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Microbiology > Respiratory Tract Infections > Flashcards

Respiratory Tract Infections Flashcards

1
Q

Otitis Externa Etiologies

A

Psuedomonas aeruginosa and Staphylococcus aureus

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2
Q

Pseudomonas aeruginosa description

A

Gram-negative encapsulated bacilli. Produces fluorescent blue/green pigments pyocyanin (virulence factor, produces ROS) and pyoverdin. Infectious isolates have pili.

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3
Q

Staphylococcus aureus description

A

Gram-positive encapsulated cocci in clusters.

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4
Q

Staphylococcus aureus Culture

A

Coagulase positive (gold standard) and Beta-hemolytic

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5
Q

AOM and Sinusitis Etiologies

A

Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis.

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6
Q

Streptococcus pneumoniae Description

A

Gram-positive, lancet-shaped, encapsulated diplococci.

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7
Q

Streptococcus pneumoniae Culture

A

Alpha hemolysis with optochin sensitivity.

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8
Q

Moraxella catarhalis Description

A

Gram-negative diplococci

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9
Q

Moraxella catarhalis Culture

A

Oxidase positive. Beta-lactamase producer.

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10
Q

Diphtheria Etiology

A

Corynebacterium

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11
Q

Corynebacterium Description

A

Gram-positive pleomorphic bacilli. Palisades (V or chinese letters appearance). Metachromatic volutin granules. Green organism with dark stained granules.

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12
Q

Diptheria toxin

A

A-B exotoxin. Stimulated by low iron concentrations. Binds the heparin-binding EGF and is endocytosed. The vesicle becomes acidified and releases the A subunit. The A subunit inactivates EF-2 via ADP- ribosylation and halts protein synthesis.

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13
Q

Cutaneous Diphtheria Presentation

A

Chronic ulcers usually due to non-toxigenic strains.

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14
Q

Respiratory Diphtheria presentation

A

Sudden onset of malaise, exudative pharyngitis, low-grade fever and LAD (“bull neck”). Forms a pseudomembrane in the pharynx made of fibrin, bacteria, WBC and necrotic epithelial cells. Systemic toxicity can lead to myocarditis and demyelination.

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15
Q

Corynebacterium culture

A

Loeffler’s medium (enhances formation of the volutin granules) and cysteine-tellurite agar (definitive test).

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16
Q

Diphtheria Diagnosis

A

Gram stain (positive with volutin granules), culture, Elek test (immunodiffusion assay of the toxin), PCR, ELISA, immunochromatographic strip assay.

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17
Q

Pertussis Etiology

A

Bordetella pertussis

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18
Q

Bordetella pertussis Description

A

Small, gram-negative coccobacilli

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19
Q

Bordetella pertussis virulence factors

A

endotoxin, adhesins, exotoxins

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20
Q

Bordetella pertussis adhesins

A

Mediate the attachment to integrins to colonize the ciliated respiratory epithelium. Filamentous hemagglutinin, pertactin and agglutinogens.

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21
Q

Bordetella pertussis A-B exotoxin

A

Dysregulates cAMP and inhibits phagocytes. Causes lymphocytosis.

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22
Q

Bordetella pertussis adenylate cyclase toxin

A

Decreases chemotaxis

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23
Q

Bordetella pertussis Dermonecrotic toxin

A

Causes vasoconstriction that can lead to necrosis

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24
Q

Bordetella pertussis tracheal cytotoxin

A

Kills ciliated respiratory cells. Allows infection of the lower respiratory tract.

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25
Q

Pertussis disease stages

A

Catarrhal: inflammaiton of the mucous membranes with nonspecific URI symptoms but is highly contagious. Paroxysmal: attacks/spasms, paroxysmal coughing often followed by vomiting, characteristic “whoop” can last for weeks.
Convalescent: Gradual recovery

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26
Q

Pertussis Complications

A

pneumonia, encephalopathy, seizures and death

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27
Q

Pertussis epidemiology

A

Usually occurs in children less than 1 yo.

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28
Q

Bordetella pertussis Culture

A

Grows on enriched selective medias. Bordet-Gengou agar (definitive) and Regan-Lowe (Gray/silver colonies).

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29
Q

Pertussis Diagnosis

A

Serology for the toxin or adhesins, culture, PCR for the toxin gene.

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30
Q

Acute Respiratory Disease Etiologies

A

Rhinovirus, coronaviruses, Adenoviruses

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31
Q

Rhinovirus Epidemiology

A

Hyperendemic during the winter. Usually occurs in children and you adults. Transmission occurs with direct contact and through aerosols. Immunity is transient.

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32
Q

Rhinovirus Treatment

A

Zinc gluconate (cold eeze) and picovir (inhibits viral binding).

