Bacteriology

Question 0

Gram-positive cocci in clusters
Catalase-positive
Coagulase-negative
Novobiocin-sensitive
Whitish, non-hemolytic colonies on blood agar

Answer 0

Staphylococcus epidermidis

Question 1

Gram-positive cocci in grape-like clusters
B-hemolytic yellow or golden colonies on blood agar
Catalase-positive
Coagulate-positive
Salt-tolerant on mannitol salts agar
“Gold” color is due to pigment staphyloxanthia

Toxin: TOXIC SHOCK SYNDROME TOXIN (TSST-1)

Mechanism: Bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-y and IL-2 –> shock

Manifestation: Toxic shock syndrome: fever, rash, shock; other toxins cause scalded skin syndrome (exfoliative toxin) and food poisoning (enterotoxin)

Answer 1

Staphylococcus aureus

Question 2

Gram-positive cocci in clusters
Catalase-negative
Coagulase-negative
Novobiocin-resistant
Whitish, non-hemolytic colonies on blood agar

Answer 2

Staphylococcus saprophyticus

Question 3

Gram-positive cocci in chains
B-hemolytic
Catalase-negative
Bacitracin-sensitive
Lancefield group A
Positive PYR test

Toxin: STREPTOLYSIN O

Mechanism: Protein that degrades cell membrane

Manifestation: Lyses RBCs; contributes to B-hemolysis; host antibodies against toxin (ASO) used to diagnose rheumatic fever (do not confuse with immune complexes of post streptococcal glomerulonephritis)

Answer 3

Streptococcus pyogenes

Question 4

Gram-positive cocci in chains
B-hemolytic
Catalase-negative
Bacitracin-resistant
Hydrolyze hippurate
CAMP test-positive
Lancefield group B
Grow using LIM broth

Answer 4

Streptococcus agalactiae (group b strep)

Question 5

Gram-positive cocci in chains
Catalase-negative
Gamma (nonhemolytic) colonies
Lancefield group D
Bite and optochin-resistant
Hydrolyzes esculin in bile-esculin agar (BEA)
Positive PYR test
E. Faecalis can grow in 6.5% NaCl
S. Bovis cannot grow in 6.5% NaCl

Answer 5

Enterococcus Faecalis ( group D strep)

Question 6

Aerobic, gram-positive box-car like rods nonmotile
Spore-forming
Medusa head morphology

Answer 6

Bacillus anthracis

Question 7

Aerobic, gram-positive spore-forming rod
Motile
Chinese fried rice syndrome

Answer 7

Bacillus cereus

Question 8

Anaerobic, gram-positive, spore-forming rods

Spore is at one end (terminal spore) so organism looks like a tennis racket

Answer 8

Clostridium tetani

Question 9

Anaerobic, gram-positive, spore-forming rods
Canned goods (bulging)
Honey
Botulinum toxin—> flaccid paralysis

Answer 9

Clostridium botulinum

Question 10

Triad of botulism

Answer 10

1. Symmetric descending flaccid paralysis (with prominent bulbar involvement)
2. Absence of fever
3. Intact sensorium

Question 11

Anaerobic, gram-positive, spore-forming rods
Double hemolysis on blood agar
Growth on egg-yolk agar

Answer 11

Clostridium perfringens

Question 12

Anaerobic, gram-positive, spore-forming rods
Exotoxins in stool detected by cytopathic effect on cultured cells or ELISA
colon
Fecal-oral route
Hospital personnel

Answer 12

Clostridium difficile

Question 13

Nonbloody diarrhea associated with pseudomembranes (yellow-white plaques) on the colonic mucosa
Toxic megacolon can occur

Answer 13

Pseudomembranous colitis

Question 14

Aerobic, non-spore forming, non-motile gram-positive rods
Club or comma-shaped rods arranged in V or L shape
Looks like Chinese characters
Metachromatic granules
Black colonies on tellurite plate
Toxigenicity detected using modified elek test

Answer 14

Corynebacterium diphtheriae

Question 15

Gram-negative “kidney-bean” diplococci
Large polysaccharide capsule
Oxidase-positive colonies on chocolate agar
Ferments maltose and glucose

Answer 15

Neisseria meningitidis

Question 16

Gram-negative “kidney-bean” diplococci
Insignificant capsule
Oxidase-positive colonies on Thayer-Martin medium
Ferment glucose only

Answer 16

Neisseria gonorrhoeae

Question 17

Small gram-negative (coccobacillary rods) rods
Requires factor X (hemin) and V (NAD) for growth (chocolate agar)
Satellite phenomenon around S. Aureus colonies

Answer 17

Haemophilus influenzae

Question 18

Small gram-negative rods

Culture on Bordet-Go agar or Regan-Lowe charcoal medium

Answer 18

Bordetella Pertussis

Question 19

Poorly gram-negative rods visualize with silver stain
Facultative intracellular bacteria
Culture on charcoal yeast extract agar
Rapid urinary antigen test

Answer 19

Legionella pneumophila

Question 20

Facultative gram-negative rods
Lactose-fermenting colonies on EMB or MacConkey’s agar
Green sheen on EMB agar; metallic sheen
TSI agar shows acid slant and acid butt with gas but no H2S
Typing by O and H antigens

Answer 20

Escherichia coli

Question 21

Non-lactose-fermenting, gram-negative rods
Produce no gas from the fermentation of glucose
Do not produce H2S
Nonmotile
Have O antigens
Cultured in XLD medium

