L.11 Mycobacterium Tuberculosis Flashcards
(98 cards)
1
Q
What remains the leading cause of death from a single infectious agent worldwide?
A
Tuberculosis (TB)
This statistic highlights the significant impact of TB on global health.
2
Q
How many new cases of TB were estimated globally in 2020?
A
10 million
This number indicates the ongoing prevalence of TB despite global health efforts.
3
Q
What was the estimated number of deaths attributed to TB in 2020?
A
1.4 million
This figure includes both HIV-positive and HIV-negative individuals.
4
Q
What percentage of those infected with TB were co-infected with HIV?
A
8.2%
This highlights the increased risk associated with immunosuppression.
5
Q
Approximately how many people developed rifampicin-resistant TB (RR-TB)?
A
500,000
RR-TB is concerning due to its resistance to a powerful first-line anti-TB drug.
6
Q
What percentage of individuals with RR-TB were confirmed to have multidrug-resistant TB (MDR-TB)?
A
78%
MDR-TB is defined as resistant to at least rifampicin and isoniazid.
7
Q
What percentage of new TB cases exhibited either MDR-TB or RR-TB?
A
3.3%
This statistic is significant for understanding drug resistance trends.
8
Q
What is the key characteristic of Mycobacterium spp.?
A
Acid-fastness
This property allows them to resist decolorization with dilute acid-alcohol.
9
Q
How many species of Mycobacterium have been identified?
A
Over 90 species
This diversity includes both pathogenic and non-pathogenic species.
10
Q
Name one primary human pathogen of the Mycobacterium genus.
A
Mycobacterium tuberculosis
This species is responsible for the majority of TB cases.
11
Q
What are the zoonotic species of Mycobacterium that cause TB?
A
Mycobacterium bovis subsp. bovis and caprae
These species can be transmitted from animals to humans.
12
Q
What does MTC stand for in Mycobacterium nomenclature?
A
Mycobacterium tuberculosis Complex
This complex includes several species, such as M. tuberculosis and M. bovis.
13
Q
What does NTM stand for?
A
Non-Tuberculous Mycobacteria
These are environmental species, including M. avium and M. kansasii.
14
Q
What is the unique cell wall structure of Mycobacterium tuberculosis central to?
A
The pathogen’s resistance and pathogenicity
The unique structure allows for high lipid content, contributing to hydrophobic and waxy characteristics.
15
Q
What are the main components of the Mycobacterium tuberculosis cell wall?
A
- Peptidoglycan layer interwoven with complex lipids
- Up to 60% lipid content
The high lipid content is crucial for its impermeability and resistance.
16
Q
What role do mycolic acids play in Mycobacterium tuberculosis?
A
They contribute to impermeability and acid-fastness
Mycolic acids are long-chain fatty acids that enhance the bacterium’s protective features.
17
Q
What is the function of the cord factor (trehalose dimycolate) in Mycobacterium tuberculosis?
A
It inhibits neutrophil migration and induces granuloma formation
This factor is a key virulence determinant.
18
Q
What is Wax-D associated with in Mycobacterium tuberculosis?
A
Immunogenicity
Wax-D contributes to the immune response against the bacterium.
19
Q
What does the cell wall of Mycobacterium tuberculosis provide resistance to?
A
- Decolourisation by acids
- Disinfectants and harsh environmental conditions
- Many antimicrobials due to poor drug penetration
- Host immune responses
This resistance is critical for the survival of the pathogen in hostile environments.
20
Q
What is the causative agent of tuberculosis?
A
Mycobacterium tuberculosis
It is classified as an acid-fast bacillus.
21
Q
How is tuberculosis primarily transmitted?
A
Through aerosolised droplets
Activities like coughing, sneezing, and speaking can spread the bacteria.
22
Q
What are typical symptoms of pulmonary tuberculosis?
A
- Persistent chronic cough (lasting >3 weeks)
- Haemoptysis (coughing up blood)
- Drenching night sweats
- Unintentional weight loss
- Fever (pyrexia)
These symptoms are indicative of active pulmonary TB.
23
Q
What organ systems can extra-pulmonary tuberculosis affect?
A
- Lymph nodes (scrofula)
- Central nervous system (TB meningitis)
- Bones and joints (Pott’s disease)
- Genitourinary system
TB can disseminate to virtually any part of the body.
24
Q
What is miliary tuberculosis?
A
Widespread dissemination via the bloodstream
This form of TB is often severe and life-threatening.
25
What percentage of the global population is thought to carry latent tuberculosis infection?
