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USMLE Step 1 > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Functions of bacterial cell wall

A
  1. Resist osmotic stress
  2. primer for own synthesis
  3. shape
  4. Protection
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2
Q

Encapsulated bacteria

A 
Strep pneumoniae
Klebsiella pneumoniae
H. influenzae
N. meningitidis
Salmonella
Group B strep
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3
Q

Bacterial capsules

A

Composed of glycocalyx (except b. anthracis)

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4
Q

Gram positive bacteria

A

Thick cell wall with lots of PG. Assoc with techoic and lipoteichoic acids

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5
Q

Gram negative bacteria

A

Thin PG layer and outer membrane. LPS.

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6
Q

Phases of bacterial growth

A

Lag, Log, Stationary, Decline

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7
Q

Obligate aerobes

A

Require O2. Nocardia, pseudomonas, mycobacterium tuberculosis, bacillus. (“Nagging pests must breathe”)

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8
Q

Obligate anaerobes

A

Cannot grow in presence of O2. Clostridium, bacteroides, actinomyces. (“Can’t breathe air”)

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9
Q

Microaerophilic

A

Requires very little levels of O2 for growth

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10
Q

Conjugation

A

One-way transfer of DNA from a donor cell to a recipient cell through sex (F) pilus. Donor bacterium must carry F plasmid (F+, male) and other must not (F-, female)

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11
Q

Spores

A

Dehydrated, multicelled structure that allows bacteria to survive when nutrients are limited. Only autoclaving will kill. Only certain gram positive rods can form spores.

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12
Q

Transformation

A

Bacteria take up fragments of naked DNA and incorporate them into their genomes if recipient is sufficiently homologous for recomb to occur

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13
Q

Transduction

A

Genetic transfer mediated by bacteriophages

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14
Q

Pigment producing bacteria

A 
S aureus (yellow)
P aeruginosa (blue-green)
Serratia marcescens (red)
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15
Q

Bacteria that carry IgA proteases

A

S pneumoniae
N meningitidis
N gonorrhoeae
H influenzae

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16
Q

alpha hemolysis

A

Green darkening of blood agar. S pneumoniae, viridans strep

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17
Q

beta-hemolysis

A

Complete clearing of blood agar. S pyogenes, agalactiae, aureus. Listeria.

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18
Q

Gamma-hemolysis

A

no hemolysis. Enterococcus

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19
Q

Endotoxin

A

LPS. Outer cell membrane of gram neg bacteria. Can cause fever and shock

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20
Q

Exotoxin

A

Polypep secreted by bacteria that harm host by altering cellular structure or fn. Very potent and potentially lethal.

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21
Q

Enterotoxins

A

Act on gut.

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22
Q

Bacteria not amenable to Gram staining

A

Mycobacteria. mycoplasma, rickettsia, chlamydia, treponema, legionella

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23
Q

MacConkey agar

A

Inhibits Gram+. Lactose fermenters: red. Non-lactose fermenters: white.

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24
Q

Chocolate agar

A

Good for H influenzae. Contains X, V factors.

