Small Gram-negative Pathogens

Question 1

Chlamydiae General Characteristics

Answer 1

Small (.25 um- .8 um)
Gram-negative
No murein in cell walls
Obligate intracellular pathogens
Energy parasites
Complex developmental cycle

Question 2

Chlamydiae species

Answer 2

C. trachomatis
C. pneumonia
C. psittaci
C. pecorum

Question 3

Chlamydial infections

Answer 3

Leading cause of preventable blindness in the world
Most common agents of sexually transmitted bacterial infections
Localized

Question 4

Chlamydial spread

Answer 4

The 4 F's
Fingers
Flies
Fomites
Fornication

Question 5

Chlamydia Trachomatis General Characteristics

Answer 5

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

Question 6

C. Trachomatis infection

Answer 6

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)

Question 7

Other Chlamydial diseases

Answer 7

Trachoma

Lymphogranuloma venerum

Question 8

Trachoma

Answer 8

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)

Question 9

Lymphogranuloma venerum

Answer 9

STD
Systemic, invasive infection apparent in the lumph nodes that drain the genital tract
Predominately in developing countries

Question 10

C. pneumonia general characteristics

Answer 10

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

Question 11

C. pneumonia treatment

Answer 11

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

Question 12

Rickettsiae Characteristics

Answer 12

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

Question 13

Rickettsiae Transmission

Answer 13

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

Question 14

Rickettsiae Spread and Multiplication

Answer 14

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

Question 15

Rickettsiae Damage

Answer 15

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

Question 16

Diagnosis of Rickettsioses

Answer 16

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

Question 17

What are the different types of Typhus fevers?

Answer 17

R. prowazekii
R. typhi
Orienta tsutsugamushi

Question 18

R. prowazekii

Answer 18

Typhus fever
Recrudescent typhus - reactivation of the dormant agent seen in the US
Transmitted by human lice
Reservoirs are humans and flying squirrels

Question 19

R. typhi

Answer 19

More prevealent and widespread for of typhus fever
Murine typhus
Transmitted by rats and their fleas

Question 20

Orienta tsutsugamushi

Answer 20

Scrubs typhus
Variety of antigenic types
No rash as observed in others

Question 21

Erlechia general characteristics

Answer 21

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

Question 22

Mycoplasma characteristics

Answer 22

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

Question 23

What four species of Mycoplasma cause disease?

Answer 23

M. pneumoniae
M. genitalium
M. hominis
Ureaplasma urealyticum

Question 24

M. pneumoniae encounter and entry

Answer 24

Humans are the only reservoir
Spread through close-contact groups by respiratory droplets
Adhere to respiratory epithelium with terminal adhesion structure

Question 25

M. pneumoniae spread, multipication, and damage

Answer 25

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

Question 26

M. genitalium

Answer 26

Newest emerging human pathogen
Causes urethritis, cervicitis, endometritis, PID
Isolated from synocial and respiratory fluids

Question 27

M. hominis and U. urelyticum

Answer 27

Frequently associated with diseases in newborns

Present in most of the sexually active populations