MAC infection
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Questions and Answers

What does MAC stand for in the context of infectious diseases?

  • Mycoplasma Associated Condition
  • Mandatory Antibiotic Course
  • Microbial Airborne Contagion
  • Mycobacterium Avium Complex (correct)

In which patient population is Mycobacterium Avium Complex (MAC) infection most commonly observed, according to the text?

  • Children with cystic fibrosis
  • Individuals with diabetes
  • Persons with AIDS (correct)
  • Elderly patients with pneumonia

What immunological condition is indicated as a contributing factor to Mycobacterium Avium Complex (MAC) infection in the specified population?

  • Elevated levels of B lymphocytes
  • Reduced CD4+ T lymphocyte counts (correct)
  • Overproduction of antibodies
  • High CD8+ T lymphocyte counts

Considering the term 'aced-fast' presented alongside 'Mycobacterium avium complex', which microbiological staining property is most likely being alluded to, assuming a typographical error?

<p>Acid-fast staining characteristic (D)</p> Signup and view all the answers

If 'Lack aced-fast' is interpreted in the context of diagnostic microbiology and assuming 'aced-fast' refers to a staining property, what could 'Lack' imply regarding Mycobacterium Avium Complex (MAC)?

<p>MAC does not exhibit the typical staining property under standard conditions. (A)</p> Signup and view all the answers

In the context of opportunistic infections, what immunological threshold, specifically referring to CD4+ cell counts, is frequently linked to the manifestation of Mycobacterium Avium Complex (MAC)?

<p>CD4+ counts typically below 200 cells/µL (A)</p> Signup and view all the answers

What characteristic is implied by the descriptor 'Lack aced-fast' when describing Mycobacterium Avium Complex (MAC), assuming 'aced-fast' is a typographical error?

<p>The organism poorly retains carbolfuchsin dye after acid wash. (A)</p> Signup and view all the answers

Which of the following scenarios represents the MOST likely route of initial exposure to Mycobacterium Avium Complex (MAC) in susceptible individuals?

<p>Inhalation or ingestion of the organism from environmental sources. (D)</p> Signup and view all the answers

A researcher is investigating novel diagnostic markers for early detection of Mycobacterium Avium Complex (MAC) in immunocompromised patients. Which immunological assay would MOST directly assess the patient's ability to mount a cellular immune response against MAC?

<p>Lymphocyte proliferation assay using MAC antigens. (D)</p> Signup and view all the answers

A patient diagnosed with advanced HIV and disseminated Mycobacterium Avium Complex (MAC) is started on a combination of clarithromycin and ethambutol. Several weeks into treatment, the patient reports a significant decrease in visual acuity. Which potential drug-related adverse effect should be MOST immediately investigated?

<p>Ethambutol-induced optic neuritis. (D)</p> Signup and view all the answers

Which of the following scenarios is LEAST likely to result in tuberculosis transmission?

<p>A short conversation with a patient who has latent TB infection. (B)</p> Signup and view all the answers

A 42-year-old patient with advanced HIV (CD4+ count = 45 cells/µL) presents with fever, night sweats, weight loss, and diarrhea. Which clinical feature would BEST differentiate MAC infection from pulmonary tuberculosis?

<p>Systemic symptoms without prominent pulmonary involvement (D)</p> Signup and view all the answers

A patient with newly diagnosed active pulmonary tuberculosis is started on a regimen of Rifampin, Isoniazid, Pyrazinamide, and Ethambutol (RIPE). At the two-month follow-up, sputum smears remain positive. What is the appropriate next step?

<p>Extend the initial phase of treatment by one month. (D)</p> Signup and view all the answers

A 35-year-old healthcare worker receives a Tuberculin Skin Test (Mantoux test) with an induration of 11 millimeters after 48 hours. Which of the following best describes the interpretation?

<p>Positive, based on occupational risk exposure (D)</p> Signup and view all the answers

Which of the following would NOT cause a false-negative Tuberculin Skin Test?

<p>Prior BCG vaccination (A)</p> Signup and view all the answers

Which diagnostic feature is exclusive to ACTIVE pulmonary tuberculosis and NOT found in latent TB infection?

<p>Abnormal chest radiograph with upper lobe cavitation (C)</p> Signup and view all the answers

A 28-year-old patient with HIV presents with fever, lymphadenopathy, and rapid clinical deterioration. Which of the following would MOST strongly indicate disseminated TB rather than localized pulmonary TB?

<p>Positive bone marrow biopsy with granulomas (C)</p> Signup and view all the answers

Which mechanism allows Mycobacterium tuberculosis to establish an initial infection despite alveolar macrophage activity?

