PYOGENIC GRAM+COCCI

Question 0

staphylococcus aureus = COAGULASE + (THATS WHY ITS IN CLUSTERS…DUHHHH

Answer 0

-normal flora (skin,clothing) and survives in inanimate objs for long. most common source of suppurative infections of SKIN, JOINTS, BONES. LEADING CAUSE OF INF ENDOCARTITIS (heart valves)
1. suppurative infections: begin as localized skin info –> cellulitis and abscesses (pus-filled), then blood –> skin, bone, joints, heart valves.
furuncles, carbuncles (neck), styes (eyelids sebaceous glands), paronychias (nail beds), felons (fingertips), scalded skin sd (50yr, vertebral osteomyelitis)
-respiratory tract inf: infants rash
3. Food poisoning: caused by PRE-FORMED TOXINS in food; BEGINS <6hr post meal, N+V, resolves w/i 12hr

Question 1

5 pyogenic gram + cocci

Answer 1

1. staphylococci aureus
2. coagulase-negative staphylococci
3. streptococcus pyogenes
4. streptococcus pneumoniae
5. group b streptococci

Question 2

coagulase - staphylococci

Answer 2

-half of the species are normal flora, causes LOW GRADE FEVER
-major cause of inf in MEDICAL DEVICES (IV catheters, prosthetic valves) - staphylococci epidermitis
-staph saprophyticus causes 10-20% UTI in women
-HAVE POLYSACCHARIDE GEL BIOFILM (attach, evade ab’s). contaminates foreign bodies and proliferate slow –> inflm response. lack enzymes to cause extensive local tissue damage (NOT TOO MUCH PUS), most have mecA gene (resists b-lactam)
TX: replace device, non-b-lactams

Question 3

streptococcus pyogenes

Answer 3

AKA GROUP A STREP, normal flora of oropharynx and skin
has ERYTHROGENIC and CYTOLYTIC TOXINS. streptolysins S: lyses bacterial protoplasts and destroys PMNs after they ingest s. pyogenes. streptolysin O: causes persistent high Ab titer.

-CAUSES SUPPURATIVE AND NONSUPPURATIVE, TOXIN-RELATED IMMUNOLOGIC RXNS.

SUPPURATIVE: pharyngitis, impetigo, cellulitis, myositis, pna, puerperal sepsis

nonsuppurative = sites far from local bacterial inf: rheumatic fever, acute poststreptococcal glomerulonephritis

strep throat, impetigo, cellulitis, erysipelas, scarlet fever, rheumatic fever, post-strep GN

Question 4

strep throat

Answer 4

strep throat = pharyngitis, spread by oral/resp secretions
S. pyogenes has M protein that helps it avoid complement deposition on bacterial surface, has surface proteins that destroys C5a ==> produce PMN exudate on tonsillar fossae
SX: SORE THROAT, FEVER, MALAISE, INC WBC, last 3-5ds, may lead to RHEUMATIC FEVER OR POST-STRP GN (TX: give penicillin to prevent nonsuppurative sequelae)

Question 5

impetigo

Answer 5

impetigo: insect bite inoculates organism into skin;;;spread by direct contact, 2-5yrs
localized intraepidermal inf caused by staph aureus/strep pyogenes –> intraepidermal pustule (exudate/purulent)–> crust, may lead to poststrep-GN, NOT NOT NOT RHEUMATIC FEVER

Question 6

S. pyogenes: erysipelas

Answer 6

• warm climates, >20yrs old, begins on face –> spreads to sc tissues. usually PMNs, most intense around vessels and adnexa of skin.
• common micro-abscesses, necrotic foci

Question 7

S. pyogenes: cellulitis

Answer 7

spreading inf of LCT

• suppurative
  cause: traumatic inoculation, freq occurs in extremities bc of impaired lymphatic drainage

Question 8

S. pyogenes: Scarlet fever

Answer 8

Scarlatina, caused by ERYTHROGENIC TOXIN

• PUNCTATE RED RASH ON SKIN AND MUCOUS MEMBRANES (commonly caused by pharyngitis, some suppurative S. pyogenes)
• begins in chest and spreads to extremities, TONGUE: white coating –> sheds –> beefy red surface

Question 9

streptococcus pneumoniae = PNEUMOCOCCUS (splenectomy)

Answer 9

-aka PNEUMOCOCCUS - pyogenic infs, major cause of LOBAR PNA
-commensal: oropharynx, most strains have a polysaccharide capsule (prevents alt pathway) and secrete IgA PROTEASE
***causes otitis media (by age 5), sinusitis (by age 5), MENINGITIS. otitis and sinusitis usually preceded by viral infection (ex: common cold)
RISK: insults to resp defenses (viral, ROH, smoking), underlying dz: diabetes, compromised bacterial opsonizatoin,
SPLENECTOMY (HIGH RISK OF FULMINANT SEPTIC SHOCK AND DEATH (b/c lack activated macrophages))

alv fills with proteinous fluid, PMNs, fluids. resolves completely (unlike s. aureus which does permanent damage)

Question 10

group B streptococci

Answer 10

gram +, grows in short chains
normal flora of vagina in 10-30% of women.
LEADING CAUSE OF NEONATAL PNA, MENINGITIS, SEPSIS (30% babies die)
RF: premature delivery (dec specific IgG from mom)
also new borns: may spread to CNS or lungs or disseminated bc low defenses. involved tissues show pyogenic response