MOD 5: Bacterial Skin Infections PDF

MICROBIOLOGY AND PARASITOLOGY 09/03/2024. MOD 5: BACTERIAL SKIN INFECTIONS...

MICROBIOLOGY AND PARASITOLOGY 09/03/2024. MOD 5: BACTERIAL SKIN INFECTIONS Dr. Vendale Jon D. Figuerres; Dr. Ma. Teresa A. Barzaga Trans Group/s: 3A, 4A OUTLINE PART 1: STAPHYLOCOCCI OBJECTIVES I. Staphylococci Learn the characteristics of bacterial agents that cause A. General Characteristics the following skin illnesses: B. Virulence Factors ○ Folliculitis, Furuncle, Carbuncle, Bullous Impetigo, Staphylococcal Scalded Skin Syndrome (SSSS), II. Staphylococcus aureus Toxic Shock Syndrome (TSS) III. Infections caused by Other Staphylococcus sp. Learn the epidemiology, laboratory diagnosis, treatment, IV. Diagnostic Laboratory Tests for Staphylococci and preventive and control measures against the infections V. Epidemiology and Control for Staphylococci VI. Streptococci I. STAPHYLOCOCCI A. General Characteristics B. Classification of Streptococci A. GENERAL CHARACTERISTICS C. Virulence Factors Gram-positive (+) spherical cells Arranged in grape-like irregular clusters D. Skin Diseases caused by Streptococci Aerobic or facultative anaerobic VII. Diagnostic Laboratory Tests for Streptococci Non-motile VIII. Epidemiology and Control for Streptococci Non-spore forming IX. Summary for Part I and II Can produce catalase as their by-product Normal flora of skin and mucous membranes X. Bacillus Primary reservoir: Human Nares XI. Bacillus anthracis A. Virulence Factors B. VIRULENCE FACTORS C. Diseases Caused by Bacillus anthracis This bacterial organism has a number of virulence factors that can generally cause different illnesses: D. Diagnostics by B. anthracis XII. Treatment, Prevention, and Control for Bacillus 1 Toxic Shock Syndrome Toxin-1 (TSST-1) XIII. Clostridium A. General Characteristics 2 Exfoliative toxins XIV. Clostridium perfringens A. Virulence Factors 3 Hemolysins B. Diseases Caused by Clostridium perfringens 4 Panton-Valentine Leukocidin (PVL) C. Diagnostics of C. perfringens XV. Prevention And Control for C. perfringens 5 Coagulase XVI. Erysipelothrix 6 Clumping Factor A. Erysipelothrix rhusiopathiae XVII. Summary for Part III 7 Enzymes (i.e. Hyaluronidase, Lipase, XVIII. Introduction To Mycobacterial Skin Infections Beta-lactamase) XIX. Mycobacterium leprae 8 Protein A XX. Mycobacterium marinum XXI. Mycobacterium ulcerans 9 Enterotoxin XXII. Summary XXIII. References Microbio and Para - Mod 5 Bacterial Skin Infections 1 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. 1. TOXIC SHOCK SYNDROME TOXIN-1 (TSST-1) TYPES OF HEMOLYSIN Enterotoxin F Chromosomal-mediated toxin ⍺-HEMOLYSIN Heterogeneous protein When activated, it becomes a superantigen that Can cause tissue damage stimulates T-cell proliferation and the subsequent due to its lytic activity in production of cytokines erythrocytes, platelets, ○ Binds to major histocompatibility class II molecules and macrophages → T-cell stimulation Disrupts smooth muscle in Associated with fever, shock and multisystem blood vessels involvement Gene is found in about 20% of S. aureus isolates. ꞵ-TOXIN Degrades sphingomyelin Causes majority of menstruation-associated toxic shock (SPHINGOMYELINASE C) Hydrolase enzyme that syndrome catalyzes hydrolysis of membrane phospholipids resulting in cell lysis Hemolytic activity is enhanced when incubated at 37°C and subsequent exposure to lower temperature (~4°C) Exhibited in CAMP laboratory test to identify Group B Streptococci δ-TOXIN Heterogeneous protein Multisystem involvement of TSST-1. and dissociated into Bacterial Skin Infections Lecture Video Part 1. subunits in non-ionic agents 2. EXFOLIATIVE TOXIN Cytolytic to erythrocytes and demonstrates Serine protease that splits the intracellular bridges of the non-specific membrane epidermis toxicity to other Two distinct proteins: mammalian cells ○ Exfoliative toxin A – encoded by eta gene located May have a role in on a phage; heat stable producing diarrhea when ○ Exfoliative toxin B – plasmid-mediated; heat-labile the gut is infected by S. When activated, this superantigen causes generalized aureus desquamation of staphylococcal scalded skin syndrome (SSSS) or Ritter Disease γ-HEMOLYSIN Leukocidin that lyses or ○ This is common in newborn and infants primarily affects the This also plays a major role in bullous impetigo. leukocytes (WBCs) Has a great association with Panton-Valentine Leukocidin 4. PANTON-VALENTINE LEUKOCIDIN (PVL) Lethal Exotoxin that affects polymorphonuclear leukocytes (or PMNs) ○ Primarily affects the neutrophils and monocytes Encoded on a mobile phage Two components: protein S and protein F SSSS or Ritter Disease. ○ Acts synergistically on WBCs