Small Gram-negative Pathogens Flashcards
Chlamydiae General Characteristics
Small (.25 um- .8 um) Gram-negative No murein in cell walls Obligate intracellular pathogens Energy parasites Complex developmental cycle
Chlamydiae species
C. trachomatis
C. pneumonia
C. psittaci
C. pecorum
Chlamydial infections
Leading cause of preventable blindness in the world
Most common agents of sexually transmitted bacterial infections
Localized
Chlamydial spread
The 4 F's Fingers Flies Fomites Fornication
Chlamydia Trachomatis General Characteristics
Genital tract infections
Usually asymptomatic in females
Can be chronic or acute
Asymptomatic carriage results in most scarring and damage
During birth, infants can contract infection leading to conjunctivitis and pneumonia
C. Trachomatis infection
Elementary bodys enter into epithelial cells by receptor-mediated endocytosis
EBs modify vesicles by maintaining ph above 6.2 and prevents vesicle fusion with lysozymes
Vesicles are also modified with host glycolipids for camo
EBs change into larger intracellular active organisms and synthesize molecules using host metabolites and energy - divide by binary fision
Organisms develop slowly (2-3 days per cycle)
Other Chlamydial diseases
Trachoma
Lymphogranuloma venerum
Trachoma
Caused by C. trachomitis strains
Inflammation of the conjunctiva that can cause blindness or scaring of the cornea
Spread by direct contact with eye, nose, and throat secretions form affected individuals (or towels)
Lymphogranuloma venerum
STD
Systemic, invasive infection apparent in the lumph nodes that drain the genital tract
Predominately in developing countries
C. pneumonia general characteristics
Perhaps most prevalent chlamydial pathogen in humans
50% of people up to age 20 have been infected, and 80% of older adults
Either asymptomatic or acute respiratory response, but chronic respiratory infections have been associated with asthma, CF, and lung cancer
C. pneumonia treatment
Metabolic active RB forms are the targets of antimicrobials
Must penetrate 4 membrane layers - host cell plasma membrane, inclusion membrane, chlamydial outer membrane, and chlamydial cytoplasmic membrane
Antibiotics must be maintained for a long time - these organisms grow slow
Rickettsiae Characteristics
Small gram-negative rods
Obligate intracellular bacteria - but not an energy parasite
May lack certain metabolites for growth
No flagella or endospores
Must be cultivated in animals, eggs, or cell cultures
Rickettsiae Transmission
Only members of the tick family Ixodidae are naturally infected with Rocky Mountain spotted fever
Once infected, a tick cna carry the pathogen for life
Bacteria can be passed on to humans during blood meal of these ticks
Rickettsiae Spread and Multiplication
Attach to vascular endothelial cells (small blood vessels) and induce endocytosis
Once inside, the lyse the phagosome and enter the cytosol
Mode of exit form the cell varies
Rickettsiae Damage
Lysis of cells results in leakage of blood (rash/hemorrhagic spots)
Organisms can travel to other vessels including the heart and brain
75% of patients will clear the infection even before antimicrobial treatment
Diagnosis of Rickettsioses
Problematic, because during first visit, patients typically don’t have a rash or fever, and may not be aware of tick bite
Clinical diagnosis tests - antibody titers, fluorescent antibody assay, complement fixation, latex agglutination
What are the different types of Typhus fevers?
R. prowazekii
R. typhi
Orienta tsutsugamushi
R. prowazekii
Typhus fever
Recrudescent typhus - reactivation of the dormant agent seen in the US
Transmitted by human lice
Reservoirs are humans and flying squirrels
R. typhi
More prevealent and widespread for of typhus fever
Murine typhus
Transmitted by rats and their fleas
Orienta tsutsugamushi
Scrubs typhus
Variety of antigenic types
No rash as observed in others
Erlechia general characteristics
Obligate intracellular bacteria
Infects mostly monoctes and macrophages
Transmitted by lonestar tick
Causes Human Granulocyte Ehrlichiosis (HGE) and Human Monocyte Ehrlichiosis (HME)
Causes fever, malaise, headache, and myalgia
Develops within host cell vacuoles first as reticulate cells (RC) and then as dense-core cells
Mycoplasma characteristics
Smallest organisms capable of growth on cell-free media
Lack a cell wall - penicillin has no effect
Cell membranes contain sterols
Found in mammals and birds
What four species of Mycoplasma cause disease?
M. pneumoniae
M. genitalium
M. hominis
Ureaplasma urealyticum
M. pneumoniae encounter and entry
Humans are the only reservoir
Spread through close-contact groups by respiratory droplets
Adhere to respiratory epithelium with terminal adhesion structure
M. pneumoniae spread, multipication, and damage
Main cells of he inflammatory response are lymphocytes
Largely limited to respiratory mucosa, but doesn’t reach alveoli
Not highly destructive, but impairs ciliary function
Can cause cold hemmagglutins, causing RBCs to stick at cold temps
Can also cause encephalitis or a rash
M. genitalium
Newest emerging human pathogen
Causes urethritis, cervicitis, endometritis, PID
Isolated from synocial and respiratory fluids
M. hominis and U. urelyticum
Frequently associated with diseases in newborns
Present in most of the sexually active populations
