GRAM +

Question 1

Catalase +, Coagulase +

Answer 1

Staphylococcus aureus

Question 2

Catalase +, Coagulase -, Novobiocin sensitive

Answer 2

Staphylococcus epidermis

Question 3

Catalase +, Coagulase -, Novobiocin resistant

Answer 3

Staphylococcus saprophyticus

Question 4

Catalase -, a hemolytic, Optochin sensitive

Answer 4

Streptococcus pneumoniae

Question 5

Catalase -, a hemolytic, Optochin resistant

Answer 5

Streptococcus viridans

Question 6

Catalase -, B hemolytic, Bacitracin sensitive

Answer 6

Streptococcus pyogenes (GAS-Group A Strep)

Question 7

Catalase -, B hemolytic, Bacitracin resistant

Answer 7

Streptococcus agalactiae (GBS-Group B Strep)

Question 8

Catalase -, non-hemolytic, 6.5% NaCl growth

Answer 8

Enterococcus

Question 9

Aerobic
Spore forming
-spores form when nutrients are limited
-Dipiccolonic acid–>pushes H2O out; autoclave with steam

Answer 9

Bacillus spp.

Question 10

Obligate anaerobe (Lack superoxide dismutase)
Spore forming
-spores form when nutrients are limited
-Dipiccolonic acid–>pushes H2O out; autoclave with steam

Answer 10

Clostridium spp.

Question 11

Non-spore forming bacillus

Answer 11

Listeria monocytogenes or Corynebacterium diptheriae

Question 12

Beaded filament, not acid fast, obligate anaerobe, spore forming

Answer 12

Actinomyces israelii

Question 13

Beaded filament, weakly acid fast, obligate aerobe, spore forming

Answer 13

Nocardia asteroides

Question 14

Staphylococcus aureus

Answer 14

Catalase +, Coagulase +
***Mayonnaise

Protein A=antiphagocytic (inhibits Fc-IgG binding)
TSST-1=superantigen causes toxic shock
Exfoliatins=skin sloughing/Scaled Skin Syndrome
Enterotoxins=vomiting/diarrhea

Skin infxn (MSSA, MRSA)
Scaled skin syndrome
Toxic shock syndrome
Food poisoning
Pneumonia
Osteomyelitis
Endocarditis

Question 15

Staphylococcus epidermis

Answer 15

Catalase +, Coagulase -, Novobiocin sensitive

***Intracorporeal devices, catheters, lines, prosthetics, etc. for >3 months

Question 16

Staphylococcus saprophyticus

Answer 16

Catalase +, Coagulase -, Novobiocin resistant
***Honeymoon cystitis–>UTI
(Not an STI but is part of normal vaginal flora, and can cause UTI due to sexual intercourse)

Question 17

Streptococcus pneumoniae

Answer 17

Catalase -, a hemolytic, Optochin sensitive
***Rusty, brown sputum

IgA Protease
Encapsulated (+Quellung reaction)

Pneumonia (in adults and elderly)
Bacterial meningitis in children and elderly
Bacterial otitis media
Bacterial sinusitis

Question 18

Streptococcus viridans

Answer 18

Catalase -, a hemolytic, Optochin resistant
***Infection after dental procedure (normal flora in mouth)

“No No Bug”

• No capsule
• Not soluble in bile
• Not sensitive to optochin

Question 19

Streptococcus pyogenes

Answer 19

Catalase -, B hemolytic, Bacitracin sensitive
Group A Strep
***ASO titers

M protein (prevents C3b binding; cross reactivity causes thematic fever)

**Impetigo
**Bacterial pharyngitis (“strep throat”)
Toxic shock-like syndrome
Erythematous infection
Scarlet fever
Necrotizing fasciitis
**Rheumatic fever–>heart disease
**Acute Poststreptococcal glomerulonephritis

Question 20

Streptococcus agalactiae

Answer 20

Catalase -, B hemolytic, Bacitracin resistant
Group B Strep
***Normal vaginal flora–>think: BABIES

Neonatal meningitis
Neonatal sepsis
Neonatal bacterial pneumonia

Question 21

Enterococcus faecalis/faecium

Answer 21

Catalase -, non-hemolytic, 6.5% NaCl growth
***Bladder cancer pts

Subacute endocarditis in bladder cancer pts or abdominal surgery pts

Question 22

Streptococcus bovis

Answer 22

Catalase -, non-hemolytic, NO growth in 6.5% NaCl
***Colon cancer pts

Sepsis and subacute endocarditis in colon cancer pts

Question 23

Bacillus cereus

Answer 23

Spore forming, aeorobic
Fried Rice Syndrome

Heat Stable toxin–>Vomiting (within 6 hrs)
Heat Labile toxin–>Diarrhea (within 6 hrs)