together with Bacterial Skin Infections Lecture Video Part 1. gamma-hemolysin to form six potential two-component toxins 3. HEMOLYSINS ○ These proteins can cause pore-formation in the Cytolytic toxins that are regulated by agr gene cellular membranes that increase cation Affects erythrocyte (RBCs) and leukocytes (WBCs) permeability which leads to massive release of Has four major types inflammatory mediators ○ alpha(⍺)-hemolysin Contributes to invasiveness of S. aureus by suppressing ○ beta(ꞵ)-toxin phagocytosis ○ delta(δ)-toxin Important virulence factor in Community-Acquired ○ gamma(γ)-hemolysin Methicillin-Resistant Staphylococcus aureus (CA-MRSA) This diagram shows how PVL acts on polymorphonuclear cells: Microbio and Para - Mod 5 Bacterial Skin Infections 2 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  8. PROTEIN A Cell wall component of S. aureus that is characterized among MSCRAMMS Binds to Fc portion of IgG molecules except IgG3 ○ Blocks phagocytosis and negate the protective effects of IgG Fab portion of IgG-Protein A complex is free to combine with a specific antigen 9. ENTEROTOXIN Heat-stable exotoxins Superantigens that have the ability to interact with many T cells, causing an aggressive, overreactive immune Diagram of PVL mechanism on polymorphonuclear cells response Resistant to actions of the gut enzymes The 2 main components of PVL are LukS-PV (protein 15 types (A-E, G-P) S) and LukF-PV (protein F) which are secreted from S. Important cause of food poisoning – most commonly aureus before they assemble into a pore-forming caused by Enterotoxins A, B, and D heptamer on PMN membranes with the help of ○ Enterotoxin B – results in vomiting and diarrhea; γ-hemolysin. linked to staphylococcal pseudomembranous ○ High concentrations of PVL causes PMN lysis enterocolitis ○ Low concentrations of PVL mediate PMN apoptosis by directly binding to mitochondrial MEDICALLY IMPORTANT SPECIES OF STAPHYLOCOCCI membranes Tissue necrosis could result from the release of reactive 1 Staphylococcus aureus oxygen species (ROS) from lysed PMNs. Alternately, release of granule contents from lysed 2 Staphylococcus epidermidis PMNs could set in motion an inflammatory response which eventually leads to tissue necrosis. 3 Staphylococcus saprophyticus ○ It is unlikely that PVL has a direct necrotic effect on the epithelial cells. 4 Staphylococcus lugdunensis 5. COAGULASE II. STAPHYLOCOCCUS AUREUS Enzyme-like protein that clots oxalated or citrated Most clinically important species plasma Important community-acquired pathogen Agglutination occurs when bound to prothrombin and Coagulase-producing organism becomes enzymatically active to initiate fibrin Can cause superficial (i.e. impetigo, furunculosis) or polymerization systemic (i.e. septicemia, bacteremia) illnesses Due to this occurrence, fibrin may deposit on the surface Common cause of infective endocarditis and of S. aureus which results to the organisms toxin-induced illnesses (i.e. TSS – toxic shock anti-phagocytic characteristic (resisting phagocytosis) syndrome, food poisoning) Synonymous with invasive pathogenic potential 6. CLUMPING FACTOR A microbial surface component recognizing adhesive matrix molecules (MSCRAMM) responsible for adherence of S. aureus to fibrinogen and fibrin, thereby causing agglutination when mixed with plasma 7. OTHER ENZYMES Other enzymes that are considered as virulence factors of S. aureus include: Staphylococcus aureus. Bacterial Skin Infections Lecture Video Part 1 Hyaluronidase Permits bacteria to spread through A. PATHOGENESIS connective tissues Determined by: Also called spreading factor ○ Virulence of the strain ○ Size of infectious dose Lipase Degrades lipids on skin surface, ○ Status of host’s immune system permitting bacterial entry into the Superficial staphylococcal infections are initiated when epidermis there is a breach in skin or mucosal barrier ○ As the organism enters the deeper layers of the Beta- Enzyme that cleaves the ring skin, its virulence factors activate the host’s acute lactamase structure of penicillin inflammatory response Significant virulence factor of S. Toxins and enzymes secreted by the organism are aureus since this makes the resistant to inflammatory cell actions (i.e. phagocytosis) organism resistant to penicillin → (+) focal lesion Microbio and Para - Mod 5 Bacterial Skin Infections 3 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. B. SKIN INFECTIONS CAUSED BY S. AUREUS May be superficial or toxin-mediated 1. SUPERFICIAL INFECTIONS Suppurative Abscess is filled with pus surrounded by necrotic tissues and damaged leukocytes Usually occur as a result of previous skin injuries 1.1 Folliculitis Carbuncle. Bacterial