Staphylococcus

Staphylococcus
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For B.Sc Optometry Students

• Gram-positive bacteria, 1μm in diameter
• Under the microscope, they appear round (cocci), and form in grape-
like clusters
• Nonmotile and Nonspore forming
Staphylococcus – Structure

• Coagulase positive
• Coagulase negative
• S. aureus and S. intermedius are
coagulase positive. All other
staphylococci are coagulase
negative. They are salt tolerant
• often hemolytic - destruction of
red blood cells which leads to the
release of hemoglobin from
within the red blood cells into
the blood plasma.
• Common pathogen eg: S. aureus
• Opportunistic pathogen eg: S. epidermidis
• Non - pathogen eg: S. hominis
Staphylococcus – Classifications

S. aureus to grow, producing yellow-colored colonies
as a result of mannitol fermentation when grown in
mannitol salt agar and subsequent drop in the
medium's pH
Staphylococcus – Culture

Yellow colonies of S. aureus on a blood agar plate,
note regions of clearing around colonies caused by
lysis of red cells in the agar - beta hemolysis
Staphylococcus – Culture

Toxins
Exotoxins Superantigens
Epidermolytic
(exfoliative)
toxin
Staphylococcus – Pathogenicity

Exotoxins
• The Alpha -toxin
is a heterogeneous protein that acts on a broad spectrum of eukaryotic
cell membranes. The alpha-toxin is a potent hemolysin.
• The Beta-toxin
degrades sphingomyelin and therefore is toxic for many kinds of cells,
including human red blood cells.
• The Delta-toxin
is heterogeneous and dissociates into subunits in non ionic detergents.
It disrupts biologic membranes and may have a role in S aureus
diarrheal diseases.
Staphylococcus – Pathogenicity - Toxins

Exotoxins
• The gamma hemolysin and leukocidin
The γ-toxin and the leukocidins are two-component protein
toxins that damage membranes of susceptible cells. The proteins
are expressed separately but act together to damage
membranes.
Leukocidin toxin of S. aureus has two components. It can kill WBC of
humans and rabbits. The two components act synergistically on the
WBC membrane. This toxin is an important virulence factor in
community associated methicillin resistant S. aureus infections

Super antigens
Enterotoxins
(A, B, C, D, E and G)
• cause diarrhea and vomiting when
ingested
• responsible for staphylococcal food
poisoning
• When expressed systemically,
enterotoxins can cause toxic shock
syndrome (TSS)
Toxic Shock Syndrome Toxin
(TSST-1)
• very weakly related to
enterotoxins and does not have
emetic activity.
• TSST-1 is responsible for 75% of
TSS
S. aureus can express two different types of toxin with superantigen
activity

What is toxic shock syndrome (TSS)
• a life threatening condition caused by bacterial toxins.
Symptoms may include fever, rash, skin peeling, and low
blood pressure, which can rapidly progress to stupor, coma,
and multiple organ failure
• TSS is caused by bacteria of either the Streptococcus
pyogenes or Staphylococcus aureus type
• Antibiotic treatment should cover both S. pyogenes and S.
aureus. This may include a combination of cephalosporins,
penicillins or vancomycin. The addition of clindamycin or
gentamicin reduces toxin production and mortality.

What is toxic shock syndrome (TSS)
Surgery may be necessary to remove
nonliving tissue (debridement) from the
site of infection or to drain the infection

How TSS
causes?
SA (Super antigens) stimulate T cells non-specifically without normal antigenic
recognition. Up to 1 in 5 T cells may be activated, whereas only 1 in 10,000 are
stimulated during antigen presentation. Cytokines are released in large
amounts, causing the symptoms of TSS. SA bind directly to class II MHC of
antigen-presenting cells outside the conventional antigen-binding grove. This
complex recognizes only the Vβ element of the T cell receptor. Thus any T cell
with the appropriate Vβ element can be stimulated, whereas normally antigen
specificity is also required in binding.

Epidermolytic (exfoliative) toxin
• causes the scalded skin
syndrome in neonates, with
widespread blistering and loss of
the epidermis.
• two distinct forms - ETA and ETB
• have esterase activity
• the toxins target a very specific
protein which is involved in
maintaining the integrity of the
epidermis.

