Ch. 21 Microbial Diseases of the Skin and Eyes Flashcards
eyes get their microbiota from…
the skin
normal microbiota of the skin (three general characteristics related to the environment they are in) (cross contact into eye)
- halotolerant
- acid tolerant
- resistant to drying
types of microbes on the skin
- gram-positive cocci
- diptheroids (pleomorphic, rods)
- — propionbacterium (metabolize sebum, produce acid)
- — cornybacterium
- yeasts
- — malassezia (require oil for growth)
bacterial diseases of the skin
- Staphylococcus
- S. epidermidis (coagulase negtive)
- — most common cause of infection in indwelling devices; creates biofilms
- — not a problem on the skin, but wrong location - bad
- S. aureus (coagulase positive)
- — many virulence factors
examples of S. aureus skin diseases
- MRSA (methicillin resistance)
- toxic shock syndrome (TSST-1)
- — produces toxins that decrease blood pressure
- impetigo (scabs around mouth; v. contagious)
Bacterial diseases of the Skin
- Staphylococcus
- Streptococcus
- Psuedomonas
- Acne
Viral diseases of the skin
- warts
- smallpox (variola)
- varicella-zoster virus
- cold sores
- measles
- rubella
Staphylococcus diseases of the skin
S. aureus (coagulase positive; many virulence factors)
S. aureus causes…
Scalded skin syndrome (exotoxin; small children or late-stage TSS)
Streptococcus diseases
S. pyogenes:
- beta-hemolytic
- Group A Streptococcus (GAS)
- has M protein (allows microorg to evade phagocytosis)
- still sensitive to beta-lactam antibiotics
Diseases caused by S. pyogenes
Erysipelas (often after strep throat)
Necrotizing fasciitis (flesh eating disease)
Streptococcal TSS
Pseudomonas disease-causing organisms (pseudomonad)
P. aeruginosa
- lophotrichous
- green pigment on petri dish
Diseases caused by P. aeruginosa
Pseudomonads dermatitis ("swimmer's itch" rash)
Otitis externa (external ear canal infection)
Opportunistic pathogen (HAI 2nd and 3rd degree burn patients)Acne
Comedal acne (mild) Inflammatory acne (moderate) Nodular cystic acne (severe)
How do propionibacterium cause acne
normally it metabolises fatty acids in sebum, creating an acidic environment and acting as a first line of defense.
excess skin shedding in hair follicles block the follicle, leading to accumulation of sebum and infection by propionibact.
Warts are caused by…
papillomavirus
smallpox is caused by …
Variola virus: variola major (over 20% mortality) and minor (less than 1% mortality)
eradicated, as it has no animal hosts
chickenpox is caused by…
varicella-zoster virus (human herpes virus 3 HHV-3)
HHV-3 characteristics
- DNA virus
- transmitted via respiratory route
- incubation about 3 wks
- virus migrates up peripheral nerves to dorsal root ganglion; latent viral DNA
- pock marks
- mostly mild in children, very severe in young adults
recurrence of HHV-3
shingles (herpes zoster)
- viruses move down peripheral nerve
- often occurs later in life
Reye’s syndrome
occurs post-chickenpox
vomiting, lethargy, coma, and eventual death
mortality previously was 90%; now, 30%
chickenpox can be prevented by…
attenuated vaccine
cold sores are caused by…
Herpes simplex virus type 1
- oral or respiratory route
- virus can travel up trigeminal nerve to ganglion where it is latent
other diseases caused by HSV-1
Herpes gladiatorum (wrestling mats; raised bumps) Herpetic whitlow (medical professionals; from nasal or mucosal secretions)
