Intracellular Bacteria Flashcards
Pregnant women are more susceptible to getting disease from listeria infection. Why and in which trimester?
The 3rd trimester because that is when cell-mediated immunity is lowest. Bacteria will leave GI and proliferate in placenta.
What are some consequences of listeria infection in a pregnant woman?
preterm labor
may cause abortion
stillbirth
intrauterine infection
Why should pregnant women steer clear of deli meat and soft cheeses?
Listeria is commonly found in deli meat since it prefers a cooler environment. Listeria is more pathogenic in pregnant women than in general population
How to prevent listeria?
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.
List the 5 recurring themes of intracellular bacteria.
- evade humoral immunity and surface defenses
- use infected macrophages for transport (i.e. trojan horses)
- host cell takeover by type 3 secretion systems
- actin-based motility and cell-cell spread
- effective antibiotics must not only penetrate the membrane, but also be effective inside cell (tetracycline)
What is the abx of choice to give to someone with an intracellular bacterial infection? What are the contraindications?
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)
Intracellular bacteria can be broken down into obligate and facultative groups. List 2 that belong to the obligate group.
- chlamydia
2. rickettsial
list gram, shape, and type of hemolysis of listeria monocytogenes
gram positive rod and beta-hemolytic
Describe listeria’s motility
tumbling motility based on T-sensitive flagella
Reservoir and transmission of listeria
environment, contaminated food; fecal-oral
What is lysterolysin?
lysterolysine is a factor that listeria has to escape endocomes and roam freely
What is actA?
actA is a factor that listeria has to form actin rockets for motility
What is the pathogenesis of listeria?
- escape GI
2. causes complications of pregnancy, meningitis, abscess, endocarditis, septic arthritis, osteomyelitis
Listeria Treatment
Antibiotics, specifically ampicillin for 6 weeks with gentamicin combination for the first week.
When will IV antibiotics be administered to patients infected with listeria?
When the patient presents with CNS issues and bacteremia.
What are some characteristics associated with an obligate intracellular bacteria?
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
Rickettsia is very difficult to stain, but when it does stain, it’s a gram
negative rod
A vector is an organism that transmits infections btw hosts. What is Rickettsia’s vector? Any exceptions?
Rickettsia are vectored by arthropods, except for c. burnetti
Rocky Mountain Spotted Fever is caused by and manifests as; what’s the vector?
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.
All viruses are
intracellular pathogens
List the facultative intracellular bacteria. What does that mean?
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
Can you grow chlamydia or rickettsia on agar plates?
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
What does intracellular pathogenesis allow these bacteria to evade?
they can evade humoral and surface-innate immunity
What are the two common functions of the type 3 secretion system in intracellular bacteria?
- enhance phagocytosis by the target cell type
2. alter the endosome so that lysosomes fail to fuse to it
What do the abx for intracellular bacteria have to be really good at?
These abx (tetracycline: doxycycline) have to be really good at penetrating the membrane and working inside cells.
What are the virulence factors carried by rickettsia?
adhesion: OMP A & B
cell entry: Type IV secretion system
escape from endosome: phospholipase A2
actin-based cell-cell spread: ActA
Why is Chlamydia pathogenesis unusual?
It uses elementary and reticulate bodies.
- bacteria will attach and penetrate cell host membrane
- in endosome, type III secretion system will prevent binding to lysosomes
- elementary bodies (metabolically inert) reorganize themselves into reticulate bodies (metabolically active)
- reticular bodies modify endosomes forming inclusion bodies
- produce progenies via binary fission
- increasing # of bacteria will start packing back down to elementary bodies
- inclusion bodies will either rupture and fill cells with elementary and reticulate bodies or get to cell surface and infect other cells
Which 4 infections are associated with reactive arthritis?
- chlamydia
- salmonella
- shigella
- yersinia
When patient presents with chlamydia, what should the physician do in addition to prescribing doxycycline?
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.
What is the leading cause of pelvic inflammatory disease? What does pelvic inflammatory disease increase one’s odds of?
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.
Where do you find elementary bodies and describe their characteristics
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.
What are reticulate bodies?
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.
Explain actin-based motility and cell-cell spread
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)
Enterics use M cells as
gateway to exterior surface of intestine, works around colonization resistance and tight junctions on interior surface
Listeria primarily infects
fetus across placenta, newborn during delivery, pregnant women and immunocompromised adults
Listeria uses which virulence factor to pop phagosome and escape into cytosol
lysteriolysin
If you suspect listeria infection, what is one symptom previously healthy adults will have
gastroenteritis
In immunocompromised patients, listeria infection manifest as these 2 symptoms
meningitis and bacteremia (sepsis)
Pathogenesis of Rocky Mountain Spotted Fever
- bacteremia
- invade and multiply in vascular endothelium
- blood vessels leak as infected cells die, causes petechial rash
Female patients with genital chlamydia may have these symptoms which can be used for diagnosis
mucopurulent endocervical discharge, bleeding, dysuria, abdominal pain, progression to PID, reactive arthritis
Male patients with genital chlamydia may have these symptoms which can be used for diagnosis
Urethral discharge, dysuria, scrotal pain, reactive arthritis
Infants with congential chlamydia may have these symptoms which can be used for diagnosis
ocular trachoma
When will chlamydia culture be required?
if case has legal implications
What are easier and cheaper ways to detect chlamydia in the lab besides culturing? What’s the downside?
ELISA, PCR and fluorescent hydridization, but more likely to give a false positive
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).
True
After endocytosis, listeria escapes the endosome via _______ and uses actin-based motility to spread between cells.
lysterolysin
ricketsia is trophic for which cells?
endothelial cells causing leakage and rocky spotted mountain fever
Chlamydia enters cells via
type III secretion system