Acute bacterial conjunctivitis
• primary due to
Staphylococcus aureus,
Streptococcus pneumoniae,
and Haemophilus influenzae.
• Other pathogens responsible
for acute disease are
Pseudomonas aeruginosa,
Moraxella lacunata,
Streptococcus viridans, and
Proteus mirabilis.
• may be spread from hand to
eye contact or through
adjacent mucosal tissues
colonization such as nasal or
sinus mucosa.
Staphylococcus – Eye Infections

Risk Factors
• Since these bacteria are usually spread from other infected inviduals,
poor hygenic habits may increase the risk of infection
• Poor contact lens hygiene
• Contaminated cosmetics
• Crowded living or social conditions
• Ocular diseases including dry eye, blepharitis, and anatomic
abnormalities of the ocular surface and lids
• Recent ocular surgery, exposed sutures or ocular foreign bodies
• Chronic use of topical medications
• Immune compromise
• Neonates are at particularly high risk for conjunctivitis

Symptoms
• Red eye: Either unilateral,
bilateral, or sequentially bilateral
• Discharge: Classically purulent,
but may be thin or thick muco-
purulent or watery
• Irritation, burning, stinging,
discomfort
• Tearing
• Light sensitivity
• Intolerance to contact lens
• Fluctuating or decreased vision
Signs
• Bulbar conjunctival injection
• Palpebral conjunctival papillary
reaction
• Muco-purulent or watery
discharge
• Chemosis
• Lid erythema

Diagnostic procedures
• Gram stain & Cultures: Primarily used in cases of
atypical conjunctivitis such as hyperacute or
chronic/non-responding. Also important in neonatal.
• There has not been a role for these tests in routine
cases due to the cost and high likelihood of success with
either empiric treatment or observation
• RPS Adeno Detector: May be used to establish diagnosis
of viral conjunctivitis instead of bacterial

• RPS Adeno Detector:

Viral and bacterial conjunctivitis :
How to differentiate?
• The gold standard for differentiation is bacterial and/or
viral cultures
• The signs on ophthalmic exam which suggest viral over
acute bacterial are as follows:
• Follicular reaction
• Watery discharge
• Itchy eyes
• Concurrent pharyngitis, fever, and upper respiratory infection

Viral and bacterial conjunctivitis :
How to differentiate?
These were a history of prior conjunctivitis and itchiness,
which both predicted viral conjunctivitis
"gluing" of the eyelids in the morning, which predicted
bacterial conjunctivitis.
Purulence of secretions was not significant.

Medical therapy
• Fluoroquinolones:
• Ciprofloxacin 0.3% drops or ointment, or Ofloxacin 0.3% drops
• Levofloxacin 0.5% drops
• Moxifloxacin 0.5% drops, Gatifloxacin 0.5% drops, or Besifloxacin 0.6% drops
• Aminoglycosides:
• Tobramycin 0.3% drops
• Gentamicin 0.3% drops
• Macrolides:
• Erythromycin 0.5% ointment
• Azithromycin 1% solution
• Other
• Bacitracin ointment
• Bacitracin/Polymixin B ointment
• Neomycin/Polymixin B/Bacitracin
• Neomycin/Polymixin B/gramicidin
• Polymixin B/Trimethoprim
• Sulfacetamide
• Chloramphenicol

Staphylococcus
Eye Infections:
Bacterial Keratitis

Bacterial Keratitis/Corneal Ulcers
• an infection of the cornea
that is caused by bacteria.
• It can affect contact lens
wearers, and also
sometimes people who
do not wear contact
lenses.
• Types of bacteria that
commonly cause bacterial
keratitis include:
Pseudomonas aeruginosa
Staphylococcus aureus
Streptococcus
pneumoniae

Bacterial Keratitis /Corneal Ulcers
Risk Factors
• The most common risk factor for bacterial keratitis is
contact lens wear.
• Contact lens wear has been associated with 19%-42%
of cases.
• Overnight wear and inadequate lens disinfection
• Other predisposing factors include:
• trauma - including foreign bodies and chemical and thermal
injuries
• contaminated ocular solutions
• immune suppression,
• corneal edema.

Symptoms
• rapid onset of ocular pain
• redness
• Photophobia
• Discharge
• decreased vision
Signs
• conjunctival injection and
focal white infiltrates
• corneal thinning
• stromal edema
• inflammatory plaque
• Descemet’s folds
• mucopurulent discharge,
• Upper eyelid edema may be
present in some cases.

Diagnostic procedures
• Corneal scrapings for smears and cultures
• Small infiltrates that do not stain may sometimes be
treated with broad spectrum antibiotics without scraping.
Laboratory test
• Culture of all ulcers should be considered before
antimicrobial therapy.
• Gram and Giemsa staining of corneal smears
• Cultures might also provide helpful information about an
organism's sensitivity to antibiotics.

