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USMLE Step 1 > Microbiology - Bacteria > Flashcards

Microbiology - Bacteria Flashcards

(126 cards)

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1
Q

Acinetobacter baumannii

A

Gram - coccobaillus

Non-lactose fermenting (non-pink colonies on MacConkey agar)

Can cause nosocomial pneumonia, bacteremia, wound infections, esp with war, UTIs

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2
Q

Actinomyces israelii

A

Gram + rods in filamentous chains

Obligate anaerobe

Molar colonies, yellow sulfur granules → stains purple with H&E (see picture)

a/w poor dentition, lumpy jaw (oral/facial abscesses), pulmonary actinomycosis a/w aspiration

“Israel has yellow sand”

Tx: penicillin

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3
Q

Bacillus anthracis

A

Gram + boxcar rods in chains

Spore-forming

Polypeptide capsule of D-glutamate

EF (edema factor) mimics adenylate cyclase → ↑ cAMP

LF (A toxins) PA (B toxin)

Cutaneous: boil-like lesions with black eschar

Pulmonary: inhales spores → flu-like symptoms, fever, pulmonary hemorrhage, mediastinitis → widened mediastinum, shock

Gastrointestional

Treat with ciprofloxacin

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4
Q

Bacillus cereus

A

Gram + rod

Spore-forming

Beta hemolytic

Causes food-borne illness, endopthalmitis (post-surgical, hematogenous)

Emetic type from preformed cereulide toxin (esp. from reheated rice)

Diarrheal type

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5
Q

Bartonella bacilliformis

A

Gram - rod Sand fly-borne Limited to Andes in Peru Causes Carrion’s disease Phase 1: Oroya fever with hemolytic anemia Phase 2: verruga peruana

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6
Q

Bartonella henselae

A

Gram - rod

Flea-born

Cat reservoir

Causes cat scratch fever or bacillary angiomatosis (biopsy reveals neutrophilic inflammation)

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7
Q

Bartonella quintana

A

Gram - rod Body louse-bore Causes trench fever, bacillary angiomatosis

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8
Q

Best media to grow Neisseria?

A

Thayer-Martin or VPN media

Vancomycin inhibits gram +

Polymyxin inhibits non-Neisseria gram -

Nystatin inhibits fungi

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9
Q

Bordetella pertussis

A

Gram - coccobacilli

Encapsulated

Requires fatty acid for culture (Bordet-Gengou agar or Regan Lowe charcoal with horse blood) → “Bordet for Bordetella”

Pertussis toxin → overactivation of adenylate cyclase increases cAMP by disabling Gi → impaired phagocytosis

Causes pertussis (whooping cough)

DTaP vaccine for children, Tdap for adults

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10
Q

Borrelia bergdoferi

A

Lyme disease

Deer tick (Ixodes)

Mice are natural reservoir

Spirochete Stage 1: erythema migrans (expanding bulls-eye rash), fever, lymphadenitis

Stage 2: annular skin lesions, meningoencephalitis, Bell’s palsy, arthritis, carditis

Stage 3: arthritis, neuropathy, 3rd degree heart block

Treat with doxycycline

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11
Q

Borrelia hermsii

A

Soft-shelled tick Spirochete Endemic relapsing fever

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12
Q

Borrelia recurrentis

A

Spirochete

Transmitted by body louse

Epidemic relapsing fever

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13
Q

Brucella

A

Gram - coccoid rod

Facultative intracellular, lives in RES

Consumption of infected milk or milk products, exposure to cattle, pigs

Causes undulant fever/brucellosis

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14
Q

Campylobacter jejuni

A

Gram - rod (gull-shaped, comma-shaped)

Oxidase +

Grows in 42°C (“Campylobacter likes the campfire”)

Transmitted from puppies, livestock, ingestion of undercooked meat

Intestinal invasion

Causes inflammatory diarrhea, especially in children

Complications include Guillain-Barre syndrome and Reiter’s syndrome (reactive arthritis)

