Skin Defenses and Acne Treatment
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Questions and Answers

Which surface antigen of S. pyogenes helps in resisting phagocytosis?

  • Fimbriae
  • M-protein (correct)
  • C substance
  • Capsule
  • What type of toxin produced by S. pyogenes induces fever and a red rash?

  • Streptolysins
  • Erythrogenic toxin (correct)
  • Superantigens
  • Streptokinase
  • What is the primary means of transmission for S. pyogenes infections?

  • Vector-borne transmission
  • Direct contact and droplets (correct)
  • Airborne pathogens
  • Fecal contamination
  • Which of the following describes a typical characteristic of Impetigo caused by S. pyogenes?

    <p>Formation of superficial lesions</p> Signup and view all the answers

    Which enzyme produced by S. pyogenes is responsible for digesting fibrin clots?

    <p>Streptokinase</p> Signup and view all the answers

    What component in sebum is known for its antimicrobial properties?

    <p>Fatty acids</p> Signup and view all the answers

    Which bacteria are primarily responsible for normal skin microbiota?

    <p>Staphylococci</p> Signup and view all the answers

    What type of acne is characterized by few scattered pustules with no inflammation?

    <p>Mild Acne</p> Signup and view all the answers

    What treatment is commonly prescribed for moderate acne?

    <p>Topical antibiotics</p> Signup and view all the answers

    What is the most common resident bacterium of the skin associated with acne?

    <p>Cutibacterium acnes</p> Signup and view all the answers

    What type of skin lesion is considered severe and includes high risk of scarring?

    <p>Cystic Acne</p> Signup and view all the answers

    Which characteristic is typical for Staphylococcus aureus?

    <p>Producing various virulence factors</p> Signup and view all the answers

    Which agent is known to loosen clogged follicles in the treatment of moderate acne?

    <p>Benzoyl peroxide</p> Signup and view all the answers

    What function does penicillinase serve in Staphylococcus aureus?

    <p>Inactivates penicillin</p> Signup and view all the answers

    Which toxin produced by Staphylococcus aureus is responsible for inducing systemic organ damage?

    <p>Toxic shock syndrome toxin (TSST)</p> Signup and view all the answers

    What is a common predisposing factor for Staphylococcus aureus infections?

    <p>Immunodeficiency</p> Signup and view all the answers

    Which condition is characterized by an abscess forming inside the bone due to Staphylococcus aureus?

    <p>Osteomyelitis</p> Signup and view all the answers

    What type of infection manifests as bubble-like swellings that break and peel away, most commonly in newborns?

    <p>Impetigo</p> Signup and view all the answers

    What role does hyaluronidase play in the virulence of Staphylococcus aureus?

    <p>Digests connective tissue</p> Signup and view all the answers

    How does food intoxication occur in relation to Staphylococcus aureus?

    <p>By the production of heat-stable enterotoxins</p> Signup and view all the answers

    Which localized staphylococcal infection is a more severe form characterized by clusters of furuncles?

    <p>Carbuncle</p> Signup and view all the answers

    What is a characteristic feature of cutaneous anthrax lesions?

    <p>They begin as a raised bump.</p> Signup and view all the answers

    Which of the following is not a virulence factor associated with Bacillus anthracis?

    <p>Endotoxins</p> Signup and view all the answers

    What type of infection is scarlet fever primarily associated with?

    <p>Streptococcal infections</p> Signup and view all the answers

    Which of the following describes a common characteristic of the genus Bacillus?

    <p>They are endospore-forming and motile.</p> Signup and view all the answers

    What is the role of rapid diagnostic tests in the identification of streptococcal skin infections?

    <p>They ensure proper treatment to prevent complications.</p> Signup and view all the answers

    What is the mortality rate associated with gastrointestinal anthrax?

    <p>50%</p> Signup and view all the answers

    Which type of anthrax infection has a mortality rate of 100%?

    <p>Inhalational (pulmonary) anthrax</p> Signup and view all the answers

    What is a common treatment for gas gangrene caused by Clostridium perfringens?

    <p>Penicillin</p> Signup and view all the answers

    Which virulence factor of Clostridium perfringens is associated with tissue destruction?

