LEC MOD 4: UNIT 1 Flashcards
Staphylococcus species are classified in the family
Staphylococcaceae
How many species and subspecies are within the genus staphylococci
45 species and 21 subspecies
what type of staphylococci are seen frequently in human infections
- the coagulase-positive Staphylococcus aureus
- two coagulase-negative species, S. epidermidis and S. saprophyticus
causes an infectious dermatitis in swine
S. hyicus
causes infections in swine, cattle, and goat
S. chromogenes
has been isolated from several types of infections in dogs.
S. intermedius
cause infectious processes in dolphins, domesticated cats, dogs, and sea otters, respectively
S. delphini, S. felis, S. schleiferi subsp. coagulans, and S. lutrae
cause external otitis in dogs
S. schleiferi subsp coagulans
Most staphylococci are not environmental. T or F
False
Gram-positive cocci
general characteristic of the staphylococci
0.5 - 1.5 um in diameter, and typically in grape-like clusters.
general characteristic of the staphylococci
non-motile
general characteristic of the staphylococci
non-spore-forming
general characteristic of the staphylococci
facultative anaerobes
general characteristic of the staphylococci
Grow most rapidly at 37°C
general characteristic of the staphylococci
halotolerant
general characteristic of the staphylococci
catalase (+)
general characteristic of the staphylococci
fermentative
general characteristic of the staphylococci
Nitrate reduction(+)
general characteristic of the staphylococci
- Coagulase(+)
- DNase(+)
- Mannitol fermenter
Staphylococcus aureus
habitat of staphylococcus aureus
human nose and skin
found in the anterior nares of 20% to 40% of adults
S. aureus
S. aureus is carried by healthy individuals chronically rather than intermittently. T or F
False. intermittently rather than chronically
Other sites of colonization of S. aureus
nasopharynx, perineum, the axillae, and the vagina
S. aureus on the skin are believed to be contaminants from the nose. T or F
True
Transmission of S. aureus
via contaminated hands
Staphylococcal infections are most commonly acquired endogenously from
- colonized anterior nares
- by direct contact with someone carrying S. aureus.
how do staphylococcal infections transmit via nasal site
-the bacteria are shed to the exposed skin and clothing of the carrier and others with whom they are in direct
contact
-Spread is augmented by touching the face and, of course, nose
picking
Factors which may predispose an individual to serious S. aureus infections
-breaks in the continuity and integrity of mucosal and cutaneous surfaces.
-presence of foreign bodies or implants (e.g., sutures, intravenous lines,
prosthetic devices).
-prior infection with other agents, particularly viruses (e.g., influenza).
-underlying diseases with defects in cellular or humoral immunity, either
congenital or acquired, (e.g. defects in leukocyte chemotaxis, defects in
opsonization by antibodies, hypogammaglobulinemias or complement
component deficiencies and/or defects).
-chronic underlying diseases such as malignancy, alcoholism, and heart
disease.
-therapeutic or prophylactic antimicrobial administration
how do staphylococcal infections occur on the skin
through:
- wounds
- follicles
- skin glands
characteristics of Staphylococcal infections of the skin
- pyogenic (pus-forming)
- often presents as an inflamed, fibrous lesion enclosing a core of pus called an abscess
a mild inflammation of the superficial dermis that is restricted to ostia
(opening) 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 / sty
Hidradenitis suppurativa is a chronic or relapsing inflammatory disease of the skin, involving
apocrine gland-bearing areas
- axillae
- groin
- perinea (perineum - an area between the thighs)
- perianal regions
This condition is characterized by presence of multiple lesions
associated with blocked and infected apocrine sweat glands
Hidradenitis suppurativa
In Hidradenitis suppurativa, local pain, swelling and erythema are absent, while systemic symptoms such as fever is usually present. T or F
False. local pain, swelling and erythema are present, systemic symptoms
such as fever is usually absent.
a deeper-seated infection of the hair follicles
furuncle or boil
latin term = furunculus - little thief
It results when the inflammation of single hair
follicle or sebaceous gland progresses into a
large, red, extremely tender abscess or pustule.
furuncle
furuncle in clusters
furunculosis
where do furuncles often appear in clusters
- buttock
- breasts
- axillae
- back of the neck where skin rubs other skin or clothing
a larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles
carbuncle
-latin term = carbunculus - little coal
They are extremely painful and can even be fatal in elderly patients when they give rise to systemic disease
carbuncle
carbuncle is usually found in areas of which thin skin such as on the
back of the neck. T or F
False. Thick skin
a staphylococcal skin infection that is not
confined to follicles and skin glands.
