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Microbiology Flashcards

1
Q

What is the mechanism of the Diptheria Toxin?

A

Blocks host cell protein synthesis
AB domain binds, A domain is endocytosed, B domain assists in acidification and translocation of A domain to cytosol, A domain ADP ribosylates EF2 blocking hydrolysis of GTP which is required for movement of ribosomes.

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2
Q

How to Superantigens work?

A

They complex MHC molecules with TCRs to stimulate antigen independent activation of lymphocytes and creation of IgM.

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3
Q

What are the most common agents responsible for diseases of the nasopharynx?

A

Rhinovirus, coronavirus, other respiratory viruses, Staph Aureus.

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4
Q

What at the most common agents responsible for disease in the oropharynx?

A 
Group A Strep
Corynebacterium Diptheria
EBV
Adenovirus
Enterovirus
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5
Q

What are the most common agents responsible for disease in the middle ear and paranasal sinuses?

A

Strep Pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Strep Pyogenes

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6
Q

What are the most common agents of infection of the epiglottis?

A

Haemophilus influenzae

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7
Q

What are the microbiological characteristics of Group A strep?

A 
Gram positive cocci in chains
Catalase Negative
Beta hemolytic (have clear space)
Bacitracin sensitive
Confirmed with anti-lancefield A test
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8
Q

How is Group A strep identified and differentiated from Staph Aureus?

A

Staph Aureus is catalase positive and that is the easiest way to tell the two apart.

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9
Q

What are the characteristics of viral pharyngitis?

A

More nasal discharge
Fever less common in adults
Paucity of clinical findings

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10
Q

What are the characteristics of bacterial pharyngitis?

A

More erythema and swelling
High fever
Tender cervical lymph nodes
Absence of conjunctivities, cough, and rhinorrhea

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11
Q

What are the major virulence determinants of group A strep?

A 
M protein (IgG response to this responsible for scarlet fever)
Helical antiphagocytic protein
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12
Q

What are the growth media requirements for Haemophilus Influenzae

A

Chocolate agar consisting of Hemin and NAD or NADP (will not grow without both)
Grows best in 5-10% CO2

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13
Q

What clinical features distinguish H. Influenzae

A

Requires Chocolate Agar
Oxidase positive
Requires Hemin and NAD

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14
Q

What are the Characteristics of the H. Influenzae B capsule?

A

Antiphagocytic

Protective against antibodies

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15
Q

What types of diseases are associated with encapsulated H. Influenzae B?

A

Meningitis
Epiglottitis
Pneumonia (seen often with COPD in adults)

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16
Q

What diseases are typically caused by non-encapsulated H. Influenzae?

A

Acute otitis media, sinusitis
Exacerbation of COPD
Conjunctivitis
Invasive infection in immunocompromised

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17
Q

How is the H. I-B virus destroyed in the body?

A

Anti-capsular antibodies are extremely important in the elimination.
Antibodies mediate complement dependent phagocytosis. Complement can also cause lysis.

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18
Q

How do you treat H I B?

A

Start with 3rd generation cephalosporin, if organism is susceptible to ampicillin switch to that. (Meningitis often treated empirically with both)

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19
Q

What is in the conjugate vaccine?

A

HIB coupled with Diptheria toxoid.

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20
Q

What is the recommended vaccination schedule for HIB?

A

2 months, 4 months, 6 months, and 12 months (Recommended that mother gets revaccinated to confer IgG immunity)

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21
Q

How do you identify C diptheriae in the lab?

A

Turns black on tellurite agar, catalase positive, typically appears as “chinese letters” on H&E

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22
Q

What are the clinical features of diptheria?

A

Incubation period 2-5 days
May involve any mucous membrane
Classified based on site of infection
Creates a pseudomembrane

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23
Q

How do you treat diptheria?

A

Antitoxin (horse origin may cause serum sickness)
Antibiotics to eradicate organisms
Both must be given

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24
Q

What is the cellular receptor for binding of the major group of rhinoviruses?