Medical therapy
• Topical broad spectrum antibiotic therapy
• fluoroquinolone drops
• gentamicin
• vancomycin
• Cornea transplantation may needed for advanced
infections

Staphylococcus
Eye Infections:
Periorbital Cellulitis

• an infection of the tissues
around the eye.
• Cellulitis of the eyelid causes
redness and painful swelling
of your eyelid and the skin
surrounding your eyes.
• can cause permanent vision
problems or total blindness.
It’s important to treat
cellulitis of the eyelid right
away to prevent
complications.

• The bacteria that most
commonly cause this
condition are:
• Haemophilus influenzae
• Staphylococcus
• Streptococcus
• If left untreated it can lead
to orbital cellulitis causing
permanent vision problems
• In orbital cellulitis the tissue
behind the eye swells due
to infection; can cause
permanent visual damage.

Symptoms and Signs
• Infection is most common in the lower extremities.
Cellulitis is typically unilateral
• local erythema and tenderness
• The skin is hot, red, and edematous, often with
surface appearance resembling the skin of an orange

Diagnosis
• Examination
• Blood cultures
• Sometime microbial cultures and gram staining
• Diagnosis is by examination
Medical therapy
• oral antibiotics, including amoxicillin and dicloxacillin.

Staphylococcus
Eye Infections:
Endophthalmitis

Endophthalmitis
• a purulent inflammation of
the intraocular fluids
(vitreous and aqueous)
usually due to infection.
• one usually finds a history
of recent intraocular
surgery or penetrating
ocular trauma

Endophthalmitis
• Hypopyon is a medical condition involving inflammatory
cells in the anterior chamber of the eye.
• usually accompanied by
• severe pain
• loss of vision
• redness of the conjunctiva
• the underlying episclera
• Staphylococcus aureus
• S. epidermidis
• Streptococcus pneumoniae
• Pseudomonas aeruginosa

Endophthalmitis
Symptoms
• Hypopyon is a medical condition involving inflammatory
cells in the anterior chamber of the eye.
• usually accompanied by
• severe pain
• loss of vision
• redness of the conjunctiva
• the underlying episclera
• Staphylococcus aureus
• S. epidermidis
• Streptococcus pneumoniae
• Pseudomonas aeruginosa

Endophthalmitis
Prevention
• antibiotic eye drops (levofloxacin or chloramphenicol)
with antibiotic injections (cefuroxime or penicillin)
probably lowers the chance of endophthalmitis after
surgery

Endophthalmitis/ PPV
Treatment
• Pars plana vitrectomy (PPV) is a surgical procedure
that involves removal of vitreous gel from the eye.
• The procedure derives it name from the fact that
vitreous is removed (i.e. vitreous + ectomy = removal
of vitreous)
• the instruments are introduced into the eye through
the pars plana.

Endophthalmitis/ PPV

Endophthalmitis/Antibiotics
Treatment
• Vancomycin
• Ceftazidime
• Amikacin for Penicillin (PCN)
• fluoroquinolones

Other
Staphylococcus
Infections

Other Infections
Skin infections
• Boils: a pocket of pus that develops in a hair follicle or
oil gland. The skin over the infected area usually
becomes red and swollen.
• occur most often under the arms or around the groin
or buttocks.
• Impetigo: often painful rash can be caused by staph
bacteria. large blisters that may ooze fluid and
develop a honey-colored crust.
• Cellulitis: an infection of the deeper layers of skin
• Staphylococcal scalded skin syndrome.
Staphylococcus – Other Infections

Other Infections
Septic arthritis
• The bacteria often target the knees, shoulders, hips, and
fingers or toes.
• Joint swelling
• Severe pain in the affected joint
• Fever
Septicemia
• Also known as blood poisoning,
• occurs when staph bacteria enter a person's bloodstream.
A fever and low blood pressure are signs of septicemia.
• Internal organs, such as your brain, heart or lungs
• Bones and muscles
• Surgically implanted devices, such as artificial joints or cardiac
pacemakers

Diagnosis
• begins with attempting to culture the bacteria from an infected site.
Any area with pus, crusty drainage, or blisters should be cultured.
• Blood from patients with sepsis, toxic shock syndrome, or
pneumonia should be cultured.
• Standard microbiological techniques include a positive coagulase test
to identify staph.
• S. aureus lyses red blood cells in blood agar plates (hemolytic staph)
while S. epidermidis does not (nonhemolytic staph).
• All staph should be further tested to see if the bacteria are resistant
to the antibiotic methicillin (and other antibiotics) and thus
determine if the organisms are MRSA. This test is important as MRSA
organisms are resistant to many antibiotics usually prescribed for
staph infections.

Treatment
• Based on antibiotic sensitivity test antibiotics are
chosen
• Penicillin is commonly used
• If the staph is resistant to Methicillin new antibiotics
like Vancomycin is recommended

Staphylococcus

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