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.
What is the antibiotic given for ABRS?
It is amoxicillin-clauvalunate.
What is the general definition of pneumonia?
When alveoli and bronchioles get filled with fluid, causing there to be gas exchange reduction.
Pneumococcal pneumonia is caused by what?
Streptococcus pneumoniae
What are the types of pneumonia that Streptococcus pneumonia causes?
Community acquired pneumonia, hospital acquired pneumonia, and most common cause of bacterial pneumonia
What are the symptoms of pneumococal pneumonia?
fever, chills, congestion, cough, chest pain, labored breathing, rust colored sputum.
What is the pathogenesis of strep. pneumo?
Pneumococci inhaled from pharynx –> goes to lungs –> bacteremia and meningitis.
Bacteria damage alveoli, allowing RBCs, WBCs, and blood plasma to enter the lung–> fluid fills alveoli up–> reduces gas exchange.
IgA protease destroys IgA.
What is strep throat?
What causes the strep throat?
What age is most affected?
Inflammation of the pharynx.
Streptococcus Pyogenes
5- 15 years
What are the signs and symptoms of strep throat?
Pain during swallowing, back of pharynx is red, swollen tonsils (white patches or streaks of pus).
Petechiae on soft and hart palate, swollen lymph nodes in the front of the neck (bilateral, anterior lymphadenitis).
There is no runny nose, conjunctivitis, diarrhea, or cough.
Bad breath, headache, fever, malaise.
Can spread to larynx –> cause laryngitis –> hoarseness
Can spread to bronchi –> bronchitis–> coughing
What can strep throat cause other than strep throat?
Scarlet fever.
What can strep throat lead to?
can lead to Acute glomerulonephritis. Immune sequelae.
What are the symptoms of glomerulonephritis?
They are hematuria, foamy urine, hypertension, edema
What can be the consequences of immune sequelae?
Immune sequelae can cause there Acute Rheumatic Fever which can cause damaged heart valves (Syndham’s chorea and St. Vitus dance)
What are the virulence factors of Strep. pyogenes?
Hyaluronic capsule, and C3b inhibiting M protein. C5a peptidase ( inhibits lymphocytes).
Streptokinase (hydrolyses blood clots) and Streptolysins (hydrolyse RBCs, WBCs, and platelets).
Pyrogenic toxins stimulate lymphocytes to secrete cytokines ( fever, rash, shock. superantigens)
How is strep throat transmitted?
Resp. Droplets
How is strep throat diagnosed?
RADT (back of throat swabbing). If RADT is positive and classic symptoms are present, then antibiotic should be given
What should be done when RADT is negative?
If RADT is negative, then throat culture should be done (24-48 incubation).
This is the gold standard for detecting strep.
What does provider do in the case of + throat culture and symptoms?
You prescribe antibiotics
With no symptoms but - RADT what does it mean?
It means asymptomatic carriers of S. Pyogenes.
What is serology used for in diagnosis of strep throat?
retrospective diagnosis, when there is immune sequelae
What is the causative organism of Diphtheria?
Corynebacterium Diphtheriae (gram + rods)
What 4 characteristics of diphtheria?
They are black colonies on Tindale’s media, v shaped palisade arrangement, Club shape, pleomorphic
What are metachromatic granules on Loffler’s media?
They are phosphate granules seen at one end or both ends of the rods.
Where is corynebacterium diphtheriae found on humans?
It is found on skin, respiratory tract, GI and GU tract.
What is mass immunization and how does it affect diphtheriae?
It means that there is reduced prevalence C. diphtheriae as normal microbiota of throat and pharynx.
What are symptoms of diphtheria?
Sore throat, localized pain, fever, oozing of fluid in throat (intracellular fluid, platelets, WBCs, bacteria, dead pharyngeal and laryngeal cells)
What can the oozing fluid in throat in diphtheria cause?
It can tonsils, uvula, roof of the mouth, pharynx, larynx
–> can block respiration –> death.
HB-EGF is for what?
It is heparin binding EGF- like growth factor. It influences cell cycle progression, molecular chaperone regulation, cell survical, ect.
How does the diphtheria toxin work?
It binds to the HB-EGF and is endocytosed into the cell. There the toxin (B) then binds to the EF-2 and the toxin (A) causes there to be the transfer of ADP-ribose from NAD to EF-2, halting protein synthesis.
What is the transmission of diphtheria?
Respiratory droplets, skin contact, fomites
Where does the Diphtheria toxin originate from?
Bacteriophage transduction
What are the diagnostic characteristics of diphtheria?
pseudomembrane
Elek test
PCR for diphtheria gene (determines presence of gene for toxin but not the toxin production) .
ELISA: diphtheria toxin production.
What is an Elek test?
It is a test used for diagnosis of corynebacterium diphtheriae.
A positive PCR in diphtheria diagnosis calls for what next? How about a negative PCR culture?
A positive PCR culture is then confirmed with culture.
Negative PCR helps rule out diagnosis.
What is the prevention for diphtheria?