Skin Infections Lecture Video Part 1 Mild inflammation of a hair follicle or sebaceous gland Lesion: small, erythematous papules; may be pruritic; 2. TOXIN-MEDIATED CUTANEOUS DISEASE often evolve to form pustules ○ Frequently associated with shaving Caused by toxins of S. aureus: ○ exfoliative toxins A and B ○ toxic shock syndrome toxin-1 May start primarily from skin or as secondary skin manifestation due to circulating bacterial toxins in the blood 2.1 Bullous Impetigo Pustules are larger as compared with streptococcal non-bullous impetigo, and is surrounded by a small zone of erythema Formation of bullae – caused by exfoliative toxins A and Folliculitis. Bacterial Skin Infections Lecture Video Part 1 B of S. aureus ○ Recall that exfoliative toxins are serine protease 1.2 Furuncle that splits the intracellular bridges of the epidermis Easily spread by direct contact with patients, fomites, or Extension of a folliculitis into deep tissue of the skin (i.e. autoinoculation dermis) Diagnosis: Gram-stain and culture of the bullous Lesion: large, raised, violaceous to erythematous, contents tender lesion containing abscess Treatment: cephalosporins, topical antibiotics (i.e. Risk Factors: diabetes mellitus, obesity, Mupirocin) immunocompromised state Treatment: incision and drainage, empirical antibiotics against staphylococcal agents Bullous Impetigo. Bacterial Skin Infections Furuncle. Bacterial Skin Infections Lecture Video Part 1 Lecture Video Part 1 1.3 Carbuncle 2.2 Staphylococcal Scalded Skin Syndrome (SSSS) Larger, more invasive lesions that develop from multiple Another essential and more serious dermolytic condition furuncle caused by exfoliative toxins A and B of S. aureus Extends to the subcutaneous fat May occur in children and adults, but newborns and Consists of multiple coalescing abscesses that can drain infants are the most vulnerable at several adjacent sites along hair follicles Transmission: direct contact, droplet contact, Patients can have systemic symptoms (i.e. fever, chills), nosocomial indicating systemic spread of the bacteria Characterized by fever, skin tenderness, scarlatiniform Most common sites: nape, back of the thighs rash, followed by extensive formation of bullae and Treatment: incision and drainage, empirical antibiotics exfoliation Microbio and Para - Mod 5 Bacterial Skin Infections 4 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  3. TOXIC SHOCK SYNDROME (TSS) Systemic syndrome caused by exotoxins/superantigens of S. aureus (less common) and Group A Streptococcus (more common) ○ Superantigens: TSST-1, Staphylococcal enterotoxins, Streptococcal pyrogenic exotoxins TSST-1: Staphylococcal infections; stimulates T cell proliferations and the subsequent production of cytokines Enterotoxins: Streptococcal infections Staphylococcal Scalded Skin Syndrome (SSSS). Bacterial Presents as a diffuse sunburn-like erythroderma in its Skin Infections Lecture Video Part 1 early stage, accompanied by fever, hypotension and evidence of multiorgan dysfunction Nikolsky Sign – the pathognomonic sign for SSSS; Cutaneous desquamation on palms and soles occurs elicited by stroking the skin upon which the epidermal during convalescent phase (1-2 weeks after rash onset) layer is easily separated from the rest of layers of the Commonly occurs in children and in young women who skin use superabsorbent tampons ○ Toxins act exclusively on stratum granulosum of Treatment plans: epidermis – no mucosal involvement (they do not ○ Systemic antibiotics act on mucosal surfaces) ○ Hydration Toxins may enter the bloodstream from an initial site and ○ Vasopressors may interact with the skin of other areas of the body ○ Debridement of infected tissue IVIG – may be helpful in neutralizing superantigens Normal skin vs. SSSS. Bacterial Skin Infections Lecture Video Part 1 Mortality: 1-5% in children; 50-60% in adults ○ Adults have much higher mortality rate compared to children when contracted with SSSS Treatment: ○ Immediate administration of antibiotics Cutaneous desquamation on palms and soles. ○ Hydration Bacterial Skin Infections Lecture Video Part 1 ○ Wound care Differential diagnosis: Toxic Epidermal Necrolysis (TEN) Professor’s Notes: ○ Split skin tissue occurs BETWEEN the dermis and Streptococcal toxic shock syndrome is more common epidermis than Staphylococcal toxic shock syndrome. ○ Caused by systemic reaction to antibiotics, barbiturates or other drugs III. INFECTIONS CAUSED BY OTHER ○ Not caused by a bacterial agent STAPHYLOCOCCUS SP. Staphylococcus May infect orthopedic or epidermidis cardiovascular prosthesis infection May be refractory to treatment because of formation of biofilms Staphylococcus Causes