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Bacteriology F > Mycobacterium Tuberculosis > Flashcards

Mycobacterium Tuberculosis Flashcards

1
Q

What causes tuberculosis?

A

Mycobacterium tuberculosis is the major cause of tuberculosis, but this disease can be caused by a group of closely related species of Mycobacterium tuberculosis complex MTC

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2
Q

What’s the definition of tuberculosis?

A

Chronic disease characterized by delayed hypersensitivity and granuloma

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3
Q

Which bacteria are included in the MTC?

A

M. tuberculosis
M. Bovis
M. Canetti
M. Microtti

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4
Q

To what is linked the muramic acid of the PGL wall?

A

Arabinogalactan layer composed of arabinose and galactose

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5
Q

What do we find above this layer?

A

Large amount of mycolic acid overlain by free lipids and glycolipids

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6
Q

Where polypeptides are located? What derives from them?

A

Polypeptides are above the lipid layer

PPD, purified protein derivative, derives from them

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7
Q

What is the function of the PPD?

A

They activate the cell mediated immunity

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8
Q

What makes them virulent?

A

They are capable of intracellular growth in unactivated alveolar macrophages

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9
Q

What causes the disease primarily?

A

Disease is primarily caused by the host response to infection
The disease is immunopathological, resulting from the production of granulomas, not caused by exotoxin or LPS..

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10
Q

Who are the reservoir?

A

Humans

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11
Q

How it is transmitted?

A

Person to person spread by aerosols from diseased individuals via coughing, sneezing or vocalizing

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12
Q

What are the basic conditions for transmission?

A 
Extent of the disease
Extent of the exposure
Absence of UV light and improper ventilation
Malnutrition
Age
Frequency of the coughs
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13
Q

When individuals are highly infectious?

A

When they expectorate the bacteria

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14
Q

What’s the period of exposure in order to be infected?

A

To be infected, there has to be a long period of exposure to infected individuals

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15
Q

What destroys the bacteria first?

A

UV light

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16
Q

In which age groups that is a quicker progression of the disease?

A

In individuals less than 1 year old and in elderly people

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17
Q

How the cough progresses?

A

It is mild repetitive at the beginning, not as severe as that caused by a viral or different bacterial ideology. In late stages, there is hemoptysis

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18
Q

What’s the problem of MTC?

A

The resistance to regular disinfectants and detergents

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19
Q

How the primary infection is acquired?

A

By droplet nuclei because of the small size of the bacteria

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20
Q

Where do they go? Why?

A

They go to alveoli since there is O2, they also need 5 to 10% of CO2

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21
Q

By which cell they are phagocytosed?

A

By macrophages

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22
Q

Where do they go then? How they are transported?

A

They go via these macrophages into regional lymph nodes, hilar lymph nodes

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23
Q

What is the outcome of the primary infection?

A

Individuals remain chronic carriers of the bacteria, in a dormant state in the granulomas

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24
Q

How the disease is confined?

A

The disease is confined by these granulomas covered with calcified tissue, that can be detected with a chest x-ray

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25
Q

Are individuals infectious at this stage?

Do they have symptoms? How do we know that they are infected?

A

They are not infectious, they can live long lives as long as the activated macrophages are controlling, so the macrophage-mediated immunity is stronger
They have no symptoms and the only way to tell they’re infected is the PPD test

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26
Q

When do we talk of a postprimary tuberculosis?

A

When DTH, delayed type hypersensitivity, prevails

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27
Q

To what is related the disease?

A

It is related to a chronic granulomatous state that is a DTH disease

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28
Q

What happens in the stage instead of the confinement?

A

Tissue distruction instead of confinement of the infection

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29
Q

Which other cells participate in the distraction?

A

Tc lymphocytes and NK cells

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30
Q

How the distruction happens?

A

There is liquefaction of the casestion part and bursting of the granuloma

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31
Q

What does the bacteria after tissue destruction?

A

Bacteria multiply rapidly in the caseation part

They will go out, leaving a cavity —> cavitation stage

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32
Q

What happens during the cavitation stage?

