Skin Defenses and Acne Treatment

Podcast

Play an AI-generated podcast conversation about this lesson

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?

Formation of superficial lesions Signup and view all the answers

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

Streptokinase Signup and view all the answers

What component in sebum is known for its antimicrobial properties?

Fatty acids Signup and view all the answers

Which bacteria are primarily responsible for normal skin microbiota?

Staphylococci Signup and view all the answers

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

Mild Acne Signup and view all the answers

What treatment is commonly prescribed for moderate acne?

Topical antibiotics Signup and view all the answers

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

Cutibacterium acnes Signup and view all the answers

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

Cystic Acne Signup and view all the answers

Which characteristic is typical for Staphylococcus aureus?

Producing various virulence factors Signup and view all the answers

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

Benzoyl peroxide Signup and view all the answers

What function does penicillinase serve in Staphylococcus aureus?

Inactivates penicillin Signup and view all the answers

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

Toxic shock syndrome toxin (TSST) Signup and view all the answers

What is a common predisposing factor for Staphylococcus aureus infections?

Immunodeficiency Signup and view all the answers

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

Osteomyelitis Signup and view all the answers

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

Impetigo Signup and view all the answers

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

Digests connective tissue Signup and view all the answers

How does food intoxication occur in relation to Staphylococcus aureus?

By the production of heat-stable enterotoxins Signup and view all the answers

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

Carbuncle Signup and view all the answers

What is a characteristic feature of cutaneous anthrax lesions?

They begin as a raised bump. Signup and view all the answers

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

Endotoxins Signup and view all the answers

What type of infection is scarlet fever primarily associated with?

Streptococcal infections Signup and view all the answers

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

They are endospore-forming and motile. Signup and view all the answers

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

They ensure proper treatment to prevent complications. Signup and view all the answers

What is the mortality rate associated with gastrointestinal anthrax?

50% Signup and view all the answers

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

Inhalational (pulmonary) anthrax Signup and view all the answers

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

Penicillin Signup and view all the answers

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

Alpha toxin Signup and view all the answers

What is the incubation period for leprosy?

2-5 years Signup and view all the answers

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

Tuberculoid lesions Signup and view all the answers

Which method is commonly used for the diagnosis of leprosy?

Detection of acid-fast bacilli Signup and view all the answers

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

HPV causes a variety of skin warts Signup and view all the answers

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

Laser therapy Signup and view all the answers

How is chickenpox primarily transmitted?

Respiratory route via droplets Signup and view all the answers

What is the primary prevention method for shingles?

Live attenuated vaccine Signup and view all the answers

What is the most effective prevention strategy for leprosy?

Constant surveillance of high-risk populations Signup and view all the answers

Which of these fungal organisms causes ringworm?

Trichophyton 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

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

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.