A

ICAM-1

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25
What is the general structure of the rhinovirus?
+ssRNA is infectious Small, Icosahedral >100 serotypes Temperature sensitive (likes nasopharynx)
26
How does replication of rhinovirus occur?
VP4 binds cellular receptor, virus mRNA directly binds to ribosomes, viral proteases cleave into VP0-VP1 and VP3, Viral RNA dependent RNA poly generates -ssRNA and makes +ssRNA from it. VPo is cleaved into VP2 and VP4, genome and proteins self assemble and the virus is released
27
Where does the RNA polymerase for Rhinovirus come from?
The virus encodes it's own RNA polymerase.
28
How is Rhinovirus transmitted?
Aerosol droplets and directs contact, primarily in the fall and winter
29
How does the virus cause disease?
Immunopathologic Causes nasal discharge, congestion, and sneezing, sorethroat, muscle aches, fatigue...etc May get into lower respiratory system of immune compromised people
30
How is immunity conferred?
Mucosal IgA is protective against already encountered serotypes, interferons fight virus but cause pathogenesis.
31
What is the general structure of RSV?
Enveloped -ssRNA genome Two major envelope proteins (G for grab, F for fusion) Encodes it's own Rna dependent Rna Poly
32
What are the characteristics of RSV?
Transmitted by aerosol droplets and direct contact Nosocomial spread common Disease can be severe in immunocompromised people, babies born prematurely, or in children less than 8 months
33
When is RSV the worst?
Primarily during the winter months because droplets stay in the air longer.
34
What is the pathogenesis of RSV?
``` Runny nose Fever Tachypnea Wheezing and breathlessness with edema of the bronchioles (LRT) Continuous coughing (LRT) Cyanosis (LRT) ```
35
Where is immunity conferred against RSV?
Immunity is typically conferred against both serotypes only in the LRT, URT reinfection is common.
36
How is RSV treated?
There is no licensed vaccine to date Ribavirin has been used but is of limited efficacy If severe, supportive care is given
37
Why is there currently no vaccine against RSV?
Infants who were put on a trial with the vaccine developed a severe course of the disease upon re-exposure leading to hospitalization and death is two cases.
38
What is Respigam?
Polyclonal antibody used for passive therapy in patients with sever lower respiratory tract infection by RSV
39
What is Synagis?
Monoclonal antibody indicated in use for patients with high risk of severe LRT infection by RSV
40
What is the structure of Adenovirus?
Unenveloped ds linear DNA genome 51 serotypes are known Replicates in the nucleas
41
How does adenovirus replicate?
``` Temporal replication in the nucleas. Binds via CAR to ICAM-1 Encodes it's own DNA polymerase E1-E1B-E2A-E2B-E3-E4 L1-L5 ```
42
How is Adenovirus transmitted?
Direct contact via FO, contaminated water, or aerosol droplets Immunity against virus is serotype specific Lytic in mucoepithelial cells, latent in adenoids
43
What serotypes of adenovirus cause which pathogenic process?
Ad3, 7 cause pharyngoconjunctival fever in crowded places | Ad4, 7 cause acute respiratory disease in military recruits
44
What respiratory diseases are caused by adenovirus?
``` Febrile, undifferentiated URI Pharyngoconjunctival fever Acutre respiratory distress Pertussis-like symptoms Pneumonia ```
45
What other adenovirus serotypes commonly cause disease?
8, 19 37 cause Keratoconjunctivitis 11 causes hemorrhagic conjunctivitis 11,4,7,1,21 cause acute hemorrhagic cystitis 40-42, 31, 25, 28 cause gastroenteritis
46
How is immunity conferred against adenovirus?
Cell mediated immunity is crucial for clearing infection, long term immunity is conferred against one serotype by antibodies.
47
How is adenovirus treated?
Symptomatic treatment Should resolve in 7-10 days New live vaccine tablet was approved in 2011 for use during basic training
48
What is EBV?
``` y-herpesvirus Enveloped Linear dsDNA Encodes it's own DNA-dependent DNA poly Replicates in the nucleas Encodes numerous host proteins ```
49
What is the epidemiology of EBV?
95% of adults thought to have latent infection Adolescents are major risk group Transmission primarily though saliva Incubation of 6-8 weeks and symptoms persist 2-3 weeks. Infects and replicates in epithelial and Bcells
50
How does EBV infection present?
