Respiratory Pathogens Overview Flashcards
What is the most common source of illness?
Respiratory infections, which are common and serious
What are the 4 mechanical defenses against respiratory tract infections?
- Saliva containse lysozyme that flushes away microbes
- Mucociliary system traps microbes in the nasopharynx
- Mucociliary escalator of the lungs traps and pushes microbes up toward the larynx
- Microbe binding properties are important
What are the normal flora of the upper respiratory tract? (7)
URT is colonized by a number of normal floral organisms:
- Oral streptococci
- Corynebacteria
- Bacteriodes
- Anaerobic cocci
- Candida albicans
- Streptococcus mutans
- Haemophilus influenzae
What the normal flora of the lower respiratory tract?
Trick question, LRT is typically STERILE
What is another name for ear infections?
otitis media
Acute otitis media and sinusitis (OM and S) are most common in who?
Infants and young children, with 80% having experienced at least one by age 3.
More than 50% of OM and S infections are caused by what type of pathogen? Especially what specific type?
More than 50% of the infections are viral, especially respiratory syncytial virus (RSV)
What are the most common bacterial sources of OM and S?
Strep pnemoniae and Haemophilus influenzae
How are OM and S treated?
B/c of increasing antibiotic resistance, treatment leans towards symptomatic in many parts of the world, but antibiotics are often prescribed in the US before a bacterial agent is suspected.
80% of URT infections are caused by what? What do these commonly result in?
80% of URTI’s are caused by viruses. In these infections, it is common to see VESICLES or ULCERATED LESIONS
Bacterial URT infections lead to what?
inflammatory exudates and hemorrhages
What type of microbe almost exclusively causes rhinitis?
Rhinitis is almost exclusively viral. Bacteria rarely cause colds.
What are the most common specific causes of rhinitis?
1&2)Rhinoviruses (more than 100 serotypes) and Coronaviruses cause more than 50% of common colds. Other viruses causing rhinitis include:
3) Adenovirus
4) Parainfluenza virus (paraflu)
5) Influenza virus (flu)
6) RSV
About 70% of Pharyngitis (sore throat) cases are caused by what?
viruses
What types of viruses cause pharyngitis (sore throats)?
Most common 5 are:
Adenovirus, Rhinovirus, Coronavirus, Paraflu, Flu
Other viral causes:
1. Herpesviruses (HSV) 2. Coxsackie A virus
3. EBV
What is the major bacterial agent that causes pharyngitis? Other bacterial causes?
Group A Strep (Strep pyogenes) is the major one.
Others include Nisseria gonorrhoeae, Corynebacterium diptheriae
Diptheria is characterized by what?
A severe sore throat and fever sometimes accompanied by a pseudomembrane composed of necrotic tissue, immune cells, and bacteria.
Diptheria can be life-threatening by causing what?
by causing respiratory obstruction
If the toxin of C. diptheriae reaches the blood stream, it can cause what?
Acute myocarditis
How is diagnosis of pharyngitis done? What is the purpose of this diagnosis?
Throat swabs for culture; the purpose of diagnosis is to determine if the causal agent is bacterial. (identification is usually not made for viral infections, except for unusually severe cases, b/c virus-specific therapy is rare)
In Dx of pharyngitis, special culture media is needed for what bacteria? What else is important to take into consideration?
C diptheriae and N gonorrhoeae;
It is important to recognize that some bacteria ( S pneumo, S aureus, H influenzae) may be colonizers and not the cause of pharyngitis.
Laryngitis and its more severe form, Croup, are more than 90% of the time caused by what? Which ones specfically?
Viruses; mostly Paraflu, flu, adenovirus, and sometimes RSV
What are 3 bacterial agents that can cause laryngitis?
- GAS
- H flu
- S aureus
Bronchitis is characterized by what signs/symptoms? (3)
mild fever, productive cough, and fatigue
What causes 80% of bronchitis? Which ones specifically?
Viruses, with Paraflu, flu, adenovirus, RSV (and measles) leading the way
What are bacterial causes of bronchitis? (4)
- Most importanty: Bordetella pertussis
- H influenzae
- Mycoplasma pneumoniae
- Chlamydia pneumoniae
What does Bordetella percussis cause? In Who? What is that? Has its prevalence increased or decreased recently? Why?
BP leads to whooping cough, which is an acute bronchitis in infants and young children.
There has been a recent increase in whooping cough incidence due to reduced vaccination rates.
In bronchitis, what is used to Dx pertussis and viral infections? What is used to Dx C pneumoniae and M pneumoniae?
Throat cultures are used to Dx pertussis and viral infections, while serology is required for M pneumoniae and C pneumoniae
Signs and symptoms of pneumonia? (6)
chills, high fever, productive cough (sputum production), chest pain, sweating, respiratory distress
What are the 3 routes by which a person can acquire pneumonia?
- inhalation
- aspiration
- blood-borne
The etiology of acute pneumonia is very _______? What does this mean specifically?
Age specific; 80% of pneumonias in infants and young children are viral, but only 10-20% of adult pneumonias are viral.
What are common viral causes of acute pneumonia? (7)
Flu, paraflu, adenovirus, RSV (infants and elderly), SARS-CoV, MERS, metapneumovirus
RSV causes pneumonia in what type of people?
infants and elderly
What type of viral infection, in particular, can produce life-threatening acute pneumonia, even in healthy young adults? It makes them prone to what?
Influenza infection; it can make patients prone to subsequent bacterial acute pneumonia
What is the most common bacterial cause of acute pneumonia? Other bacterial causes include?
Most common: Strep pneumoniae (pneumococcus)
Others: S aureus, H influenze, anaerobes (aspiration)
What are fungal sources of acute pneumonia?
Candida and Aspergillis spp
What is atypical pneumonia?
When the course of presentation differs from that typical of pneumococcal pneumonia and from which a microbe that is not S pneumo is cultured
What are causes of pneumonia in compromised patients?
a) Ps, aeruginosa, anaerobes, Klebsiella pneumoniae
b) Candida, Aspergillis, Pneumocystis
Chronic pneumonia is rarely caused by what?
rarely caused by viruses
What is a typical bacterial cause of chronic pneumonia?
Tuberculosis
What fungal pathogens are common sources of chronic pneumonia?
Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides immitis
Diagnosis of pneumonia is often dependent on what?
microscopic examination and culture of sputum, but quality of sputum is essential (lots of PMNs good, lots of epithelial cells bad)
How does mycobacterium tuberculosis cause chronic pneumonia?
Primary TB is often asymptomatic. It is the reactivated form that leads to chronic pneumonia
Chronic pneumonia due to TB is characterized by what?
fever, malaise, night sweats, weight loss, and bloody sputum
Reactivation of TB occurs how often and is most common in who?
Reactivation occurs in about 10% of cases and is seen more often in men over 50
Reactivation of TB follows what? What brings this on?
Reactivation follows immunosuppression brought on by alcoholism, malnutrition, diabetes, or old age.
What does untreated TB lead to?
Untreated TB will disseminate and ultimately lead to fatal meningitis (consumption)