~1/3
## Footnote
Individuals with latent TB are asymptomatic but may reactivate the disease.
26
What percentage of latent TB carriers progress to active disease?
Approximately 10%
## Footnote
This progression typically occurs if immunity wanes.
27
What are the methods for preventing tuberculosis?
* BCG vaccine
* Public health measures
## Footnote
These strategies are essential for controlling the spread of TB.
28
How is tuberculosis treated?
Standardised multi-drug therapy for at least 6 months
## Footnote
Effective treatment is critical for curing TB and preventing its spread.
29
What region has the highest burden of tuberculosis?
South-East Asian Region, particularly India and Indonesia
## Footnote
The African Region also has a significant burden, especially due to HIV-TB co-infection.
30
What are some social determinants that increase TB risk?
* Poverty
* Overcrowding
* Malnutrition
* HIV infection
## Footnote
These factors significantly contribute to the spread and severity of tuberculosis.
31
What is the WHO’s goal for TB deaths by 2030?
90% reduction
## Footnote
This goal is part of the End TB Strategy.
32
Name a risk factor for tuberculosis related to exposure.
Exposure to person with active tuberculosis
## Footnote
Close contact with an infected individual increases the risk.
33
What health conditions are risk factors for tuberculosis?
* Leukaemia
* Hodgkin's Disease
* Diabetes mellitus
* Alcoholism
* IV drug abuse
## Footnote
These conditions can impair the immune system and increase susceptibility.
34
What nutritional factors are associated with an increased risk of tuberculosis?
* Malnutrition
* Low body weight
* Vitamin D deficiency
## Footnote
These factors can weaken the immune response.
35
How does smoking relate to tuberculosis risk?
Smoking increases the risk of tuberculosis
## Footnote
It can damage lung tissue and impair the immune response.
36
What is primary tuberculosis?
Initial infection following exposure to M. tuberculosis
## Footnote
It typically affects the lungs and can involve regional lymph nodes.
37
What is the Ghon complex?
Involvement of regional lymph nodes in primary tuberculosis
## Footnote
This complex is a sign of the body's immune response to TB infection.
38
What happens in most healthy individuals after primary tuberculosis infection?
The immune system contains the infection, leading to latent TB
## Footnote
This means the individual is asymptomatic and non-infectious.
39
What characterizes progressive primary tuberculosis?
Immune system fails to control the primary infection
## Footnote
It is more common in young children, the elderly, or immunocompromised individuals.
40
What can latent tuberculosis do if the immune system weakens?
Can reactivate
## Footnote
Conditions like HIV or diabetes can trigger reactivation.
41
What is secondary (reactivation) tuberculosis?
Reactivation of latent TB, often after years or decades
## Footnote
It typically affects the apical regions of the lungs.
42
What are common symptoms of secondary tuberculosis?
Chronic pulmonary symptoms and high infectivity
## Footnote
This form of TB can lead to severe health complications.
43
What are the primary symptoms of Pulmonary Tuberculosis?
Chronic cough, haemoptysis, night sweats, weight loss, fever
## Footnote
These symptoms are key indicators for the diagnosis of pulmonary tuberculosis.
44
What does a positive Tuberculin Skin Test (TST) indicate?
Previous infection or BCG vaccination
## Footnote
The Mantoux test involves an intradermal injection of purified protein derivative (PPD).
45
What do Interferon Gamma Release Assays (IGRAs) measure?
Immune response (IFN-γ production) to M. tuberculosis antigens
## Footnote
IGRAs are blood tests not affected by BCG vaccination.
46
What can a Chest X-ray assess in relation to tuberculosis?
Pulmonary involvement, e.g., cavitary lesions, consolidation, or miliary pattern
## Footnote
Chest X-rays are essential in evaluating the extent of disease.
47
What is the purpose of Ziehl-Neelsen staining in tuberculosis diagnosis?
Microscopy for Acid-Fast Bacilli
## Footnote
This technique is used to identify M. tuberculosis in specimens.
48
What are Nucleic Acid Amplification Tests (NAAT) used for?
Detecting M. tuberculosis (e.g., Xpert MTB/RIF assay)
## Footnote
NAATs provide rapid results for tuberculosis diagnosis.
49
What types of specimens are collected for diagnosing tuberculosis?
Pulmonary specimens, urine, pleural fluid, joint fluid, cerebrospinal fluid, tissue samples
## Footnote
Correct sampling is critical for accurate diagnosis.