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33
Q

Influenza Serotypes

A

Type A > Type B > Type C. Subtypes are based on envelope proteins, H=hemagglutinin (attachment) and N=neuraminidase (penetration and release).

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34
Q

Influenza Presentation

A

Abrupt onset of fever, aches, chills and cough, that usually lasts a week.

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35
Q

Influenza complications

A

Primary influenza pneumonia, Secondary/bacterial pneumonia (S. pneumoniae, S. aureus, Hib), Reyes syndrome and Guillain-Barre syndrome.

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36
Q

Reyes syndrome

A

Acute, catastrophic systemic disorder. Edematous encephalitis and fatty alteration of liver tissue. Usually seen in kids 6 mo-15 yo. Associated with influenza and the chicken pox that is treated with aspirin.

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37
Q

Guillain-Barre Syndrome

A

Demyelination that can be induced by the vaccination but there is a ten fold higher risk from the natural infection.

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38
Q

Influenza Diagnosis

A

Direct isolation from throat/nasopharyngeal swabs or rapid antigen detecting kits (can give false negatives).

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39
Q

Amantadine/rimantadine

A

Treats influenza type A. Stops uncoating and penetration. Some resistance has emerged.

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40
Q

Ostemivir (tamiflu)/ zanamivir (relenza)

A

Treats influenza type A and type B. Neuraminidase inhibitors that stop the release and spreading. Resistance has emerged.

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41
Q

Influenza vaccine

A

Trivalent contains two type A and one type B virus that is predicted to be most likely. Children less than 9 yo require two administrations for their first time. Can result in mild flu-like symptoms.

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42
Q

Influenza vaccine target groups

A

Adults over 65, long term care facilities, pulmonary/cardiac chronic conditions, asthma, immunosuppressed, DM, renal dysfunction, hemoglobinemias, pediatric patients on aspirin therapy, healthcare workers.

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43
Q

Antigenic Drift

A

Point mutation in the H or N genes that causes minor genetic variation.

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44
Q

Antigenic Shift

A

Exchange of genomic segments. Causes major genetic variation. Occurs more in type A due to it’s segmented genome and wide range of hosts.

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45
Q

Influenza Nomenclature

A

type/location of discovery/year of isolation/isolation number/antigenic type

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46
Q

Chlamydiae

A

Obligate intracellular parasite. Biochemically restricted so has to use host ATP.

47
Q

Chlamydia trachomatis presentation

A

Infant pneumonia (onset at 3 weeks). Rhitis follow by a cough. Transmitted to the neonate by the mother through vaginal delivery. At risk for reiter’s syndrome

48
Q

Chlamydophila pneumonia presentation

A

Can cause bronchitis, pneumonia, sinusitis and is associated with atherosclerosis.

49
Q

Croup presentation

A

Syndrome of fever, hoarseness and a barking cough. Most common in children 6-18 mo. Results from varying degrees of laryngeal obstruction.

50
Q

Croup etiology

A

PIV type 1 > PIV type 2&raquo_space;> RSV

51
Q

Parainfluenza Virus (PIV) Description

A

Nonsegmented, negative sense, ssRNA genome. Virion is enveloped with protein spikes.

52
Q

PIV presentation

A

Harsh cough, rhinitis, sore throat, SOB. 2-3% leads to croup. In adults PIV presents as a nonspecific URI.

53
Q

PIV Complications

A

Otitis media, parotitis.

54
Q

PIV Epidemiology

A

Most common in the fall/winter. Type 1 and type 2 are alternating epidemics in the fall. Type 3 is sporadic in later winter/ early spring. Life long immunity is not observed.

55
Q

PIV Diagnosis

A

Direct fluorescent antibody test or RT-PCR.

56
Q

Respiratory Syncytial Virus (RSV) Presentation

A

Cough, dyspnea, cyanosis and sometimes croup. IgE mediated.

57
Q

RSV Diagnosis

A

Rapid antigen tests or nucleic acid tests

58
Q

RSV Treatment

A

Immune globulin (Palivizumab) also used as prophylaxis. Ribavirin is used only if supportive treatment fails.

59
Q

RSV Epidemiology

A

Annual winter outbreaks. Most common lower respiratory infection in children younger than 4 yo (peak incidence in less that 1 yo).

60
Q

RSV risk factors

A

Prematurity, cardiac/respiratory abnormalities, birth a few months before RSV season.

61
Q

SARS description

A

Severe Acute Respiratory Syndrome. Coronavirus. Emerging new infection that is now considered extinct. Zoonotic.