    <p>Alpha toxin</p> Signup and view all the answers

    What is the incubation period for leprosy?

    <p>2-5 years</p> Signup and view all the answers

    What type of lesions are characterized as shallow and asymmetrical in leprosy?

    <p>Tuberculoid lesions</p> Signup and view all the answers

    Which method is commonly used for the diagnosis of leprosy?

    <p>Detection of acid-fast bacilli</p> Signup and view all the answers

    Which of the following statements about human papillomavirus (HPV) is true?

    <p>HPV causes a variety of skin warts</p> Signup and view all the answers

    Which treatment method is NOT commonly used for removing warts caused by HPV?

    <p>Laser therapy</p> Signup and view all the answers

    How is chickenpox primarily transmitted?

    <p>Respiratory route via droplets</p> Signup and view all the answers

    What is the primary prevention method for shingles?

    <p>Live attenuated vaccine</p> Signup and view all the answers

    What is the most effective prevention strategy for leprosy?

    <p>Constant surveillance of high-risk populations</p> Signup and view all the answers

    Which of these fungal organisms causes ringworm?

    <p>Trichophyton</p> Signup and view all the answers

    Study Notes

    Skin Defenses

    • Sebum, salt from perspiration, and lysozyme fight microbial growth
    • Skin has a normal microbiota: gram-positive, salt-tolerant bacteria
    • Staphylococci, Micrococci, and Diphtheroids are common skin residents

    Acne

    • Cutibacterium acnes (formerly known as Propionibacterium acnes) is the most common cause
    • It is a gram-positive, aerotolerant-to-anaerobic, nontoxigenic rod
    • C. acnes resides in pilosebaceous glands
    • Sebum can block channels with skin cells leading to acne
    • Mild acne has few scattered pustules, no inflammation, and no scarring
    • Treatment for mild acne: topical agents and salicylic acid preparations
    • Inflammatory/moderate acne has many pustules, slight inflammation, and can spread beyond the face
    • Treatment includes oral accutane (isotretinoin), topical antibiotics, benzoyl peroxide, and visible blue light
    • Nodular cystic/severe acne has hard, painful lesions and a high risk of scarring
    • Treatment includes isotretinoin and oral antibiotics

    Staphylococcus

    • S. aureus is a common inhabitant of the skin and mucous membranes
    • S. aureus are spherical cells in irregular clusters
    • S. aureus are gram-positive, lack spores and flagella, and may have capsules
    • S. aureus grow in large, round, golden-yellow colonies on agar
    • S. aureus is a facultative anaerobe and can withstand high salt, extreme pH, and high temperatures
    • S. aureus produces many virulence factors

    Staphylococcus aureus Virulence Factors

    • Enzymes: Coagulase, Hyaluronidase, Staphylokinase, Penicillinase
    • Toxins: Hemolysins, Leukocidins, Enterotoxin, Exfoliative toxin, Toxic shock syndrome toxin (TSST)

    Staphylococcus aureus Epidemiology

    • Present in most environments frequented by humans
    • Can be isolated from objects or materials that carry infection (fomites)
    • Most commonly found in the anterior nares, skin, and nasopharynx
    • Predisposition to infection includes poor hygiene, poor nutrition, tissue injury, and immunodeficiency

    Staphylococcus Infections

    • Localized Infections: Folliculitis, Furuncle, Carbuncle, Impetigo
    • Systemic Infections: Osteomyelitis, Bacteremia

    Streptococcus pyogenes

    • Group A Streptococcus
    • Gram-positive, spherical, arranged in chains
    • Facultative anaerobe
    • Produces hemolysis on blood agar
    • Expresses surface antigens including C substance, fimbriae, M protein, and capsule

    Streptococcus pyogenes Virulence Factors

    • Extracellular Toxins: Streptolysins (cell and tissue injury), Erythrogenic toxin (fever and rash), Superantigens (strong monocyte and lymphocyte stimulants)
    • Extracellular Enzymes: Streptokinase (digests fibrin clots), Hyaluronidase (breaks down connective tissue)

    Streptococcus pyogenes Epidemiology and Pathogenesis

    • Humans are the only reservoir
    • Asymptomatic carriers exist
    • Transmission: direct contact, droplets, food, and fomites
    • Portal of entry: skin and respiratory system
    • Children are predominantly affected for cutaneous and throat infections
    • Systemic infection and sequelae possible without treatment

