Bacteriology Flashcards
Staphylococcus saprophyticus
Gram + Catalase + Coagulase - Urease +
Cocci in clusters
Novobiocin resistent
Normal flora in female genetal tract and perineum
Second most common cause of uncomplicated UTI in female (1st=Ecoli)
Streptococcus pneumoniae
Gram + lancet shaped diplococci Encapsulated (no virulence w/o capsule) Optochin sensitive IgA protease most common cause of MOPS: -meningitis -otitis media (children) -pneumonia - a/w rusty colored sputum -sinusitis sepsis in sickle cell and asplenic pts
Viridans group streptococci
S. mutans & S. mitis
S. sanguinis
Gram + alpha-hemolytic
optochin resistent
Normal flora of oropharynx
S. mutans & S. mitis - dental caries
S. sanguinis - subacute bacterial endocarditis
(dextrans bind fibrin-plt aggregates on damaged heart valves)
Streptococcus pyrogenes (GAS)
Pyogenic
Toxigenic
Immunologic
Gram + beta-hemolytic PYR+*
cocci in chains
Bacitracin sensitive
Hyaluronic acid capsule & M protein inhibit phagocytosis
Ab to M protein - defense but cause RHF
Pyogenic - pharyngitis (–>RHF,GN), cellulitis, impetigo (–>GN), erysipelas
Toxigenic - scarlet fever, toxic shock-like syndrome, necrotizing fascitis
Immunologic - RHF, glomerulonephritis
+ASO titer or anti-DNase B Ab => recent infxn
*pyrrolidonyl arylamidase
Scarlett Fever
GAS
blanching, sandpaper-like body rash
Strawberry toungue
circumoral pallor in the setting of GAS infxn
Streptococcus agalactiae GBS
Gram + Beta-hemolytic PYR+
cocci
Bacitracin resistent
Hippurate test+
produces CAMP factor –> enlarges hemolysis around S.aureus
Colonizes vagina
Causes pneumonia, meningitis & sepsis in Babies
Screen preg. women 35-37wks - PCN ppx
Streptococcus bovis (S bovis biotype 1)
Gram +
cocci
colonizes gut
a/w colon cancer
Streptococcus gallolyticus (S bovis biotype 1) causes bacteremia & subacute endocarditis
Enterococci
(E faecalis, E faecium)
VRE
Gram + Catalase- PYR+ variable hemolysis
cocci
grow in 6.5% NaCl & bile
normal colonic flora that are PCN resistent
=> UTI, biliary tract infxn, subacute endocarditis s/p GI procedures
VRE - important cause of nosocomial infxn
Bacillus anthracis
cutaneous anthrax
pulmonary anthrax
Gram +
spore forming rod
produces anthrax toxin
polypeptide capsule (D-glutamate)
colonies - halo of projections “medusa head” appearance
cutaneous anthrax - uncommon progresses to bacteremia & death
painless papule surrounded by vesicles -> ulcer w/ black eschar, painless, necrotic
Pulmonary anthrax "woolsorter's disease" inhalation of spores => flu like sx => fever, pulm hemorrhage, mediastinitis, shock CXR - widened mediastinum
Bacillus cereus
Gram +
rod
Causes food poisoning:
spores survive cooking rice
warm - germination of spores & enterotoxin formation
emetic type - a/w rice & pasta
2/2 cerulide, preformed toxin
p/w N/V w/in 1-5hr
diarrheal type
p/w NB diarrhea & abd pain w/in 8-18hr
Clostridia w/ exotoxins
G+ spore forming obligate anaerobes
C tetani
tetanospasmin = exotoxin causing tetanus
toxin = protease that cleaves SNARE proteins for NTs
blocks release of inhibitory NTs (GABA, glycine) from Renshaw cells in spinal cord
p/w spastic paralysis
trismus (lockjaw)
risus sardonicus (raised eyebrows + open grin)
opisthotonos (spasms of spinal extensors)
ppx tetanus vaccine
tx antitoxin +/- vaccine booster
abx
diazepam (for mm spams)
wound debridement
C botulinum
Produces heat-labile toxin
toxin inhibits Ach release at NMJ (cleave SNARE)
