Mycobacterium Tuberculosis & Streptococcus Agalactiae Flashcards
Which bacterium causes tuberculosis, and how is it transmitted?
Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis, and is transmitted through air when people with TB cough, sneeze, or spit.
Which organ is primary affected by tuberculosis?
Pulmonary TB (lunge) is most common, but any organ may be affected.
TB meningitis and miliary TB is the most severe.
What are the general symptoms of TB?
Fever, weight loss, reduced appetite, weakness/fatigue, night sweats.
Lung symptoms: cough for several weeks, sputum which may be blood stained, chest pain, breathing problems.
How is TB treated?
Treatment with several active drugs at the same time to ensure cure and avoid relapse of the disease, normally for 4-6 months.
The most common antibiotics used are: isoniazid, rifampicin, pyrazinamide, and ethambutol.
Directly observed treatment, short course (DOTS):
- First two months with four drugs
- Then four months with two drugs
What is primary and secondary resistance?
Primary resistance: no previous treatment
Secondary resistance: developed during treatment
What is Line-Probe Assays (LPA)?
DNA is extracted from culture or directly from clinical speciments.
Next, PCR amplification is performed using biotinylated primers. Labeled PCR products are hybridized with specific oligonucleotide probes immobilized on a strip.
Captures labeled hybrids are detected by colored bands on the strip at the site of probe binding.
What is latent tuberculosis?
Latent TB is when a patient is infected with the Mycobacterium tuberculosis, but the infection is not active. That means that the infection can not be transmitted to another person.
The bacteria lives in the body, but does not grow. The patient has not any symptoms.
Can advance to TB disease.
Which methods can be used to detect TB?
WHO recommends the use of rapid molecular diagnostic test like Xpert MTB/RIF Ultra and Truenat assays as the initial diagnostic test.
Otherwise, microscopy, culture, PCR, or molecular susceptibility analysis can be used.
Why is the TB rpoB important?
A 81 bp sequence includes mutations covering about 95% of rifampicin-resistant mutations.
How is TB normally treated?
By antibiotics.
In certain countries, the BCG vaccine is given to babies or small children to prevent TB.
What conditions can increase a persons risk for TB disease?
- Diabetes (high blood sugar)
- Weakened immune system (ex from HIV or AIDS)
- Being malnourished
- Tobacco use
- Harmful use of alcohol
What characterize multidrug-resistant TB (MDR-TB)?
The bacteria do not respond to isoniazid and rifampicin, the two most effective first-line TB drugs. MDR-TB is treatable and curable by using other drugs, which tend to be more expensive and toxic.
Why is people with HIV about 16 times more likely to fall ill with TB disease?
HIV and TB form a lethal combination, each speeding the others progress.
What characterizes primary TB, and what method is used to distinguish between primary and secondary TB?
Chest X-rays (CXR) is a screening tool and used as a diagnostic aid to differentiate between primary and secondary TB.
Primary disease is usually characterized by a single lesion in the middle or lower right lobe with enlargement of the draining lymph nodes.
What are factors to consider when identifying M. tuberculosis on medium?
M. tuberculosis is an obligate aerobe, grows optimally at 37°C and at a pH of 6.4-7.0. It is a slow-growing organism with a generation time of 14-15 h and the colonies appear only in about two weeks and sometimes may be delayed up to 6-8 weeks. On solid media, M. tuberculosis forms dry, rough, raised, irregular colonies with a wrinkled surface. The colonies are creamy white initially, becoming yellowish or buff colored later and tough when picked off. They are tenacious and not easily emulsified.
