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Microbiology Flashcards

1
Q

What are the four classes of dermophytes?

A
  1. Trichophytin
  2. Microsporum
  3. Epidermophytin
  4. Malassezia furfur
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2
Q

What are the common yeast organisms? Name 3.

A
  • Candida albicans
  • Cryptococcus neoformans
  • Pneumocystis jirovecii
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3
Q

What is a common mould organism?

A

Aspergillus fumigatus

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4
Q

What are some common dimorphic fungal organisms? Name 5.

A
  • Histoplasma capsulatum
  • Blastomyces dermatitidis
  • Coccidioides immitis
  • Paracoccidioides brasiliensis
  • Sporothrix schenkii
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5
Q

What are the treatments for Candida infections?

A

Vulvovaginitis: topical azoles, nystatin

Oral/Esophageal thrush: oral fluconazole, caspofungin

Systemic infections: oral/IV fluconazole, caspofungin, or amphotericin B

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6
Q

What are the three possible manifestations of Aspergillus infection?

A
  1. Allergic bronchopulmonary aspergillosis (ABPA)
    >> Common in asthma and cystic fibrosis
    >> Can cause bronchiectasis and eosinophilia
  2. Aspergillomas: esp. after TB infection
  3. Invasive aspergillosis (systemic)
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7
Q

What are the microscopic characteristics of Aspergillus fumigatus?

A

Narrow septate hyphae branching at acute angles

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8
Q

What are the microscopic characteristics of Mucor and/or Rhizopus speciies?

A

Broad, irregularly-shaped non-septate hyphae branching at right angles

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9
Q

What is the treatment for Aspergillus infection?

A
  • Voriconazole
  • Lipid amphotericin B
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10
Q

What are the common clinical manifestations of Rhizopus/Mucor infections?

A

Invasion via the cribiform plate leads to rhinocerebral infections
>> Frontal lobe abscesses
>> Black necrotic eschar on the face
>> Cranial nerve involvement

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11
Q

What is the treatment for Mucor/Rhizopus infections?

A
  • Surgical debridement
  • Amphotericin B
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12
Q

What are the prophylactic drugs for PCP?
When should we start giving them in an AIDS patient?

A
  • TMP-SMX (Bactrim)
  • Pentamidine
  • Dapsone
  • Atovaquone

>> Start prophylaxis when CD4+ count <200cells/mm3 in HIV patients

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13
Q

How do we prevent cryptococcal meningitis in AIDS/HIV patients?

A

Fluconazole

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14
Q

What are the clinical manifestations of Sporothrix schenkii infection?

A
  • Local pustule from skin trauma, usually by a (rose) thorn
  • Painless ulcerating ascending lymphangitis
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15
Q

How can we treat Sporothrix schenkii infection?

A
  • Oral potassium iodide
  • Itraconazole
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16
Q

What are some common infections caused by dermatophytes?

A
  • Tinea pedis (athlete’s foot)
  • Tinea cruris (groin – jock’s itch)
  • Tinea corpus (body – ringworm)
  • Tinea capitus (head – ringworm)
  • Tinea unguium (nails – onychomycosis)
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17
Q

What are the treatment for typical superficial dermatophyte infection?

A
  • Topical terbinafine
  • Topical azoles
  • If extensive or if involving the scalp or hair
    >> Oral terbinafine
    >> Oral azoles
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18
Q

What is the treatment for onychomycosis (tinea unguium)?

A
  • Oral terbinafine
  • Oral atroconazole
  • Oral fluconazole
    >> 6 weeks - 6 months: hands
    >> 12 weeks - 12 months: feet/toes
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19
Q

Where are the endemic locations of Histioplasma capsulatum?

A
  • Mississippi River Valley
  • Ohio River Valley
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20
Q

What are the endemic locations of Blastomyces dermatiditis?

A
  • States East of the Mississippi River
  • South to Central America
  • North to Canada
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21
Q

What are the endemic locations of Coccidioides immitis?

A
  • California
  • Southwestern United States (Texas)
  • San Joaquin Valley
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22
Q

What are the endemic locations of Paracoccidioides brasiliensis?

A

Latin America

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23
Q

What is the route of transmission of Histioplasma capsulatum?

A

Bird and bat droppings
>> Contact/inhalation

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24
Q

What is the microscopic feature of Histioplasma capsulatum?