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15
Q

Capnocytophagia canimorsus

A

Gram - rod Dog > cat bite Resistant to TMP/SMX, aminoglycosides

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16
Q

Causes of VDRL false positives:

A

Viruses (mono/EBV, hepatitis)

Drugs

Rheumatic fever

Lupus and leprosy

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17
Q

Chlamydia pneumonia

A

Atypical pneumonia in young adults

Intracellular

Lacks muramic acid in cell wall

Tx: azithromycin or doxycycline

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18
Q

Chlamydia trachomatis

A

Gram - coccus or rod

Obligate intracellular pathogen (elementary bodies [infective part] and reticulate bodies)

Serovars A, B, C cause infectious keratitis (trachoma)

Serovars D-K cause STIs: cervicitis, urethritis with a clear discharge, reactive arthritis, PID, neonatal conjunctivitis (unilateral), neonatal pneumonia

Serovars L1-L3 cause lymphogranuloma venereum –> tender regional lymphadenopathy that ulcerates to form buboes

Diagnose with nucleic acid amplification test

Treat with azithromycin, doxycycline, tetracycline

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19
Q

Chlamydophila psittaci

A

Causes Psittacosis

Transmitted from parrots/birds

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20
Q

Clostridium botulinum

A

Gram + rod

Spore-forming

Obligate anaerobe

Botulinum toxin (pre-formed, heat labile) is a protease that cleaves SNARE proteins and prevents release of acetylcholine at neuromuscular junction

Flaccid paralysis, floppy baby syndrome (honey)

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21
Q

Clostridium difficile

A

Gram + rod

Obligate anaerobe

Spores resistant to heat, alcohol-based antiseptics

Toxin A (enterotoxin) binds to brush border of gut and toxin B (cytotoxin) depolymerizes actin → psueomembranous colitis → diarrhea → toxic megacolon

Risk factor include older age, Caucasian female, recent hospitalization, recent antibiotic use (esp. clindamycin, ampicillin)

Tx: metronidazole, oral vancomycin, fidaxomin, fecal transplant

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22
Q

Clostridium perfringens

A

Gram + rod

Obligate anaerobe

Spore-forming (resistant to heat and alcohol-based antiseptics)

Alpha-toxin/lecithinase/phospholipid C splits phospholipids, hemolyzes RBCs

Myonecrosis (gas gangrene), food poisoning

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23
Q

Clostridium tetani

A

Gram + rod (tennis racket)

Spore-forming

Obligate anaerobe

Tetanospasmin toxin is a protease that cleaves SNARE proteins → prevents release of GABA and glycine → decrease in inhibitory neurotransmitters → increased activation of motor nerves → spastic paralysis, risus sardonicus, trismus (lock jaw)

Toxin travels from wound → motor neuron axons → spinal cord

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24
Q

Corynebacterium diphtheriae

A

Gram + rod arranged in “Chinese letter” clumps

Catalase +

Contains cytoplasmic granules that stain with aniline dyes like methylene blue

Grow on Tellurite agar or Loffler medium

Causative agent of diphtheria (pseudomembrane), myocarditis → arrhythmias, lymphadenopathy

The toxin can be cleaved into a fragment that catalyzes the NAD+ -dependent ADP-ribosylation of elongation factor 2, thereby inhibiting protein synthesis

Treat with horse antitoxin

Prevent with DTaP vaccine (toxoid)