urinary tract infections in saprophyticus young women Staphylococcus Causes disease spectrum lugdunensis similar to S. aureus Shares hemolysis and clumping factor with S. aureus Comparison between SSSS and TEN. Bacterial Skin Infections Lecture Video Part 1 Microbio and Para - Mod 5 Bacterial Skin Infections 5 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  IV. DIAGNOSTIC LABORATORY TESTS FOR STAPHYLOCOCCI Specimens that may be submitted to the laboratory to confirm the etiologic agent of an infection: ○ Surface swab pus ○ Aspirate from an abscess ○ Blood ○ Endonasotracheal aspirate ○ Expectorated Sputum Blood agar plates of S. aureus and S. epidermidis. ○ Spinal fluid Bacterial Skin Infections Lecture Video Part 1 Techniques and Tests used: ○ Gram-stain Smears ○ Culture ○ Catalase Test ○ Coagulase Test ○ Susceptibility Testing A. SMEARS Staphylococcus species may appear as Gram-positive cocci organisms arranged in clusters in smear slides. Mannitol salt agar. A great limitation: CANNOT DIFFERENTIATE between Bacterial Skin Infections Lecture Video Part 1 S. aureus and non-aureus organisms (one staphylococcus species to another) C. CATALASE A cytochrome oxidase enzyme that converts hydrogen B. CULTURE peroxide into water and oxygen through the process A definitive diagnostic technique for identifying of hydrolyzation Staphylococcus species is through bacterial culture. 1. CATALASE TEST TYPES OF CULTURE A simple test to detect the presence of cytochrome oxidase enzymes BLOOD AGAR PLATES MANNITOL SALT AGAR ○ This is done by simply applying a drop of hydrogen peroxide on the specimen slide or tube containing Colonies of Used for contaminated the organism Staphylococcus specimens with mixed ○ A positive result will produce bubbles since the species appear after microbiota catalase has hydrolyzed hydrogen peroxide into incubating for 18 hours Used to screen for nasal water and oxygen at 37°C carriers of S. aureus and This test is used to differentiate Staphylococcus sp, a Hemolysis and pigment to recover S. aureus catalase-positive organism, from Streptococcus sp., a production may occur from respiratory catalase-negative bacteria. several days later specimens since S. Three hemolysis aureus can ferment patterns are reported: mannitol ○ alpha-hemolysis Mannitol can inhibit the ○ beta-hemolysis growth of other ○ gamma- organisms, including hemolysis non-aureus Staphylococci. HEMOLYSIS PATTERNS Catalase test. Lecture 11 Handout Alpha- Shows partial hemolysis of an hemolysis organism D. COAGULASE It will appear as areas of small An exoenzyme that clots blood plasma by a mechanism discoloration surrounding the cultured similar to normal clotting organism Two forms: ○ Free coagulase – secreted extracellularly Beta- Shows complete hemolysis of an ○ Bound coagulase – cell wall-associated protein hemolysis organism in which there are large areas of discoloration surrounding the cultured 1. COAGULASE TEST organism Staphylococcus aureus is a prime Used to detect the presence of coagulase, the example of an organism that exhibits exoenzyme present only in S. aureus beta-hemolysis. Large areas of golden Differentiates S. aureus from other Staphylococcus sp. yellow discoloration will be seen Done by applying a drop of blood plasma on a slide or surrounding the colonies. tube of specimen sample ○ Positive result: Presence of agglutination after 1-4 Gamma- Do not show hemolytic reaction from hours hemolysis the cultured colonies This is exemplified by Staphylococcus epidermidis. Microbio and Para - Mod 5 Bacterial Skin Infections 6 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  V. EPIDEMIOLOGY AND CONTROL TYPES OF COAGULASE TEST FOR STAPHYLOCOCCI SLIDE COAGULASE Detects bound coagulase A. EPIDEMIOLOGY TUBE COAGULASE Detects free coagulase CHIEF SOURCES OF INFECTION 1 Shedding Human Lesions 2 Fomites 3 Human Respiratory Tract 4 Skin Antibiotic-resistant Staphylococci may be carried in the nose or on the skin Slide and tube coagulase test. Lecture 11 Handout B. CONTROL OF MICROBE E. SUSCEPTIBILITY TESTING Broth microdilution or disk diffusion susceptibility testing CONTROL MEASURES FOR STAPHYLOCOCCUS Should be done routinely on staphylococcal isolates IN THE HOSPITAL from clinically significant infections 1. DISK DIFFUSION 1 Proper hygiene Also known as cefoxitin disk test 2 Strict adherence to infection-control policies Recommended for S. aureus, S. lugdunensis, and S. saprophyticus 3 Exclusion of individuals and personnel with active A zone of inhibition less than 22 mm in diameter infection in vulnerable areas such as nurseries, indicates resistance for cefoxitin ICUs, operating rooms, and chemotherapy wards 2. BROTH MICRODILUTION 