A
  • Smaller than RBCs
  • Hides in macrophages
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25
What is the microscopic feature of Blastomyces dermatitidis?
- Broad-based budding - Same size as RBCs
26
Which systems are mainly affected in the case of blastomycosis infection?
- Lung - Skin - Bone
27
What is the microscopic feature of Coccidioides immitis?
- Spherule much large than RBCs - Filling with endospores
28
What is the natural life course of Coccidioides immitis?
Barrel-shaped **arthroconidia** \>\> airborne \>\> inhalation \>\> enters lung \>\> switches to **spherules** (NOT YEAST!) \>\> explodes with **endospores**
29
Which systems are mainly affected in the case of coccidioides infection?
- Lungs - CNS - Skin - Bones and Joints
30
What is the route of transmission of Coccidioides immitis?
Inhalation - Case rate increased after earthquakes as spores in the dust are thrown up in the air and easily inhaled - "San Joaquin Valley" Fever
31
What is the microscopic feature of Paracoccidioides brasiliensis?
- Much bigger than RBCs - Multiple "captain-wheel" budding formation
32
What are the general treatment plans for systemic mycoses?
Localized infections - Fluconazole - Itraconazole Systemic infections - Amphotericin B
33
What are the possible causes of systemic mycoses?
- Histioplasma capsulatum - Blastomyces dermatiditis - Coccidioides immitis - Paracoccidioides brasiliensis
34
Which organism causes tinea versicolor?
Malassezia furfur (a dermatophyte)
35
What are the presenting clinical features of tinea versicolor?
Hypopigmented and/or hyperpigmented patches on the trunk and proximal limbs - Light macules coalescing to form large scaling plaques - Not usually pruritic
36
What is the microscopic feature of Malassezia furfur?
"Spaghetti and meatball" appearance on KOH prep
37
What is the treatment for tinea versicolor?
- Topical miconazole - Topical **selenium sulfide** - Oral azoles if severe
38
What is the treatment for Malassezia furfur infection?
- Topical miconazole - Topical **selenium sulfide** - Oral azoles if severe
39
What infections are associated with birds?
- Histoplasma capsulatum - Cryptococcus neoformans - Chlamydophila psittaci - Viruses \>\> H5N1 Influenza \>\> West Nile Virus
40
Which anti-HIV medication is known for causing bone marrow suppression?
Zidovudine
41
What cell wall features are unique to Gram-positive organisms?
- Thick peptidoglycan wall - Lipoteichoic acid
42
What cell wall features are unique to Gram-negative organisms?
- Thin peptidoglycan wall - 2 membranes - Lipopolysaccharides (LPS) endotoxin in the outer membrane - Periplasmic space between the two membranes, containing beta-lactamase
43
What test is useful in determining capsular organisms?
**Quellung reaction** ## Footnote - Anticapsular serum is added to the bacteria - Capsule will appear swollen under microscopy
44
Name some encapsulated bacteria.
**E**ven **S**ome **P**retty **N**asty **K**illers **H**ave **S**hiny **B**odies. ## Footnote - **E**scherichia coli (certain strains) - _**S**treptococcus pneumoniae_ - **P**seudomonas aeruginosa - _**N**eisseria meningitidis_ - **K**lebsiella pneumoniae - _**H**aemophilus influenzae type B_ - **S**almonella typhi - Group **B** streptococcus + *Cryptococcus neoformans*: fungus that causes meningitis in AIDS patients and is also an encapsulated organism. * *The _SHiN_ organisms are very important to remember, and are common causes of infections and death in asplenic patients:** - **S**treptococcus pneumoniae - **H**aemophilus **i**nfluenzae type B - **N**eisseria meningitidis
45
What are the differences in the ribosomes of prokaryotes and eukaryotes?
_Prokaryotes_ - 50S and 30S subunits - 70S ribosomes _Eukaryotes_ - 60S and 40S subunits - 80S ribosomes
46
What are the differences between generalized and specialized transduction?
_Generalized transduction_ - **"Packaging" event** - **Lytic** phages - *Parts of bacterail chromosomal DNA become packaged into viral capside* - Phage infects another bacterium \>\> transfer of genetic material _Specialized transduction_ - **"Excision" event** - **Lysogenic** phages - After incorporation of viral DNA into bacterial chromosome, *when the phage DNA is excised from the bacterial DNA* for production of viruses after activation of the viral infection, flanking bacterial genes are excised WITH it. - DNA is packaged into phage viral capside - Phage infects another bacterium \>\> transfer of genetic material
47
What are the 5 bacterial toxins encoded in a lysogenic phage?
**ABCDE** ## Footnote - Shig**a**-like toxin - **B**otulinum toxin - **C**holera toxin - **D**iphtheria toxin - **E**rythrogenic toxin of *Streptococcus pyogenes*
48
Name some bacteria that do not Gram stain well.
**T**hese **M**icrobes **M**ay **L**ack **R**eal **C**olour. ## Footnote - **T**reponema - **M**ycobacteria - **M**ycoplasma - **L**egionella pneumophila - **R**ickettsia - **C**hlamydia
49
Name the microorganisms that are stained by **Giemsa stain**.
**C**ertain **B**ugs **R**eally **T**ry **H**is **P**atience. ## Footnote - **C**hlamydia - **B**orrelia - **R**ickettsia - **T**rypanosomes - **H**istoplasma - **P**lasmodium
50
What is periodic acid-Schiff (PAS) stain used for?
Staining of: - Mucopolysaccharides - Glycogen \>\> Whipple's disease by Tropheryma whipplei
51
What organisms can be stained by Ziehl-Neelson (carbol fuchsin) stian?
- Mycobacterium - Nocardia
52
What organism can be stained by India Ink?
Cryptococcus neoformans
53
What organisms can be stained by silver stain?
- Fungi (e.g. pneumocystis) - Legionella - Helicobacter pylori
54
Which bacteria can form spores?
- Bacillus: anthracis, cereus - Clostridium: perfringens, tetani, botulinum - Coxiella burnetii
55
Which bacteria have the ability of transformation (i.e. taking up naked DNA from a lysed cell by a living microorganism and incorporating that naked DNA into its own chromosomal DNA)?
**SHiN** ## Footnote - **S**treptococcus pneumoniae - **H**aemophilus **i**nfluenzae - **N**eisseria meningitidis \>\> These three organisms are also mainly responsible for infections and deaths in asplenic individuals, and are also available as capsular conjugate vaccines.
56
Name the bacterial structure. Mediates adherence of bacteria to the surface of a cell
Fimbria
57
Name the bacterial structure. Protects against phagocytosis
Capsule \>\> Organized and firmly adherent glycocalyx
58
Name the bacterial structure. - Rgiid support to bacterial cell - Protects against osmotic pressure differences
Peptidoglycan layer of the cell wall
59
Name the bacterial structure. - Space between the inner and outer cellular membranes - Unique to Gram-negative bacteria
Periplasmic scpae
60
Name the bacterial structure. - Bacterial form providing resistance to heat, chemicals and dehydration - Formed mainly by Bacillus and Clostridium species - Also formed by Coxiella burnetii
