The normal biota of the skin is composed of bacteria and
Pathogenesis of Acne
Abnormal follicular keratinization and occlusion
Excessive oil/sebum production
Release of inflammatory Mediators
Pt. presents with multiple follicular lesions with periods of improvement and exacerbation. Lesions are open and closed comedone, inflammatory papules, pustules, nodules and cysts presenting on back, face, neck, upper chest. What do they have? What are the associated symptoms?
Associated-oiliness, post-inflammatory hyper/hypo pigmentation, atrophic or hypertrophic scars, excoriations
How do you diagnose acne?
Lesions in characteristic locations
Prevention and Treatment of Acne
Topical Sloghing agents
Primary etiologic agent of acne
G+, Rod bacteria that occurs in short chains/clumps.
How does Propionibacterium acne cause infection?
Digestive products + bacterial antigens = local inflammation
Benzoyl peroxide, erythromycin, and benzoyl peroxide/erythromycin combinations are used to treat
Pt. presents with non-bulbous, single/multiple isolated or coalescent small, superficial pustules that progress to erosions with honey-colored crusts. What is the bacterial infection?
Impetigo by either Staph. aureus or Strep. pyogenes.
Pt. presents with bullous (blister-like) bullae, with minimal/no inflammtion. Areas of blister rupture are covered with varnish-like brown crusts. What is the bacterial infection?
Impetigo -Staph. aureus or Strep. pyogenes
Who generally becomes affected by impetigo?
Children 2-5, often contagious with poor hygiene/minor trauma
Acute, superficial pyoderma
What bacteria can cause cellulitis?
What common clinical infection can be caused by Streptococci (S. pyogenes), Enterobacteriaceae, Clostridium perfringfrens, Bacteriodes gradilis, and MRSA?
What are the organisms of HACEK? What is the importance of the this group?
Haemophilus Actinobacillus Cardiobacterium Kingella ***Agents of endocarditis
What etiologic agents should you be concerned about following a Dog Bite? A Cat bite?`
Dog-P. Canis Cat-Pasteurella multocida
What clinical features follow a bite from a domestic animal?
Local abcess with swelling and discoleration associated with bites
Hansen's Dz is also known as ____ and is caused by _____.
Leprosy Mycobacterium leprae
Acid-fast positive bacteria with lengthy generation time, with slow clinical manifestation. Pt. can present with either tuberculoid or lepromatous forms, is caused by what bacteria?
The primary reservoirs of Mycobacterium leprae are:
What is the treatment for leprosy? How is it transmitted?
Long term Anitbiotics Person-person transmission
The majority of Staphylococcaceae infections are caused by:
S. aureus S. epidermidis S. saprophyticus
What species are Staphyloccocae are Coagulase negative?
S. epidermidis S. saprophyticus
What species are Staphyloccocae are Coagulase positive?
What is the most common cause of suppurative (pus-forming) diseases seen in medical practices?
S. aureus often causes _____ infections, of what body part?
Nosocomial Skin infections
You are looking at a G+, bacteria arranged in clusters of cocci.
The peptidoglycan of S. aureus is susceptible to ______.
Pt. presents with suppurative infection on upper arm. Culture is positive for Catalase, coagulase, and staphylokinase. The bacteria is susceptible to lysostaphin. What is the bacteria?
What are the types of toxins that S. aureus produces?
Cytolytic Enterotoxins Exfoliative Toxins TSST-1
What do Cytolytic Toxins do? Give an example
membrane-active exotoxins that lyse RBCs and other cells.
What do enterotoxins cause? How are they successful?
Cause Food Poisioning. They are resistant to gastric enzymes and heating, and act as a Superantigen
What do exfoliative toxins cause? How do they work?
Cause Scalded-skin syndrome
Due to lysis of intracellular attachment between cells of the granular layer of the epidermis occurs
Methicillin Sensitive S. aurues -treate with oxacillin or nafcillin
What is a G+
What is a G+, cocci, with fibrils that presents in pairs or chains (diplocci) lancet-shaped.
Streptococcaceae, specifically S. pneumoniae
How do Streptococcaceae species modify hemoglobin?
α-hemolysis-partial lysis associated with reduction of Hb produces a greenish/brownish discoloration. β-hemolysis-complete lysis of RBCs with a clear zone surrounding colony γ-hemolysis-no lytic activity
GAS bacteria that establishes infection by preventing phagocytosis by M protein and hyaluronic acid. Uses streptokinase
What are the Virulence Factors of S. pyogenes?