4 Frequent screening for anterior nares colonization among high risk patients Either oxacillin or cefoxitin may be used to detect oxacillin resistance 5 Strict adherence of health care workers to infection ○ 2% of NaCl is added to the medium if cefoxitin is to control policies by wearing gloves and proper hand be used, and the test must be incubated for a full 24 hygiene before and after patient contact hours at 35°C Done by adding a certain amount of microbial sample into a series of broth tubes containing serial dilution of a specific drug CONTROL MEASURES FOR STAPHYLOCOCCUS The minimal inhibitory concentration (MIC) is then OUTSIDE THE HOSPITAL recorded 1 Proper hygiene 2.1 Penicillin G Resistance (+) for beta-lactamase 2 Avoidance of long-term usage of tampons Approximately 90% of S. aureus produce beta-lactamase; hence, majority are penicillin-resistant Professor’s Notes: 2.2 Nafcillin Resistance Aerosols and UV irradiation of air in hospitals have little to no effect for control (+) mecA or mecC genes ○ Genes that encode for PB2a Occurs in about 65% of S. aureus and approximately PART 2: STREPTOCOCCI 75% of S. epidermidis ○ mecA or mecC-positive organisms are also OBJECTIVES resistant to all extended spectrum penicillin, Learn the characteristics of bacterial agents that causes carbapenems, and cephalosporins (except the following skin illnesses ceftaroline) ○ Erysipelas ○ Cellulitis ○ Necrotizing Fasciitis ○ Non-Bullous Impetigo ○ Scarlet Fever ○ Streptococcal Toxic Shock Syndrome Learn the epidemiology, laboratory diagnosis, treatment, and preventive and control measures against the infections Microbio and Para - Mod 5 Bacterial Skin Infections 7 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  VI. STREPTOCOCCI A. GENERAL CHARACTERISTICS Gram-positive (+) spherical to ovoid cells Arranged in pairs or chains Catalase negative Most are facultative or aerotolerant anaerobes Can ferment glucose, with lactic acid as the end-product Different hemolytic patterns on blood agar. Bacterial Skin Infection Lecture Video Part 2 2. LANCEFIELD CLASSIFICATION Based on: carbohydrate antigen found in the cell wall of the organism ○ This is identified by an agglutination reaction on a specific antibody preparation Basis of serological specificity: amino sugar Lancefield Groups A-H and K-U Medically important groups for Streptococci: ○ A, B, C, D, F, G Streptococci. Bacterial Skin Infection Lecture Video Part 2 LANCEFIELD GROUPS OF MEDICALLY IMPORTANT STREPTOCOCCUS ORGANISMS B. CLASSIFICATION OF STREPTOCOCCI Based on the following AMINO SUGAR PRESENT REPRESENTATIVE ○ Colony morphology and hemolytic reactions on ORGANISM blood agar ○ Lancefield classification or serologic specificity of A Rhamnose-N- S. pyogenes the cell wall group-specific substance (Lancefield acetylglucosamine Antigens) and other cell wall or capsular antigens Majority of streptococcal bacteria are classified B Rhamnose-glucosamine S. agalactiae according to their Lancefield classification polysaccharide ○ Biochemical reactions and resistance to physical and chemical factors C Rhamnose-N- S. dysgalactiae sub. acetylgalactosamine equisimilis 1. HEMOLYSIS D Glycerol teichoic acid with S. bovis Streptococci can be classified based on their ability to D-alanine and Glucose hemolyze erythrocytes on blood agar plates ○ Many streptococcal organisms are able to hemolyze F Glucopyranosyl-N- S. anginosus erythrocytes acetylgalactosamine TYPES OF HEMOLYSIS G Rhamnose-N- S. canis acetylgalactosamine with ALPHA Incomplete lysis of erythrocytes with Galactose reduction of hemoglobin Result in the formation of a green pigment surrounding the colonies Ex. Streptococcus pneumoniae, Streptococcus mutans BETA Complete disruption of erythrocytes Clearing of blood around bacterial colonies Ex. Streptococcus pyogenes, Streptococcus agalactiae GAMMA Non-hemolytic organisms Ex. Some strains of Streptococcus salivarius Lancefield Classification. Bacterial Skin Infection Lecture Video Part 2 Microbio and Para - Mod 5 Bacterial Skin Infections 8 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. 