BACTERIAL INFECTIONS OF BACTERIAL INFECTIONS OF THE SKIN AND SOFT THE SKIN AND SOFT

TISSUESTISSUES

Staphylococcal InfectionsStaphylococcal Infections

• are one of the most successful human pathogens.

• They normally colonise skin and mucous membranes and anterior nares but readily enter breaches in these natural barriers, especially if foreign material - e.g. soil, plastic cannulise, prosthetics - is present.

staphylococci were divided into

• coagulase-positive, Staph. aureus & Staph. intermedius

• coagulase-negative like Staphylococcus epidermidis S. saprophyticus

StreptococcusStaphylococcus

STAPHYLOCOCCAL INFECTIONSSTAPHYLOCOCCAL INFECTIONS Staph. aureus • is the main cause of staphylococcal infections.

Staph. intermedius • causes infection following dog bites. Staph. epidermidis • is the predominant commensal organism of the skin, • can cause severe infections in those with central venous

catheters or implanted prosthetic materials. Staph. saprophyticus is part of the normal vaginal flora and causes urinary

tract infections in sexually active young women.

Infections caused by Staphylococcus aureus.

S.aureus produces skin infectionS.aureus produces skin infection

I. Direct infection of skin and adjuscent tissues

a. Impetigo

b. Ecthyma

c. Folliculitis

d. Furunculosis

e. Carbuncle

f. Sycosis

II.Cutaneous disease due to effect of bacterial toxina. Staphylococcal scalded skin syndrome

b. Toxic shock syndrome

EcthymaEcthyma• Streptococcal & staph

• Common in children

• Small bullae or pustules on erythematous base

• Formation of adherent dry crusts

• Beneath which ulcer present with Indurated base • Heals with scar and pigmentation

• Buttocks, thighs and legs, commonly affected

FolliculitisFolliculitis

• Superficial

involving just the ostium of the hair follicle (folliculitis)

• Deep

furuncles

carbuncles.

•

Superficial folliculitisSuperficial folliculitis

• Infection of hair folliclescan

• be subacute or chronic.

• Commonly caused by staph. aureus

• Children

• Scalp & limb

• Rarely painful

• The pustules usually heal in 7-10 days but can become more

chronic

Deep folliculitisDeep folliculitis

• furuncles

• carbuncles

Furuncle (BoilFuruncle (Boil((

• Acute

• Staph. Aureus often affecting the neck, buttocks and anogenital area

• Predisposing factors include tight clothing

• Small, follicular noduler -- Pustule--necrotic--The lesions eventually

rupture to discharge pus and, because they are deep, leave a scar.

• Painful

• Constitutional symptoms

• They can progress to form a carbuncle.

CarbuncleCarbuncle

• Extensive infection of a group of contagious follicles

• Staph. aureus

• Middle or old age

• Predisposing factors

– Diabetes

– Malnutrition

– Severe generalized dermatoses

– During prolonged steroid therapy

• Painful, hard tender nodule, often on the neck, shoulders or hips

and associated with severe constitutional symptoms.

• Suppuration begins after 5-7 days

• Pus discharge from multiple follicular orificies

• Necrosis of intervening skin

• Large deep ulcer

CarbuncleCarbuncle (continue (continue((

Wound infections

• Many wound infections are caused by staphylococci

• Prevention involves paying careful attention to hand hygiene, skin preparation and aspetic technique, and the use of topical and systemic antibiotic prophylaxis.

• Treatment is by drainage of any abscesses plus adequate dosage of antistaphylococcal antibiotics.

Cannula-related infection

• Staphylococcal infection associated with cannula sepsis and thrombophlebitis

• Staphylococci have a predilection for plastic, rapidly forming a biofilm which remains as a source of bacteraemia as long as the plastic is in situ.

• cannula removal and antibiotic treatment with flucloxacillin are necessary if there is any suggestion of spreading infection.

Meticillin-resistant Staph. Aureus (MRSA(

• Resistance to meticillin, due to a penicillin-binding protein mutation, has been recognised in Staph. aureus for more than 30 years.

• The recent recognition of resistance to vancomycin/teicoplanin (glycopeptides( in either

glycopeptide intermediate Staph. aureus (GISA( vancomycin-resistant (VRSA(• MRSA is now accounting for up to 40% of

staphylococcal bacteraemia in developed countries.

• These organisms have also acquired other virulence factors such as Panton-Valentine leukocidin (PVL(, which can cause rapidly fatal infection in young people.

• Milder MRSA infections may be treated with clindamycin, tetracyclines or co-trimoxazole.

• Glycopeptides, linezolid and daptomycin are reserved for treatment of more severe infections.

)MRSA(

Injection site infection in injection drug-users

• Poor hygiene and injection techniques in injection drug-users, along with sharing unsterile equipment, often lead to skin and subcutaneous tissue sepsis.

• A diagnostic aspiration of skin lesions with appropriate microbiological investigation should be undertaken.

• In any patient with superficial staphylococcal infections, especially injection drug-users, the possibility of endocarditis must always be considered.