Spores/endospores
61
Name the bacterial structure. Forms attachment between two bacteria during conjugation (transfer of DNA material)
Pilus \>\> Sex pilus \>\> F-pilus
62
Name the bacterial structure. - Genetic material within bacteria that contains genes for antibiotic resistance - Not a part of the chromosomal DNA
Plasmid
63
Name the four main methods of bacterial genetic transfer.
1. Conjugation 2. Transposition (by transposons) 3. Transformation (uptake of naked DNA from a lysed cell by a living microorganism) 4. Transduction (generalized VS. specialized)
64
What are the properties of a superantigen? Which bacteria are famous for producing superantigens?
- Exotoxins that are able to bind to MHC II receptors and TCRs **simultaneously** - This induces a polyclonal expansion of T-cells and thus a massive immune response, triggering release of large amounts of cytokines ## Footnote * *Bacteria famous for producting superantigens: - *Staphylococcus aureus* - *Streptococcus pyogenes (Group A Streptococcus)***
65
What are the exotoxins produced by *Staphylococcus aureus*?
- Alpha-toxin: hemolysis - Beta-toxin: sphingomyelinase C - Gamma-toxin \>\> A+B = Hemolysin \>\> B+C = Leukocidin - Delta-toxin: hemolysis - Panton-Valentine leukocidin: bicomponent toxin especially found in MRSA - Superantigens \>\> **Enterotoxins A-E**: food poisoning \>\> **TSST-1**: toxic shock syndrome (tampons; high fever, hypotension, diffuse rash) \>\> **Epidermolytic/exfoliative toxins**: scalded skin syndrome
66
How does endotoxin induce damage in the host tissue?
_1. Macrophage activation_ - IL-1 and IL-6: fever - TNF-alpha: fever, hypotension, cell death and cachexia - Nitric oxide: hypotension - Mediates the occurrence of septic shock _2. Complement activation_ - C3a: hypotension, edema - C5a: neutrophil chemotaxis _3. Tissue factor release_ - Activates the coagulation cascade - Can lead to disseminated intravascular coagulopathy (DIC\_
67
Name four exotoxins that work by inhibiting protein synthesis.
1. Diphtheria toxin of *Corynebacterium diphtheriae* (inhibits EF-2) 2. Exotoxin A of *Pseudomonas aeruginosa* (inhibits EF-2) 3. Shiga toxin of *Shigella* species (inactivates 60S subunit of host ribosomes) 4. Shiga-like toxin of EHEC (inactivates 60S subunit of host ribosomes)
68
Name 4 exotoxins that work by increasing fluid secretion (and thus usually causing watery diarrhea).
1. Heat labile (increases cAMP) and heat stable (increased cGMP) toxins of ETEC 2. Cholera toxin of *Vibrio cholera* (increases cAMP and thus increases Cl- and H2O efflux in the gut) 3. Anthrax toxin of *Bacillus anthracis* (mimics adenylate cyclase) 4. Pertussis toxin of *Bordetella pertussis* (disables Gi protein \>\> increases cAMP)
69
What toxin is secreted by *Corynebacterium diphtheriae* and what is its mechanism of action? What are its clinical effects?
- Diphtheria toxin - Inhibits protein synthesis by **inhibiting elongation factor 2 (EF-2)** - Clinical features \>\> Pseudomembranous pharyngitis \>\> Cardiac cell damage \>\> Nerve cell damage
70
What toxin is secreted by enterhemorrhagic *Escherichia coli* (EHEC), and what is its mechanism of action? What are its clinical effects?
- Shiga-like toxin (verocytotoxin) - Inactivates the **60S subunit** of the hosts' ribosomes by **cleaving adenine from rRNA**, and thus inhibiting protein synthesis - Enhances cytokine release \>\> *hemolytic uremic syndrome (HUS)* \>\> Hemolytic anemia \>\> Thrombocytopenia \>\> Acute renal failure
71
What toxin is secreted by *Shigella* species, and what is its mechanism of action? What are its clinical effects?
- Shiga toxin - Inactivates **60S subunit** of the hosts' ribosomes by **cleaving adenine from rRNA**, and thus inhibits protein synthesis - Clinical effects: \>\> GI mucosal damage -- dysentery \>\> Enhances cytokine release -- hemolytic uremic syndrome (HUS)
72
What toxin is secreted by *Pseudomonas aeruginosa*, and what is its mechanism of action? What are its clinical effects?
- Exotoxin A - Inhibits **elongation factor 2 (EF-2)** and thus inhibits protein synthesis - Causes host cell death
73
What toxin is secreted by enterotoxigenic *Escherichia coli* (ETEC), and what is its mechanism of action? What are its clinical effects?
- Heat stable and heat labile toxins - Heat **labile** toxin overstimulates **adenylate cyclase** \>\> increases intracellular c**A**MP - Heat **stable** toxin overstimulates **guanylate cyclase** \>\> increases intracellular c**G**MP - Clinical effects \>\> Watery diarrhea \>\> ETEC is the leading cause of traveller's diarrhea RMB: **L**os **A**ngeles and **S**in**g**apore!
74
What toxin is secreted by Bacillus anthracis, what are its components and what are their mechanisms of action? What are the clinical effects?
- Anthrax toxin \>\> Edema factor \>\> Lethal factor \>\> Protective factor - **Edema factor** mimics **adenylate cyclase** and thus increases intracellular **cAMP** - Leads to the characteristic edematous borders of the black eschar in cutaneous anthrax
75
What toxin is secreted by *Vibrio cholerae*, and what is its mechanism of action? What are its clinical effects?
- Cholera toxin - Permanently activates **Gs proteins** and thus overstimulates adenylate cyclase \>\> increased intracellular cAMP levels \>\> increased Cl- and H2O efflux - Causes watery diarrhea \>\> Rehydration is *life-saving* in cholera!
76
What toxin is secreted by *Bordetella pertussis*, and what is its mechanism of action? What are its clinical effects?
- Pertussis toxin - Disables **Gi proteins** \>\> adenylate cyclase work uninhibited \>\> increased intracellular cAMP levels - *Whooping cough* \>\> Seen in children \>\> Whoops on inspiration \>\> Coughs on expiration
77
What toxin is secreted by *Clostridium perfringens*, and what is its mechanism of action? What are its clinical effects?
- Alpha toxin - A phospholipase (lecithinase) causing lysis of cell membranes and tissue damage - Clinical effects \>\> Gas gangrene \>\> Myonecrosis
78
What toxin is secreted by *Clostridium tetani*, and what is its mechanism of action? What are its clinical effects?
- Tetanospasmin - Cleaves SNARES that are required for neurotransmitter release \>\> inhibits release of **GABA** and **glycine** from the neurons (esp. in the Renshaw cells of the spinal cord) - Clinical effects \>\> **Spastic paralysis** \>\> Risus sardonicus \>\> Lock-jaw
79
What toxin is secreted by *Clostridium botulinum*, and what is its mechanism of action? What are its clinical effects?
- Botulinum toxin - Cleaves SNARES that are required for neurotransmitter release \>\> prevents release of **ACh** at neuromuscular junctions mainly - Clinical effects: **flaccid paralysis**
80
What are the exotoxins produced by *Streptococcus pyogenes*?
1. Streptolysin O: oxygen labile 2. Streptolysin S: oxygen stable 3. Erythrogenic/pyrogenic toxins A, B and C (superantigens) \>\> Scarlet fever \>\> Streptococcal toxic shock syndrome
