Microbiology Flashcards
Give 3 symptoms of influenza
- General malaise
- Myalgia Headache
- Dry cough
- Prostration - extreme fatigue and weakness
- Fever
What are potential causes of classical flu?
- Influenza type A or B viruses
- Influenza type C virus can also cause a form of influenza yet it is less common
How is flu spread?
- Droplets/formites
- Direct contact with respiratory secretions from an infected individual
How can influenza be treated?
Treatment can be:
- Symptomatic - bed rest, maintain fluids etc.
- Curative - antivirals such as oseltamivir and zanamivir
What allows influenza to cause frequent epidemics?
Antigenic drift - minor surface protein changes (usually)
Pandemics are potentially very dangerous when involving influenza - why?
Influenza A viruses only are involved. Antigenic shift occurs in a animal reservoir or mixing vessel This means a “hybrid” virus can be formed that humans will have little if no immunity to
Which laboratory techniques can be used to determine the presence of the flu virus?
- PCR - using nasopharyngeal swabs, throat swabs or other respiratory samples
- Immunofluorescence for antigen detection
- Viral cultures
- Antibody detection
Influenza is prevented though vaccines, what is a “killed vaccine”?
The virus is grown in culture, inactivated and combined with an adjuvant - a substance to enhance immune reaction. This can be given annually to patients at risk of contraction, healthcare workers, the very young/old
Influenza is prevented though vaccines, what is an attenuated vaccine”?
This is a more effective vaccine vs a killed vaccine The real pathogen is used, but with reduced virulence. This vaccine is given to all children aged between 2 and 5
What is the most common cause of community acquired pneumonia?
Streptococcus pneumoniae
What are the three causes of atypical pneumonia?
- Mycoplasma pneumonia
- Legionella pneumonia
- Chlamydophilia pneumoniae
Coxiella burnetii is associated with which two main conditions?
- Q fever
- Pneumonia
A complication, involving Q fever and the heart is likely to be what?
Infective endocarditis
(caused by Coxiella burnetii)
Chlamydophila psittaci causes which condition?
Psittacosis
This is an uncommon sporadic zoonosis (pet birds) and will normally present as pneumonia
What is a sporadic zoonosis?
An infectious disease from animals that can spready to humans
What is bronchiolitis?
A common lower respiratory tract infection causing inflammation of the bronchioles
It normally affects people in the first or second year of life
Grunting will occur - difficulty in breathing, reduced partial pressure of oxygen and sternal indrawing
What is most likely to cause bronchiolitis?
Respiratory synctial virus (RSV)
What is metapneumovirus?
The second most common cause (after RSV) of lower respiratory infection in young children
The virus has highest incidence in winter
How is metapneumovirus diagnosed?
Throat swabs and PCR
What is chlamydia trachomatis?
An STI caused by bacteria
The bacteria can present in one of three ways:
- Genitourinary
- Pulmonary
- Ocular
It can cause pneumonia in infants
Diagnosed by PCR on urine of mother, or pernasal/throat swabs of child
Coxiella burnetii is a becteria mostly spread from what to humans?
Animals such as sheep or goats
When was metapneumovirus discovered?
2001
Name an alpha-haemolytic streptocooci that can cause respiratory tract infection
Strep pnemoniae
Name a beta haemolytic streptococci that can cause respiratory tract infection
Strep pyogenes
Name two key gram negative bacteria that can cause respiratory tract infection
- Haemophilus influenzae
- Moraxella catharalis
What pathogen will cause acute epiglottitis?
Haemophilus influenza type B
What is used to test for the presence of haemophilus influenzae in epiglottitis?
Blood cultures
(not throat swabs)
What is the treatment for epiglottitis?
Ceftriaxone
Haemophilus influenzae will only grow on what?
Lysed blood agar
Exacerabtions of COPD can be caused by which pathogens?
- Haemophilus influenzae
- Moraxella catarrhalis
- Streptococcus pneumoniae
- Gram negatives
What is Moraxella catarrhalis?
A gram-negative coccus bacteria commonly found in respiratory tract infection
How can the cause of a COPD exacerbation be tested for?
- Sputum culture
- Sputum purulence
- CXR
When will a COPD exacerbation be treated for infection?
- When sputum is purulent
- When CXR changes
- In the presence of pneumonia
What is the first line treatment for infection during a COPD exacerbation?
Amoxicillin (500mg) for 5 days
(aims to treat H.influenzae, M.catarrhalis, S.pneumoniae)
What is the second line treatment for infection during a COPD exacerbation?
Doxycycline 200mg on day 1 which drops down to 100mg between days 2 and 5
By what other name is acute laryngotracheobronchitis known?
Croup
Croup is characterised mainly by what?
