Introduction Classification Bacteria Gram-positive cocci Staphylococcus Staphylococcus aureus Pathogenesis transmission hands sneezing surgical wounds contaminated food custards mayonnaise / potato salad canned meats predisposing factors for infection surgical wounds foreign body tampons surgical packing or sutures severe neutropenia IV drug abuse chronic granulomatous disease cystic fibrosis reservoir normal flora of nasal mucosa or skin 25% of population are carriers molecular biology protein A binds Fc component of IgG, forcing variable region to face away from bacterium inhibits phagocytosis inhibits complement fixation enterotoxins fast acting heat stable toxic shock syndrome toxin-1 (TSST-1) superantigen binds MHC II and T-cell receptor results in polyclonal T-cell activation coagulase converts fibrinogen to fibrin clot exfolatins skin-exfoliating toxins involved in scalded skin syndrome Diseases Gastroenteritis food poisoning salty foods and custards nausea/vomiting, abdominal pain, diarrhea 2-6 hours after ingesting toxin caused by enterotoxins A-E preformed in food symptoms start and end quickly Infective endocarditis (acute) fever, malaise, leukocytosis, heart murmur due to fibrin-platelet mesh Abscesses and mastitis subcutaneous inflammation due to coagulase liver abscesses via hematogenous spread Toxic shock syndrome desquamating rash especially on palms and soles fever, hypotension multiorgan failure caused by TSST-1 Impetigo erythematous papules to bullae due to coagulase, exfoliatins Scalded skin syndrome infants and children epidermal peeling due to exfoliative toxin epidermolytic toxins A and B against desmoglein 1 in stratum granulosum Pneumonia typical, acute, productive, rapid onset nosocomial pneumonia due to coagulase, cytolysins can result in empyema pus in the pleural space Surgical infections Osteomyelitis the most common overall cause of osteomyelitis also associated with prostheses, neonates MRSA (methicillin-resistant S. aureus) infection important cause of serious nosocomial and community-acquired infections resistant to β-lactams due to altered penicillin-binding protein Laboratory Coagulase positive β-hemolytic Small yellow colonies on blood agar Ferments mannitol Treatment Nafcillin/oxacillin MRSA vancomycin clindamycin TMP-SMX VRSA quinupristin/dalfopristin Gastroenteritis is self-limiting
QUESTIONS 1 of 5 1 2 3 4 5 Previous Next Lab Values Blood Hematologic Cerebrospinal Sweat, Urine, and BMI Blood, Plasma, Serum Reference Range ALT 8-20 U/L Amylase, serum 25-125 U/L AST 8-20 U/L Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL Calcium, serum (Ca2+) 8.4-10.2 mg/dL Cholesterol, serum Rec: < 200 mg/dL Cortisol, serum 0800 h: 5-23 μg/dL //1600 h: 3-15 μg/dL 2000 h: ≤ 50% of 0800 h Creatine kinase, serum Male: 25-90 U/LFemale: 10-70 U/L Creatinine, serum 0.6-1.2 mg/dL Electrolytes, serum Sodium (Na+) 136-145 mEq/L Chloride (Cl-) 95-105 mEq/L Potassium (K+) 3.5-5.0 mEq/L Bicarbonate (HCO3-) 22-28 mEq/L Magnesium (Mg2+) 1.5-2.0 mEq/L Estriol, total, serum (in pregnancy) 24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL 28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL Ferritin, serum Male: 15-200 ng/mLFemale: 12-150 ng/mL Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL Female: premenopause: 4-30 mIU/mL midcycle peak: 10-90 mIU/mL postmenopause: 40-250 pH 7.35-7.45 PCO2 33-45 mmHg PO2 75-105 mmHg Glucose, serum Fasting: 70-110 mg/dL2-h postprandial:<120 mg/dL Growth hormone - arginine stimulation Fasting: <5 ng/mLProvocative stimuli: > 7ng/mL Immunoglobulins, serum IgA 76-390 mg/dL IgE 0-380 IU/mL IgG 650-1500 mg/dL IgM 40-345 mg/dL Iron 50-170 μg/dL Lactate dehydrogenase, serum 45-90 U/L Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL Female: follicular phase: 5-30 mIU/mL midcycle: 75-150 mIU/mL postmenopause 30-200 mIU/mL Osmolality, serum 275-295 mOsmol/kd H2O Parathyroid hormone, serume, N-terminal 