Chapter 21

Rickettsia

Non-motile, aerobic, gram-, intracellular parasites that live in cytosol of host cell

Rickettsia

Hematoxylin and R. typhi: are generally used for visualization

R. rickettsii & R. typhiArthropod vectrs

continuously released via exocytosis

R.prowazekii

fills up host cell until cell lyses and parasites release

Arthropod vectors

carry pathogens from one host to another by both mechanical and biological transmission

Rickettsia rickettsii

causes rocky mountain spotted fever

Rickettsia rickettsii

hard ticks (Dermacentor) transmit among humans and rodents, bacteria dormant for several hours in salivary glands of ticks, replicate in mammal's circulatory system

Rickettsia rickettsii

develop rashes on wrist, ankles, soles, and palms andl ater spreads to trunk, petechial homerrhages

Rickettsia rickettsii

Treatment includes removal of ticks

Rickettsia rickettsii

Treatment is deoxycycline and removal of ticks

Ricketts prowazekii

causes epidemic typhus

Rickettsia prowazekii

Human body louse transmits bacteria to humans, flying squirrels serve as reservior, humans are primary host

Rickettsia prowazekii

Recurrent disease is called Brill-Zinsser disease

Rickettsia prowazekii

Treatment with doxycycline, tetracycline, chloramphenicol

Rickettsia prowazekii

Prevent with vaccine and personal hygiene

Rickettsia typhi

Causes endemic or murine typhus, major reservoir is rodents, fleas ar vectors

Rickettsia typhi

Disease is not fatal, rash restricted to chest and abdomen, endemic on every continent

Rickettsia typhi

Prevent by avoiding arthropod vectors

Rickettsia typhi

Treatment is doxycycline

Orientia

Different rRNA sequence, thicker cell wall, minmal slime layer compared to ricketts

Orientia

Mites are reservoir and vector

O.tsutsugamushi

Causes scrub typhus, endemic ares are Asia, Australia, Japan, India

Orientia

Prevent by avoiding exposure to mites

Orientia

No vaccine, treatment is doxycycline and azithromycin

Ehrlichia and Anaplasma

Ticks transmit disease to humans, triggers its own phagocytosis by leukocytes, grow in phagosomes

E. chaffeensis

causes human monocytic ehrlichiosis

Anaplasma phagocytophilum

Causes anaplasmosis

Ehrlichia and Anaplasma

Diagnosis difficult due to non-specific symptoms

Ehrlichia and Anaplasma

Prevent by avoiding ticks, treatment is doxycycline

Chalmydias

Virus-like size but contain DNA, RNA, and 70S ribosomes

Chalmydias

Non-motile, no cell walls, Obligate intracellular parasites, no vectors as hosts, lack enzymes to synthesize ATP

Elementary bodies

tiny cocci, dormant, infective forms

Reticulate bodies

larger pleomorphic, noninfective

Chalmydia trachomatis

Only one strain affects mice, all others infect humans

Chalmydia trachomatis

specifically infects cells with receptors for elementary bodies (conjuctiva and various mucous membranes) (trachea, bronchi, urethra, uterus, anus, rectum). Enters the body through abrasions and lacerations

Chalmydia trachomatis

most common reportable STD in the US

Chalmydia trachomatis

Reinfection at same site can result in severe hypersensitivity reactions leading to blindness, sterility, or sexual dysfunction

Lymphogranuloma venereum

transient genital lesions, swollen inguinal lymph nodes, genital sores, nongonococcal urethritis, proctitis

Trachoma

Ocular disease, pathogen multiplies in cells of conjuctiva and destroys them, leading cause of traumatic blindness, infection occurs during childbirth

Chalmydia trachomatis

Diagnosis by demonstrating bacteria in cells from site of infection

Chalmydia trachomatis

Treatment is antibiotics for genital and ocular infections, surgical corrections can prevent blindness

Chalmydia trachomatis

Prevention by abstinence, don
t get an STD

Chlamydia psittaci

Causes ornithosis (parrot fever), transmitted by birds, doxycyline for treatment, diagnosis is difficult

Spirochetes

Thin, tightly coiled, helically shaped G- bacteria, can burrow through tissue

Axial Filaments

In spirochetes, composed of endoflagella located in periplasmic space between cytoplasmic membrane and outer membrane

Treponema

Human pathogen only, T. pallidum pallidum is most widespread, causative agent of syphilis

Treponema

Can grow in rabbits, monkeys, and rabbit epithelial cells, visualized by phase contrast and dark field microscopy, can't be grown in cell free media

Treponema

Produce hyaluronidase and glycocalyx, difficult to identify virulence factors because the pathogen cannot be cultured

Treponema

Transmitted via sexual contact, endemic among sex workers, homosexuals, and users of illegal drugs

Congenital syphilis

can occur when infection spreads from an infected mother to her fetus, can result in mental retardation or fetal death

Primary disease

Starts with painless, reddened lesion, called a chancre at site of infection 10-21 days from exposure. Usually form around external genitalia

Secondary syphilis

starts with invasion of bacteria in bloodstream, sore throat, fever, myalgia, lymphoadenopathy and rashes that include palms and soles of the feet

Latent phase

Commences after several week, may last up to 30 years

Tertiary syphilis

Syphilitic lesions called gummas- rubbery painful swollen lesions due to inflammation, causes dementia, blindness

Treponema

Diagnosis is by antibody tests against antigens of T. pallidum, tertiary syphilis is difficult to diagnose

Treponema

Penicillin is the drug of choice

Treponema

Prevention by abstinence and safe sex

Borrelia

Lightly staining, G- spirochetes, causes Lyme and Relapsing fever

Lyme disease

Borrelia burgdorferi is the causative agent, characterized by arthritis, infected children may have Bell's palsy, utilizes manganese instead of iron for ETC

Hard ticks (Ixodes)

Vectors for lyme disease must remain on host for 48 hours, mice and deer are reservoirs

Lyme disease

Expansing bulls-eye rash, severe arthritis that can last for years, diagnosed mostly through serological test

Lyme disease

Prevention by avoiding ticks using DEET

Louse born relapsing fever

Borrelia recurrentis is causative agent, transmitted by human body louse

Tick-borne relapsing fever

Several borrelia species can transmit this disease, transmitted by soft ticks of genus Ornithodirus

Relapsing fever

Characterized by recurring episodes of septicemia and fever due to body's efforts to remove spirochetes, diagnosis by observation of spirochetes, treatment with doxycycline and erythromycin