62
Q

Bacterial Pneumonia Definition

A

Inflammation of the lung parenchyma with the build up of fluid, inflammatory mediators, debri and necrotic tissue that restricts airflow

63
Q

Nosocomial definition

A

Develops 72 hours or more following hospital admission

64
Q

Typical pneumonia etiologies

A

S. pneumoniae, H. influenzae, K. pneumonia, S. aureus.

65
Q

Atypical pneumonia symptoms

A

Gradual fever that is less than 103 degrees, non-productive cough, patchy infiltrates, well appearing, body aches, diarrhea, abdominal pain.

66
Q

Atypical pneumonia etiologies

A

Chlamydiphla pneumoniae, mycoplasm pneumoniae, legionella pneumoniae.

67
Q

Typical pneumonia symptoms

A

Sudden fever that is greater than 103, ill appearing, productive cough, chills, pleurisy, consolidation, chest pain, SOB.

68
Q

Streptococcus pneumoniae epidemiology

A

Cold/wet months. Children and those over 65 yo. Asymptomatic carriers are the main reservoir. There are 25 infectious serotypes.

69
Q

Streptococcus pneumoniae virulence factors

A

Capsule, IgA protease, hydrogen peroxide, pili, adhesins, choline binding protein, peptidoglycan-teichoic acid, pneumolysin (specific to S. pneumoniae), neuraminidase/hyaluronidase, autolysin (specific to S. pnemoniae).

70
Q

Pneumolysin

A

S. pneumoniae virulence factor. Interacts with host cells to form transmembrane pores leading to lysis. Activates complement to increase inflammation. Produced during stress.

71
Q

Autolysin

A

S. pneumoniae virulence factor. Causes the lysis of pneumococcus. Attempt by the organism to dampen the host immune response. Destroys one layer of the biofilm to overwhelm the immune system. Released in response to antibiotic therapy and stationary phase.

72
Q

Clinical presentation of Streptococcus pneumoniae

A

Typical Pneumoia: rust colored sputum. Otitis media, sinusitis, bacteremia, meningitis, arthritis, peritonitis.

73
Q

23-valent pneumococcal vaccine

A

Covers 90% of the serotypes. Recommended in adults older than 65 yo and those with high risk.

74
Q

13-valent pneumococcal vaccine

A

Covers 80% of the serotypes in children younger than 6 yo. Conjugated to a carrier protein. Covers most of the penicillin resistant strains.

75
Q

Streptococcus pneumoniae Diagnosis

A

Gram-positive diplococci. Alpha-hemolytic (green colonies on RBC agar), optochin sensitivity, Bile solubility (only alpha hemolytic that is lysed by bile), agglutination tests for the capsule, genetic probe test.

76
Q

Streptococcus pneumoniae DOC

A

Penicillin G

77
Q

Chlamydophila pneumoniae Description

A

Atypcial pneumonia. Gram negative obligate intracellular parasite. Life cycle exists of elementary bodies (spores/infectious) and reticulate bodies (intracellular).

78
Q

Chlamydophila pneumoniae Pathogenesis

A

Direct tissue destruction and inflammatory response. Posesses 2 exotoxins. Primary response is from PMNs so no long lasting immunity.

79
Q

Chlamydophila pneumoniae Presentation

A

Atypical pneumonia. Can be asymptomatic. Persistent non-productive cough with malaise. Unilateral lower lobe involvement.

80
Q

Chlamydophila pneumoniae epidemiology

A

Humans are the only reservoir. Most common in adults older than 60 yo.

81
Q

Chlamydophila pneumoniae Diagnosis

A

cell culture and microscopy for serology and PCR.

82
Q

Chlamydophila pneumoniae Treatment

A

Tetracycline/erythromycin

83
Q

Haemophilus Influenzae Description

A

Non-motile, gram-negative, coccobacillus. Has lipooligosaccharide (LOS) instead of LPS. Requires RBCs but isn’t capable of lysis. Can be encapsulated or not. Non-typeable H. influenzae is able to lose it’s capsule and is part of normal flora. Type B (Hib) can cause pneumonia in children.

84
Q

Haemophilus Influenzae Virulence factors

A

Polyribosylribitol phosphate (PRP) capsule, neuraminidase, IgA protease, Fimbriae, LOS.

85
Q

Haemophilus Influenzae Pathogenesis

A

Non-typeable causes infection due to imbalance of colonization. Non-encapsulated strains have adhesisns with bind to the epithelium resulting in loss of the cilia and sloughing off of cells (LOS).

86
Q

Haemophilus Influenzae Diagnosis

A

Gram staining (negative), serological testing (capsule), Culture, Latex agglutination test (tests for antigens not viable bacteria).

