Mycobacterium tuberculosis (Tuberculosis)


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Mycobacterium tuberculosis (Tuberculosis)


Introduction to bacteria

Bacterial structure and functions

Gram positive bacteria

Staphylococcus epidermidis

Staphylococcus aureus

Staphylococcus saprophyticus

Streptococcus viridans

Streptococcus pneumoniae

Streptococcus pyogenes (Group A Strep)

Streptococcus agalactiae (Group B Strep)


Clostridium perfringens

Clostridium botulinum (Botulism)

Clostridium difficile (Pseudomembranous colitis)

Clostridium tetani (Tetanus)

Bacillus cereus (Food poisoning)

Listeria monocytogenes

Corynebacterium diphtheriae (Diphtheria)

Bacillus anthracis (Anthrax)


Actinomyces israelii

Gram negative bacteria

Escherichia coli

Salmonella (non-typhoidal)

Salmonella typhi (typhoid fever)

Pseudomonas aeruginosa


Klebsiella pneumoniae


Proteus mirabilis

Yersinia enterocolitica

Legionella pneumophila (Legionnaires disease and Pontiac fever)

Serratia marcescens

Bacteroides fragilis

Yersinia pestis (Plague)

Vibrio cholerae (Cholera)

Helicobacter pylori

Campylobacter jejuni

Neisseria meningitidis

Neisseria gonorrhoeae

Moraxella catarrhalis

Francisella tularensis (Tularemia)

Bordetella pertussis (Pertussis/Whooping cough)


Haemophilus influenzae

Haemophilus ducreyi (Chancroid)

Pasteurella multocida


Mycobacterium tuberculosis (Tuberculosis)

Mycobacterium leprae

Mycobacterium avium complex (NORD)

Other bacteria

Mycoplasma pneumoniae

Chlamydia pneumoniae

Chlamydia trachomatis

Borrelia burgdorferi (Lyme disease)

Borrelia species (Relapsing fever)


Treponema pallidum (Syphilis)

Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species

Coxiella burnetii (Q fever)

Ehrlichia and Anaplasma

Gardnerella vaginalis (Bacterial vaginosis)


Mycobacterium tuberculosis (Tuberculosis)


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USMLE® Step 1 questions

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High Yield Notes

4 pages


Mycobacterium tuberculosis (Tuberculosis)

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USMLE® Step 1 style questions USMLE

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A 55-year-old female presents to the emergency department with worsening cough and hemoptysis. The patient has had a cough for months, but over the past week, it has become more severe and produces bright-red blood. She is originally from Bolivia, where she worked as a nurse, and she immigrated to Ohio several months ago. Past medical history is unremarkable, and she does not smoke or use illicit drugs.  Temperature is 38.3°C (101°F), pulse is 110/min, respirations are 22/min, blood pressure is 90/64 mmHg, and O2 saturation is 92% on room air. Physical exam demonstrates an ill-appearing, cachectic woman. Cardiopulmonary exam is notable for diffuse rales throughout the lung fields, and mental status exam demonstrates a confused woman who is unable to recall the year or month. Abdominal exam is remarkable for hepatosplenomegaly. Laboratory and radiographic findings are demonstrated below.  
 Laboratory Value  Result 
 Hemoglobin  12 g/dL 
 Hematocrit  40% 
 Leukocyte count  2,500/mm3 
 Platelet count  90,000/mm3 
 Neutrophils, segmented  25% 
 Neutrophils, banded  1% 
 Eosinophils  0.5% 
 Basophils  0% 
 Lymphocytes  10% 
 Monocytes  2% 

 Erythrocytes  0/hpf 
 Leukocytes  100/hpf 
 Color   Yellow 
 Urine protein  1+ 
 Sediment   None 

Image reproduced from Radiopaedia    
Which of the following is the most likely diagnosis?  

External References

First Aid








Isoniazid p. 194

Mycobacterium tuberculosis p. , 193

Mycobacterium tuberculosis p. , 138

aerobic organism p. 124

culture requirements for p. 124

osteomyelitis p. 177

therapeutic agents p. 193, 194

Pyrazinamide p. 194

Mycobacterium tuberculosis p. , 193

Rifampin p. 193

Mycobacterium tuberculosis p. , 193


Content Reviewers

Rishi Desai, MD, MPH


Tanner Marshall, MS

It’s estimated that about two billion people worldwide are infected with mycobacterium tuberculosis, often just shortened to tuberculosis or simply ‘TB’. Two billion is a ton of people, but even though they’re infected, that doesn’t mean that all those people have symptoms, the vast majority, about 90-95%,  aren’t even aware that they’re infected. And this is because usually the immune system can contain it such that it isn’t able to multiply, and often remains latent, or dormant, as opposed to active, which usually causes symptoms and can be spread to others. If the host’s immune system becomes debilitated at some point down the road, like with AIDS or some other illness, or as a person grows older, it can be allowed to reactivate, or basically wake up and become very serious, especially if it spreads throughout the body.

Mycobacteria are an interesting bunch, they’re slender, rod-shaped, and need oxygen to survive, in other words, they’re “strict aerobes”. They’ve got an unusually waxy cell wall, which is mainly a result of the production of mycolic acid. Because of this waxy cell wall, they’re “acid-fast”, meaning that they can hold on to a dye in spite of being exposed to alcohol, leaving it bright red colored when a Ziehl–Neelsen stain is used.  The wall also makes them incredibly hardy, and allows them to resist weak disinfectants and survive on dry surfaces for months at a time.

Now Mycobacterium tuberculosis is usually transmitted via inhalation, which is how they gain entry into the lungs. Now, we breathe in all sorts of virus and bacteria all the time, but we’ve got defenses that take care of most of them. For one, air that we breathe in is turbulent in the upper airways, and drives most bacteria against mucus which is then cleared pretty quickly. Ultimately, though, TB can avoid the mucus traps and make its way to the deep airways and alveoli where we have macrophages that eat up foreign cells, digest, and destroy them. With TB, they recognize foreign proteins on their cell surface, and phagocytize them, or essentially package them into a space called a phagosome. With most cases, the macrophage then fuses the phagosome with a lysosome, which has hydrolytic enzymes that can pretty much break down any biochemical molecule. TB’s tricky, though, and once inside the macrophage, they produce a protein that inhibits this fusion, which allows the mycobacterium to survive. It doesn’t just survive, though, it proliferates, and creates a localized infection.


Mycobacterium tuberculosis is a species of pathogenic bacteria that is responsible for causing the infectious disease tuberculosis (TB). TB is a contagious disease that primarily affects the lungs but can also affect other parts of the body. It is spread through the air when an infected person coughs, sneezes, or talks. Symptoms of TB include a persistent cough, chest pain, and shortness of breath. If left untreated, TB can be fatal. Treatment for TB typically involves a combination of antibiotics for several months.


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