Answer 21

Shigella spp

Question 22

Shigella transmission

Answer 22

4Fs
Food
Fingers
Feces
Flies

Question 23

Gram-negative rods

Obligate aerobe

Non-lactose-fermenting

Oxidase-positive

Pyocyanin (blue-green pigment)

Sweet grape-like odor

Grown on Cetrimide agar

Answer 23

Pseudomonas aeruginosa

Question 24

Facultative gram-negative rods Non-lactose-fermenting Urease-positive Swarming motility Alkaline urine Struvite Magnesium-ammonium-phosphate Staghorn calculi

Answer 24

Proteus mirabilis

Question 25

Facultative gram-negative rods with large polysaccharide capsule Extended spectrum beta-lactamase (ESBL) Urease-positive Current jelly sputum Most common cause in alcoholics

Answer 25

Klebsiella pneumoniae

Question 26

Curved gram-negative rods Microaerophilic Urease-positive

Answer 26

Helicobacter pylori

Question 27

Comma-shaped gram-negative rods Microaerophilic Positive oxidase and catalase test Grows well at 42C on Skirrows agar Campy medium (with antibiotics) Gullain-barre syndrome Reiter's syndrome

Answer 27

Campylobacter jejuni

Question 28

Comma-shaped gram-negative rods Motile Oxidase-positive Cultured on thiosulfate citrate bile salts sucrose (TCBS) agar Shooting star motility

Answer 28

Vibrio spp

Question 29

Encapsulated, pleomorphic gram-negative bacillus Bipolar densities (Donovan bodies) look like closed safety pins Small painless papule ulcerates to form beefy red ulcer with velvety surface Pseudobuboe formation

Answer 29

Granuloma inguinale (donovanosis)

Question 30

Gram-negative rods Reservoir: domestic animals Transmission: oro-fecal route

Answer 30

Mesenteric adenitis (pseudo appendicitis)

Question 31

Small gram-negative rod Culture on chocolate agar with heme (factor x) PE: painful genital ulcer

Answer 31

Chancroid

Question 32

Facultative gram-variable rod Clue cells present Positive whiff test (fishy odor) Malodorous vaginal discharge

Answer 32

Bacterial vaginosis

Question 33

Dog reservoir Transmission: dog tick (dermacentor) bite Forms morulae in cytoplasm of monocytes

Answer 33

Ehrlichia chaffeensis

Question 34

Gram-negative rod Normal oral flora of cats Cat-scratch fever in immunocomponent individuals Bacillary angiomatosis in immunocompromised Transmission: cat bite or scratch

Answer 34

Cat-scratch disease

Question 35

Obligate intracellular bacteria Energy parasites that use host ATP Cell wall lacks muramic acid Grown in cycloheximide culture Cytoplasmic inclusions in Giemsa

Answer 35

Chlamydia trachomatis

Question 36

Thin, coiled spirochetes Hook at one or both pointed ends (shepherd's crook) Obligate aerobe Grown on Ellinghausen-McCullough-Johnson-Harris (EMJH) medium or Fletcher's medium

Answer 36

Leptospira interrogans

Question 37

Rapid changes due to programmed rearrangements of bacterial DNA encoding surface proteins Transmitted by human body louse (Pediculus humanus) Diagnostic test of choice is microscopy DOC is tetracycline or erythromycin

Answer 37

Relapsing fever ( borrelia recurrentis)

Question 38

C. Trachomatis types D-K Late-onset (2-4weeks) Striking tachypnea, characteristic paroxysmal cough (staccato cough), absence of fever, and eosinophilia

Answer 38

Neonatal pneumonia

Question 39

C. Trachomatis types L1-L3 Papule or vesicular which ulcerates and leads to suppurative inguinal lymphadenitis (buboes) Positive Frei test

Answer 39

Lymphogranulomq venereum

Question 40

``` C. Trachomatis types D-K Most common cause of STDs Neonatal conjunctivitis Neonatal pneumonia Associated with Reiter's syndrome ```

Answer 40

Genital tract infections

Question 41

Aerobic, acid-fast rods Ziehl-Neelsen Lowenstein-Jensen medium Luciferase assay

Answer 41

Mycobacterium tuberculosis

Question 42

Small gram-negative rods without a capsule Contaminated dairy or direct contact Tx: doxycycline plus rifampicin

Answer 42

Brucellosis (undulating fever)

Question 43

Small gram-negative rods Reservoir: rabbits, deer, and rodents Transmission: ticks, aerosols, contact and ingestion Tx: streptomycin or gentamicin

Answer 43

Tularemia (francisella tularentia)

Question 44

``` Most virulent bacteria Small gram-negative rods with bipolar (safety pin) staining Reservoir: wild rodents Transmission: flea bite, inhalation PE: buboes, cutaneous hemorrhage Treatment: streptomycin and tetracycline ```

Answer 44

Yersinia pestis

Question 45

Short, encapsulated gram-negative rod that exhibits bipolar staining Buttery colonies with musty odor due to indole production Reservoir: cats and dogs Transmission: animal bites Treatment: penicillin G

Answer 45

Pasteurella multocida

Question 46

``` Anaerobic, gram-negative rods Predominant anaerobe of human colon Spreads to blood or peritoneum during bowel trauma, perforation or surgery Synergistic pathogenicity Low with endotoxic activity Foul-smelling discharge Abdominal abscess ```

Answer 46

Bacteroides fragilis