bacterial genera
DESCRIPTION
Bacterial GeneraTRANSCRIPT
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