    Streptococcus Clinical Disease

    • Skin Infections: Impetigo and Erysipelas
    • Scarlet Fever: Caused by erythrogenic toxin of group A Streptococcus

    Bacillus

    • Gram-positive rods
    • Endospore-forming, motile
    • Mostly saprobic
    • Aerobic and catalase positive
    • Digest complex macromolecules
    • Source of antibiotics
    • Primary habitat is soil

    Medically Important Bacillus Species

    • Bacillus anthracis
    • Bacillus cereus

    Bacillus anthracis

    • Large, block-shaped rod
    • Produces central spores under extreme conditions
    • Virulence factors: polypeptide capsule and exotoxins
    • Causative agent of anthrax

    Types of Anthrax

    • Cutaneous Anthrax: A lesion that begins as a bump, develops into a blister, then an ulcer with a black center
    • Gastrointestinal Anthrax: Caused by ingestion of contaminated food, mortality rate of 50%
    • Inhalational Anthrax: Caused by inhaling endospores, mortality rate of 100%

    Anthrax Control and Treatment

    • Anthrax occurs naturally in cattle, sheep, goats, camels, and antelopes
    • Cattle are routinely vaccinated
    • Vaccines for high-risk occupations and military personnel use toxoids with 6 doses and annual boosters
    • Treatment includes ciprofloxacin or doxycycline

    Gangrene

    • Caused by loss of blood supply to tissue (ischemia) leading to death of tissue (necrosis)
    • Clostridium perfringens causes gas gangrene (rapidly progressing gangrene with foul-smelling gas)

    Gas Gangrene

    • Predisposing factors include surgical incisions, compound fractures, diabetic ulcers, septic abortions, puncture wounds, and gunshot wounds
    • Clostridium perfringens is a gram-positive, endospore-forming anaerobic rod that grows in necrotic tissue

    Clostridium perfringens Virulence Factors

    • Toxins: Alpha toxin (RBC rupture, edema, tissue destruction)
    • Enzymes: Collagenase, Hyaluronidase

    Clostridium perfringens Pathology

    • C. perfringens requires damaged and dead tissue with anaerobic conditions for growth
    • C. perfringens spores germinate and release exotoxins and destructive enzymes
    • Fermentation of carbohydrates in muscle cells produces gas and further tissue destruction

    Treatment and Prevention of Gangrene

    • Immediate cleansing of wounds, deep wounds, compound fractures, and infected incisions
    • Removal of damaged tissue
    • Large doses of cephalosporin or penicillin
    • Hyperbaric oxygen therapy
    • No vaccines available

    Mycobacteria: Acid-Fast Bacilli

    • Gram-neutral, irregular bacilli
    • Acid-fast staining due to mycolic acids in the cell wall
    • Strict aerobe, catalase positive
    • Do not form capsules, flagella, or spores
    • Slow-growing

    Medically Important Mycobacteria Species

    • Mycobacterium tuberculosis
    • Mycobacterium leprae

    Mycobacterium leprae: Leprosy Bacillus

    • Strict parasite that feeds from host carbon sources
    • Cannot be grown on artificial media or tissue culture
    • Slowest growing Mycobacterium species
    • Multiplies inside host cells in globi (large packets)
    • Causes leprosy (Hansen’s disease), a chronic disease starting on the skin and mucous membranes then progressing to nerves

    Epidemiology and Transmission of Leprosy

    • Not highly virulent
    • Risk factors include poor health and crowded living conditions
    • Transmission: droplets
    • Infection requires prolonged direct skin-to-skin contact with an infected person (months)
    • Rare but still exists today
    • Endemic in Asia and Africa

    Course of Infection and Disease

    • M. leprae lives in nasal membranes and skin
    • Macrophages ingest bacilli but M. leprae survives phagocytosis
    • Incubation period is 2-5 years
    • If untreated, bacilli grow in the skin and then migrate to peripheral nerves

    Leprosy Lesions

    • Tuberculoid: Asymmetrical, shallow lesions that damage the nerves resulting in loss of pain sensation
    • Lepromatous: Deep, nodular lesions causing severe disfigurement of the face and extremities