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25
Coxiella burnetii
Gram - rod Obligate intracellular Spore-forming Aerosol Contact with goats, sheep, or cattle Q fever, atypical pneumonia
26
Eikenella corrodens
Gram - rod Anaerobic Human bite wounds Smells like bleach
27
Enteroaggregative E. coli (EAEC)
Gram - rod Oxidase - Glucose fermenter Lactose fermenter → colonies turn pink on MacConkey agar Dauses diarrhea in infants and adults
28
Enterobacteria
Gram - rod Lactose fermenter (fast) a/w endocarditis with abdominal or pelvic surgery
29
Enterococcus faecalis/faecium
Gram + cocci Catalse - Gamma/Non-hemolytic → Group D Salt and bile-tolerant Causes complicated UTI, biliary tract infections, _subacute endocarditis following GI/GU procedures_
30
Enterohemorrhagic E. coli (EHEC)/Shiga Toxin-producing E. coli (STEC)
Gram - rod Oxidase - Glucose fermenter Lactose fermenter → colonies turn pink on MacConkey agar Does not ferment sorbital Causes hemorrhagic colitis, hemolytic uremic syndrome ("H for hold the antibiotics, hamburger, and HUS") Shiga-like toxin inactivates 60S ribosome by removing adenine from rRNA Most common serotype if O157:H7
31
Enteroinvasive E. coli (EIEC)
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Causes bacillary dysentery Invades intestinal mucosa (shigella-like) but does not produce shiga toxin
32
Enteropathogenic E. coli (EPEC)
Gram - rod Oxidase - Glucose fermenter Lactose fermenter → colonies turn pink on MacConkey agar Causes diarrhea in infants ("P for pediatric") Pedestal formation Adheres to apical surface → flattens villi → prevents absorption
33
Enterotoxigenic E. coli (ETEC)
Gram - rod Oxidase - Glucose fermenter Lactose fermenter → colonies turn pink on MacConkey agar Causes watery diarrhea in travelers ("T for traveler") and children LB (heat labile) toxin is cholera toxin-like→ overactivates adenylate cyclase → ↑ cAMP → ↑ Cl- and H20 secretion in gut ST (heat stable) toxin → overactivates guanylate cyclase → ↑ cGMP → ↓ resorption of NaCl and H20 in gut
34
Erhlichia chaffeensis
Gram - Obligate intracellular in hematopoetic cells Lone star tick Human Monocytic Erhlichiosis Cytoplasmic mulberry inclusion in leukocytes (see picture)
35
Escherichia coli
Gram - rod Lactose fermenter → colonies turn pink on MacConkey agar Colonies show green metallic sheen on EMB agar Oxidase - Encapsulated _Most common cause of UTI_ fimbriae → cystitis, pyelonephritis K capsule → pneumonia, neonatal meningitis LPS endotoxin → septic shock
36
Escherichia coli K1
Gram - rod Lactose fermenter Sialic acid capsule Can cause meningitis, bacterimia in newborns
37
For what organisms do you use Sabouraud agar?
Fungi
38
Franciscella tularensis
Gram - coccobacilli Facultative intracellular pathogen lives in macrophages Requires cysteine in grow Acquired via exposure to ticks, rabbits, deer fly Causes tularemia
39
Fusobacterium nucleatum
Gram - rod Anaerobic Causes periodontal disease, pleuropulmonary infection, linked to colorectal cancer
40
Gardnerella vaginalis
Gram variable rod β-hemolytic Elevated in bacterial vaginosis --\> thin, grayish/white discharge and fishy odor with KOH Diagnose with elevated pH (\>4.5), Whiff test, clue cells Treat with metronidazole or clindamycin
41
Group B Streptococci
Gram + cocci Catalase - Beta-hemolytic CAMP test + Bacitracin resistant Common cause of meningitis, bacteremia in newborns
42
HACEK
Haemophilus parainfluenzae, Aggregatibacter acetomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae a/w endocarditis with negative blood cultures
43
Haemophilus ducreyi
Gram - coccobacillus Culture with enriched agar (factors X and V + CO2) Causes _painful_ ulcers (chancroid) and possibly inguinal lymphadenopathy
