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o ssue n ec ons

Impetigo Folliculitis Cellulitis Necrotising fasciitis Clostridial MyonecrosisCommon in children Infection of hair follicles Acute spreading inflammation

involving Epidermis, Dermis,Subcutaneous fat

Rare infectionHigh mortality (30-40%)

= Gas gangreneClostridial infection primarily of muscle tissue

Skin/ epidermis of FaceAround Mouth & Nose

Occur after exfoliating, shaving,spontaneous

Staphylococcus aureus-haemolytic streptococci

(group A S. pyogenes)(group C & G)

Surgical emergencyRadical debridement of devitalised tissue

Clostridium perfringensC. novyiC. septicumC. histolyticumC. fallaxC. bifermentans

Non-bullousStreptococcus pyogenes(group A streptococci)

honey-crust lesion

Whirlpool (hot tub/ spa)folliculitisPseudomonas aeruginosa

Crepitant anaerobic cellulitisNecrotic soft tissue infectionAbundant CT gasLack of mark systemic toxicity

Gradual onsetLess painAbsence of muscle involvement

Type 1Caused by multiple organisms(often gut origin)(synergistic gangrene)

Anaerobesy Peptostreptococcusy Bacteroidesy Fusobacterium speciesAerobicy Streptococcus group A

(Streptococcus pyogenes )y Staphylococcus aureusy E. coli

BullousStaphylococcus aureusRupture of bullae leaves a thin

varnish-like crust

Furuncle/ boilStaphylococcus aureusStaphylococcus epidermidis(CONS)

Infection occurs in areas of Major traumaSurgeryComplication of thermal burns

Can occur spontaneously byActivation of dormantclostridial spores (old scar)Bacteremic spread from GIT orGUT site

Bullous

Furuncle/ boilInflammation of hair folliclesLocalized accumulation of pus,dead tissue

Bacteroides speciesPeptostreptococcus speciesClostridium speciesEnterobacteriaceae

Type 2Caused by group A streptococci (GAS)Flesh eating bacteria

ClinicalsRapid onset of myonecrosiswithin 4-6 hours after injuryMuscle swellingSevere painGas production - crepitus SepsisExudate sweet mousy odor

ComplicationsSevere systemic toxicityHypotensionRespiratory distressMultiorgan failureClinicalSevere pain in affected areaSkin changes modest (early)Progressing to fascial & skinnecrosis & deep tissueinfarction (muscle layers)

Pathophysiologyy Clostridium soil, GITy Traumatic & Surgical gas

gangrene direct inoculationof wound

y Compromised blood supply wound has anaerobicenvironment ideal forClostridium perfringens

y Spontaneous gas gangrene caused by hematogeneousspread of C. Septicum fromGIT with colon cancer

y C. Septicum enter blood (viasmall break) in GIT mucosaand seeds muscle tissue

y C. Septicum is aerotolerant (unlike C. perfringens) caninfect normal tissues

y When sufficienct devitalizedtissue present (supportanaerobic metabolism),myonecrosis develop

Virulence factorsExtra-cellular toxinsHydrolyze cell membranesAbnormal coagulationMicrovascular thrombosisCardiodepressive effects

-toxin (lecithinase) haemolytic, histotoxic,necrotizingToxic factor produced

TreatmentAntiobiotics penicillin(interfere cell wall synthesis)Surgery - debridementHyperbaric oxygen

Non-bullous ImpetigoHoney-crust lesion

Carbuncles (cluster of boils)Boils can develop to abscess

Cellulitis

Thrombosis of subcutaneousblood vessels necrosis of skin

Initial local pain replaced bynumbness, analgesia (involvescutaenous nerves)

Most cases follow aftersurgery, minor trauma

Highest incidence small vesseldisease diabetes mellitus

FuruncleNecrotising fasciitisSkin, deep structures of neck

Necrotising fasciitisLarge, dark, boil-like blistersFlash-eating disease (GAS)

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one n ec ons

steomyelitis

Bone infected throughHaematogenous2 to contiguous focus of infection relatively normal vascularity, generalizedvascular insufficiency (eg. Diabetic foot)ChildrenLong bonesAdultsFeetVertebrae bodies lumbar, thoracicPelvisDiaphysis of long bones

