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Flashcards in Bacterial Infection in Respiratory Disease Deck (86):

What is the leading cause of acute morbidity and visits to the physician?

respiratory illness


What are 75-80% of infectious respiratory illnesses due to?



Do bacterial or viral infections tend to be more severe?



Can a viral infection (like influenza) or allergic response predispose the host for a superinfection by bacteria?

YES leading to obstruction of the airways (due to inflammatory response) and damage to ciliated epithelial cells causing impairment of mucociliary transport.


What bacteria can cause a TYPICAL pneumonia following influenza?

1. Streptococcus pneumoniae (most common)
2. Staphylococcus aureus
3. Haemophilus influenzae


Are specific viruses typically identified?

NO (sometimes in lower respiratory tract infections they are though). Instead we treat the symptoms.


What causes most "colds" (Rhinitis)?

viruses (rhinovirus; most common, coronavirus, adenovirus...)


What bacteria can cause the common cold and can also cause ATYPICAL pneumonia or bronchitis?

- Mycoplasm pneumoniae
- Chlamydia pneumoniae


What causes most pharyngitis?

viruses most often and are self-limiting :)


**** What bacteria can cause pharyngitis?

- Streptococcus pyogenes (strep throat; GAS)
- Corynebacterium diphtheriae (rare due to vaccination)
- Mycoplasm pneumoniae
- Chlamydia pneumoniae


**** What are the common pathogens that can cause otitis media?

- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis


What pathogen causes croup ( laryngotracheobronchitis)?

- parainfluenza viruses


What bacteria causes epiglottitis?

- mostly haemophilus influenza type b (children 2-6).
- Also Strep pyogenes, Strep pneumoniae, Staph aureus to a lesser degree.


What bacteria causes whooping cough?

bordetella pertussis


Can pneumonia be caused by either viruses or bacteria?



Can most pathogens infect anywhere in the airways, even though they have preferred sites?



What is the leading cause of severe respiratory infections in infants?

respiratory syncytial virus (RSV) in both upper and lower respiratory tract


What is the source of many bacterial pathogens?

RESIDENT FLORA of the upper respiratory tract leading to obstruction of the nasal passages and thus sinusitis and otitis media. Its always a balance between immune defenses and bacteria present.


What are the resident bacterial flora?

- anaerobes= in the oral cavity (peptostreptococcus, fusobacterium) and associated with abscesses.
- aerobes= oral cavity and nasopharynx (nonpathologic: streptococcus and neisseria, non-typeable: Haemophilus influenzae, and moraxella catarrhalis).
- occasional or transient flora= strep. pyogenes, strep pneumoniae, or neisseria meningitidis


**** What bacteria can cause otitis externa?

- Staphylococcus aureus
- Streptococcus pyogenes (GAS)
- Pseudomonas aeruginosa (swimmers ear)
* Aspergillus and Candida (fungal)


**** What bacteria can cause community-acquired rhinosinusitis?

same as otitis media:
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis


**** What bacteria can cause hospital-acquired rhinosinusitis?

Gram-negative bacilli:
- Pseudomonas aeruginosa
- Klebsiella
- Proteus
- Enterobacter
Staph aureus (gram-positive)


What are the symptoms of rhinitis (cold)?

stuffy nose, sneezing, rhinorrhea (runny nose), general malaise, headache, watery eyes, sore throat, fever (depending on severity), cough (if pathogen spreads to trachea and bronchi or due to post nasal drip).


What type of mucus secretion corresponds to viral vs. bacterial infection?

- clear, mucoid nasal secretions= viral
- mucopurulent secretions= bacterial infection
*obstruct sinuses (sinusitis) or eustachian tubes (otitis media).


*** What is ACUTE rhinosinusitis?

inflammation or infection of the nasal passages and sinuses (cold symptoms + facial pressure/pain and headache) lasting no longer than 4 weeks.


What is CHRONIC rhinosinusits?

inflammation or infection of the nasal passages and sinuses (cold symptoms + facial pressure/pain and headache) lasting more than 8 weeks or more than 4 episodes a year lasting more than 10 days each.
*most due to fungi.


By what is bacterial rhinosinusits commonly preceded?

acute viral rhinosinusits or allergic rhinitis.


What will you see in allergic fungal sinusitis?

- eosinophils and increases in IgE in response to an allergen, putting the pt at a greater risk of becoming infected with a fungal pathogen (Aspergillus= most common).