adults 2/2 ingestion of preformed toxin (bad bottles)
babies 2/2 ingestion of spores (honey) ~floppy baby
p/w 4D’s - Diplopia, Dysarthria, Dysphagia, Dyspnea
Descending paralysis
local botulinum toxin - tx dystonia, achalasia, mm spasm, cosmetic
C perfringens
produces alpha toxin (lecithinase, a phospholipase)
causes hemolysis, myonecrosis/gas gangrene & food poisoning
Myonecrosis - p/w soft tissue crepitus
Food poisoning - spores survive undercooked food & release heat-labile enterotoxin
C difficile
Produces 2 toxins
Toxin A - enterotoxin
binds brush border of gut & alters fluid secretion
Toxin B - cytotoxin
actin depolymerization
Both lead to pseudomembranous colitis + diarrhea
2/2 abx use, ampicillin, clindamycin, a/w PPIs
dx - PCR or antigen detection from stool sample
tx - metronidazole, PO vancomycin, fidaxomicin, fecal microbiota transplant
Corynebacterium diphtheriae
Gram + rod
ABCDEFG
A - ADP-ribosylation (of EF2 via exotoxin)
B - Beta-prophage (encodes exotoxin)
C - cystine-tellurite agar ~ black colonies
D - causes diphtheria*
E - Elek test + for toxin
G - Granules - lab dx with metachromatic granules (blue&red)
*p/w pseudomembranous pharyngitis (grayish white membrane) w/ LAD, myocarditis & arrhythmias
Listeria monocytogens
Gram +
facultative intracellular rod
Tumbling motility in broth
Forms “rocket tails” via actin polymerization
allows intracellular movement & cell-to-cell spread across membranes ~avoid Ab
Grows well in fridge temp (4-10C)
acquired by ingestion of unpasteurized dairy products & cold deli meats
Transplacental or vertical transmission at birth
p/w amnionitis, septicemia, SAB in pregnant women
granulomatosis infantispetica, neonatal meningitis
meningitis in immunocompromised
limited gastroenteritis in nl adult
tx ampicillin
Nocardia vs Actinomyces
Gram + form long branching filaments resembling fungi
Nocardia
Aerobe
acid fast (weak)
Found in soil
immunocompetant -> cutaneous infxn
immunocompromised -> pulm infxn (can mimic TB w/ -PPD)
can spread to CNS
tx - TMP-SMX
Actinomyces
Anaerobe
not acid fast
found in Oral, GI and reproductive tract
forms yellow “sulfur granules”
oral/facial abscesses that drain in sinus tract
a/w dental caries/extraction, facial maxillofacial trauma
can cause PID w/ IUD
tx - PCN
Mycobacteria
all are AFB +
M tuberculosis
p/w fever, night sweats, weight loss, cough, hemoptysis
cold factor creates serpentine cord appearance in virulent strains
activates macrophages (granuloma formation) & induces release of TNF-alpha
sulfatides (surface glycolipids) inhibit phagolysosomal fusion
caseating granulomas w/ central necrosis & langhans giant cell - characteristic of secondary TB
PPD+ current infxn or past exposure
PPD- no infxn, sarcoidosis, HIV infxn (esp low CD4+)
IFN-gamma assay (IGRA) < BCG vaccine (FP)
TB
Primary TB - Ghon complex
hilar nodes + ghon focus (usually mid-lower lobes)
> 90% - healing by fibrosis, calcification, PPD+
=> Secondary TB, reactivation
fibrocaseous cavitary lesion in upper lobe
- -> locally destructive dx
- -> bacteremia & miliary TB
M avium-intracellulare
AIDS - disseminated, non-TB dx
ppx - azithromycin when CD4+<50
often resistent to multiple drugs
M scrofulaceum
cervical lymphadenitis in children
M marinum
hand infection in aquarium handlers
M leprae - Hansen disease
Lepromatous
Tuberculoid
likes cool temp, can’t grow invitro
infects skin & superficial nn (stocking-glove) - loss of sensation
dx - skin bx
Lepromatous
p/w diffusely