Risk factorsRecent traumaDiabetesHemodialysisIV drug abuseRemoval of spleen ( risk)PathophysiologyInfection produces local cellulitis( bone pressure, pH, breakdown of leukocytes)Necrosis of boneInfection proceed laterally, through Haversian & Volkmann canal system,perforate cortex, lift periosteumExtend into intramedullary canalVascular compromiseBone necrosisCapillaries penetrate growth plate (infants)Infection spread to epiphysis & joint space

Children > 1 y/oGrowth plate no longer penetrated by capillariesEpiphysis & joint space protected from infection

AdultsGrowth plate resorbedJoint extension of metaphyseal infection can recurEtiological agentsStaphylococcus aureusStreptococcus pyogenesHaemophilus influenzae (rare, Hib vaccine)Pseudomonas aeruginosa (intravenous drug abusers vertebral osteomyelitis)

ungal osteomyelitisCoccidioidesBlastomycesCryptococcusSporothrix speciesLesion appears as cold abscess overlying OM lesionJoint space extension (occur in coccidioidomycosis & blastomycosis)TherapySurgical debridementAntifungal chemotherapy

Sporotrichosis Sporotrichosis

Acute Hematogenous OMMainly in infants, childrenAdult frequencyInfants & ChildrenMetaphysis of long bones (tibia, femur)Non anastomosing capillary ends of nutrient arteryMake sharp loops under growth plateEnter a system of large venous sinusoidsBlood flow becomes slow & turbulentObstruction to capillary endsAvascular necrosis (AVN)ClinicalLocalised bone pain

movement of affected body partSkin red, hot, swollen, pusSpasms of musclesWeight Malaise (general)

TemperatureSweat excessivelyChillsLymphadenopathyComplicationsChronic OMBone abscess (pocket of pus)Bone necrosis (bone death)Spread of infectionInflammation of soft tissue (cellulitis)Sepsis

Chronic Hematogenous OMDead areas of bone (sequestrum)Fail to respond to treatmentRecur for a long timePolymicrobial

Chronic osteomyelitis (Right great toe)Persistent swellingClosed fistulus tract (arrow)

Chronic osteomyelitisBony destruction

ManagementHospitilization, IV antibioticsLong term antibiotics (4-6 weeks or more) oral + IVPain-killing medicationSurgical debridementSkin graftsAmputationReplace with prostheticsLifestyle stop smoking to improve blood circulationTreat underlying causes - diabetes

Diabetic foot infectionFactorsMicro-angiopathy (impaired blood supply)Diabetic sensory neuropathy (impaired pain sensation)

sweet glucose (promotes bacteria growth)15X higher rate for lower extremity amputation compared to non-diabeticsDiabetic lower extremity amputationGangreneInfection

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St pto o us p o n s(GAS)

Clost idiu p f in ns St ph lo o us au us Haem ophilus Influ e nzae P se udo m on as aer u inos a

Es her i hia c oli

Inc e

e he ys s zon e Compl e

e hemol ys s zon e Blood agarSmall s ze Conve Circ larTran sluce nt coloni es Beta h emol ysis

Blood agarLarge SmoothLow con ve CircularTran sluce nt coloni es Doubl e zon e of h emol ysis (compl e te incompl et e

Blood agarMe ium size Con ve CircularWhit e colour coloni es Be ta h emol ysis

Chocol a te blood agarSmallCircularLow con ve SmoothPal e gra y Tran spar ent

Nut rie nt agarMe ium to Larg e size Low con ve coloni es Extra ce llular pigm ent(gr ee n)

Mac Con ey agarSmoothCon vexSmall to M e ium size Pink colour(la cto se f e rm e ntingcoloni es )

Gram st a in Gram +ve Cocci in chain s

Gram st a in Gram +ve BacilliSub t erminal spor e

Gram st a in Gram +ve cocciGrap e like clust ers Singl e & Pair e Cocci

Gram st a in Gram ve Pleomorphi c

Gram st a in Gram ve Bacilli

Gram st a in Gram ve Bacilli