Chapter 19

Question 1

Folliculitis (1)

Answer 1

-Signs & Symptoms:
Infection of the hair follicle -pimple; when it occurs at the eyelid base-sty; Spread of infection into surrounding tissues can produce furuncles-boil; When multiple furuncles grow together-carbuncles

-Pathogen
Caused by Staphlococcus Aureus
Transmitted via fomites
MRSA=Methicillin Resistant Staph Aureus

Treatment: Dicloxacillin

Question 2

Staphylococcal Scalded Skin Syndrome (2)

Answer 2

-Signs & Symptoms:
Skin becomes red and wrinkled & forms blisters; Outer epidermis peels off in sheets

-Pathogen & Virulence Factors
Some Staphylococcus Aureus strains; 1 or 2 EXFOLIATIVE TOXINS cause SSSS

-Pathogenesis
No scarring because dermis is unaffected; Death is rare but most often due to secondary infections

-Epidemiology
Disease occurs primarily in infants; Transmitted by person-to-person spread of bacteria

-Diagnosis, treatment, & prevention
Diagnosed by characteristic soughing of skin; Treated by administration of antimicrobial drugs; Widespread presence of S. aureus makes prevention difficult

Question 3

Impetigo (Pydoderma 3)

Answer 3

-Signs & Symptoms:
Red patches form on the face and limbs

-Pathogens & Virulence factors
Most cases are caused by S. Aureus; Some cases caused by Streptococcus Pyogens

-Pathogenesis
The bacteria invade where the skin is compromised; Acute glomerulenephritis can result if infection spreads to the kidneys

-Epidemiology
Transmitted by person-to-person contact via fomites; impetigo occurs mostly in children

-Diagnosis, treatment, and prevention
The presence of vesicles is diagnostic for impetigo; red patches of skin with HONEY-COLORED CRUSTS; Impetigo is treated with oral and topical antimicrobials and careful cleaning of infected areas

Question 4

Erysipelas (4)

Answer 4

-Signs & Symptoms:
Infection Spreads to the lymph nodes

-Pathogens & Virulence factors
Most cases are caused by S. Aureus; Some cases caused by Streptococcus Pyogens

-Pathogenesis
The bacteria invade where the skin is compromised; Acute glomerulenephritis can result if infection spreads to the kidneys

-Epidemiology
Transmitted by person-to-person contact via fomites; Erysipelas can also occur in the elderly

-Diagnosis, treatment, and prevention
Red patches of skin, Treated with penicillin

Question 5

Necrotizing Fasciitis (5)

Answer 5

-Signs & Symptoms
Redness, intense pain, and swelling at infection site; Develop fever, nausea, malaise, and possible mental confusion

-Pathogen and Virulence Factors
Most Cases are caused by S. Pyogense

-Pathogenesis
S. Pyogenes enters through breaks in the skin

-Epidemiology
Usually spread from person to person; Death occurs in about 20% of patients

Question 6

Acne (6)

Answer 6

-Pathogen

Commonly caused by Propionibacterium acnes

Question 7

Cat Scratch Disease (7)

Answer 7

-Signs & Symptoms
Fever, malaise, localized swelling at infection site; Swollen lymph nodes

-Pathogen & Virulence Factors
Caused by Bartonella Henselae (Gram-negative bacillus)

-Pathogenesis & Epidemiology
Transmitted by cat bites/scratches or blood-sucking arthropods

Question 8

Pseudomonas Infection (8)

Answer 8

-Signs & Symptoms
Blue-green color from the bacterial pigment; PYOCYANIN, occurs in massive infections

-Pathogen & Virulence Factors
Pseudomonas aeruginosa is the causative agent

Question 9

Rocky Mountain Spotted Fever (RMSF) (9)

Answer 9

-Pathogen
Rickettsia rickettsi (bacteria)

-Signs & Symptoms
Petechaie non itchy spotted rashes on trunk and appendages often on hands and feet, transmitted by infected tick (DERMACENTOR SP.)

Question 10

Cutaneous Anthrax (10)

Answer 10

Caused by Bacilus anthracis
Characterized by Eschar (black painless ulcer)
Treated with antimicrobial drugs
Prevention requires control of disease in animals

Question 11

Gas Gangrene (11)

Answer 11

-Signs and Symptoms
Death of muscle & connective tissue; blackening of infected muscle & skin/presence of gas bubbles

-Pathogens & Virulence Factors
Caused by Several Clostridium species; C. perfringens is most often isolated

-Pathogenesis & Epidemiology
Traumatic event must introduce endospores into dead tissue, mortality rate exceeds 40%

-Diagnosis, treatment, & prevention
Appearance is usually diagnostic; rapid treatment is cruicial, surgical removal and antitoxins; prevented with proper cleaning of wounds

Question 12

Diseases of Poxviruses (12)

Answer 12

Poxvirus that cause human diseases; Smallpox; Smallpox if the first human disease to be eradicated

-Signs & Symptoms
Diseases progress through a series of stages

-Pathogens & Virulence Factors
Poxvirus are envoloped in dsDNA virus; ORTHOPOXVIRUS causes smallpox

-Pathogenesis
Smallpox infection occurs by inhalation of virus; spreads through respiratory tract; some by direct contact

-Epidemiology
Variola virus stocks are maintained in U.S. and Russian labs for research

-Diagnosis, Treatment, Prevention
Treatment requires immediate vaccination; Vaccination discontinued in 1980’s

Question 13

Herpes Infections (13)
HHV (Human Herpes Virus)

Answer 13

HHV1-mostly cold sores

HHV2-mostly genital herpes

Question 14

Warts (14)

Answer 14

Papilomavirus: non envoloped dsDNA (60 different strains)