A

It is a source of more extensive coughs with expectoration of more sputum and bacilli

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33
Q

What are the symptoms of this stage?

A

High fever

Anorexia and weight loss (—>wasting disease)

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34
Q

Which individuals are the most infectious?

A

Those with open cavities

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35
Q

Where bacteria can go during coughing?

A

Bronchi, trachea and then the larynx

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36
Q

What is the most infectious stage of tuberculosis?

A

Laryngeal tuberculosis and it is one of the end stages

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37
Q

What shows a chest x-ray for a postprimary infection?

A
  • Cavitation of the lungs

- An architectural change of the lungs represented by shrinkage and decrease in volume of the lungs because of fibrosis

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38
Q

What is the survival range if individuals are left untreated?

A

2.5 to 3 years

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39
Q

What happens if they are treated?

A

They can have long lives, with on and off state, intervals in which they are good, and intervals in which there is reactivation

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40
Q

Why they can’t be cured of the bacilli?

A

Since they are chronically infected, they can only be cured of the manifestations and the allergic hypersensitivity reaction

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41
Q

What happens if during the primary infection the individual isn’t able to confine the primary complex?

A
  • Bacteria can go to the surface of the lungs without entering them
  • In the case of HIV infection before tuberculosis, there is a quick progression of tuberculosis since macrophages are not properly functional and lymphocytes are destroyed
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43
Q

What do we call liquid droplets where bacteria are found?

A

Droplet nuclei

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44
Q

Why these nonspore forming bacteria are considered as resistant bacteria?

A

Since they can stay for 9 months to 1 year in an environment without sunlight and ventilation

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45
Q

What is the infectious dose?

A

5 to 200 bacteria are enough to cause an infection so it is a very small infectious dose

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46
Q

Where bacteria live and replicate? How?

A

In unactivated macrophages by inhibiting the phagosome-lysosome fusion

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47
Q

In which part of the lungs bacteria are found?

A

In alveoli

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48
Q

Where bacteria will spread?

A

In the hilar lymph nodes

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49
Q

From what is composed the primary complex?

A

From the Ghon focus and the hilar lymph nodes

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50
Q

What are the symptoms? Are they severe?

A

They are mild symptoms

Low fever, respiratory manifestations, mild cough that can be accompanied with streaking of blood

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51
Q

How the disease is confined in the primary complex?

A

By the production of the granuloma

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52
Q

Which T lymphocytes will be recruited? When? What is the function?

A

After 10 days of the infection, activated T cells especially Th type: Th1 that produce lymphokines to recruit macrophages and even Th2
They will produce lymphokines and interleukins to activate macrophages

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53
Q

What is the structure of the granuloma?

A
  • Its central part is formed by unactivated macrophages (multinucleated giant cells that are dead), and necrotic tissue containing bacteria (pus) that has a cheese like consistency, so it is called caseation
  • Its outer part is formed of activated macrophages (epithelioid cells) and T cells
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54
Q

Why there will be acidification of the medium?

A

Because many bacteria are destroyed

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55
Q

What will cover granulomas?

A

Fibrous tissue and calcification

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56
Q

Why at this stage bacteria are not affected by antibiotics?

A

Since they are dormant in the center of the granulomas, so there is confinement and recovery of the symptoms not of the bacteria because of chronic infection

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57
Q

By which way we can know that there is an infection?

A

With the PPD test and chest x-ray where granulomas look like scares in different areas of the lungs

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58
Q

What is the final outcome of the primary infection?

A

After calcification, bacteria are dormant and the disease is under control

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59
Q

What do we call the lesions forming after the initial infection? What happens to those lesions?

A

Ghon focus

Mostly, they heal spontaneously and become small calcified nodules

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60
Q

From what is composed of the Ghon complex?

A

Ghon focus + Regional lymphadenopathy

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61
Q

In which age groups primary pulmonary TB may progress rapidly to clinical illness?

A

In young children with immature cellular mediated immunity (CMI) and in persons with impaired immunity e.g. those with malnutrition or HIV infection

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62
Q

What happens if bacilli penetrate into the pleural space?