3. BIOCHEMICAL REACTIONS 3. DEOXYRIBONUCLEASES (DNases) Used for: species that do not react with commonly used Enzymes that degrade DNA. antibody preparations for group-specific substances Facilitates the spread of Streptococci in the tissue by (A, B, C, F, and G) liquefying pus Organism will undergo to a battery of biochemical test Can be measured by the decrease in viscosity of DNA Include: solutions ○ sugar fermentation reactions Used in enzymatic debridement together with ○ test for presence of enzymes streptokinase ○ test for susceptibility to specific chemical substance C. VIRULENCE FACTORS M protein Streptokinase (Fibrinolysin) Deoxyribonucleases (DNases) Hyaluronidase Pyrogenic Exotoxins (Erythrogenic Toxin) Hemolysins 1. M-PROTEIN Major virulence factor of Streptococci Filamentous structure anchored to the cell membrane that penetrates and projects from the cell wall Deoxyribonucleases. Bacterial Skin Infection Action: Inhibits the activation of alternative Lecture Video Part 2 complement pathway 4. HYALURONIDASE TWO MAJOR STRUCTURAL CLASSES Acts as a spreading factor Splits hyaluronic acid of the tissue which enables the CLASS I Contains antigenic epitopes infecting microbes to spread throughout the body system CLASS II DOES NOT possess epitopes Antigenic and specific Specific antibodies of hyaluronidase-producing organisms are seen in the serum after infection M-Protein. Bacterial Skin Infection Lecture Video Part 2 Hyaluronidase. Bacterial Skin Infection Lecture Video Part 2 2. STREPTOKINASE (FIBRINOLYSIN) 5. PYROGENIC EXOTOXINS (ERYTHROGENIC TOXIN) Action: Transforms plasminogen of human plasma into plasmin Analogous to exfoliative toxins (A and B) of ○ Allows escape of bacteria from blood clots Staphylococcus ○ Interfered with: non-specific serum inhibitors & Associated with streptococcal toxic shock syndrome antistreptokinase and scarlet fever Produced by: Group A, β-hemolytic Streptococci Act as superantigens which stimulate T cells by binding to the class II major histocompatibility complex in Vb region of the T-cell receptor → release of cytokines that mediate shock and tissue injury THREE ANTIGENICALLY DISTINCT STREPTOCOCCAL PYROGENIC EXOTOXINS (Spe) SpeA Produced by Group A Strep. that carry a lysogenic phage SpeB Cysteine protease Streptokinase (fibrinolysin). Bacterial Skin Infection Lecture Interferes with phagocytosis Video Part 2 SpeC Similar with SpeA Microbio and Para - Mod 5 Bacterial Skin Infections 9 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  Risk Factors in Diabetes mellitus Adults Alcohol abuse Venous stasis Trauma Skin ulcers Chronic inflammatory skin conditions Lymphatic obstruction Drug of Choice Penicillin 1st Generation Cephalosporins (i.e. Cefalexin, Erythromycin) Pyrogenic Exotoxins (Erythrogenic Toxins). Bacterial Skin Infection Lecture Video Part 2 6. HEMOLYSINS (STREPTOLYSINS) Lyse erythrocyte membranes and cause damage to other cells Produced by S. pyogenes 6.1 Streptolysin O Hemolytically active in reduced state Rapidly inactivated in the presence of oxygen ○ Easily detected with anti-streptolysin O (ASO) Erysipelas. Lecture 11 handout titers 1.2 Cellulitis 6.2 Streptolysin S Diffuse inflammation and infection of the superficial skin Responsible for the hemolytic zones produced around layers and subcutaneous tissues the streptococcal colonies growing on the surface of Extends deeper into the soft tissues blood agar plates ○ Not antigenic Characterized Painful, erythema, warmth, and by edema of the skin with poorly defined margins Drainage of pus may sometimes occur Risk Factors Surgery Trauma Skin ulcer Dermatitis Treatment Broad spectrum antibiotics that may cover for Streptococcus, Staphylococcus, Hemolysins (Streptolysins). and other gram-positive or Bacterial Skin Infection Lecture Video Part 2 gram-negative organisms, including anaerobes D. SKIN DISEASES CAUSED BY STREPTOCOCCI 1. SUPERFICIAL INVASION AND SPREADING OF S. PYOGENES 1.1 Erysipelas Superficial infection that involves the epidermis, dermis and lymphatic system Usually seen in children and older adults Sometimes preceded by a respiratory beta-hemolytic streptococcal infection Characterized Painful, indurated, erythematous by areas of inflammation with Cellulitis. Lecture 11 Handout raised borders that are sharply demarcated from the adjacent normal skin Microbio and Para - Mod 5 Bacterial Skin Infections 10 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. 1.2.1 Recurrent Cellulitis 2. LOCAL INFECTION WITH S. PYOGENES AND THEIR BY-PRODUCTS Usually predisposed to patients with lymphedema, obesity, venous stasis, and untreated tinea pedis 2.1 Non-Bullous Impetigo (Impetigo Contagiosa) 1.3 Necrotizing Fasciitis Purulent skin infection involving face and extremities. Often begin at a site of trauma and progress from More contagious than Bullous Impetigo. superficial involvement to deep involvement in a rapid Initial lesions begin as small vesicles and progress to manner pustules May occur as a bacteremia with secondary involvement Prominent honey-colored crust lesions are due to of skin and soft tissues ruptured pustules that produce purulent discharge, Loss of sensation in the involved area may occur due to which eventually dries out extensive tissue damage. ○ Ruptured pustules → purulent