44
Haemophilus influenzae
Gram - coccobacilli Oxidase + Culture on blood agar requires factors X (hematin, heat stable) and V (NAD+, heat labile) to grow; S. aureua supplements NAD+ Type b (Hib) is encapsulated (polyribose-ribitol phosphate) and causes meningitis in infants, epiglottitis, cellulitis, pneumonia (secondary, COPD) Non-typable/non-encapsulated causes conjuctivitis, otitis media, sinusitis IgA protease cleaves IgA to colonize respiratory mucosa Tx mucosal infections: amoxicillin ± clavulanate Tx meningitis: ceftriaxone; prophylaxsis for close contacts with rifampin Hib vaccine (conjugated)
45
Helicobacter pylori
Gram - spiral rod (comma-shaped) Catalase + Oxidase + Urease + Silver stain Type I carcinogen Causes gastritis, ulcers, adenocarcinoma, and MALT lymphoma Contains urease, VacA, CagA Protective against asthma, active TB, esophageal cancer Dx: urea breath test, fecal antigen test Tx: triple therapy (PPI + clarithromycin + amoxicillin or metronidazole)
46
Hemolytic uremic syndrome
a/w EHEC (shiga-like toxin producing E. coli) S&S: anemia, thrombocytopenia, acute renal failure Toxin damaged endothelium → microthrombi form (↓ platelets) → mechanical hemolysis (schistocytes) + decreased renal blood flow
47
How do superantigens cause toxic shock syndrome?
Toxins (TSST-1 for staph, exotoxin A for strep) bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-γ and IL-2 S&S: fever, rash, shock
48
Klebsiella pneumoniae
Gram - rod Lactose fermenter (fast) → mucoid colonies turn pink on MacConkey agar Encapsulated Urease + _Thick mucoid capsule_ --\> current jelly suputum Pneumonia in malnourished, alcoholics, diabetics, nosocomial UTI
49
Lactobacilli (L. acidophilus)
Gram + rod Converts lactose to lactic acid Normal oral flora that can cause dental caries
50
Legionella pneumophila
Gram - rod, primarily intracellular a/w water aerosols Doesn't gram stain well → silver stain LPS can be detected in a urine sample Culture on charcoal yeast with iron and cysteine Causes high fever + GI symptoms + pneumonia (typical and atypical), _hyponatremia_ Treat with macrolide or quinolone
51
Leptospira interrogans
Transmitted through water infected with animal urine Leptospirosis: acute febrile illness with conjunctival suffusion (erythema without exudate), jaundice, photophobia, renal failure Treat with doxycycline
52
Listeria monocytogenes
Gram + rod Catalase + CAMP test + Beta-hemolytic Facultative intracellular → ActA → "rocket tails" via actin polymerization _Listerolysin O → only gram + organisms to have LPS_ Acquired by ingestion of unpasteurized dairy and deli meats, transplancental and vaginal transmission Cause of meningitis in newborns, amnionitis, spontaneous abortion, gastroenteritis Can grow in the cold Tx meningitis with ampicillin
53
Moraxella catarrhalis
Gram - diplococci Oxidase + Causes conjunctivitis, otitis media, sinusitis
54
Mycobacterium avium-intracellulare
Causes TB-like disease in AIDS When CD4 count \< 50 → MAC prophylaxis with azithromycin
55
Mycobacterium leprae
Acid-fast bacillus Likes cool temperatures so affects skin and nerve of the hands and feet Armadillos serve as reservoir Lepromatous form (diffuse cutaneous, communicable) → Th2 response (- lepromin skin test); treat with dapsone, rifampin, clofazimine for 2-5 years Tuberculoid form → Th1 response (+ lepromin skin test); treat with dapsone and rifampin for 6 months
56
Mycobacterium marinum
Fish tank granuloma
57
Mycobacterium tuberculosis
