Staphylococci Flashcards
Cocci bacteria
staph, strep, enterococcus
bacilli: Spore forming
- Bacillus (facultative anaerobe)
- Clostridium (obligate anaerobe)
Bacilli: Non-spore forming
- Listeria
- Corynebacteria
Strep
catalase negative
Staph
catalase positive
What kind of infection are Staph and Strep common in?
- skin infections/eruptions
- wound infections
- upper respiratory infections (sinusitis/pharyngitis)
- Pneumonia
- food poisoning/TSS
- septicemia/disseminated infections
staph/strep accounts from the majority for what kind if infections?
suppurative infections
- also abscess formation-> can only spread along tissue planes
- role of phagocytosis/opsonization very important
diseases that interfere with ________ function result in pyogenic infections?
neutrophils
- diabetes
- chronic granulomatous disease
is staph a native flora?
Yes
-ubiquitous (common cause of skin abscesses)
Coagulase positive staph?
Staph. aureus
coagulase negative staph?
Staph. epidermidis
- infects damaged tissue
- contamination of devices, implants-> lead to infection
what are general forms of disease from staph?
- local infections/abscess formation
- bacteremia (sepsis)-> can be to heart valves, kidneys, bones, joints
- toxin-mediated diseases: food poisoning, TSS
what are the virulence factors of Staph?
- coagulase +/-
- cytolytic toxins
- lipases
- penicillinase, plasmid mediated antibiotic resistance
- fibronectin and vitronectin-> bind to host cells
- protein A: binds Fc portion of immunoglobulins
what are toxins from staph?
- enterotoxins
- cytolytic toxins
- exfoliative toxins
- toxic shock syndrome toxin (TSST-1)
Pathogenic factors in S. aureus
- Suppurative disease: impetigo, folliculitis
- Enteritis
- TSS
- Postoperative pneumonia
- staphylococcal scalded skin syndrome
- food poisoning
For staph infections: over growth of NF/UPT leads to?
sinusitis
otitis media
For staph infections: access to sterile areas leads to?
- skin, wound infection
- hematogenous spread from punctures
- bacteremia spread to joints, bone, heart valves. etc
For staph infections: deep infections in immunosuppressed/debilitated leads to?
necrotizing pneumonia, septicemia
types of skin/wound infections?
furuncle, carbuncle, sutures/foreign bodies, impetigo
staph infections are a common cause of ________ infections?
burns, surgical, nosocomial infections
staph infections of UPT are usually caused from?
obstruction with overgrowth of colonizing bacteria
-sinusitis, otitis media, pharyngitis
what are UPT is usually associated with?
- secondary to viral infection
- diabetes
- trauma or irritation
- foreign bodies
- duct obstruction
what are the two toxic mediated diseases with staph?
food poisoning
TSS
what toxin causes food poisoning with staph?
enterotoxin
- short incubation (1-6 hours)
- custards, milk, meats, potato salad
what is TSS from staph?
overgrowth of bacteria with absorption of toxin
- T cell super antigen (non-specific activation)
- fever, diffuse macular rash, shock
- confused with gram negative sepsis
characteristics of bacteremia from staph?
relatively non-threatening
- seeding of damaged tissue from circulation
- acute endocarditis, septic arthritis, osteomyelitis, meningitis
characteristics of bronchopneumonia from staph?
debilitated patients
- nosocomial
- secondary to viral infection, or obstructive illness
- very destructive purulent lesions
characteristics of staph saprophyticus
NF, periurethral and urethral flora
-UTI in young women
characteristics of staph epidermidis
coagulase negative
-only infects inert objects (catheters, artificial tissues)
MRSA
has hospital and community forms
what is MRSA first detected as?
cluster of abscesses or spider bites
community acquired MRSA
mostly skin and soft tissue infections
- 5% invasive (sepsis, bone/joints)
- NOT lethal organism
how do most MRSA infections occur?
cuts, wounds, or abrasions that allow bacteria to enter the skin or mucous membranes
-can cause local necrosis (like a spider bite), and look like a small collection of boils