discharge and dries out → honey-colored crusts Approximately 10% of cases are caused by Group A Characterized Painful, erythematous lesions streptococci; Majority by S. aureus. by which progress to hemorrhage, Group B streptococci occasionally cause impetigo in ischemia and necrosis newborns acquired through vaginal delivery. afterwards Common in hot and humid climates. Bullae and palpable gas Most common skin infection in children. (crepitus) may also occur due to tissue ischemia from thrombosed blood vessels Risk Factors Overcrowding Diabetes mellitus Treatment Oral penicillin** (for streptococcal impetigo) Cefalexin (for MRSA impetigo) Dicloxacillin (for MRSA impetigo) ** - drug of choice Necrotizing Fasciitis. Lecture 11 handout 1.3.1 Polymicrobial Necrotizing Fasciitis (Type I) Honey-colored crust lesions. caused by Enterobacterales and anaerobes Bacterial Skin Infections Lecture Video Part 2 1.3.2 Monomicrobial Necrotizing Fasciitis (Type II) 3. INVASIVE GROUP A STREPTOCOCCAL INFECTIONS caused by S. pyogenes (more common) or S. aureus Diseases caused by invasive Group A streptococcal (less common) infections: Usually involve the extremities ○ Scarlet Fever ○ Streptococcal Toxic Shock Syndrome Monomicrobial Necrotizing Fasciitis (Type II) 3.1 Scarlet Fever Risk Factors Blunt Trauma Caused by release of streptococcal pyrogenic exotoxin. Surgery Most commonly occurs in children with concomitant Childbirth pharyngeal infection IV Drug Use Rash starts on the chest and spreads outward; Does not involve the face. Treatment Immediate surgical exploration of the wound Lesion Erythematous Excision of all devitalized tissue Petechial to maculopapular Empiric broad-spectrum Sandpaper textured rashes antibiotics Other Signs & Flushed skin Drug Choices Vancomycin Symptoms Circumoral pallor Combination regimen: Strawberry tongue Daptomycin + Piperacillin-tazobactam Treatment Penicillin Combination regimen: Macrolides Carbapenem + Clindamycin Cephalosporin Microbio and Para - Mod 5 Bacterial Skin Infections 11 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  VII. DIAGNOSTIC LABORATORY TESTS FOR STREPTOCOCCI Streptococcal infections may be detected through throat swab, pus, CSF, and other sterile body fluid via culture Detection through blood is via serum for antibody determination A. SMEARS Positive (+) smear samples often show single cocci or pairs rather than definite chains Sometimes, the organism may appear as gram-negative cocci due to loss of viability Throat swab smears are rarely contributory ○ This is because viridans streptococci are always present and have the same appearance as group A streptococci Scarlet Fever. Bacterial Skin Infections Lecture Video Part 2 3.2 Streptococcal Toxic Shock Syndrome Presented similarly as staphylococcal toxic shock syndrome Portal of entry is through skin with cellulitis that progresses rapidly Most cases involve young adults Same signs and symptoms as with the Staphylococcal Toxic Shock Syndrome Streptococci Smear. Bacterial Skin Infections Lecture Video Part 2 Risk Factors Lack of immunization Prolonged skin infection/chronic B. CULTURE dermatitis Specimens suspected of streptococcal infection are cultured in blood agar plates Diagnosis Blood cultures are more often Incubation in 10% CO2 increases the rate of hemolysis positive, yielding more growth in ○ Streptolysins are active in the absence of oxygen Streptococcal TSS than in Alpha-hemolytic streptococci and enterococci may grow Staphylococcal TSS slowly ○ Streptococcus pyogenes are beta-hemolytic Treatment Antimicrobial therapy Bacitracin Sensitivity Test is used for detection of Debridement of infected tissues Group A streptococci IVIG (as adjunct therapy) ○ Group A streptococci may be presumptively identified by inhibition of growth by bacitracin Bacitracin Sensitivity Test. Bacterial Skin Infections Lecture Video Part 2 Streptococcal Toxic Shock Syndrome. Bacterial Skin Infections Lecture Video Part 2 C. ANTIGEN DETECTION TESTS Commercially-available rapid test kits that use enzymatic or chemical methods to extract antigen from the swab, then use enzyme immunoassay or agglutination tests to demonstrate the presence of antigen 60-90% sensitive and 98-99% specific as compared with culture methods Microbio and Para - Mod 5 Bacterial Skin Infections 12 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  IX. SUMMARY General characteristic of Staphylococci and Streptococci Virulence factors of Staphylococci and Streptococci Others medically agents belonging to Staphylococcus genus Classification of Staphylococcus Different skin infections caused by Staphylococci and Streptococci Different diagnostic tests to determine the presence