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USMLE/ Step ONE > MICRO > Flashcards

MICRO Flashcards

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1
Q

What are the GP rods/bacilli?

A 
Clostridium
Bacillus
Corynebacterium
Listeria
Mycobacterium
Gardnerella
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2
Q

What are the branching filamentous bacteria?

How do they gram stain?

A

Actinomyces & Nocardia

Gram positive

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3
Q

Which bacteria does not have a cell wall?

How does it gram stain?

A

Mycoplasma. Does not gram stain!

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4
Q

What is PG of bacteria made of? What enzyme significant to structure

A

Sugar backbone w/ peptide side chains, crosslinked by transpeptidase

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5
Q

Differentiate GP vs GN bug wall structure

A

GP: Lipoteichoic acid, thicker PG layer
GN: LPS/Endotoxin, periplasm, thin PG layer

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6
Q

What induces TNF & IL-1 in GN & GPs?

A

GP: Lipoteichoic acid
GN: Lipid A

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7
Q

What are capsule made of? What is the exception

A

Polysacharide

(EXCEPTION: Bacillus anthracis contains D-glutamate, a Polypeptide)

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8
Q

What structure allows bugs to adhere to foreign substances?

A

Glycocalyx

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9
Q

normal flora for skin?

A

Staph epidermidis

S. aureus, yeasts, & other strep species

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10
Q

normal flora for mouth (oropharynx)?

A

Viridins strep (Strep mutans), Candida, H. influenza (type w/o capsule), Neisseria

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11
Q

normal flora of adult colon?

A

Bacteroides fragilis > E. coli

Fusobacterium, Lactobacillus,Enterococcus faecalis, GN anaerobic rods

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12
Q

normal flora in baby colon? (being breast-fed)

A

Bifidobacterium

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13
Q

normal flora in vagina?

A

Lactobacillus. E. coli, group B strep, Corynebacterium, Candida

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14
Q

MC cause of neonatal meningitis? MC transmission source?

A

Group B strep! During natural delivery, from vagina normal flora

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15
Q

List the 3 main causes of newborn (0-6mon) meningitis

A

1) Group B strep
2) E. coli
3) Listeria

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16
Q

what is polycistronic mRNA and give example? Where is it found?

A

single mRNA can code for several genes. Found in Prokaryotes, NOT Eukaryotes.

Ex; Lac operon in E. coli

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17
Q

How does bacteria replicate?

A

Binary fission asexual

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18
Q

What component of Fungal cell membrane target of drugs (different from bacteria)?

A

Ergosterol

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19
Q

normal flora of body organs?

A

NONE! Sterile, like blood should be

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20
Q

name the one bug that can replicate in stomach?

A

H pylori

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21
Q

virulence factor for E. coli to cause UTI? What type of bugs this found?

A

Pili! How it clings to urethra against urine stream

Pili found in GN bugs

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22
Q

Explain chronic infection by Neisseria?

A

Pili change to avert immune response = antigenic variation

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23
Q

Adherence structure for GP bugs?

A

Teichoic acids

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24
Q

Adhesions are important virulence factor for which toxins?