Very difficult to distinguish Bacillus cereus vs enterotoxin of Staphylococcus aureus

Question 24

Bacillus anthracis

Answer 24

Spore forming, aeorobic

• **Boxcars
• **Hilar lymphadenopathy and mediastinal widening

Polypeptide capsule (unique to this organism)
EF (Edema Factor)=adenylate cyclase–>increase in cAMP–>water homeostasis imbalance
LF (Lethal Factor)=metalloproteinase that kills macrophages
PA (Protective Antigen)=require for EF and LF to function

Cutaneous anthrax: spore contact–>painless ulcer–>black eschar (w/ swelling)–>bacteremia–>death
Pulmonary anthrax: inhalation of spores–>flu-like symptoms–>pulmonary hemorrhage and mediastinitis (hilar lymphadenopathy and mediastinal widening)–>shock/ARDS

Question 25

Clostridium tetani

Answer 25

Obligate anaerobe (Lack superoxide dismutase) Spore forming ***Deep tissue wounds--> ↑contractility/spasms Tennis racket/drumstick shaped Tetanospasmin toxin=inhibits release of INHIBITORY GABA and glycine-->SPASM Presentation: - Trismus (aka Lockjaw) - Facial spasms - Opisthotonus (aka Back arching) - Sympathetic overactivity (fever, sweating, tachycardia, labile HTN)

Question 26

Clostridium botulinum

Answer 26

Obligate anaerobe (Lack superoxide dismutase) Spore forming ***Improper food prep/canned foods…HONEY Heat labile toxin A=inhibits release of EXCITATORY ACh-->PARALYSIS Classic tetrad: - Descending weakness with flaccid paralysis - CNs affected first (bulbar weakness) - No fever - No mental status changes Also causes Floppy Baby Syndrome -Due to anticholinergic symptoms-->constipation (1st), lethargy, difficulty feeding, change in crying pitch of baby

Question 27

Clostridium difficile

Answer 27

Obligate anaerobe (Lack superoxide dismutase) Spore forming ***Antibiotic associated diarrhea (esp. with CLINDAMYCIN and ampicillin, but some other broad spectrum antibiotics) A toxin=Enterotoxin-->Binds to brush border causing diarrhea B toxin=Cytotoxin-->Destroys cytoskeleton causing pseudomembranous colitis Tx: Metronidazole, Vancomycin, poop transplant

Question 28

Clostridium perfringens

Answer 28

Obligate anaerobe (Lack superoxide dismutase) Spore forming Only member of Clostridium spp. that is NON-MOTILE ***Gas gangrene α toxin=Lecithinase-->breaks down cell membranes "Double-zoned" hemolysis on blood agar Gas gangrene/myonecrosis - Red/purple skin that looks like cellulitis - Bullae - Crepitus felt on skin

Question 29

Listeria monocytogenes

Answer 29

Non-spore forming bacillus, motile INTRACELLULAR; still motile using actin to transfer between cells ("actin rockets") LPS endotoxin=can cause fever, shock Neonates-->normally in vagina, so can cross placenta and cause abortions; also, granulomatosis infantiseptica Elderly-->Meningitis

Question 30

Corynebacterium diphtheria

Answer 30

Non-spore forming bacillus, non-motile ***Pseudomembrane on pharynx "Chinese letter" appearance Diphtheria toxin=AB toxin=ADP ribosylation of EF-2-->inhibits protein synthesis + Elek's test Growth of black colonies on potassium tellurite agar Pseudomembrane on pharynx with fever Myocarditis-->EKG changes Polyneuritis-->targets local nerves-->CNs-->laryngeal nerves

Question 31

Actinomyces israelii

Answer 31

Beaded filament, not acid fast, obligate anaerobe, spore forming Normal oral flora, GI tract, and female GU tract-->usually opportunistic or after surgery (or IUDs) ***Yellow sulfur granules Oral/facial abscesses with draining sinuses-->can go on to form GI and lung abscesses

Question 32

Nocardia asteroides

Answer 32

Beaded filament, weakly acid fast, obligate aerobe, spore forming Opportunistic Slowly progressive pneumonia-->abscesses in kidney or brain (encephalitis) [Similar to TB in that it's acid fast, but differentiated due to beaded, filamentous growth]