What is rhinocerebral disease?

fungal infection that begins as a sinusitis, but then penetrates the bone and enters the CNS (in immunocompromised pts).


What will you see with pharyngitis?

fever, sore throat, tonsillar and pharyngeal erythema, may or may not have exudate and anterior cervical lymphadenopathy.


**** How do you tell if you are dealing with a viral or bacterial pharyngitis?

- If you have an exudate and cervical lymphadenopathy, then you are either dealing with GAS, C. diphtheriae, or EBV (more generalized lymphadenopathy with EBV; mono).
- if you have a cough, it's less likely to be GAS
- if you don't have an exudate or cervical lymphadenopathy, then it could be influenza.


What does bacterial pneumonia often follow?

flu-like illness or URI (viral).


What are the symptoms of bacterial pneumonia?

acute onset, fever, chills, productive cough, SOB, and tachycardia.


Is viral pneumonia more or less severe than bacterial pneumonia?

less severe and more gradual onset (atypical pneumonia, along with chlamydia pneumonia and mycoplasma)


What is important for diagnosing pneumonia?

chest x-ray!!
- definded density and lobular= typical pneumonia
- diffuse, not well defined infiltrates or interstitial pneumonia= atypical pneumonia.


What bacteria can cause ATYPICAL pneumonia?

- Mycoplasm pneumoniae (most common)
- Chlamydia pneumoniae
- Legionella


Does typical or atypical pneumonia have a faster onset?



Does typical or atypical pneumonia have a higher temperature?



Does typical or atypical pneumonia have a productive cough?

- TYPICAL= productive cough with purulent sputum (PMNs).
- ATYPICAL= nonproductive cough (monocytes).


**** What bacteria cause community-acquired TYPICAL (acute) pneumonia?

- Streptococcus pneumoniae
- Haemophilus influenze
- Moraxella catarrhalis
- Staphylococcus aureus
- Klebsiella pneumonia
*Basically the same list as typical pneumonia list earlier.


**** What bacteria cause community-acquired ATYPICAL pneumonia?

- Mycoplasma pneumoniae
- Chlamydia pneumoniae
- Legionella
* Same list as atypical pneumonia list earlier.


**** What additional bacteria can cause hospital-acquired pneumonia?

- Enterobacteriaceae
- Klebsiella
- Serratia marcescens
- Pseudomonas aeruginosa


**** With what is aspiration pneumonia associated?

- anaerobic oral flora= Bacteroides, Prevotella, Fusobacterium, Peptostreptococcus
- aerobic bacteria= same as all other mentioned bacteria.


**** What bacteria can cause a CHRONIC pneumonia?

- Mycobacterium tuberculosis


*** What bacteria can cause NECROTIZING pneumonia and lung abscess?

- TB
- Anaerobic bacteria
- Nocardia
- Klebsiella
- Staph aureus


What are the big respiratory pathogens that can affect the immunocompromised (AIDS pts)?

- Pneumocystis jirovecii
- Mycobacterium avium
- Aspergillus and Candida (fungal)


**** What are the common causes of pneumonia based on age? (picmonic)

- neonates= Group B strep and E. coli
- Children (4 wks-18 yrs)= RSV, Mycoplasma, Chlamydia pneumoniae, and Strep pneumoniae.
- Adults (18-40 yrs)= Mycoplasma, Chlamydia pneumoniae, Strep pneumoniae.
- Adults (40-65 yrs)= Step pneumoniae, Haemophilus influenzae, anaerobes, viruses, Mycoplasma.
- Elderly= Streptococcus pneumoniae, viruses, anaerobes, Haemophilus influenzae, gram negative bacilli.


*** What pneumonia pathogens are associated with alcoholics?

Klebsiella, anaerobes, staph aureus, and strep pneumo


*** What pneumonia pathogens are associated with COPD?

Haemophilus influenzae and Moraxella catarrhalis


*** What pneumonia pathogens are associated with IV drug use?

Staph aureus and Strep pneumo


*** What pneumonia pathogens are associated with HIV?

pneumocystis jirovecii, CMV and histoplams cpsulatum


*** What pneumonia pathogen is most associated with cystic fibrosis?

Pseudomonas aeruginosa


*** What pneumonia pathogen is most associated with ventilation?

Pseudomonas aeruginosa


*** Is Streptococcus pneumoniae associated with military training camps, jails, homeless shelters, and nursing homes?



*** What pneumonia pathogen is associated with contaminated air-conditioning units and hot tubs?



*** What pneumonia pathogen is associated with animals?

Coxiella burnetii and Brucella


How do we distinguish between Streptococcus pyogenes and pneumoniae?