Gram + like (but won't gram stain) Obligate aerobe Mycolic acid in cell envelope --\> acid fast stain Culture on Lowenstein-Jensen agar Cord factor is a virulence factor that causes the bacteria to grow in chains/serpentine cords and inactivates neutrophils, damages mitochondria, and releases TNF Causes TB (can be latent, reactivated, miliary, disseminated) Characterized by Ghon complex in mid zone of lung (primary infection), caseating granuloma, or secondary infection (cavitary lesion in upper lobes due to high PO2) Can spread hematogenously and effect vertebrae (Pott disease) and cranial nerves Treat with RIPE
58
Mycoplasma genitalium
No cell wall Causes urethritis
59
Mycoplasma hominis
No cell wall Causes endometritis, salpingitis, PID
60
Mycoplasma pneumoniae
No cell wall → no gram stain Grows on Eaton agar (requires cholesterol) Atypical pneumonia in young adults in close quarters; CXR findings worse than clinical appearance _High titer of cold agglutinins (IgM) which can lyse RBCs_ Tx: macrolide, doxycycline, fluoroquinolone
61
Name some obligate anaerobes
Clostridium Bacteroides Actinomyces Obligate anaerobes lack catalase and/or superoxide dismutase and are suseptible to oxidative damage Aminoglycosides are ineffective because they require oxygen to enter into the bacteria
62
Name some obligate anerobes
Nocardia Pseudomonas Mycobacterium tuberculosis
63
Neisseria gonorrheae
Gram - diplococci (often found intracellularly) Oxidase + No capsule Glucose fermenter Maltose non-fermenter IgA protease Causes urethritis, vulvovaginitis (girls, postmenopause), cervicitis (premenopause) with mucupurulent discharge, PID, prostatitis, epididymitis, septic arthritis, neonatal conjunctivitis (bilateral) Treat with ceftriaxone + azithromycin No vaccine due to antigenic variation of the pili
64
Neisseria meningiditis
Gram - diplococci Catalase + Oxidase + Encapsulated Maltose fermenter Glucose fermenter Lipooligosaccharide toxin IgA protease contributes to morbidity and mortality Common cause of meningitis in infants, children, and adults, Waterhouse-Friderichsen syndrome (primary acute adrenal insufficiency 2/2 hemorrhagic necrosis), cutaneous manifestations (non-blanching petechial, purpuric, or ecchymotic rash) Long-term sequalae include amputations, hearing loss, skin scarring Tx: ceftriazone or penicillin G; prophylaxis in close contacts with rifampin, ciprofloxacin, or ceftriaxone
65
Nocardia
Gram +, branching Obligate aerobe Urease + Weakly acid fast Causes cavitary pneumonia and brain abscess in immunocompromised and cutaneous infections after trauma in immunocompetent Tx: sulfonamides
66
Orientia tsutsugamushi
Gram - coccobacillus Mite-borne Scrub typhus
67
Pasteurella multicodia
Gram - coccobacillus Cat \> dog bites Causes cellulitis, osteomyelitis _Resistant to clindamycin_ Characteristic mouse-like odor (indole +)
68
Porphyromonas gingivalis
Can cause periodontitis and diabetes, CVD, adverse pregnancy outcomes
69
Propionibacterium acnes
Gram + rod Anaerobic Causes acne, chronic blepharitis, infection of prosthetic devices, endopthalmitis (post-surgical)
70
Proteus mirabilis
Gram - rod Lactose non-fermenter Oxidase - Urease + Motility causes "swarming" on agar Causes UTI, pyelonephritis, kidney stones (MAP/Struvite)
71
Pseudomonas aeruginosa
Gram - rod Lactose non-fermenter Oxidase + Catalse + Obligate aerobe Smells like artificial grape Produces blue-green pigment (pyocyanin) Causes pneumonia in CF patients, nosocomial pneumonia, _hot tub folliculitis_, _otitis externa_, UTIs, burn wounds, infectious keratitis, endophthalmitis (post-traumatic), otitis externa, _osteomyelitis (diabetics and IVDU)_, ecythyma gangrenosum (dermatologic lesions) in immunocompromised/neutropenic Treat with aminoglycoside plus extended-spectrum penicillin (e.g. piperacilin) Exotoxin A inactivates elongation factor 2
