Bacterial Infections - Pyogenic G+ Cocci Flashcards
Staphylococcus aureus
- 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
Furuncles (boils), styes, paronychias, felons
- 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
Carbuncles
- coalescing infections with S. aureus around hair follicle, produce draining sinuses
- lesions mostly on neck
Scalded Skin Syndrome
- 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
Osteomyelitis
- S. aureus
- usually in bones of legs in boys 3-10 yo
- adults over 50 vertebral osteomyelitis
Infections of burns/surgical wounds
- S. aureus
- increased susceptibility in newborn, elderly, malnourished, diabetic, obese
Respiratory tract infections
- S. aureus
- mostly in infants younger than 2 years
- ulcers of upper airway, scattered foci of pneumonia, pleural effusion, empyema, and pneumothorax
Bacterial arthritis
- S. aureus in half of cases of septic arthritis
- 50-70 yo
- predisposed in RA or corticosteroid therapy
Septicemia
- S. aureus, can hit patients with lowered resistance
Bacterial endocarditis
- complication of S. aureus septicemia
- IV drug use predisposition
Toxic Shock Syndrome
- S. aureus
- menstruating women : fever, nausea, vomiting, diarrhea, myalgias –> shock, sunburn like rash
Staphylococcal food poisoning
- S. aureus, preformed toxin in food
- less than 6 hrs after meal
- abrupt nausea/vomiting resolving w/in 12 hrs
Antibiotic-resistant S. aureus
- MRSA - nosocomial or community acquired
- difficult to treat when becomes invasive
Coagulase-negative Staph
- 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
Streptococcus pyogenes
- 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
Streptococcal Pharyngitis
- strep throat
- direct contact with oral or respiratory secretions
- binds to fibronectin of epithelial cells
- tx: penicillin to shorten course and prevent nonsuppurative complications
Scarlet Fever
- S. pyogenes
- punctate red rash on skin in suppurative infections
- tongue with yellow/white coating then beefy red
- caused by erythrogenic toxin
Erysipelas
- S. pyogenes
- erythematous swelling of skin
- begins on face, spreads rapidly
- inflammatory infiltrate of neutrophils
Impetigo
- S. pyogenese or S. aureus
- localized, intraepidermal infection
- spread via direct contact, commonly kids 2-5 yo
- papules –> pustules
Streptococcal cellulitis
- S. pyogenes
- acute spreading infection of loose connective tissue of deeper layers of dermis
Puerperal Sepsis
- S. pyogenes
- Postpartum infection of uterine cavity
- spread by contaminated hands of attendants at delivery
Streptococcus pneumoniae
- aerobic, G+ diplococcus with capsule
- causes pneumonia, otitis media, sinusitis, and meningitis
- commensal organism in oropharynx
Group B Streptococci
- G+ bacteria in short chains
- part of normal vaginal flora in 10-30% women
- leading cause of neonatal pneumonia, meningitis, and sepsis
