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Clinical Microbiology > Respiratory Tract Infections > Flashcards

Respiratory Tract Infections Flashcards

1
Q

2 Lower tract bacterial infections

A

Pneumonia (community or hospital acquired)

Acute exacerbations of chronic bronchitis COPD

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2
Q

3 Upper tract infections

A

Sinusitis
Otitis media
Pharyngitis

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3
Q

Examples of RTI specimens

A

Sputum
BAL/bronchial washing (with bronchoscope)
Nasopharyngeal aspirates/swabs
Endotracheal aspirates
Sinus aspirates (have to punch through bone)
Tympanocentesis (needle through eardrum and aspirate)
Throat swabs

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4
Q

When grading sputum, what do you want to see?

A

HIGH numbers of neutrophils, LOW numbers of epithelial cells

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5
Q

3 common resp tract pathogens

A

Strep pneumoniae (vast majority)
Haemophilus influenzae
Moraxella catarrhalis

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6
Q

3 Atypical pathogens

A

Mycoplasma pneumoniae
Chlamydophyla pneumoniae
Legionella pneumonphila

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7
Q

Empirically you need to make sure to cover…

A

Strep pneumoniae

The atypical pathogens

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8
Q

Pneumonia

A

An inflammatory condition of the lung primarily affecting the alveoli
Severity of disease and mortality vary considerably
Community, hospital, or ventilator acquired

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9
Q

Typical signs and symptoms of pneumonia

A

Fever
Cough (productive or dry)
Chest pain
Shortness of breath

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10
Q

S. pneumoniae

A

Most common bacterial cause of RTIs
Small gram positive diplococci
Alpha hemolytic, bile soluble, optochin S***
Growth enhanced by CO2
Most are encapsulated
Colonizes the nasopharynx in 5-10% of adults and 20-40% of children (cannot take throat swabs)
Incidence increases in winter months

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11
Q

6 factors that cause a disposition to pneumococcal infection

A
  1. Defective Ab formation
  2. Insufficient numbers of PMNs
  3. Living in close quarters
  4. Chronic resp disease
  5. Infancy and aging
  6. Diabetes, alcoholism, liver disease
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12
Q

How do you diagnose otitis media?

A

Look in the ear and see it is red
HAVE to blow air through the otoscope and see how much the eardrum moves
Red ear does not mean otitis

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13
Q

S. pneumoniae virulence factors (3)

A

Capsule (most important - aids in adherence and escape from phagocytic cells)
Pneumolysin (hemolysin - destroys ciliated epithelial cells, activates complement, suppresses oxidative burst by phagocytic cells
Secretory IgA protease

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14
Q

2 vaccines for pneumonia

A
  1. Pneumococcal vaccine - Pneumovax (directed against 23 most common capsular serotypes that cause invasive disease (get into the blood) - but carbohydrate based so no lasting immunity, not very immunogenic, and doesnt work against kids)
  2. Prevnar (conjugate vaccine - to diptheria toxoid)
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15
Q

Drug treatment for S. pneumoniae

A 
Penicillins (cannot use empirically though - too much resistance)
Cephalosporins
Macrolides
Fluoroquinolones
Vancomycin
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16
Q

COPD

A

Chronic obstructive pulmonary disease
An umbrella term used to describe progressive lung diseases (emphysema, chronic bronchitis, refractory asthma, some forms of bronchiectasis)
Characterized by increasing breathlessness

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17
Q

Haemophilus influenzae

A 
Most common cause of AE-COPD
Small gram negative bacilli
Requires X and V factors
Will grow on chocolate agar
May be encapsulated
Type B caused major invasive disease - epiglottitis
Satelliting growth on SBA with S. aureus
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18
Q

Porphyrin Test

A

Determines and isolates X factor requirement
Heavy suspension in amino-levulinic acid, incubate 4 hours, illuminate with UV light and examine for red fluorescence
Positive = X factor independent

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19
Q

H. influenzae Treatment

A

Approx 18% produce beta lactamase and 1% have altered PBP
2nd/3rd gen cephalosporins
Newer macrolides ok
Fluoroquinolines good, but not in children
Amoxicillin-clavulanate very effective

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20
Q

Which two drugs can you NOT use to treat H. influenzae?