72
Rickettsia akari
Gram - coccobacillus Obligate intracellular Mite-borne Rickettsialpox Black eschar mimics anthrax Treat with doxycycline
73
Rickettsia prowazekii
Gram - coccobacillus Obligate intracellular Louse-borne Epidemic typhus fever Tx: doxycycline
74
Rickettsia rickettsii
Gram - coccobacillus Obligate intracellular in endothelial cells Actin polymerization American dog tick (Dermacentor) Rocky Mountain Spotted Fever (rash starts on wrists and ankles and spreads to trunk, palms, and soles) Treat with doxycycline
75
Rickettsia typhi
Gram - coccobacillus Obligate intracellular Flea-borne Murine endemic typhus Tx: doxycycline
76
Salmonella
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Encapsulated (Vi antigen protects from opsonization and phagocytosis) H2S+ Intestinal invasion Causes bloody enterocolitis or bacteremia (immunocompromised), _osteomyelitis in sickle cell disease_
77
Salmonella typhi Salmonella paratyphi
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter H2S+ Intestinal invasion Has flagella ("salmon swim") Causes bloody diarrhea, typhoid fever (_rose spots on the abdomen_, fever, headache, diarrhea) Can result in carrier state if bacteria colonizes the gallbladder
78
Serratia marcrescens
Gram - rod Lactose fermenter (slow) Catalase + Produces a red pigment Can cause UTI (often nosocomial and drug resistant)
79
Shigella dysenteriae
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Intestinal invasion Type 1 causes inflammatory diarrhea and produces shiga toxin → inactivated 60S ribosome by removing adenine from rRNA May cause hemolytic uremic syndrome
80
Shigella flexnerii
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Causes inflammatory diarrhea Most common in developing countries
81
Shigella sonnei
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Causes inflammatory diarrhea Most common in the US
82
Staphylococcus aureus
Gram + cocci Catalase + Coagulase + a/w acute endocarditis in IV drug abusers → large vegetations that destroy the valve, commonly tricuspid Secondary bronchopneumonia, blepharitis, conjuctivitis, endophthalmitis (post-surgical, post-trauma, hematogenous), otitis externa, sinusitis, osteomyelitis in children (most common, adheres to collagen), furuncle Characterized by focal destructiveness, puss, neutrophilic inflammation, and abscess formation Can cause scalded skin syndrome when exofoliative A and B toxins cleave desmoglein 1 Toxic shock syndrome toxin (TSST-1) is a superantigen → toxic shock syndrome Protein A binds Fc region of IgG → prevents opsonization and phagocytosis
83
Staphylococcus epidermidis
Gram + cocci Catalase + Coagulase - Novobiocin sensitive Urease + a/w endocarditis with prosthetic valves, complicated catheter-associated UTI, endophthalmitis (post-surgial), otitis externa Makes biofilm Characterized by focal destructiveness, puss, neutrophilic inflammation, and abscess formation
84
Staphylococcus saprophyticus
Gram + cocci Catalase + Coagulase - Novoiocin resistant Urease + a/w _UTI in young, sexually active females_
85
Streptobacillus moniliformis
Gram - rod, branching Rat bite fever
86
Streptoccocus bovis
Gram + cocci Catalase - Gamma/Non-hemolytic → Group D a/w subacute endocarditis with colorectal cancer
87
Streptococcus agalactiae
Gram + Catalase - Beta-hemolytic → Group B Bacitracin resistant CAMP factor + Hippurate test + Encapsulated Causes meningitis in newborns
88
Streptococcus mutans
Gram + cocci Alpha hemolytic Normal oral flora that can cause dental caries
89
Streptococcus pneumoniae
