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L8. Skin and soft tissue infections .pptx
- 1. SKIN AND SOFTTISSUE INFECTIONS DEPARTMENT OF MICROBIOLOGY AND IMMUNOLOGY Presenter: Daniel Mwandu Facilitator: Dr. Joel Manyahi Date: 20th Dec, 2023 Venue: Microbiology Lab
- 2. Presentation Outline • Introduction •Risk factor for SSTIs • Etiology • Classification • Clinical manifestation • Laboratory diagnosis • Treatment • Prevention & Control
- 3. INTRODUCTION • Skin andsoft tissue infections (SSTIs) are clinical entities of variable presentation, etiology and severity that involve microbial invasion of the layers of the skin and underlying soft tissues. • It can be caused by direct penetration or by hematogenous spread of pathogens from initial sites • SSTIs range from mild infections, such as pyoderma, to serious life-threatening infections, such as necrotizing fasciitis.
- 4. Anatomy of theSkin
- 5. RISK FACTOR FORSSTIS • Long hospital stay • Skin traumatic , Injury and open wounds • Surgical, • Skin conditions, such as athlete’s foot or eczema, • Obesity, Diabetes, • Immunodeficiency, • Certain medications.
- 6. ETIOLOGY S/no Agent Examples 01Bacteria Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus spp, Escherichia coli, Enterobacter spp, Klebsiella spp, β-Hemolytic streptococci, Proteus mirabilis, Coagulase-negative staphylococci, and Serratia spp 02 Fungi Sporothrix schenckii Blastomyces dermatitidis Histoplasma capsulatum Coccidioides immitis Scopulariopsis spp. 03 Parasites Schistosomes, Strongyloides stercoralis , Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus, Hookworms Leishmania spp and Ectoparasite( i.e. ticks, lice, scabies) 04 Viruses Paramyxovirus, Rubella virus, human parvovirus B19, Enteroviruses, Alphaviruses, poxviridae, HPV, Herpesviridae(HSV, VZV, CMV, EBV), and Hemorrhagic Fever Viruses
- 7. CLASSIFICATION The skin andsoft tissue infections, can be classified according to i. The type of skin lesion produced( superficial or deep) ii. The causative organism(bacteria, parasites ,fungi or Viruses) iii. The pathogenesis of the infection such as a primary entity or secondary to a preexisting infection or systemic manifestation).
- 8. Clinical Manifestation Dermatitis • Itis a general term that describes an inflammation of the skin. • It is characterized by areas of redness, swelling, and sometimes scaling of the skin and pruritus. • The common infectious causes of dermatitis. Intertrigo and Superficial Candidiasis
- 10. Cont.. Erythrasma • It isa superficial, chronic skin infection • Usually found in intertriginous areas • It characterized by Red or brown hyperpigmented patches of skin with scaling and central hypopigmentation. • It often occurs in men, Obesity, DM patients, and immunosuppressed. • Corynebacterium minutissimum, a skin biota, the causative organism, produce a lesions with a coral red fluorescence under a Wood lamp.
- 12. Cont.. Dermatophytosis • Dermatophytosis isan infection of the hair, skin, or nails caused by a dermatophyte • Three genus Trichophyton, Epidermophyton, and Microsporum are known causative of infection, also known as ringworm or tinea • The classic lesion of a dermatophyte infection is a circular scaly patch of erythema with a raised border. The edges are often more inflamed than the center.
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- 16. Bite Infections • Bitesfrom humans or animals can result to serious infections with a mixture of aerobic and anaerobic organisms originated from biting oral cavity and skin biota of the patient. • Dog bites are typically polymicrobial and Pasteurella, Bacteroides spp., Fusobacterium, Prevotella, staphylococci, etc • Cat teeth can inflict very deep wounds and have a greater risk of infection, soft tissue abscess formation, and infection of underlying bones and joints compared with dog bites.
- 17. • Cat bitesalso progress to infection more rapidly than dog bites. Pathogens are similar to dog with inclusion of Francisella tularensis • Human bite pathogens infections include Streptococcus anginosus group, S. aureus, Eikenella corrodens, Fusobacterium nucleatum, and Prevotella melaninogenica.
- 18. Cont.. Diabetic Foot Infections •It is a very common in DM patients; • It is risk factors including peripheral neuropathy, traumatic feet, and kidney dysfunction. • it can manifest to cellulitis, soft tissue ulceration and gangrene • Ulcerative lesions and gangrene may be is a result of mixed infections of gram positive and negative bacteria and both aerobes anaerobic bacteria. .
- 19. Necrotizing Soft TissueInfection • A necrotizing soft tissue infection is a serious, life-threatening condition. It can destroy skin, muscle, and other soft tissues. • Subtypes of necrotizing infection (infectious gangrene) include i. Type I caused by polymicrobial ii. Type II, monomicrobial usually S. pyogenes iii. Gas gangrene (type III), caused by Clostridium spp. and marine vibrios
- 20. Common viral infectionof skin
- 21. Laboratory diagnosis Specimen collection: -Propercontainer -Proper transport media -Proper storage conditions Collection technique: -deep pus swab -needle Aspirate Near skin swab Diagnosis technique: -Macroscopic -Microscopic -Culture and sensitivity Successful diagnosis
- 22. Sample • A varietyof diagnostic methods may be helpful in determining the cause of skin and soft tissue infections. • Swabs of surface wounds or skin are likely to yield colonizing or contaminating bacteria. • Therefore deep aspirates or biopsies are recommended. • Other specimen are Blood for culture (if systemic infection is suspected) and Fluid aspirates from infected lesion for culture
- 24. Specimen collection; • Collectthe specimen using a sterile cotton-wool swab if aspirate is not possible • Pus from an abscess is best collected during abscess incision and drainage. • Pus from a wound should be collected before an antiseptic dressing is applied • Swabs should be well soaked in pus to collect adequate pus. 24
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- 26. Storage and transportation; •If pus swab use Amies transport medium. • If aspirate transfer the fluid to a sterile, leak-proof container. • cooked meat medium (or thioglycollate broth) when anaerobic pathogen are suspected
- 27. Macroscopic examination • Observingthe presence of granules and branching filaments suggestive of infections with actinomycetes or fungi. • Color- white-yellow, brown, green • Smell eg foul smelling for Anaerobic infections • a Wood lamp, for suspicion of dermatophytes (Microsporum) will fluoresce yellow-green.