impetigo
-latin term = impetus - to attack
is characterized by bubble-like epidermal sweeping that can break and peel away like a localized form of scalded skin syndrome
impetigo
impetigo occurs in two forms:
non-bullous and bullous
furuncle is usually present on exposed areas,
especially the face, and may spread to surrounding areas by
autoinoculation. T or F
False. impetigo
a type of transmission wherein the infected person himself infects other sites of his body
autoinoculation
begins as a single red macule (patch) or papule that quickly becomes a vesicle.
non-bullous impetigo
in non-bullous impetigo, the vesicle rupture and
forms an erosion, and the lesion and its
contents dry to form a characteristic
honey-colored crusts with erythematous
(reddish) margins that may be pruritic
(itchy). T or F
True
a localized form of staphylococcal scalded skin syndrome that
commonly affects neonates but can also occur in older children and adults
bullous impetigo
a localized form of staphylococcal scalded skin syndrome that
common affects neonates but can also occur in older children and adults
bullous impetigo
Bullous impetigo is usually found in moist,
intertriginous areas (e.g., the diaper area,
axillae, neck folds). T or F
True
in bullous impetigo, superficial vesicles progress to enlarging bullae (singular; bulla plural; vesicle or blister) with sharp margins with no surrounding erythema. T or F
True
What form of impetigo is characterized by honey-colored crusts?
non-bullous impetigo
what form of impetigo is characterized by yellow crust?
bullous impetigo
S. aureus can present itself as a _________ and cause toxigenic diseases
toxemia
-due to the production of toxins
a gastrointestinal illness caused by eating foods contaminated with toxins produced by the S. aureus
Staphylococcal food poisoning
staphylococcal food poisoning is considered a food-borne infection rather than a food intoxication. T or F
False. It is considered as a food intoxication because the food is not the cause of food poisoning, it is due to the fact that the food is contaminated with toxins
Staphylococcal food poisoning is characterized by acute symptoms that appear in ___________
2 to 6 hours after ingestion of the toxin-contaminated food
Recovery from staphylococcal food poisoning is usually _____
within 24 hrs
Symptoms of staphylococcal food poisoning
- emesis (vomiting), often projectile
- diarrhea is less frequent
Staphylococcal food poisoning is due to the ingestion of viable S. aureus cells. T or F
False
Staphylococcal food poisoning is associated with eating foods such as
custards, sauces, cream pastries, processed meats, chicken salad, or ham that have been contaminated by handling and then left unrefrigerated for a few hours.
S. aureus has high salt tolerance. T or F
True
Also known as Ritter’s Disease
Staphylococcal Scalded Skin Syndrome (SSSS)
Ritter’s disease or SSSS is usually seen in __________
- neonates (newborns/children less than 1 month old)
- infants less than 5 years
characterized by
- widespread erythema
- appearance of bullous lesions over large areas of the body
- subsequent sloughing of the superficial skin layers
Ritter’s disease or Staphylococcal Scalded Skin Syndrome
Ritter’s disease is similar to ______________. However, their only difference is that the latter is localized.
Bullous impetigo
Ritter’s disease leads to the exposure of large areas of
denuded ( stripped off surface layers) and raw skin. T or F
True
In ritter’s disease, desquamation occurs and symptoms wane over _____
5-7 days
initially a flu-like illness characterized by fever, hypotension, and rash on the skin that resembles a sunburn
Staphylococcal Toxic Shock Syndrome (TSS)
Staphylococcal Toxic Shock Syndrome only involves certain regions of the body. T or F
False. It can involve any region of the body (lips, mouth, eyes, palms, and soles)
In patients who survive the initial phase of the infection (TSS), the rash is
followed by desquamation _______________ after onset
1-2 weeks
Staphylococcal Toxic Shock Syndrome (TSS) involves only 1 organ system. T or F
False.
There is the involvement of multiple (three or more) organ systems with varying symptoms of vomiting, diarrhea, renal failure, headache, chills, sore throat and conjunctivitis
TSS was noted most frequently in men. T or F
False.
-the disease was noted most frequently in women, with onset mainly occurring during menstruation (use of high-absorbancy tampons)
non-menstrual-associated TSS is reported in males and females as _________
complication of staphylococcal abscesses or systemic infections
Most systemic staphylococcal infections have an irregular pattern. T or F
False.
Most systemic staphylococcal infections have a focal pattern,
spreading from a local cutaneous infection to other sites.
