Lecture 1 Musculoskeletal-Microbiology PDF

Course: Musculoskeletal-Microbiology Course code: BMD20 Collage: Medicine and health sciences Department: Basic medical sciences Program: Medicine & Surgery Name of lecturer: Ibrahim AL-Sabal Email: [email protected]  Musculoskeletal block - Microbiology...

Course: Musculoskeletal-Microbiology Course code: BMD20 Collage: Medicine and health sciences Department: Basic medical sciences Program: Medicine & Surgery Name of lecturer: Ibrahim AL-Sabal Email: [email protected]  Musculoskeletal block - Microbiology 1 st lecture  Structure and functions (defenses) of the Skin  Bacterial Diseases of the Skin and Wounds 2  Bacterial diseases of the skin and wounds Dear student at the end of this lecture you should be able to: Describe the structure, functions and normal microbiota of the skin. Define folliculitis, furuncle, carbuncle, and impetigo. Describe the pathogen, pathogenesis, signs, symptoms, diagnosis, treatment, and prevention of folliculitis and associated infections. Describe the pathogen, pathogenesis, signs, symptoms, diagnosis, treatment, and prevention of Staphylococcal Scalded Skin Syndrome. Describe the pathogen, pathogenesis, signs, symptoms, diagnosis, treatment, and prevention of impetigo (pyoderma). erysipelas, and necrotizing fasciitis.  Bacterial Diseases of the Skin and Wounds Components and vocabulary of the lecture: Structure, Functions, and Normal Microbiota of the skin Bacterial Diseases of the Skin and Wounds For each disease Pathogen and Diagnosis, treatment Pathogenesis Clinical features virulence factors and prevention  Introduction Structure of the skin  Introduction Functions of the skin Skin keeps the internal organs together Skin prevents excessive water loss Skin helps regulate body temperature Skin assists in the formation of vitamin D Skin is involved in sensory phenomena  Introduction Skin defenses Several layers of deadepithelial cells The skin surface is inhabited by a variety of normal microbiota The skin generates antimicrobial peptides The sweat lower the skin pH The high salt concentration in sweat inhibit the growth of most pathogens sebum, has a low pH makes the skin inhospitable to most microorganisms.  Introduction Normal Microbiota of the Skin The skin is colonized by an array of organisms which forms its normal microbiota. The relatively arid areas of the forearm and back are colonized with fewer organisms, but are more numerous in moister areas. Bacteria such as: Staphylococcus epidermidis, Propionibacterium, Corynebacterium, Lactobacillus, Bacteroides, Prevotella, Haemophilus Yeasts such as Malassezia andCandida  Introduction Microbial Diseases of the Skin and Muscles skin and soft tissue infections are the second most common infections encountered in primary care settings, following respiratory infections. Skin microbial diseases can occur through three pathways: 1- Breach of intact skin, allowing external infection. 2- Skin manifestations of systemic infections from blood-borne spread. 3- Toxin-mediated skin damage from microbial toxins produced elsewhere in the body.  Section 1: Bacterial Diseases of the Skin and Wounds 1- Folliculitis, furuncles (boils), and carbuncles Folliculitis, furuncles (boils), and carbuncles are all infections of the hair follicle Staphylococcus aureus. Pathogen facultative anaerobic, Gram positive bacteria that forms grape-like clusters of spherical cells Hot tub folliculitis Pseudomonas aeruginosa  Bacterial Diseases of the Skin and Wounds 1- Folliculitis and associated infections 1- Coagulase 2- Hyaluronidase a- Enzymes 3- Staphylokinase 4- β-Lactamase virulence factors b- Protein A a defense against Phagocytosis 1- Cytolytic toxins 2- Leukocidin c- Toxins 3- Exfoliative toxins 4- Toxic shock syndrome toxin  Bacterial Diseases of the Skin and Wounds 1- Folliculitis, furuncles (boils), and carbuncles Humans acquireStaphylococcus aureus through direct contact with infected individuals or contaminated objects (fomites) Pseudomonas aeruginosa acquired from exposure to contaminated warm water Pathogenesis Bacteria on the surface of the skin grow into hair follicles and, in some cases, invade the surrounding tissues and progress to form furuncle and carbuncle. Invasion leads to inflammation, fever, and symptom development as natural responses to infection  Bacterial Diseases of the Skin and Wounds 1- Folliculitis, furuncles (boils), and carbuncles Folliculitis Signs and Symptoms furuncle or boil Carbuncle  Bacterial Diseases of the Skin and Wounds 1- Folliculitis, furuncles (boils), and carbuncles Diagnosis of folliculitis, furuncle, or carbuncle is based on the characteristic clinical presentation Diagnosis In most cases, laboratory tests are unnecessary for diagnosing furuncle or carbuncle. However, bacterial culture and sensitivity testing of the pus sample may be ordered in severe or recurrent cases  Bacterial Diseases of the Skin and Wounds 1- Folliculitis, furuncles (boils), and carbuncles incision of the lesion, drain the pus from the abscesses clean the wound and apply topical antibiotic therapy with mupirocin Treatment In the United States, current recommendations suggest clindamycin + trimethoprim/ sulfamethoxazole (TMP/SMZ) or doxycycline Vancomycin is used to treat such infections caused by methicillin resistant strains MRSA  Bacterial Diseases of the Skin and Wounds 2- Impetigo (Pyoderma) Impetigo is a superficial bacterial infection limited to the epidermis and presents as a bullous, crusted, or pustular eruption of the skin. It is not a serious disease but is highly contagious. Impetigo can be caused byStaphylococcus aureus or Streptococcus pyogenes Most cases caused by both bacteria (a Combination) Pathogens S. pyogenes is a Gram-positive coccus arranged in chains  Bacterial Diseases of the Skin and Wounds 2- Impetigo (Pyoderma) The bacteria of impetigo occasionally colonize the skin and then invade through scratches, abrasions, or other wounds. Pathogenesis Children are commonly affected by impetigo, with infections frequently occurring beneath the nose where the skin is abraded due to frequent mucus wiping.  Bacterial Diseases of the Skin and Wounds 2- Impetigo (Pyoderma) Impetigo characterized by small, flattened, red patches that appear primarily on the face and limbs The patches develop into oozing, pus-filled vesicles on a red base vesicles eventually break and form a thick honey- Signs and Symptoms colored, sticky crust Lesions primarily occur around the mouth, face, and extremities but can manifest anywhere on the skin Impetigo affects mostly preschool children, but individuals of all ages can acquire the disease.  Bacterial Diseases of the Skin and Wounds 2- Impetigo (Pyoderma) Doctors usually diagnose impetigo by visual inspection the pus found in the blisters is filled with bacteria and white blood cells, which distinguishes impetigo from scalded skin syndrome Diagnosis The presence of grapelike clusters of Gram-positive cocci indicates staphylococcal impetigo the presence of chains of Gram-positive cocci characterizes streptococcal impetigo and erysipelas  Bacterial Diseases of the Skin and Wounds 2- Impetigo (Pyoderma) Impetigo is commonly treated with topical mupirocin (Bactroban), an effective drug that targets bothS. pyogenes and S. aureus. Treatment In cases caused byS. aureus , oral antibiotics like dicloxacillin or cephalexin are often required For methicillin-resistantS. aureus (MRSA), trimethoprim-sulfamethoxazole (TMP-SMZ) is the primary alternative  Bacterial Diseases of the Skin and Wounds 2- Impetigo (Pyoderma) Good general hygiene and cleanliness help to prevent Prevention impetigo and erysipelas  Bacterial Diseases of the Skin and Wounds 3- Erysipelas Erysipelas is a bacterial infection that affects the upper dermis and lymphatic vessels in the skin Streptococcus pyogenes is the causative agent of erysipelas Pathogens S. pyogenes is a Gram-positive coccus arranged in chains  Bacterial Diseases of the Skin and Wounds 3- Erysipelas Erysipelas occurs when bacteria enter the skin through a cut or break Toxins released by the bacteria contribute to the characteristic inflammation, typically seen on the face, Pathogenesis legs, or feet Erysipelas manifests as reddening of the skin, swollen local lymph nodes, pain, fever, chills, and leukocytosis About 5% of patients with erysipelas go on to develop bacteremia which carries a high mortality if untreated  Bacterial Diseases of the Skin and Wounds 3- Erysipelas Doctors diagnose erysipelas by examining visible signs such as sores, blisters, or raised skin rashes Diagnosis Your doctor will also take your medical history, asking about injuries or surgeries  Bacterial Diseases of the Skin and Wounds 3- Erysipelas Oral penicillin is prescribed if your doctor