Transcript Streptococcus pneumoniae and Staphylococci

Staphylococcus and Related
Organisms
미생물학교실
권 형 주
STAPHYLOCOCCI
• Gram positive
• Facultative anaerobes
(Capable of aerobic and anaerobic growth)
• Grape like-clusters
• Catalase positive
• Major components
of normal flora
- skin
- Nose : mucose membrane
Gram stain of Staphylococcus aureus
1. 병원성 Staphylococcus의 특징을 이용 하여 다른 세균과 구별
* 병원성: 혈액응고효소 생산, 만니톨 분해, 젤라틴 액화, 황금색 집락, 간혹 용혈성
식중독,화농성
염증,포도구균성
피부박탈증후군,독소형
쇼크증후군
Micrococcus : 그람양성구균으로 불규칙한 배열을 하고있으며, 임상적으로 큰 의의는 없어
균속만 동정
: Catalase +,
Coagulase -
Staphylococcus
Catalase시험 : catalase 생산세균을 동정.(2H2O2---catalase--- 2H2O + O2 )
양성-Micrococcus, Staphylococcus. Bacillus, 장내세균.
음성-Streptococcus, 혐기성균.
색소 생산시험 : 세균이 배지에 집락을 형성할때 색소를 생산
병원성균일 경우 황금색 색소 생성
S. aureus -황색 S. epidermidis -(회)백색~레몬색 S. saprophyticus -백색
Coagulase생산시험 : 강한병원성인 Staphylococcus aureus와 S. intermedius및 S.
saprophyicus의 일부가 생산하는 효소이며, 토끼나 사람의 혈장을 배양균과함께 반응시키면 혈장
의 응고가 일어남.
* free coagulase-혈장중의 prothrombin을 활성화함으로써 응고
* bound coagulase(균에 결합)-fibrinogen을 직접 fibrin으로 바꿈
Streptococcus
용혈성 관찰 : 세균의 적혈구 파괴를 확인하기위해 혈액한천배지를 이용한다.
배양후 집락주위에 형성된 용혈환에 따라 a, b, g -용혈로 구분
a-용혈 : hemoglobin을 methemoglobin으로 변화시켜 녹색의 환을 형성
b-용혈 : 적혈구가 완전히 파괴되어 투명한 용혈환 형성
g-용혈 : 비용혈성
Bacitracin감수성 검사 : bacitracin에 감수성이 있는 균은 13mm이상 저지대 형성
BOX 21-1. Important Staphylococci
Organism
Historical Derivation
Staphylococcus
staphylé, bunch of grapes; coccus, grain or berry (grapelike coccus)
S. aureus
aureus, golden (golden or yellow)
S. epidermidis
epidermidis, outer skin (of the epidermis or outer skin)
S. lugdunensis
Lugdunum, Latin name for Lyon, France, where the organism was first isolated
S. saprophyticus
sapros, putrid; phyton, plant (saprophytic or growing on dead tissues)
Table 21-1. Staphylococcus Species and Their Diseases
Organism
Diseases
Staphylococcus
aureus
Toxin mediated (food poisoning, scalded skin syndrome, toxic shock syndrome);
cutaneous (carbuncles, folliculitis, furuncles, impetigo, wound infections); other
(bacteremia, empyema, endocarditis, osteomyelitis, pneumonia, septic arthritis)
Staphylococcus
epidermidis
Bacteremia; endocarditis; surgical wounds; urinary tract infections; opportunistic
infections of catheters, shunts, prosthetic devices, and peritoneal dialysates
Staphylococcus
saprophyticus
Urinary tract infections; opportunistic infections
Staphylococcus
lugdunensis
Arthritis, bacteremia, endocarditis, opportunistic infections, and urinary tract infections
Staphylococcus
haemolyticus
Bacteremia, bone and joint infections, endocarditis, urinary tract infections, wound
infections, and opportunistic infections
Physiology and Structure
O CAPSULE AND SLIME LAYER
- polysaccharide capsule - inhibiting phagocytosis of
the organisms by polymorphonuclear leukocytes
(PMN).