A

We have pleural effusion

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63
Q

What happens in the primary infection in infants less than 1 year of age?

A

There is the progression of the disease, there is a tendency to develop a meningitis and a miliary tuberculosis

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64
Q

What do we have during miliary tuberculosis?

A

There are many white nodules which are the miliary foci of tuberculosis

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65
Q

Why the PPD test in individuals under 1 year with miliary tuberculosis is negative?

A

Because before invasion of the lungs, PPD test is negative and in those children there is no invasion yet

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66
Q

What causes postprimary tuberculosis after the primary infection?

A

Depression in cellular immunity

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67
Q

What balance should be present to confine the primary infection?

A

Between the activity of activated macrophages and TH1 which confine the focus and TH2 which have a destructive effect

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68
Q

How the caseation part gets liquefied?

A

Because there is destruction of bacteria, and, at the same time, tissues surrounding the bacteria

69
Q

What happens after this liquefaction?

A

We are left with an open cavity which is the source of hemoptysis because of open capillaries, blood comes out with every expectoration

70
Q

What is expectorated?

A

Sputum and bacilli

71
Q

Where bacteria can go when coughing?

A

To bronchi, trachea and larynx

72
Q

What is the most infectious stage and one of the end stages of tuberculosis?

A

Laryngeal tuberculosis

73
Q

Why cavities are a good area of bacterial multiplication?

A

Since it is an oxygenated area

74
Q

What causes liquefaction?

A

Interleukins produced by T cells and proteases of macrophages

75
Q

What are the symptoms of the postprimary tuberculosis in the middle range?

A

Fever, night sweats, weight loss, anorexia, general malaise and weakness (wasting disease)

76
Q

When there is pleuritic chest pain?

A

In patients with sub-pleural disease

77
Q

What should we rule out in the case of hemoptysis?

A

Cancer

78
Q

What happens in the case of miliary tuberculosis?

A

Fever is a perplexing fever, it goes up and down like saddle fever

79
Q

To what leads laryngeal infection? How it is caused?

A

At least you hoarseness of the voice

It is caused by the fact that with each cough there are bacilli that are going to the larynx

80
Q

What is the basic rule with tuberculosis?

A

No matter where bacilli go first, there will be involvement of the regional lymph nodes via unactivated macrophages

81
Q

Which lymph nodes are involved in the case of pulmonary tuberculosis? Tonsils? GI tract? Skin?

A

Hilar lymph nodes
Cervical lymph nodes
Mesenteric lymph nodes
Regional lymph nodes

82
Q

From what is composed the primary complex?

A

Primary infection + Regional lymph nodes

83
Q

By what is usually controlled the primary complex?

A

The formation of a granuloma that gets calcified

84
Q

Which organs can be affected by extra pulmonary tuberculosis?

A

Lymph nodes, pleura, genitourinary tract, bones and joints, meninges, peritoneum, pericardium, miliary

85
Q

What is the most common form of tuberculosis infection outside the lungs?

A

Tuberculous lymphadenitis or tuberculous adenitis (scrofula)

86
Q

What happens if bacteria go to the surface of the lungs without entering them primarily?

A

The result is meningitis, miliary tuberculosis, pleurisy.. after a period of time, there will be a pulmonary invasion and bacteria will go to the lungs

87
Q

What is the presentation when lymph nodes are involved?

A

Painless swelling, inflammation, of the lymph nodes

88
Q

How starts the scrofula, and how it progresses? What could be produced?

A

It starts as painless hard swelling that becomes harder, nontender with time
Many times there is production of sinuses and development of fistula in which we have draining of liquid

89
Q

What is the major cause of scrofula and G.I. tract tuberculosis?

A

Ingestion of Koch’s bacilli

90
Q

What happens when bacilli pass through the tonsils to go to the intestine?

A

The primary tuberculosis will involve the tonsils and the regional lymph nodes

91
Q

How much do we need bacteria to cause infection in tonsils? In the stomach?

A

A small number of bacteria is needed in the tonsils

But a high number is needed in the stomach because it is highly resistant to these bacteria

92
Q

What are the rates of founding the bacteria in a biopsy?