<p>Escape from alveolar macrophage microbicidal activity (D)</p> Signup and view all the answers

Which latent TB regimen is LEAST likely to cause hepatotoxicity in a 40-year-old patient with no underlying liver disease?

<p>Rifampin daily for 4 months (D)</p> Signup and view all the answers

A patient presents with fever, anorexia, hepatomegaly, and splenomegaly. Which diagnostic test is MOST likely to confirm miliary tuberculosis?

<p>Bone marrow biopsy with granulomas (A)</p> Signup and view all the answers

Which of the following individuals should NOT be routinely screened for tuberculosis?

<p>A person with a history of latent TB infection and negative chest radiograph (D)</p> Signup and view all the answers

During the initial phase of Mycobacterium tuberculosis infection, which of the following is TRUE?

<p>Tubercle bacilli reach the alveoli and are ingested by alveolar macrophages (D)</p> Signup and view all the answers

Which of the following diagnostic findings is REQUIRED to confirm Mycobacterium avium complex (MAC) infection?

<p>Identification of MAC from sputum cultures (D)</p> Signup and view all the answers

Which of the following is the LEAST likely cause of a false-positive Tuberculin Skin Test (TST)?

<p>Overwhelming TB disease (B)</p> Signup and view all the answers

Which of the following organ systems is LEAST commonly affected by extrapulmonary tuberculosis?

<p>Skin (A)</p> Signup and view all the answers

Which of the following characteristics is found in BOTH latent TB infection and active pulmonary TB?

<p>Positive tuberculin skin test or interferon-gamma release assay (IGRA) (D)</p> Signup and view all the answers

A patient with active pulmonary tuberculosis is undergoing treatment with the RIPE regimen. At the two-month mark, sputum smear results are negative. What is the NEXT appropriate step?

<p>Discontinue Pyrazinamide and Ethambutol, continue Rifampin and Isoniazid (D)</p> Signup and view all the answers

Which of the following is the most appropriate prophylactic measure to prevent MAC infection in an HIV patient with a CD4+ count of 40 cells/µL?

<p>No prophylaxis; initiate antiretroviral therapy (ART) (B)</p> Signup and view all the answers

Which of the following BEST describes the mechanism of resistance in multidrug-resistant tuberculosis (MDR-TB)?

<p>Mutations in the rpoB gene (Rifampin resistance) and katG gene (Isoniazid resistance) (C)</p> Signup and view all the answers

Which of the following is FALSE regarding the diagnosis of pulmonary tuberculosis?

<p>Chest radiograph is always abnormal in active pulmonary TB (D)</p> Signup and view all the answers

A 62-year-old patient with chronic kidney disease receives a Tuberculin Skin Test (TST) with an induration of 7 mm after 48 hours. How should this result be interpreted?

<p>Positive, due to underlying CKD (B)</p> Signup and view all the answers

Which of the following situations poses the HIGHEST risk for TB transmission?

<p>Sharing a classroom with a coughing student diagnosed with active pulmonary TB (B)</p> Signup and view all the answers

Which of the following is a unique adverse effect of Ethambutol in the treatment of tuberculosis?

<p>Optic neuritis (A)</p> Signup and view all the answers

Which of the following patients has the HIGHEST risk of reactivation of latent TB infection?

<p>A 50-year-old receiving TNF-alpha inhibitors for rheumatoid arthritis (C)</p> Signup and view all the answers

Which of the following findings would NOT support a diagnosis of Mycobacterium avium complex (MAC) infection?

<p>Positive tuberculin skin test (TST) with 10 mm induration (A)</p> Signup and view all the answers

Which of the following patients requires an EXTENDED duration of tuberculosis treatment beyond the standard 6 months?

<p>A patient with cavitary pulmonary TB and positive sputum culture at 2 months (C)</p> Signup and view all the answers

Which combination of drugs is recommended for treating Mycobacterium avium complex (MAC) infection until sputum cultures are negative for 12 months?

<p>Azithromycin + Rifampin + Ethambutol (C)</p> Signup and view all the answers

Which of the following mechanisms prevents the progression from latent TB infection to active disease in most individuals?

<p>Formation of granulomas by T cells and macrophages (B)</p> Signup and view all the answers

A patient is admitted to the hospital with suspected active pulmonary tuberculosis. Which of the following is the MOST important initial step?

<p>Isolate the patient in a negative-pressure room (A)</p> Signup and view all the answers

Which patient is MOST likely to have a FALSE-NEGATIVE Tuberculin Skin Test (TST)?

