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Micrococcaceae
Student Lab
Division of Laboratory Sciences
Michele Jurgensmeier MT(ASCP)
General Information
• Cause human infections
• Recover from various clinical specimens
• Found in many places
• Spread by direct contact
• Elaborate an inflammatory response
• Produce pathogenic effects
Gram Positive Cocci
Family Micrococcaceae
Gram Stain: Gram positive cocci
Catalase: Positive
Gram Stain• Gram Positive Cocci in tetrads
Micrococcus species
Growth Characteristics
• Aerobic
• Colony morphology– Smooth, raised,
opaque– Pigment
Micrococcus species
Biochemical Characteristics
• Non-motile• Non-spore forming• Glucose oxidizer• Modified oxidase +• Bacitracin sensitive• Furazolidine Resistant• Lysostaphin Resistant
Micrococcus species
• Bacitracin Sensitive• Zone size > 10 mm
around disk
Micrococcus species
• Glucose Oxidizer• Tube on left shows
glucose oxidation by the presence of yellow color (No oil overlay)
• Tube on right shows no fermentation of glucose (oil overlay)
Micrococcus species
Clinical Significance
• Rarely produces disease
• Normal flora
• Opportunistic infection– Immunocompromised
Micrococcus species
Antibiotic Therapy
• Test methods and therapeutic guidelines do not exist
• Susceptible to beta-lactam antimicrobics
Micrococcus species
Gram Stain• Gram Positive Cocci in clusters
Staphylococcus species
Growth Characteristics
• Facultative anaerobes
Staphylococcus species
• Colony morphology– Opaque, smooth,
circular– Gray-white, white, cream, yellow– Hemolysis
• S. aureusbeta-hemolytic
Biochemical Characteristics
• Non-motile• Non-spore forming• Glucose fermenter• Modified oxidase -• Bacitracin resistant• Furazolidine sensitive• Most are sensitive to Lysostaphin• Variable growth in 6.5 % Salt (Salt
tolerance)
Staphylococcus species
Micrococcus Staphylococcus species species
• Gram positive cocci• Catalase = Positive• Bacitracin = Sens.• Mod. Oxidase = Pos• Glucose Oxidizer
• Gram Positive cocci• Catalase = Positive• Bacitracin = Sens.• Mod. Oxidase = Neg• Glucose Fermenter
Colony morphology
• Opaque, smooth• Raised colony with
smooth border• White-gold (cream)
in color• Beta hemolytic
Staphylococcus aureus
Biochemical Characteristics
• Coagulase +
Staphylococcus aureus
• Mannitol salt +
• DNase +
Mechanisms of Pathogenicity
• Capsule• Enzymes
– Catalase– Coagulase– Staphylokinase– Hyaluronidase– DNase– Beta-lactamase
• Toxins– Hemolysin– Leukocidin– Exfoliatin– Enterotoxin
• TSST-1
Staphylococcus aureus
Clinical SignificanceStaphylococcus aureus
Impetigo
Scalded Skin Syndrome
Antibiotic Therapy
• Penicillinase (beta-lactamase)
• Agents resistant to penicillinase– Methicillin– Oxacillin– Nafcillin
• Methicillin Resistant Staph aureus– Drug of choice - vancomycin
Staphylococcus aureus
Methicillin Resistant S. aureus
• “S” & “R” strains coexist
• “R” strains grow more slowly
• Growth requirements:– Media with neutral pH– Cooler temperature (30-35° C)– 2-4% NaCl– Incubate full 24 hours
Staphylococcus aureus
Clinical SignificanceCoagulase Negative Staphylococcus
Colony morphology
• Opaque• Smooth, raised
Staphylococcus epidermidis
• Gray- white in color
Biochemical Characteristics
• Coagulase -
Staphylococcus epidermidis
• Mannitol salt -
• DNase –• Novobiocin “S”
Mechanisms of PathogenicityStaphylococcus epidermidis
• Capsule
• Extracellular slime substance
Clinical Significance
• Normal flora
• Subacute bacterial endocarditis
• Meningitis
• Bacteremia / Septicemia
• Wound infections
• Urinary tract infections
• Post-operative infections
Staphylococcus epidermidis
Antibiotic Therapy
• More resistant than Staph aureus
• Susceptibility testing done if presumed pathogen
• Drugs of choice– Methicillin– Vancomycin (if methicillin “R”)
Staphylococcus epidermidis
Biochemical Characteristics
• Coagulase -
Staphylococcus saprophyticus
• Mannitol salt variable
• DNase –• Novobiocin “R” (<16 mm)
Clinical Significance
• Urinary tract infections– Cystitis in young women– Frequency - 2nd to E. coli
Staphylococcus saprophyticus
Antibiotic Therapy
• Susceptibility testing not routinely done
• Drugs of choice– Nitrofurantoin– Trimethoprim/sulfamethoxizole– Fluoroquinolone
• Lack correlation between in vitro and in vivo response
Staphylococcus saprophyticus
GPC - Catalase Positive
Micrococcaceae
Modified oxidaseBacitracin
OF Glucose
PositiveSensitiveOxidizer
NegativeResistantFermenter
Micrococcus species
+ Coagulase -
Staphaureus
“R” Novobiocin “S”
ProbableStaph
sapro
Coag neg Staph