81
What organism causes pseudo-appendicitis?
Yersinia enterocolitica
82
What are the 3 components of anthrax toxin?
- Edema factor - Lethal factor - Protective antigen
83
Name 7 bacteria that produce enterotoxins (exotoxins that causes gut electrolyte and water imbalances leading to diarrhea).
1. Staphylococcus aureus 2. Shigella species 3. Enterohemorrhagic E. Coli (EHEC) -- O157:H7 4. Enterotoxigenic E. Coli (ETEC) 5. Vibrio cholerae 6. Yersinia enterocolitica 7. Clostridium perfringens, Clostridium difficile
84
What is the mechanism of resistance in MRSA?
Altered **penicillin-binding protein**
85
What bacterium is known to produce large golden colonies?
Staphylococcus aureus
86
What bacterium is known to produce blue-green pigments?
Pseudomonas aeruginosa
87
What bacterium is known to produce yellow sulfur granules?
Actinomyces israelii \>\> Anaerobic \>\> Not acid-fast \>\> Gram-positive branching filaments
88
What bacterium is known to produce red pigments?
Serratia marcescens
89
What is the first and second most common cause of uncomplicated urinary tract infection (UTI) in young women?
1. Escherichia coli 2. Staphylococcus saprophyticus (catalase +ve, coagulase -ve, novobiocin resistant)
90
What vaccinations are available against *Streptococcus pneumoniae*?
- Pneumococcal conjugate vaccine (PCV13): for infants - Pneumococcal polysaccharide vaccine (PPSV23): for adults
91
What are the indications for pneumococcal vaccination for adults?
- Age 65 years of above - Age 2-64 years with chronic illness - Smoker - Asthmatic - Disease that decreases immune response \>\> Leukemia \>\> Lymphoma \>\> Renal failure \>\> HIV infection \>\> Asplenia - Medication that decreases immune response \>\> Steroids \>\> Chemotherapy \>\> Radiation therapy
92
What virulence factor does *Staphylococcus aureus* have other than exotoxins?
**Protein A** ## Footnote - Binds to Fc-IgG - Inhibits complement activation and thus disrupts opsonization - Disrupts phagocytosis
93
What important virulence factors do *Streptococcus pneumoniae* have?
- **Capsule** \>\> There is no virulence if the pneumococcus has no capsule - **IgA protease** \>\> IgA protects _mucosal surfaces_ from bacterial infection \>\> IgA protease cleaves IgA, providing a survival advantage for the pneumococci that is trying to colonize the respiratory mucosae
94
What are the classical presenting features for pneumococcus pneumonia?
- Sudden onset of chills - Lobar consolidation - "Rusty colour" sputum
95
What infections does *Streptococcus pneumoniae* usually cause?
**MOPS** ## Footnote - **M**eningitis - **O**titis media (especially in children) - **P**neumonia - **S**inusitis
96
What are some classes of Viridans Streptococcus?
- Strep. mutans - Strep. salivarius - Strep. anginosus - Strep. mitis - Strep. sanguinis
97
What types of infections/diseases can *Streptococcus pyogenes* cause?
_Pyogenic diseases_ - Pharyngitis - Cellulitis/impetigo - Systemic infections: pneumonia, bacteremia, necrotizing fasciitis _Toxin-mediated diseases_ - Streptococcal toxic shock syndrome - Necrotizing fasciitis _Immunological diseases_ - Rheumatic fever (following strep throat) - Acute post-streptococcal glomerulonephritis (following either pharyngitis or skin infection)
98
What is the diagnostic criteria for rheumatic fever?
**Jones Criteria** \>\> 2 major criteria OR 1 major criterium plus 2 minor criteria ## Footnote _Major criteria_ - **J**oints: polyarthritis - **\<3:** pancarditis (endo/myo/peri) - **N**odules: subcutaneous/Aschoff nodules - **E**rythema marginatum - **S**ydenham chorea _Minor criteria_ - Fever - Arthralgia - Elevated ESR or CRP - Prolonged PR interval on ECG
99
What are some clinical features for Scarlet fever?
- Scarlet sandpaper-like rash - Strawberry tongue - Circumoral pallor
100
What infections can Group B streptococcus (*Streptococcus agalactiae*)?
_Babies/Neonates_ - Pneumonia - Meningitis - Sepsis _Pregnant Women_ - Asymptomatic bacteruria - Urinary tract infection - Post-partum endometritis - Bacteremia _Non-Pregnant Women_ - Bacteremia - Skin and soft tissue infections
101
Name the three most common organisms causing neonatal sepsis.
- Group B streptococcus - *Escherichia coli* - *Listeria monocytogenes*
102
Where are Viridians streptococci usually found?
Normal flora of the **oropharynx**
103
Where is *Streptococcus agalactiae* usually found?
Normal flora of the **vagina** in 25% of women \>\> Asymptomatic carriers
104
Where are enterococci usually found?
Normal **colonic** flora
105
What infections do enterococci usually cause?
- Urinary tract infections - Biliary tract infections - Subacute bacterial endocarditis
106
How does the Lancefield grouping classify streptococci?
By the differences in the **C carbohydrate** on the bacterial cell wall
107
What condition is *Streptococcus bovis* associated with?
**COLON CANCER** \>\> Bacteremia \>\> Subacute endocarditis
108
What organisms are most commonly implicated in subacute endocarditis?
- Viridans streptococci - Enterococci - Streptococcus bovis - Staphylococcus epidermidis (coagulase-negative staphylococcus) - **HACEK** organisms \>\> **H**aemophilus \>\> **A**ctinobacillus \>\> **C**ardiobacterium \>\> **E**ikenella \>\> **K**ingella
109
What are some clinical manifestations of *Corynebacterium diphtheriae* infection?
- Pseudomembranous pharyngitis with grayish-white membraneous exudate - Lymphadenopathy - Myocarditis - Arrhythmias
110
How does one diagnose *Corynebacterium diphtheriae* infection?
- Culture of gram-positive **club-shaped** rods with **metachromatic** (blue/red) granules - **Elek test** for diphtheria toxin - Black colonies on cystine-tellurite agar
111
What is the capsule of *Bacillus anthracis* made of?
**D-glutamate** \>\> B. anthracis is the only bacterium with polypeptide capsule
112
Name the obligate anaerobes.
Anaerobes **C**an't **B**reathe **A**ir. ## Footnote - **C**lostridium - **B**acteroides - **A**ctinomyces \>\> Treat with _metronidazole_ and/or _clindamycin_
113
Name the obligate aerobes.
**N**agging **P**ests **M**ust **B**reathe. ## Footnote - **N**ocardia - **P**seudomonas aeruginosa - **M**ycobacterium - **B**acillus: actually a facultative anaerobe....
114
What are the clinical manifestations of infection with *Bacillus anthracis*?
_Cutaneous anthrax_ - Boil-like papule \>\> Ulcer with **black eschar** -- **PAINLESS** with necrotic centre - Uncommonly progresses to bacteremia and death _Inhalation/Pulmonary anthrax_ - Flu-like symptoms - Fever - Pulmonary hemorrhage - Mediastinitis - Shock \>\> *Mediastinal widening on CXR* \>\> *Woolsorter's disease*
115
What are the clinical features of tetanus infection?
- Trismus (Lock-jaw) - Risus sardonicus - Spastic paralysis
116
Which populations does *Listeria monocytogenes* mainly affect?
