Microbiology Flashcards
1
Q
Common pathogens affecting the nasopharynx?
A
Mostly viral: rhinovirus, coronavirus
2
Q
Common pathogens affecting the oropharynx?
A
Mostly bacterial: Group A Strep (S. pyogenes), Diptheriae, EBV, Adenovirus, Enterovirus, HIV (initial infection)
3
Q
Common pathogens affecting the epiglottis?
A
Mostly bacterial: Haemophilus influenzae type B
4
Q
Common pathogens affecting the middle ear and parasinuses?
A
Mostly bacterial: Step pneumoniae, Haemophilus influenzae (non-typeable)
5
Q
Contrast the clinical features of viral vs bacterial pharyngitis.
A
Viral (more common cause):
- conjunctivitis, cough, rhinorrhea (more nasal discharge)
- fever less common in adults
- discomfort more than true malaise (not “sick”)
Bacterial (usually Group A Strep): appear sicker
- more erythema, swelling, white-ish exudate
- high fever (>101)
- tender anterior cervical lymph nodes
- NO conjunctivitis, cough, rhinorrhea
6
Q
Pharyngitis can rarely be associated with what more serious disease?
A
Scarlet fever
7
Q
What are petechiae, and what are they associated with?
A
Small red spots on the soft palate. Associated with inflammation of the oropharynx
8
Q
What is the major virulence factor of Group A Strep?
A
M protein (M for mimicry)
- it’s a helical anti-phagocytic protein on the outer surface of the protein
- mimics our own surface proteins, to avoid phagocytosis; if an anti-body is made, it causes autoimmune problems
- e.g., causes the anti-cardiac antibody that causes valve deposits in rheumatic heart disease
9
Q
Major characteristics of Haemophilus influenzae?
A
Gram negative coccobacilli
- Oxidase positive
- requires X (hemin) and V (NAD or NADP) growth factors to culture; AKA grows on chocolate agar
10
Q
H. influenzae type B (encapsulated) can cause what diseases in children?
A
- Meningitis*
- Epiglottitis*
- Pneumonia*
- Bacteremia
- Cellulitis
- Septic arthritis
11
Q
Non-typeable H. influenzae (non-ecapsulated) can causes what infections?
A
- acute otitis media
- sinusitis
- conjuctivitis (outbreaks common in daycares)
12
Q
Mode of action of diptheria toxin?
A
inhibits protein synthesis
13
Q
Cells in what organs have receptors that make them susceptible to diptheria toxin?
A
Heart and nerve cells
14
Q
What are the characteristics of Cornyebacteria diptheriae?
A
- Gram positive rods
- form Chinese letters on culture
- non-motile, non-spore forming
- catalase positive
15
Q
What is the hallmark clinical feature of diptheria toxicity?
A
Pseudomembrane visible at the back of the throat
16
Q
What virus is usually responsible for the common cold?
A
Rhinovirus
17
Q
Why does the rhinovirus usually stay isolated to the nasopharynx?
A
It’s temperature sensitive - grows optimally at 88-90 degrees (further into the body gets too hot)
18
Q
What is the primary receptor rhinovirus uses to infect the body?
A
ICAM-1
19
Q
Who has more difficulty fighting off a rhinovirus?
A
Asthmatics and immune compromised
20
Q
Treatment for rhinovirus infection?
A
Symptomatic
21
Q
Viruses that cause upper respiratory infections?
A
- Rhinovirus
- Respiratory Syncytial Virus
- Adenovirus
- EBV
22
Q
Common causes of acute, TYPICAL community acquired pneumonia?
A
- Strep pneumoniae*
- Staph aureus
- H. influenzae (esp with COPD)
- Gram-negative enterics (hospital acquired)
23
Q
Clinical presentation of TYPICAL community acquired pneumonia?
A
- high fever
- shaking chills
- chest pain
- lobar consolidation (X-ray)
24
Q
Common causes of acute, ATYPICAL community acquired pneumonia?