Sore throat, inflammed tonsils, swollen cervical lymph nodes, splenomegaly, nausea, chills, photophobia, fatigue
51
What are the most common symptoms of infectious Mono?
Pharyngitis, cervical lymphadenopathy, Sore throat, >10% atypical lympocytes
52
What genes allow for latency of EBV?
EBER and EBNA1
53
How is EBV diagnosed?
Atypical lymphocytes, agglutination test for heterophile antibodies, EBV antibody ELISA, PCR for EBV
54
What is characteristic of typical pneumonia?
High fever, chills, chest pain, lobar consolidation
55
What is the most common cause of Typical CAP?
Strep Pneumoniae Staph Aureus H. Influenzae
56
What is atypical CAP?
less severe illness, dry cough, headache, diffuse pattern on xray
57
What are the most common causes of atypical CAP?
``` Mycoplasm pneumoniae Chlamydia pneumonia Legionella pneumophila Viruses Coxiella ```
58
What are the bacterial characteristics of Strep Pneumoniae?
Alpha hemolytic (green color due to breakdown of heme by pneumolysin) Mucoid colonies Gram positive, catlase negative, susceptible to optochin and bile
59
What is the major virulence factor of Strep Pneumo?
Thick polysaccharide capsule which interferes with deposition of C3b on bacterial surface, no phagocytosis 90+ serotypes prevent immunity against all types Loss of capsule = loss of virulence
60
What are predisposing factors to pneumococcal pneumonia?
``` Viral URT infection Compromised pulmonary fx Age Black, Indians, Inuits Impaired immunity Type 3 serotype of S. pnuemoniae in URT ```
61
What are the signs and symptoms of pneumococcal pneumonia?
Sudden onset, rusty sputum, pleuritic chest pain, lobar consolidation
62
What are possible sequelae of Pneumococcal pneumonia?
Death Neurological deficits from meningitis Hearing impairment secondary to otitis media
63
Who is most susceptible to drug resistant pneumococcal pneumonia?
Most is resistant to penicillin | The very young and very old are more susceptible
64
Why is the conjucate PCV13 vaccine more effective?
Conjugation allows for recognition (not superantigen) this allows for IgG creation, somatic hypermutation, and a secondary response.
65
What makes mycoplasma unique?
Smallest bacteria Can pass through .45 um filters Lack cell wall (no peptidoglycan) Surrounded by lipid bilayer containing sterols
66
What forms of mycoplasma are normally human pathogens?
M. Pneumoniae M. Hominis (ureteritis) M. Genitalium (ureteritis) Ureaplasma species (ureteritis)
67
How do mycoplasm colonies look in culture?
Require serum for growth and have a fried egg appearance under a microscope
68
What is the epidemiology of M. pneumoniae?
``` No seasonality Higher in young and old Spreads in dorms and barracks Transmission through close contact via droplets 2-3 week incubation period. ```
69
What are the pathogenic mechanisms of M. Pneumoniae infections?
Respiratory entry, attaches to epithelium of LRT via P1 adhesin to NA containing glycoprotein Produces CARDS toxin which has ADP-ribosyltransferase activity causing deterioration of the cilia Phagocytosis by Ms leads to inflammation Vigorous CMI leads to sever clinical form
70
How is M. Pneumoniae diagnosed?
Serology, cold agglutinins
71
What antibiotics are recommended for M. Pneumonia?
Tetracycline Macrolides (emerging resistance) B-lactams not effective
72
What Chlamydia forms cause pneumonia?
C. Pneumoniae | C. Psittaci (birds)
73
What are characteristics of Chlamydiceae?
``` Have DNA, RNA, and 70s ribosomes Divide by binary fission Small genome Carry plasmids Cell Envelope ```
74
What is the infectious process of chlamydia?
Elementary bodies are phagocytosed, reticulate bodies form and begin to multiply by binary fission, chlamydia antigens are expressed and released from cell surface, reticulate bodies reorganized to elementary bodies and are released to cause further infection
75
What are the pathogenic mechanisms of chlamydia?
Cytopathic effect on host cells Immunopathogenesis causing inflammation and scarring in effort to clear disease Establishes persisten infection
76
How is C. Pneumoniae diagnosed?
Serology Igm titer greater that a 1:64 or a four fold rise of IgG titer is acuted serum and 4 week later serum
77
How does psittaci infection occur?
Zoonotic infection causes wasting disease in birds, transmissible to humans via dried feces or direct contact Patients usually are poultry industry workers, vets, or exotic bird owners Presents with pneumonia and confusion