- Infants - Elderly - Immunocompromised - Pregnant women
117
What infections does *Listeria monocytogenes* mainly cause?
_Pregnant women_ - Amionitis - Septicaemia - Spontaneous abortions _Neonates/Infants_ - Granulomatous infantiseptica - Neonatal meningitis _Elderly_ - Meningitis _Healthy individuals_ - Gastroenteritis - Usually self-limiting **\>\> Listeria is the only gram-positive organism that produces LPS.**
118
What are the microscopic characteristics of *Listeria monocytogenes*?
- Facultative intracellular microbe - Taken up by monocytes - Rocket tails - **Tumbling motility**
119
Which antibiotic can be used to treat *Listeria monocytogenes*?
Ampicillin
120
Which antibiotic can be used to treat *Actinomyces*?
Penicillin
121
Which antibiotic can be used to treat *Nocardia*?
Sulfonamides
122
What is the most common cause of meningitis?
Streptococcus pneumoniae
123
What is the most common cause of osteomyelitis?
Staphylococcus aureus
124
Name the gram-negative cocci.
- Neisseria meningitidis (maltose fermenter) - Neisseria gonorrhoeae (maltose non-fermenter) - Morexella catarrhalis
125
Name the gram-negative coccoid rods.
- Haemophilus influenzae - Bordetella pertussis - Pasteurella - Brucella
126
Name the gram-negative lactose fermenter rods.
_Fast fermenters_ - Escherichia coli - Klebsiella - Enterobacter _Slow fermenters_ - Citrobacter - Serratia
127
Name the gram-negative lactose nonfermenting rods.
_Oxidase positive_ - Pseudomonas _Oxidase negative_ - Shigella - Salmonella - Proteus
128
Name the gram-negative curved bacteria.
- Campylobacter jejuni \>\> Grows in 42oC \>\> Predisposes to Guillain-Barre syndrome - Vibrio cholerae \>\> Grows in alkaline medium \>\> Comma-shaped ## Footnote **These are oxidase positive.**
129
What infections can *Neisseria gonorrhoeae* cause?
- Urethritis - Sexually transmitted infection - Pelvic inflammatory disease - Septic arthritis - Fitz-Hugh-Curtis syndrome
130
What infections can *Neisseria meningitidis* cause?
- Meningitis - Meningococcemia - Waterhouse-Friderichsen syndrome (adrenal hemorrhage)
131
What drugs are used to prophylaxis against *Neisseria meningitidis*?
- Rifampicin - Ciprofloxacin - Ceftriaxone
132
What is the treatment for *Neisseria gonorrhoeae* infection?
- Ceftriaxone - Azithromycin/doxycycline for *Chlamydia trachomatis* co-infection
133
What is the treatment for *Neisseria meningitidis* infection?
- Ceftriaxone - Penicillin G \>\> Immediate and empirical treatment! ---- NEVER WAIT FOR CULTURE
134
What infections does *Haemophilus influenzae* usually cause?
**EMOP** ## Footnote - **E**piglottitis - **M**eningitis - **O**titis externa - **P**neumonia
135
Which culture medium is used for *Haemophilus influenzae*?
Chocolate agar with **Factor V** and **Factor X**
136
What is the treatment for *Haemophilus influenzae* infection?
_Mucosal infections_ - Amoxicillin - +/- Clavulanic acid _Meningitis_ - Ceftriaxone - **Rifampicin prophylaxis for close contacts**
137
Which culture medium and stain is used for *Legionella pneumophilus*?
- Stain: **silver** stain - Culture medium: **charcoal** **yeast extract medium** with **iron** and **cysteine**
138
What is the mode of transmission of *Legionella pneumophila*?
- Aerosol transmission - NOT person-to-person
139
What are the clinical manifestations of *Legionella pneumophila* infections?
_Legionnaire's disease_ - Fever - Severe pneumonia - GI symptoms - CNS symptoms _Pontiac fever_ - Mild flu-like syndrome
140
What infections does *Pseudomonas aeruginosa* usually cause?
**PSEUDO**monas ## Footnote - **P**neumonia - **S**epsis - Otitis **E**xterna - **U**rinary tract infection - **D**iabetic **O**steomyelitis - Wound and burn infections - Hot tub folliculitis - Ecthyma gangrenosum: rapidly progressive necrotic cutaneous lesions
141
What is the treatment for *Pseudomonas aeruginosa*?
- Aminoglycoside - Fluoroquinolones - Anti-pseudomonal penicillins: piperacillin, ticarcillin - Anti-pseudomonal cephalosporins: cefepime, ceftazadime, cefoperazone - Imipenem, meropenem
142
What is *Helicobacter pylori* a risk factor for?
- Peptic ulcer disease - Gastric adenocarcinoma - Lymphoma
143
What microbiological tests help identify *Helicobacter pylori*?
- Gram-negative curved rod - **Urease +** - Catalase + - Oxidase +
144
What is the treatment for *Helicobacter pylori* infection?
**Triple therapy** \>\> Proton pump inhibitor \>\> Clarithromycin \>\> Amoxicillin OR Metronidazole **Quadruple therapy** \>\> Proton pump inhibitor \>\> Bismuth \>\> Metronidazole \>\> Tetracycline
145
What is the most common cause of travellers' diarrhea?
Enterotoxigenic *E. coli*
146
What are the features of hemolytic uremic syndrome?
- Hemolytic anemia - Thrombocytopenia - Acute renal failure
147
What is the treatment for *Escherichia coli* infections?
- Mainly supportive - Antibiotics \>\> Fluoroquinolones \>\> Azithromycin \>\> TMP-SMX
148
What is the treatment for *Clostridium difficile* infection?
- Metronidazole - Oral vancomycin \>\> Not absorbed systemically \>\> Will not cause nephrotoxicity
149
What are some important microbiological differences between *Salmonella* and *Shigella*?
- Salmonella has flagella; Shigella doesn't - Salmonella produces **hydrogen sulfide**; Shigella doesn't - Salmonella is found in a lot of animals Shigella is found only in human and primates
150
What are the characteristic features of typhoid fever, and what is the causative organism?
- **Rose spots** on the abdomen - Fever - Headache - Diarrhea - Can remain in the gallbladder and cause a carrier state \>\> *Salmonella typhi* \>\> Found only in humans
151
What is the characteristic clinical finding for *Klebsiella* pneumonia?
**Red current jelly sputum**
152
What infections does *Klebsiella* usually cause?
- Aspiration pneumonia in _diabetics_ and _alcoholics_ - Nosocomial UTI
153
What is the source of infection of *Yersinia enterocolitica*?
- Pet feces (e.g. **puppies**) - Contaminated milk - Contaminated pork
154
What are the clinical manifestations of *Yersinia enterocolitica* infection?
- Bloody diarrhea - Mesenteric adenitis \>\> can mimic Crohn disease or appendicitis
155
What are the bacteria that can cause food poisoning?
_Gram-positive bacteria_ - Staphylococcus aureus (picnics) - Bacillus cereus (reheated rice) - Clostridium perfringens (reheated meat) - Clostridium botulinum (canned food) _Gram-negative bacteria_ - E. coli O157:H7 (burgers) - Salmonella (poulty, meat and eggs) - Vibrio parahemolyticus/vulnificus (seafood)
156
What are the toxins produced by *Clostridium difficile*?
- Toxin A: enterotoxin \>\> diarrhea - Toxin B: cytotoxin \>\> pseudomembranous colitis
157
Which antibiotics are associated with *Clostridium difficile* infection?
- Clindamycin - Ampicillin \>\> Any antibiotic can do it
158
Name the bacteria. - Clue cells - Fishy discharge - Bacterial overgrowth
*Gardnerella vaginalis*
159
