TB and MAC- Exam 2 Flashcards
What organism causes most TB disease in the U.S.?
Mycobacterium Tuberculosis
How is TB spread?
Respiratory droplets
The probability that TB will be transmitted depends on what four factors?
Infectiousness of the TB patient, Environment, Frequency and duration of the exposure, and Immune status of the individual
What is Latent TB Infection (LTBI)?
It is TB that has remained dormant and then appears at times of immunocompromise. Non-infectious and asymptomatic.
When a person inhales air that contains droplet nuclei containing M. tuberculosis, where do the droplet nuclei go and where does infection begin?
After inhalation, the bacteria travels to the alveoli where it multiplies in the lungs then can spread through the bloodstream.
In people with LTBI how does the immune system keep the tubercle bacilli under control? What happens if the immune system fails and the bacilli begin to multiply rapidly?
Macrophages surround the tubercle bacilli and LTBI occurs but if the immune system fails then replication can no longer be kept under control and active TB infection will take place.
List at least 4 differences between LTBI and TB.
Latent TB is controlled by the immune system, non-infectious, asymptomatic, chest x-ray normal.
TB is active and is not controlled by the immune system, infectious, symptomatic, chest x-ray abnormal.
What percentage of those with LTBI will develop TB (non-HIV infected)?
10%
Name at least two conditions that appear to increase the risk that LTBI will progress to TB disease?
Those taking immunosuppressive therapy and those who have HIV.
TB primarily affects the lungs. Name two other sites that “extrapulmonary” TB can occur?
It can occur in the spine and brain.
. Name 7 groups of people who are more likely to be exposed or infected with TB
Medically underserved, People in Correctional facilities, People in Nursing homes, People in Homeless Shelters, Health care workers, People who visit areas with high prevalence of TB disease, People who abuse drugs or alcohol
Name at least 2 ethnic groups that are disproportionately affected by TB?
Asian and Hispanic/Latino Descent
Give 2 possible reasons why these ethnic groups may have a higher rate of TB
Lower Socioeconomic status and higher incidence of HIV infection (TB is prevalent with AIDS)
When a child has TB infection or disease, what does it tell us about the spread of TB in the child’s home or community? Name 3 things:
TB was transmitted relatively recently
Person who transmitted the TB to the child may still be infectious
Others may have also been exposed
Name 5 groups of people who are more likely to develop active TB disease once infected:
Children younger than 5 years of age, People receiving immunosuppressive therapy, People who have a low body weight, People who smoke cigarettes or abuse drugs/alcohol, People who have been infected with M. tuberculosis within the past 2 years
If a person is infected with both M. tuberculosis and HIV, what are his or her chances of developing TB disease? How does this compare to the risk for people who are infected only with M. tuberculosis?
7% to 10% each year. The risk for developing TB is much higher when the patient also has HIV with infection than just the infection of M. tuberculosis alone. Those who are infected with Mycobacterium Tuberculosis have a 5% chance of developing TB.
What diagnostic test is used to screen for and diagnose latent TB (LTBI)?
Mantoux tuberculin skin test or a blood test (interferon-gamma release assay) and if either is positive then need a chest x-ray
With the TST, after the injection is administered, when is the patient’s arm examined?
48 to 72 hours
What 2 factors determine the interpretation of a skin test reaction as positive or negative?
Induration size and patient risk factors.
For which groups of people is > 5 mm of induration considered a positive reaction? Name 4.
Patients with HIV infection or risk for HIV, recent close contact to someone with TB, patients with CXR consistent with prior TB, patients with organ transplants or other immunocompromised patients
For which groups of people is > 10 mm of induration considered a positive reaction? Name 7.
-Countries with high rate of TB
- low body weigt
- less than 5 years old
- high risk setting
- teenagers exposed to active TB
- IV drug user
- Mycobateriology lab worker
For which group of people is > 15 mm of induration considered a positive reaction?
Everyone else
Name 3 factors that can cause a false positive reaction to the TST?
-Previous BCG vaccine for TB
-Infection with non TB mycobacteria
-Incorrect measurement
-Incorrect antigen
Name 6 factors that can cause a false negative reaction to the TST
Recent TB infection within 8-10 weeks
Anergy so absence of normal immune response or weakened immune system
Age <6 months old
Recent live virus vaccine such as MMR
Incorrect administration
Incorrect interpretation
After TB has been transmitted to someone, how long does it take before TB infection can be detected by the TST?
Approximately 8 to 10 weeks
True or False: If a patient has a negative TST result, but has symptoms of TB disease, they should be medically evaluated for active TB disease
True
