MICROBIO 3.9 - ACID-FAST BACTERIA

Acid Fast Bacteria

• Gram-positive bacilli are contrasted with Gram-negative bacilli and bacilli-like organisms.
• Gram-negative bacilli are contrasted with Gram-positive cocci.
• Diagnostic and laboratory tests can differentiate bacteria cultures, like the coagulase test.
• Virulence factors help pathogens subvert the immune system and sicken the host.
• Diagnosis and treatment is determined by patient history, signs/symptoms, diagnostic tests, lab values, and virulence factors.
• Treatment contraindications include antibiotic allergies.
• It is crucial to recognize bacterial strains within each group.
• Mycobacteria are acid-fast.

Atypical Bacteria

• Atypical bacteria may or may not have cell walls.
• Bacteria without a cell wall are Mycoplasma and Ureaplasma.
• Acid-fast bacteria are Mycobacteria.
• Bacteria that are obligate intracellular are Chlamydia, Rickettsia, and Coxiella.
• Spirochetes are Borrelia, Leptospira, and Treponema.

Why Should You Care?

• Tuberculosis incidence saw a nine-percent reduction between 2015 and 2019
• TB deaths saw a 14% drop in the same period.
• Access to TB services remains a challenge.
• Global targets for prevention and treatment will likely be missed without urgent action and investments.
• In 2011 in the US there were 1,042 cases of drug-resistant tuberculosis
• In 2011 in the US there were 10,528 Tuberculosis cases in total.
• Tuberculosis is among the most common infectious diseases
• Tuberculosis is among the most frequent causes of death worldwide

Mycoplasma vs. Mycobacterium

• Mycoplasma are small, free-living organisms and facultative anaerobes, except for strictly aerobic Mycoplasma pneumoniae.
• Mycoplasma lack a cell wall, making them resistant to certain antibiotics.
• Mycoplasma cell membranes contain sterols.
• Mycoplasmas do not gram stain
• Mycoplasma pneumoniae and Ureaplasma are included.
• Ureaplasmas are mycoplasmas that produce urease.
• Mycobacterium has a thick, protective, waxy cell wall that is lipid-rich and does not gram stain.
• Mycobacterium is acid-fast and resistant to detergents and antibiotics, making it difficult to diagnose and treat.
• Mycobacterium includes Mycobacterium tuberculosis, Mycobacterium leprae, and non-tuberculosis mycobacterium.

Mycoplasma Pneumoniae

• Mycoplasma pneumoniae spreads slowly, with long incubation periods, and asymptomatic carriers, making it difficult to diagnose.
• It causes respiratory and extrapulmonary infections, spreading via respiratory droplets and infecting the respiratory tract.
• Mycoplasma attaches to ciliated epithelial cells using pili and adhesin, destroying them with reactive oxygen species and exotoxins.
• Treatment is with doxycycline, but some strains carry antibiotic resistance.
• Extrapulmonary infections can present as neurological, cardiac, or skeletal infections.
• Other mycoplasmas and ureaplasmas can cause sexually transmitted infections like Mycoplasma genitalium and Ureaplasma urealyticum.
• They can attack the urogenital system, leading to urethritis, pelvic inflammatory disease, and pyelonephritis.
• There is a potential for bacteremia and meningitis if it enters the bloodstream.

Mycobacterium Tuberculosis

• Mycobacterium tuberculosis is an obligate human pathogen that replicates in macrophages.
• Tuberculosis is characterized by the formation of a granuloma.
• Primary infection starts in the lungs via respiratory transmission, then can spread to lymph nodes, renal/genital tract, bone, GI tract, and meninges.
• Tuberculosis is especially dangerous in People Living With HIV
• The Bacillus Calmette-Guérin (BCG) vaccine for tuberculosis is not widely administered in the US.
• The BCG vaccine is a live attenuated vaccine that can produce false positives on tuberculosis skin prick tests.

TB Granuloma

• TB granulomas consist of macrophages, multinucleated giant cells, epithelioid cells, and foamy cells, surrounded by lymphocytes.
• Granulomas are a form of immune tissue that protects the pathogen.
• During latency, there is no active release of bacteria
• Reactivation happens with a compromising immune event, making it infectious and easily spreads.

Mycobacterium Leprae

• Mycobacterium leprae is an obligate intracellular pathogen that causes Hansen's disease (Leprosy)
• Long term contact with an infected person is necessary to spread the disease.
• Mycobacterium leprae tends to infect superficial structures like skin, nerves, eyes, or nasal cavities.
• The incubation period is very long at 3-10 years.
• Disease severity is determined by Host immune response
• Treatment involves analgesics for pain, corticosteroids for swelling, and Dapsone.

Leprosy - Type 1 vs. Type 2

• Patients alternate between stages depending on immune system responses.
• Type 1 is tuberculoid which is milder, less infectious, and associated with effective immune response and restriction of infection.
• Characteristics of tuberculoid include:
  • Few lesions with 5 or fewer granulomatous lesions
  • Dry and scaly lesions with irregular edges.
  • Negative skin smear tests
• Type 2 is lepromatous which is severe, disseminated, and infectious.
• Characteristics of lepromatous include:
  • Ineffective immune response.
  • Widespread lesions with thickened skin and nerve damage
  • Lion face
  • Positive skin smear test
• Borderline leprosy is in the middle of Type 1 & 2 & immunologically unstable

Florence Sabin

• Florence Sabin was a scientist and “First Lady of American Science” born in 1871.
• She attended all-women Smith College in Northampton, MS, and Johns Hopkins Medical School.
• In 1896, Sabin was 1 of 14 women in a class of 45 to attend Johns Hopkins Medical School
• She created a brain model of the neonatal brain stem and proved lymphatic vessels bud out from blood vessels.
• In 1917, she became the first woman to become a full professor at Hopkins.
• Sabin became a research scientist for the Rockefeller Institute and Research Committee of the National Tuberculosis Association.
• She advocated for more women to become doctors and lobbied for more tuberculosis education.
• Her campaigning led to the creation of "Sabin Health Laws" which allowed more funding for TB hospitals
• In 1925, she was the first woman elected to the National Academy of Sciences.
• Additionally, she won 15 honorary doctorates and awards from the National TB Association.