00:00 / 00:00
Bacterial structure and functions
Bacillus anthracis (Anthrax)
Bacillus cereus (Food poisoning)
Corynebacterium diphtheriae (Diphtheria)
Clostridium botulinum (Botulism)
Clostridium difficile (Pseudomembranous colitis)
Clostridium tetani (Tetanus)
Streptococcus agalactiae (Group B Strep)
Streptococcus pyogenes (Group A Strep)
Bartonella henselae (Cat-scratch disease and Bacillary angiomatosis)
Legionella pneumophila (Legionnaires disease and Pontiac fever)
Salmonella typhi (typhoid fever)
Yersinia pestis (Plague)
Vibrio cholerae (Cholera)
Bordetella pertussis (Whooping cough)
Francisella tularensis (Tularemia)
Haemophilus ducreyi (Chancroid)
Mycobacterium tuberculosis (Tuberculosis)
Mycobacterium avium complex (NORD)
Gardnerella vaginalis (Bacterial vaginosis)
Coxiella burnetii (Q fever)
Ehrlichia and Anaplasma
Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species
Borrelia burgdorferi (Lyme disease)
Borrelia species (Relapsing fever)
Treponema pallidum (Syphilis)
0 / 1 complete
Mycobacterium avium complex, or MAC, includes three species; Mycobacterium avium, Mycobacterium Chimaera, and Mycobacterium intracellulare.
MAC is the most common nontuberculous mycobacteria, or NTM.
The three different species of MAC are difficult to differentiate and cause the same spectrum of diseases, so they are often grouped together.
MAC is very different from Mycobacterium tuberculosis.
MAC lung infection is a chronic disease, often present for several years prior to diagnosis.
It typically has a more indolent course, and can be difficult to eradicate, with frequent recurrences after completing long courses of treatment.
In addition, in immunocompromised individuals, MAC can become disseminated, affecting organs other than the lungs, and can cause lymphadenitis.
MAC are non-motile, facultative intracellular bacteria which means they can survive both inside and outside the cell.
They’re also aerobic which means they need oxygen to survive.
They have a high content of mycolic acid in their cell wall, which makes them waxy, hydrophobic and impermeable to routine stain such as Gram stain.
So, they need special staining methods to be visualized such as Ziehl-Neelsen staining which is able to penetrate the waxy mycobacterial cell wall.
So, the stain binds to the mycolic acid in the mycobacterial cell wall and after staining, an acidic decolorizing solution is applied which removes the red dye from the background cells, tissue fibres, and any organisms in the smear except Mycobacteria, which retain the dye; and this is why they are called “acid-fast,” and they appear bright red on a blue background.
Finally, MAC are slow growing bacteria, and it typically takes them 10 to 21 days to grow on a medium called Lowenstein Jensen.
MAC are ubiquitous in soil and water and they are thought to enter the body through inhalation.
Once inside the body, they adhere to mucosal epithelial cells in the respiratory tract, and infect the macrophages that try to destroy them.
Macrophages try to break down the MAC organisms inside an intracellular organelle called a lysosome, which contain digestive enzymes.
However, MAC has unique, antigenic lipids called glycopeptidolipids, or GLPs, which are found on the surface of the cell.
These GLPs act as a protective barrier against lysosomal enzymes, allowing the bacteria to survive and multiply inside macrophages.
Mycobacterium avium complex or just MAC, is a group of bacteria that includes Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium Chimaera. These are acid-fast bacilli, non-motile, facultative intracellular, aerobic bacteria found in soil and water, and are known to cause respiratory infections. MAC infections often attack people with weakened immune systems, such as those with AIDS, and lymphadenitis in children. Symptoms of MAC include fever, night sweats, weight loss, and a persistent cough.
Latest on COVID-19
Nurse Practitioner (NP)
Physician Assistant (PA)
Create custom content
Raise the Line Podcast
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
Terms and Conditions
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.