50
What are the consequences of poor specimen quality in tuberculosis diagnosis?
False negatives, poor culture recovery, lack of identification and susceptibility results
## Footnote
Ensuring high-quality specimens is essential for accurate testing.
51
What is the hazard group classification of M. tuberculosis?
Hazard Group 3 pathogen
## Footnote
This classification indicates a higher risk and the need for containment measures.
52
What laboratory safety measures are required when handling M. tuberculosis?
Avoidance of aerosol generation, use of sealed buckets for centrifugation, preliminary disinfection with hypochlorite, routine Mantoux testing and BCG vaccination for lab staff
## Footnote
These measures help prevent laboratory-acquired infections.
53
Fill in the blank: M. tuberculosis requires work to be conducted in a _______ laboratory.
Containment Level 3
54
What are the three types of macroscopic grading in specimen processing?
* Bloodstained
* Purulent
* Mucosalivary
## Footnote
These categories help in the initial assessment of the specimen's characteristics.
55
What is the purpose of homogenisation and decontamination in specimen processing?
To eliminate commensals while preserving mycobacteria.
## Footnote
2% NaOH is used for decontamination, targeting a contamination rate of 2-5%.
56
What is the principle behind acid-fast staining?
Mycobacteria retain primary stain after acid-alcohol decolourisation.
## Footnote
This property is crucial for identifying mycobacterial infections.
57
What are the two methods of acid-fast staining mentioned?
* Ziehl-Neelsen staining
* Auramine-rhodamine fluorescent staining
## Footnote
Both methods are used to detect the presence of mycobacteria.
58
What is an advantage of acid-fast staining?
Rapid and cost-effective results available within one working day.
## Footnote
This makes it a practical choice for initial diagnosis.
59
What is a limitation of acid-fast staining?
Requires ~10,000 organisms/mL for detection.
## Footnote
This can lead to false negatives in cases with lower bacterial loads.
60
What does an AFB positive smear suggest?
High infectivity and active pulmonary TB.
## Footnote
This result necessitates immediate public health actions.
61
What does an AFB negative smear indicate?
Lower infectivity but does not rule out TB.
## Footnote
Clinicians should consider further testing in these cases.
62
What is the role of microscopy in TB diagnosis?
* Determining the need for patient isolation
* Influencing the scope of contact tracing
* Monitoring response to treatment
## Footnote
Microscopy plays a critical role in managing TB outbreaks.
63
What is considered the gold standard for TB diagnosis?
Culture of Mycobacterium tuberculosis.
## Footnote
Culturing provides definitive evidence of infection.
64
What is the limit of detection for smear microscopy?
~10,000 CFU/mL.
## Footnote
This limit may affect the sensitivity of the test.
65
What is the limit of detection for culture?
10–100 CFU/mL.
## Footnote
Culturing is more sensitive than smear microscopy.
66
Which medium is egg-based and inhibits contaminants?
Lowenstein-Jensen (LJ) medium.
## Footnote
This medium is widely used for growing M. tuberculosis.
67
What enhances the growth of M. tuberculosis in Lowenstein-Jensen medium?
Glycerol.
## Footnote
Glycerol is an essential component for optimal growth.
68
What is the purpose of the PANTA antibiotic cocktail?
Suppresses non-mycobacterial contaminants.
## Footnote
Ensures the growth of mycobacteria without interference from other organisms.
69
What is a benefit of using liquid media like Middlebrook 7H9 broth?
Faster growth compared to solid media.
## Footnote
This speed is critical for timely diagnosis.
70
What is a disadvantage of automated systems for TB culture?
Risk of mixed cultures and contamination.
## Footnote
Care must be taken to ensure accurate results.
71
Name one automated system used for mycobacterial culture.
* MGIT (Mycobacterial Growth Indicator Tube)
* BACTEC 9000
* MB BacT
## Footnote
These systems are designed to enhance sensitivity and reduce time to positivity.
72
What is the incubation period for Automated Fluorescent Detection Systems like the MGIT 960 system?
Up to 6 weeks; median positivity is around 10–12 days
## Footnote
The MGIT 960 system is a widely used automated culture system for detecting mycobacterial infections.
73
What principle does the MGIT 960 system use for detection?
A fluorescent oxygen sensor detects changes in oxygen levels due to respiring mycobacteria consuming oxygen
## Footnote
As oxygen decreases, the sensor emits fluorescent light under UV exposure.
74
What are the staining methods used in microscopy for culture positive confirmation?