What drugs can cause photosensitivity?
**SAT** for a photo ## Footnote - **S**ulfonamides - **A**miodarone - **T**estosterone
160
What are the signs and symptoms of cystitis?
- Dysuria - Frequency - Urgency - Suprapubic pain \>\> WBCs and often RBCs in urine \>\> No casts: need involvement of the kidney for casts
161
What patient populations are at increased risk for urinary tract infections?
- Women (especially pregnant women) - Men with congenital abnormalities \>\> Hypospadias \>\> Epispadias - Vesicoureteral reflux - Elderly men, especially those with enlarged prostates - Any condition that causes stasis of urine - Diabetics
162
What are the signs and symptoms of pyelonephritis?
- Fever - Chills - Flank pain - Hematuria - WBC casts: WBCs in the renal tubules and compressed \>\> moulded in the tubules to form casts
163
How does one diagnose urinary tract infections?
- History: women with dysuria and frequency without vaginal discharge – 90% UTI - Leukocyte esterase test \>\> Positive LE indicates inflammation in the urinary tract (not only specific to UTIs) - Nitrite test \>\> Detects the presence of Enterobacteriaceae \>\> Can be negative in the presence of UTI if caused by other organisms
164
What are the common causative organisms for UTIs?
1. Escherichia coli (80% of all UTIs) 2. Staphylococcus saprophyticus (10-15% of all UTIs) 3. Klebsiella pneumoniae 4. Proteus mirabilis/Proteus vulgarus \>\> Enterobacter cloacae \>\> Serratia marcescens \>\> Pseudomonas **KEEPPSS** - **K**lebsiella pneumonia - **E**scherichia coli - **E**nterobacter cloacae - **P**roteus mirabilis/Proteus vulgarus - **P**seudomonas aeruginosa - **S**taphylococcus saprophyticus - **S**erratia marcesens
165
What condition is associated with *Proteus* infection of the urinary tract?
Struvite/staghorn/ammonium-magnesium-phosphate renal stones
166
What antibiotics are commonly used to treat urinary tract infections?
- SMP-TMX (sulfonamides) - Aminopenicillins - Fluoroquinolones - Nitrofurantoin
167
What is the mechanism of action of sulfonamides?
- Competitive inhibitor of **dihydropteroate synthase** - Inhibits folate production - Bacteria cannot absorb folate from the external environment - Bacteria must make their own folate acid
168
What organisms do sulfonamides cover?
- Gram negatives - Gram positives - *Nocardia* - *Chlamydia* - Usually used for UTI - Also used for skin infections
169
What are the common side effects of sulfonamides?
- Hypersensitivity (sulfa allergy) - Hemolysis in patients with G6PD deficiency - Nephrotoxicity: tubulointerstitial nephritis - Photosensitivity - Stevens-Johnson syndrome - Kernicterus from in utero exposure - Drug interaction: displacement of drugs (e.g. warfarin) from albumin
170
What are the mechanisms of resistance of bacteria against sulfonamides?
- Decreased drug uptake - Altered target enzyme (dihydropteroate synthase) - Increased PABA synthesis
171
What drugs can cause Stevens-Johnson syndrome?
- Penicillins - Sulfa drugs - Seizure drugs \>\> Carbamazepine \>\> Phenyotoin \>\> Ethosuximide \>\> Lamotrigine \>\> Phenobarbital - Allopurinol
172
What is the mechanism of action of trimethoprim?
- Inhibits **dihydrofolate reductase** - Often used in combination with sulfamethoxazole - Inhibits folate synthesis
173
What are the indications for use of TMP-SMX?
- Urinary tract infections - Prophylaxis in recurrent UTIs - Shigella - Salmonella - Treatment and prophylaxis for *Pneumocystis jirovecii* pneumonia (PCP) - Prophlaxis for toxoplasmosis
174
What the side effects of trimethoprim?
Conditions associated with low folate levels - Megaloblastic anemia - Leukopenia - Granulocytopenia
175
What is the mechanism of action for fluoroquinolones?
Inhibits **DNA gyrase** and **topoisomerase IV**
176
What drugs should be avoided when taking fluoroquinolones?
- Antacids - Any supplements containing: \>\> Calcium \>\> Magnesium \>\> Iron
177
What are the main indications for fluoroquinolone use?
- Gram-negative infections of the urinary and gastrointestinal tract - *Pseudomonas* infections - *Neisseria* infections - Some gram-positive infections, especially for later generations (e.g. levofloxacin)
178
What are the side effects of fluoroquinolones?
- GI upsets - Headache - Dizziness - Superinfections - **Tendonitis** (Achilles tendon) and **tendon rupture** - Leg cramps and myalgias - Prolonged QT interval \>\> _Contraindicated in pregnant women, nursing mothers and children under 18 years due to possible damage to cartilage_ \>\> The only exception to use of FQ in children is in recurrent lung infections in **cystic fibrosis**
179
What is the mechanism of resistance against fluoroquinolones?
- Chromosomal-encoded mutations of DNA gyrase - Plasmid-encoded resistance - Efflux pumps
180
What is the mechanism of action of nitrofurantoin?
Inactivates bacterial ribosomes \>\> Reduced by bacterial proteins to a reactive intermediate
181
What is the indication for nitrofurantoin use?
Mild UTI: usually cystitis caused by *E. coli* and *S. saprophyticus* \>\> NEVER pyelonephritis \>\> NEVER *Proteus* infections
182
What is the mechanism of action of metronidazole?
Forms free radial toxic metabolics \>\> Bactericidal \>\> Anti-protozoal
183
What are the indications for metronidazole use?
**GET GAP** on the *Metro*. ## Footnote - **G**iardia lamblia - **E**ntamoeba histolytica etc. - **T**richomonas vaginalis etc. - **G**ardneralla vaginalis - **A**naerobes: *Clostridium*, *Bacteroides* - H. **P**ylori
184
What are the side effects of metronidazole?
- **Disulfuram-like reaction** - Headaches - Metallic taste
185
What are the drugs that can cause a disulfuram-like reaction if taken with alcohol?
**PM PMT** in **S**in**G**apore ## Footnote - **P**rocarbazine - **M**etronidazole - Cefo**p**erazone, cefa**m**andole and cefo**t**etan - First generation **S**ulfonylureas - **G**riseofulvin
186
What drugs are used to treat anaerobic infections?
- Below the diaphragm: metronidazole - Above the diaphragm: clindamycin
187
Name the three spirochetes.
**BLT** ## Footnote - **B**orrelia burgdoferi - **L**eptospira interrogans - **T**reponema
188
What is the characteristic shape of *Leptospira interrogans*, and what is the classic origin of infection?
- **Question-mark shape** - Contact with contaminated water of **animal urine**
189
What are the clinical manifestations of *Leptospira* infections?
_Leptospirosis_ - Early phase: flu-like symptoms - Asympatomatic phase - Later phase: jaundice from liver damage, renal failure, meningitis and conjuntival suffusion with photophobic * *_Weil disease_** - Jaundice - Azotemia - Fever - Hemorrhage - Anemia
190
What is the causative organism of Lyme disease? Where in the U.S. is it most commonly found?
*Borrelia burgdoferi* \>\> Most commonly found in _northeastern_ United States
191
What is the vector for *Borrelia burgdoferi*?
Ixodes ticks (also vector for *Babesia*) Natural reservoir: mouse