A

Septra

Penicillin

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21
Q

Moraxella catarrhalis

size, gram stain, shape, associated with what diseases, carriage rate, resistant to, susceptible to

A

Small gram negative cocco-bacilli
Associated with otitis media, sinusitis, AECB
Carriage rate about 50%
DNase+, asacchrolytic
90% strains resistant to amp/amoxi and Septra
Susceptible to most oral antibiotics

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22
Q 
Legionella pneumophila
(gram stain, shape, intra/extracellular, where is it found in environment, illness, media, staining, requires what for growth)
A 
Gram negative bacilli
Intracellular pathogen
Widespread in environment (soil, water, taps, showers)
Widespread spectrum of illness
Requires special media to grow - BCYE agar
Faintly stains, easy to miss
Asaccharolytic
Requires L-cysteine for growth!
Stimulated by 5% CO2
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23
Q

Why do you have to put charcoal or blood in the media with Legionella?

A

Because you need them to mop up the toxins so they will grow!

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24
Q

2 ways to get a Legionella diagnosis in the lab?

A

Urinary antigen test
Culture
NOT DFA testing or serology

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25
Q

2 drugs used to treat Legionella

A

Fluoroquinolones

Macrolides

26
Q

Mycoplasma morphology and physiology

A 
Lack a cell wall!!
Smallest free living bacteria
Small genome
Require complex media to grow
Facultative anaerobes except M pneumonia (strict aerobe)
27
Q

2 diseases M. pneumoniae causes

A
  1. Tracheobronchitis (70-80% of infections, post infectious cough)
  2. Pneumonia (20-30% of infections, mild disease but long duration, most common cause of atypical pneumonia)
28
Q

3 drugs the atypicals are susceptible to (myco and chlamydophyla)

A
  1. Doxycycline
  2. Macrolides
  3. Fluoroquinolones
    Not susceptible to cell wall active agents
29
Q

Bordetella pertussis

A 
Causes pertussis
Small gram negative cocci-bacilli
Strictly aerobic, fastidious
Requires growth on media containing charcoal, blood or starch
BG or RL media
30
Q

3 stages of pertussis

A
  1. Catarrhal stage (1-2 weeks, non specific upper tract infection - sneezing, runny nose mild cough, low grade fever, very contagious)
  2. Paroxysmal stage (1-6 weeks, paroxysmal cough, inspiratory whoops, vomitting, cyanosis, exhaustion, leukocytosis, lymphocytosis)
  3. Convalescent stage (2-3 weeks, gradually resolves, may return if patients acquire secondary infection)
31
Q

Incubation period of pertussis

A

7-10 days

Range 4-21

32
Q

Specimen and drug for pertussis

A

Naso-pharyngeal specimens

Treat with Macrolides

33
Q

Strep pyogenes

A

Gram positive, catalase positive, beta-haemolytic, group A, PYR +, Taxo A (bacitracin) S
Complications: rheumatic heart disease, post-streptococcal glomerulonephritis

34
Q

2 drugs to treat S pyogenes

A

Penicillin

Amoxicillin

35
Q

2 reasons to treat bacterial pharyngitis

A
  1. Eradication

2. Prevents complications (antibodies can prevent or minimize risks, wait for culture results)

36
Q

2 main ways viral RTIs are transmitted

A

Droplet (not aerosol)

Contact (inoculate nose/eyes)

37
Q

Factors contributing to severity of viral diseases (4)

A

Inoculum size
Virulence traits
Immune system (compromised or not)
Co-morbidities

38
Q

Most common virus causing RTIs

A

Rhinovirus

Coronavirus is second

39
Q

2 ways to collect viral specimens

A

Nasopharyngeal swab or aspirates for URTIs (swab has to be transported in a special media, use flocked swab, throat swab isn’t as good as NP swabs)
Bronchial alveolar lavages for LRTIs (transport in sterile container)

40
Q

Best way to detect respiratory viruses

A

Molecular methods (high sensitivity and specificity! Can use qualitative real-time multiplex RT-PCR for FluA/B/RSV)

41
Q

Rhinovirus

family, nucleic acid/sense, enveloped or not, diseases

A 
Picronaviridae family
ssRNA (+)
Non-enveloped
>100 serotypes (no vaccine)
Most common viral RTI
42
Q

Coronavirus

family, nucleic acid/sense, enveloped or not, diseases

A 
Coronaviridae family
ssRNA (+)
Enveloped
Cause of common cold (second to rhino)
Some have caused more severe disease (SARS)
43
Q

