Exam #4: Bacterial Infections of the URT II Flashcards Preview

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Flashcards in Exam #4: Bacterial Infections of the URT II Deck (41):

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?



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?



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



How do you treat all Chlamydia infections?

- Erythromycin
- Azithromycin


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