A

pertussis & hemagglutinins

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25
Which bugs use IgA protease?
Strep pneumo H. influenza type B Neisseria
26
Obligate aerobe w/ a capsule?
Pseuodomonas aeruginosa
27
Fungi w/ a capsule?
Cryptococcus neoformans
28
MC virulence factor of bacterial meningitus?
Capsules! help to cross BBB (very slippery) & evade immune response
29
Anti-phagocytis virulence factors w/ associated bugs
Protein A- S. aureus M protein- GAS Pili- N. gonorrhea
30
What bugs do phase variation?
Trypanosoma brucei rhodesiense & | Trypanosoma brucei gambiense
31
Phase variation in flagella?
Enterobacteriaceae
32
what tests used to detect capsule?
Quelling reaction and Latex particle agglutination
33
Which bugs are intracellular- facultative?
``` Salmonella Neisseria Brucella Listeria Francisella Legionella Yersina Mycobacterium ```
34
Obligate intracellular bugs?
Chlamydia & Rickettsia
35
Describe intracellular mechanisms of TB & Listeria?
TB: (-) phagolysosome fusion | Listeria- leaves phagosome before phagolysosome fusion
36
How does a bug invade a non-phagocytic cell?
Invasins
37
Patient has Chronic Granulomatous Disease. Increased risk of infection by...?
Catalase + bugs! SPACE MaN SaM S. aureus, Pseudomonas, Aspergillus, Candida, E. coli, Mycobcaterium, Nocardia, Serratia marcescens
38
Obligate aerobes ? Fermentation method?
Nocardia TB Pseudomonas aeruginosa Bacillus No fermentation
39
When do you see infection by Pseudomonas aeruginosa?
Diabetes Burn wounds Nosocomial pneumonia CF patients w/ pneumonia
40
Urease + bugs
CHuck norris hates PUNKSS ``` Cryptococcus H. pylori Proteus Ureaplasma Nocardia Klebsiella S. epidermidis S. saprophticus ```
41
Describe how vaccines made for capsular bugs?
Capsules (polysaccharide) are conjugated to a protein (i.e. Prevnar). This promotes Tcell activation and later class switching. If not conjugated, only IgM abs made
42
Type III secretion system? Bugs?
Tunnel from bug to macrophage to inject toxins | E. coli, Salmonella, Yersinia, Chlamydia, Pseudomonas
43
Rheumatic fever example of what HS?
Type 2 | Cross reaction of bacterial-induced Abs w/ tissue Ags (endoderm)
44
Granulomas seen in what type of bugs? What type of HS?
``` Intracellular facultative Type 4 (DTH) ```
45
Virulence factors of TB?
Nothing release. The immune response is what is damaging
46
Which organism can block the bile duct?
Ascaris worm
47
Heat stability of toxins?
Exo are destroyed @ 60C, except enterotoxin by Staph | Endo stable @ 100C for an hour
48
Endo vs Exotoxin: secretion
Exo are secreted, Endo not secreted
49
Toxin vaccination for Endo and Exo
Vaccines for Exotoxins using toxoids | NONE for Endo
50
Which bugs are Beta-hemolytics?
S. aureus, Strep pyogenes, Streptotoccus agalactiae, Listeria monocytogenes
51
Coagulase pos, GP cocci virulence factors? How
``` Protein A- (-) phago & complement fixation TSST Enterotoxin Catalase, Coagulase Exfoliative toxin Alpha-toxin (makes cell pores) ```
52
GP cocci in clusters, catalase (+). | Causes what diseases?
``` Food poisoning- heat stable enterotoxin Toxic Shock syndrome- a super Ag Scalded skin syndrome- exfoliative toxin MRSA (Beta-lactam resist) Acute nacteria; endocarditis Osteomyelitis Pneumonia (nosocomial, post-viral) Surgical infection (MCC) Bone pain + fever in kid (unless Sickle) Impetigo ```
53
S. aureus as normal flora and how transmitted?
Nares & skin touching, sneezing, nose-picking, surgical wounds, food (custards, potato salad, canned meat)
54
Predisposing factors for S. aureus infection
Surgery/wounds. Tampons, CGD, CF
55
How does Toxic shock syndrome present? Mechanism
Mechanism: TSST (a super-Ag) binds to MHCII & TCR--> polyclonal Tcell activation Sx: Fever, shock, desquamation, rash, vomit, end-organ failure
56
Explain skin infections by S.aureus
Exfoliative toxin- cause Scalded skin syndrome & Bullou Impetigo
57
Which GPC, catalase pos bug infects IV catheters and how?
Staph epidermidis via biofilms
58
Strep pneumo MCC of what? | Gram stain look?
Meningitis (6months and older, even old) Otitis media (kids) Pneumonia- rusty colored sputum Sinusitis Gram stain: lancet shaped, GP diplo ("halo" sometimes, due to capsule)
59
Draw GP flowchart. Include cocci, Rods, and branching bugs
pg 127
60
What predisposes to Strep pneumo infection?
``` influenza or measles infection COPD CHF Asplenia and/or HgbS--> septicemia Alcoholics (dont confuse w/ Klebsiella, which in this group) ```
61
Which bugs are alpha hemolytic? How to differentiate among them?
Viridans strep & Strep pneumo | Optichin disk: O VR PS
62
Transmission of GPC, catalase neg, Optochin resistant
normal flora in Oropharynx
63
Viridinas strep diseases and causes
Dental caries & plaque- Strep mutans (Dextrans..) Subacute bacterial endocarditis @ damaged valve plus dental work w/o antibiotics- S. sanguis Fibrin/PLT bind to damaged site, and Viridans binds to fibrin via Dextrans polysach
64
Subacutre endocarditis in colon cancer patient, whats da bug?
Streptococcus bovis
65
Disease of GAS
Pyogenic: phayngitis, cellulitis, impetigo (honey-crusted lesions) Toxigenic- scarlet fever, necrotizing fasciitis, TS-like syndrome Immunologic- rheumatic fever, acute glomerulonephritis
66
How to detect GAS, other than gram stain?
ASO titer Bacitracin sensitive PYR positive
67
JONES criteria, use and define
``` Diagnose Rheumatic fever (Type 2 HS) Joints- polyarthritis O- carditis Nodules- subcutaneous Erythema marginatum Syndenham chorea (involuntary limb movement) ```
68
What diseases caused following a Strep pyogenes infection (sequelae infections)
Phayngitis can cause rheumatic fever and acute glomerulonephritis RF (HS 2): 2 wks after, Abs attack heart (molecular mimicry) AGN (HS 3): Due to M-protein. Also after skin infection
69
Sx of Scarlet fever? Associated bug?
Sx: scarlet rash (sparing face). strawberry/scarlet tongue, scarlet throat. Sandpaper rash (spares hands & soles), desquamation of hands soles GAS
70
How does Strep pyogenes spread?
Streptokinase, Streptococal DNAse, Hyaluronidase
71
Diseases of GBS? Prophylaxis? Tx?
Sepsis, pneomonia, & MCC of Neonatal meningitis: Screen women 35-37wks pregnancy. If +, give intrapartum penicillin or ampicillin (Clindamycin or erythromycin in allergies) Tx: Ampicillin w/ aminoglycoside or cephalosporin
72
Lab testing of GBS
CAMP factor, enlarging hemolysis area by S. aureus Bacitracin resistant Beta hemolytic Hippurate positive
73
Lab presentation of Enterococci
Lancefield group D Variable hemolytic patterns Growth on 6.5% NaCl & bile
74
Diseases of Group D Strep Examples of bugs
Penicillin G resistant cause UTI, biliary tract infection, subacute endocarditis- from procedures, (cystoscopy), from colon, perenium, genitals Enterococcus faecalis & E. faecium

USMLE/ Step ONE (11 decks)

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