- Streptococcus pyogens (GAS)= beta hemolytic and bacitracin sensitive.
- Streptococcus pneumonia= alpha hemolytic and optochin sensitive.
*Remember both are catalase negative!


**** What is important to remember about Strep pyogenes (GAS)? (sketchy)

- hyaluronic acid capsule (anti-phagocytic via M proteins that block binding of complement component C3b; poor immunogen).
- can cause rheumatic fever and rheumatic heart disease by making antibodies to the M proteins that can cross react with the heart or kidney (acute glomerulonephritis).
- Pyrogenic (erythrogenic) exotoxins= superantigens that activate cytokines and lead to scarlet fever or toxic shock syndrome.
- Streptolysin S and O= lyse luekocytes, platelets, and RBCs. ASO titers measure antibody to streptolysin O to indicate recent infection.


**** What clues should make you suspicious of strep throat?

- children age 5-15 yrs
- sudden onset of sore throat, high fever (100.4), absence of cough, chills, malaise, headache.
- erythematous pharynx
- exudate (50% of cases)
- petechiae on soft palate (small red dots)
- anterior cervical lymphadenopathy


What will you see with SCARLET FEVER (associated with strep strains that produce pyrogenic (erythrogenic) exotoxin Spe A or C)?

- rough, sandpaper-like rash that starts on the chest and spreads to the extremities occurring 1-2 days after onset of pharyngitis. It will fade over 5-7 days followed by desquamation (skin peeling).


What will you see with rheumatic fever following strep throat?

occurs 2 weeks after pharyngitis with fever, migrating polyarthritis, and endocarditis. You can culture because the infection is gone at this point, but you can look at antibody titers to see if there are antibodies against M proteins in circulation. These M antibodies will cross-react to heart tissue and capsule antibodies will cross-react to joints.


How do you treat strep throat?



When is acute glomerulonephritis more likely to occur following a strep infection?

more likely from strep skin infection than strep throat. This again is due to antibodies formed against the M proteins that cross-react with the glomerulus.


What tests do we use to diagnose strep throat?

- throat swab for rapid antigen detection assay (very fast and effective) or you can culture looking for beta-hemolytic, catlase negative, gram + cocci (but this takes over a day to get results).


*** If you are suspicious of strep throat, but the patient has conjunctivitis, cough, or coryza (cold symptoms), should you stick to your suspicion?

NO, its most likely viral.


*** If you are suspicious of strep throat, but the patient has a grayish pseudomembrane, should you stick to your suspicion?

NO this is Corynebacterium diphtheriae!


*** If you are suspicious of strep throat, but you notice vesicles and ulcers, what should this tell you?

its more likely HSV or coxsackievirus


**** What is important to remember about Strep pneumoniae? (sketchy)

- most common bacterial respiratory pathogen and occurs at all levels of the respiratory tract.
- alpha hemolytic, lancet-shaped diplococcus.
- there is an adult vaccine (protects against 23 of the 90 serotypes) and a pediatric vaccine (Prevnar 13 that protects against 13 of the 90 serotypes).
- optochin sensitive
- common for sinusitis and otitis media
- rust colored sputum


What disorders are associated with Staph aureus for URIs?

pneumonia, empyema, and otitis externa


*** What is an empyema?

purulent pleural pus (PMNs and microorgansims) associated with Staph aureus pneumonia, but it is polymicrobial and can be associated with many other bacteria as well.


**** What is important to remember about Haemophilus influenzae? (sketchy)

- gram negative coccobacillus
- requires X factor (hematin) and V factor (NAD) for growth.
- produces IgA protease (cleaves IgA).
- sinusitis, epiglottitis, and otitis media (children mostly)
- pneumonia in elderly or adults with COPD
- nonencapsulated (non-typeable)= part of normal flora and thus opportunistic pathogen.
- capsulated (typeable)= more pathogenic (type b was the worst causing meningitis and epiglottitis in children, prior to "Hib vaccine").


Is epiglottitis considered a medical emergency?