192
What are the symptoms of Lyme disease?
_Stage 1 symptoms_ - **Erythema chronicum migrans** ("Bull's eye" red rash) - Flu-like symptoms - May have facial nerve palsy _Stage 2 symptoms_ - Cardiac symptoms \>\> AV nodal block \>\> Myopericarditis - Neurological symptoms \>\> Facial nerve palsy (usually bilateral) \>\> Encephalopathy \>\> Polyneuropathy _Stage 3 symptoms_ - Chronic large joint monoarthritis - Migratory polyarthritis - Subactue encephalitis/encephalopathy
193
What is the treatment for Lyme disease?
- Doxycyline - Ceftriaxone
194
What are the symptoms of syphilis?
_Primary syphilis_ - Usually singular/isolated painless **chancre** _Secondary syphilis_ - **Systemic**/disseminated disease - Maculopapular rash involving the **palms and soles** - **Condyloma lata**: warty lesions at moist areas _Tertiary syphilis_ - **Gummas**: chronic granulomas - **Aortitis** of the ascending aorta: tree barking due to vasa vasorum destruction - Neurosyphilis \>\> **Tabes dorsalis** \>\> Argyll Robertson pupil \>\> Charcot joints
195
How does one diagnose syphilis?
- Direct visualization by dark-field microscopy in primary syphilis - Serological testing \>\> Nonspecific: VDRL/RPR \>\> Specific: FTA-ABS
196
What is the treatment for syphilis?
**Penicillin G** \>\> If allergic to penicillin: doxycycline
197
What are the clinical features of congenital syphilis?
- Sabre shins - Saddle nose - Hutchinson teeth - Mulberry molars - CNVIII deafness
198
What conditions are associated with rash involving the palms and soles?
**Kawasaki CARS** ## Footnote - **Kawasaki** disease - **C**oxsackie **A** viral infection - **R**ocky Mountain Spotted Fever - **S**econdary syphilis
199
What are the possible causes of a false positive VDRL test?
**M**issed **P**ositive **VDRL** ## Footnote - **M**alaria - **P**regnancy - **V**iruses: EBV (mono), hepatitis - **D**rugs - **R**heumatic fever and **R**heumatoid arthritis - **L**upus and **L**eprosy
200
Name the zoonotic organism. - Cat-scratch fever - Bacillary angiomatosis
*Bartonella* ## Footnote \>\> Regional lymphadenopathy \>\> Bacillary angiomatosis in immunocompromised (similar to Kaposi sarcoma)
201
Name the zoonotic organism. - Lyme disease - Ixodes ticks
*Borrelia burgdoferi* ## Footnote \>\> Shares *Ixodes* ticks with *Babesia*
202
Name the zoonotic organism. - Recurrent fever - Ticks and lice
*Borrelia recurrentis*
203
Name the zoonotic organism. - Undulant fever - Unpasteurized dairy products
* Brucella* species - - Gram negative coccoid rods
204
Name the zoonotic organism. - Bloody diarrhea - Pets and livestock - Grows in 42oC
*Campylobacter jejuni*
205
Name the zoonotic organism. - Severe pneumonia - Parrots and other birds
*Chlamydia psittaci*
206
Name the zoonotic organism. - Q-fever - Spores from tick feces and cattle placenta
*Coxiella burnetii*
207
Name the zoonotic organism. - Headache, muscle aches and fatigue - Blunts immune system \>\> opportunitistic infections (e.g. Candida) - Lone Star ricks
*Ehrlichia chaffeensis*
208
Name the zoonotic organism. - Tularemia - Deer - Tick bites - Rabbits
*Francisella tularensis*
209
Name the zoonotic organism. - Jaundice - Azotemia - Hemorrhage - Conjunctival suffusion - Animal urine
*Leptospira interrogans*
210
Name the zoonotic organism. - "Glove and stocking" loss of sensation - Leonine facis - Armadillos
*Mycobacterium leprae*
211
Name the zoonotic organism. - Cellulitis - Osteomyelitis - Cat and dog bites
*Pasteurella multocida*
212
Name the zoonotic organism. - Epidemic typhus - Louse
*Rickettsia prowazekii*
213
Name the zoonotic organism. - Rash over the palms and soles - *Dermacentor* ticks
*Rickettsia rickettsii*
214
Name the zoonotic organism. - Endemic typhus - Fleas
*Rickettsia typhi*
215
Name the zoonotic organism. - Bubonic plague - Fleas - Prairie dogs - Rats
*Yersinia pestis*
216
Name the bacterium. - Fishy smell discharge - Bacterial overgrowth - Clue cells
*Gardnerella vaginalis*
217
Name the bacterium. - Fever - Spread by ticks - Rash on palms and soles
Rickettsia rickettsii \>\> Rocky Mountain Spotted Fever
218
Name the bacterium. - Fever - Spread by louse and fleas - Central rash spreading outwards
Rickettsia prowazekii and typhi
219
Name the bacterium. - Infertility - Ectopic pregnancy - Urethritis
*Chlamydia trachomatis*
220
Name the bacterium. - Transmitted by aerosols - Treated with doxycycline or azithromycin - Interstitial pneumonia
* Chlamydophila pneumoniae/Mycoplasma pneumoniae*
221
Name the bacterium. - Spore former - Negative Weil-Felix - Q-fever
*Coxiella burnetii*
222
How does primary TB present?
- Asymptomatic - Fever - Chest pain and cough - Usually CXR is normal - Most common CXR finding if present: hilar lymphadenopathy
223
What is the difference between Ghon focus and Ghon complex?
- Ghon focus: calcified lung scar - Ghon complex: Ghon focus + calcified hilar lymph node
224
What are the possible causes of a positive PPD (purified protein derivative) test?
- Current infection - Past exposure - BCG vaccine
225
What are the possible causes of a negative PPD skin test?
- No infection - Anergy \>\> Steroids \>\> Immunocompromised \>\> Malnutrition \>\> Sarcoidosis
226
How can primary TB in immunosuppressed patients present?
- Significant and potentially lethal lung infection - Severe bactermia - Miliary tuberculosis (multiple organ seeding)
227
How does secondary TB present?
- Reactivation of latent TB - Fibrocaseous cavitary lesions \>\> Cheese-like caseous necrosis - Much more symptomatic than primary TB \>\> Fever \>\> Weight loss \>\> Night sweats \>\> Hemoptysis - Includes **extrapulmonary TB** \>\> CNS lesions: parenchymal tuberculoma, meningitis etc. \>\> Pott's disease \>\> Lymphadenitis \>\> Renal disease \>\> Gi disease \>\> Miliary TB
228
What culture medium is used for MTB culture?
- Lowenstein-Jensen agar - Takes 2-4 weeks to culture - More rapid diagnosis: acid-fast stain on early morning sputum for 3 consecutive days - Interferon Gamma-Release Assay
229
What is the treatment for latent TB?
6-9 months of **isoniazid** (INH)
230
What is the treatment for active primary or secondary TB?
_First two months_ - Rifampin - Isoniazid - Pyrazinamide - Ethambutol _Following four months_ - Rifampin - Isoniazid
231
What patients are at risk for *Mycobacterium kansasii* infections?
- Chronic bronchitis - Emphysema \>\> COPD patients \>\> Causes pulmonary TB-like symptoms
232
Which drug is used for prophylaxis of MAI in AIDS patients? When should one start?
Azithromycin \>\> CD4 count \<50 -- START!
233
What are the clinical manifestations of *Mycobaterium leprae* infection?
_Tuberculoid_ - Few hypoesthetic, hairless skin plaques - High cell-mediated immunity with Th1 cell response _Lepromatous_ - Diffuse skin involvement - Leonine (lion-like) facies - "Glove-and-stocking" sensory loss \>\> repeated trauma \>\> deformity of the digits - Communicable - Low cell-mediated immunity with Th2 cell response
