Organism Identification

all staphylococcus spp.

• GPC

• clusters

• catalse positive

• non-fastidious

• SBA most common media

Staphylococcus aureus

• GPC in clusters

• catalase positive

• coagulase positive

• latex agglutination positive (protein A)

• yellow colonies

• often beta hemolytic

• mannitol and DNase positive

• can tolerate NaCl

Coagulase Negaive Staphyloccus (CoNS)

• GPC in clusters

• catalase positive

• coagulase negative

• latex agglutination negative (no protein A)

• white colonies

• gamma hemolytic

• mannitol and DNase negative

Micrococcus spp.

• GPC in tetrads (usually larger than staph)

• catalase positive

• bright yellow colonies

• A-disk sensitive

• gamma hemolytic

all streptococcus spp.

• GPC in chains or pairs (usually oval-shaped)

• catalase negative

• fastidious (needs blood)

• most grow on SBA

• prefers CO2

• can also grow on CNA

• can be gamm, alpha, or beta hemolytic

Streptococcus pyogenes

“group A strep”

• GPC in chains

• catalase negative

• Small, white colonies (translucent)

• large zone of beta hemolysis

• sensitive to A disk

• PYR positive

Streptococcus agalactiae

“Group B strep”

• GPC in chains

• catalase negative

• smaller zone of beta hemolysis

• colonies are larger

• CAMP positive

• PYR negative

• considered normal flora in female genital tract

Streptococcus pneumoniae

• GPC pairs in a lancet shape (end to end)

• polysaccharide capsule (interferes with phagocytosis)

• P disk sensitive

• bile soluble

• alpha hemolytic

Streptococcus viridans

• GPC in chains (can mutate into longer rods)

• small, dry, and alpha hemolytic on SBA

• P-disk resistant

• bile esculing negative

• salt broth negative

• normal flora of the throat

Enterococcus spp.

• GPC

• catalse negative or weak positive

• usually gamma hemolytic

• can be beta or alpha

• bile esculin positive

• salt broth positve

• PYR positive

• normal bowel flora

Streptococcus gallolyticus

“Group D strep”

• GPC

• catalase negative

• gamma hemolytic

• Bile esculin positive

• salt broth negative

Listeria Monocytogenes

• GPR (very short)

• catalase positive

• beta hemolytic

• VP positive

• bile esculin positive

• umbrella motility

Corynebacterium

• GPR

• palisading or coryneform (L and V shapes)

• small, cream colonies

• gamma hemolytic

• no growth on MAC

• resembles CoNS

• catalase positive

• nonmotile

• no spores

Corynebacterium diphtheriae

• GPR

• asporogenous

• grows on SBA

• grows on cystine-tellurite and tinsdale agar

Bacillus

• ubiquitous

• aerobic

• large GPR often in chains

• catalase positive

• produces endospores

• large colonies with irregular edges

Bacillus anthracis

• anthrax

• medusa head colony with ground glass

• leathery

• gamma hemolytic

• catalase positive

• nonmotile

• penicillin sensitive

• nonmotile

• spores

Bacillus cereus

• food poisoning

• large GPR

• beta hemolytic

• ground glass colony

• motile

• lecithinase positive

• pencillin resistant

Erysipelothrix rhusiopathiae

• GPR (short or filamentous) easily decolorized

• small colonies either rough or smooth

• catalase negative

• non motile

• gamma or weakly alpha

• H2S positive

• associated with animals

lactobacillus

• GPR often in chains (pliemorphic)

• small colonies

• alpha or gamma

• catalase negative

• cultative

• grow well in thioglycollate broth

• vancomycin resistant

Gardnerella vaginalis

• Gram variable rods

• plieomorphic

• tiny gamma colonies

• beta hemolytic on HBT agar

• catalase negative

• oxidase negative

• inihibited by SPS

• look for clue cells

• disease: bacterial vaginosis

arcanobacterium haemolyticum

• delicate, curved GPR with pointed ends

• usually beta

• catalase negative

Trueperella spp.

• short GPR

• catalase negative

Neisseria spp.

• GNDC (like two kidney beans)

• aerobic

• oxidase positive

• non motile

• intracellular!

• grow at body temp

• fastidious (needs blood)

• sensitive to fatty acids and trace metals

• rapid autolysis

• highly susceptible to drying and extreme temps

• grows best in CO2

Neisseria meningitidis

• GNDC

• attachment is key

• has piliand proteins

• polysaccharide capsule

• endotoxin

• gamma

• oxidase positive

• round, smooth, moist , gray colonies

Neisseria gonorrhoeae

• GNDC inside of wbc

• culture on choc or thayer-martin (highly selective)

• no growth on SBA

• oxidase positive

• utilizes glucose only

non-pathogenic Neisseria spp.

(saphrophytic neisseria)

• normal oropharyngeal flora

• less picky

• N. sicca utilizes glucose, maltose, sucrose

• N. lactamica utilizes glucose, maltose, lactose

• usually yellowish and greenish on plates

Moraxella catarrhalis

• GNDC (larger)

• oxidase positive

• opportunistic

• common oropharyngeal or skin flora

• often holds onto CV

• asaccharolytic

• SBA and choc in carbon dioxide

• nitrate positive

• DNase positive

• butyrate esterase positive

other Moraxella and Neisseria spp.

• animal bite wounds

• coccobacilli or short to medium rods

• doesnt ferment gluocse

• grows well on SBA and CHOC

• prefer ambient air

Haemophilus spp.

• short GNR or GNCB

• facultative anaerobes

• fastidious (needs growth factors) need V and X factor

Haemophilus influenzae

• GNR or GNCB

• upper respiratory trac normal flora

• no growth on SBA (NADase activity)

• causes meningitis

• typeable if contains capsular antigens

• most common type: B

• capsules and attachment factors are virulence factors

• can satellite around staph

Haemophillus ducreyi

• mimics syphillis

• GNR

• doesnt require NAD (V factor)

Enterobacteriaceae

• facultative anaerobes

• GNR (usually short and plump)

• no spores

• grow well on MAC (fermenter or non)

• ferment glucose

• oxidase negative

• nitrate positive

• most are catalase positive

• normal flora in GI tract

• usually causes diarrheal illness

Escherichia coli

• dry colonies

• most are lactose fermenters

• IMViC = + + - -

• motile

• lysine positive

• urea negative

• TSI = A/A with gas

Klebsiella pneumoniae

• mucoid colonies

• IMViC = - - + +

• nonmotile

• lysine positive

• ornithine and arginine negative

• urea positive

• all resistant to ampicillin

• TSI = A/A with gas

Enterobacter cloacae

• lactose fermenter

• IMViC = - - + +

• motile

• arginine and ornithine positive

• urea negative or positive

• TSI = A/A with gas

citrobacter freundii

• fermenter or nonfermenter

• IMViC = - + - +

• motile

• ornithine negative

• TSI = A/Ag H2S +

citrobacter koseri

• usually nonlactose fermenter

• IMViC = + + - +

• motile

• ornithine positive

• TSI = A/Ag H2S +

proteus mirabilis

• nonlactose fermenter

• PAD positive

• indole negative

• ornithine positive

• urea positive

• motile

• TSI = K/A H2S+

• swarmer

proteus vulgaris

• sucrose fermenter

• nonlactose fermenter

• PAD positive

• indole positive

• ornithine negative

• urea positive

• motile

• TSI = A/A H2S+

• swarmer