Tuberculosis Quiz

Spirochetes, Mycobacteria, and Other Bacteria

• Spirochetes, mycobacteria, and other bacteria are diverse groups of bacteria with varying characteristics
• Mycobacteria are slender rods with lipid-rich cell walls, resistant to staining and decolorization, making them acid-fast
• Mycobacterial infections are intracellular and usually result in slow-growing granulomatous lesions that cause tissue damage
• Examples of mycobacterial diseases include tuberculosis, caused by Mycobacterium tuberculosis
• Mycobacteria are long, slender rods, non-motile, strictly aerobic, and non-resistant to UV
• Mycobacteria are resistant to drying and ultraviolet irradiation, but susceptible to heat
• Mycobacteria are frequently complex and form wax-like compounds, making them hydrophobic and acid-fast
• Mycobacteria causes TB; about one-third of the world's population is infected with M. tuberculosis
• Mycobacteria are prevalent in some Asian and sub-Saharan African nations and highly associated with HIV infection

Learning Objectives

• Learning objectives include characteristics of mycobacteria, actinomycetes, rickettsiae, and spirochetes, as well as diseases caused by each

Atypical Bacteria

• Atypical bacteria are a diverse group of bacteria that don't fit into typical classifications

Mycobacteria and Actinomycetes

• Mycobacteria and Actinomycetes are resistant to stains and cannot be removed
• They have a thick cell wall rich in lipids
• Mycobacteria are slender rods that contain mycolic acids
• Actinomycetes are filamentous and gram-positive
• Actinomycetes, are also opportunistic pathogens, causing various infections

Overview

• Mycobacteria are slender rods with lipid-rich cell walls, resistant to staining and decolorization.
• They generally cause slow-growing granulomatous lesions.
• Mycobacterial infections are often intracellular.
• Mycobacteria are important because they cause major tissue destruction

Medically Important Bacteria

• The slide presents a chart illustrating medically important bacteria, including descriptions of their structural characteristics, pathogenicity, and potential medical relevance.

Mycobacteria

• Mycobacteria are long, slender, non-motile rods.
• They are strictly aerobic.
• They are resistant to drying but not heat or UV
• Their cell walls are complex with lipids (mycolic acids)
• They are strongly hydrophobic
• Mycobacteria are slow-growing, forming highly hydrophobic surfaces

Tuberculosis

• Tuberculosis (TB) is a contagious bacterial disease caused by M. tuberculosis
• TB is transmitted through aerosols produced when infected people cough, sneeze, or speak
• Prevention is available through BCG vaccines, and chemotherapy is available for treatment
• Current estimated prevalence of TB globally is approximately 30 million active cases around the world

Epidemiology

• Patients with active pulmonary tuberculosis shed large numbers of organisms via aerosolized droplets
• Person-to-person transmission is the main mode of contagion

Primary Disease Initial Phase

• Primary tuberculosis is usually acquired through the respiratory tract
• The initial lesion develops in small bronchioles or alveoli in the midlung periphery
• Local mononuclear phagocytes engulf the organisms, initiating an inflammatory response

Tuberculosis Signs and Symptoms

• Common signs and symptoms associated with tuberculosis include blood cough, fever, chest pain, chills, long-term cough, weight loss, and night sweats

Laboratory Identification

• Diagnosing active pulmonary tuberculosis involves identifying M. tuberculosis in clinical specimens.
• Nucleic acid amplification PCR and culture on special agar is commonly employed.

Treatment

• Several chemotherapeutic agents are effective against M. tuberculosis
• The likelihood of resistant strains emerging necessitates multiple drug therapy
• Isoniazid, rifampin, ethambutol, streptomycin, and pyrazinamide are the most commonly used first-line drugs due to efficacy and a generally acceptable degree of toxicity
• Treatment usually takes 8-12 months.

Prevention

• Latent TB chemotherapy is given to individuals who are tuberculin-positive and asymptomatic
• Directly observed therapy (DOT) is implemented to ensure compliance with medication regimens.

Mycobacterium leprae

• Causes leprosy, notably in places with less-developed economies
• Mycobacterium leprae feels pain loss on limbs, a notable feature of the bacteria.
• It's acid fast.

Leprosy

• Worldwide, approximately 10 to 12 million cases are estimated.
• Leprosy is transmitted through close contact with infected individuals
• Clinical significance: Chronic granulomatous skin condition, specifically of peripheral nerves; usually occurring as tuberculoid or lepromatous leprosy

Actinomycetes

• Gram-positive, filamentous, and opportunistic microorganisms

Nocardia

• Members of the Nocardia genus are aerobic soil microorganisms
• Nocardiosis, a disease of humans and domestic animals, is not contagious.
• Nocardiosis often presents as pneumonia, typically with a chronic course involving abscesses, extensive tissue necrosis (tissue death), and formation of cavities

Chlamydiae

• Small bacteria that are obligate intracellular parasites
• Diseases of the genitourinary tract, including cases of non-gonococcal urethritis, and ocular infections
• Often infects respiratory tract, leading to ailments such as psittacosis and atypical pneumonia

Medically Important Bacteria (Chart)

• The slide displays a chart categorizing medically important bacteria based on cell wall presence

Chlamydia Trachomatis

• C. trachomatis is the most common sexually transmitted bacterial disease in the U.S.
• Causes non-gonococcal urethritis (NGU)
• C. trachomatis can also cause trachoma (an eye infection)
• Symptoms vary from irritation to blindness

Trachoma

• Trachoma is an ancient disease that remains prevalent in developing nations
• Well described in Egyptian writings from around 3800 BC

Chlamydia Psittaci

• Transmission occurs primarily through the inhalation of dust contaminated with bird secretions or feces.
• Birds are the primary reservoirs for this zoonotic infection.
• Typically, the human infection involves the lower respiratory tract
• Symptoms such as fever, hacking dry cough, and flu-like symptoms are common.

