ch. 19: bacterial diseases of the skin

normal microbiota of the skin

bacteria

• gram positive aerobic cocci belonging to staphylococcus and microccus

• gram positive anaerobric bacilli uncluding various diphtheriods related to corynebacterium

• microbes can not be removed by normal cleansing

• skin mircibes may become opprtunistic pathogens

bacterial diseases of skin

• cause a wide range of diseases with mil life threatening consequences

diseases caused by s. aures

folliculitis, styes, carbuncles, scalded skin sydrome, impetigo, toxico shock syndrom, bacteremia, food poisoning and pneumonia

staphylococcal virulence factors

enzymes, phagocytic factors, toxins

folliculitis

infection of a hair follicle

most commonly caused by staphylococcus sp.

• facultatively anaerobic- can tolerate sealed environment of buried hair follicle

• salt tolerant- tolerate salty human skin

• desiccation tolerant- can survive on infectious surfaces (fomites) and skin

• transmission- direct contact between individuals or fomites

folliculitis

diafnosis- detection of gram positive bacteria in grapelike arrangments isolated from pus, blood, or other fluids

treatment- s aures is leading cause of nosocomial infections in us, treated with methicillin

staphylococcal scalded skin syndrome (SSS)

signs and symptoms - cells of the skin separates and underlying tissue, outer skin layer peels off

pathogens and virulence factors - strain of staphylococcus aureus, caused exfoliative toxins ( causesiddolution of cellular bride protien)blood will carry the toxins throughtout the body

ssss

pathogenesis- no scarring since the dermis is unaffected, death is rare due to secondary infections, such as yeast

epidemiology- occurs primarily in infants or immune suppressed individuals, transmitted by direct contact

methicillin resistant s. aureus (MRSA)

signs and symptoms: red bumps that develop into deep painful abscesses

pathogens and virulence factors: staphylococcus aureus that exhibit resistance ti methicillin , most resistance to antibiotics

epdiemiolgy: elderly and ummunosuppressed patients and long term healthcare facilities, can occur in healthy people like serious skin, soft tissue and pneumonia like infection

treatment: draining and debriding abcesses

necrotizing fasciitis

signs and symptoms: intense pain and swelling sue to digestion of muscle fascia by bacterium; easily misdiagnosed

pathogens and virulence factor: caused by streptococcus pyogenes

Epidemiology: s. pyogens enters broken skin , spread person to person

acne

• caused by pripionibacterium acnes in 85% of cases

• Epidemiology : prropionibacteria are normal microbita, begins in adolescence

cat scratch fever

• swelling at site of infection , atypical cases involve organ system

• bartonella henselae and bartonella

• cat scratches , bites or blood sucking flea

pseudomonas infection

• fever, chills, and shock and green color due to pigment pyocyanin

• pseudomonas aeruginosa bacterium

• various adhesins, toxins, and polysaccharides capsule, produce toxic form of oxygen

• pathogenesis- grows under the surface of burn

gas gangrene

causative agent: clostridium sp

portal: dead tissue via traumatic event

signs and symp: pain swelling, fever, cracking sounds and bubbles , bad smell

incubation perios: 1 to 3 days

treatment surgical removal of dead tisses

prevention clean wounds

small pox

• 2 -3 days severe ilness

• concetrated on face hans and feet

• change skowly, scabbing 9-15 days

chickenpox

• 0-2 days mild ilness before rash

• concentrated on torso

• change rapidly, crusting over 24 hours

small pox part 2

• caused by orthopoxvirus

• portal is inhalation

• signs and symp: rash, papules

• incubation: 12-14 days

• treatment: vaccine

• prevention vaccination

poxvirus diseases (smallpox)

causes: small pox, cow pox, monkeypox

chickenpox and shingles

• caused by varicellovirud

• portal: repiratory tract, blood (liver/spleen), nerve ganglia (latent),

• incubation perios 2-3 weeks

• effects unvaccinated people and those who have not had it

• prevetion: attenuated vaccine

herpes

• malaise, fever, muscle pain and blister

• portal: break in skin and mucus membrane

HSV-1 & HSV-2

epidemiology

HHV-1: occur via contact by age 2 , 80% of children are asymptomatic

HHV-2: most infection, sexual contact, 15-29 years old

chemotherapeutic drugs help cintril but does not cure it

warts

caused by papiloma virus

transmitted direct contact

some strains contain oncogenes

diagnosed by direct observation

new warts can develop due to latent viruses

laten HPV can lead to cervical cancer