Staphylococcaceae and Micrococcus species Flashcards
Staphylococcal infections of the skin
pyogenic
inflamed, fibrous lesion enclosing a core of pus restricted to ostia
abscess
a mild inflammation of the superficial dermis of the hair follicles
Folliculitis
characterized by the presence of small, reddish, painful lesions and the absence of systemic symptoms
Folliculitis
If folliculitis occurs in the eyelid, it is referred to as
stye (or sty).
a chronic or relapsing inflammatory disease of the skin, involving the apocrine gland-bearing areas axillae, groin, perineal
Hidradenitis suppurativa
characterized by presence of multiple lesions associated with blocked and infected apocrine sweat glands
Hidradenitis suppurativa
local pain (swelling and erythema) = present
systemic symptoms (fever) = absent.
Hidradenitis suppurativa
little thief
furunculus
is a
deeper-seated infection of the hair follicles
Furuncle
boil
Furuncle
results when the inflammation of single hair follicle or sebaceous gland progresses into a large, red, extremely tender abscess or pustule
Furuncle
Furuncles often appear in clusters where skin rubs against other skin or clothing
furunculosis
little coal
carbunculus
a larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles
Carbuncle
found in areas of which tough skin such as on the back of the neck
Carbuncle
not confined to follicles and skin glands
Impetigo
to attack
impetus
characterized by bubble-like epidermal sweeping that can break and peel away like a localized form of scalded skin syndrome
Impetigo
present on exposed areas
Impetigo
autoinoculation
Impetigo
two forms of Impetigo
non-bullous and bullous
begins as a single red macule (patch) or papule that quickly becomes a vesicle
Non-bullous impetigo
vesicle rupture and forms an erosion
Non-bullous impetigo
honey-colored crusts with erythematous
(reddish) margins that may be pruritic
(itchy)
Non-bullous impetigo
a localized form of staphylococcal scalded skin syndrome that common affects neonates
Bullous impetigo
bullae/blister with sharp margins with no
surrounding erythema
Bullous impetigo
yellow crust with oozing
Bullous impetigo
found in moist, intertriginous areas (diaper area)
Bullous impetigo
ingestion of pre-formed toxin
food intoxication
gastrointestinal illness caused by eating foods contaminated with toxins
Staphylococcal food poisoning
food intoxication rather than a food-borne infection
Staphylococcal food poisoning
acute symptoms that appear in 2 to 6 hours after ingestion of the toxin-contaminated food
Staphylococcal food poisoning
is often projectile, and diarrhea is less frequent
Emesis (vomiting)
Staphylococcal food poisoning recovery is rapid, usually within
24 hours.
associated with eating foods contaminated by handling and then left unrefrigerated for a few hours
Staphylococcal food poisoningv
even foods that contain salt as a food preservative are not exempt
high salt tolerance
toxins produced by the multiplying bacteria does not alter the food’s
taste or smell
Ritter’s disease
Staphylococcal Scalded Skin Syndrome (SSSS)
seen in neonates
Staphylococcal Scalded Skin Syndrome (SSSS)
characterized by widespread erythema and the appearance of bullous lesions
Staphylococcal Scalded Skin Syndrome (SSSS)
exposure of large areas of d e n u d e d ( s t r i p p e d o f surface layers) and raw skin
Staphylococcal Scalded Skin Syndrome (SSSS)
occurs and symptoms wane
over 5-7 days
desquamation
a flu-like illness characterized by fever,
hypotension, and rash on the skin that
resembles a sunburn
Staphylococcal toxic shock syndrome (TSS)
the rash is followed by desquamation 1 – 2 weeks after onset
Staphylococcal toxic shock syndrome (TSS)
involvement of multiple (three or more) organ systems with varying symptoms of vomiting, diarrhea, renal failure, headache, chills, sore throat and
conjunctivitis
Staphylococcal toxic shock syndrome (TSS)
disease was noted most frequently
in women, with onset mainly occurring during menstruation; high-absorbancy tampons during menses
Staphylococcal toxic shock syndrome (TSS)
was reported in males and females as complication of staphylococcal abscesses or systemic infections
non-menstrual-associated TSS
spreading from a local cutaneous infection to other sites
focal pattern
Miscellaneous Systemic Infections
osteomyelitis pneumonia bacteremia endocarditis arthritis meningitis
polysaccharides; electron microscopy
Microcapsule
mediates attachment to host cells or tissues, and inhibits phagocytosis by polymorphonuclear leukocytes
Microcapsule
specific antibodies
Microcapsule
a bacterial surface protein
Protein A
binds to the Fc portion of IgG, leaving the IgG no longer capable of binding to
Fc receptor on phagocytes (preventing
opsonization)
Protein A
blocks complement fixation
Protein A
nactivates toxic hydrogen peroxide and free radicals formed by the
myloperoxidase system
Catalase
promotes conversion of fibrinogen to fibrin causing plasma to clot
Coagulase
Fibrin coat the bacterial cells, hiding their antigenic surface, thus protecting
them from
phagocytosis and immune response.