    Leprosy Diagnosis

    • Combination of symptomology, microscopic examination of lesions, and patient’s medical history
    • Symptoms: numbness in hands and feet, loss of sensitivity, muscle weakness, thickened earlobes, and persistent stuffy nose
    • Feather test: detects M. leprae
    • Acid-fast bacilli in skin lesions and nasal discharges

    Leprosy Treatment and Prevention

    • Treatment involves long-term therapy with steroids and antibiotics
    • Prevention includes surveillance of high-risk populations and a currently in-development vaccine

    Human Papillomavirus (HPV)

    • Cause papillomas (warts) - squamous epithelial growth
    • Over 100 HPV strains exist
    • Transmission: direct contact with lesions or contaminated fomites
    • Incubation period is 2 weeks to a year
    • Common warts: small, painless, elevated, rough growth on fingers
    • Plantar warts: deep, painful warts on the soles of feet
    • Genital warts: most common STD in the US, ranges from tiny bumps to cauliflower-like masses

    Treatment and Prevention of HPV

    • Removal of warts: Cryotherapy, electrodesiccation, and salicylic acid
    • Topical drugs: imiquimod and Bleomycin
    • Vaccination against HPV strains

    Herpes Simplex Virus (HSV)

    • Belongs to the Herpesviridae family
    • All strains show prolonged latency and cause recurrent infections
    • Complications occur in older adults, chemotherapy patients, and immunocompromised individuals
    • Common in AIDS patients.
    • Source of many diseases: chickenpox, shingles, mononucleosis, cold sores, and genital herpes
    • HSV infection is prevalent in the population

    Chickenpox

    • Caused by varicella-zoster virus (Herpesvirus 3)
    • Transmission: respiratory route (droplets) and direct contact with rash
    • Pus-filled papules develop on the skin
    • Virus may remain dormant in dorsal root ganglia (spinal nerves)
    • Prevention: live attenuated vaccine

    Shingles

    • Caused by reactivation of latent Herpesvirus 3
    • Virus is released from peripheral nerves back to the skin
    • Rash usually appears on the chest, abdomen, or back but can also develop on the face and genitals
    • Postherpetic neuralgia: burning pain on the skin after rash disappears
    • Prevention: live attenuated vaccine
    • Treatment: acyclovir (antiviral drug) may lessen symptoms

    Rubeola (Measles)

    • Caused by Measles virus
    • Transmission: respiratory route
    • Virus lives in the nose and throat
    • Macular rash on skin and Koplik's spots in the throat and mouth
    • Symptoms last up to 10 days
    • Prevention: vaccination
    • No treatment, it goes away on its own

    Rubella (German Measles)

    • Caused by Rubella virus
    • Macular rash on skin and fever
    • Rash resolves in 5 days
    • In pregnant women, Rubella virus can cause congenital rubella syndrome, leading to severe fetal damage
    • Prevention: vaccination
    • No treatment

    Fungal Infections on Skin: Dermatomycosis

    • Ringworm: caused by Trichophyton, Microsporum, and Epidermophyton (dermatophytes), which produce enzymes that digest keratin
    • Creates a rash on various body parts

    Locations of Ringworm Infection

    • Tinea corporis: body
    • Tinea pedis: athlete's foot
    • Tinea capitis: scalp
    • Tinea barbae: beard
    • Tinea unguium: nails
    • Tinea cruris: groin

    Dermatomycosis Treatment

    • Topical antifungals (e.g., tolnaftate)

    Scabies

    • Caused by the mite Sarcoptes scabiei
    • Mite burrows into skin and lays eggs, causing a rash with intense itching
    • Transmission: direct contact with rash or fomites
    • Treatment: topical insecticides

    Pediculosis

    • Caused by lice (head louse)
    • Affects scalp and skin
    • Lice feed on host blood and lay eggs on hair
    • Transmission: direct contact or sharing belongings
    • Treatment: topical insecticides

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    Explore the mechanisms of skin defenses against microbial growth and the common causes of acne. This quiz covers the role of different bacteria, the types of acne, their characteristics, and treatment options. Discover effective strategies for managing acne at various severity levels.

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