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BACTERIAL SKIN INFECTIONS
Yeditepe University
School Of Medicine
Dermatology Department
MD. Ozlem Akın
Folliculitis
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Bacterial skin infection of the hair follicles
Thin-walled pustules at the follicle orifices
S. aureus is the most frequent cause
Infection may secondarily arise in scratches,
insect bites, or other skin injuries
• Favorite locations extremities, scalp, face,
eyelashes, axillae, pubis and thighs
Folliculitis
• Treatment
– Cleansing of the affected areas with
antibacterial soap and water three times daily
– Mupirocin ointment topically
– If it fails a first generation cephalosporin, or a
penicillinase resistant penicillin (oxacillin,
cloxacillin, or dicloxacillin)
Furuncle
• infection of the pilosebaceous unit, therefore is
more extensive than a folliculitis because the
infection also involves the sebaceous gland
• frequently occurs on the neck, face, armpits, and
buttocks
• begins as a small, tender, red nodule that becomes
painful and fluctuant. Frequently, pus will
spontaneously drain, and often the furuncle will
resolve on its own
Furuncle
• Predisposing factors:
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Obesity
Alcoholism
Malnutrition
Disorders of neutrophil function
Blood disorders
Iatrogenic or other immunosuppression, including AIDS
Diabetes
Atopic dermatitis
Irritation
Pressure
Friction
Hyperhidrosis
Shaving
Furuncle
• Treatment:
– Warm compressess
– Incision and drainage (when the furuncle has become
localized and shows definite fluctuation)
– Penicillinase-resistant penicillin or a first generation
cephalosporin 1-2 g/day
– Methicillin-resistant and even vancomycin resistant
strains occur. In unresponsive patients antibiotic
resistant strains should be suspected and sensitivities
should be checked.
– Mupirocin cream to anterior nares daily for 5 days
Carbuncle
• collection of multiple infected haif follicles
• an abscess, just like a furuncle, but a much more serious
infection
• Whereas a furuncle is an infection of a hair follicle and the
surrounding tissue, a carbuncle is actually several
furuncles that are densely packed together.
• usually extends into the deeper layers of the skin - the
subcutaneous fat
• forms into a broad, red, hot, painful nodule that often
drains pus through multiple openings of the skin
• Someone who has a carbuncle likely will feel sick and
have a fever and fatigue
• tend to occur in areas with thicker skin like the nape of the
neck, the back, or the thighs
Carbuncle
• Diagnosis
– diagnosed based on their typical appearance, but
sometimes they can be confused with a ruptured
epidermoid cyst
– There aren't any tests that are performed to decide if an
infection is a carbuncle, but often the pus inside the
carbuncle is tested with a gram stain or bacterial culture
to determine if the bacteria causing the infection is a
typical Staphylococcus aureus or one that is resistant to
the usual penicillin-type antibiotics
Carbuncle
• Because usually contain a significant amount of
pus, they are usually first treated with a procedure
called incision and drainage draining the pus and
allowing the infection to heal from the inside out.
• Carbuncles are typically caused by the bacteria,
Staphylococcus aureus. The usual medications
used to treat Staph infections include the
antibiotics dicloxacillin or cephalexin.
• Unfortunately, there is a new strain of Staph
bacteria that is resistent to these antibiotics.
Carbuncles Caused by Methacillin
Resistant Staphylococcus Aureus
(MRSA)
• In the past several years, there has been a sharp increase in
the incidence of infections caused by a special strain of S.
aureus that is resistant to the normal penicillin-based
treatment.
• Until recently, MRSA was an uncommon bacterial strain
that occurred in nursing homes and other long-term care
facilities. But with the overuse of antibiotics for conditions
that don't require antibiotics, MRSA infections are
common
• These infections often occur spontaneously in the groin,
buttock, and upper thigh region. Currently, there are
antibiotics that do treat this resistant strain. The antibiotic
of choice for MRSA infections that were not acquired from
a hospital or long-term care facility is trimethoprimsulfamethoxazole. The next option is clindamycin,
especially for people who are allergic to sulfa.