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25
Bordet-Gengou medium
Good for B pertussis
26
Bile esculin agar
Good for Group D streptococci
27
Silver stain
Good for Legionella pneumophilia
28
Hemolysis on blood agar
Differentiates streptococci
29
Streptococcus pyogenes
Pyogenic. B hemolysis. Causes wide variety diseases
30
Streptococci
Catalase negative, grm positive
31
Rheumatic fever
Caused by cross rxn of Abs raised against streptococcus bacteria with antigens in heart, causing pancarditis initially and potentially later-onset valvular disease.
32
Streptococcal pharyngitis
Odynophagia, high fever, regional lymphadenopathy, and most notably, erythema and frank white exudate on palatine tonsils. Scarlet fever is a complication from lysogenized pyrogenic exotoxin.
33
Impetigo
Common childhood colonization of upper epidermis. Perioral vesicular/blistered lesions that eventually develop honey-colored crust. Can be caused by streptococcus or S aureus.
34
Necrotizing fasciitis
Rapidly progressive infection of deep subcutaneous tissue. Purple-blue bullae on overlying skin following cellulitis-like picture, overt gangrene, systemic sxs, MOF.
35
Erysipelas
Acute skin infection-erythema, edema, warmth, systemic sxs. Streptococcus or other orgs like s aureus if immunocompromised
36
Cellulitis
Acute skin infection-erythema, edema, warmth, systemic sxs. Streptococcus or other orgs like s aureus if immunocompromised
37
Strep agalactiae
Common cause UTIs in pregnant women, comm cause neonatal infection. Indistinguishable from strep pyogenes on microscopy. B hemolysis. High rate of asymptomatic carriage in pregnant women.
38
Yellow fever
Flavivirus
39
Poliovirus
RNA enterovirus. Acute flaccid paralysis in <1%
40
Cat scratch disease
Bartonella henselae
41
Lyme disease
Borrelia burgdorferi, by Ixodes tick
42
EBV
Assoc with Burkitt lymphoma
43
S saprophyticus
5-20% cystitis
44
K pneumoniae
Community acquired pneumonia or secondary infections in COPD patients Currant-jelly sputum Alcoholics and aspirators at risk
45
WBC casts
Only if in kidney
46
Pyelonephritis
Costovertebral angle tenderness, fever, chills, with or without sxs UTI. In kids, may ascend to kidneys through incompetent ureterovesical sphincters
47
Histoplasma
Can live intracellularly
48
Blastomyces
Big, Broad Based, Budding
49
Mississippi River Basin
Histoplasmosis, blastomycosis
50
Central and S America-fungi
Paracoccidioidomycosis
51
Paracoccidioidomycosis
Captains wheel/Mickey Mouse appearance
52
Atypical pneumonia
Mycoplasma pneumoniae, legionelle pneumoniae, chlamydia pneumoniae
53
IgM cold agglutinin production
Only seens with mycoplasma infection
54
Legionella pneumoniae
Cultured on charcoal yeast extract medium OR SILVER STAIN Gram - Severe community acq pneumonia, mostly affecting elderly with pre-existing lung disease
55
Reticulate bodies
Intracellular form of chlamydia species
56
Progressive multifocal leukoencephalopathy
Immunodef. pts. Caused by JC virus
57
CMV encephalitis
Uncommon except in HIV, homeless
58
Toxoplasmosis
Most comm cause cerebral mass lesions in HIV infected pts. Ring enhancing lesions on head CT. TORCH infection. Cat feces.
59
Rubeola
Measles. Koplik spots (red oral lesions with blue-white centers).
60
Diptheria
membraous pharyngitis
61
Rubella
German measles
62
Roseola
HHV6. V young kids, Rash, high fever
63
Rocky Mtn Spotted Fever
Petechial rash beginning around ankles and wrists
64
Eczema herpeticum
Vesicular rash. Pruritic. HSV-1 with disrupted skin barrier.
65
Impetigo
Honey colored crusting. Itchy btu not painful. S aureus or sometimes S pyogenes
66
P. malariae
72 hr cycle
67
P ovale
24 hr cycle
68
P vivax
24 hr cycle
69
P knowlensi
Macaques
70
Viral meningitis
Normal or raised ICP, high lymphos, normal protein, sugar
71
HPV
Inactivates p53, Rb
72
Influenza
Hemagglutinin and neuraminidase on surface allow absorption and penetration of host cells
73
Antigenic shift
New virus, can cause pandemics
74
Guillan Barre
Assoc with campylobacter jejuni | Symmetrical ascending paralysis
75
Neurocysticercosis
Pork tapeworm. Most comm parasitic infxn CNS worldwide. Brain, muscles, skin, heart.
76
B. Pertussis-stages