hydrolyze DNA
. Deoxyribonuclease (DNase)
facilitates the spread of bacteria by liquefying and decreasing the viscosity of abscess materials
. Deoxyribonuclease (DNase)
“spreading factor”
Hyaluronidase
hydrolyzes the intercellular matrix of acid mucopolysaccharides (hyaluronic acid) in tissue
Hyaluronidase
spreads the organism to adjacent areas in tissues
Hyaluronidase
hydrolyzes lipids and help the spread of the organism in cutaneous and subcutaneous tissues
Lipase
a plasminogen activator
Staphylokinase
dissolves fibrin clot (a fibrinolysin)
Staphylokinase
Localized fibtinolysis might aid in the spread of infection to contiguous tissues
Staphylokinase
affects tissues of the host making them more susceptible to damage and destruction by complement components and products
Phosphatidylinositol-specific phospholipase C
affects tissues of the host making them more susceptible to damage and destruction by complement components and products
β-lactamase
is under plasmid-control transmitted by transduction and conjugation a
β-lactamase
provides resistance to β-lactam antibiotics such as penicillin, penicillin derivatives (penams), and cephalosporins.
β-lactamase
β-lactam antibiotics have a common element in their molecular structure: : a four-atom ring known as a β-lactam
hydrolysis
the β-lactamase breaks the β-lactam ring open, deactivating the molecule’s
antibacterial properties
specific type of β-lactamase, showing specificity for penicillins
Penicillinase
The hemolysins lyse red blood cells
Blood Cell Toxins (Hemolysins and Leukocidins)
damage cell membranes of neutrophils and macrophages, causing them to lyse
Leukocidins
help incapacitate the host’s phagocytic line of defense
Blood Cell Toxins (Hemolysins and Leukocidins)
Note that the Greek letter used for the staphylococcal hemolysins do not correspond to the Greek letters describing general patterns of hemolysis in
blood agar medium
is heterogeneous protein that facilitates formation of pores on the target eukaryotic cell membrane
⍺ (alpha)-Hemolysin
osmotic swelling and rupture of the cell.
⍺ (alpha)-Hemolysin
potent toxin lyses red blood cells of various mammals and damages monocytes, macrophages, lymphocytes, skeletal muscle, heart, and renal tissue as well
⍺ (alpha)-Hemolysin
active against thrombocytes (platelets); may contribute to septic thrombotic events during S. aureus bacteremia
⍺ (alpha)-Hemolysin
sphingomyelinase that degrades
sphingomyelin in the cell membrane
(beta)-Hemolysin
protein exotoxin - “hot-cold” hemolysin
(beta)-Hemolysin
hemolytic properties - red blood cells to low temperatures
(beta)-Hemolysin
is known to encode the toxin
lysogenic bacteriophage
cytotoxic not only to human erythrocytes but as well as to monocytes
(beta)-Hemolysin
result from disruption of host cell
plasma membrane fluidity
Cell death
inactive against granulocytes, lymphocytes, and fibroblasts
(beta)-Hemolysin
surfactant or a detergent-like molecule; slow leakage of cellular
contents
δ (delta)-Hemolysin
S. aureus diarrheal diseases
δ (delta)-Hemolysin
Leukocidin that lyses white blood cells
γ (gamma)-Hemolysin
S and F proteins
γ (gamma)-Hemolysin
lysing white blood cells = pore formation in the cellular membranes (increase cation permeability)
γ (gamma)-Hemolysin
Affected cells undergo degranulation of the cytoplasm, cell swelling, and lysis
γ (gamma)-Hemolysin
leads to massive release of inflammatory mediators = necrosis and severe inflammation
γ (gamma)-Hemolysin
produced by lysogenized strains of S. aureus.