Harsh cough and stridor
How is croup treated?
Steroids
Humidification
Coryza can be caused by which pathogens?
Rhinovirus - mainly
Coronavirus
What is cystic fibrosis?
An inherited disease causing abnormally thick mucous blocking many tubular structures in the body (mostly lungs and digestive system)
This will lead to repeated chest infections and chronic infection because microbes become trapped
What will often precede an episode of acute bronchitis?
UTI
(whooping cough can cause the condition)
What is the clinical presentation of acute bronchitis?
- Infection an inflammation of bronchi
- Productive cough
- Wheeze
- Fever
- Normal CXR
What causes whooping cough?
Bordetella pertussis
How does whooping cough present clinically?
- Acute tracheobronchitis
- Cold-like symptoms
- Paroxysmal coughing (sudden recurrence/worsening)
- Repeated violent exhalations
- Potentially vomiting
How is Bordetella pertussis diagnosed?
- Bacterial culture - pernasal swabbing and charcoal-blood agar
- PCR - pernasal swab
- Serology
How does the treatment of whooping cough vary based on age?
- Age <1 - clarithromycin
- Age>1 - clarithromycin and azithromycin
- Pregnancy - erythromycin
Community acquired pneumonia is caused most frequently bvy which pathogen?
Step pneumoniae
How is pneumonia diagnosed?
- Culturing sputum
- Undergoing viral PCR
How is pneumonia treated?
Amoxicillin (5 days)
or
Co-amoxiclav and doxycycline (100mg)
Very severe:
Co-amoxiclav and IV clarithromycin
How is pneumonia tested for?
Bloods
- Erythrocyte sedimentation rate
- C-reactive protein
- Cultures
Sputum
- Microscopy
- Culture
- Cytology
CXR and potentially CT
Legionella pneumonia is known by which other name?
Legionnaire’s disease
Legionella pneumonia is a form of _________ pneumonia
Atypical
Where does the pathogen legionella pneumonia normally reside and how is it acquired?
Resides in water (stagnant) with water amoeba which provide nutrients and protection
Often acquired by coming into contact with this water (inhalation) or from direct person to person contact
Often acquired on holiday abroad
What are some risk factors for Legionella pneumonia?
- Coming into contact with contaminated water
- Impaired immunity
- Altered immunity
- Diabetes
- Smoking
- Having a malignancy
What is the treatment for legionella pneumonia?
Clarithromycin and erythromycin
or
Quinolones such as levofloxacin
What are the commonest causes for hospital acquired pneumonia?
Gram negative bacteri such as:
- Klebsiella spp
- Pseudomonas spp
- E.coli
Clostridia (gram postive bacteria)
Staph aureus
What is pneumocystis pneumonia and what causes it?
Pneumocystis jirovecii
What is pneumocystis jirovecii and how is it acquired?
A fugus acquired through inhalation of spores
(usually only affected severly immonocompromised - HIV etc)
How does pneumcystis jirovecii present clinically?
- Dry cough
- Fever
- Breathlessness
- Fatigue
How is pneumcystis jirovecii diagnosed?
- Bronchoalveolar lavage
- Sputum sample or gargle
- Immunofluorescence (antibody techniques)
What can used as treatment for pneumcystis jirovecii?
Co-trimoxazole and prophylaxis
What is aspergillus?
Aspergillus fumigatus is a fungus that can cause severe pneumonia and invasive disease when inhaled in immunocompromised individuals
In normal patients localised pulmonary infection and potentially a aspergilloma (fungus ball) will develop
How can aspergillus be diagnosed?
Bronchoalveolar lavage to obtain specimens for fungal culture and PCR
(tissue can also be examined)
How is aspergillus fumigatus treated?
Amphotericin B
Voriconazole
Surgery
Tb is detected by which methods?
- Culturing (most sensitive)
- PCR
- Ziehl-Neelsen stain (least sensitive)
Describe how a Ziehl-Neelsen stain is performed
- A red dye (carbol fuchsin) is added to a sample of Tb
- The sample is heated slighly to melt the waxy coat of Tb
- Alcohol and acid are then added and in mycobacteria the colour of the dye is still retained
- A blue dye is then added (methylene blue)
- If red dye is still visible under the microscope then Tb is present
What are the pros and cons of a Ziehl-Neelsen stain?
Pros
- Cheap
- Fast
Cons
- Does not distinguish between species
- Gives no information on drug sensitivity
What are the pros and cons of PCR for Tb detection?
Pros
- Inexpensive
- Fast
Cons
- Little information on species
- Little infomation on drug sensitivity
What are the pros and cons of culturing as a detection method for Tb?
Pros
- Highly sensitive and specific
- Allows for information on drug sensitivity
Cons
- Slow