Staphylococcal scalded skin synotrane Staphylococcal scalded skin synotrane (Ritter’s Disease(Ritter’s Disease((

• Exotoxin of staph (Phage Group II(

• Acantholysis

• Occult staph. upper respiratory tract infection or

purulent conjunctivitis

• Infants and children

• Tender red skin

Staphylococcal scalded skin synotrane Staphylococcal scalded skin synotrane (Ritter’s Disease(Ritter’s Disease((

• Denuded skin

• Heals 7 - 14 day

• Don’t grow staph. from blister fluid

• Complication 2%

– Cellulitis

– Pneumonia

• Prognosis : Rule

Staphylococcal toxic shock syndrome (TSS(

• This serious and life-threatening disease • infection by Staph. aureus, which produces a specific

toxin (TSST1(. • commonly seen in young women associated with the

use of highly absorbent intravaginal tampons.• abrupt onset with high fever, generalised systemic

upset ,a generalised erythematous blanching rash resembling scarlet fever, and hypotension.

• It rapidly progresses over a matter of hours to multisystem involvement with cardiac, renal and hepatic compromise, leading to death in 10-20%.

• Recovery is accompanied at 7-10 days by desquamation

• The diagnosis is clinical and may be confirmed in menstrual cases by finding

of a retained tampon microbiological examination by Gram stain demonstrating

typical staphylococci. culture and demonstration of toxin production are

confirmatory.

TSS (continue(

Treatment of staph. TSS

• immediate and aggressive fluid resuscitation • intravenous antistaphylococcal antibiotic

(flucloxacillin or vancomycin(, with the addition of a protein synthesis inhibitor (e.g. clindamycin( to inhibit toxin production.

• Intravenous immunoglobulin is occasionally added in the most severe cases on the basis of efficacy in streptococcal toxic shock.

STREPTOCOCCAL INFECTIONSSTREPTOCOCCAL INFECTIONS

ßß-hemolytic streptococcus produces -hemolytic streptococcus produces skin infectionskin infection

I. Direct infection of skin or subcutaneousa. Impetigo (non bullous(

b. Ecthyma

c. Erysipelas

d. Cellulitis

e. Vulvovaginitis

f. Blistering distal dactylitis

g. Necrotizing fascitis

II. Secondary infectionEczema infection

II. Tissue damage from circulating toxin

Scarlet fever

IV. Skin lesion attributed to allergic hypersensitivity to streptococcal

antigens

E.Nodosum

Vasculitis

V. Skin disease provocated or influenced by streptococcal infection

(mechanism uncertain(

Guttate psoriasis

ß-hemolytic streptococcus produces skin infection

STREPTOCOCCAL INFECTIONSSTREPTOCOCCAL INFECTIONS

Strep. pyogenes• erysipelas, impetigo, necrotising fasciitis.• Streptococcal toxic shock syndrome • Bone and joint infection • Tonsillitis • Puerperal sepsis • Scarlet fever • Glomerulonephritis • Rheumatic fever

STREPTOCOCCAL INFECTIONSSTREPTOCOCCAL INFECTIONS

Alpha-haemolytic streptococci (Strep. mitis, sanguis, mutans, salivarius)

• Endocarditis • Septicaemia in immunosuppressed

STREPTOCOCCAL INFECTIONSSTREPTOCOCCAL INFECTIONS

Group B streptococci• Neonatal infections including meningitis • Female pelvic infections

Enterococcus faecalis• Endocarditis • Urinary tract infection

STREPTOCOCCAL INFECTIONSSTREPTOCOCCAL INFECTIONS

Anaerobic streptococci (Peptostreptococcus spp.)

• Peritonitis • Dental infections • Liver abscess • Pelvic inflammatory disease

scarlet fever

• Group A (or occasionally groups C and G) streptococci • the infecting strain produces a streptococcal pyrogenic exotoxin.

• Common in school-age children, & young adults who have contact with young children.

• A diffuse erythematous rash occurs, which blanches on pressure , classically with circumoral pallor.

• The tongue, initially coated, becomes red and swollen ('strawberry tongue‘).

• The disease lasts about 7 days, the rash disappearing in 7-10 days followed by a fine desquamation.

• Residual petechial lesions in the antecubital fossa may be seen ('Pastia's sign‘)-.

Treatment benzylpenicillin or orally penicillin

symptomatic measures

• This is associated with severe group A streptococcal skin infections producing pyogenic exotoxin A.

• Initially, an influenza-like illness occurs, in 50% of cases, signs of necrotising fasciitis.

• A faint erythematous rash, mainly on the chest, rapidly progresses to a toxic multisystem shock-like state.

• Without aggressive management, multi-organ failure will develop.

Streptococcal toxic shock syndrome

• Fluid resuscitation• parenteral antistreptococcal antibiotic

therapy, usually with benzylpenicillin and a clindamycin to inhibit toxin production.

• Intravenous immunoglobulin is usually administered in addition.

Treatment of strep. TSS

ErysipelasErysipelas

• Acute infection and imflammation of the dermal layer of skin.

• Painful red patches with raised erythematous edge which enlarge and thicken

• usually affects the face or the legs. • Treatment –

penicillin(phenoxymethylpenicillin) or erythromycin

CellulitisCellulitis

• Acute/sub-acute/chronic

• Inflammation of loose connective tissue

• Streptococcal (Group A)

• Erythematous, edematous, swelling

• Pain/tenderness

• Constitutional upset