<p>A 6-month-old infant exposed to active TB (A)</p> Signup and view all the answers

A healthcare worker undergoes a Tuberculin Skin Test (TST) and shows an induration of 9 mm at 72 hours. Which of the following best describes this result?

<p>Negative, as induration is less than 10 mm (A)</p> Signup and view all the answers

Which of the following patients is LEAST likely to develop Mycobacterium avium complex (MAC) infection?

<p>An immunocompetent adult with no underlying health conditions (C)</p> Signup and view all the answers

Which of the following latent TB treatment regimens is preferred for patients at increased risk of hepatotoxicity?

<p>Rifampin daily for 4 months (D)</p> Signup and view all the answers

Which of the following statements is FALSE regarding the pathophysiology of tuberculosis?

<p>Latent TB patients can transmit the disease if they have a positive TST or IGRA (C)</p> Signup and view all the answers

Which of the following symptoms is more characteristic of Mycobacterium avium complex (MAC) than pulmonary tuberculosis?

<p>Systemic symptoms without pulmonary involvement (D)</p> Signup and view all the answers

An HIV patient with a CD4+ count of 150 cells/µL undergoes a Tuberculin Skin Test (TST) and shows an induration of 6 mm. What is the correct interpretation?

<p>Positive, due to immunocompromised status (B)</p> Signup and view all the answers

A chest X-ray of a patient with pulmonary tuberculosis is MOST likely to show which of the following?

<p>Apical consolidation with cavitary lesions (D)</p> Signup and view all the answers

Which genetic mutation is responsible for Rifampin resistance in multidrug-resistant tuberculosis (MDR-TB)?

<p>rpoB gene mutation (D)</p> Signup and view all the answers

Which of the following conditions is LEAST likely to cause a false-negative interferon-gamma release assay (IGRA) test?

<p>Previous BCG vaccination (D)</p> Signup and view all the answers

During MAC treatment with Azithromycin, Rifampin, and Ethambutol, which of the following should be monitored regularly to detect drug-related side effects?

<p>Visual acuity and color discrimination (D)</p> Signup and view all the answers

A 34-year-old patient presents with fever, night sweats, weight loss, and a productive cough. Which of the following tests provides a DEFINITIVE diagnosis of active pulmonary tuberculosis?

<p>Positive sputum culture for <em>Mycobacterium tuberculosis</em> (C)</p> Signup and view all the answers

Which of the following BEST explains why HIV patients with CD4+ counts below 50 cells/µL are at increased risk of Mycobacterium avium complex (MAC) infection?

<p>Decreased production of interferon-gamma weakens systemic defenses (B)</p> Signup and view all the answers

Which of the following individuals is at the LOWEST risk of transmitting tuberculosis?

<p>A healthcare worker recently diagnosed with latent TB infection (C)</p> Signup and view all the answers

Which of the following patients should NOT receive Pyrazinamide as part of their initial TB treatment regimen?

<p>A 60-year-old patient with chronic liver disease (C)</p> Signup and view all the answers

A patient diagnosed with disseminated Mycobacterium avium complex (MAC) is started on Azithromycin, Rifampin, and Ethambutol. How long should treatment continue after sputum cultures become negative?

<p>12 months (B)</p> Signup and view all the answers

Which of the following clinical features is MORE characteristic of miliary tuberculosis than pulmonary TB?

<p>Hepatomegaly, splenomegaly, and lymphadenopathy (D)</p> Signup and view all the answers

Which of the following processes allows Mycobacterium tuberculosis to evade destruction by alveolar macrophages during initial infection?

<p>Inhibition of lysosomal fusion with the phagosome (A)</p> Signup and view all the answers

Which of the following is TRUE regarding the interferon-gamma release assay (IGRA)?

<p>It is more specific than the Tuberculin Skin Test (TST) (C)</p> Signup and view all the answers

Flashcards

Mycobacterium Avium Complex (MAC)

Group of closely related mycobacteria, including M. avium and M. intracellulare.

Acid-fast Stain

A staining procedure used to identify acid-fast bacteria, like Mycobacterium.

Typical MAC occurrence

MAC typically manifests in individuals with compromised immune systems.

CD4+ Counts

Refers to the count of CD4+ T cells, a measure of immune function.

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MAC and AIDS

Individuals with AIDS are highly susceptible to MAC infection.

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Acid-fast Bacteria

Bacteria that retain dye after acid washing, indicating a unique cell wall structure.

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AIDS

Advanced stage of HIV infection characterized by a severely compromised immune system.

