Chapter 13 Flashcards Preview

Mechanisms of Microbial Disease > Chapter 13 > Flashcards

Flashcards in Chapter 13 Deck (73):

What are the parts of the lower respiratory tract?

Trachea, bronchi, bronchioles


What causes laryngitis and tracheitis?

Growth A Streptococcus (GAS), H. influenzae, parainfluenza virus, RSV, influenza, adenovirus


What is the clinical presentation of laryngitis and tracheitis in adults and children?

In adults, hoarseness and burning pain, dry cough
In children the airway is narrow and easily obstructed so hospitalization is required


What causes diphtheria?

The lysogenized strain of corynebacterium diptheria, carrying the viral genome which encodes for a toxin


How can we find if someone will get sick from corynebacterium diptheria?

Presence of the bacterium doesn't necessarily mean you will get sick. Must look for the gene by using PCR or ELISA for the toxin


How does the lysogenized strain of corynebacterium diptheria work?

The toxin produced by the viral genome causes arrest of protein synthesis in cells, causing them to die and build up in a mass (not extracellular, don't remove)


What are the clinical manifestations of diphtheria?

Common in developing world.
Necrotic false membrane, dark and malodorous
Life threatening


What are the complications of diphtheria?

Polyneuritis (paralysis of soft palate and regurgitation of liquids)


How is diphtheria treated?

Immediately after diagnosis use the antitoxin from horse serum (do horse hypersensitivity test) and antibiotics
May also need a tracheotomy to assist breathing


What is the vaccine available for diphtheria prevention?

A vaccine in combination with pertussis, tetanus, polio and Haemophilus influenzae B


What is pertussis (whooping cough) caused by?

Bordetella pertussis and parapertussis
B. bronchiseptica


How are pathogens successful in causing pertussis?

Can attach to and multiply in the ciliated respiratory mucosa, produces a variety of toxins


Who does pertussis most affect?

Infants and young children, highly transmissible


What are the clinical manifestations of pertussis?

3 stages
Catarrhal: Mild cold, runny nose, mild cough lasting for several weeks
Paroxysmal: Severe uncontrollable bursts of coughing (15-25 fits/24 hours with vomiting and whooping)
Convalescent: Slow decrease in symptoms 4 weeks after infection


What are the 3 toxins produced in pertussis?

Pertussis toxin: AB type, A subunit affects signal transduction by messing with ADP-ribosyl transferase
Adenylate cyclase: Enters neutrophils, increases cAMP, inhibiting abilities
Tracheal toxin: Kills tracheal cells


What are the complications of pertussis?

Pneumonia (secondary infection), alveolar rupture, seizures


What is the vaccination for pertussis prevention?

Used to be triple protein vaccine but became ineffective due to mutations in protein
Now, acellular vaccines containing the pertussis toxoid and bacterial components (filamentous haemagglutinin and fimbrae)


What causes acute bronchitis?

Often viral: rhinovirus, coronavirus, influenza virus, adenovirus
Bacteria: B. pertussis, B. parapertussis, Mycoplasma pneumoniae, Chlamydophila pneumoniae


What are the clinical manifestations of acute bronchitis?

Peaks in winter
Cough, fever and variable amounts of purulent sputum


How does a pathogen cause acute bronchitis?

Usually following an upper respiratory tract infection, spread and damage the respiratory epithelial cells by the same (usually viral) pathogens


What are the complications of acute bronchitis?

Secondary bacterial infections
Persistant bronchitis (increased sputum volume and purulence instead of resolution)
Pneumonia (from community acquired pathogens, S. pneumonia, H. influenzae)


What are the long term complications of acute bronchitis?

Kids who get bronchitis are more prone to asthma and vice versa


What does respiratory syncytial virus (RSV) cause?

Primary cause of bronchiolitis and pneumonia in infants


How is RSV transmitted?

Via airborne droplets that are inhaled


What are the symptoms of a RSV infection?

Cough, fast respiratory rate and cyanosis


What causes Hantavirus Pulmonary Syndroms (HPS)? Where is it found?

New World hantavirus or Sin Nombre virus (SNV) found in deer mouse


How is SNV transmitted?

Inhalation of SNV-infected rodent feces, saliva or urine


What are the clinical manifestations of HPS?

Flu-like symptoms then viral invasion of the pulmonary capillary endothelium increases vascular permeability and causes fluid to pour into the lungs
~35% mortality rate


What does old world hantavirus cause?

Hemorrhagic fever and renal syndrome


Who is at high risk for pneumonia?

Elderly due to immunocompromisation and innate defences not working as well


What is pneumonia?

Inflammation of the lower respiratory tract
A secondary bacterial infection
Chest pain, cough possibly with sputum, shortness of breath


What are the routes that a pathogen can gain access to the lungs to cause infection?

Upper airway colonization or infection that extends to the lung
Aspiration of organisms
Inhalation of airborne droplets
Seeding of lung via the blood from a distant site


When is pneumonia considered nosocomial (hospital) acquired?

When the patient has been in the hospital for 3 days.
Tends to be more resistant, more severe


What is lobar pneumonia?

Involvement of a distinct region of the lung, can spread to adjacent alveoli


What is bronchopneumonia?

More diffuse and patchy


What is interstitial pneumonia?

Invasion of the lung interstitium, characteristic of viral infections


What is a lung abscess?

Cavitation and destruction of the lung paryenchyma


What causes bacterial pneumonia?

