Gram + Bacteria

Question 1

Bacillus cereus

Answer 1

fried rice, reheated rice

vomitting w/in few hours of ingesting preformed toxin

resolved w/in 24 hours

Question 2

Chronic granulomatous disease

Answer 2

NADPH oxidase deficiency –> can’t produce reactive oxygen species

H2O2 easily broken down by catalase + bacteria (Staphyococcus)

Susceptible to infections by catalase + organisms

Question 3

S. aureus gastro enteritis

Answer 3

dairy, may, eggs “potato salad”

preformed toxin in food –> rapid onset vomiting, resolves quickly

Question 4

S. aureus protein A

Answer 4

binds human Ig

disrupts opsonization, phagocytosis

Question 5

MRSA infections

Answer 5

Skin infections
rapidly worsening abscess
pneumonia
endocarditis
blood stream infections
bone and joint infections
TSS
scalded skin syndrome
gastroenteritis

Question 6

Draw out gram + algorithm

Answer 6

printed (page 317)

Question 7

Staph epidermidis

Answer 7

prosthetic heart valves, central venous catheters, prosthetic joints
biofilm

Question 8

Staph saprophyticus

Answer 8

UTI in females, young sexually active

Question 9

Strep pneumoniae

Answer 9

gram + diplococci
community acquired pneumonia
bacterial meningitis
OM, sinusitis

sudden onset of chills, lobar consolidation, “rust colored” sputum

–> fulminant septicemia

Has capsule - problem w/ aspenia

Question 10

Vaccines against S. pneumo

Answer 10

Pneumococcal conjugate vaccine - PCV13
-infants and adults

Pneumococcal polysaccharide vaccine - PPSV23
-adults

Adult criteria:
65+
2-64 w/ chronic illness dz or meds that decreases immune response, smokers, asthmatics

Question 11

Streptococcus virulence

Answer 11

capsule

IgA protease - leaves IgA

Question 12

Viridan group streptococci

Answer 12

S. mutans - dental plaque
S. salivarius
S. angiosus
S. mitis
S. sanguinis - dental procedures –> subacute endocarditis w/ turbulent flow heart problems (pre-existing endothelial damage)
-require prophylaxis w/ amoxicillin prior to dental procedures if prosthetic heart valve, hx of endocarditis, congenital heart disease

Question 13

Enterococci

Answer 13

catalase -
gamma hemolysis

Enterococcus faecalis
Enterococcus faecium

normal gut flora

–> endocarditis, UTI
Abx resistant - VRE

Question 14

Strep bovis

Answer 14

Group D strep

S. gallolyticus
S. lutetiensis
S. infantarius
S. pasteuranus

found in gut
Endocarditis, bacteremia

Assoc w/ colon cancer 15-30%

Question 15

Dz caused by group A streptococcus

Answer 15

superficial/deep infections: acute pharyngitis, cellulitis, invasive infections (bacteremia, pneumonia, necrotizing fasciitis)

Immunological illness: acute post-strep GN (d/t molecular mimicry - Ig deposits), rheumatic fever

Toxin mediated: Strep TSS (rapid release of cytokines), necrotizing fasciitis

Question 16

Skin infections caused by both S. pygoenes and S. aureus

Answer 16

Cellulitis - deep skin infection

Impetigo
-superficial skin infection - redness, small vesicles or blisters
vessicles rupture –> yellowish fluid - honey crusted
Usually affects face, nose, mouth, cheeks

Question 17

S. agalactiae (Group B, beta-hemolytic Strep)

Answer 17

Normal vaginal flora in 25% - asx carriers

Pregnant woman:
asx bacteriuria
UTI
Post-partum endometritis
Bacteremia

Nonpregnant:
Bacteremia
skin/soft tissue infections

Infants: colonaized at birth
pneumonia
sepsis
meningitis

Vaginal and rectal swab at 35-37 weeks
if GBS + prophylactic PCN during labor

Question 18

Spore formers

Answer 18

Clostridium tetani - rod w/ blob on end “chicken leg”
Bacillus anthracius
Coxiella burnetti - Q fever

Question 19

Actinomyces israelii

Answer 19

anaerobic
colonize oropharynx and GI tract

cervicofacial infections
- jaw, mandible

sinus tract forms
yellow “sulfur” granules

Question 20

Nocardia

Answer 20

gram + rod, partially acid fast

aerobic
soil, dust, decaying vegetation

oral flora

infections in immunocompromised

• inhalation
• inoculation into skin

Question 21

Q fever

Answer 21

Coxiella burnetti

flu like sx
fever several weeks

aerosols from infected placenta or contaminated fluids on coats of newborn farm animals

Question 22

Clostridium difficile

Answer 22

Spore forming, gram+ rod
obligate anaerobe

Toxin A: enterotoxin - binds brush border of gut
Toxin B: cytotoxin disrupts actin in mucosal cells of intestine
–> pseudomembranous colitis
-diffuse watery D
–> toxic megacolon –> colon performation

Risk: abx use - recent or active clindamycin

Dx: stool toxin assay - PCR or ELISA

Tx:
mild: metronidazole PO or IV - excreted into bowels
Severe: oral vancomycin - not absorbed

Fidaxomicin - recurrent, macrolide
Fecal bacteriotherapy

Question 23

Clostridium tetani

Answer 23

Spore forming, gram+ rod
obligate anaerobe
spores in environment - soil

produce tetanospasmin
–> block release of GABA and glycine –> trismus (lock jaw)

vaccine q10 yrs

Question 24

Clostridium botulinum

Answer 24

Spore forming, gram+ rod
obligate anaerobe
heat labile toxin: inhibits ACh release at NMJ –> flaccid paralysis

Spores in honey –> symmetric weakness in babies

Question 25

Clostridium perfringens

Answer 25

Spore forming, gram+ rod
obligate anaerobe

alpha toxin (phospholipase)

• gas gangrene
• myonecrosis

Enterotoxin - food poisoning

Question 26

Bacillus anthracis

Answer 26

Gram + rod, facultative anaerobe (aerobic but can survive anaerobic conditions)

Anthrax toxin: edema factor, lethal factor, protective antigen

Syndromes:
Alimentary tract anthrax

Cutaneous anthrax (MC):
spores enter skin via wound –> small papules –> large, painless ulcer w/ central necrosis
-eschar - depressed, black
-erythema and edema - surround ulcer d/t toxin production

Inhalation (pulmonary) anthrax: “wool sorters dz”
aerosolized spores phagocytosed –> mediastinal LN
CXR: mediastinal widening
bacteria enter circulation –> widespread infection, sepsis, death

Question 27

Listeria monocytogenes

Answer 27

facultative intracellular organism
unpasturized milk/cheese, contaminated deli meats

enters GI tract –> penetrates mucosa –> monocytes

Cross placenta –> fetal loss, neonatal sepsis

Risk groups: infants, elderly, immunocompromised, pregnant

Question 28

Corynebacterium diphtheriae

Answer 28

Gram + rod w/ protuberances on either end - club like

Diphtheria toxin:

• ADP ribosylator of EF2
• -> damage nerve and heart cells = cardiac arrhythmias, myocarditis

Pseudomembranous pharyngitis

• white patches coalesce –> grayish membrane
• scraping –> profuse bleeding

Can proliferate in respiratory tract –> mucus membrane inflammation –> bull neck

Dx: + culture, txin - PCR or Elek test

Vaccine available

Tx:
erythromycin or PCN
anti toxin
Vaccinate after better - natural infection does NOT induce immunity