Gram + diplococci, lancet-shaped Catalase - Alpha-hemolytic Optochin sensitive Bile soluble Encapsulated a/w endocarditis in alcoholics Most common cause of community-acquired pneumonia, meningitis in infants, children, and adults, otitis media, conjuctivitis, sinusitis IgA protease cleaves IgA to colonize respiratory mucosa
90
Streptococcus pyogenes
Gram + cocci in chains Catalase - Beta-hemolytic Group A Bacitracin sensitive PYR + a/w pharyngitis, pyoderma (impetigo, erysipelas, cellulitis, necrotizing fasciitis), _scarlet fever (sandpaper-like rash with fever, sore throat, circumoral pallor, strawberry tongue)_, rheumatic fever/heart disease (M-protein mimicry) Streptolysin O degrades cell membranes, lyses RBCs; anti-streptolysin O used to dx rheumatic fever Exotoxin A (superantigen) → streptococcal toxic shock syndrome
91
Viridians group streptococci
Gram + cocci Catalase - Alpha-hemolytic Optochin resistant Not bile soluble _Synthesize dextrans from sucrose to adhere to tooth enamel and fibrin-platelet aggregates_ Streptococcus sanguinis a/w subacute endocarditis of previously damaged valves → small vegetations that don't destroy the valve Streptococcus mutans a/w dental caries
92
Treponema pallidum
Spirochete Causes syphilis (1° - painless ulcers, 2° - patches, rashes on palms and soles, conylomata lata, 3° - gummas, aortitis, neurosyphilis), congenital syphilis (snuffles, saber shins, saddle nose, CN VIII deafness, Hutchinson teeth, mulberry molars) Diagnose with darkfield microscopy, fluorescent antibody staining, nontreponemal and treponemal serology tests Treat with penicillin G
93
Trichomonas vaginalis
Flagellated protozoan Causes trichomoniasis --\> copious yellow/green, frothy discharge, odor, itching, burning, inflammation Dx: motile trophozoites on wet mount (see picture), strawberry cervix, pH \> 4.5 Tx: metronidazole for patient and sexual partner
94
Ureaplasma urealyticum
No cell wall Urease + Causes urethritis
95
Vibrio cholerae
Gram - rod (comma-shaped) Oxidase + Grows in alkaline media Glucose fermenter Can cause voluminous "rice-water" diarrhea Cholera toxin overactivates adenylate cyclase → ↑ cAMP by permanently activating Gs → ↑ Cl- and water secretion in the gut
96
Vibrio parahemolyticus
Gram - rod Oxidase + Glucose fermenter Can cause secretory diarrhea Commonly transmitted from undercooked seafood (increasing with global warming)
97
Vibrio vulnificus
Wound exposure to shellfish or warm salt/brackish water Can cause hemorrhagic bullae
98
What bacterial diseases are transmitted by body louse?
Trench fever (Bartonella quintana), epidemic typhus (Rickettsia prowazekii), epidemic relapsing fever (Borrelia recurrentis)
99
What bacterial diseases are transmitted by fleas?
Murine endemic typhus (Rickettsia typhi), bubonic plague (Yersinia pestis), cat scratch fever (Bartonella henselae)
100
What bacterial diseases are transmitted by mites?
Scrub typhus (Orientia tsutsugamushu), Rickettsialpox (Rickettsia akari)
101
What bacterial diseases are transmitted by ticks?
Lyme (Borrelia burgdorferi), STARI, endemic relapsing fever (Borrelia hermsii), RMSF (Rickettsia rickettsii), sometimes tularemia (Franciscella tularensis) and Q fever (Coxiella brunetti)
102
What can cause a false negative PPD test?
Steroid use Malnutrition Immunocompromised Sarcoidosis
103
What can cause a positive PPD test?
Current TB infection Past TB exposure BCG vaccination → interferon-gamma release assay more specific (fewer false positives); measures INF-gamma released by T lymphocytes when exposed to Mycobacterium tuberculosis antigens
104
What conjucated vaccines are available?
Conjugated vaccines are made for encapsulated bacteria whereby capsule polysaccharides are joined to a carrier protein to stimulate T cell activation and class switching Available for PCV/Prevnar, Hib, and meningococcal vaccines