Pneumococcus (used to be almost all cases, gram + dicocci), H. influenzae
M. pneumoniae, Chlamydiophila psittaci, Coxiella burnetti, Legionella pneumonphilia can cause atypical pneumonia (chronic, minimal sputum)


How is pneumonia diagnosed?

Take sputum sample in the morning before breakfast (no saliva), gram stain for typical pathogens and serology for atypical pathogens


How is pneumonia treated?

Antibiotics but resistance can be a problem


How can pneumonia be prevented?

Pneumococcus capsular (23-valent) vaccine in adults
7-valent vaccine in infants (hypersensitivity)


What are some causes of viral pneumonia?

Influenza A or B, Parainfluzena, Measles, RSV, adenovirus, CMV, VZV
Invade through the respiratory tract or blood


What is the differences between the 3 strains of the influenza virus?

A: Epidemics and pandemics, animal reservoirs (birds)
B: Epidemics, no animals
C: No epidemics, mild respiratory illness


What is the basic structure of the influenza A virus?

Haemagglutinin (H) and neuraminidase (N) are type specific antigens used to characterize different strains of influenza A
Changes based on antigenic shift and drift


How does the nomenclature for influenza virus work?

Influenza type/location/year of isolation/strain type (H3N2)


What is the mixed vessel hypothesis?

New influenza strains emerge because influenza type A infects pigs, horses and other animals
Avian H5N1 and H3N2 mixed with Human H1N1 or H3N2


When are the common influenza outbreaks?

Southern hemisphere: May-Oct
Northern hemisphere: Nov-Apr
Coldest months of year, more time inside, easier to transmit


How is avian flu spread?

By the movement of poultry and products


How does influenza virus enter the body?

In droplets, attaches to sialic acid receptor on the epithelial surface via H-spikes


How does influenza virus infection progress?

1-3 days after attachment to the epithelial surface, cytokines are released, causing fever and chills, muscle aches, runny nose and cough
If not resolved in 7-10 days, could lead to bronchitis or interstitial pneumonia
Susceptible to secondary bacterial infection


Who is at higher risk of secondary bacterial infection due to influenza?

Pregnancy and those >60 years old


How can we prevent influenza infection?

Using an egg grown virus that is purified, formalin inactivated and ether extracted or
Purified H and N antigens make a split vaccine
Exact virus strains are reviewed annually


How can you treat influenza infection?

Neuraminidase inhibitors (zanamivir and oseltamivir)


How is influenza infection diagnosed?

Using PCR


What is severe acute respiratory syndrome associated coronavirus (SARS-CoV)?

Novel coronavirus with single stranded RNA
Fever >38 degrees, cough, shortness of breath/difficulty breathing, chest x-ray
Can cause fatality


How did SARS-CoV come about?

Changes in viral reservoir (genetic mutation allowing animal to human and human to human transmission) and human eating habits
Consumption of exotic animals (bats, civet cats)


What animals were a SARS-CoV-like virus detected in?

Himalayan palm civet cats, chinese ferret badgers, horseshoe bats


How is SARS-CoV transmitted?

Respiratory droplets (stable at room temp for 2 days on surfaces) and fecal (stable at room temp for 4 days)


What is MERS?

A variant of SARS (clonal virus) that is spreading from camels to humans


What is a potential coronavirus?

A coronavirus from a bat has potential to spread between humans. From experiment that mutated virus and injected it in rats.


What is the oldest documented communicable disease?

"disease of poverty"
Infects 1/3 world population (most common in South Africa, from cattle)
Often occurs in those HIV/AIDS postive


What is tuberculosis caused by?

Mycobacterium tuberculosis (acid-fast, disinfectant resistant)


How does tuberculosis progress?

Primary infection in lung is asymptomatic (hides in macrophages) then hypersensitivity reaction to mycobacterium antigens causing granuloma and then dissemination through the blood stream to other parts of the body (miliary TB)


How can we diagnose tuberculosis?

Signs and symptoms (fatugue, chronic productive cough with blood, weakness, fever), chest x-ray and tuberculin test


Why is culturing not suitable to diagnose tuberculosis?

Mycobacterium takes 2 months to grow
Can see if acid-fast to confirm mycobacterium


How does a tuberculin test work?

A standardized amount of PPD is injected intradermally and the results are read 48 hours later
Size >10 mm is a positive
Immunocompromised: sinze >5 mm is a positive


How is tuberculosis treated?

Using 3 drugs in combination for 6-9 months


What is MDR-TB?

Resistant to at least isoniazid and rifampicin


What is XDR-TB?

Resistant to isonizid, rifampicin, fluoroquinolone and at least 1 of 3 injectable 2nd line drugs (capreomycin, kanamycin and amikacin)


What is cystic fibrosis?

Inherited disease of secretory glands
Mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene
Most common lethal inherited disorder in whites


What are some characteristics of cystic fibrosis?

Pancreatic insufficiency, abnormal sweat electrolyte concentrations (salty) and production of very viscid bronchial secretions


What bacteria typically colonize in the lungs of patients with cystic fibrosis?

P. aeruginosa (almost all patients by 30), S. aureus, B. cepacia
Organisms that are not pathogenic contribute to the pathogenicity of another


How does P.aeruginosa act in cystic fibrosis?

Changes to a highly mucoid form to protect itself and makes proteases that inactivates or "cleans" antibodies. Bacteria is protected but macrophages are still producing antimicrobial compounds which damage the lungs