87
Q

Haemophilus Influenzae Culture

A

Must be cultured on chocolate agar (lysed RBC) with hemin and NAD at 37 degrees celcius with CO2. Or can be grown as a satellite around S. aureus (not diagnostic).

88
Q

Haemophilus Influenzae Treatment

A

Augmentin

89
Q

Klebsiella pneumoniae description

A

non-motile, gram-negative bacillus with a thick/slimy capsule.

90
Q

Klebsiella pneumoniae Epidemiology

A

Found in the normal flora. Causes typical CAP and nosocomial pneumonia. Mainly seen in the immunocomrpomised (alcoholics, DM, homeless).

91
Q

Klebsiella pneumoniae Virulence factors

A

polysaccharide capsule, Adhesins (fimbriae).

92
Q

Klebsiella pneumoniae Presentation

A

Caused by aspiration of normal oropharyngeal microbes. Aggressive necrotizing CAP usually in the upper lobes. Causes the destruction of alveoli. Rapid onset of fever and often fatal. Currant jelly sputum.

93
Q

Klebsiella pneumoniae Diagnosis

A

Gram stain (negative), culture (mucoid capsule), CXR (cavitation).

94
Q

Klebsiella pneumoniae Treatment

A

Empiric therapy with aminoglycoside, third generation cephalsporin and/or a flouroquinolone

95
Q

Mycoplama pneumoniae Description

A

Very small bacteria that lacks a cell wall (doesn’t gram stain). Plasma membrane contains sterols.

96
Q

Mycoplama pneumoniae Culture

A

“fried egg” appearance on many different media.

97
Q

Mycoplama pneumoniae Presentation

A

Atypical CAP. Non-productive cough that lasts 1-2 months, fever, crackles, HA, CP. Can cause otitis, rhinitis, pharyngitis and tracheobronchitis.

98
Q

Mycoplama pneumoniae epidemiology

A

Most common in people 5-20 yo. Relapses are common because it fuses to the hosts cell membrane so there is no long term immunity.

99
Q

Mycoplama pneumoniae Diagnosis

A

CXR (patchy infiltrates), sold aggluntinin assay (detects IgM that binds the I antigen on RBC)

100
Q

Mycoplama pneumoniae treatment

A

azithromycin/tetracycline

101
Q

Legionella pneumoniae description

A

thin, pleomorphic, gram-negative bacillus, fimbriae with a polar flagellum. Produces beta lactamase. Usually caused by serotype 1. Facultative intracellular parasite.

102
Q

Legionella pneumoniae pathogenesis

A

Bacterial cells are inhaled and opsonized with C3b then phagocytized. Survive intracellulary by inhibiting the phagolysosome. Replicates inside the cell then kills the host cell and releases toxic enzymes along with the bacteria. Huge inflammatory response can lead to necrosis.

103
Q

Pontiac fever

A

Legionella pneumoniae. Self-limited illness that lasts 2-5 days and doesn’t require treatment. Fever, chills, malaise, HA.

104
Q

Legionnaire’s Disease

A

Legionella pneumoniae. Severe, acute, atypical CAP. High mortality rate. Fever, chills, non-productive cough, HA, GI, neurological symptoms. Acute fibropurulent necrotizing pneumonia.

105
Q

Legionella pneumoniae Epidemiology

A

Found in nature and moist environments. Inhalation of aerosols from contaminated water (rivers, sewage, showerheads). Capable of replication in protozoans.

106
Q

Legionella pneumoniae Risk factors

A

Large inoculum and a compromise in pulmonary or immune function. Smoking, COPD, elderly, alcoholics.

107
Q

Legionella pneumoniae Diagnosis

A

Culture on a buffered charcoal yeast extract medium (BCYE). Rapid antigen test of the urine (ELISA) for serotype 1.

108
Q

Legionella pneumoniae Treatment

A

Levofloxacin or azithromycin

109
Q

Pseudomonas aeruginosa virulence factors

A

pyocyanin (ROS production), A-B exotoxin (inhibits protein synthesis), Elastases, Alginate (slime layer), glycocalyx, pili, lipopolysaccharide (endotoxin).

110
Q

Pseudomonas aeruginosa Epidemiology

A

Widespread in the environment. used extensively in bioremediation. Carried on skin, fomites and in feces. Opportunistic infections.

111
Q

Pseudomonas aeruginosa Presentations

A

UTI, pneumonia, eyes, ears, skin, burn patient, CF (often the cause of death).

112
Q

Pseudomonas aeruginosa Diagnosis

A

Culture (BAP and MacConkey) produces water-soluble blue/green pigment with a “fruity” smell.

113
Q

Pseudomonas aeruginosa Treatment

A

Cefepime and levofloxacin

Microbiology (4 decks)

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