A
- Mycoplasma pneumoniae*
- Chlamydia pneumoniae, psittaci
- Legionella pneumophila
- influenza and other viruses
- Coxiella burnetii
25
Clinical presentation of ATYPICAL community acquired pneumonia?
Less severe illness than typical.
- insidious onset
- low grade fever
- dry cough
- headache
- diffuse pattern on X-ray (looks worse)
- more constitutional symptoms than respiratory
26
Characteristics of Strep pneumoniae?
- G+, lancet shaped cocci
- catalase negative
- alpha-hemolytic
- mucoid colonies (bc of capsule)
- bile soluble
- susceptible to optochin* (growth inhibition test, separates it from other Streps)
27
What is the major virulence factor of Strep pneumoniae?
anti-phagocytic capsule (difficult for C3b to opsonize)
28
When is there an elevated risk of a bacterial upper respiratory tract infection?
- After a viral infection (esp influenza)
- compromised pulmonary function (asthma)
- alcoholism
- general anesthesia
- immunity impaired
- very young (<2) or very old
- blacks, American Indians, Alaskan Natives
29
Clinical presentation of pneumococcal pneumonia?
- lobar pneumonia on x-ray
- sudden onset
- fever
- pleuritic pain
- rusty sputum
- positive blood cultures in 30%
30
Characteristics of mycoplasmas?
- Smallest bacteria (that cause human disease) --> filterable
- lack a cell wall (no peptidoglycan)
- cell membrane resembles ours (don't gram stain)
31
Treatment for M. pneumoniae infection?
Antibiotics (usually beta-lactam resistant)
- Tetracycline
- Erythromycin
- Azithromycin
32
Characteristics of Chlamydiaceae?
- obligate intracellular bacteria
| - cell envelope similar to G- bacteria (no detectable peptidoglycan)
33
2 developmental forms of Chlamydia?
Elementary body: infectious form
- small, dense
- extracellular
- metabolically inactive
- disulfide cross-linked outer membrane proteins
Reticulate body: replicative form
- large
- intracellular
- metabolically active
- osmotically fragile
- replicate inside vacuoles in the cell until they burst
34
Clinical features of Pssittatosis?
- caused by chlamydia psittaci, transmitted via birds
- abprupt onset
- fever, headache, myalgia, mild cough
- abnormal chest exam
- confusion/altered consciousness
- can culture
35
Organism responsible for whooping cough?
Bordetella pertussis
36
Characteristics of Bordetella pertussis?
- G+ rod (short)
| - viruence factors: pertussis toxin and special adhesion molecules
37
What distinguishes Legionella infection other respiratory infections?
GI involvement. Presentation will include nausea/vomiting while most other pneumonias won't.
38
Risk factors for Legionnaire's disease?
- immunosuppression (requires cell-mediated immunity to fight off)
- cigarette smoking
- renal failure
- >50
- AIDS
- hematologic malignancies
- lung cancer
- males
- alcohol abuse
39
Characteristics of Legionella?
facultative intracellular pathogen
- G- slender bacilli (but don't Gram stain)
- multiplies inside macrophage phagosomes, taken up by coiling phagocytosis
- pearly appearance on charcoal culture
- typically grow in water sources
40
What is the Legionella species that most often causes human disease?
Legionella pneumophila
41
Characteristics of Pseudomonas aeruginosa?
- G- rods
- flagellated
- strict aerobes
- oxidase positive
- produce Pyocyanin (green pigment)
- Lactase negative
- artificial grape odor
- found everywhere (esp fruits and vegetables)
42
Virulence factors of Pseudomonas aeruginosa? (7)
- LPS: cytokine agonist
- Alginate capsule: avoid opsonization (stretchy culture appearance)
- Pili: adherence
- Flagella: motility
- Exotoxin A: inactivation of proteins
- Exoenzyme S and T: inactivation of proteins
Alakline protease elastase: protein breakdown
Phospholipase C: hydrolysis of cell membrane
- forms biofilms, particularly in CF patients
43
Common diseases of P. aeruginosa?
