slides 1 misc - 4.3

Vocabulary flashcards covering unique structural traits, life cycles, virulence factors, and associated diseases of Mycoplasma, Ureaplasma, Rickettsiae, and Chlamydia discussed in the lecture.

Mycoplasma pneumoniae

Very small, pleomorphic bacterium that lacks a cell wall, contains membrane sterols, and causes atypical (walking) pneumonia by adhering to and killing respiratory epithelial cells.

• attaches to epithelial cells, kills them

• Buildup of mucus, other infections

• Fever, malaise, sore throat, etc. walking pneumonia

• No cell wall! (but strong cytoskeletal framework)

• Can’t treat with penicillins

Mycoplasma/ureaplasma - pathogenic bacteria misc

have unusual properties

• Very small, pleomorphic (change shape depending on environment) (cocci to filaments)

• Have no cell walls, but have sterols in their membranes

• Require numerous growth factors to grow (fastidious)

require host cells =

obligate intracellular

Walking (Atypical) Pneumonia

Mild, community-acquired pneumonia characterized by fever, malaise, sore throat, and persistent cough, most commonly produced by Mycoplasma pneumoniae or Chlamydia pneumoniae.

Respiratory Distress Toxin

Virulence factor of Mycoplasma pneumoniae that depletes host cell nutrients and destabilizes membranes, contributing to pulmonary symptoms.

Ureaplasma urealyticum

Cell wall–less, urease-positive bacterium transmitted sexually; a major cause of non-gonococcal urethritis (NGU).

• Sexually transmitted, cause of urethritis

• Often referred to as NGU (Non-gonococcal urethritis), infections caused by something other than N. gonorrhoeae.

• Similar to M. pneumoniae, but urease +

Non-gonococcal Urethritis (NGU)

Inflammation of the urethra caused by organisms other than Neisseria gonorrhoeae, notably Ureaplasma urealyticum and Chlamydia trachomatis.

about 50% of cases

• Chlamydia infections are the most common STI, but even more are infected and asymptomatic

Urease

Enzyme produced by Ureaplasma urealyticum that splits urea, releasing toxic NH4⁺ and damaging host tissues.

Rickettsiae (Genus)

Gram-negative, obligate intracellular pleomorphic rods with leaky membranes; infect endothelial cells and are usually transmitted by arthropod vectors, causing spotted fevers and typhus.

• Gram negative, very small, obligate parasites

• Leaky membranes?

• Most diseases spread by vectors

• Rickettsiae infect endothelial cells lining blood vessels, avoid digestion in lysozome

• Have LPS, generate fever

• Damage to capillaries produces spots, rashes

• Damage to vessels deprives organs of oxygen

Rickettsia rickettsii

Species transmitted by tick bites (rodents as reservoir) that causes Rocky Mountain spotted fever with rash and vascular damage.

Rocky mountain spotted fever

• Spread by tick bite; rodents are the reservoir

• Most common through southeast, mid-south

Rocky Mountain Spotted Fever

Severe tick-borne illness by R. rickettsii, presenting with fever, headache, and petechial rash that begins on wrists/ankles and spreads centrally.

Rickettsia prowazekii

Louse-borne Rickettsia species responsible for epidemic typhus, typically occurring in crowded or unhygienic conditions.

epidemic typhus

• Humans primary host; vector is the louse

• Disease spread in crowded, unhygienic conditions

Epidemic Typhus

Acute febrile illness with high fever, confusion, and truncal rash caused by Rickettsia prowazekii; transmitted by human body lice.

Rickettsia typhi

Flea-borne Rickettsia species that causes murine (endemic) typhus, maintained in rodent populations.

murine/endemic typhus

• present in rodent population, vector is the flea

Murine (Endemic) Typhus

Milder typhus form caused by R. typhi, contracted from flea bites associated with rodents.

Chlamydia (Genus)

Very small, obligate intracellular bacteria lacking peptidoglycan; exhibit a two-stage life cycle and are spread by direct contact rather than vectors.

• Very small, obligate intracellular parasites

• Cell and outer membrane, but no peptidoglycan

• Spread directly rather than by vectors

Two stage life cycle

• Elementary body: tiny (0.2-0.4 µm) and inert

• Spore-like: dormant and resistant

• Infectious: form that moves between cells

• Reticulate body: 0.6-1.5 µm, metabolically active, reproduce inside host cells

Elementary Body

Dormant, extracellular, infectious form of Chlamydia (0.2-0.4 µm) that survives outside host cells and initiates infection.

Reticulate Body

Metabolically active, non-infectious intracellular form of Chlamydia (0.6-1.5 µm) that replicates within host cell vacuoles.

Chlamydia trachomatis

Species that infects mucous membranes and conjunctiva, causing trachoma, NGU, and lymphogranuloma venereum; most common bacterial STI agent.

infects cells of mucous membranes, conjunctiva. Mostly eye & STI

• Infection kills cells, stimulates inflammation which also causes cell destruction

Trachoma

Chronic conjunctival infection by C. trachomatis leading to eyelid scarring, inward-turned lashes, corneal abrasion, and potential blindness.

- leading cause of non-traumatic blindness. Caused by certain strains.

• Infection of conjunctiva causes scarring, turning in on eyelashes which scratch cornea.

• Scarred cornea, with ingrown blood vessels, obscure vision.

• Eye infections of newborns prevented with antibiotic drops/salve.

Lymphogranuloma Venereum (LGV)

Invasive C. trachomatis infection producing genital lesions and painful inguinal lymphadenopathy (buboes) that may rupture; can cause genital elephantiasis.

• Lymph nodes in genital region (inguinal) become enlarged (buboes), may even rupture.

• Blocked lymph ducts lead to genital elephantiasis, other damage in genital region.

• 85% of women asymptomatic; others can develop PID; scarring of uterine tubes can lead to sterility, ectopic pregnancy.

Pelvic Inflammatory Disease (PID)

Ascending infection of female reproductive organs often due to asymptomatic C. trachomatis infection, risking tubal scarring, sterility, and ectopic pregnancy.

Chlamydia pneumoniae

Chlamydial species causing bronchitis, sinusitis, and atypical pneumonia; clinically resembles infection by Mycoplasma pneumoniae.

• Cause of bronchitis, sinusitis, pneumonia

• Hard to distinguish from Mycoplasma pneumonia

Obligate Intracellular Parasite

Microorganism that must reside within host cells for energy production and replication, exemplified by Rickettsiae and Chlamydia.

Sterols in Bacterial Membranes

Lipid components incorporated by mycoplasmas to stabilize their cell wall–less membranes, a feature uncommon among bacteria.

Phospholipases

Enzymes produced by Rickettsiae and Ureaplasma urealyticum that degrade host cell membranes, aiding intracellular spread and tissue damage.