of Staph and/or Strep Epidemiology, prevention and control measures for Antigen Detection Tests. Bacterial Skin Infections Lecture Staph and Strep Video Part 2 PART 3: BACILLUS, CLOSTRIDIUM, D. SEROLOGIC TESTS & ERYSIPELOTHRIX Used to detect antibody titers in the serum It is done by making serial dilution of the patient’s serum OBJECTIVES and adding a drop of RBC in the diluted samples Learn the characteristics of bacterial agents that causes The test is positive (+) if there is a agglutination reaction the following skin illnesses ○ Anthrax, Gas Gangrene, Erysipeloid ASO For respiratory infections Learn the epidemiology, laboratory diagnosis, treatment, Most widely used and preventive and control measures against the infections. Anti-DNase B & For skin infections Antihyaluronidase X. BACILLUS Anti-Streptokinase Not frequently utilized A. GENERAL CHARACTERISTICS compared to ASO and Large (size = 1.0 x 3.0-4.0 um), gram-positive, Anti-M Anti-DNase B & rod-shaped Type-Specific Antihyaluronidase Arranged in long chains Pathogenic species possess virulent plasmids Most are saprophytic Spores are located at the center of the bacilli and are resistant to environmental changes. Serologic Test. Bacterial Skin Infections Lecture Video Part 2 VIII. EPIDEMIOLOGY AND CONTROL Bacillus. Bacterial Skin Infections Lecture Video Part 3 FOR STREPTOCOCCI A. EPIDEMIOLOGY MEDICALLY IMPORTANT SPECIES OF BACILLUS SP. Humans can be asymptomatic carriers via nasopharynx or perineum 1 Bacillus anthracis Causes anthrax Nasal discharges harboring S. pyogenes are the most dangerous source of spread 2 Bacillus cereus Causes food poisoning Viridans streptococci and enterococci are part of normal flora of the body B. PREVENTION Prophylactic antibiotics prior surgical procedures, especially to patients with known heart valve deformity and to those prosthetic valves or joints C. CONTROL Detection and early antimicrobial therapy of respiratory and skin infections with group A streptococci Antistreptococcal chemoprophylaxis in persons who have suffered an attack of rheumatic fever Bacillus cereus. Eradication of S. pyogenes from carriers. Bacterial Skin Infections Lecture Video Part 3 Microbio and Para - Mod 5 Bacterial Skin Infections 13 of 24 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  XI. BACILLUS ANTHRACIS Primary hosts: herbivores Humans are just incidental hosts Endemic in developing countries (i.e., Africa, Middle East, and Central America) Portal of entry is through mouth in herbivores In humans, infection is acquired through the following: ○ Cutaneous anthrax - Injured skin ○ Inhalation anthrax - Inhalation of the organism ○ Gastrointestinal anthrax (rare) - Gut mucosa via consumption of an infected ○ May also be acquired through injection or bite of an infected insect (rare) Bacillus Anthracis. Bacterial Skin Infections Lecture Video Part 3 B. VIRULENCE FACTORS Aid in the survival of the bacteria as they spread via the lymphatics Bacteria may propagate freely in the blood and in tissues before and after the host‘s death 2 primary virulence factors: capsule and exotoxins 1. CAPSULE Composed of Poly-gamma D-glutamic acid Bacillus Anthracis. Antiphagocytic Bacterial Skin Infections Lecture Video Part 3 Genes responsible for its formation are encoded on pXO2 plasmid A. THE ANTHRAX CYCLE The figure below shows the different points of entry of 2. EXOTOXINS anthrax Herbivores acquire them through ingestion of bacteria Compounds released by the bacteria responsible for from the soil tissue edema and death Humans may acquire the disease through contamination Genes are encoded on pXO1 plasmid of injured skin, inhalation, or consumption of infected meat THREE IMPORTANT EXOTOXINS Anthrax may also be considered as vector borne infection (rare) Protective binds to specific cell receptors and Agent (PA) mediates entry of EF and LF Edema Factor an adenylate cyclase that becomes (EF) an edema toxin when combined with the protective agent PA + EF = edema toxin the edema toxin is responsible for cell and tissue edema Lethal Factor lethal factor when combined with the (LF) protective agent, it produces lethal toxin PA + LF = lethal toxin Lethal toxin - major virulence factor of Anthrax that causes death The Anthrax Cycle. Bacterial Skin Infections Lecture Video Part 3 Once the anthrax bacteria enters the body, spores germinate in the tissue at the portal of entry The human immune system will try to eradicate the bacterial spore, however, due to the formation of the gelatinous edema and congestion, the growth of vegetative cells will ensue Capsule and Exotoxins. Bacterial Skin Infections Lecture Video Part 3 Microbio and Para - Mod 5 Bacterial Skin Infections