VIII - Gram-Positive Bacteria Flashcards
Gram (+) cocci in grape-like clusters, β-hemolytic yellow or golden colonies on blood agar, catalase (+), coagulase (+)
Staphylococcus aureus
Staphylococcus aureus is cultured in _____ because of salt tolerance.
Mannitol Salt Agar
The gold color of Staphylococcus aureus is due to
staphyloxanthin
S. aureus: Location
human nose (anterior nares), skin
S. aureus: Transmission
direct contact (hands), fomites, contaminated food
S. aureus Immunomodulators: Prevents complement activation
Protein A
S. aureus Immunomodulators: Builds an insoluble fibrin capsule
Coagulase
S. aureus Immunomodulators: Toxic to hematopoietic cells
Hemolysins (Cytotoxins)
S. aureus Immunomodulators: Specific for White Blood Cells
PV Leukocidin
S. aureus Immunomodulators: Detoxifies hydrogen peroxide
Catalase
S. aureus Immunomodulators: Inactivates penicillin derivatives
Penicillinase
S. aureus Tissue Penetrance: Hydrolyzes hyaluronic acid
Hyaluronidase
S. aureus Tissue Penetrance: Dissolves fibrin clots
Fibrinolysin (Staphylokinase)
S. aureus Tissue Penetrance: Spread in fat-containing areas of the body
Lipase
S. aureus Toxins: Causes epidermal separation
Exfoliatin
S. aureus Toxins: Superantigens causing food poisoning
Enterotoxins (heat-stable)
S. aureus Toxins: Superantigen leading to toxic shock syndrome
Toxic Shock Syndrome Toxin (TSST-1)
S. aureus Toxins: Causes marked necrosis of the skin and hemolysis
Alpha Toxin
S. aureus Pyogenic Disease: Skin and Soft Tissue
bullous impetigo, folliculitis, furuncles, carbuncles, cellulitis, hidradenitis suppurativa, mastitis, surgical site infections
Bullous impetigo, foliculitis, furuncles, carbuncles, cellulitis, hidradenitis suppurativa, mastitis, surgical site infections
Staphylococcus aureus
Most common cause of acute endocarditis
Staphylococcus aureus
Acute endocarditis usually affects _____ in _____.
native tricuspid valve, IV drug users
S. aureus Pyogenic Disease: Pneumonia
nosocomial pneumonia, VAP, necrotizing pneumonia, complicated by empyema, abscess or pneumatocoele, post-viral
Nosocomial pneumonia, VAP, necrotizing pneumonia, complicated by empyema, abscess or pneumatocoele, post-viral
Staphylococcus aureus
Osteomyelitis and septic arthritis come from _____ spread or _____ at the wound site.
hematogenous spread, local introduction
Sequestered focus of osteomyelitis arising in the metaphyseal area of a long bone
Brodie Abscess
S. aureus: Pyogenic Infections
skin, soft tissue, acute endocarditis, pneumonia, osteomyelitis, septic arthritis
S. aureus: Toxigenic Infections
gastroenteritis, Scalded Skin Syndrome (Ritter Disease), Toxic Shock Syndrome
Gastroenteritis has _____ onset of vomiting and diarrhea due to ingestion of _____ from _____.
acute (4 hours), preformed heat-stable enterotoxin from S. aureus, salad with mayonnaise
S. aureus exfoliatin cleaves _____ in desmosomes leading to separation of epidermis in the _____ causing _____.
desmoglein, stratum granulosum, Scalded Skin Syndrome (Ritter disease)
Separation of the dermo-epidermal junction
Toxic Epidermal Necrolysis (Lyell Disease)
Fever, hypotension, sloughing of the filiform papillae → strawberry tongue, desquamating rash, multiorgan involvement (>3), usually no site of pyogenic inflammation, blood CS (-)
Toxic Shock Syndrome (S. aureus)
Seen in tampon-using menstruating women or in patients with nasal packing for epistaxis
Toxic Shock Syndrome (S. aureus)
Methicillin-Sensitive SA (MSSA): Treatment
penicillinase-resistant penicillins (nafcillin, oxacillin, dicloxacillin)
Methicillin-Resistant SA (MRSA): Treatment
Vancomycin
Vancomycin-Resistant SA (MRSA): Treatment
Linezolid
Staphylococcus aureus with altered penicillin binding proteins
Methicillin-Resistant SA (MRSA
Gram (+) cocci in clusters, catalase (+), coagulase (-), novobiocin-sensitive, whitish, non-hemolytic colonies on blood agar
Staphylococcus epidermidis
S. epidermidis: Location
normal skin flora
S. epidermidis: Transmission
autoinfection, direct contact (hands)