A

50% AFB positive

80% positive culture

93
Q

When could we have an infection of the pleura?

A

During a primary infection

During a postprimary infection

94
Q

What happens during a primary infection?

A

Bacteria go in the pleural space space before invading the lungs

95
Q

What is the composition of the effusion in this case?

A

It has a high protein content, a low glucose content and a high amount of lymphocytes

96
Q

What are the manifestations of pleurisy?

What could be done to relieve the patient?

A

Chest pain

Aspirate a small amount of the effusion

97
Q

What is the result of the PPD test? Why?

Do we find AFB?

A

Negative since there is still no involvement of the lungs

AFB are rarely seen

98
Q

When there can be invasion of bacteria in the lungs?

A

After several years of receiving the proper treatment causing a pulmonary tuberculosis

99
Q

What happens during a post primary infection?

A

In this case the infected liquid spilling from the cavities go to the pleural space

100
Q

Is it an effusion in this case?

A

No it is an empyema which is an abscess in the pleural space

101
Q

Which one is more severe a primary or a postprimary infection?

A

Postprimary infection, with high fever

102
Q

What is the results of the PPD test? Are AFB seen?

A

PPD test will be positive

AFB are found in large amounts and more cultures are positive

103
Q

What are the symptoms when the effusion is large?

A

Fever, pleuritic chest pain and dyspnea

104
Q

What is the appearance of the fluid?

A

It is straw colored or hemorrhagic depending on wether there is a primary or postprimary infection

105
Q

What can cause the bacteria during an infection of the pleural fluid? How?

A

Pneumonia or bronchitis

Either via lymphatic channels or direct spreads via lungs or through blood to any organ

106
Q

How the genitourinary tuberculosis is caused?

A

From hematogenous or lymphogenous spread (from infected mesenteric lymph nodes) from G.I. tract tuberculosis

107
Q

What can be involved in the case of urinary tract infections?

A

The bladder and ureters

108
Q

What are the symptoms of urinary tract infections?

A

Hematuria, pyuria and abdominal pain

109
Q

What is the rate of finding the bacteria in the urine?

A

90% positive culture

110
Q

Which parts are involved in females when we have genital tract infection?

A

There can be salpingitis where 20% of them progress to infertility by fibrosis
It can also affect the endometrium

111
Q

What are the symptoms?

A

It can lead to pelvic pain and menstrual abnormalities

112
Q

Which parts in males are involved in the genital tract infection?

A

There can be inflammation of the epididymis, or inflammation of the testes (orchitis) or prostatitis

113
Q

Which part of the skeleton are involved?

What’s the outcome of the infection in these sites?

A

Bones (vertebrae in the lower back especially), and joints (hips and knees i.e. weight bearing joints)
There are chronic abscesses in these sites

114
Q

What is Pott’s disease?

A

Spinal tuberculosis involving vertebral bodies

There can be too much spread in lymphatics (paravertebral lymph nodes), causing an unstable spine appearance

115
Q

How bone and joint disease is caused?

A

Pathogenesis is related to reactivation of hematogenous foci or to spread from adjacent paravertebral lymph nodes

116
Q

What do we find in bone biopsy?

A

We have AFB positive and culture positive

117
Q

From what results tuberculous meningitis?

A

From the hematogenous spread

118
Q

What are the two cases of tuberculous meningitis?

A

During a primary infection before any lung involvement

After pulmonary tuberculosis after a bacteremia

119
Q

What is the presentation during a primary infection?

A

Headache and slight mental changes after weeks of low-grade fever, malaise, anorexia

120
Q

What are the signs if it is not diagnosed directly?

A

Severe headache, confusion and neck rigidity

121
Q

Why meningitis is very dangerous in children?

A

Because it always precedes lung involvement

122
Q

Which granulomas are used to confine the disease?

A

Tuberculomas and they will stay in the CSF and in neural tissues

123
Q

What happens in the case of reactivation of granulomas in some children?