- A loose-bound, water-soluble film (slime layer)
: monosaccharides, proteins, and small peptides
: Bind the bacteria to tissues and foreign bodies
: important for the survival of relatively avirulent
coagulase-negative staphylococci.
O PEPTIDOGLYCAN
- layers of glycan chains built with 10 to 12 alternating subunits of N-acetylmuramic
acid and N-acetylglucosamine
- endotoxin-like activity, stimulating the production of endogenous pyrogens,
activation of complement, production of interleukin-1 from monocytes, and
aggregation of PMN
O Synthesis of cell wall peptidoglycan
- Transpeptidation : cross-linking peptidoglycan
- Penicillin-binding proteins (PBPs)
: Targets of penicillin and beta-lactam antibiotics
- Methicillin-resistant S. aureus (MRSA)
: mecA gene
(Staphylococcal cassette chromosome mec(SCCmec)
- novel penicillin-binding protein (PBP2)
- not bound by penicillin, retain enzymatic activity
- Hospital, community infections
- SCCmec type IV : most common type
o Methicillin-resistant Staphylococcus aureus (MRSA)
- a bacterium responsible for difficult-to-treat infections in humans.
- multiply-resistant Staphylococcus aureus
or oxacillin-resistant Staphylococcus aureus (ORSA).
- Community-Associated MRSA (CA-MRSA)
or Hospital-Associated MRSA (HA-MRSA)
- Survive treatment with beta-lactam antibiotics,
(penicillin, methicillin, and cephalosporins)
Electron micrograph of MRSA
O TEICHOIC ACIDS
- Ribitol teichoic acid with N-acetylglucosamine residues ("polysaccharide A") is present in
S. aureus- Glycerol teichoic acid with glucosyl residues ("polysaccharide B") is present in
S. epidermidis.
- Attachment of staphylococci to mucosal surfaces through their specific binding to fibronectin.
- poor immunogens, a specific antibody response is stimulated
O PROTEIN A
- surface of most S. aureus strains
- a unique affinity for binding to the Fc receptor of immunoglobulin (Ig)G1, IgG2, and IgG4
: prevents antibody-mediated immune clearance of the organism.
- Extracellular protein A can also bind antibodies
: consumption of the complement
: a specific identification test for S. aureus.
O COAGULASE AND
OTHER SURFACE ADHESIN PROTEINS
- clumping factor (bound coagulase) : outer surface of most strains of S. aureus
: binds fibrinogen and converts it to insoluble fibrin,
causing the staphylococci to clump or aggregate.
- Other surface proteins : MSCRAMM (microbial surface components recognizing adhesive
matrix molecules) proteins
: adherence to host matrix proteins, which in turn bind to host
tissues (e.g., fibronectin, fibrinogen, elastin, collagen).
Pathogenesis and Immunity
- surface proteins : adherence of the bacteria to host tissues
- extracellular proteins, such as specific toxins and hydrolytic enzymes.
- expression of the exoprotein genes is controlled primarily by a global regulator, agr,
which in turn is controlled by environmental factors, cell density, and energy availability.
STAPHYLOCOCCAL TOXINS
O Cytotoxin
1) Alpha (α) toxin
: bacterial chromosome and a plasmid
: disrupts the smooth muscle in blood vessels and is toxic to many types of cells, including
erythrocytes, leukocytes, hepatocytes, and platelets
: integrated in the hydrophobic regions of host cell membrane, leading to formation of
1- to 2-nm pores.
- rapid efflux of K+ and influx of Na+, Ca2+, and other small molecules leads to osmotic
swelling and cell lysis.