- folliculitis
- swimmer's ear
- pneumonia in cystic fibrosis patients
- burn infections
- hospital acquired infections
- cellulitis
- UTIs
44
Common ESBL producers?
Enterobacteriaceae:
- E. coli
- Serratia marsescens
- Enterobacter cloacae
- Klebsiella pneumoniae
45
ESBL?
Extended spectrum beta-lactamases
| - inactivate the newest generation of beta-lactam antibiotics (cephalosporins, carbepenems)
46
3 most common causes of fungal infections?
- Histoplasmosis (most common)
- Blastomycosis
- Coccidioidomycosis
47
General method of transmission of fungal infections?
1. In soil (as a multicellular mold), esp with bird or bat droppings
2. Gets disturbed and aerosolized (construction, person kicking through it)
3. Spores get inhaled
4. Mold germinates into single-celled yeast
5. Yeast cells get taken up by macrophages, which can't kill them, and multiply by budding
6. Travel to lymph nodes
7. Starts respiratory (bc inhaled) --> goes systemic
48
Who is at risk for fungal infections?
Everyone - don't have to be immunocompromised
49
What geographical location is associated with Histoplasmosis var capsulatum?
Mississippi river valley
50
Body's healing response to fugal infection?
Cell-mediated
- macrophages become fungicidal 2-3 weeks after infection
- form granulomas (fibrosis), esp in spleen
- granulomas become calcified within a few years (yeast cells in granulomas can relapse later)
51
Complications of Histoplasmosis infection?
- Mediastinitis (from body's inflammatory response); can lead to acute pericarditis and cardiac tamponade
- progressive disseminated histoplasmosis (in immunocompromised or patients on TNF-alpha inhibitors
52
What should always be considered whenever Histoplasmosis is on a differential (and vice-versa)?
tuberculosis (similar method of transmission and presentation)
53
What geographic location is associated with Blastomycosis?
Southern Mississippi river valley
54
Where does Histoplasmosis typically disseminate to?
Anywhere
55
Where does Blastomycosis typically disseminate to?
- skin (causes warty outgrowths)
- bone
- genitourinary tract (chronic prostatitis)
56
Treatment for fungal infections?
Primary: self-limiting
Moderate: Itraconazole
Severe: Amphotericin B
57
Geographical location associated with Coccidiodes immitis?
San Joaquin Valley (in California), Arizona and northern Mexico; AKA Valley Fever
58
Unique features of Coccidioidomycosis lifecycle?
- Inhaled as an arthroconidia (barrel-shaped collection of spores separated by disjunctor cells)
- arhroconidia become spherules (sphere-shaped) in the lung
- spherules rupture to produce endospores, which can disseminated and form new spherules
59
Clinical presentation of Coccidioidomycosis infection?
Fever, cough, chest pain, fatigue, SOB, chills, myalgias, night sweats, weight loss, lymphadenopathy.
Almost always has a pulmonary component, even when it disseminates
Eosinophilia in 25% of patients (big exam giveaway)
60
Most common dissemination locations for Coccidioidomycosis?
Skin, bone, meninges (usually only disseminates in immunocompromised)
61
Geographical association of Paracoccidioidomycosis?
tropical and subtropical Central and South America
- patients may have recently traveled or immigrated
- disease can re-activate years later
62
Unique characteristics of Paracoccidioidomycosis life cycle?
yeast form: multiple buds in pilot wheel shape
63
Clinical hallmark of Paracoccidioidomycosis?
chronic mucocutaneous ulcers of the mouth
64
Dissemination location of Paracoccidioidomycosis?
lymphadenopathy, organomegaly, and bone marrow involvement
65
Clinical presentation of infleunza infection?
abrupt onset, headache, high fever, chills, myalgias, malaise, sore throat, non-productive cough, rhinorrhea
66
Complications of influenza?
- Secondary bacterial pneumonia (S. pneumonia, S. aureus, H. influenzae): more common, less severe
- viral pneumonia: rare, more severe
- myositis and cardiac involvement
- neurologic symptoms (Guillain-Barre, encephalopathy, encephalitis, Reye's)
67
Complications are more common in which patients?