Example of miscellaneous systemic infections
- osteomyelitis (bone infection)
- pneumonia (usually occurs after influenza viral infection)
- bacteremia (with consequences such as endocarditis, arthritis, and meningitis)
Virulence Factors of S. aureus
- Protein A
- Microcapsule
- Catalase
- Coagulase
- DNase
- Hyaluronidase
- Lipase
- Staphylokinase
- B-lactamase
- Leukocidin
- Hemolysins
- Exfoliative toxin
- TSS toxin
- Enterotoxin A-E
Microcapsule among most S. aureus strains of clinical importance consists of _______
polysaccharides
This has been called microcapsule because ______
it can be visualized only by electron microscopy unlike the true capsules of some bacteria which are readily visualized by light microscopy
It mediates the attachment of S. aureus to host cells or tissues
microcapsule
It inhibits phagocytosis by polymorphonuclear leukocytes
unless specific antibodies are present
microcapsule
How many serotypes of microcapsules have been identified
11
- types 5 and 8 responsible for the majority of infections
How many serotypes of microcapsules have been identified
11
- types 5 and 8 responsible for the majority of infections
a bacterial surface protein in some S. aureus strains
Protein A
Protein A binds to the _____ portion of _____
Fc; IgG
protein A binds to the Fc portion of IgG,
leaving the IgG no longer capable of binding to Fc
receptor on phagocytes, thus preventing
opsonization
protein A also blocks
complement fixation
inactivates toxic hydrogen peroxide and free radicals formed by the
myloperoxidase system within the phagocytic cells
catalase
the primary killing mechanisms within the phagolysosome.
myloperoxidase system
promotes conversion of fibrinogen to fibrin causing plasma to clot
coagulase
function of fibrin
fibrin protects bacterial cells from PHAGOCYTOSIS and IMMUNE RESPONSE by hiding their antigenic surface
hydrolyze DNA
Deoxyribonuclease (DNase)
This 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
hydrolyzes lipids and help the spread of the organism in cutaneous and
subcutaneous tissues
lipase
plasminogen activator
staphylokinase
This factor dissolves fibrin clot (a
fibrinolysin).
staphylokinase
affects tissues of the host making
them more susceptible to damage and destruction during complement activation
Phosphatidylinositol-specific phospholipase C
under plasmid-control transmitted by transduction and perhaps
also by conjugation
B-lactamase
provides resistance to β-lactam antibiotics such as
penicillin, penicillin derivatives, and cephalosporins
B-lactamase
penicillin derivatives
penams
penicillin, penicillin derivatives, and cephalosporins all have a common element in their molecular structure
four-atom ring known as (B-lactam)
the β-lactamase breaks the β-lactam ring
open, deactivating the molecule’s antibacterial properties through
hydrolysis
a specific type of β-lactamase, showing specificity for penicillins
penicillinase
These lyse red blood cells by disrupting their cell membranes.
Hemolysins
these damage cell membranes of neutrophils and macrophages, causing
them to lyse
Leukocidins
what are the two blood cell toxins
hemolysins leukocidins
This toxins probably help incapacitate the host’s phagocytic line of
defense
Blood Cell toxins
heterogeneous protein that facilitates formation
of pores on the target eukaryotic cell membrane
a-hemolysin
a-hemolyisin facilitates formation of pores on the target eukaryotic cell membrane through which monovalent cations can pass, leading to
osmotic swelling and rupture of the cell
effects of a-hemolysin
-lyses red blood cells
-damages:
>monocytes
>macrophages
>lymphocytes
>skeletal muscle
>heart
>renal tissue
a-hemolysin may contribute to ____________ during S. aureus bacteremia
septic thrombotic events
a sphingomyelinase that degrades sphingomyelin in the cell membrane and therefore is toxic for many kinds of cells
B-hemolysin
a protein exotoxin described as a “hot-cold” hemolysin
B-hemolysin
what bacteria encodes B-hemolysin toxin
lysogenic bacteriophage
B-hemolysin hemolytic properties are enhanced by
subsequent exposure to red blood cells to low temperatures.
B-hemolysin is cytotoxic to
human erythrocytes and monocytes
B-hemolysin is inactive against
- granulocytes
- lymphocytes
- fibroblasts
cell death caused by B-hemolysin results from
disruption of host cell
plasma membrane fluidity
a small peptide that acts primarily as a
surfactant or a detergent-like molecule
delta-hemolysin
interacts with cell membranes and forms channels resulting in slow leakage of cellular contents. It may have a role in S. aureus diarrheal diseases.
delta-hemolysin
a leukocidin that lyses white blood cells and is
composed of two proteins
gamma-hemolysin
two proteins of gamma-hemolysin
S and F
It is capable of efficiently lysing white blood cells by causing pore formation in the cellular membranes that increase cation permeability.
gamma-hemolysin
the cells affected by gamma-hemolysin undergo
- degranulation of cytoplasm
- cell swelling
- lysis
gamma-hemolysin causes massive release of inflammatory mediators which are responsible for necrosis and severe inflammation
True
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)