2) Beta (β) toxin-sphingomyelinase C
: toxic to a variety of cells, including erythrocytes, fibroblasts, leukocytes, and macrophages
: hydrolysis of membrane phospholipids in susceptible cells
3) Delta (δ) toxin
:a wide spectrum of cytolytic activity, affecting erythrocytes, many other mammalian cells, and
intracellular membrane structures - nonspecific membrane toxicity : acts as a surfactant
disrupting cellular membranes by means of a detergent-like action.
O Cytotoxin
4) Gamma (γ) toxin (made by almost all S. aureus strains) and P-V leukocidin
(made by <5% of S. aureus strains)
: Cell lysis by these toxins is mediated by pore formation with subsequent increased
permeability to cations and osmotic instability.
o Panton-Valentine leukocidin (PVL)
- cytotoxin—one of the pore forming toxins.
- increased virulence of certain strains (isolates) of Staphylococcus aureus.
: Methicillin-resistant Staphylococcus aureus (MRSA)
- The cause of necrotic lesions involving the skin or mucosa,
including necrotic hemorrhagic pneumonia.
- The genetic material of a bacteriophage which infects Staphylococcus aureus, making it
more virulent.
Mechanism of action
- secrete lethal factors
:secrete two proteins—toxins designated LukS-PV and LukF-PV, 33 and 34 kDa in size.
- induces pores in the membranes of cells
: assembling in the membrane of host defense cells, particularly white blood cells,
monocytes and macrophages. The subunits fit together and form a ring with a central
pore through which cell contents leak and which acts as a superantigen.
O Exfoliative Toxins (표피탈락독소)
- Staphylococcal scalded skin syndrome (SSSS, 포도알균 열상피부증후군)
: exfoliative dermatitis 원인
: serine proteases
- splitting of the intercellular bridges (desmosomes) in the stratum granulosum epidermis
: SSSS is seen mostly in young children and only rarely in older children and adults
- ETA (heat stable, chromosome), ETB (heat labile, plasmid)
O Enterotoxins(장독소)
- stable to heating at 100°C for 30 minutes
- resistant to hydrolysis by gastric and jejunal enzymes.
- precise mechanism of toxin activity is not understood
- superantigen ; releases inflammatory mediators
- staphylococcal food poisoning.
O Toxic Shock Syndrome Toxin-1 (독소충격증후군 유발독소-1)
- pyrogenic exotoxin C and enterotoxin F
- superantigen that stimulates release of cytokines, producing leakage of
endothelial cells at low concentrations and a cytotoxic effect to the cells at high concentrations.
- ability of TSST-1 to penetrate mucosal barriers
- Death in patients with TSS is cause by hypovolemic shock(저혈액량쇼크)- multiorgan failure.
O Superantigens
- Exfoliative toxin A
- Enterotoxin
- TST-1
STAPHYLOCOCCAL ENZYMES
O Coagulase
- S. aureus strains possess two forms of coagulase: bound and free.
- Bound : convert fibrinogen to insoluble fibrin and cause the staphylococci to clump.
- Cell-free coagulase : formation of coagulase-reacting factor to form staphylothrombin, a thrombinlike factor.
: conversion of fibrinogen to insoluble fibrin : protecting the organisms from phagocytosis
O Catalase
- catalyzes the conversion of hydrogen peroxide to water and oxygen
O Hyaluronidase
Hyaluronidase hydrolyzes hyaluronic acids, the acidic mucopolysaccharides present in the cellular matrix of
connective tissue - facilitates the spread of S. aureus in tissues.
O Fibrinolysin
Fibrinolysin, also called staphylokinase : dissolve fibrin clots.
O Lipases
- hydrolyze lipids, an essential function to ensure the survival of staphylococci in the sebaceous areas of the
body. to invade cutaneous and subcutaneous tissues and for superficial skin infections
O Nuclease
A thermostable nuclease - role of this enzyme in the pathogenesis of infection is unknown.
O Penicillinase
- More than 90% of staphylococcal isolates were susceptible to penicillin in 1941
- Resistance to penicillin quickly developed - produce penicillinase (β-lactamase) - transmissible plasmids.