78
How is chlamydia treated?
Doxycycline Macrolides (empiric therapy for all atypical pneumonias)
79
What does pertussis look like on H and E?
Blue Safety pin shaped rod
80
What is the environmental niche of Legionella?
``` Gram negative Lives in iron rich soil Lives in water Endures extreme temp Resists chlorination Survives inside amoebas ```
81
What are the risk factors for Legionella?
Immunosuppression, smoking, renal failure, age over 50, cancer, male sex, alcohol abuse
82
How does legionella live intracellularly?
Taken up by coiling phagocytosis, ribosomes surround phagosome, bacteria multiplies, host cell lyses and bacteria escapes.
83
How do you identify legionella?
Gram negative slender bacilli Need to do bronchoalveolar lavage to get MACs in which they live Growth media is Buffered Charcoal Yeast Agar which has amino acids, iron, and trace metals
84
What is pontiac fever?
Disease associated with legionella causing flu like symptoms.
85
How do you diagnose Leginella?
UA done with ELISA for LPS antigen BAL with Flourescent staining or Dieterles silver stain 4 fold antibody rise in serum
86
What antibiotics treat Legionella?
Macrolides (-romycin) Flouroquinolones (-oxacin) B-lactams ineffective
87
What is the environs for Psedomonas Aureginosa?
Gram negative rods Flagellated Strict aerobes (Nonfermenters)
88
Where is psudomonas found?
Everywhere Fresh Fruits and Veggies Hot Tubs Respiratory Therapy Equipment
89
What are the most important virulence factors of pseudomonas?
``` LPS (cytokine agonist) Alginate Capsule (resists opsonization) Pili (adherence) Flagella (motility) Exotoxin A ```
90
What does pseudomonas Auereginosa cause?
``` Folliculitis Swimmers ear Pneumonia in CF patients Burn infections Nosocomial infections Cellulitis UTIs ```
91
What is the alginate capsule?
1-4 linked B-D-mannuronate and its C-5 epimer a-L-guluronate
92
Why is Pseudomonas less susceptible to antibiotics in CF patients
Biofilm formation
93
How is P. Auruginosa characterized in the lab?
``` Lactase - growth on McConkey Agar Oxidase positive Pyocyanin production (green) Glucose oxidation only Smells like grape soda ```
94
What antibiotics are useful against Pseudomonas?
``` Aminoglycosides Carbapanems Carboxypenicillins Ureidopenicillins Cephalosporins Flouroquinolones Monobactam ```
95
What are the characteristics of Klebsiella Pneumonia?
Aspiration pneumonia Gram -, Lac + Mucoid Capsule Targets alcoholics
96
What are important concepts of endemic mycoses?
All acquired by inhalation of spores Specific geographic locations Acute or reactivated Range in severity
97
What are the typical characteristics of Histoplasmosis?
``` Similar appearance to TB White or Brown hyphal colonies Yeast form appears as "dot disease" Transmitted in soil in areas contaminated by bird or bat droppings Mostly in mississippi river valley ```
98
What is the pathogenesis of Histo?
Spores get into the lungs where they are taken up by dust cells in their yeast form, travel to lymph nodes and spread everywhere (lungs, lymph, liver, spleen, bone marrow) Small amounts remain in granules and can become reactivated years later
99
What is the most common clinical finding in Histo?
None
100
What predisposes somboy to progressive disseminated Histo?
TNF-a inhibition
101
How is Histo diagnosed?
Culture (takes a while) Fungal stain (low sensitivity) Serology (can have false negs or pos) Antigen
102
How are dimorphic fungi treated?
``` Moderate disease (Itraconazole) Severe disease (Amphoteracin B) ```
103
What does Blastomyces look like?
White tan filamentous mold colonies with round to over conidia Spherical yeast with thick double contoured walls Reproduces by broad base budding Dogs are 10x more susceptible than humans
104
Where is blastomyces found?
Southern Mississippi river valley
105
What is the pathogenesis of blastomyces?
Inhalation of conidia into alveoli causes yeast form to multiply by budding leading to hematoginous dissemination (it is the great pretender) Most common in lungs, skin, bone and genitals Typically presents like anything else but doesn't respond to antibiotics
106
What is coccidioidomycosis?
Mold form grows quickly and forms anthroconidia Yeast form forms spherules which produce endospores Found in San Juaquin Valley of CA Can cause eosinophilia
