Staphylococci and Related Gram Positive Cocci 9/2/15 Flashcards
What are the key characteristics of Staphylococci?
-Gram + cocci -Grape-like clusters ***Catalase positive -Fac anaerobes
What are some important species of Staphylococci?
-S. aureus -S. epidermidis -S. lugdunensis -S. saprophyticus “Achy epidermis, loose skin”
Where are S. aureus typically found?
-Skin and mucous membranes (i.e. anterior nares)
What factors predispose to serious Staphylococcus aureus infection?
- Defects in leukocyte chemotaxis (Down syndrome, DM, or RA)
- Defects in opsonization
- Defects in intracellular killing (leukemia)
- Skin injury (burns, sports)
- Presence of foreign bodies (sutures, IV)
- Infection with other agents (influenza)
- Chronic underlying disease (malignancy)
- Use of antibiotics to which the infecting S. aureus is not susceptible
What are the usual sites of infection for S. aureus?
Skin
Nose
Throat
GI tract
Urethra
Vagina
What are some diseases caused by Staphylococcus aureus?
- Pyoderma: pyogenic skin disease (the baby pic)
- Furuncle (boil): infected hair follicle, filled with pus and dead tissue, painful
- Carbuncle: Abscess larger than a boil, openings draining pus onto the skin, common on nape of neck
- Toxin-mediated infections: Scalded skin syndrome (the babies), TSS, Food poisoning
- Disseminated infections: infection metastasis resulting in: sepsis, pneumonia, osteomyelitis, endocarditis
What are some of the major virulence factors of Staph aureus?
- Components interfering with phagocytosis: Capsules, protein A, PVL, COAGULASE +
- Hemolysins: alpha and beta mostly (others exist)
- Toxins
- Enzymes
- Superantigens: pyrogenicity, superantigenicity, enhance effects of endotoxin, induce polyclonal T cell proliferation
What are some effects of toxins produced by S aureus
- Exfoliatins/epidermolytic toxins: Dissolves muco-polysaccharide matrix of epidermis (scalded skin syndrome)
- Enterotoxins: heat-stable, responsible for Staph food poisoning (quick onset, quick recovery)
What are some examples of pyrogenic toxin superantigens?
- TSST-1 (S. aureus mediated)
- SPE -Streptococcal superantigens
What are the coagulase positive Staphylococci species?
STAPH AUREUS = pathogenic
What species of Staphylococci can be detected via Latex Agglutination?
A coagulase test of Staph aureus
Is Staphylococcus epidermidis coagulase positive or negative?
Negative
What types of infections are associated with Staph epidermidis?
- Infections of indwelling devices
- Infections involving biofilms
What Staphylococcus species is responsible for acute UTI in young women?
Staph saprophyticus
How can one ID Staph saprophyticus?
-Negative coagulase
-Resistance to Novobiocin
Which bacterial strains would be resistant and which would be susceptible to a Novobiocin disc?
R = S. saprophyticus
S = Other Staph and Micrococcus
Which bacterial strains are resistant and which are susceptible to Furozolidone?
R = Micrococcus S= Staphylococcus
Describe characteristics of Staphylococcus lugdunensis “The Lug Bug”.
- Coagulase negative
- Colonizes human inguinal area
-ONLY species that is both PYR and Ornithine positive
-Causes same infections as Staph aureus: meningitis, abscesses, oral infections, osteomyelitis, etc.
List six settings that have been associated with community-acquired MRSA outbreaks
- Sports participants: MPSM
- Correctional facilities
- Military recruits
- Daycare and other institutions
- Newborn nurseries and other healthcare settings
- MSM
List 5 severe syndromes in which MRSA should be considered in the differential diagnosis.
- Severe diseases compatible with S. aureus infection:
1. Sepsis
2. Osteomyelitis
3. Necrotizing pneumonia
4. Septic arthritis
5. Necrotizing fasciitis
Describe effective infection prevention measures to control MRSA infections in the hospital.
- Careful hand hygiene for all pt interactions
- Standard precautions: gowns, gloves, masks
- Effective cleaning of pt environment
- Clean shared/dedicated equipment: Stets, remotes, BP cuffs, etc.
- Appropriate use of antibiotics
- Active surveillance