Epidemiology
- Normal flora on human skin and mucosal surfaces – 피부, 구인두, 위장관, 비뇨생식계
- Organisms can survive on dry surfaces for long periods (owing to thickened peptidoglycan
layer and absence of outer membrane-characteristics of all gram-positive bacteria)
- Person-to-person spread through direct contact or exposure to contaminated fomites (e.g.,
bed linens, clothing)
- Risk factors include presence of a foreign body (e.g., splinter, suture, prosthesis, catheter),
previous surgical procedure, and use of antibiotics that suppress the normal microbial flora
- Patients at risk for specific diseases include infants (scalded skin syndrome), young
children with poor personal hygiene (impetigo and other cutaneous infections), menstruating
women (toxic shock syndrome), patients with intravascular catheters (bacteremia and
endocarditis) or shunts (meningitis), and patients with compromised pulmonary function or
an antecedent viral respiratory infection (pneumonia) – 신생아간호에 중요
- Infections found worldwide and generally with no seasonal prevalence (except that food
poisoning is more common in summer and during late-year holidays)
Community-associated MRSA (CA-MRSA)
항생제 내성과 치사율
Clinical Diseases
Staphylococcus aureus
One of commonest opportunistic
infections - hospital and community:
• Toxin activity
: SSSS
: Staphylococcal food poisoning
: Toxic shock syndrome
• Proliferation
(abscess formation, tissue destruction)
: cutaneous infections,
endocarditis,
pneumonia,
empyema,
osteomyelitis,
septic arthritis
O Staphylococcal Scalded Skin Syndrome
(포도알균 열상피부증후군, 표피탈락증후군)
- In 1878, Gottfried Ritter von Rittershain : bullous exfoliative dermatitis
( 297 infants younger than 1-month old)
- Ritter's disease or SSSS : perioral erythema (redness and inflammation
around the mouth)
- Slight pressure displaces the skin (a positive Nikolsky's sign)
- -> large bullae or cutaneous blisters desquamation of the epithelium
- bacterial toxin (Exfoliative Toxins) , protective antibodies appear
- 전신성 표피탈락성 피부염이 가장 심각
- Nikolsky's sign
: A skin condition in which the top layers of the skin slip away from the lower
layers when slightly rubbed
: positive or negative.
- A positive : loose skin that slips free from the underlying layers when rubbed.
: The area beneath is pink and moist and may be very tender.
: by twisting a pencil eraser against your skin. If positive, a blister
will form in the area, usually within minutes.
- Allergic reaction (Toxic epidermal necrolysis)
- Autoimmune condition (Pemphigus vulgaris)
- Bacterial infection ( Scalded skin syndrome)
O Bullous impetigo (수포성농가진)
- 표피탈가성 환부가 있는 국소적 질환
- specific strains of toxin-producing S. aureus
(e.g., phage type 71)
- formation of superficial skin blisters.
- Nikolsky's sign is not present. The disease occurs
primarily in infants and young children and is highly
communicable.
Staphylococcal Food poisoning
•
•
•
•
•
•
•
•
not an infection
food contaminated by humans
– growth of bacteria
– production of enterotoxin
– enterotoxins are heat-stable
onset and recovery both occur within few hours
Vomiting
nausea
diarrhea
abdominal pain
Enterocolitis –watery diarrhea, abdominal cramps, fever
Toxic shock syndrome (독소충격증후군)
•
•
•
•
•
•
•
Fever
Hypotension
rash
desquamation
vomiting
diarrhea
Toxic shock toxin
- Dissemination
• Organism
– no dissemination
- ability of TSST-1 to penetrate mucosal barriers
Death in patients with TSS is cause by hypovolemic shock(저혈액량쇼크)
- multiorgan failure.
Cutaneous Infections
Localized, pyogenic staphylococcal infections
: impetigo (농가진), folliculitis(모낭염), furuncles(뽀로지), and
carbuncles(옹종, 큰종기). .