YES (look for 4 Ds):
- dysphagia
- dysphonia
- drooling
- distress
Also hoarseness, barking cough, fever, and pharyngitis.


What are some possible complications of epiglottitis?

bacteremia resulting in meningitis, septic arthritis, or osteomyelitis.


*** What is important to remember about Moraxella catarrhalis?

- gram negative diplocci
- can be part of normal flora of URT
- similar to H. influenzae
- most frequently associated with otitis media and community acquired sinusitis in children.


*** What is important to remember about Bordetella pertussis? (sketchy)

- small gram negative coccobacillus; strict aerobe
- causes whooping cough (pertussis).
- human pathogen (no animal or environmental reservoir) spread human to human via aerosols.
- unvaccinated infants are at greatest risk.
- filamentous hemagglutinin and pertactin mediate attachment to ciliated respiratory epithelial cells and has a tracheal cytotoxin that disrupts mucociliary clearance leading to severe cough.
- stimulates adenylate cyclase/hemolysin, inhibiting leukocyte chemotaxis and phagocytosis.


What are the A and B subunits of Bordetella pertussis?

B= bind lactosylceramide and receptors on phagocytes
A (active subunit)= adds ADP-ribose to membrane G-protein, preventing deactivation of adenylate cyclase to inhibit leukocyte chemotaxis and phagocytosis.


What are the 3 stages of Pertussis?

- Stage 1 (Catarrhal stage)= cold like symptoms for 1-2 wks (so hard to diagnose at this stage). Very contagious here and best time to culture.
- Stage 2 (Paroxysmal stage)= whooping coughing fits for 1-6 wks.
- Stage 3 (Convalescent stage)= recovery stage.


How do you diagnose pertussis?

- nasopharyngeal aspirate or posterior nasopharyngeal swab (oropharyngeal swabs aren't helpful bc you need CILIATED epithelial cells).
- culture but takes over a week.


What type of vaccine is used for pertussis?

acellular vaccine= inactivated pertussis TOXIN (one or more bacterial adhesins) given in combination with tetanus and diphtheria vaccine (5 doses of DTaP for kids or 1 dose of Tdap for adults or pregnant women).
*Immunity wanes over time.


*** What is important to remember about Corynebacterium diphtheriae? (sketchy)

- gram positive rob (V or L-shaped formations)
- A-exotoxin= expressed by a lysogenic bacteriophageand inhibits elongation factor 2 to shut down protein synthesis.
- B-exotoxin= binds heparin-binding epidermal growth factor.
*DTaP/Tdap vaccines protect against A-B exotoxins.
- Human pathogen
- causes DIPTHERIA= fever and exudative pharyngitis with a pseudomembrane (bacteria, debris, fibrin, WBCs) that is very adherent and trying to rid this tends to cause bleeding. Lymphadenopathy (bull neck appearance).


How do you diagnose diptheria?

- special media containing tellurite which forms gray-black colonies.
- Elek test= neutralization test for the exotoxin (most important)
- PCR for tox gene.


What is important to remember about enterobacteriacea?

- gram-negative bacteria associated with RTI and includes Klebsiella, Serratia, Proteus, Enterobacter...
- antibiotic resistance can be a problem.


*** What is Klebsiella pneumoniae? (sketchy)

- gram-negative lactose fermenter (only other enterobacteriaceae that ferments lactose is E. coli) with a very THICK MUCOID ANTI-PHAGOCYTIC CAPSULE.
- usually seen in pts with COPD, diabetes or alcoholism.
- produces "current jelly sputum"


*** What is Pseudomonas aeruginosa? (sketchy)

- aerobic, non-fermenting bactiera
- ubiquitous in the environment (soil and moist environments like sinks, respiratory equipment...).
- resistant to multiple antibiotics
- sweet grape-like odor
- pigmented blue-green
- polysaccharide capsule (CF isolates).
- associated with CF pts, otitis externa (swimmers ear), burns, UTIs, and eye infections.


What is Burkholderia cepacia?

- originally classified as Pseudomonas cepacia and likes moist environments and resistant to antibiotics.
- affects CF pts also.


*** What is Nocardia? (sketchy)

- gram positive cell wall
- filamentous bacteria
- causes bronchopneumonia (necrosis and abscess formation in immunocompromised pts) and often disseminates to the CNS causing brain abscesses.
- Nocardia asteroides complex is main culprit.