(incomplete) Chlamydia and Rickettsia Flashcards
HOST ORGANISMS and diagnosis are important
List some common characteristics of intracellular pathogens.
Gm- by phylogeny, but not analyzed by Gm stain (OBLIGATE intracellular pathogens) Small size (~300nm) Bacteria-like cell walls
Why is Chlamydia an obligate intracellular pathogen? Describe the two stages in its developmental cycle.
Cannot make ATP - depends on host cell ATP
- Elementary bodies: small, non-multiplying, with rigid bacterial-like cell wall; this form transmits infection
- Initial bodies (aka reticulate bodies): larger, actively multiplying, lack rigid cell wall, noninfectious
List the steps in the intracellular growth cycle of Chlamydia.
- Elementary bodies induce phagocytosis by host cell (can enter non-phagocytic cells this way)
- Elementary bodies -> initial bodies via loss of cell wall, increase in size, and RNA synthesis
- Initial bodies divide by binary fission
- Some progeny converted back to elementary bodies -> further spread
What organisms are affected by Chlamydia?
Humans, other mammals, birds
List the three known human pathogens in Chlamydiaciae, how many serotypes, and what they cause (briefly).
Chlamydophilia psittaci: one serotype, causes psittacosis
Chlamydophilia pneumoniae: one serotype, pneumonia in adults
Chlamydia trachomatis: different serotypes cause a variety of things
Chlamydophilia psittaci: reservoir, transmission, pathogenesis, detection
AKA “parrot fever”
Zoonosis - infects birds, -> constant fecal excretion
–Mostly subclinical in birds, but can increase in malnutrition and crowding
Transmission: inhaling fresh bird feces
Pathogenesis: generalized infection, -> fever, headache
–Severe -> extensive INTERSTITIAL PNEUMONIA
Detection: isolatable from blood or sputum
Chlamydophilia pneumoniae: disease caused, transmission
Causes 10% of pneumonia (atypical pneumonia)
Transmission: person to person via respiratory aerosols (no birds)
Chlamydophilia trachomatis serotypes D-K in adults: disease caused, transmission, symptoms, diagnosis, treatment
Nongonococcal urethritis - common venereal disease (non-gonococcal = no N. gonorrhea)
Mostly asymptomatic in males, frequently asymptomatic in females
- -Symptom: purulent urethral discharge
- -Increases likelihood of HIV transmission
- -Can -> severe disease/scarring of epididymus or Fallopian tubes -> infertility
Diagnosis: rapid PCR of urine specimens
Treatment: single high dose of azithromycin for both sexual partners
Chlamydophilia trachomatis serotypes A-C: disease caused, transmission, symptoms, treatment
Trachoma
Transmission: mechanical (finger to eye) and by flies under conditions of poor hygiene
Symptoms: chronic reinfection of conjunctiva -> infolding of eyelashes -> corneal scarring and blindness
Treatment: annual treatment with azithromycin, surgery
Chlamydophilia trachomatis serotypes L1-L3:
Lymphogranuloma venereum: venereal disease, more invasive than serotypes D-K
FINISH
Treatment of Chlamydia
MUST ENTER CELLS
Tetracyclines work well
Azithromycin preferred
Diagnosis of Chlamydia
NO CULTURE
Check for group antigen shared by all ChlamydiaFINISH
Chlamydophilia trachomatis serotypes D-K in neonates: disease caused, transmission, symptoms, diagnosis, treatment
Inclusion conjunctivitis and infant pneumonia
Transmission: from infected mother to neonate at birth or environmental contamination
Symptoms:
Inclusion conjunctivitis:
FINISH
Basic properties of Rickettsia
Mostly arthropod-transmitted
Intracellular growth cycle, but CAN make their own ATP
Rickettsia prowazekii:
Epidemic typhoid fever
First multiplies in capillary endothelial cells
Incubation period: 10 days
Symptoms: fever, severe intractable headache, rash 4-7 days later
–Frequently fatal in children
Transmitted by body lice: human -> louse -> human -> louse
- -Scratching increases transmission
- -Aggravating factors: poor hygiene, famine, war
- -Also maintained in flying squirrels
Treatment: tetracyclines
Diagnosis: PCR detection, serological tests for specific antigens, LFTs
Prevention: louse control
What is Brill-Zinsser disease?
A recrudescent disease that occurs due to R. prowazekii FINISH
Rickettsia typhi:
Endemic murine typhus
Hosts: rats, ground squirrels
FINISH
Rickettsia rickettsii:
Rocky Mountain spotted fever
Symptoms: fever, headache, arthritic pains, abdominal pain, N/V
Incubation period: < 1 week
Transmission:
Treatment:
Diagnosis: fluorescent Ab tests on skin biopsy -> immediate diagnosis
Prevention: suitable clothing to avoid ticks
FINISH
Rickettsia akari:
Rickettsial pox
Incubation period: primary skin lesion + incubation period of 1 week
Symptoms: fever, chills, headache, rash
Transmission: mouse mite -> mouse -> mouse mite -> humans
–Often in urban setting combined to large apartment complexes
Coxiella burnetii:
Q fever
Transmission: inhalation of pathogen associated with carcasses of farm animals
-> sheep/goat/cow/cat -> tick -> sheep/goat/cow/cat -> placental tissue with spores -> humans
Symptoms: interstitial pneumonia, fever, headache, elevated LFTs, sometimes rash (FINISH)
Ehrlichioses: what are they, two types and what each infects, symptoms, treatment
Newly emerging tick-borne diseases
- -Monocytic ehrlichiosis: infects monocytes
- -Granulocytic ehrlichiosis: infects granulocytes
Symptoms: fever, lymphocytopenia, elevated LFTs
Treatment: tetracycline