A

Seizures will occur but not meningitis

This case is much more difficult to be treated

124
Q

How meningitis after pulmonary tuberculosis is diagnosed?
What is the composition of the CSF?
What is the rate of finding a bacteria?

A

By lumbar puncture
Examination of the CSF reveals a high leukocyte count, high protein content and low glucose concentration
AFB positive in 1/3 of the cases, culture positive and 80% of the cases

125
Q

What is the cause of GI tract tuberculosis?

A

It results from ingestion of milk from cows affected by bovine tuberculosis
Any portion of the G.I. tract may be affected
It can follow a pulmonary tuberculosis either by hematogenous or by lymphogenous spread

126
Q

What is the presentation of the G.I. tract tuberculosis?

A

Non-specific abdominal pain, fever and ascites (accumulation of fluid in the peritoneal cavity causing abdominal swelling)

127
Q

How it’s diagnosed?

A

Paracentesis reveals an exudate fluid with high protein content and leukocytosis
Direct smear shows AFB negative and culture negative
For real diagnosis, we need to do a peritoneal biopsy that shows granulomas and the AFB

128
Q

How pericardium tuberculosis is caused?

A

Due to hematogenous spread or lymphogenous spread (from lungs lymph nodes after pulmonary tuberculosis)

129
Q

What are the presentations of pericardial tuberculosis?

A

Dyspnea, fever and retrosternal pain

130
Q

How it is diagnosed?

A

By pericardiocentesis
The effusion is exudative in nature, with proteins and a high count of leukocytes
Direct smear shows AFB negative
Culture of pericardial fluid reveals the bacilli in up to 2/3 of the cases, while pericardial biopsy has a higher yield.

131
Q

When miliary tuberculosis can happen?

A

During the primary infection

During the postprimary infection

132
Q

How it occurs during the primary infection?

A

In children where we have spread of the bacteria in different organs
It can be followed by a lung infection in which we have involvement of all lungs part not just the lower parts

133
Q

What is in this case the result of the PPD test?

A

PPD negative because before invasion of the lungs unless we wait for a longer period of time

134
Q

What is the cause of the postprimary infection?

A

Hematogenous spread
And children it is often the consequence of primary infection
In adult it may be due to either recent infection or reactivation of old disseminated foci

135
Q

What is the appearance of lesions during miliary tuberculosis?

A

Yellowish granulomas that resemble millet seeds

136
Q

What is the presentation?

A

Non-specific depending on the predominant side of involvement
Fever, night sweats and weight loss

137
Q

What reveals a chest radiography?

A

Miliary reticulonodular pattern although not a present early in the course and among HIV infected patients

138
Q

What is the diagnosis?

A

AFB positive in 20% of the cases, PPD negative in 50% of the cases
Bronchioloalveolar lavage is more likely to provide bacteriology confirmation
If not recognized it is lethal

139
Q

What is the cause of the ocular tuberculosis?

A

It is not caused by bacteria since the culture is negative, but by a hypersensitivity reaction

140
Q

Where do we have granulomas?

A

In the ocular space

141
Q

What are other names of the PPD test?

A

Skin test reactivity
Mantoux test
Tuberculin test

142
Q

What is the PPD test?

A

It is a very specific reaction to the proteins of Mycobacterium tuberculosis. There can be some cross-reactivity with atypical mycobacteria.

143
Q

What is the type of the reaction?

What is the result of this reaction?

A

It is a delayed type hypersensitivity reaction due to sensitized T cells that act on effector monocytes.
It results in an erythema and induration in case of positive reaction (hardening of the area where there is injection of the PPD). It is felt by palpation.

144
Q

How this test is done?

A

By injection of PPD, then drawing a circle of 10 to 15 mm of diameter

145
Q

What are the conditions for a positive test?

A
  • There has to be an infection with lung involvement (e.g. in the case of miliary tuberculosis or meningitis, the individual can be PPD negative because the T cells have not been properly sensitized, so there is no induration when they reencounter the Ag)
  • It should be done in the forearm
  • Intradermal (false results if subcutaneous)
  • Amount: A standardized amount of PPD antigen will give the results. it is called the intermediate those of PPD (5 IU).
  • Time: palpation is performed after 48 to 72 hours
146
Q

What should we put in the syringe before injecting the PPD?

