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