105
What CSF findings are consistent with bacterial meningitis?
Gram stain findings Antigen findings ↑ opening pressure ↑ PMNs ↑ protein ↓ glucose
106
What diseases are caused by Ixodes ticks (deer ticks)?
Lyme disease Babesia Anaplamosis
107
What is a Jarisch-Herxheimer reaction?
Flu-like syndrome after starting antibiotics 2/2 killed bacteria releasing pyrogens
108
What is different about the cell membranes/walls of mycoplasma and mycobacteria?
Mycoplasma do not have cell walls, membranes contain _sterols_ Mycobacteria cell walls contain _mycolic acid_ (acid fastness) and a high lipid content
109
What is hemolytic uremic syndrome?
microangiopathic hemolytic anemia, thrombocytopenia, glomerular thrombosis
110
What structures are unique to gram + organisms?
Cell wall made of peptidoglycans Lipoteichoic acid (lipid + teichoic acid) → induces TNF, IL-1
111
What structures are unique to gram - organisms?
Outermembrane contains endotoxins (lipopolysaccharide); Lipid A induces TNF and IL-1
112
Which age groups are most affected by Neisseria meningitidis?
Infants, children, and adults
113
Which age groups are most affected by Streptococcus pneumoniae?
Infants, children, and adults
114
Which bacteria cause meningitis in adults?
Streptococcus pneumoniae Neisseria meningitidis Mycobacteria
115
Which bacteria cause meningitis in children?
Neisseria meningitidis Streptococcus pneumoniae
116
Which bacteria cause meningitis in infants?
Neisseria meningitidis Haemophilus influenzae Streptococcus pneumoniae
117
Which bacteria cause meningitis in newborns?
Group B streptoccoci Escherichia coli Listeria monocytogenes
118
Which orgninisms are acid fast?
Mycobacterium (e.g TB) Nocardia (weakly acid fast)
119
Yersinia enterocolitica
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Transmitted from pet feces, contaminated milk, pork Causes enterocolitis, reiter's syndrome, mesenteric lymphadenitis, extraintestinal infection May mimic Chron's disease or appendicitis ("take yer appendix out")
120
Yersinia pestis
Gram - rod Lactose non-fermenter Oxidase - Flea-borne (rats and prarie dogs are reservoirs) Causes bubonic plague (painful buboes) or pneumonic plague
121
Yersinia pseudotuberculosis
Gram - rod Oxidase - Glucose fermenter Lactose non-fermenter Causes enterocolitis, reiter's syndrome, mesenteric lymphadenitis, extraintestinal infection May mimic appendicitis ("take yer appendix out")
122
Pelvic inflammatory disease (PID)
Causes: chlamydia (subacute) or gonorrhea (acute) S&S: cervical motion tenderness (chandelier sign), purulent cervical discharge, may include salpingitis, endometritis, hydrosalpinx, tubo-ovarian abscess, Fitz-Hugh-Curtis syndrome (ascending infection of the liver capsule with adhesion to the peritoneum)
123
Bacteroides fragilis
Gram - rod Anaerobic Unique surface polysaccharides favor abscess formation Commonly isolated in intraabdominal infections
124
Which bacteria invade the intestinal mucosal causing bloody diarrhea?
Salmonella Shigella Enteroinvasive E. coli (EIEC) Campylobacter jejuni Entamoeba histolytica
125
Bacterial methods of acquiring genes for virulence and antibiotic resistance
Transformation = uptake of exogenous DNA Transduction = bacteriophage transfers DNA Conjugation = one-way transfer of plasmid DNA through sex pilus Spontaneous or induced mutations Transposon = mobile genetic elements that can transfer from plasmids to bacterial chromosome or vice versa
126
Tropheryma whipplei
Gram + PAS + foamy macrophages Causes Whipple disease: malabsorption, cardiac symptoms, arthralgias, neurologic symptoms

USMLE Step 1 (20 decks)

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