230-630 pg/mL Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L Phosphorus (inorganic), serum 3.0-4.5 mg/dL Prolactin, serum (hPRL) < 20 ng/mL Proteins, serum Total (recumbent) 6.0-7.8 g/dL Albumin 3.5-5.5 g/dL Globulin 2.3-3.5 g/dL Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h Thyroxine (T4), serum 5-12 μg/dL Triglycerides, serum 35-160 mg/dL Triiodothyronine (T3), serum (RIA) 115-190 ng/dL Triiodothyronine (T3) resin uptake 25%-35% Urea nitrogen, serum 7-18 mg/dL Uric acid, serum 3.0-8.2 mg/dL Hematologic Reference Range Bleeding time 2-7 minutes Erythrocyte count Male: 4.3-5.9 million/mm3Female: 3.5-5.5 million mm3 Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/hFemale: 0-20 mm/h Hematocrit Male: 41%-53%Female: 36%-46% Hemoglobin A1c ≤ 6 % Hemoglobin, blood Male: 13.5-17.5 g/dLFemale: 12.0-16.0 g/dL Hemoglobin, plasma 1-4 mg/dL Leukocyte count and differential Leukocyte count 4,500-11,000/mm3 Segmented neutrophils 54%-62% Bands 3%-5% Eosinophils 1%-3% Basophils 0%-0.75% Lymphocytes 25%-33% Monocytes 3%-7% Mean corpuscular hemoglobin 25.4-34.6 pg/cell Mean corpuscular hemoglobin concentration 31%-36% Hb/cell Mean corpuscular volume 80-100 μm3 Partial thromboplastin time (activated) 25-40 seconds Platelet count 150,000-400,000/mm3 Prothrombin time 11-15 seconds Reticulocyte count 0.5%-1.5% of red cells Thrombin time < 2 seconds deviation from control Volume Plasma Male: 25-43 mL/kgFemale: 28-45 mL/kg Red cell Male: 20-36 mL/kgFemale: 19-31 mL/kg Cerebrospinal Fluid Reference Range Cell count 0-5/mm3 Chloride 118-132 mEq/L Gamma globulin 3%-12% total proteins Glucose 40-70 mg/dL Pressure 70-180 mm H2O Proteins, total < 40 mg/dL Sweat Reference Range Chloride 0-35 mmol/L Urine Calcium 100-300 mg/24 h Chloride Varies with intake Creatinine clearance Male: 97-137 mL/minFemale: 88-128 mL/min Estriol, total (in pregnancy) 30 wks 6-18 mg/24 h 35 wks 9-28 mg/24 h 40 wks 13-42 mg/24 h 17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 hFemale: 2.0-8.0 mg/24 h 17-Ketosteroids, total Male: 8-20 mg/24 hFemale: 6-15 mg/24 h Osmolality 50-1400 mOsmol/kg H2O Oxalate 8-40 μg/mL Potassium Varies with diet Proteins, total < 150 mg/24 h Sodium Varies with diet Uric acid Varies with diet Body Mass Index (BMI) Adult: 19-25 kg/m2 Calculator ( ) xy AC 7 8 9 ÷ 4 5 6 × 1 2 3 - 0 . = + Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.MC.104) A 14-year-old Caucasian male presents with painful erythematous and honey-colored crusted lesions around his mouth. Culture of the lesions reveals gram-positive cocci in clusters. Further analysis reveals bacteria that are beta-hemolytic, coagulase positive, catalase positive, and appear golden on the blood agar plate. Which of the following helps the bacterium in this infection bind to immunoglobulin and prevent phagocytosis when invading its host? Review Topic QID: 101563 FIGURES: A B 1 Protein A 44% (8/18) 2 Staphylokinase 0% (0/18) 3 Exfoliatin A 0% (0/18) 4 Protein M 50% (9/18) 5 Neurotoxin 0% (0/18) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 1 (M1.MC.81) A 63-year-old female recovering from a total shoulder arthroplasty completed 6 days ago presents complaining of joint pain in her repaired shoulder. Temperature is 39 degrees Celsius. Physical examination demonstrates erythema and significant tenderness around the incision site. Wound cultures reveal Gram-positive cocci that are resistant to nafcillin. Which of the following organisms is the most likely cause of this patient's condition? Review Topic QID: 101540 1 Streptococcus viridans 0% (0/15) 2 Escherichia coli 0% (0/15) 3 Staphylococcus epidermidis 40% (6/15) 4 Staphylococcus aureus 40% (6/15) 5 Streptococcus pyogenes 13% (2/15) M1 Select Answer to see Preferred Response PREFERRED RESPONSE 4
S. aureus Microbiology - Staphylococcus aureus - Treatment Consult This video gives an in-depth look at S. Aureus. 2/14/2015 75 views