Impetigo : superficial infection that mostly affects young children,
-a small macule (flattened red spot)
- a pus-filled vesicle (pustule) on an erythematous base develops.
- Crusting occurs after the pustule ruptures.
Folliculitis : pyogenic infection in the hair follicles 
follicle is raised and reddened- small collection of pus
beneath the epidermal surface.
- Furuncles (boils) : extension of folliculitis, are large,
painful, raised nodules
Carbuncles : furuncles coalesce and extend to the
deeper subcutaneous tissue
- chills and fevers, indicating the systemic spread of
staphylococci via bacteremia to other tissues.
Staphylococcal wound infections : in patients after
a surgical procedure or after trauma
- edema, erythema, pain, and an accumulation of purulent
material.
- the foreign matter removed, and the purulence drained.
Figure 21-7 Staphylococcus aureus carbuncle.
This carbuncle developed on the buttock over
a 7- to 10-day period and required surgical
drainage plus antibiotic therapy. (From Cohen
J, Powderly WG: Infectious diseases, ed 2, St
Louis, 2004, Mosby.)
Bacteremia (균혈증) and Endocarditis (심내막염)
S. Aureus - bacteremia
- infection of the lungs, urinary tract, or gastrointestinal tract
-use of a contaminated intravascular catheter.
Acute endocarditis - S. aureus : a serious disease, mortality rate ~50%.
-nonspecific influenza-like symptoms, disruption of cardiac output
- 외과적 수술 후 또는 정맥내 삽관후 발생하는 원내 감염
Pneumonia (폐렴) and Empyema (농흉)
Aspiration pneumonia (흡식폐렴) : young, the elderly, and patients with cystic fibrosis,
influenza, chronic obstructive pulmonary disease, and bronchiectasis
Hematogenous pneumonia is common for patients with bacteremia or endocarditis
necrotizing pneumonia with massive hemoptysis, septic shock, and a high mortality
rate has been observed in recent years.
Empyema occurs in 10% of patients with pneumonia,
- drainage of the purulent material is sometimes difficult.
Osteomyelitis (골수염) : Destruction of bones, particularly the metaphyseal area of
long bones
Septic arthritis (화농성, 세균성 관절염): Painful erythematous joint with collection
of purulent material in the joint space
Staphylococcus epidermidis and
other coagulase-negative Staphylococci
•
•
•
•
•
•
•
Staphylococcus epidermidis
Staphylococcus lugdunensis
Coagulase-negative
Catheter and shunt infections
Prosthetic joint infections
Urinary tract infections
diarrhea
Identification (Staphylococcus aureus)
• b hemolytic
– sheep blood agar
– yellow pigmented (aureus)
• mannitol fermentation
• coagulase-positive
Staphylococcus epidermidis
• major component, skin flora
• opportunistic infection
- less common than S.aureus
• nosomial infections
- shunts, catheters
Identification
• Non-hemolytic
– sheep blood agar
– Non-pigmented
• Does not ferment mannitol
• Coagulase negative
• artificial heart valves/joints
Staphylococcus saprophyticus
• urinary tract infections
• coagulase-negative
– not usually differentiated from S. epidermidis
Antibiotic therapy
• Resistance to penicillin
– penicillinase
 b- lactam antibiotics (including methicillin)
– often ineffective
– modified penicillin binding proteins
• Vancomycin
• current drug of choice
• resistance has been observed
Antibodies (monoclonal)
- MSCRAMM (microbial surface components recognizing
adhesive matrix molecules) proteins : clumping factor
Summary Figure (Identification Scheme)
Note: S. viridans is Is alpha
hemolytic and negative for
all the tests below
below
GRAM POSITIVE COCCI
Catalase
-
+
Staphylococcus(Clusters)
Streptococcus(pairs & chains)
Coagulase
+
S. aureus

hemolytic
mannitol
yellow
-
S. epidermidis
nonhemolytic (usually)
mannitol