Chlamydia Pneumoniae

• Chlamydia pneumoniae is a significant cause of community-acquired respiratory infection
• This infection does not display seasonal trends and often presents in worldwide epidemic outbreaks

Chlamydia species

• Not routinely stained via gram staining, but rather using darkfield microscopy
• Small, round-to-ovoid shaped organisms.
• Contain double layered lipid bilayers
• Obligate intracellular parasites; replicate within vacuoles.

Rickettsia, Ehrlichia, Coxiella, and Bartonella

• These are gram-negative intracellular bacteria.
• Spotted fevers, typhus, and similar diseases are caused by them
• Ehrlichia and Anaplasma are prominent human genera.
• Coxiella burnetii causes Q fever.

Rickettsial Diseases

• Presents a summary of selected rickettsial diseases, including the organisms, vectors, reservoirs, and their prevalence in the United States.

Mycoplasma

• Mycoplasma lack cell walls, thus are classified as prokaryotic organisms with no peptidoglycan cell walls
• They're extremely small.
• The diseases they cause include atypical pneumonia, genital infections, and intrapartum infections caused by Mycoplasma pneumoniae, Mycoplasma hominis, and Ureaplasma urealyticum

Spirochetes

• Spirochetes are long, slender, motile, flexible organisms with a corkscrew or helical shape.
• They are often gram-negative, but their staining characteristics may vary among species
• They are important because they can be aerobic, anaerobic, or facultatively anaerobic
• They can form cultures (cell-free and tissue culture), but some cannot

Medically Important Spirochetes

• Important human pathogens: Treponema pallidum (syphilis), Borrelia burgdorferi (Lyme disease), and Borrelia recurrentis (recurrent fever).

Structural Features of Spirochetes

• Spirochetes have a unique structure for motility.
• Periplasmic flagella (axial filaments) are oriented axially, propelling the spirochete in a corkscrew-like movement

Treponema Pallidum

• Treponema pallidum is the causative agent of syphilis.
• It's a sexually transmitted bacterial infection that can be congenitally acquired
• Diagnosed via immunofluorescent or dark-field microscopy

Syphilis

• Starting with a painless chancre (ulcer), syphilis progresses through stages categorized by symptoms.
• Untreated syphilis can lead to significant long-term complications, including neurological and cardiovascular damage in its tertiary stage.

Treponema pallidum

• The causative organism of syphilis is extremely fastidious and fragile.
• It cannot be routinely cultured and requires specific techniques like immunofluorescence or darkfield microscopy for detection

Clinical Significance of Syphilis

• Syphilis presents in stages which correlate with site of inoculation or infection (genitals or mouth in the initial stage in most cases).
• Organisms spread to the rest of the body via the lymph and blood.
• An asymptomatic period lasting up to 24 weeks follows, after which the secondary stage arises

Secondary Stage of Syphilis

• Systemic involvement, including hepatitis, meningitis, nephritis, or chorioretinitis, may occur.
• After resolution of the secondary stage, a latent period can follow.
• Approximately 40% of untreated cases progress to a tertiary stage, associated with nervous system degeneration, cardiovascular complications (aneurysms), and granulomatous lesions (gummas)

Congenital Syphilis

• T. pallidum can cross the placenta and infect the fetus during pregnancy (after week 10 of pregnancy).
• The infection can cause death, stillbirth, and a range of structural and central nervous system abnormalities

Laboratory Identification of Syphilis

• Syphilis is commonly diagnosed serologically via fluorescent treponemal antibody absorption (FTA-ABS)
• Microscopically, examination of primary and secondary lesions using immunofluorescence or dark-field illumination

Treatment of Syphilis

• Penicillin remains the primary treatment choice for primary and secondary syphilis
• Alternative options like erythromycin or tetracyclines may be utilized if penicillin is not suitable

Treponema species

• Penicillin is the primary treatment choice for various stages of syphilis.
• Alternative choices are possible, depending on patient sensitivity

Borrelia Burgdorferi

• Borrelia burgdorferi is the causative agent for Lyme disease.
• It's a gram-negative spirochete transmitted by ticks.
• Mice are often the primary reservoirs for these ticks
• Humans are often secondary hosts.
• Lyme disease typically begins with a red circular rash at the site of the tick bite

Pathogenesis of Lyme Disease

• Transmission occurs through tick bite (requires at least 24 hours).
• Mice are a primary reservoir for the spirochete
• Deer are host animals for the ticks

Clinical Significance of Lyme Disease

• The first stage involves the appearance of a red, circular rash (erythema migrans) at the bite site 3–32 days post-bite
• The condition may have different stages; chronic arthritis and or central nervous system (CNS) diseases may occur.

Borrelia Species

• Borrelia burgdorferi causes Lyme disease,
• Borrelia recurrentis causes relapsing fever.
• These bacteria are gram-negative spirochetes

Leptospira Interrogans

• Leptospirosis is caused by the bacterium L. interrogans, a gram-negative spirochete.
• It's transmitted by contaminated animal urine through water or food.
• The infection initially presents with fever, typically one to two weeks post-infection; it can also present with systemic invasion of the liver, kidneys, and central nervous system, leading to jaundice, hemorrhaging, tissue necrosis, and or meningitis like conditions.

Leptospira species

• Diagnostic techniques include dark-field microscopy or wet-mount examinations.

Test your knowledge on tuberculosis with this quiz covering aspects such as infection rates, transmission methods, treatment challenges, and the role of mycobacteria. Explore critical questions about the disease caused by Mycobacterium tuberculosis and its impact on the global population.