Enterovirus

family, nucleic acid/sense, enveloped or not, diseases

A 
Picronaviridae family
ssRNA (+)
Non-enveloped
12 species, over 100 serotypes
Affect millions worldwide each year
Usually mild respiratory illness
Certain ones have been linked to polio like illnesses with paralysis (EV - D68)
44
Q

Respiratory syncytial virus

family, nucleic acid/sense, enveloped or not, diseases

A

Paramyxoviridae family
ssRNA (-)
Enveloped
RSV A and RSV B
Most common cause of bronchiolitis in children
Spreads rapidly in households and daycares
Can affect adults (do not have lasting immunity)
Severe infections may be fatal (co-morbidities: heart and lung disease, treat with passive immunization palivizumab)

45
Q

3 groups of people most at risk for respiratory disease

A

Children
Elderly
Immunocompromised

46
Q

Parainfluenza viruses

family, nucleic acid, enveloped?, causes

A 
Paramyxoviridae family
ssRNA (-)
Enveloped
4 types
Common cause of URTIs in children
2% get croup (laryngotracheobronchitis - barking cough - inflammation of upper airways and narrowing of subglotic region)
47
Q

Adenovirus

genome, enveloped?, causes, types

A 
dsDNA
Non-enveloped
Over 60 types have been identified
URTIs or LRTIs
Types 40 and 41 are GI viruses (cause diarrhea)
48
Q

Influenza

family, nucleic acid, enveloped?, types

A

Orthomyxoviridae
ssRNA (-)
Enveloped
Segmented genome
3 types (A, B, C)
FluA and B cause seasonal epidemics each year
FluA is most important (pandemic potential, more severe disease)
Subtyping based on hemagglutinin and neuraminidase

49
Q

Common symptoms for influenza

A 
Cough
Fever
Malaise
Fatigue, weakness
Severe muscle pain
50
Q

2 classes of antiviral treatment for influenza

A 
Amantidine (M2 inhibitor)
Neuraminidase inhibitors (oseltamivir and zanamivir)
51
Q

Function of:
Hemagluttinin
Neuraminidase

A

Hemagluttinin: binds to sialic acid to allow viral entry to the cell
Neuraminidase: cleaves the HA binding to sialic acid to release viral particle

52
Q

Amantidine Resistance

A

Mutations in amino acids in the M2 channels
All H3N2 human strains are resistant
Doesn’t work against influenza B (no M2 channels)
No longer used

53
Q

Neuraminidase inhibitors

A

Mutations in NA or HA

Most circulating strains are susceptible

54
Q

Influenza vaccine

A

Trivalent or quadravalent vaccine
Needs to be updated every year
Protection good when matched to circulating viruses, but antigenic drift occurs

55
Q

Antigenic drift

A

Due to mutation over time in surface glycoproteins (HA and NA)
Occurs in both FluA and B
May lead to a vaccine mismatch or lack of immunity

56
Q

Antigenic shift

A

Genetic reassortments between avian/swine/human
Only occurs in FluA
Emergence of pandemics
No pre-existing immunity

57
Q

Influenza

  1. Natural reservoir
  2. Mixing vessel
A
  1. Aquatic birds

2. Pigs

58
Q

Avian Influenza A (H5N1)

A

Transmission by direct contact with infected poultry or objects contaminated by their feces
Exposure is most likely during slaughter and cooking prep
Doesn’t usually spread person to person very readily - not adapted to humans

59
Q

H1N1 versus H5N1

A

H1N1: Easily spread, rarely fatal
H5N1: Spreads slowly, often fatal

60
Q

Arcanobacterium hemolyticum

causes what with what symptoms, hemolytic, treat with, grows best with

A

Causes pharyngitis in teen and young adults (16-24)
Rash (like scarlet fever), RHD or AGN
Invasive disease occurs, but rare
May respond poorly to penicillin, but disease is self limiting
Grows best in CO2 for 48 hours
Weakly beta hemolytic (best on rabbit blood)
Anaerobically: slower growth
Penicillin + gentamicin or clindamycin used

61
Q

Factors (out of X, V, and Catalase) needed for H influenzae, H parainfluenzae, and Aggregatibacter aphrophilus

A

H influenzae: X, V, and catalase +
H parainfluenzae: V +, catalase +/-
A. aphrophilus: negative for all

Clinical Microbiology (25 decks)

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