Incubation: 7-10 days Catarrhal stage: URTI sxs. Max infectivity Paroxysmal-single deep breath then whooping Convalescent stage: decrease in intensity Macrolides only work in incubation, catarrhal stages.
77
H influenzae
Chocolate agar + factor V, X Does not cause influenza! (But can be post-influenza pneumonia) Hib vaccine covers serotype B Epiglottitis, meningitis, otitis media, pneumonia, eye infections, sinusitis
78
Corynebacterium diptheriae
Loeffler medium
79
N gonorrhoeae
Thayer-Martin medium
80
C botulinum
``` fresh honey (babies). Babies-unable to swallow, general weakness. Heat labile toxins that inhibit ACh release into NMJ. Home-canned or preserved food in adults. ```
81
Exotoxin A
TSS, Scarlet fever
82
Rose thorns
Sporothrix schenkii
83
TORCH infections
``` Diseases transmitted transplacentally and thus tested for at birth. Toxoplasmosis Other: Syphilis Rubella CMV Herpes/HIV ```
84
Congenital rubella
Deafness, cataracts, CV abnormalities (esp PDA)
85
Listeria monocytogenes
Gram +ve bacilli, B hemoysis. Meningitis and sepsis in neonates and immunocompromised Soft cheeses
86
Group B strep
Most comm cause neonatal meningitis
87
Listerosis in immunocomp
Ingestion poorly pasteurized milk, soft cheeses, cole slaw, ready to eat turkey/pork products
88
Sarcoidosis
Lympadenopathy (enlarged, nontender). CXR-bilat hilar lymphadenopathy. Non caseating granulomas. Tx with systemic corticosteroids
89
Malaria
Fever, sweat, chills, myalgia. if jaundiced, most likely falciparum.
90
Test for malaria
Thick and thin blood films (parasites and species), giemsa stained.
91
Hodgkins lymphoma
Reed Sternberg cells (binucleate)
92
Typhoid fever
Enteric fever. High fever unresponsive to paracetamol. Gram neg bacilli. Fever increases in step wise manner til 39-41. Bradycardia, rose spots, 3rd gen cephalosporin
93
E. histolytica
Diarrhea withuot blood or mucus.
94
Erythema nodosum
Tender warm red nodules nuder skin from inflamm adipocytes, Strep, HCV, TB, M. pneumoniae, Yersinia, EBV, coccidioides, AI, sarcoid, preg, cancers....
95
Blackwater fever
Complication of malaria due to hemolysis and release Hb into urine. Freq--> renal failure
96
EBV + ampicillin
maculopapular pattern rash
97
Risus sardonicus
"Sardonic smile". Tetanus
98
Trismus
Decreased jaw opening, oft due to muscle spasms. Tetanus
99
Opisthotonos
State of severe hyperextaneion, spasticity. Tentanus
100
Cholera toxin
Stimulates adenylate cyclase
101
Thayer-Martin agar
X, V factors + abx/antifungals that suppress normal flora in vaginal, rectal, and pharyngeal specimens. Neisseria.
102
Tellurite agar
Corynebacterium. Pos=black
103
LPS
Potent activator of immune syst. Il-1, IL-6, TNF
104
Catalase
Differentiates G+ cocci
105
Coagulase
Differentiates S aureus from other staph
106
Superantigens
Scarlet fever toxin (S pyogenes), TSST-1 (S aureus), staph enterotoxins
107
IgA proteases
``` Cleave IgA (1st line defense against pathogens). Prevents opsonization so not noticed by immune system S. pneum, Neisseria, H. influenzae ```
108
Viridans strep
Ungroupable. alpha hemolyitc, optochin resistant
109
S mutans
Dental caries
110
Strep bovis
Assoc w/ GI malignancies
111
S pneumoniae
#1 cause bacterial pneumonia in adults Pyogenic immune response-highly immunogenic capsule #1 cause meningitis in adults Tx: ceftriaxone and/or vanco
112
S aureus
B hemolysis, producing gold pigment Contains coagulase Scalded skin syndrome, TSS, cellulitis, impetigo, folliculitis, dirty wounds w/ foreign matter, osteomyelitis
113
Osteomyelitis in Sickle cell
Salmonella
114
S epidermis
Novobiocin sensitive Mechanical prostheses, indwelling catheters Often a contaminant
115
C. tetani
anaerobic G+. Neurotoxin prevents release GABA, glycine--sustained contractions, risus sardonicus. Vaccine: TDaP. Immunity fleeting-need boosters.
116
C. perfringens
Gas gangrene. Soil. Necrotizes tissue, blood, vasculature. High mortality.
117
C. diff
Anaerobic. Antibiotic-assoc colitis. Most severe=pseudomembranous colitis.
118
B anthracis
Cutaneous-black eschar Pulm-woolsorters disease. Also GI version.
119
B. cereus
Reheated fried rice. Emetic form and diarrheal forms. Resolve on own.
120
Corynebacterium diphtheriae
