Exam #4: Bacterial Infections of the URT II Flashcards
What is conjunctivitis? What are the symptoms of conjunctivitis?
- Pinkeye, or infection of the eye surface/ conjunctiva
- Increased tears
- Conjunctival redness
- Photophobia
- Eyelid swelling*
- Significant pus secretion*
These symptoms typically differentiate bacterial conjunctivitis from viral conjunctivitis
What are the causative agents of conjunctivitis?
- Haemophilus influenzae
- Streptococcus pneumoniae
*Moraxella lacunata, enterobacteria & Neisseria gonorrhoeae can also infect the conjunctiva, but do so to a lesser extent
What are the characteristics of Haemophilus Influenzae?
- Small & hard to see
- Gram (-)
- Rod
What other infections can haempphilus influenzae cause?
- Epiglotitis
- Otitis media
- Sinusitis
How is conjunctivitis treated?
- Prevention of spread by removal from school or daycare
- Hand washing, STOP rubbing eyes, don’t use common towels
- Gentacmicin or ciprofloxacin eye drops
List the characteristics of Streptococcus pneumoniae. What type of hemolysis does streptococcus pneumoniae have?
- Gram +
- Encapsulated
- Diplococcus known as a pneumococcus
- Alpha hemolysis
Remember that Strep. pnemoniae is one of the major groups to have alpha-hemoylsis- green on blood agar.
What is otitis media?
Infection of the middle ear–tympanic membrane
What is otitis media commonly caused by?
- Streptococcus pneumoniae (GpC)
- Haemophilus influenzae (GnR)
- Moraxella catarrhalis (GnR)
What are the most common agents that cause sinustitis?
- Streptococcus pneumoniae (GpC)
- Haemophilus influenzae (GnR)
- Moraxella catarrhalis (GnR)
Same organisms as OM
What is the difference between beta & alpha hemolysis?
- Beta= complete lysis
- Alpha= incomplete that looks green on the blood agar plate
*Gamma= no lysis
Remember, a-hemolysis= strep. pneumoniae
In commercials for pneumonia vaccines, which bacteria are they targeting?
Streptococcus pneumoniae
*Note that this vaccine has decreased not only the annual cases of OM by almost 1 million, it has also decreased the need for pediatric intubation by 20%
In the immunocompromised, what do severe streptococcus pneumoniae infections lead to?
- Sinusitis
- OM
- Lobar pneumonia
- Meningitis
What are the two genera in the family chlamydiaceae?
- Clamydia= trachomatis
- Chlamydophila= psittaci & pneumoniae
What are the characteristics of Chlamydophila?
- V. small
- Obligate intracellular parasite
*Previously thought to be viruses
What is the difference between an elementary body & a reticulate body?
Chlamydia has a unique developmental cycle; they can take on two different forms:
1) Elementary body= metabolically inactive but infectious
2) Reticulate body= metabolically active but non-infectious
What can chlamydia trachomatis cause?
- Trachoma
- Adult inclusion conjunctivitis
- Neonatal conjunctivitis
- Infant pneumonia
- Urogenital infections
Describe the pathogenesis of Chlamydia Trachomatis.
- Direct destruction of host cells during replication (in the cell, grows, lyses the host cell)
- Host inflammatory response
How do chlamydia trachomatis gain access to the body
1) Infectious EB attaches to the susceptible host & is phagocytosed
2) Inhibition of phagolysosome fusion
3) Hours later EB’s reorganize into larger metabolically active RB’s
4) Synthesis of DNA occurs utilizing host energy
Does C. trachomatis lead to long-lasting immunity?
Not really; rather, infection induces vigorous inflammatory responses to subsequent infection, which can cause vision loss in chronic ocular infection
How serious is the disease?
Can be very serious & lead to blindness if left untreated.
What are the signs of adult inclusion conjuncitivitis?
- Same serovars as genital infections (STD)
- Occurs in sexually active adults
- Mucopurulent discharge
- Keratitis
- Corneal infiltrates
- Some vascularization
What is neonatal conjunctivitis?
Infants exposed to C. trachomatis at birth
- 5-12 days after birth the eyelids swell
- Untreated leads to conjunctival scarring & corneal vascularization
What are the symptoms of infant pneumonia?
Onset 2-3 weeks after birth, caused by C. Trachomatis
- Bronchitis
- Dry cough
- Afebrile
What can Chlamydophila pneumoniae cause?
This is also known as the TWAR pathogen (Taiwan acute respiratory agent)
- Pneumonia- most severe infections involve only one lobe
- Bronchitis
- Sinusitis
most common in adults & most
What pathogens is Chlamydophilia pneumoniae difficult to differentiate between?
Mycoplasma pneumoniae
Legionella pneumophila
Respiratory viruses
Thus, treat BOTH Mycoplasma pneumoniae
How do you differentiate chlamydia?
PCR- nucleic acid amplification
Complement fixation test
What is Chlamydophila psittaci associated with?
Psittacine birds- parrots, parakeets…etc.
Describe the pathogenicity of Chlamydophilia psittaci.
- Infection by respiratory tract
- Bacteria spread to reticuloendothelial cells
- Seeded due to hematogenous spread
- Lymphocytic inflammatory response on the alveolar & interstitial spaces
Describe the infectious process in OM.
1) OM begins with infection of the nasal chamber & nasopharynx
2) Infection spreads upwards trough the eustachian tube to the middle ear
3) Infection damages ciliated cells, resulting in inflammation & swelling
4) Damaged Eustachian tube cannot move secretions–>pressure from pus & fluid build-up
How is OM caused by streptococcus pneumoniae or H. influenzae treated?
Ampicillin
List the characteristics of Haemophilus influenzae.
- Small
- Pleomorphic
- Gram (-)
- Rods or coccobacilli
What is Diptheria? What are the symptoms?
Diptheria is a deadly toxin mediated disease. Symptoms include:
- Mild sore throat
- Slight fever
- High fatigue
- Malaise
- Dramatic neck swelling (cervical lymphadenopathy)
- Whitish/ gray mucous membranes
How is Diptheria controlled?
Toxoid vaccine i.e. a vaccine against the toxin that diptheria produces
What organism causes Diptheria?
Corynebacterium
List the characteristics of Corynebacterium.
- Gram (+) rod that looks like Chinese letters
- Variable shape
- Non-motile
- Non-spore forming
What is the major virulence factor of Diptheria?
Diptheria exotoxin
*Note that diptheria did not originally have this, it was lysogenized by a bacteriophage
Describe the pathogenesis of Diptheria.
- Not an invasive pathogen
- Stays on the surface & releases toxin that diffuses and absorbs into the bloodstream
- Causes a classic gray-white membrane of clotted blood, epithelial cells of the mucous membrane, & leukocyte infiltrate
What is the Diptheria toxin? What is its mechanism of action?
AB subunit
- A= inactivation of elongation factor-2 (EF-2) to stop protein synthesis & induce cell death (enzyme)
- B= binding
Where is severe damage seen in individuals that survive Diptheria?
- Heart
- Kidneys
- Nerve cells
Describe the progression of conjunctivitis caused by C. Trachomatis.
1) Follicular conjunctivitis i.e. diffuse inflammation of the conjunctiva
2) Conjunctiva scarring–eyelids turn inward
3) Turned in eyelids abrade the cornea
–>Blindness
How do you treat all Chlamydia infections?
Macrolides
- Erythromycin
- Azithromycin
Tetracycline
Levofloxacin
