Intracellular Bacteria

Question 1

Pregnant women are more susceptible to getting disease from listeria infection. Why and in which trimester?

Answer 1

The 3rd trimester because that is when cell-mediated immunity is lowest. Bacteria will leave GI and proliferate in placenta.

Question 2

What are some consequences of listeria infection in a pregnant woman?

Answer 2

preterm labor
may cause abortion
stillbirth
intrauterine infection

Question 3

Why should pregnant women steer clear of deli meat and soft cheeses?

Answer 3

Listeria is commonly found in deli meat since it prefers a cooler environment. Listeria is more pathogenic in pregnant women than in general population

Question 4

How to prevent listeria?

Answer 4

Cook food thoroughly; wash cooking supplies and eating utensils thoroughly; avoid unpasteurized dairy; also in immunosuppressed and pregnant ppl, avoid deli meat and soft cheeses.

Question 5

List the 5 recurring themes of intracellular bacteria.

Answer 5

1. evade humoral immunity and surface defenses
2. use infected macrophages for transport (i.e. trojan horses)
3. host cell takeover by type 3 secretion systems
4. actin-based motility and cell-cell spread
5. effective antibiotics must not only penetrate the membrane, but also be effective inside cell (tetracycline)

Question 6

What is the abx of choice to give to someone with an intracellular bacterial infection? What are the contraindications?

Answer 6

Tetracycline is the abx of choice, but should not be given to pregnant women since it interferes with fetal bone growth. Tetracycline might cause teeth problems in children. (***doxcycline for lyme disease)

Question 7

Intracellular bacteria can be broken down into obligate and facultative groups. List 2 that belong to the obligate group.

Answer 7

1. chlamydia

2. rickettsial

Question 8

list gram, shape, and type of hemolysis of listeria monocytogenes

Answer 8

gram positive rod and beta-hemolytic

Question 9

Describe listeria’s motility

Answer 9

tumbling motility based on T-sensitive flagella

Question 10

Reservoir and transmission of listeria

Answer 10

environment, contaminated food; fecal-oral

Question 11

What is lysterolysin?

Answer 11

lysterolysine is a factor that listeria has to escape endocomes and roam freely

Question 12

What is actA?

Answer 12

actA is a factor that listeria has to form actin rockets for motility

Question 13

What is the pathogenesis of listeria?

Answer 13

1. escape GI

2. causes complications of pregnancy, meningitis, abscess, endocarditis, septic arthritis, osteomyelitis

Question 14

Listeria Treatment

Answer 14

Antibiotics, specifically ampicillin for 6 weeks with gentamicin combination for the first week.

Question 15

When will IV antibiotics be administered to patients infected with listeria?

Answer 15

When the patient presents with CNS issues and bacteremia.

Question 16

What are some characteristics associated with an obligate intracellular bacteria?

Answer 16

1- cannot grow on agar plates
2- have to be grown on tissue plates with human host cells (like viruses)
3- require host cell machinery to replicate

Question 17

Rickettsia is very difficult to stain, but when it does stain, it’s a gram

Answer 17

negative rod

Question 18

A vector is an organism that transmits infections btw hosts. What is Rickettsia’s vector? Any exceptions?

Answer 18

Rickettsia are vectored by arthropods, except for c. burnetti

Question 19

Rocky Mountain Spotted Fever is caused by and manifests as; what’s the vector?

Answer 19

It is caused by a ricketsial infection leading to petechial rash due to blood leaking from infected blood vessels. The vector is the dog tick.

Question 20

All viruses are

Answer 20

intracellular pathogens

Question 21

List the facultative intracellular bacteria. What does that mean?

Answer 21

Facultative intracellular bacteria can survive and replicate outside of host cells as well. These are Neisseria (gram neg cocci), enterics (gram neg rods), mycobacter (acid fast), bacilli, legionella

Question 22

Can you grow chlamydia or rickettsia on agar plates?

Answer 22

No, because they are obligate intracellular bacteria that require human host cells so need to be grown on tissue culture. The facultative intracellular bacteria can grow on agar plates

Question 23

What does intracellular pathogenesis allow these bacteria to evade?

Answer 23

they can evade humoral and surface-innate immunity

Question 24

What are the two common functions of the type 3 secretion system in intracellular bacteria?

Answer 24

1. enhance phagocytosis by the target cell type

2. alter the endosome so that lysosomes fail to fuse to it

Question 25

What do the abx for intracellular bacteria have to be really good at?

Answer 25

These abx (tetracycline: doxycycline) have to be really good at penetrating the membrane and working inside cells.

