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Chapter 18


Boil; results when an inflammation of hair follicle or sebaceous gland progresses into a pustule (S.aureus)


Most common; mild; superficial inflammation of hair follicles (S.aureus)


Deeper lesion created by aggregation of a cluster of furuncles into one large mass; extremely painful (S.aureus)


Slightly more invasive form; edema and redness of the skin near the portal of entry, fever, chills; cutaneous lesions can
remain superficial or cause long term systemic complications

Pyoderma (Streptococcal impetigo)

Burning, itching papules that break and form highly contagious crust


Strep, staph, enterococcus




-Inhabitants of skin and mucous membranes
-Irregular clusters, short chains and pairs

S. aureus

-Among most resistant (high salts, temps, extreme pHs)
-Viable after months of air drying, resists many antibiotics and disinfectants


Coagulates plasma and blood; diagnostic (S.aureus)


Digests the hyaluronic acid that binds connective tissue (S.aureus)
-extracellular in S.pyogenes


Digests blood clots (S.aureus)


Digests DNA (S.aureus)


Inactivates penicillin (S.aureus)


Lyse red blood cells (S.aureus)


Lysis of neutrophils and macrophage (S.aureus)


Act upon gastrointestinal tract (S.aureus)

Exfoliative toxin

Causes skin to peel away; responsible for staphylococcal scalded skin syndrome (S.aureus)

Toxic Shock Syndrome Toxin (TSST)

Probable role in development of toxic shock syndrome (S.aureus)

Bullous Impetigo

Bubble-like epidermal swellings that can break and peel away; most common in newborn (S.aureus)


Pathogen is established in the highly vascular metaphyses of a variety of bones; abscess form (S.aureus)


Primary origin is bacteria from another infected site or from colonized medical devices; endocarditis possible (S.aureus)


As nasopharynx is one of the colonization site, pathogens can be aspirated into lungs and cause pneumonia involving multiple lung abscesses (S.aureus)

Food Intoxication

Ingestion of heat stable enterotoxins; food poisoning; cramping, nausea, vomiting, diarrhea

Staph Scalded Skin Syndrome

Toxemia; upon reaching the skin the toxin induces bright red flush; blisters, then desquamation of the epidermis

Toxic Shock Syndrome

Fever, vomiting, rash, potentially fatal complications involving liver, kidney etc.

S. epidermidis

Infections usually occur after surgical procedures such as insertion of catheters; biofilm formation along with other CNS
-endocarditis, UTI, coagulase negative

S. saprophyticus

Infrequent resident of the skin, lower intestinal tract & vagina; UTI


methicillin-resistant S.aureus

Group A

S. pyogenes

C Carbohydrates

Protect against lysozyme
-surface antigen S. pyogenes

Lipoteichoic acid

-Contributes to adherence
-Bound to fimbriae
-surface antigen S. pyogenes


Resists to phagocytosis, improves adherence
-surface antigen S. pyogenes

Hyaluronic Acid Capsule

Provokes no immune response, antiphagocytic
-surface antigen S. pyogenes


Hemolysin; injure many cells and tissue
-extracellular toxin, S.pyogenes

Erythrogenic (pyrogenic) Toxin

Induces fever and responsible for typical red rash; key toxin in scarlet fever
-extracellular toxin, S.pyogenes


Involved in digestion of fibrin clot
-extracellular, S.pyogenes

Streptococcal Pharyngitis

Strep throat

Scarlet Fever

-Strep throat infection involving S.pyogenes carrying a prophage that codes for erythrogenic toxin
- high fever, diffuse rash
-Systemic infection

Streptococcal Toxic Shock Syndrome

Result of a profound bacteremia and deep tissue infection and rapidly progresses to multiple organ failure
-Systemic infection (S.pyogenes)

Rheumatic Fever

Usually follows an overt or subclinical streptococcal pharyngitis in children; carditis, arthritis, fever, usually without lasting damage; in case of severe carditis, extensive valve and muscle damage possible
-sequelae Group A

Acute Glomerulonephritis

Damaged kidney cells can not adequately filter blood- nephritis, increased blood pressure; occasionally heart failure; may clear or become chronic leading to kidney failure
-sequelae Group A

Group B

Streptococcus agalactiae

Streptococcus agalactiae

Residents of human vagina, pharynx and large intestine
• Because of its location in vagina can be transferred to infant during delivery and can cause severe infection
- most prevalent cause of neonatal pneumonia, sepsis and meningitis
- Pregnant women should be screened for colonization and treated.

Enterococcus faecalis

- normal colonists of human large intestine
- Infections arise most often in elderly patients undergoing surgery and affect the urinary tract, wounds etc
- Group D

Group C and G

Common flora of domestic animals; frequently isolated from human upper respiratory tract; occasionally imitate group A streptococci in causing pharyngitis, glomerulonephritis;
bacteremia in severely compromised patients

Subacute Endocarditis

Blood-borne bacteria settle on heart lining or valves that have been previously damaged by rheumatic fever, valve surgery etc; biofilm formation called vegetation; vegetations release masses of bacteria into circulation
-complication of viridans infections


Involved in 60-70% of bacterial pneumoniawhich primarily affect immunocompromise

Otitis Media

Gains access to the chamber of middle ear by way of eustachian tube and cause a middle year infection called otitis media; occurs readily in children under 2 years


Young children upper respiratory tract infection

Pneumococcal Treatment

• Traditionally treated with penicillin G or V
• Increased drug resistance
• Two vaccines available

Primary Neisseriaceae Pathogens

gonorrhea, mengintidis

Males (gonorrhea)

Infection of urethra causes urethritis with yellowish discharge; can cause infertility (10 percent asymptomatic)

Females (gonorrhea)

Bloody vaginal discharge, painful urination if urethra is infected; in case of ascending infection -PID (pelvic inflammatory disease) possible; can cause sterility (50 percent asymptomatic)

Opthalmia Neonatorum

Gonococcal eye infections in babies during pregnancy
-prevented by prophylaxis immediately after birth

Gonococcal Diagnosis

Gram stain - presence of Gram-negative diplococci


Penicillinase producing N. gonorrhoeae


Tetracycline resistant N. Gonorrhoeae

Meningitis Treatment

Treated with intravenous penicillin G, cephalosprin
• Prophylactic treatment of family members, medical personnel, or children in day care who have come in close contact with infected people
• Vaccines available


Found in nasopharynx; significant opportunist in hosts with disturbed immune functions


Short, plump rods as well as cocci; widely distributed on mucous membranes, weakly pathogenic or non pathogenic

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