MICRO: CH 14 Staphylococcus, Micrococcus and similar organisms
Micrococcus luteus produces a yellow pigment and is susceptible to
bacitracin
extracellular enzymes that inactivates several classes of antibiotics
beta lactamase
When should the tech should look for small colony variants (SVCs)
in persistent;, recurring infections;. if there are cocci in the gram stain;, but no growth on plates;. in presence of 2 colony types in positive blood cultures;. or in vitro activity shows susceptibility;. but treatment fails
Staph epidermidis is associated with
indwelling devices and prosthetics;. such as pertoneal dialysis catheters and valve endocarditis
Some strains of MRSA have become resistant to vancomycin; two new antibiotics that may be useful are
linezolid and daptomycin
Staph epidermidis; & other coagulase negative staph; have been dismissed as contamination; but may be
pathogenic
Oxacillin can destroy extracellular staph organisms but cannot
penetrate the host cell.
Daptomycin is the only negatively charged
antibiotic in use
Staph saprophyticus is differentiated from other nonhemolytic;, Cons (coag-neg staph) by its
resistance to novobiocin
Mannitol salt agar contains
10% salt mannitol; and pheno red as an indicator
Methicillin resistant Staph aureus is a multidrug resistant strain called
MRSA; which can only be treated with vancomycin
Micrococcus has two species
Micrococcus luteus and Micrococcus lylae; which are harmless saprophytes
Confirmation of oxacillin resistance in Staph aureus is done by testing for the presence of
Penicillin binding protein
Staph produce conlonies surrounded by a yellow halo. Species include
Staph aureus;. S. saprophyticus;. S. lugdunesis;. S. epidermidis;. S. haemolyticus;. and S. schleiferi
Endocarditis and soft tissue infections are associated with
Staph lugdumensis and Staph haemolyticus
In the family Micrococcaceae are the genera
Staphylococcus and Micrococcus
Staphs intrinsic resistance to beta lactam antibiotics is due to
a penicillin binding protein called PBP
Staph epidermidis produces exopolysaccharide slime;. which allows
adherence to the indwelling devices or prosthetics
test that detects cytochrome oxidase
catalase test
Staph aureus is differentiated from other species with a negative P Y R; and its production of
coagulase ; which is positive for the Voges Proskauer test;
Micrococci and staph contain
cytochrome enzymes; which is detected by catalase
Conditions that predispose a person to staph infections include
diabetes;. IV;. prosthetics;. chemotaxis disease; such as Chediak-Higashi;, neutrophil defects;. and complement defects
Toxic shock syndrome is a life threatening infection involving several organ systems that presents with
high temp;. diarrhea;. high blood pressure;. rash with desquamation;. and renal failure
Staph aureus is the most virulent species;. and Most staph secrete
enzymes and cytotoxins
Enzymes and cytotoxins secreted by staph include one of the 4
hemolysins;. nucleases;. proteases;. lipases;. hyaluronidase;. and collagenase
Chlorehexidine showers may be used to reduce Staph aureus colonization in
nasal pathways;. in situations of nasal carriers
Characteristics of staph
nonmotile; non spore forming; facultative anaerobes; and resistant to bacitracin.
Enzymes & cytotoxins secreted by staph convert host tissue into
nutrients required for growth
Staphylococcus and Micrococcus cocci are gram
positive
sloughing of epidermis usually seen in neonates
scalded skin syndrome
Staph lugdunesis and Staph schleifer are Cons isolated from colonized
shunts; prosthetic devices and catheters
Saprophytes inhabit
skin; mucosa; and oropharynx
The most common cause of food poisoning
staph aureus enterotoxin contamination
Some strains produce exoproteins; including TSS-1; which causes
toxic shock syndrome
Staph saprophyticus is a true
urinary tract pathogen
Small colony variants (SCVs) can evade destruction & proliferate; by hiding
within the host cell
Are staph able to grow in the presence of salt
yes.; This characteristic is used to isolate staphylcocci from clinical material.
Staph saprophyticus cause upper and lower UTI in
young; sexually active females