Chapter 7 CATALASE POSITIVE GRAM POSITIVE COCCI
Chapter 7 CATALASE POSITIVE GRAM POSITIVE COCCI
Chapter 7 CATALASE POSITIVE GRAM POSITIVE COCCI
• Heterogeneous group of organisms • The skin colonizers – Micrococcus spp., Kocuria spp.,
• Previously, genus Staphylococcus was included and Kytococcus spp.
with the genus Micrococcus in the family ✓ Easily confused with staphylococci
Micrococcaceae ✓ Usually associated with skin lesions
• molecular phylogenetic and chemical analysis, ✓ isolated from immuno-compromised
Staphylococcus has now been combined with patients
Bacillaceae, Planacoccaceae, Listeriaceae into the • Clinically significant organisms in this chapter belong
order Bacillales to genus Staphylococcus
• Several of the Micrococcus spp. are now Epidemiology
reclassified into the genera Kocuria, Nesterenkonia,
Kytococcus, and Dermacoccus – these genera are • Staphylococci associated with infections in humans
reorganized into Micrococcaeae and are colonizers of various skin and mucosal surfaces
Dermacoccaceae • Three types of nasal carrier states associated with
• Alloiococcus otitidis – biochemically similar to the Staphylococcus aureus:
families included in this chapter; belongs to the ✓ Persistent carriers - harbor a single strain for an
family Carnobacteriaceae extended period of time
• All organisms discussed in this chapter are catalase ✓ Intermittent carriers – harbor different strains
positive, gram positive, aerobic or facultatively over time
anaerobic ✓ Individuals that do not harbor any organisms or
• Exceptions (obligate anaerobes and maybe gram non-carriers
negative): • Because the carrier state is common, infections are
✓ Staphylococcus aureus subsp. Anaerobius frequently acquired when the colonizing strain gains
✓ Staphylococcus saccharolyticus entry to a normally sterile site due to trauma or
• Genus Staphylococcus are non-motile and non-spore abrasion to the skin or mucosal surface
forming • High Incidence of Carrier State
• Coagulase-negative staphylococci (CoNS) or non- ✓ Health care workers
Staphylococcus aureus ✓ Immuno-compromised individuals,
• Divided into two groups based on novobiocin including those with insulin-dependent
susceptibility pattern diabetes mellitus
• Novobiocin-susceptible CoNS – Examples are ✓ Long-term haemodialysis patients
Staphylococcus capitis, Staphylococcus haemolyticus, ✓ IV drug users
Staphylococcus hominis subsp. hominis, ✓ Vaginal carriage may be seen in
Staphylococcus lugdunensis, Staphylococcus premenopausal women
saccharolyticus, and Staphylococcus warneri • Staphylococci are also transmitted from person to
person
✓ Upon transmission, organisms become
established as part of recipient’s normal
flora
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MICROCOCCACEAE
Micrococcus
• Catalase – positive
• Coagulase – negative
• Normally found in:
✓ Environment
✓ Skin
✓ Maybe isolated as contaminant or as part of
the normal of the skin and respiratory tract
• Opportunistic pathogen found in immuno-
compromised patients
• Often recovered with staphylococci
• Low pathogenic significance
FAMILY STAPHYLOCOCCACEAE
COLONIAL CHARACTERISTICS
➢ Lysostaphin Susceptibility Test
✓ Cream-colored, off - white or rarely light gold
▪ Lysostaphin is an endopeptidase that and “buttery-looking”
cleaves the glycine-rich pentapeptide ✓ Oil-paint like, pin head colonies
cross bridges in the staphylococcal cell ✓ Jet black in tellurite lysine agar
wall peptidoglycan • Common isolates in clinical laboratory
▪ The susceptibility of Staphylococcus to • Responsible for supurative type of infections
lysostaphin is used to differentiate them
from Micrococcus
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Staphylococcus aureus
VIRULENCE FACTORS
Toxins
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➢ Coagulase test
• Once an isolate is identified as, or strongly
suspected to be, a Staphylococcus sp., a
coagulase test is performed to
differentiate Staphylococcus aureus from
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➢ Free coagulase
✓ Tube coagulase test (detects both free and
bound)
✓ Definitive test for Staphylococcus aureus
✓ used to confirm all slide test negative results on
clinically significant isolates
✓ demonstrates the presence of extracellular
staphylocoagulase (free coagulase)
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Purpose:
▪ Undefined, selective medium
▪ Used to isolate
staphylococci and
streptococci from
specimens containing
mixtures of bacterial
flora
▪ Typically used for
specimens thought
to also contain
Escherichia coli or
strains of Proteus
▪ Allows growth of gram-positive
organisms
▪ Stops or inhibits growth
of most gram-negative organisms
▪ Most gram-positive rods will also grow on this
medium, except Bacillus anthracis, which is unique
among the Bacillus spp. in its lack of growth on this
medium
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Principle:
▪ active ingredient, phenylethyl alcohol, functions by
interfering with DNA synthesis in gram-negative
organisms
▪ PEA also inhibits facultative gram-negative rods,
especially swarming Proteus spp., but permits the
growth of gram-positive cocci
▪ When prepared with 5% sheep blood,
it is used for cultivation of
gram-positive anaerobes
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