- older (>65)
- ppl in nursing homes or chronic care facilities
- underlying CV or pulmonary problems (e.g. asthma)
- hospitalized
- kids on aspirin therapy
- women in 2nd-3rd trimester of pregnancy
68
Characteristics of influenza virus?
- enveloped RNA virus
- A and B types cause human disease
- virulence factors: hemagglutinin (viral attachment & membrane fusion in low pH) and neuraminidase (virus release & deaggregation)
69
Who is recommended to get flu vaccine?
pregnant women, child caregivers, healthcare personnel, kids 6 mo to 24 yrs, adults up to 64 at risk for complications
70
What antivirals inhibit Neuraminidase?
Oseltamivir (Tamiflu) and Zanamivir (Relenza)
- neuraminidase releases the flu virus from the cell surface for spread
- good for both Type A and B
71
What antivirals inihibit the M2 ion channel?
Amantadine and Rimantadine
- M2 ion channel facilitates flu virus dissembly and HA maturation
- only good for Type A flu
- reduces severity if given early
72
Clinical presentation of tuberculosis?
Cough, weight loss/anorexia*, fever, night sweats*, hemoptysis, chest pain, fatigue
73
Method of transmission/infection of TB?
1. inhalation of droplet nuclei
2. bacilli implant and multiply in alveoli
3. inflammation --> caseous necrosis
4. bacilli transmitted to lymph nodes --> dissemination (usually controlled, cell-mediated immunity)
5. Ghon complex heals (fibrosis and/or calcification); may contain virulent bacteria
6. Can reactivate later
74
What is the Ghon complex and where is it seen?
Ghon complex = primary TB lesion + infected adjoining lymph node. Usually seen around the hilum of the infected lung
75
Where in the lung will TB typically gravitate?
Upper lobes (more O2)
76
Common triggers for TB reactivation?
- Diminished immune response
- malnutrition
- aging
77
Miliary TB?
TB lesion spread throughout - Lymphadenitis from M. bovis (unpasteurized milk) can become miliary TB
78
Disseminating locations of TB?
- reticuloendothelial system: lympthatics, liver, spleen, bone marrow --> Miliary TB (can also result from Lymphadenitis from M. bovis)
- brain/spinal cord --> meningitis
- bone/muscle --> Pott's Disease
79
Who gets an Interferon gamma release assay?
Used on ppl who have been vaccinated for TB and would have a positive PPD. IFN-gamma test is more specific to the human disease.
80
How to distinguish active from latent TB
- imaging (x-ray)
| - culture and smear for acid fast bacilli (gold standard): don't stain, and waxy membrane doesn't hold the dyes
81
Virulence factors of Mycobacterium species (TB)?
Phenolic Glycolipid I: binds complement
| Lipoarabinomannan: toxic to macrophages
82
Treatment for TB?
Infection w/o symptoms: 9 months of isoniazid therapy (blocks synthesis of mycolic acids)
Infection w symtoms: RIPE (rifampin, isoniazid, pyrazinamide, ethambutol)
83
How to diagnose Group A Strep infection?
Throat swab for antigen against Group A Strep
84
How to diagnose rhinovirus?
Clinically (symptoms)
85
How to diagnose respiratory syncytial virus?
- Antigen detection by ELISA IFA
- virus culture
- RT PCR
86
How to diagnose adenovirus?
- antigen detection by ELISA, IFA
- CFT
- virus culture
- PCR
87
How to diagnose EBV?
- Heterophile antibody
- atypical lymphocytes
- EBV antibody ELISA
- PCR
88
How to diagnose M. pneumoniae?
- difficult to culture
- Serology: 4x increase in IgM antibody specific to M. pneumoniae
- test for cold agglutinins (not specific)
89
How to diagnose C. pneumoniae?
- difficult to culture
- serology: IgM to 1:64, 4x increase in IgG
- variations in NAATs
90
How to diagnose C. psittaci?