S. epidermidis is a ___-virulence organism with _____ which adheres well to foreign bodies and form biofilms.
low-virulence, glycocalyx
Most common cause of prosthetic valve endocarditis
Staphylococcus epidermidis
Most common cause of septic arthritis in prosthetic joints
Staphylococcus epidermidis
Most common cause of ventriculoperitoneal shunt infections
Staphylococcus epidermidis
S. epidermidis: Treatment
removal of prosthetic device, Vancomycin (over 50% are methicillin-resistant)
Gram (+) cocci in clusters, catalase (+), coagulase (-), novobiocin-resistant, whitish, non-hemolytic colonies on blood agar
Staphylococcus saprophyticus
2nd most common cause of UTI in sexually active women
Staphylococcus saprophyticus
S. saprophyticus: Findings
dysuria, pyuria, bacteriuria
S. saprophyticus: Treatment
TMP-SMX, quinolones
Gram (+) cocci in chains, β-hemolytic, catalase (-), bacitracin-sensitive, Lancefield group A, PYR test (rapid identification)
Streptococcus pyogenes (GABHS)
S. pyogenes: Location
human throat (oropharynx), skin
S. pyogenes: Transmission
respiratory droplets
S. pyogenes Virulence Enzymes: Degrades hyaluronic acid (spreading factor)
Hyaluronidase
S. pyogenes Virulence Enzymes: Activates plasminogen
Streptokinase (Fibrinolysin)
S. pyogenes Virulence Enzymes: Degrades DNA in exudates or necrotic tissue
DNAse (Streptodornase)
S. pyogenes Virulence Enzymes: Inactivates complement C5A
C5A Peptidase
S. pyogenes Toxins: Produces scarlet fever
Erythrogenic Toxin
S. pyogenes Toxins: Highly antigenic, causes AB formation
Streptolysin O (oxygen-labile)
S. pyogenes Toxins: Oxygen-stable
Streptolysin S
S. pyogenes Toxins: Superantigen similar to TSST
Pyogenic Exotoxin A
S. pyogenes Toxins: Protease that rapidly destroys tissue → necrotizing fascitis
Exotoxin B
Document antecedent S. pyogenes pharyngitis
Anti-Streptolysin O (ASO)
Document antecedent S. pyogenes skin infection
Anti-DNAse B
Streptolysin O is irreversibly inhibited by
cholesterol in skin lipids
Decrease the efficacy of streptokinase in managing MI
Anti-Streptokinase Antibodies
S. pyogenes: Pyogenic Infections
impetigo contagiosa, erysipelas, cellulitis, necrotizing fascitis, pharyngitis
Impetigo contagiosa, erysipelas, cellulitis, necrotizing fascitis, pharyngitis
Streptococcus pyogenes
Perioral blistered lesions with honey-colored crust, accumulation of neutrophils beneath stratum corneum, PSGN
Impetigo Contagiosa
Superficial infection extending into dermal lymphatics
Erysipelas
Deeper infection involving subcutaneous/dermal tissues, facilitated by hyaluronidase (spreading factor)
Cellulitis
Rapidly progressive infection of deep subcutaneous tissues, facilitated by exotoxin B
Necrotizing Fascitis
Most common bacterial cause of sore throat
Streptococcus pyogenes
Pharyngeal inflammation, exudate, fever, leukocytosis, tender CLAD
Pharyngitis
Pyogenic Complications of Pharyngitis
abscess, otitis, sinusitis, meningitis
Post-pharyngitic, due to erythrogenic toxin, seen in lysogenized strains, fever, strawberry tongue, centrifugal rash (sandpaper-like), Pastia’s lines, desquamation
Scarlet Fever
Test for Scarlet Fever Susceptibility
Dick Test
Clinically similar but milder than S. aureus TSS, due to pyogenic exotoxin A, recognizable site of pyogenic inflammation, blood culture (+)
Streptococcal Toxic Shock Syndrome
S. pyogenes: Toxigenic Infections
scarlet fever, strep. TSS
S. pyogenes: Immunologic Infections
ARF, GN
Post-pharyngitic, cross-reacting antibodies to M proteins and antigens of the joints, heart and brain
Acute Rheumatic Fever
Jones Criteria
migratory polyarthritis, pancarditis, subcutaneous nodules, erythema marginatum, Sydenham chorea
Post-pharyngitic or post-impetigo, M protein incites immune complex deposition on the glomerular basement membrane
Post-Strep Glomerulonephritis
Post-Strep Glomerulonephritis: Findings
hypertension, periorbital edema, hematuria
Post-Strep Glomerulonephritis: Treatment
IV Pen G, antibiotic prophylaxis for patients with hx of RF
Gram (+) cocci in chains, β-hemolytic, catalase (-), bacitracin-resistant, hydrolyze hippurate, CAMP test (+), Lancefield group B, LIM broth
Streptococcus agalactiae (GBS)
S. agalactiae: Location
vagina
S. agalactiae: Transmission
transvaginal, transplacental
S. agalactiae: Pyogenic Infections
UTI in pregnant women, neonatal pneumonia, neonatal sepsis, neonatal meningitis, endometritis (polymicrobial, foul-smelling lochia)
Most common cause of neonatal pneumonia, sepsis and meningitis worldwide
Streptococcus agalactiae (GBS)
Most common cause of neonatal pneumonia, sepsis and meningitis in the Philippines
Escherichia coli
Predisposing Factors for Neonatal GBS Infection
intrapartum fever (>38°C), PROM (>18h), vaginal colonization, complement deficiency