Gram + Bacteria Flashcards
Bacillus cereus
fried rice, reheated rice
vomitting w/in few hours of ingesting preformed toxin
resolved w/in 24 hours
Chronic granulomatous disease
NADPH oxidase deficiency –> can’t produce reactive oxygen species
H2O2 easily broken down by catalase + bacteria (Staphyococcus)
Susceptible to infections by catalase + organisms
S. aureus gastro enteritis
dairy, may, eggs “potato salad”
preformed toxin in food –> rapid onset vomiting, resolves quickly
S. aureus protein A
binds human Ig
disrupts opsonization, phagocytosis
MRSA infections
Skin infections rapidly worsening abscess pneumonia endocarditis blood stream infections bone and joint infections TSS scalded skin syndrome gastroenteritis
Draw out gram + algorithm
printed (page 317)
Staph epidermidis
prosthetic heart valves, central venous catheters, prosthetic joints
biofilm
Staph saprophyticus
UTI in females, young sexually active
Strep pneumoniae
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
Vaccines against S. pneumo
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
Streptococcus virulence
capsule
IgA protease - leaves IgA
Viridan group streptococci
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
Enterococci
catalase -
gamma hemolysis
Enterococcus faecalis
Enterococcus faecium
normal gut flora
–> endocarditis, UTI
Abx resistant - VRE
Strep bovis
Group D strep
S. gallolyticus
S. lutetiensis
S. infantarius
S. pasteuranus
found in gut
Endocarditis, bacteremia
Assoc w/ colon cancer 15-30%
Dz caused by group A streptococcus
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
Skin infections caused by both S. pygoenes and S. aureus
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
S. agalactiae (Group B, beta-hemolytic Strep)
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
Spore formers
Clostridium tetani - rod w/ blob on end “chicken leg”
Bacillus anthracius
Coxiella burnetti - Q fever
Actinomyces israelii
anaerobic
colonize oropharynx and GI tract
cervicofacial infections
- jaw, mandible
sinus tract forms
yellow “sulfur” granules
Nocardia
gram + rod, partially acid fast
aerobic
soil, dust, decaying vegetation
oral flora
infections in immunocompromised
- inhalation
- inoculation into skin
Q fever
Coxiella burnetti
flu like sx
fever several weeks
aerosols from infected placenta or contaminated fluids on coats of newborn farm animals
Clostridium difficile
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
Clostridium tetani
Spore forming, gram+ rod
obligate anaerobe
spores in environment - soil
produce tetanospasmin
–> block release of GABA and glycine –> trismus (lock jaw)
vaccine q10 yrs
Clostridium botulinum
Spore forming, gram+ rod
obligate anaerobe
heat labile toxin: inhibits ACh release at NMJ –> flaccid paralysis
Spores in honey –> symmetric weakness in babies
Clostridium perfringens
Spore forming, gram+ rod
obligate anaerobe
alpha toxin (phospholipase)
- gas gangrene
- myonecrosis
Enterotoxin - food poisoning
Bacillus anthracis
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
Listeria monocytogenes
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
Corynebacterium diphtheriae
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