A

When we put the amount in syringe, we need to put additional chemicals to prevent sticking of the proteins to the walls, which would decrease their amount

147
Q

What is the result of repeated PPD test if the person is not infected?

A

Repeated PPD tests will not convert the person into a PPD positive

148
Q

What is anergy?

When does it occur?

A

Negative immune reaction in an infected person

It occurs in elderly who were infected, and who didn’t do PPD for a long time, PPD is negative

149
Q

What do we do in this case?

A

In this case we do a repeated PPD test to boost the original reaction
The first PPD dose is to activate the T cells, The second one done after 7 to 10 days will be positive

150
Q

What do we consider an induration of any diameter in the case of HIV infected individuals?

A

It is considered positive because the diameter depends on the amount of T lymphocytes

151
Q

When do we consider an induration of 5 or more mm positive?

A
  • In a recent contact of a person with tuberculosis
  • In persons with fibrotic changes on chest radiography consistent with prior tuberculosis
  • In patients with organ transplants
  • In persons who are immunosuppressed for other reasons (e.g. taking the equivalent of >15 mg/day of prednisone for one month or longer, taking TNF alpha antagonists)
152
Q

When do we consider an induration of 10 mm or more positive?

A
  • In recent immigrants from high prevalence countries e.g. Africa
  • In injection and drug users
  • In residents and employees of high risk congregate settings
  • In mycobacteriology laboratory personnel
  • In persons with clinical conditions that place them at a high risk
  • In children under 4 years of age
  • In infants, children, and adolescents exposed to adults in high-risk categories
153
Q

When do we consider an induration of 15 or more mm positive??

A

In any person, including persons with no known risk factors for tuberculosis.

154
Q

Why it is important to do the culture?

A

For antibiogram, to know to which drugs the bacteria are sensitive

155
Q

Why sputum is not always the proper specimen in the diagnosis of pulmonary tuberculosis?

A

Because it might not contain bacteria

156
Q

What do we do in this case?

A

We can do a bronchioloalveolar lavage or 3 consecutive gastric lavage

157
Q

Why do we give a synergy of drugs?

A

Since resistance develops quickly even if bacteria are sensitive to those antibiotics

158
Q

What is the treatment in case there is no multidrug resistance?

A

-First 2 months: Pyrazinamide, INH, rifampicin, a 4th drug (streptomycin, ethambutol, quinolones, some microlides, cycloserine, ethionamide, PAS)
After 2 months, we stop pyrazinamide and the 4th drug and we continue with INH and refampicin for 9 to 12 months

159
Q

What is the treatment in case of multidrug resistance?

A

We add PAS, or quinolones.

160
Q

When do we give prophylaxis?

Which prophylaxis is given?

A

If a person has been in contact with a diseased individual

INH for 12 months

161
Q

Where are kept individuals suffering from pulmonary tuberculosis?

A

In the sanatorium

162
Q

What happens after 2 to 3 weeks?

A

Symptoms ameliorate, fever and anorexia decrease, individuals start to gain weight, coughs decrease

163
Q

What happens after 2 months?

A

When the sputum specimen becomes AFB negative we can send individuals back home

164
Q

For what we do x-rays? When?

A

After 4 months x-ray ameliorates. We do x-rays both for chest and bones in case of skeletal tuberculosis. In other cases x-ray is of no use.

165
Q

What is the vaccine?

A

It is the BCG vaccine which is a live attenuated mycobacterium bovis, so it multiplies in the system, giving continuous Ag stimulation to the person.

166
Q

What is the result of the PPD test in vaccinated individuals?

A

It will be positive for 5 to 7 years

167
Q

What if after 7 years the individual is still PPD positive?

A

If after 7 years the individual is still PPD positive, it means that during this interval, he was infected with a virulent type

168
Q

What are the most common sites of infection of lymph nodes?

A

The posterior cervical and supraclavicular site

Bacteriology F (16 decks)

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