* Auramine O (fluorescent)
* Ziehl-Neelsen (ZN) (acid-fast stain)
## Footnote
These staining methods help visualize mycobacteria in clinical samples.
75
What is the purpose of the MGIT TBc Assay?
Rapid confirmation of M. tuberculosis complex
## Footnote
This assay is part of immunochromatographic methods used for confirming tuberculosis.
76
What does the GeneXpert MTB/RIF Ultra Assay detect?
M. tuberculosis DNA and rifampicin resistance (rpoB gene mutations)
## Footnote
This is a molecular detection technique that provides rapid results.
77
What is the limit of detection for Xpert MTB/RIF Ultra?
15.6 CFU/ml (high sensitivity)
## Footnote
This indicates the assay's ability to detect low levels of the bacterium.
78
What are Line Probe Assays (LPAs) used for?
* Differentiating members of M. tuberculosis complex
* Detecting non-tuberculous mycobacteria (NTM)
* Drug resistance profiling
## Footnote
LPAs can be performed directly on clinical specimens or culture isolates.
79
True or False: The MGIT 960 system requires extensive hands-on time for operation.
False
## Footnote
The MGIT 960 system is designed for minimal hands-on time.
80
Fill in the blank: The culture positive confirmation step involves _______.
Microscopy
## Footnote
Microscopy is a critical step to confirm positive cultures visually.
81
What is the role of molecular methods in tuberculosis diagnosis?
Used for confirmation and resistance testing
## Footnote
Molecular methods provide rapid and accurate results compared to traditional cultures.
82
What is the purpose of susceptibility testing in tuberculosis?
To guide treatment after initial positive culture
## Footnote
Susceptibility testing helps determine the most effective medications based on the strain's resistance profile.
83
What are the two main categories of methods used for susceptibility testing?
Molecular Methods and Culture Methods
## Footnote
Culture methods include liquid media systems and solid media.
84
What is the key advantage of molecular methods for susceptibility testing?
Rapid results within hours to 1 day
## Footnote
This speed allows for quicker treatment decisions.
85
Name one molecular method used for testing rifampicin resistance.
GeneXpert
## Footnote
GeneXpert provides rapid molecular results.
86
What is the principle of the MGIT 960 System?
Growth comparison between drug-containing and drug-free tubes based on fluorescence
## Footnote
This system allows for semi-automated liquid culture-based susceptibility testing.
87
How long does it typically take to detect susceptibility using solid media like Lowenstein-Jensen?
3–4 weeks
## Footnote
Solid media is less sensitive and takes longer than liquid culture.
88
What does Deeplex-MycTB by GenoScreen utilize for testing?
Targeted ultra-deep sequencing (24-plex amplification)
## Footnote
This method allows for simultaneous identification of Mycobacterium species and mutations.
89
Define MDR-TB.
Multidrug-resistant TB: Resistance to rifampicin and isoniazid
## Footnote
Approximately 250,000 cases globally each year.
90
What is Pre-XDR TB?
MDR-TB plus resistance to any fluoroquinolone
## Footnote
This classification indicates a more severe form of drug resistance.
91
What characterizes XDR-TB?
MDR-TB plus resistance to fluoroquinolones and at least one Group A drug
## Footnote
XDR-TB poses significant treatment challenges.
92
What are the clinical implications of drug-resistant tuberculosis?
Complex treatment regimens, higher mortality rates, prolonged therapy with toxic drugs
## Footnote
These factors complicate management of drug-resistant cases.
93
What is the BCG vaccine effective against?
Severe childhood forms of TB
## Footnote
BCG vaccination is the primary preventive measure against tuberculosis.
94
List the first-line anti-TB drugs.
* Isoniazid
* Rifampicin
## Footnote
These drugs are essential components of standard TB treatment regimens.
95
What are examples of second-line anti-TB drugs?
* Streptomycin
* Para-aminosalicylic acid (PAS)
## Footnote
Second-line drugs are used for drug-resistant tuberculosis.
96
What is the typical treatment duration for drug-susceptible TB?
6 months
## Footnote
Treatment for resistant TB is typically longer and more complex.
97
Where is the Irish Mycobacteria Reference Laboratory located?
St. James’s Hospital, Dublin
## Footnote
The IMRL provides essential services such as species identification and drug susceptibility testing.
98
What services does the Irish Mycobacteria Reference Laboratory provide?
* Species identification
* Drug susceptibility testing (DST)
* Epidemiological strain typing
## Footnote
These services are crucial for managing tuberculosis in Ireland.