For kids: It is DTaP vaccine. (15-18 months of age, 2, 4, 6 years)
For preteens: It is Tdap 11-12 years
For adults: It is Td or Tdap every 10 years
What is the treatment for diphtheria?
Antitoxin at early stages
Antibiotics
Surgery and tracheostomy ar later stages.
What are needed after treatment in diphtheria?
post treatment pharyngeal cultures to confirm eradication.
When is diphtheria PEP?
given to close contacts of diphtheria patient.
Erythromycin/penicillin for 14 days.
What are the characteristics of H.Influenzae?
Oxidase positive, gram - coccobacilli, humans are only known host.
Growth factor requirement testeing for hemin (X factor) and NAD (V factor). –> staph aureus provides this.
Slide agglutination serotyping to determine capsular serotype.
What is agar used to grow H.influenzae?
chocolate agar (for NAD and hemin)
Uncapsulated H. Influenzae causes what?
It causes nasopharyngeal colonization, which then causes a noninvasive infections (sinusitis, otitis media)
What does the HiB/ capsulated influenzae cause?
It causes there to be invasive infections.
How does capsule help in the case of HiB infection?
It prevents opsonization.
K. Pneumoniae is what kind of bacteria?
Gram - bacteria aerobic bacillus from our gut. Normal microbiota of GI tract and human feces.
What type of pneumonia does Klebsiella cause?
Friedlander’s Disease. What
Healthy people usually ——– get klebsiella infections.
do not.
Who are the at risk patients for klebsiella infections?
patients on ventilators or on IV catheters. Patients who are on long course antibiotics.
What is the mortality rate of klebsiella?
50% even with antibiotics
What are the symptoms of klebsiella?
currant jelly sputum
rapid acute onset of high fever and chills
What is the pathogenesis of klebsiella?
Destruction of alveolar cells leading to bacteremia. When bacteria die, they can cause release of LPS, causing shock and DIC
What do drug resistant Klebsiella produce?
Carbapenemase and metallo beta lactamase
Why is drug resistant Klebsiella so dangerous?
As carbapenems are often he last line of defense for gram - infections that are resistant to other antibiotics.
How is Klebsiella transmitted?
It is transmitted through contaminated hands of healthcare workers, contamination of the environment, aspiration of gastrointestinal material.
How is prevention of Klebsiella done?
Aseptic techniques by healthcare workers.
How is diagnosis of Klebsiella done?
Gram stain, culture, and biochemical tests
What is the treatment of Klebsiella?
Supportive care, ventilation, and antibiotics
Avycaz (Ceftazidime-Avibactam) which is reserved when limited and no alternate antibiotics.
Legionanaire’s disease causes what? What type of bacteria is Legionnaire’s disease caused by?
severe, atypical pneumonia.
Caused by gram negative bacteria
How are we exposed to leigionella pneumophilia?
Freshwater protozoa release legionella in vesicles. Humans inhale these vesicles and get the disease.
In humans, the parasite can grow inside alveolar macrophages and monocytes.
What are symptoms of legionnaire’s disease?
- fever/chills
- dry non-productive cough
- headache
- pleurisy (inflammation of pleurae)
- complications can involve other structures
6/ Untreated mortality is 50%
Pontiac fever is
milder form of legionella with no pneumonia
What are risk factors of legionnaires disease?
smokers, elderly, those with chronic respiratory issues and immunocompromised people.
Why is legionella seasonal?
As AC ducts, showers, vaporizers, other water using things can spread legionella.
Which water conditions promote legionella?
stagnant, warm water with temps between 20 and 50 degrees centigrade.
What is the antibiotic treatment route for mild and severe legionnarie’s
oral, IV
Mycoplasma Pneumoniae causes what?
Tracheobronchitis /chest cold
Walking pneumonia
leading type of pneumonia in children and young adults
What are some descriptors of Mycoplasma Pneumoniae?
- encapsulated, lack cell walls (so pleomorphic- sterols in cell membranes)
- Smallest free living microbes (light microscopy and no visible turbidity in liquid cultures)
- Considered gram- positive
What are the symptoms of mycoplasma pneumoniae?
Usual symptoms of fever, malaise, headache, sore throat.
More directed symptoms are excessive sweating, persistent, unproductive cough.
What is the pathogenesis of mycoplasma pneumoniae?
Attachment to base of cilia causes it to stop beating. Allows colonization and buildup of mucus –> colonization eventually kills epithelial cells.
Bacteria can be endocytosed by host cells and could aid in latency or chronic disease state.
What is the virulence factor that mycoplasma produces?
CARDS (community acquired respiratory distress syndrome) toxin
What are the main modes of transmission for this?
Lack of cell wall means susceptible to dessication and transmission is person to person by airborne droplets and occurs through close contact.
It is exclusive human pathogen, and patients are infective even when on antimicrobials.
What is the diagnosis of mycoplasma?
Culture forms fried egg colonies after 2- 6 weeks
What is the treatment of mycoplasma?
Macrolides is TOC, floroquinolones, tetracyclines for older children and adults,