- 28. Microscopic examination • Gramstain • For fungi suspicion ,a wet mount with 10% to 20% potassium hydroxide solution. Also Calcofluor white (CW) stain may also be used. • if mycobacterial disease is suspected, ZN or FM • To identify Nocardia species, a modified acid- fast stain can be performed,
- 29. Culture • Bacteria cultureby using BA and CA, and MCA; • For anaerobic organisms, an anaerobic transport and growth media should be used to maximize recovery. • For fungal(Candida spp.) on Sabouraud dextrose agar(SDA). • For mycobacteria spp, Lowenstein-Jensen and Middlebrook media could be used • For viruses, cell culture to observe CPE.
- 30. Identification • A Gramstain provides the morphologic • Growth characteristics and colonies appearance in culture media, • Convention Biochemical tests and API 20E can help identify the organism, • An automated MALDI-TOF MS has recently been adapted in many laboratories.
- 31. Other techniques. Theseinclude • Urine antigen detection (e.g., for systemic fungi); • serum antibody tests for bacteria, viruses, and parasites; • Immunological assay(ELISA) • Molecular techniques(PCR) for the detection of a great variety of bacteria, fungi, and viruses.
- 32. Antimicrobial susceptibility testing •Antimicrobial susceptibility testing is subsequently performed on isolates based on Standards updated guidelines eg CLSI and EUCAST. • Also molecular techniquies can be used for detection the mecA gene confer for methicillin resistance (e.g., in S. aureus) and the vanA and vanB genes conferring vancomycin resistance (e.g., in Enterococcus). • Also MALDI-TOF MS can be used
- 34. Treatment, • Treatment shouldbe guided by AST results • For bacteria wound dressing with mupirocin (topical) • For severe bacteria infection, Topically or orally administered erythromycin or clindamycin and amoxicillin-clavulanic are useful • Superficial mycoses use topical antifungal agents such as clotrimazole. Oral antifungal agents such as fluconazole,
- 35. Prevention and control Improvepersonal hygiene Hand washing Wash lesions with soap and water Remove crust Vaccination to immunocompromised such as namely on conjugated vaccines against pneumococcus, H influenzae and N meningitidis,
- 36. References • Jawetz, MedicalMicrobiology, 28th Edition. • Textbook of Diagnostic Microbiology-sixth Edition (2018) By Connie R. Mahon, Donald C. Lehman. • Monica Cheersburgh 2nd Edition. • Tanzania Standard Treatment Guideline, 2021 • Published Articles.
Editor's Notes
- #5 The skin, skin structures, and normal microbiota play a significant role in protecting the host against microbial invasion and disease. ■ Virulence factors of disease-producing organisms (e.g., toxins) can enable the organisms to evade host defense mechanisms, which can result in severe manifestations of infection. ■ A compromised immune system can lead to more severe or unusual manifestations of infection and can allow normally innocuous organisms to be pathogenic. ■ The occurrence of disease in a host is a function of the underlying host’s immunity and virulence of the pathogen. ■ The method and site of collection, quality of the clinical specimen, and clinical context are all important factors to consider when distinguishing between colonization and infection. ■ Proper specimen collection and laboratory processing of specimens are factors critical to the success of making a microbiological diagnosis of infection
- #7 Bacteria, viruses, fungi, and parasites are all important causes of skin and soft tissue infections. S. aureus and S. pyogenes are important causes of pyoderma.
- #9 Intertrigo (intertriginous dermatitis) is an inflammatory cutaneous condition that occurs in body areas subjected to heat, moisture, and friction, which work together to cause maceration and skin breakdown. Infectious agents enhance this process. Intertrigo usually occurs in the skin folds of infants and obese adults and often can be found in the axillae, in perineum (e.g., diaper rash), beneath the breasts, and in abdominal folds. The most common organism present in these areas is Candida, although S. aureus and coliforms also can play a role
- #12 A and B Axilla of a 65-year-old White man with erythrasma showing a well-demarcated erythematous plaque with fine scale (A). Wood lamp examination of the area showed characteristic bright coral red fluorescence (B). C and D A well-demarcated, red-brown plaque with fine scale in the antecubital fossa of an obese Hispanic woman (C). Wood lamp examination revealed bright coral red fluorescence (D).
- #14 Transmitted by human contact, sharing of clothesi ans coms, also zoonotic.
- #16 Erysipelas
- #19 The impairment of host defenses seen in diabetic patients can also allow weakly virulent organisms, such as coagulase-negative staphylococci and diphtheroids, to be pathogens in the skin.
- #23 For example, if pustules or vesicles are present, the roof or crust should be removed with a sterile blade, and any pus or exudate should be Gram stained and cultured
- #27 Anaerobic culture When an anaerobic infection is suspected (specimen is often foul-smelling), or the Gram smear shows an ‘anaerobic mixed flora’, inoculate a second blood agar plate and incubate it anaerobically (see subunit 7.4) for up to 48 hours. The anaerobic blood agar plate may be made selective by adding neomycin to it (see No. 16). At a final neomycin concentration of 50–70 g/ml, the majority of facultative anaerobic Gram negative rods will be inhibited.