Panton-Valentine Leukocidin (PVL)
this pore-forming toxin is active against neutrophils and causes tissue necrosis
Panton-Valentine Leukocidin (PVL)
consists of two components designated as S and F on the wbc as described for γ toxin.
Panton-Valentine Leukocidin (PVL)
superantigen
Toxic Shock Syndrome Toxin (TSST-1)
manifestations of toxic shock syndrome
Toxic Shock Syndrome Toxin (TSST-1)
gene s found in about 20% of S. aureus isolates
Toxic Shock Syndrome Toxin (TSST-1)
protein toxins that stimulate T cells non-specifically without normal antigenic recognition
Superantigens
polyclonal T-cell activation
Superantigens
released in large amounts, leading to an overwhelming inflammatory response
Cytokines
epidermolytic toxins that facilitate dissolution of the mucopolysaccharide matrix of the stratum granulosum in the epidermis
. Exfoliative toxins (or exfoliatins)
intraepithelial splitting of cellular linkages seen in SSSS
. Exfoliative toxins (or exfoliatins)
two distinct proteins of the same molecular weight:
Exfoliative toxin A (ET-A)
Exfoliative toxin B (ET-B)
produced by lysogenized strains of S. aureus
Exfoliative toxin A (ET-A)
plasmid-mediated
Exfoliative toxin B (ET-B)
intestines
“entero”
heat-stable exotoxins which are responsible for the clinical features of staphylococcal food poisoning
Enterotoxins A through E, G-J, K-R and U, V
Heating the food may not prevent the disease because inactivation
of staphylococcal enterotoxin requires 100oC for at least
100oC for at least 30 minutes
temperature for destroying staphylococci in clothes and bedding
controlling reinfection; eliminating the carrier state
increases the bactericidal activity of the skin
chlorhexidine or hexachlorophene soaps
• anterior nasal carriage can be reduced
o combination of nasal creams
o oral therapy w antimicrobials
mupirocin, neomycin, and bacitracin
rifampin or ciprofloxacin
o hip and cardiac valve replacements
• Chemoprophylaxis
o may reduce the chance for intraoperative infection
o Minimizing risk of superinfection (with longer periods of antibiotic administration)
• Methicillin (cephalosporin) or vancomycin
most commonly encountered staphylococcal species
Staphylococcus epidermidis
99% of the normal flora of the skin
Staphylococcus epidermidis
opportunistic pathogens, but are substantially less virulent than S. aureus
Staphylococcus epidermidis
nosocomial infections related to use of contaminated medical devices
Staphylococcus epidermidis
associated with prosthetic heart valves; also pacemaker wires, implanted defibrillators, and vascular grafts
Endocarditis
associated with prosthetic joint, or hip implant
Arthritis
associated with indwelling urinary catheters
Urinary tract infection (UTI)
associated with IV catheters
Bacteremia
Pathogenesis is related to production of [?] resulting in biofilm formation
on the surface of a prosthetic device
adherent slime
Primarily a saprophyte
Staphylococcus saprophyticus
Gastrointestinal tract (primarily the rectum) as the primary site of colonization in humans
Staphylococcus saprophyticus
part of the normal flora of female genitourinary tract (urethra, cervix), perineum
Staphylococcus saprophyticus
Second most common cause of community-acquired UTI in young, sexually active females (most common is Escherichia coli)
Staphylococcus saprophyticus
Pathogenesis of Staphylococcus saprophyticus is related to production of [?] and [?]
adherent slime and urease
an enzyme that hydrolyzes urea in urine
resulting in the formation of ammonia and ammonium carbonate - making the urine alkaline and favoring bacterial growth
urease
found free-living in the environment including air, soil, various extreme
environments and food
Micrococcus species
Micrococcus species are considered part of the normal microbiota of the
skin, mucosa, and oropharynx
mode of transmission is still uncertain, and they are rarely implicated in human infections
Micrococcus species
When infections occur, particularly in hosts with compromised immune systems, such as HIV patients, they likely involve
endogenous strains (those that are part of the host’s normal flora).
are not generally identified to species level in clinical laboratories because they are rarely clinically significant.
Micrococci
Micrococci typically appear as gram-positive cocci in [?], rather than in clusters and usually larger than staphylococci
tetrads
Some micrococci are pigmented bacteria;
produces yellow colonies
produces reddish colonies
M. luteus
M. roseus
The yellow colonies of [?] may
be mistaken for the pigmented colonies of S. aureus.
M. luteus
