Bacterial Infections - Pyogenic G+ Cocci

Question 1

Staphylococcus aureus

Answer 1

• grows in clusters, normally resides on skin
• causes suppurative infection
• coagulase positive
• survives on inanimate surfaces for long periods
• most commonly affects skin, bones, joints, heart valves

Question 2

Furuncles (boils), styes, paronychias, felons

Answer 2

• all from S. aureus
• furuncle - infection in hair follicle, central core becomes necrotic and fluctuant
• stye - boils of sebaceous glands around eyelid
• paronychia - infection of nail bed
• felon - infection on palmar side of fingertips

Question 3

Carbuncles

Answer 3

• coalescing infections with S. aureus around hair follicle, produce draining sinuses
• lesions mostly on neck

Question 4

Scalded Skin Syndrome

Answer 4

• S. aureus
• infants/children younger than 3
• sunburn like rash beginning on face and traveling to rest of body
• bullae form and skin easily desquamates due to exotoxin

Question 5

Osteomyelitis

Answer 5

• S. aureus
• usually in bones of legs in boys 3-10 yo
• adults over 50 vertebral osteomyelitis

Question 6

Infections of burns/surgical wounds

Answer 6

• S. aureus

- increased susceptibility in newborn, elderly, malnourished, diabetic, obese

Question 7

Respiratory tract infections

Answer 7

• S. aureus
• mostly in infants younger than 2 years
• ulcers of upper airway, scattered foci of pneumonia, pleural effusion, empyema, and pneumothorax

Question 8

Bacterial arthritis

Answer 8

• S. aureus in half of cases of septic arthritis
• 50-70 yo
• predisposed in RA or corticosteroid therapy

Question 9

Septicemia

Answer 9

• S. aureus, can hit patients with lowered resistance

Question 10

Bacterial endocarditis

Answer 10

• complication of S. aureus septicemia

- IV drug use predisposition

Question 11

Toxic Shock Syndrome

Answer 11

• S. aureus

- menstruating women : fever, nausea, vomiting, diarrhea, myalgias –> shock, sunburn like rash

Question 12

Staphylococcal food poisoning

Answer 12

• S. aureus, preformed toxin in food
• less than 6 hrs after meal
• abrupt nausea/vomiting resolving w/in 12 hrs

Question 13

Antibiotic-resistant S. aureus

Answer 13

• MRSA - nosocomial or community acquired

- difficult to treat when becomes invasive

Question 14

Coagulase-negative Staph

Answer 14

• S. epidermidis - major cause of infections involving medical devices (IV, heart valves, pacemakers, prostheses, CSF shunts, peritoneal catheters)
• S. saprophyticus - 10-20% UTIs in women
• form biofilms and cause acute inflammatory infiltrate
• treat with non B-lactam Abx

Question 15

Streptococcus pyogenes

Answer 15

• group A strep
• G+ coccus frequently on skin and oropharynx
• suppurative - site of bacterial invasion, tissue necrosis, acute inflammation
• non suppurative diseases - remote sites, rheumatic fever or acute poststreptococcal glomerularnephritis
• erythrogenic exotoxins (scarlet fever) and cytologic exotoxins

Question 16

Streptococcal Pharyngitis

Answer 16

• strep throat
• direct contact with oral or respiratory secretions
• binds to fibronectin of epithelial cells
• tx: penicillin to shorten course and prevent nonsuppurative complications

Question 17

Scarlet Fever

Answer 17

• S. pyogenes
• punctate red rash on skin in suppurative infections
• tongue with yellow/white coating then beefy red
• caused by erythrogenic toxin

Question 18

Erysipelas

Answer 18

• S. pyogenes
• erythematous swelling of skin
• begins on face, spreads rapidly
• inflammatory infiltrate of neutrophils

Question 19

Impetigo

Answer 19

• S. pyogenese or S. aureus
• localized, intraepidermal infection
• spread via direct contact, commonly kids 2-5 yo
• papules –> pustules

Question 20

Streptococcal cellulitis

Answer 20

• S. pyogenes

- acute spreading infection of loose connective tissue of deeper layers of dermis

Question 21

Puerperal Sepsis

Answer 21

• S. pyogenes
• Postpartum infection of uterine cavity
• spread by contaminated hands of attendants at delivery

Question 22

Streptococcus pneumoniae

Answer 22

• aerobic, G+ diplococcus with capsule
• causes pneumonia, otitis media, sinusitis, and meningitis
• commensal organism in oropharynx

Question 23

Group B Streptococci

Answer 23

• G+ bacteria in short chains
• part of normal vaginal flora in 10-30% women
• leading cause of neonatal pneumonia, meningitis, and sepsis