107
How does coccy typically present?
Like pneumonia, usually disseminated to skin, bone, and meninges (uncommon in immunocompetent hosts) Filipinos and Blacks get it worse Late pregnancy and post-partum is bad
108
How do you diagnose coccy?
Microscopic evaluation of tissue Serology Calcaflour white stain Methanamine silver stain
109
What is the epidemiology of TB?
70% of new contacts not infected 30% are infected 95% of new infected develop latent infection 5% develop disease within two years 5% with latent infection develop active tuberculosis
110
Typical presentation of TB?
``` Cough Weight loss Hemoptysis Constitutional Chest pain Fatigue ```
111
Who is at risk for TB?
``` Close contact with TB Foreign born from TB Area Prisoners Health Care Workers Underserved Ethnic minorities Children exposed to adults with TB IV druggies ```
112
Where is Latent Vs. REactivated TB found?
Latent found near the hilum and in the nearest lymph node in the form of a ghon complex Reactivated in the upper lobe of the lung Can proceed to miliary TB and proceed to other locations in the body causing potts disease, meningitis, or lymphadenitis or any other disease
113
How do you screen for TB?
Positive PPD, Interferon Y test. BCG vaccine can give false positive on PPD Acid Fast bacilli are found on sputum Cavitary lesion in upper lobe on Xray (can be histo)
114
What are the major components of the cellular envelope of TB?
``` Waxes Mycolic acids Polysaccharides Peptidoglycan PGL-I (so it can get phagocytosed) Lipoarabinomannan ```
115
What stain causes TB to flouresce?
Auramine-Rhodamine stain
116
On what agar is TB grown?
Lowenstein-Jensen agar (buff colonies after 3 weeks)
117
How is TB treated?
Latent (9 months Isoniazid) | Active (Rifampin, Isoniazid, Pyrazinamide, Ethambutol) R.I.P.E
118
What are the innate defenses in the urinary tract?
``` Low pH Urea Organic Acids Tamm-horsfall protein lactoferrin Lipocalcin Antimicrobial peptides ```
119
What are the signs and symptoms of cystitis?
Dysuria Frequent urination Suprapubic pain
120
What are the signs and symptoms of pyelonephritis?
``` Flank pain Fever Nausea Increased CRP Bacteremia ```
121
What are the major players in Uncomplicated UTI?
Members of the Enterobacteriaceae family (normal intestinal flora) E. Coli, K. Pneumoniae, Proteus Mirabalis... Gram negative, oxidase negative
122
What are the virulence factors of uropathogenic E. Coli?
Type 1 fimbriae (colonization of bladder) P pili (adhere to digalactoside receptors, colonization of kidneys) Hemolysin (damages cell membranes) CNF toxin (inhibits Rho GTPases of cytoskeleton)
123
What is a gram positive cause of UTI?
S. Saprophyticus
124
How is S. Saprophyticus identified in a lab?
Gram positive cocci in clusters Non-hemolytic, white Catalase positive Coagulase Negative
125
What are complicated UTI?
Associated with metabolic disorders that are secondary to anatomic or functional abnormalities (UTI + kidney stones)
126
What are catheter associated UTIs?
80% of nosocomial UTIs related to catheterization | Fever, leukocytosis, pyuria
127
What are the players in Complicated and Caterter UTI?
``` Enterobactericeae (Straight rods, glucose fermenters, oxidase negative) Proteus mirabilis E. Coli Klebsiella Pseudomonas S aureus ```
128
What common organisms form biofilms on indwelling catheters
Extracellular crosslinking polymers that facilitate adhesion are found in S epidermidis, S aureus, E. faecalis, Candida albicans, pseudomons, klebsiella, E. coli, P. Mirabilis
129
What is the most common cause of catheter associate UTIs?
Proteus Mirabilis Produces swarming motility on solid agar Produces urease Prediliction of UUT
130
What is the relationship between bacterial urease and renal calculi?
Bacterial urease causes stones to precipitate | This is found in Proteus Mirabellis
131
What are the characteristics of Pseudomonas?
``` Gram negative rods Non-fermenters Non-lactose fermenters Oxidase positive Pyoverdin (green) ```
132
What is the criteria for uncomplicated UTI plating?
>10^5 bacteria/ml of a single species
133
What is the criteria for a complicated UTI
10^2-10^4 bacteria/ml
134
What is a positive suprapubic tap?
Isolation of any organism

Pulmonary Physiology (5 decks)

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