white
Hemolysis
BETA: Bacitracin
S.pyogenes (group A)
+
CAMP/ Hippurate
+
S. agalactiae (group B)
ALPHA: Optochin /Bile Solubility
+
S. pneumoniae
GAMMA: Bile Esculin
+
6.5% NaCl
Enterococcus
+
Bile Esculin
+
6.5% NaCl
Group D*
Non-Enterococcus
Group D*
-
(*can also be alpha hemolytic)
Enterococcus
Groupable streptococci
• A, B and D
– most important
• C, G, F
– rare
Group D streptococcus
• Growth on bile esculin agar
– black precipitate
• 6.5% saline, 40% bile salts
• grow
– enterococci
• no growth
– non-enterococci
Enterococci
•
•
•
•
•
distantly related to other streptococci
genus Enterococcus
catalase-negative, gram-positive cocci
gut flora
– urinary tract infection
• fecal contamination
– opportunistic infections
• particularly endocarditis
most common E. faecalis
BOX 21-1. Important Enterococci
Organism
Historical Derivation
Enterococcus
enteron, intestine; coccus,
berry (intestinal coccus)
E. faecalis
faecalis, relating to feces
E. faecium
faecium, of feces
E. gallinarum
gallinarum, of hens
(original source was
intestines of domestic fowl)
E. casseliflavus
casseli, Kassel's; flavus,
yellow (Kassel's yellow)
Table 23-3. Enterococcal Virulence Factors
Virulence Factor
Surface Adhesins
Aggregation substance
Biologic Effect
Hairlike protein embedded in cytoplasmic membrane that facilitates plasmid
exchange and binding to epithelial cells
Enterococcal surface protein Collagen-binding adhesin present in E. faecalis
Carbohydrate adhesins
Present in individual bacterium in multiple types; mediate binding to host cells
Secreted Factors
Cytolysin
Pheromone
Protein bacteriocin that inhibits growth of gram-positive bacteria (facilitates
colonization); induces local tissue damage
Chemoattractant for neutrophils that may regulate inflammatory reaction
Gelatinase
Hydrolyzes gelatin, collagen, hemoglobin, and other small peptides
Antibiotic Resistance
Multiple plasmid and
chromosome genes
Resistant to aminoglycosides, β-lactams, and vancomycin
BOX 243-2. Summary of Enterococci
•Physiology and Structure
Gram-positive cocci arranged in pairs and short chains (similar to Streptococcus pneumoniae)
Facultative anaerobe
Cell wall with group-specific antigen (group D glycerol teichoic acid)
•Virulence Factors Refer to Table 23-3
•Epidemiology
•Colonizes the gastrointestinal tracts of humans and animals
•Cell wall structure typical of gram-positive bacteria, which makes it able to survive on environmental surfaces for
prolonged periods
•Most infections from patient's bacterial flora; some caused by patient-to-patient spread
•Patients at increased risk include those hospitalized for prolonged periods and treated with broad-spectrum
antibiotics (particularly cephalosporins, to which enterococci are naturally resistant)
•Diseases
• Urinary tract infections
•Wound infections (particularly intraabdominal and usually polymicrobic)
•Bacteremia and endocarditis
•Diagnosis
•Grows readily on common, nonselective media. Differentiated from related organisms by simple tests
(catalase negative, PYR positive, resistant to bile and optochin)
•Treatment, Prevention, and Control
•Therapy for serious infections requires combination of aminoglycosides with a cell wall-active antibiotic (penicillin,
ampicillin, or vancomycin); newer agents include linezolid, quinupristin/dalfopristin, and selected fluoroquinolones
•Antibiotic resistance is becoming increasingly common, and infections with many isolates (particularly E. faecium)
are not treatable with any antibiotics
•Prevention and control of infections require careful restriction of antibiotic use and implementation of appropriate
infection-control practices