- Culture from respiratory secretions
- Serology: 4x increase in antibody titer, IgM > 1:16, microimmunofluoresence
- NAATs
91
How to diagnose Legionella genus?
- Specific LPS antigen in urine
- Culture: bronchoalveolar lavage
- nucleic acid probes
- serology (no Gram stain)
92
How to diagnose Pseudomonas aeruginosa?
- Culture: lactose non-ferment ring
- oxidase positive
- green pigment-producing (pyocyanin)
- grape-like odor
93
How to diagnose Histoplasmosis?
- Culture is gold standard (but takes 2-4 weeks)
- fungal stain (not sensitive)
- serology (more sens, but may flag a prior infxn)
- antigen: not sensitive for mediastinal or pulmonary
94
How to diagnose Blastomycosis?
- culture
| - serology not helpful
95
How to diagnose Coccidioidomycosis?
- sputum or tissue eval
- culture (dangerous)
- serology: rising titers are a bad prognostic sign
96
How to diagnose Paracoccidioidomycosis?
- direct microscopy
- tissue biopsy
- culture
97
How to diagnose TB?
- PPD
- Biopsy of ghon complex (not desired bc infectious)
- Sputum smear (acid fast stains)
98
How to diagnose UTI?
urine collection, analysis, and culture:
- uncomplicated: single species > 10^5 bacteria/ml
- complicated: 10^2-10^4 bacteria/ml (could be multiple species)
- catheter associated: multiple species common, biofilms
99
Innate defenses against UTI?
- Low pH
- Urea
- organic acids
- Tamm-Horsfall protein
- Lactoferrin
- Lipocalin
- Antimicrobial peptides
- *Unidirectional flow
100
Risk factors for UTI?
- Female (higher incidence)
- Sexual intercourse
- Elderly
- Pregnant
101
Presentation of cystitis?
Dysuria, frequent urination, suprapubic pain
102
Presentation of pyelonephritis?
```
Flank pain
fever
nausea, vomiting, chills
inceased C-reactive protein
Bacteremia (30%)
```
103
Major causes of uncomplicated UTI?
1. E. coli (normal gut flora)
| 2. Staph saprophyticus
104
Virulence factors of E. coli?
- Type I fimbrae: adherence to uroepithelial cells and exfoliation of bladder walls
- Pap pili: adhere to digalactoside-receptors to colonize kidney
- Hemolysin: damages cell membranes
- Cytonecrotizing factor (CNF toxin): inhibit Rho GTPaes in cytoskeleton
105
Virulence factors of Staph saphrophyticus?
- Adhesins
| - Urease: breaks down urea to ammonia and carbamate (raises urine pH)
106
Characteristics of E. coli?
```
Enterobacteriaceae family
G- straight rods
facultative anaerobe
glucose fermenters
oxidase negative
```
107
Characteristics of Staph saphrophyticus?
- G+ cocci in clusters
- coagulase negative
- novabiocin resistant (distinguishes it from Staph epidermidis)
108
Associations for complicated UTIs?
- metabolic disorders
| - kidney stones
109
Presentation of catheter-associated UTIs?
often nonspecific
- fever
- leukocyotisis
- pyuria (>50 WBC/hpf)
110
Common causes of complicated UTIs?
Proteus mirabilis
Staph aureus
Staph epidermidis
Enterococcus faecalis
111
Characteristics of Proteus mirabilis?
- Enterobacteriaceae family
- G- straight rods
- glucose fermenters
- oxidase negative
- swarming motility on solid agar (ripple pattern)
- produces urease (virulence factor to raise urine pH)
- usually invades upper urinary tract
112
Risk factors for Pseudomoas aeruginosa infections?
catheterization and kidney stones (can result in UTIs)
113
Virulence factors of Staph epidermidis?
```
antibiotic resistance
biofilm formation (can form on indwelling foreign devices like catheters or pacemakers)
```
114
Virulence factors of enterococcus faecalis and E. faecium?
- can become blood-borne
| - antibiotic resistance
115
What causes croup?
Parainfluenza virus AKA paramyxovirus