diagnoses erysipelas Treatment If the condition is severe, they may recommend intravenous penicillin  Bacterial Diseases of the Skin and Wounds 4- Staphylococcal Scalded Skin Syndrome Five percent of strains ofStaphylococcus aureus secrete one or two distinct exfoliative toxins that cause SSSS Pathogen facultative anaerobic, Gram positive bacteria whose spherical cells are typically clustered in grapelike arrangements  Bacterial Diseases of the Skin and Wounds 4- Staphylococcal Scalded Skin Syndrome The blood carries exfoliative toxins from sites of infection throughout the body toxemia ( ) Exfoliative toxins cause the dissolution of epidermal desmosomes, which are intercellular bridge proteins Pathogenesis that hold together cytoplasmic membranes of adjoining cells and therefore, lead to skin sloughing Death, if it occurs, is most often due to secondary infections of skinless areas by bacteria such as Pseudomonas aeruginosa or yeasts such asCandida albicans  Bacterial Diseases of the Skin and Wounds 4- Staphylococcal Scalded Skin Syndrome reddening and wrinkling of the skin that typically begins near the mouth, spreads over the entire body followed by large blisters that contain clear fluid lacking bacteria and white blood cells Fever may precede the skin manifestations Signs and Symptoms Within two days, the affected outer epidermis peels off in sheets  Bacterial Diseases of the Skin and Wounds 4- Staphylococcal Scalded Skin Syndrome Diagnosis is made on the basis of the distinctive sloughing of the skin Diagnosis Histological examination is usually a better way to diagnose the disease than reliance on culture  Bacterial Diseases of the Skin and Wounds 4- Staphylococcal Scalded Skin Syndrome Treatment involves intravenous antimicrobial drugs such as cloxacillin Treatment Vancomycin is used to treat resistant strains  Bacterial Diseases of the Skin and Wounds 4- Staphylococcal Scalded Skin Syndrome Prevention Little can be done to prevent SSSS becauseS. aureus is normally on moist skin  Bacterial Diseases of the Skin and Wounds 5- Necrotizing Fasciitis Several bacteria can cause necrotizing fasciitis, but the most common cause isStreptococcus pyogenes Pathogens S. pyogenes is a Gram-positive coccus arranged in chains  Bacterial Diseases of the Skin and Wounds 5- Necrotizing Fasciitis S. pyogenes is passed from person to person and enters the body through breaks in the skin. It spreads rapidly along muscle fascia S. pyogenes secretes enzymes that allow the bacterium to invade body tissues. Streptokinases dissolve blood clots Hyaluronidase breaks down hyaluronic acid between cells Pathogenesis Deoxyribonucleases break down DNA released from damaged host cells M protein allows S. pyogenes to survive phagocytosis S. pyogenes also secretes toxins that damage tissue Enzymes and toxins secreted byS. pyogenes can destroy tissue at the rate of several centimeters an hour  Bacterial Diseases of the Skin and Wounds 5- Necrotizing Fasciitis A hot, intensely painful, sunburn-like rash at the site of infection Subsequently, patients develop fever, tiredness, and muscle aches Signs and Symptoms As tissue is destroyed, blood pressure drops, and patients become mentally confused and ultimately comatose Necrotizing fasciitis has developed following surgery, abortion, and seemingly harmless events such as an insect bite or a needle stick to draw blood  Bacterial Diseases of the Skin and Wounds 5- Necrotizing Fasciitis Diagnosis of necrotizing fasciitis involves a combination of: Diagnosis clinical evaluation, imaging studies, laboratory tests, and sometimes surgical exploration  Bacterial Diseases of the Skin and Wounds 5- Necrotizing Fasciitis Physicians must remove dead tissue immediately, repeating the procedure daily until bacterial destruction of tissue is halted Doctors prescribe intravenous broad-spectrum Treatment antimicrobial drugs to curb the severity of disease and inhibit any remaining bacteria Clindamycin and penicillin when used together had a cure rate of 83%, compared to a cure rate of only 41% for penicillin alone  ‫ﺗﻜــﺎﻟﻴﻒ اﻟﻤﺤﺎﺿﺮة‬ ‫ﻋﻘﻮم ىﻠﻊ ةرﺿﺎﺣﻤﻼ ﺗﺎﻗﻔﺮم ىﻺ ﻋﻮﺟﺮﻻ ﻣﺘﻲ‬ ‫‪.LMS‬ةﻋﻤﺎﺟﻠﻞ ﻳﻨﻮرﺗﻜﻺﻻ ﻣﻴﻠﻌﺘﻼ ﻣﺎﻇﻦ‬ ‫وأداء ﺗﻜﻠﻴﻒ اﻟﻤﺤﺎﺿﺮة اﻷول وإرﺳـﺎﻟﻪ ﻓﻲ اﻟﻤﻮﻋﺪ‬ ‫اﻟﻤﺤﺪد ﻟﺬﻟﻚ‪.‬‬ ‫ﻋﺰﻳﺰي اﻟﻄﺎﻟﺐ‪:‬‬ ‫ﻳﻤﻜﻨﻚ اﻻﻃﻼع ﻋﻠﻰ اﻟﻔﻴﺪﻳﻮ ﻋﺒﺮ زﻳﺎرة اﻟﺮاﺑﻂ اﻟﺘﺎﻟﻲ ﻟﻼﻃﻼع‬ ‫ﻋﻠﻰ ‪:....................‬‬ ‫‪https://www.youtube.com/...................‬‬ ‫‪37‬‬