B6 may be given
Fatal hepatitis (pregnant women at increased risk)
Pyrazinamide side effects
Hepatotoxicity
Hyperuricemia
Ethambutol side effects
Optic neuritis: test visual acuity and color vision
How are the RIPE drugs administered?
Initial (intensive) phase: 4 meds daily x 2 months (DOT)
Repeat CXR, AFB smear, and culture
Continuation phase: RIF and INH daily or twice weekly x 4 months (may be extended based on sputum culture and med tolerance
Treatment considerations for special cases
HIV: extends treatment 9-12 months (intermittent dosing)
Pregnant women: No PZA given
Infants/children: EMB not given and may extend treatment
Criteria to not be considered infectious for TB
2 weeks of treatment
3 negative sputum smears
Symptoms improve
Who can go home while still infectious?
Those who can strictly follow up and have DOT arranged
No children < 5 or immunocompromised individuals in home
Unable to travel except to healthcare visits
How is latent TB treated?
9 month regiment of Isoniazid 300mg daily or 900mg twice weekly using DOT (this is preferred therapy for pregnant women and children 2-11 - but monitor LFTs)
New preferred regime for adults and children ≥ 12: Combined INH and Rifapentine for 12 weekly doses (NOT used in pregnancy)
How is MDR-TB defined?
Does not respond to at least INH and RIF
Causes: inadequate meds or dosing, premature treatment interruption, spontaneous genetic mutation
How is XDR-TB defined
Extensively drug resistant TB, responds to even fewer drugs including fluoroquinolone
Surgery to remove necrotic tissue important but often not available
What is the purpose of the BCG vaccine
To decrease risk of severe consequences due to TB
Does not prevent primary infection or activation of latent TB
Proven to protect against meningitis and disseminated TB in kids though
Given as single dose at birth in developing countries
Fungal infection associated with soil contaminated with bird or bat droppings
Histoplasmosis
Occurs most frequently in OH and Mississippi River valleys (midwestern states)
Most common among individuals with HIV/AIDs or other weakened immune systems
Clinical presentation of histoplasmosis
Hx of SPELUNKING, construction, demolition, mining, roofing, farming, gardening, installing AC units
Incubation period is 3-17 days after exposure
90% asymptomatic or mild flu-like symptoms
Most symptoms resolve in few weeks to a month unless infection becomes more severe
50-90% of pt with histoplasmosis are …
Asymptomatic
CXR may show residual granuloma
What is acute symptomatic pulmonary histoplasmosis?
Fever and marked fatigue, few respiratory symptoms
Symptoms extend from 1 week to 6 months
Mild Sx are typically self-limited
Progressive disseminated histoplasmosis occurs in …
Immunocompromised patients
Fever, marked fatigue, cough, dyspnea, weight loss
Multiple organ involvement
Fatal within 6 weeks
Chronic pulmonary histoplasmosis occurs in…
Older COPD patients and those with progressive lung changes (apical cavities)
Dx of histoplasmosis is usually via…
Serology
Antibody tests (Immunodiffusion (ID) and Complete Fixation (CF) tests
Antigen detection via enzyme immunoassay (EIA test) - can be either urine or serum testing
CXR findings for histoplasmosis
Hilar adenopathy
Patchy or nodular infiltrates in lower lobes
Treatment for histoplasmosis
Acute mild to moderate - no treatment
Others - either an azole or Ampho B if pregnant
Fungal infection endemic to lower deserts of Western Hemisphere
Coccidioidomycosis (Valley Fever)
Inhalation of spores from contaminated soil - outbreaks occur following dust storms and earthquakes
Clinical presentation of Cocci
Lives or recently traveled to SW
Activities increasing exposure: excavation, construction, playing in the dirt (dogs can get it too)
Incubation 1-3 weeks
60% asymptomatic
More severe presentation in immunocompromised, pregnant women, DM, African and Filipinos
Sub-acute valley fever
Mild respiratory Sx that are self-limited and last weeks to months - may be considered protective from future disease
Symptoms of primary Cocci infection
Typically present with community acquired pneumonia 7-21 days following exposure
Primary Sx: Fever, cough, pleuritic CP
Others: Marked fatigue, HA, arthralgia, erythema multiform, erythema nodosum
Sx of disseminated disease in Cocci patients
Has spread to Lungs Bones or Brain
Higher Risk: HIV, African or Filipino descent, 3rd trimester of pregnancy
More pronounced lung findings (ie abscess)
Bone lesions
Lymphadenitis, meningitis
Lab findings in Cocci
Eosinophils with slight leukocytosis
CXR findings vary in cocci but include…
Hilar LAD
Patchy, nodular pulmonary infiltrates
Miliary infiltrates
Thin wall cavities
Treatment of cocci not generally required but for patients who are high risk or have severe illness…
Symptomatic therapy = -azole
Ampho B if severe or pregnant
Prognosis = good with limited disease, but 50% mortality if disseminated
Think cocci when …
Pulmonary complaints and one or more of the 3 Es:
Erythema nodosum
Erythema multiforme
Eosinophilia