Question 26

What are the virulence factors carried by rickettsia?

Answer 26

adhesion: OMP A & B
cell entry: Type IV secretion system
escape from endosome: phospholipase A2
actin-based cell-cell spread: ActA

Question 27

Why is Chlamydia pathogenesis unusual?

Answer 27

It uses elementary and reticulate bodies.

1. bacteria will attach and penetrate cell host membrane
2. in endosome, type III secretion system will prevent binding to lysosomes
3. elementary bodies (metabolically inert) reorganize themselves into reticulate bodies (metabolically active)
4. reticular bodies modify endosomes forming inclusion bodies
5. produce progenies via binary fission
6. increasing # of bacteria will start packing back down to elementary bodies
7. inclusion bodies will either rupture and fill cells with elementary and reticulate bodies or get to cell surface and infect other cells

Question 28

Which 4 infections are associated with reactive arthritis?

Answer 28

• chlamydia
• salmonella
• shigella
• yersinia

Question 29

When patient presents with chlamydia, what should the physician do in addition to prescribing doxycycline?

Answer 29

The physician should test for other STDs b/c chlamydia often appears as a co-infection. Also, physician should offer safe sex counselling as well as treat the partners to prevent reinfection. Reinfection occurs due to affected partners than from antibiotic resistance.

Question 30

What is the leading cause of pelvic inflammatory disease? What does pelvic inflammatory disease increase one’s odds of?

Answer 30

Genital chlamydia is a leading cause of pelvic inflammatory disease which can increase one’s chance of having an ectopic pregnancy and will have chronic pain.

Question 31

Where do you find elementary bodies and describe their characteristics

Answer 31

Elementary bodies are involved in the pathogenesis of chlamydia. They are rugged, small, infectious bodies with rigid outer membrane and can bind to receptors. They can survive host to host transfer.

Question 32

What are reticulate bodies?

Answer 32

Reticulate bodies are the other cell type involved in chlamydia pathogenesis. They are metabolically active, but delicate. They are non-infectious, replicating, and can synthesis own DNA, RNA and proteins but require host ATP. They also have a fragile gram negative membrane.

Question 33

Explain actin-based motility and cell-cell spread

Answer 33

This is one of 5 characteristics of intracellular bacteria. These bacteria have virulence factors like “ActA” (listeria) which will generate an actin tail behind bacteria. Bacteria can eventually ram through cell membrane into next cell (ex. listeria, shigella)

Question 34

Enterics use M cells as

Answer 34

gateway to exterior surface of intestine, works around colonization resistance and tight junctions on interior surface

Question 35

Listeria primarily infects

Answer 35

fetus across placenta, newborn during delivery, pregnant women and immunocompromised adults

Question 36

Listeria uses which virulence factor to pop phagosome and escape into cytosol

Answer 36

lysteriolysin

Question 37

If you suspect listeria infection, what is one symptom previously healthy adults will have

Answer 37

gastroenteritis

Question 38

In immunocompromised patients, listeria infection manifest as these 2 symptoms

Answer 38

meningitis and bacteremia (sepsis)

Question 39

Pathogenesis of Rocky Mountain Spotted Fever

Answer 39

1. bacteremia
2. invade and multiply in vascular endothelium
3. blood vessels leak as infected cells die, causes petechial rash

Question 40

Female patients with genital chlamydia may have these symptoms which can be used for diagnosis

Answer 40

mucopurulent endocervical discharge, bleeding, dysuria, abdominal pain, progression to PID, reactive arthritis

Question 41

Male patients with genital chlamydia may have these symptoms which can be used for diagnosis

Answer 41

Urethral discharge, dysuria, scrotal pain, reactive arthritis

Question 42

Infants with congential chlamydia may have these symptoms which can be used for diagnosis

Answer 42

ocular trachoma

Question 43

When will chlamydia culture be required?

Answer 43

if case has legal implications

Question 44

What are easier and cheaper ways to detect chlamydia in the lab besides culturing? What’s the downside?

Answer 44

ELISA, PCR and fluorescent hydridization, but more likely to give a false positive

Question 45

T/F: Intracellular pathogenesis allows human pathogens to use infected macrophages for transport as trojan horses around the body and evade humoral and surface-innate immunity (actin-based cell-cell spread).

Answer 45

True

Question 46

After endocytosis, listeria escapes the endosome via _______ and uses actin-based motility to spread between cells.

Answer 46

lysterolysin

Question 47

ricketsia is trophic for which cells?

Answer 47

endothelial cells causing leakage and rocky spotted mountain fever

Question 48

Chlamydia enters cells via

Answer 48

type III secretion system