-Most are harmless; may precipitate some cancers

Question 15

Chickenpox & Shingles (15,16)

Answer 15

-Signs & Symptoms
Chickenpox: Highly contagious infectious disease; characterized by lesions on the back & trunk that spread across body; Virus becomes latent within sensory nerves VARICELLA ZOSTER
Shingles: Occurs following reactivation of virus; Lesions are localized to skin along an infected nerve; pain may last after lesions have healed HERPES ZOSTER

-Epidemiology
Chickenpox occurs mostly in children; VZV infected 90% of children prior to immunization; more severe in adults; Risk of shingles increases with age

-Diagnosis, treatment, and prevention
Diagnosis based on characteristic lesions; treatment based on relief of symptoms; vaccine available against chickenpox

Question 16

Rubella (17)

Answer 16

-Signs & Symptoms
Children develop a mild rash; adults may develop arthritis & encephalitis; Congenital infection can result in birth defects or death of fetus

-Pathogen & Pathogenesis
Caused by rubella virus: RIBOVIRUS (+ssRNA virus)
AKA German measles

-Signs & Symptoms
Characterized by KOPLIK’S SPOTS; Subacute sclerosing panencephalitis (SSPE) is complication

-Pathogen & Virulence Factors
Caused by Measles virus (Morbillivirus (-ssRNA virus)
Adhesion and fusion proteins helps virus avoid recognition

-Pathogenesis
Immune response to infected cells causes most symptoms; disease can be fatal in children

-Epidemiology
Measles is highly contagious; spread via respiratory droplets; vaccination helps reduce spread; MMR vaccine protects against measles

Question 17

Measles (Rubeola) (18)

Answer 17

-Signs & Symptoms
Characterized by Koplik’s spots
SUBACUTE SCEROSING PANENCEPHALITIS (SSPE) is rare complication

-Pathogen and virulence factors
Caused by measles virus :Morbillivirus (ssRNA Virus); adhesion and fusion proteins help virus avoid immune recognition

-Pathogenesis
Immune response to infected cells causes most symptoms; disease can be fatal in children

-Epidemiology
Measles is highly contagious; Spread via respiratory droplets; vaccination has reduced spread of the disease; MMR vaccine protects against measles

Question 18

Erythema Infectiosum (19)

Answer 18

Also referred to as fifth disease; caused by Erythrovirus (B19); respiratory disease that manifests as a rash; adults may also develop anemia and joint pain

Question 19

Roseola (20)

Answer 19

Endemic disease of children; caused by human herpesvirus (HHV-6); characterized by a rose-colored rash

Question 20

Pityriasis Versicolor (21)

Answer 20

Hypo- or hyperpigmented patches of scaly skin

-Pathogens & Virulence Factors
Caused by Malessezia Furfur; normal inhabitant on the skin

Diagnosis, treatment, and prevention
Infected skin is page green under ultraviolet light; definitive diagnosis requires microscopic examination

Question 21

Dermatophytoses (22)

Answer 21

Cutaneous lesions caused by some fungi that grow in the skin; caused by dermatophytes

Pathogens: 3 genera cause dermatophytoses: Microsporum, trichophyton, epidermohyton floccosum

Pathogenesis: Dermattophytes colonize skin, nails, and hair; use keratin as nutrient source; infection is rare; limited infections treated with topical agents

Question 22

Chromoblastomycosis (23)

Answer 22

Can infect wounds, not easily treated; people who work barefoot in the soil are at risk; wearing shoes reduces number of infections

Question 23

Phaeohyphomycosis (24)

Answer 23

Includes fungi that invades traumatic or surgical wounds; immunocompromised

Question 24

Mycetomas (25)

Answer 24

Caused by several genera of soil fungi; pricks and scrapes introduce fungi into people; people who work barefoot in soil most at rick; tumorlike lesions form on skin, fascia, and bones

Question 25

Sporotrichosis (26)

Answer 25

Caused by Sporothrix schencki- resides in the soil; pricks & splinters introduce fungi into humans; occurs most often in GARDENERS AND FARMERS

Question 26

Leishmaniasis (27) PROTOZOA

Answer 26

LEISHMANIA is the causative agent (found in animals)- zoonosis; PROTOZOAN transmitted by FEMALE SAND FLIES (VECTOR) -Sign & Symptoms CUTANEOUS-MOST INDIVIDUALS RECOVER ; produces large painless skin lesions MUCOCUTAENOUS-MOST INDIVIDUAL RECOVER: Skin lesions enlarge to encompass mucous membranes VISCERAL (KALA-AZAR) OFTEN FATAL: Parasite is spread by macrophages throughout the body -Pathogenesis & Epidimediology Infected macrophages stimulate inflammatory responses; Leishmaniasis is endemic part of the TROPICS & SUBTROPICS) -Diagnosis, Treatment, and Prevention: MOST CASES HEAL WITHOUT TREATMENT; Diagnosed by microscopic identification of the protozoa; antimicrobials are needed for severe infections; Prevention involves reducing exposure to reservoir host

Question 27

Scabies (28)

Answer 27

-Signs & Symptoms Characterized by intense itching & rash at infection site; Lesions common between fingers, around the genitalia, wrists, elbows and knees -Pathogen and Virulence Factors The mite SARCOPTES SCABIEI is the causative agent; Inflammation and damage to nerve endings occur as the mites burrow -Pathogenesis & Epidemiology EPEDEMICS OCCUR IN CROWDED CONDITIONS; Itching blisters occur where females mites lay eggs; mites transmitted via prolonged body contact -Diagnosis, treatment, and Prevention NO IMMUNITY; Diagnosis made by observing mites, often in skin folds between fingers, along wrist; treated with mite-killing lotions and cleaning of contaminated items