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Flashcards in Bacteriology Deck (27):
1

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)

2

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

3

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)


4

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

5

Scarlett Fever

GAS

blanching, sandpaper-like body rash
Strawberry toungue
circumoral pallor in the setting of GAS infxn

6

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

7

Streptococcus bovis
(S bovis biotype 1)

Gram +
cocci

colonizes gut
a/w colon cancer

Streptococcus gallolyticus (S bovis biotype 1) causes bacteremia & subacute endocarditis

8

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

9

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

10

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

11

Clostridia w/ exotoxins

G+ spore forming obligate anaerobes

12

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

13

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

14

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

15

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

16

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

17

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

18

Nocardia vs Actinomyces

Gram + form long branching filaments resembling fungi

19

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

20

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

21

Mycobacteria

all are AFB +

22

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)

23

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

24

M avium-intracellulare

AIDS - disseminated, non-TB dx
ppx - azithromycin when CD4+<50
often resistent to multiple drugs

25

M scrofulaceum

cervical lymphadenitis in children

26

M marinum

hand infection in aquarium handlers

27

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