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TRANSCRIPT
Outline
Staphylococcus
Streptococcus
Enterococcus
Neisseria and Branhamella
Classification 、 Clinical Significance 、 Microbial
Characters 、 Microbial diagnostics
Staphylococcus Gram-positive cocci that occur singly and in pairs, tetrads, and irregular grape-like clusters
Common description Widespread in nature
Mainly found living on the skin, skin glands
and mucous membranes of mammals and
birds
Also found in the environment
Sometimes found in the mouth, blood, and
intestinal, and upper respiratory tracts
ClassificationCurrently composed of 32 species and 15 subspecies
Important StaphylococcusS. aureus
S. epidermidis
S. capitis
S. hominis
S. saprophyticus
CoagulaseCoagulase positive Staphylococci
Coagulase negative Staphylococci
Clinical significantS. aureus Important pathogen
Enzymes:catalase, coagulase,staphylokinase, et al Toxin: exotoxin, enterotoxin, et al
Community- and hospital acquired infection Acute pyogenic infection
Common infection ： boil 、 cellulitis 、 postoperative wound infections
Serious infection ： bacteremia 、 pneumonia 、 osteomyelitis 、 meningitis ， acute endocarditis, et al
BoilsInfection of hair follicles by S. aureusImpetigo
School sores; common mostly among children
Abscess
Osteomyelitis
Food poisoning: enterotoxinToxic shock syndrome(TSS) ：
toxic shock syndrome toxin 1(TSST-1)
Scaled skin syndrome
Coagulase negative staphylococcus, CONS Normal flora of human Causing nosocomial infections S. epidermidis
Prosthetic valve endocarditis
Intravascular catheter-related infection
Peritoneal dialysis-related infection Prosthetic joint infection
Why The increase in the use of prosthetic and indwelling devices Immunocompromised patients in hospitals
S. saprophyticus Urinary tract infection
Microbial CharactersGram positive coccus arranged ： single 、 pairs 、 tetrads, short chains and grape-like
clusters
Facultatively anaerobe
Colonial appearance Color, smooth, entire, heamolytic characters
Chemical reaction: active metabolism, fermenting carbohydrates
Catalase ： +(differentiates from streptococcus)
Coagulase: +/-
Microbial diagnostics
procedure
specimen
Smear and stain culture direct examination
colony
Smear and stain biochemical serology antibiotic
identification identification susceptibility
Isolated cultureBroth culture
Specimen collection Routine method
Avoid normal flora contamination Surface swab, pus, blood, spinal fluid,
sputum, et al
Specimen direct diagnostics Smear and Gram stain report
Culture and identification Media selection
Blood agar Broth Selective agar
Colonial appearance
S. epidermidis Small, smooth, entire, sli
ghtly raised, white, nonheamolysis
S. aureus Large,smooth,entire, sligh
tly raised, pigment from cream-yellow to orange, β heamolysis
Catalase
Staphylococcus produce catalase
Convert hydrogen peroxide into water and oxygen
(formation of bubbles)
Coagulase productionAbility to clot plasma
Rapid and economical test
Dehydrated rabbit plasma containing EDTA
Slide test Bound coagulase ＋ plasma clot(10s)
+: S. aureus and S. intermedius
Tube test Free coagulase
Other: latex agglutination test
Heat-stable nuclease
+ ： S. aureus, S. schleiferi , S. intermedius and S. carnosus
Heat-stable staphylococcal nuclease (thermonuclease[TNase])
Method: metachromatic agar diffusion procedure and DNA-t
oluidine blue agar
Phosphatase activity
+ ： S. epidermidis, S. aureus, S. schleiferi and S. intermedius
Pyrrolidonyl arylamidase activity (PYR test)
principle: bacteria
L-pyrrolidonyl-β-naphthylamide β-naphthylamine
＋
N,N-dimethylaminocinnamaldehyde
red color
OtherOrnithine decarboxylase activity
β-galactosidase activity
Novobiocin resistance
Antibiotic susceptibilities
A class （ routine antibiotic ）oxacillin,penicillin
B class （ use mainly antibiotic in clinical ）azithromycin,clindamycin,TMP/SMZ,vacomycin
C class （ resistant to A class ）ciprofloxacin,gentamicin,chloramphenicol
U class （ bacteria from urine ）norfloxacin, nitrofurantoin
Methecillin resistant Staphylococcus, MRS
MRSA 、 MRSE 、 MRSCO
Main pathogen in nosocomial infection
Resistant to oxacillin
resistant ： high resistant
heteroresistant ： borderline
Two subpopulations coexist: one susceptible and the other resist
ant
MRS
Detection methods
The presence of NaCl （ 2 to 4% ）cooler temperatures (30 to 35 )℃prolonged incubation(up to 48h)
mecA gene probe
PCR
MRS
Resistant mechanism chromosome mecA gene mediated, produce low affinity
penicillin binding protein(PBP), PBP2’ or PBP2a
characters
Multidrug-resistant
Resistant to all β － lactams
Clinical use
Vacomycin, teicoplanin, ciprofloxin, TMP-SMZ, et al
Summary
Gram stain ＋ colonial appearance
Catalase +
+ S. aureus
_ coagulase CONS
Attention: MRS