G+ rods Metachromatic (red/blue) granules Diphtheria-exudative pharyngitis-dysphagia, fever, malaise. Pseudomembrane on post oropharynx and tonsils that cannot be scraped off (dislodges +1 week) DTaP vaccine
121
Actinomycetes
G+ rods. Fungus like morphology. Nocardia and actinomycetes israelii.
122
Nocardia
Strictly aerobic. Bronchopulm infxns, esp if decreased T cell immunity.
123
Actinomycetes israelii
Anaerobic. Oral/facial abscesses with underlying yellow color (sulfur). Surgical drainage and penicillin/ampicillin.
124
Neisseria
G- cocci. Differentiate gonorrhoeae and meningitidis: N men can ferment maltose.
125
N. meningitidis
Most cases meningitis in adolescents. Meningococcemia: multiorgan disease with small vessel thrombolysis and overwhelming consumptive coagulopathy--petechiae/purpura
126
Waterhouse-Friderichsen syndrome
Fulminant meningococcemia--septic shock and bilat hemorrhagic destruction of adrenal glands.
127
N. gonorrhoeae
``` Opthalmia neonatorum if pass through infected birth canal. Gon=2nd most comm STI. Req's Thayer-Martin media. Males-acute purulent urethritis Females-acute cervicitis or asymptomatic ```
128
PID
Polymicrobial but usually gonococcus and/or C thrachomatis involved. Spreads to inner lady bits causing bad things like ovarian abscess, increased risk ectopic preg, infertility
129
H ducreyi
Causes chancroid (STI). Tender perianal nodule that eventually ulcerates. Inguinal lympahdenopathy.
130
Genital herpes
Multiple painful ulcers
131
Lymphogranulum venereum
STI. Single painless ulcer, but painful lymphadenopathy.
132
Gardnerella vaginalis
Coccobacillary Gram -. | Asymptomatic or bacterial vaginosis.
133
Bacterial vaginosis
``` G. vaginalis and/or other anaerobes. Intense pruritis, fishy odor, and copius frothy secretions when mixed with KOH. Clue cells (=epith surrounded by bacteria) ``` Metronidazole
134
Shigella
``` Gram- rod Fecal-oral route Invasive gastroenteritis-bloody diarrhea +pus, fever, abdo pain Shiga toxin Severe=dysentery ```
135
Salmonella
G- rod Chicken, eggs, dairy S. typhi=typhoid fever (pain mimics appendicitis, splenomegaly, rose spots). Cipro, even for carriers.
136
E. coli
``` G- rod. Infectious diarrhea, HUS #1 cause UTIs #2 cause neonatal meningitis Shiga-like toxin causes enterocyte death EHEC, incl O157:H7 most common in US ```
137
Proteus miribalis
Urease. Comm cause UTIs.
138
V cholerae
Exotoxin (choleragen) increases cAMP | Rice water stools. Oral rehydration. Doxy, TMP-SMX can shorten course.
139
C jejuni
G- rod Undercooked chicken, unpast. milk Single most comm cause invasive diarrhea Assoc with Guillain Barre and reactive arthritis
140
H pylori
G- rod. Duod ulcers, chronic gastritis. Urease enzyme Increases risk gastric adenocarcinoma, gastric lymphoma.
141
Pseudomonas
Opportunistic. *Skin infections in burn patients P. aeruginosa has blue-green tint and sweet grape odor.
142
Yersinia pestis
Plague. Dissem by macrophages. Rats and rodents in rural areas (SW US)-bite or fleas. Bubonic plague-buboes. Pneumonic plague-constit and resp sxs
143
Francisella tularensis
Tularemia. Rabbits. Central plains. | Lesions-bubo formation at site infxn
144
Brucella
``` Cows, goats, pigs. Spread by infected meat, aborted placentas, unpast milk. Intermitt fever (worse in day, better at night). ```
145
Pasteurella multocida
Mouths of cats and dogs. Local wound infx, lymphadenopahty, cellulitis. Doxy or penicillin.
146
Bartonella
B. henselae-Cat scratch fever. Chronic lymphadenitis. Mostly in kids. B quintana-trench fever
147
Mycobacterium tuberculosis
TB. 1/3 world. Caseous granulomas. Ghon complex-perihilar LNs by calcified granuloma. In vertebrae=Pott disease Apices of lungs (high O2) Fever, night sweats, weight loss, hemoptysis Miliary-distal seeding
148
M. leprae
Hansen disease (former: leprosy) Armadillos. Tuberculoid and lepromatous forms.
149
Mycoplasma. pneumoniae
Comm cause atypical pneumonia in young adults.
150
Treponema pallidum
Type of spirochete. SYPHILIS Primary-single nonpainful lesion Tertiary-neurosyph. Argyl-Robertson.
151
Spirochetes
Borrelia, tremponema, leptospira
152
Nonvenereal treponema
Yaws, pinta, bejel. All tx'd with penicillin
153
Borrelia recurrentis
Relapsing fever. Louse. Sudden onset shaking chilld, fever, myalgias, headache, delirium, cough, lethargy, hepatosplenomegaly Penicillin, tetracycline