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CD4+ Cells

Immune cells crucial for fighting infection; their count indicates immune system strength.

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Latent TB

Non-contagious form of TB. Cannot be spread to others.

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MAC: Systemic Symptoms

Systemic illness common with MAC, impacting multiple organs, unlike pulmonary-focused TB.

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TB Treatment Extension

Extend the initial treatment phase by 1 month.

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TST Positive (Healthcare)

Induration ≥10 mm is positive in healthcare workers.

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BCG & TST Results

BCG causes false positives, not negatives.

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Active TB Feature

Upper lobe cavitations are specific to active TB.

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Miliary TB Confirmation

Bone marrow granulomas indicate systemic dissemination, miliary TB.

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TB's Initial Evasion

TB bacteria evade destruction by alveolar macrophages.

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Least Toxic TB Regimen

Rifampin monotherapy has the lowest liver toxicity risk.

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Miliary TB Test

Essential to confirm hematogenous dissemination of TB.

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TB Screening Exceptions

Not needed for latent TB history unless symptomatic.

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TB Infection Start

Macrophages ingest bacilli, a step in primary infection.

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Confirms MAC

Requires isolation from sputum cultures, unlike AFB smear alone.

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Overwhelming TB effect

Overwhelming TB causes false negatives, not positives.

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Rare TB Locations

Skin is least common site of extrapulmonary TB.

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Latent and Active Link

Both have positive TST or IGRA, showing TB exposure.

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TB 2-Month Shift

Shift to Rifampin & Isoniazid after negative smears.

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MAC Prevention Update

Initiate ART now, no prophylaxis for MAC needed.

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MDR-TB Resistance

Mutations in rpoB (Rifampin) and katG (Isoniazid).

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Pulmonary TB & CXR

Abnormal CXR not always present, especially early.

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TST Positive (CKD)

≥5 mm is significant due to CKD risk.

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Highest TB Risk

Prolonged contact with active, untreated TB cases.

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Ethambutol Side Effect

Ethambutol and optic neuritis are correlated.

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Reactivation Risk (TNF)

TNF-alpha inhibitors impair granulomas, increase TB risk greatly.

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MAC

MAC requires culture identification.

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Extended TB Tx

9-month treatment needed for cavitary disease.

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MAC Treatment Combo

Azithromycin + Rifampin + Ethambutol regimen is needed until it cultures.

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TB Latency Mechanism

Granuloma formation prevents active TB.

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Hospital TB Control

Airborne transmission must be controlled.

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Infant False Negative (TST)

Immature system causes test to not be accurate.

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TB Transmission Risk

Brief conversations with individuals with latent TB are LEAST likely to transmit the disease.

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MAC vs. TB Symptoms

Systemic symptoms without pulmonary involvement best differentiate MAC from pulmonary TB.

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TB Treatment Adjustment

Extending the initial phase of treatment by one month is appropriate when sputum smears remain positive at two months.

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TB Pathophysiology - Initial Phase

Tubercle bacilli reach the alveoli and are ingested by alveolar macrophages during the initial phase.

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MAC Diagnosis - Required Finding

Definitive MAC diagnosis requires isolation of the organism from sputum cultures.

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TST - False Positives

Overwhelming TB disease can cause false-negative results, not false positives.

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Extrapulmonary TB - Rare Site

Skin is the LEAST common organ systems affected by extrapulmonary tuberculosis.

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TB Treatment Monitoring

Treatment shifts to continuation phase using Rifampin and Isoniazid after two months with negative smears.

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HIV - MAC Prophylaxis

Current guidelines no longer recommend MAC prophylaxis if ART is promptly initiated in patients with low CD4+ counts.

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Drug Resistance in TB

MDR-TB is primarily due to genetic mutations affecting targets of Rifampin and Isoniazid.

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Pulmonary TB Diagnosis

Some patients may have normal chest X-ray findings in active TB, particularly early in the disease.

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TB Prophylaxis in HIV

For HIV patients, a TST induration of ≥5 mm is considered positive due to their immunocompromised state.

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TB - Risk for Transmission

Prolonged, close contact with an untreated, actively infectious TB patient poses the highest transmission risk.

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Toxicity

Ethambutol is specifically associated with optic neuritis, causing blurred vision.

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Risk Factors for MAC

MAC primarily impacts immunocompromised people.

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TB Skin Test result

Induration of < 10 mm is considerd negative.

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Rifampin - Isoniazid - Pyrazinamide - Ethambutol

Treatment is based on four-drug treatment Regimen

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TB Latent Infection

Rifampin monotherapy for 4 months has a lower risk of hepatotoxicity compared to INH regimens.