Cellulitis
• bacterial infection of the deeper layers of the skin,
the dermis and the subcutaneous tissue.
• In adults and children, most often caused by
Streptococcus and Staphylococcus Aureus
• Sometimes Haemophilus influenzae type B can
cause cellulitis in children younger than 3, but this
has become less common since we've been
vaccinating against this bacteria.
• Knowing the type of bacteria that commonly
cause cellulitis helps doctors determine the best
antibiotic to treat the infection.
Cellulitis
• Bacteria are able to cause an infection if they can get into
the skin through a break in the skin barrier (cuts, scrapes,
ulcers, and surgical wounds)
• Unfortunately, can also develop in skin that appears
perfectly normal
• Repeated infections often happen in areas where there is
damage to the blood or lymph vessels that circulate fluid
throughout the body. This damage can be caused by prior
cellulitis infections, surgical removal of lymph nodes,
removal of veins for vein grafts somewhere else in the
body, and radiation to the area.
Cellulitis
• Before skin changes occur, someone with cellulitis
can have fever, chills, and fatigue.
• The skin infection is usually red, swollen, warm to
touch, and painful.
• It's often difficult to tell exactly where the border
is between normal and infected skin.
• Red streaks coming out of the area and swollen
lymph nodes can sometimes occur.
• Children often get cellulitis on the head and neck,
and adults often get cellulitis on the arms or legs.
Cellulitis
• Diagnosis
– usually diagnosed based on its typical appearance.
– blood count
– blood cultures
– A cellulitis infection doesn't have pus that could be
cultured to see what bacteria are involved.
– Sometimes a doctor might do an "aspirate" which
involves injecting sterile fluid into the infected tissue
and drawing it back out, hoping that some of the
bacteria get washed into the fluid. This fluid is then
cultured to see what bacteria grow.
– An aspirate is usually done in unusual situations where
there is a high chance that the infection is caused by a
different bacteria than expected.
Cellulitis
• Treatment
– Most infections require 10 days of an oral antibiotic. If
the infection is on an arm or especially a leg, elevating
the extremity often speeds healing.
– IV antibiotics might be used in more severe cases such
as:
– Cellulitis of the face
– Someone who is seriously ill
– Infections in people who are immunocompromised
– Infections that didn't improve or got worse with oral
antibiotics
Cellulitis
• Prevention
– The best prevention is taking good care of any
break in the skin. This can be done by:
– Washing the wound daily with soap and water
– Applying a topical antibiotic to the wound
– Keeping it covered with a bandage to keep it
clean
– Changing the bandage every day or more often
if the bandage gets dirty or wet
Erysipelas
• a superficial infection of the skin, which typically
involves the lymphatic system
• most often caused by Group A Streptococcus
• In a few cases, it can be caused by other types of
Streptococcus or Staphylococcus bacteria
• Some cases of erysipelas have an inciting wound
such as trauma, an abrasion, or some other break
in the skin that precede the fiery infection
• However, in most cases, no break in the skin can
be found
Erysipelas
• was previously found mainly on the face
• However, now it is seen most commonly on the lower
extremities
• tends to occur in areas where the lymphatic system is
obstructed
• A cluster of symptoms (fever, chills, fatigue, anorexia, and
vomiting) typically precede the appearance of the rash by 4
to 48 hours
• The rash then quickly appears as a bright red, hot, swollen,
shiny patch that has clearly defined borders
• The consistency of the rash is similar to an orange peel,
also known as "peau d'orange"
Erysipelas
• Diagnosis
– mainly by the appearance of the rash
– Blood tests and skin biopsies generally do not help
make the diagnosis
– In the past, saline solution was injected into the edge of
the rash, aspirated back out, and cultured for bacteria.