154
Leptospira interrogans
Aerobic, two flagella. Fecal-oral through contaminated water (puddle jumping) Flu-like, photophobia. Mild-aseptic meningitis. Severe-Weil disease
155
Weil disease
Severe complication leptospirosis. Hemorrhagic vasculitis. High mortality.
156
Dimorphic fungi
Coccidiodes immitis Histoplasma capsulatum Blastomyces dematiditis Paracoccidioides brasiliensis
157
Pseudomonacea
Wound infections in burns patients. Opportunistic. G- rods, oxidase positive, do not ferment lactose..
158
Rocky Mountain Spotted Fever
Rickettsial infection (arthropod vector)
159
Lyme disease
Borrelia burgdoferi Ixodes scapularis tick bite Erythema chronicum migrans and constitutional sxs. Can later cause heart conduction problems
162
Coccidiodes
SW US. Desert rheumatic fever.
163
Herpesviruses
``` HSV-1, HSV-2 ZVZ EBV CMV HHV-6 HHV-8 ```
164
HBV
Blood/sex transmission. Partially double stranded hepadna (DNA) virus. Requires RNA-dependent DNA polymerase. Vaccine is recombinant
165
Adenovirus
ds DNA virus. Febrile pharyngitis, pneumonia, conjunctivitis ("pink eye").
166
Parvovirus
ss DNA. Most important is B19-aplastic crises in sickle cell, "slapped cheeks" (fifth disease)-erythema infectiosum in kids, RBC destruction in fetus leading to hydrops fetalis and death.
167
Papillomavirus
ds DNA. Main disease=HPV. Warts: 1, 2, 6, 11 Cervical cancer: 16, 18 Vaccine recombinant.
168
Polyomavirus
ds DNA. JC virus-progressive multifocal leukoencephalopathy in HIV BK virus-transplant patients, commonly affects kidney
169
Poxvirus
ds DNA. | Smallpox, vaccinia (cowpox), molluscum contagiosum
170
Live attenuated vaccines
MMR, polio (Sabin), typhoid, BCG, chickenpox, yellow fever, smallpox
171
Killed vaccines
Rabies, Influenza, Pertussis, Polio (Salk), HAV
172
Recombinant vaccines
HBV, HPV
173
HSV identification
Tzanck test. Detects multinucleated giant cells.
174
Reoviruses
*Only class of RNA viruses that are ds Colitvirus Rotavirus
175
Picornaviruses
``` HAV Polio Echo Rhino Coxsackie ```
176
Hepevirus
HEV
177
Calicivirus
Norwalk
178
Flavivirus
``` Yellow fever Dengue fever HCV St. Louis encephalitis West Nile virus ``` All are arboviruses except HCV
179
Togaviruses
Rubella Eastern equine encephalitis Western equine encephalitis
180
Retroviruses
HIV-1, HIV-2 HTLV-1 Requires reverse transcriptase
181
Coronavirus
Common cold, SARS
182
Orthomyxoviruses
Influenza
183
Paraorthomyxoviruses
Parainfluenza-croup RSV Measles (Rubeola) Mumps
184
Rhabdovirus
Rabies
185
Filovirus
Ebola/Marburg
186
Bunyavirus
Hanta California encephalitis Sandfly/Rift Valley Fever Crimean-Congo hemorrhagic fever
187
Delta virus
HDV
188
Negative stranded viruses
``` "Always Bring Polymerase Or Fail Replication" Arena Bunya Paramyxo Orthomyxo Filo Rhabdo ```
189
Segmented viruses
``` All RNA. BOAR. Bunya Orthomyxo Arena Reo ```
190
Yellow fever
Aedes mosquito. | High fever, black vomitus, jaundice (hence "yellow")
191
Rotavirus
"ROTA: Right Out The Anus" Most important global cause infantile gastroenteritis.
192
HBeAg
Marker of HBV replication and infectivity.
193
Anti-HBeAg
Antibody. Low transmissability.
194
HBsAg
Have HBV :(
195
Anti-HBcAg
Antibody to HBcAg. IgM=acute infection IgG=chronic disease
196
Anti-HBsAg
Immunity to HBV
197
HIV diagnosis
"Rule out" with ELISA | "Rule in" with Western blot
198
Bugs mimicking appendicitis
Yersinia enterocolitica, C jenuni, non-typhoidal Salmonella. Mimicks by causing mesenteric adenitis.
199
Congenital toxoplasmosis
Chorioretinitis, hydrocephalus, intracranial calcifications
200
Congenital rubella
PDA/pulm artery hypoplasia Cataracts Deafness Possibly "blueberry muffin rash"
201
Congenital CMV
Hearing loss Seizures petechial rash "Blueberry muffin" rash
202
Congenital HIV
Recurrent infections | Chronic diarrhea
203
HSV-2
Termporal encephalitis | Herpetic lesions
204
Congenital syphilis
Often results in stillbirth, hydrops fetalis. If survives: Facial abnormalities-notched teeth, saddle nose, short maxilla Saber shins CN VIII deafness
205
Hand-foot-mouth disease
Coxsackievirus type A
206
Erythema infectiosum
Parvo B19. | "Slapped cheek syndrome"

USMLE Step 1 (15 decks)

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