Microbiology Flashcards
What are commensal bacteria? `
They are basically the bacteria which act on host immune system and prevent pathogen colonization and invasion. `
How do commensal bacteria help to prevent infection?
They help by competing for nutrients and sites of adhesion, by producing products ( promote mucosal immunoglobulin production), and signals `
What are some of the normal colonizers of the the oropharynx and nasopharynx?
Group C or G streptococci, Group A Streptococcus, Strep. pneumoniae, H.Influenzae or Moraxella catarrhalis, N.Meningitidis
What age group does Strep. Pneumo affect?
6-100% of infants and toddlers, 25% of children ages 3 months to 4 years, 5-10% of older and younger people
What age group does Group A strep affect?
20% of children are colonized.
H. influenzae and Moraxellla Catarrhalis affects whom?
large percentage of infants and toddlers
N. Meningitidis affects mainly whom?
It affects mainly adolescents and toddlers. Coloniztion can lead to bacteremia, meningitis, or septic arthritis.
Streptococcus Aureus can cause ——-.
Can cause pneumonia (lower respiratory tract disease)
1/3rd of adults are colonized in their upper respiratory tracts and can cause serious disease.
Strep. Pneumo can cause
pneumonia
Enterobacteriaceae and non fermenting gram- negative bacilli can cause:
These are among the most common causes VAP.
Colonize URTI in children who have been in the ICU or frequent courses of antibiotics. Can become normal microbiota of ventilated children ICU.
Human rhinovirus aka RV can cause ——.
Is the most prevalent cause of virus induced ——-.
Virus induced asthma attacks.
Most common cause of the common cold. RV infections
What demographic does HRV cause common cold in?
Infection rates among young children can be as high as 8-12 times a year.
What are RV infections are often linked to :
acute otitis media and rhinosinusitis
What is the optimal temperature of RV replication?
32-33 C (cooler temps of the URTI)
Unable to replicate in the GI tract.
What upper respiratory tract diseases including:
Pneumonia, bronchitis, bronchiolitis, and exacerbation.
RVs exacerbate asthma attacks by what percentage?
What other conditions can RVs exacerbate?
50-85% of asthma exacerbations.
CF and COPD
RV is transmitted how?
Inhalation of infectious droplets, direct contact is major route and fomites.
RV Virus survives how long? How is control of RV virus?
Few hours to 4 days on non-porous surfaces, for atleast 2 hours on human skin.
With adequate hand hygiene cleaning surfaces
What is the mechanism behind rhinovirus infection?
Host cell ICAM-1 attaches to the canyon of the virus capsid.
VP1 is the viral attachment protein (immune system responds to a 20 AA stretch in the VP-1 protein)
When is VP-1 20 monomer epitope exposed?
After VP-1 binds to ICAM-1. This is how RV avoids immune system and causes recurrent immune infections.
What is a respiratory viral panel?
It is basically a tests that can identify what resp. viral infection you have.
20 viruses can be identified.
What main viruses can Respiratory viral panels test for?
Influenza A and B, Respiratory Syncytuial virus, human mela-pneumovirus, rhinovirus, human bocavirus, coronavirus, and adenovirus
What are two other conditions that RV virus is linked to other than cold?
Otitis media and rhinosinusistis
What is otitis media?
Inflammation of the middle ear
How is otitis media caused?
Caused by fluid buildup in the eustachian tube, which helps bacteria travel to middle ear from fluid buildup in this tube.
The migration to middle ear is preceded by an acute viral upper respiratory tract tract (URT).
Acute Otitis Media
Acute Otitis Media may develop during or after a cold.
AOM and Antibiotics
No benefit from antimicrobial therapy.
AOM is not of bacterial origin or immune system clears infection even without antibiotics.
When do you prescribe antibiotics?
Prescribe antibiotics in children:
- <6 months of age AOM
- 6 months- 2 years with moderate to severe bilateral AOM
- > 6 months (mod-severe >48 hours and T>39 C
- For non-severe, bilateral AOM in >6 months close followup and antibiotics only if child does NOT IMPROVE in 48-72 hours of symptoms.
What do you do with a child recurrent AOM:
You have tympanostomy tubes
Where the Tympanostomy tubes?
Placed through the tympanic membrane.
Inadequate antibiotic therapy of AOM causes?
Inadequate antibiotic therapy of AOM –> OME and subsequent hearing loss
Otitis Media with Effusion is what?
Fluid in middle ear w/o acute of illness or inflammation of middle ear. Usually follows AOM. Eustachian tube dysfunction is often a predisposing.
OME is most common cause of hearing loss and requires
Antibiotic therapy and surgical management.
Etiologies of Otitis Media
Strep. pnemo, NT-HI, Moraxella Catarrhalis, Alloiococcus Otitidia, Strep. Pyogenes, Staph. aureus.
What is the most common pathogen associated with OME?
Strep. Pneumoniae
H. Influenzae
Strep. Pneumo is what type bacteria?
Gram positive cocci, and catalase negative.
H. Influenzae is what type of bacteria?
It is gram - coccobacili,oxidase positive, non capsulate, satellitism (only grow when there is a streak of staph aureus)
Moraxella Catarrhalis is what type of bacteria? What does it cause?
It is a gram negative diplococci.
Causes AOM in children and exacerbations in adults with COPD
How is moraxella catarrhalis treated?
empirically as it could be neisseria or moraxella
What is the distinguishing sign for moraxella?
Hockey puck sign
What is rhinosinusitis?
is a temporary infection of the sinuses tat often follows respiratory infections.
What is the timeframe for rhinosinusitis?
7- 10 days. Bacterial infections in less than 2% of patients.
Symptom based treatment
What is chronic rhinosinusitis?
lasts at least 12 weeks:
nasal congestion, mucus discharge, decreased sense of smell.
Why is acute bacterial rhino-sinusitis less common in children under the age of 4?
as in younger children these viral infections are usually manifest themselves as AOM which is treated with antibiotics and prevents viral infection from leading to ABRS.
Where does the fluid buildup in otitis media come from?
It comes from the immune remnants of the viral caused UTRI
How do you prevents ABRS?
Stop smoking, saline spray, glucocorticoid nasal sprays.
When are antibiotics given for ABRS?
when infection lasts for more than 10 days, there is high fever and pus filled nasal drainage, and it gets worse after a brief period of improvements.