bacterial genera

Staphylococci Streptococci/ Enterococci

CATALASE

+ -

Coagulase (+) Coagulase (-)

-hemolytic

-hemolytic non-hemolytic

(γ)

• Lancefield group D • Black colonies on

bile-esculin agar • Normal GI flora

Gram-positive

cocci

• CoNS • Normal flora on

skin, nares, vagina

S. epidermidis •Novobiocin susceptible

S. saprophyticus •Novobiocin resistant

S. pneumoniae Viridans streptococci

Streptococcus pyogenes

Streptococcus agalactiae

• Optochin susceptible

• Bile-soluble • Diplococci • No Lancefield

antigen • Can be part of

normal pharyngeal flora • Bacitracin

susceptible • PYR (+) • Lancefield

group A • Can be part of

normal pharyngeal flora

• Optochin resistant

• Bile resistant • Normal oral

flora • S. mitis

important example

• Various Lancefield groups

• Bacitracin resistant

• PYR (-) • Lancefield

group B

Enterococcus

Streptococcus

• Clear colonies or no growth on bile-esculin agar

• Anaerobes • Facultative anaerobes

Gram positive rods

Spore-forming

Aerobic

Non spore-forming

Anaerobic Aerobic Anaerobic

Bacillus • Found in soil

and water

Clostridium • Found in soil,

water and in human GI tract

• Filamentous, branching

• Part of normal oral , GI flora

Corynebacterium Listeria Nocardia • Part of normal

skin, vaginal, pharyngeal flora

• Can be “club-shaped” or can take appearance of “Chinese letters”

• Catalase (+)

• Will grow at low temperatures (as low as 4C)

• Facultative intracellular

• Distinctive tumbling motility in broth

• Part of normal flora (mouth, vagina, GI)

• Range of oxygen sensitivities, but all are anaerobes (some aerotolerant, some strict)

• Catalase (-)

• Filamentous, branching

• Found in soil & water

• Partially acid-fast

Lactobacillus Actinomyces

Neisseria sp. •Diplococci •Often associated with PMNs in direct smear •5% CO2, facultative anaerobe •Chocolate or Thayer-Martin agar •Oxidase-positive • Ferment glucose • Some species normal in throat

Gram-negative cocci

Moraxella sp. •Often diplococcus • Resembles Neisseria

•Normal respiratory flora Acinetobacter sp. •Can be cocci or rods • May resemble Neisseria

•Oxidase negative •Normal oropharyngeal flora •Soil/plants Bordetella sp. •Bordet-Gengou agar •Regan-Lowe agar •7-12 d incubation • NAAT often used Francisella sp. •Very small, faint staining •Requires cysteine •BCYE or chocolate agars •3 day incubation Brucella sp. •Small, intracellular •Difficult to detect •Enriched blood agar •3 d or longer incubation

Aerobes

Gram-negative bacilli

Pseudomonas sp. •Oxidase-positive •Actually facultative but NOT fermentative

Legionella sp. •Thin, can be short or long •Clinical specimens do not Gram stain well

•Dieterle silver stain •Direct fluorescent antibody test (DFA) •Obligate aerobe •Requires cysteine, iron •BCYE agar •3-5 day incubation

Curved and Spiral rods

Campylobacter sp. •Can have “gull wing” appearance •Oxidase-positive •Microaerophilic •Grow at 42C

Vibrio sp. •Comma shaped rods •Oxidase-positive •Likes alkaline environment

Helicobacter sp. •Oxidase positive •Urease-positive •Microaerophilic

Straight rods Coccobacilli/ pleomorphs

Oxidase (-)

Lactose-fermenting

Non-lactose fermenting

Citrobacter Enterobacter Escherichia Klebsiella •Often highly mucoid •Non-motile

Non-H2S -producing

H2S -producing

Proteus •Swarming motility •Urease-positive

Salmonella •Motile

Shigella •Non-motile

Yersinia •Bipolar staining (“Safety-pin”) •Urease-positive

Haemophilus •Coccobacilli •Facultative anaerobe •Can grow as long filaments •Requires factor X (heme) and factor V (NAD) •Chocolate agar Pasturella •Coccobacilli •Can display bi-polar staining (“safety pin”) •Facultative anaerobe •Blood or chocolate

Anaerobes

Bacteroides •Pleomorphic •Stain poorly •Easy to grow •Normal GI, oral flora Prevotella •Very small •Slow growing, fastidious •Normal oral flora Porphyromonas •Very small •Slow growing, fastidious •Normal (?) oral flora

Facultative anaerobes

Oxidase (+)

Enterobacteriaceae • Ferment glucose • Normal GI flora • Multiple tests required to

get down to genus (indole, citrate, MR-VP, lysine decarboxylase, motility, urease, H2S)

• Serratia can be lac(+/-), produces red pigment

Organisms that do not Gram-stain

Spirochetes Obligate

Intracellular Mycobacteria

Treponema • Has never been

cultured Borrelia Leptospira

• Long, flexible spirals • Endoflagella • Gram-negative

cell wall

• In vivo, may survive outside host cells but cannot grow

• Cannot culture on semi-solid media

Chlamydia, Chlamydophila

• Cannot make their own ATP

• Gram-negative-like Rickettsia • Gram-negative Ehrlichia • Gram-negative Anaplasma • Gram-negative Coxiella • Gram-negative • Axenic culture now

possible

Mycoplasma

• Small rods • Cell wall contains

waxy mycolic acids • Resistant to drying,

chemical agents, germicides

• Slow growing

• Lack a cell wall • Pleomorphic • Sensitive to

environmental conditions

• Hard to grow in laboratory

• “Fried-egg” colonies

Staphylococcus aureus • Normal flora

on skin, in nares

• Colonies often yellow

• Salt tolerant • Produces acid

from mannitol