This method of diagnosis is not used anymore because
bacteria were not found in the majority of cases
– If the preceding symptoms such as fever and fatigue are
significant enough, sometimes blood is drawn and
cultured for bacteria to rule out sepsis.
Erysipelas
• Treatment
– A variety of antibiotics can be used including
penicillin, dicloxacillin, cephalosporins,
clindamycin, and erythromycin
– Most cases can be treated with oral antibiotics
– However, cases of sepsis, or infections that do
not improve with oral antibiotics require IV
antibiotics administered in the hospital.
Erysipelas
• Recurrence of Erysipelas
– Even after appropriate treatment with antibiotics, can
recur in 18% to 30% of cases
– People who are susceptible to recurrence are those with
compromised immune systems or compromised
lymphatic systems
– Because erysipelas can damage the lymphatic system,
the infection itself can be a setup for recurrence
– Some people with recurrent infections must be treated
daily with low-dose antibiotics as a prevention of
further infections.
Impetigo
• a common bacterial infection of the upper layers
of the skin caused by Streptococcus pyogenes and
Staphylococcus aureus
• highly contagious and usually treated with a
topical antibiotic
• In industrialized countries most cases are caused
by Staphylococcus aureus, but in developing
countries Streptococcus pyogenes is the main
causitive agent.
• Mixed infections caused by both bacteria are
common
Impetigo
• tends to occur in areas of minor breaks in
the skin such as insect bites, cuts, or
abrasions
• can also occur in breaks in the skin caused
by skin conditions such as eczema, scabies,
herpes, chickenpox, pediculosis capitis or
contact dermatitis
Impetigo
• common contributing factors:
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Warm, humid climate or environment
Traumatized skin
Poor hygiene
Overcrowding
Nasal colonization with bacteria
Impetigo
• Clinical findings
• classified as bullous or non-bullous
• both types have a distinct appearance and
cause
Impetigo
• Non-Bullous Impetigo
– More common - 70% of impetigo infections
– Caused by either Streptococcus or Staphylococcus
species
– Hallmark of appearance is a thick "honey-colored"
crust
– Occurs mainly on face or limbs
– Only large lesions are painful
– Generally does not cause a fever
– Heals without scarring
Impetigo
• Bullous Impetigo
– Less common form of impetigo
– Occurs mainly in newborns and younger children
– Caused by a specific sub-group of Staphylococcus
aureus
– Blisters form in response to a toxin produced by the
bacteria
– Occurs on face, trunk, hands, and buttocks
– Generally does not cause a fever
– Heals without scarring
Impetigo
• Diagnosis
• often diagnosed clinically, based on the
characteristic appearance.
• Gram stain
• Bacterial culture
Erythrasma
• caused by Corynebacterium minutissimum
• occurs most often between the third and fourth
toes, but also frequently can be found in the groin,
armpits, and under the breasts
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Overweight people
Elderly
Diabetics
People in warm, moist climates
Erythrasma
• Clinical findings
– starts as a pink to red patch with well-defined
edges
– patch has a finely wrinkled appearance with a
very fine scale on it
– after some time, the rash fades from pink to a
uniform brown color (ddx from fungal
infections)
Erythrasma
• Differential diagnosis:
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Inverse psoriasis
Tinea cruris
Intertrigo
Seborrheic dermatitis
Candidiasis
Tinea versicolor
Lichen simplex chronicus
Erythrasma
• Diagnosis
– Wood's Lamp examination: under the UV light of a
Woods Lamp, erythrasma turns a bright coral red, but
fungal infections do not.
– Gram Stain: Unfortunately, this bacteria is difficult to
get to stick to the slide so it requires a special
technique.
– KOH Test: to confirm that there is no fungus present
– Skin Biopsy
Erythrasma
• Treatment
– Erythromycin 250 mg four times a day for 5
days
– Clarithromycin 1gm once
– The antifungal creams (clotrimazole)
– Topical antibiotics like clindamycin or
erythromycin twice a day for 2 weeks