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False Pathogology

Latent patients do not have this as a symptom.

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Is it MAC or is it Pulmonary??

Systemic ailments are more related to MAC than other afflictions.

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Lungs are the key...

Lung health needs to be considered when diagnosing MAC.

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TNF

Autoimmune diseases need to be watched for as well.

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MAC identification is key

Must confirm with culture indentification before deciding on a path.

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Check this often...

Check if patient has cavitary as well as negative test results.

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MAC, time to watch close...

Check and make sure azithromycin has been working

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Graulomas

Make sure granuloma has been contained or else you will be sad...

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Act Fast if you suspect!

When suspected act fast!

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Kids weak.

False negatives happen when kids aint immune yet..

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Healthcare Worker

Induration is less than 10 mm, so therefore is negative.

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Study Notes

Mycobacterium Avium Complex (MAC)

  • Acid-fast bacilli are associated with MAC.

Screening for Tuberculosis

  • Routine screening is not required for individuals with previously diagnosed latent TB, unless symptomatic or immunocompromised.

Tuberculin Skin Test (TST) Interpretation

  • In patients with conditions such as chronic kidney disease (CKD) that increases TB risk, an induration of >=5 mm is considered positive.
  • Healthcare workers are considered positive if the induration is >=10 mm; 9mm is classified as negative.

False positives

  • Overwhelming TB disease can cause false-negative results and not false positives, unlike prior BCG vaccinations, incorrect administration, or infections with non-tuberculous mycobacteria.
  • Prior BCG vaccination can cause false positives, but not false negatives.

Interferon-gamma release assay (IGRA)

  • Is more specific than the Tuberculin Skin Test (TST).

Workup and Diagnosis

  • Chest radiograph is not always abnormal in active pulmonary TB, it can be normal in some patients, particularly early in the disease.

Miliary TB

  • Bone marrow biopsy is essential for confirming hematogenous dissemination.

Drug Resistance

  • Multidrug-resistant tuberculosis (MDR-TB)'s mechanism of resistance best described as mutations in the rpoB gene (Rifampin resistance) and katG gene (Isoniazid resistance).
  • Rifampin resistance primarily occurs through mutations in the rpoB gene.
  • Extensively drug-resistant tuberculosis (XDR-TB) is resistance to Isoniazid, Rifampin, and at least one fluoroquinolone.

Treatment for Pulmonary TB

  • After two months with negative smears, treatment shifts to the continuation phase, using Rifampin and Isoniazid, per standard guidelines.

Risk Factors

  • The individual least likely to develop Mycobacterium avium complex (MAC) infection is an immunocompetent adult with no underlying health conditions.

TB Transmission

  • The scenario least likely to result in tuberculosis transmission is a short conversation with a patient who has latent TB infection.
  • The individual at the lowest risk of transmitting tuberculosis is a healthcare worker recently diagnosed with latent TB infection
  • Sharing a classroom with a coughing student diagnosed with active pulmonary TB poses the highest risk for TB transmission.

Reactivation Risk

  • The patient with the highest risk of reactivation of latent TB infection is one receiving TNF-alpha inhibitors for rheumatoid arthritis.

Drug Toxicities

  • Optic neuritis is a unique adverse effect of Ethambutol, which also can cause blurred vision or color blindness.

Treatment Duration

  • The patients that require an extended duration of tuberculosis treatment beyond the standard 6 months are patients with cavitary pulmonary TB and a positive sputum culture at 2 months.

MAC Treatment Regimen

  • The combination of drugs for treating Mycobacterium avium complex (MAC) infection until sputum cultures are negative for 12 months is Azithromycin + Rifampin + Ethambutol.

TB Pathophysiology

  • Mycobacterium tuberculosis is able to establish an initial infection despite alveolar macrophage activity, because it can escape from their microbicidal activity
  • During the initial phase of Mycobacterium tuberculosis infection, tubercle bacilli reach the alveoli and are ingested by alveolar macrophages.
  • The primary mechanism by which Mycobacterium tuberculosis establishes infection in the lungs is escape from alveolar macrophage microbicidal activity.
  • Granulomas, containing T cells and macrophages, limit bacterial replication, thus preventing progression to active TB during latency.

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Description

Mycobacterium Avium Complex (MAC) infection is most commonly observed in immunocompromised patients, particularly those with HIV/AIDS. The text describes MAC and its relevance to patient populations with immunological conditions. It also touches on microbiological staining properties.

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