Strep Pyrogenic Exotoxins
DNAse and hyaluronidase
What is M protein?
fibrous protein in the cell surface that protects cell from phagocytosis. Can act as an adhesion. **S. pyogenes
What is Streptolysin O?
lyses blood cells by causing transmembrane pores.
How do you test for GAS infections?
look for antibodies formed against antigen= anti-streptolysin O (ASO) test
What is streptolysin S
lyses red and white blood cells that are responsible for beta-hemolysis on blood agar.
What are Strep pyrogenic exotixins (Spes)?
super-antigens that are involved in the development of the rash observed with scarlet fever.
Clinical manifestations of the skin of S. pyogenes?
What is an acute infection of the skin with localized pain in an area that is raised, erythematous and warm?
what are common associated symptoms of Erysipelas?
LN enlargement, chiills, and fever.
S. pyrogenes is responsible for what non-skin infections?
Pharyngitis Scarlet Fever Strep TSS Bacteremia
Pt. presents with pharyngitis-like symptoms, with a skin rash that first appears on upper chest then spreads to trunk, neck, and extremities. Also, appears with strawberry tongue, followed by a raspberry tongue. What are they suffering from? What bacteria has caused it?
Scarlet fever caused by s. pyogenes
Describe the clinical manifestations of Strep TSS
resembles staph TSS with hypotension, renal failure, and red rash.
What bacteria are G+, rods that form spores that are obligate anaerobes?
What bacteria causes infection by lowering oxidation-reduction potential, release alpha toxins, and use edema and gas to promote spread.
What are the two wound infections caused by C. perfringens?
Clostridial cellulitis Gas Gangrene
Infection of tissue that is already dead and produces gas
invasive infection associated with toxemia, local edema, foul-smelling exudate, with various amounds of gas. That may cause septicemia, massive hemolysis and renal failure.
Gas Gangrene, due to C. perfingens
What form of food poisoning presents with diarrhea, cramps, and abdominal pain roughly 8-24 hours folloinw ingestion?
**No Vomit C. perfringens
Loss of intestinal mucosa with bleedin into the stool can be symptom of ______
Necrotic enteritis due to C. prefringens.
How to diagnose C. perfringens infection
clinical symptoms gram stain & culture Nagler test (alpha toxin)
Treatment of C. perfringes
Cellulitis-remove necrotic tissue, antbiotics Gas Gangrene-remove infected area, high does antibiotics, hyperbaric oxygen (inhibits alpha toxin)
G+ rods that produce endospores with high resistance to chemical and physical environments
Pathogenesis of Bacillus anthracis
spore enter through small abrasion and multiply with dramatic inflammatory response. Can occur with toxemia
pt presents with small papule that later developed into a vesicle filled with dark, bluish-black fluid. Rupure causes a black eshar.
Bacillus anthracis occurs 2-5 days after exposure.
what is the natural reservoir for Bacillus anthracis
herbivorous animals endemic in Africa and Middle East (US via imports)
Diagnosis of Bacillus anthracis
culture on blood agar, PCR
Treatment and Prevention of Bacillus anthracis
Treat-antibiotics Prevention-sterilizaion of animal products, immunization of herbivorous animals, and humans vial cell-free filtrate.
Who receives vaccination against Bacillus anthracis?
Military and those in industrial settings
Tears contain _____ and _____ for protection
lysozyme and lactoferrin
Difference between Bacterial and Viral infections of the eye
Bacterial-milky discharge Viral-clear exudate
What are the common causes of neonatal eye infection?
Neisseria gonorrhoeae Chlamydia tracomatis
G-, diploccocci bacteria that often presents with PMNs
G-, cocci, obligate intracellular parasite with inclusion bodies in infected host cells.
What are the major causes of bacterial conjunctivitis in everyone except neonates?
S. epidermidis S. pyogenes S. pneumoniae H. influenzae Moraxella
G-, bacillus found in normal flora of upper respiratory tract. Most commonly causes otitis media (children) and bronchitis/bronchopneumonia (elderly)
Viral conjunctivitis is usually caused by
pt presents with clouded and casularized cornea with scarred and malformed eyelids. Trichiasis (inward groth of eyelids) presents. What do you think is the dz and cause of infection?
Trachoma due to Chlamydia trachomatis
Infection of Chlamydia trachomatis
infection of conjunctival epithelial cells that cause subepithelial infiltration of lymphocytes that lead to the development of follicles. Follicles-infected epithelial cells that contain cytoplasmic inclusion bodies.
Keratitis is caused by
HSV-1 and -2
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