234
What is the source of infection of *Mycobacterium leprae*?
- Person-to-person - **Armadillos** \>\> CANNOT BE GROWN IN VITRO
235
What is the treatment for *Mycobacterium leprae* infection?
_Tuberculoid leprosy_ - 6-12 months - Dapsone + rifampin _Lepromatous leprosy_ - 2-5 yeras - Dapsone + rifampin + clofazimine
236
What is the mechanism of action of isoniazid?
Inhibits synthesis of mycolic acids
237
What are the side effects of isoniazid?
- Hepatotoxicity - Peripheral neuropathy \>\> Prevented by giving B6 (pyridoxine) supplements - Drug-induced lupus
238
What are the 4 Rs for Rifampin?
- **R**NA polymerase inhibitor - **R**amps up cytochrome P450 - **R**ed/orange body fluids - **R**apid resistance if used alone
239
What are the indications for rifampin?
- Treatment of TB - Treatment of leprosy - Prophylaxis against: \>\> Neisseria meningitidis \>\> H. influenzae type B
240
241
What are the side effects of pyrazinamide?
- Hyperuricemia - Hepatotoxicity
242
What is the mechanism of action of ethambutol?
_Decreasing carbohydrate polymerization of mycobacterium cell wall_ by blocking **arabinosyltransferase**
243
What are the side effects of ethambutol?
**OPTIC NEUROPATHY** | (red-green colour blindness -- reversible)
244
What organism is associated with: Rabbit hunters?
Francisella tularensis
245
What organism is associated with: Pet prairie dog?
Yersinia pestis
246
What organism is associated with: Ixodes tick?
- Borrelia burgdoferi - Babesia
247
What organism is associated with: Lymphadenopathy + a new kitten?
Bartonella
248
What organism is associated with: a dog bite?
Pasteurella multocida
249
Which Rickettsial species has properties unique from the other Rickettsial organisms? What are those unqiue properties?
Coxiella burnetii ## Footnote - No vector - Transmitted by aerosolized droplets - Endospore - No rash -- instead causes interstitial pneumonia - Negative Weil-Felix test
250
What are the nonenveloped viruses?
Give a **PAPP** smear and **CPR** to the _naked_ **heppy**. ## Footnote - **P**apillomaviruses - **A**denoviruses - **P**arvoviruses - **P**olyomaviruses - **C**aliciviruses - **P**icornaviruses - **R**eoviruses - **Hep**eviruses
251
What would happen to the Mycobacterium tuberculosis organisms within the first week of infection/after exposure?
Aerosol infection of the lower lung fields \>\> phagocytosis by alveolar macrophages \>\> **sulfatide virulence factor** by M. tuberculosis allows for **intracellular bacterial proliferation** \>\> cell lysis from continuous proliferation \>\> MTB organisms released and infect other macrophages ## Footnote *Eventually antigen-carrying macrophages migrate to the lymph nodes and induce a T-helper lymphocyte response -- **2-4 weeks after exposure***
252
Describe the process of epithelioid transformation of macrophages in M. tuberculosis infection.
**MTB is a facultative intracellular organism that is relatively indigestable** When macrophages ingest something that is relatively indigestable, they _lose their motility_, and _accumulate_ at the site of the injury \>\> transform into epithelioid cells --\> usually in a **chronic granuloma** caused by infection with fungi or MTB
253
Which type of tuberculosis infection are Ghon foci found?
**Primary** tuberculosis infection \>\> granulomatous inflammation sites that are walled off when they are too big to be destroyed
254
What cells are predominantly involved in the eradication of Mycobacterium tuberculosis?
**Cell-mediated Th1-mediated immune response** as immunoglobulins from B-cells are unable to reach the organism; this response occurs **2-4 weeks after exposure** ## Footnote - Th1 cells recruit macrophages and more Th-1 cells - Th2 cells recruit and activate B-cells and inhibit Th-1 cells and are therefore of no help
255
What is the treatment for tuberculoid M. leprae infection?
Localized infection mediated by Th1-cells Rifampin + Dapsone x 6 months
256
What is the treatment for lepromatous M. leprae infection?
Diffuse infection mediated by Th2 cells Dapsone + rifampin + clofazimine x 2-5 years
257
Which organisms are catalase positive?
**PLACESS** ## Footnote - **P**seudomonas - **L**isteria - **A**spergillus - **C**andida - **E**. coli - **S**taphylococcus aureus - **S**erratia \>\> Those with chronic granulomatous disease, which is a X-linked mutation affecting NADPH oxidase, are at increased risk for recurrent infections of these bacteria and fungi ----- nitroblue tetrazolium test negative (neutrophils fail to turn blue) and dihydrorhodamine test abnormal
258
What is the action of NADPH oxidase?
Usually functions within activated phagocytes to produce **reactive oxygen species**, which are then broken down by catalase in catalase-positive organisms
259
What is the action of coagulase?
Activates **prothrombin**, and thus converts fibrinogen to fibrin \>\> fibrin-coating of the organism and thus offers resistance against phagocytosis ## Footnote **Staphylococcus aureus expresses coagulase.**
260
What is lecithinase?
The toxin and major virulence factor of **Clostridium perfringens**, also known as alpha toxin ## Footnote - Has activity of **phospholipase C** - Increases platelet aggregation and adherence molecule expression on leukocytes and endothelial cells - Results in _vaso-occlusion_ and _ischemic necrosis_ of affected tissues
261
What are the capsulated bacteria?
**E**ven **S**ome **P**retty **N**asty **K**illers **H**ave **S**hiny **B**odies ## Footnote - **E**scherichia coli - **S**treptococcus pneumoniae - **P**seudomonas aeruginosa - **N**eisseria meningitidis - **K**lebsiella pneumoniae - **H**aemophilus influenzae type B - **S**almonella typhi - Streptoccocus group **B**
262
What is the action of shiga toxin?
Inactivate **60S **ribosome by removing _adenine_ from _tRNA_
263
Why does no effective immunity develop despite the presence of antibodies in HCV infection?
HCV has six or more genotypes and multtiple subgenotypes ## Footnote - The genetic difference in the encoding of its two **envelope glycoproteins** has led to the development of a **hypervariable region of the envelope glycoprotein** that is especially prone to frequent mutation - There is no proofreading 3' --\> 5' exonuclease activity buil into the virion-encoded RNA polymerase \>\> many mistakes and therefore many mutations - **There are usually several dozen subspecies of hepatitis C virus typically present in the blood of an infected individual at any one time. The production of host antibodies lags behind the production of new mutant strains of HCV and effective immunitty against infection is not conferred.** - **The tremendous antigenic variety of HCV has signifiantly slowed efforts to develop a vaccine against the virus.**
264

USMLE Step 1 (14 decks)

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