Post on 25-Mar-2022
Outline
• 5 pathogenic cocci/ Pyogenic cocci – G + : Staphylococcus
S.aureus Streptococcus
S.pyogenes, S.pneumoniae – G : Neisseria
N.meningitidis, N.gonorrhea
þ Biological characteristics; þ Pathogenicity;
Staphylococcus
• Primary reservoir human carriers nasopharynx, throat, skin
• >30 species main bacteria in the nosocomial infection S.aureus: the most virulent species. S.epidermidis: opportunistic pathogen. S.saprophyticus: rarely cause human diseases.
Biological characteristics
• Cultivation • Requirement: Low
grow on basic media facultative anaerobes 37 (2838) pH: 7.4 710% NaCl
Growth properties liposoluble pigments complete/clear hemolysis (βhemolysis) (S.aureus)
Biological characteristics S.aureus
• Biochemical reactions
Biological characteristics
Catalase test “+” Staphylococci: “+” Streptococci: “”
Mannitol Fermentation “+” S. aureus: “+”; S.epidermidis & S.saprophyticus: “”;
– Carbohydrate antigens: capsules & teichoic acid
– Protein antigens:
• Antigenic composition
Biological characteristics
• Staphylococcal protein A (SPA) • Characteristics:
nonspecifically bind to the Fc fragment of IgG
S. aureus
• Function: F a. antiphagocytosis; F b. damage platelet; F c. induce hypersensitivity and inflammation;
Biological characteristics
SPA(staphylococcal protein A)
Bacteria Bacteria
Fc Fc receptor receptor
Phagocyte Phagocyte
IgG IgG
Fab Fc
SPA SPA
• Function: F a. antiphagocytosis; F b. damage platelet; F c. induce hypersensitivity and inflammation; F d. SPAcoated S.aureus is used as reagent
(Ab carriers) of coagglutination test to identify species and types of bacteria.
Biological characteristics
Classification
• Based on the pigments and chemical reactions
Properties S. aureus S. epidermidis S. sarprophyticus
Pigment Golden yellow White Citrine Coagulase + - - Mannitol + - -
Thermostable nuclease + - -
αhemolysin + - - SPA + - -
Pathogenicity strong Weak
Classification
• Based on coagulase § Coagulase” +”: S. aureus § Coagulase” ”: e.g., S. epidermidis & S. saprophyticus
• Phage typing is of epidemiological value S. aureus: 3 phage groups, 26 phage types. § group 1: TSST1producing strains § group 2: exfoliative toxinproducing strains § group 3: enterotoxinproducing strains
Resistance to environment
• Resistance: • Drying
• Heat (survive at 80 30 min); • high concentration of salt (1015% NaCl)
• Sensitivity: • basic dyes (e.g., crystal violet)
• several antibiotics (penicillin, vancomycin) MRSA (methicillin resistant S.aureus)
Pathogenicity (S.aureus)
• Virulence factors ØInvasiveness • Surface structure
SPA, capsule/slime layer • Invasive Enzymes
ØToxinexotoxins • Hemolysins • Leukocidin • Staphylococcal enterotoxin • TSST1 • Exfoliative toxin Coagulase
Enzyme
• Coagulase: • An enzyme that converts fibrinogen in citrated human or rabbit
plasma into fibrin causing the coagulation of blood. • Roles:
inhibit the phagocytosis and function of bactericidal substances in human body by coating bacteria with fibrin
• Classification: Free coagulase plasma clotting tube coagulase test Bound coagulase agglutination of bacteria slide
coagulase test
Pathogenicity (S.aureus)
• Virulence factors Ø Invasiveness • Surface structure
SPA, capsules, slime layer
• Invasive Enzyme
ØToxinexotoxin • Hemolysins/Staphylolysin • Leukocidin • Staphylococcal enterotoxin • TSST1 • Exfoliative toxin/
Epidermolytic toxin
Coagulase
Hemolysins/Staphylolysins Five kinds: αLysin (main pathogenic substance)
βLysin γLysin δLysin εLysin
Roles: • damage host cell membrane → permeability↑; • Have cytotoxic effects on phagocytes and tissue cells;
Pathogenicity (S.aureus)
• Virulence factors Ø Invasiveness • Surface structure
SPA, capsules, slime layer
• Invasive Enzyme
ØToxinexotoxin • Hemolysins/Staphylolysin • Leukocidin • Staphylococcal enterotoxin • TSST1 • Exfoliative toxin/
Epidermolytic toxin
Coagulase
Staphylococcal enterotoxin
• ~1/2 strains of S.aureus • Heat stable protein (100, 30 min) • Resistant to proteolytic enzymes of GI tract
• Role: stimulate vomitingcontrol center of CNS and cause a food poisoning characterized by projectile vomiting.
Toxic shock syndrome toxin1(TSST1)
• Role: • Induce fever, shock, hypotension, multiorgans failure; • enhance the host susceptibility to endotoxin • Cause TSS (Toxic shock syndrome)
Exfoliative toxin
Epidermolytic toxin
• Role: blister of skin SSSS
SSSS: staphylococcal scalded skin syndrome
Pathogenicity
• Disease Ø Invasive infection/pyogenic infection • local infection: folliculitis; boil; carbuncle; impetigo, etc.
(Lesion is limited in local area) • organ infection: pneumonia; meningitis, etc.
• Systemic infection: Septicemia; pyemia
Pathogenicity
ØToxinassociated diseases • Food poisoning (enterotoxin) • TSS (TSST1)
– Sudden high fever, shock, kidney failure, and red skin rash, etc. • SSSS (Exfoliative toxin) (staphylococcal scalded skin
syndrome) • Staphylococcal enterocolitis dysbacteriosis
most often occurs in infants and young children.
low mortality rate.
skin blister →denudation (like scald)
Staphylococcal scalded skin syndrome (SSSS)
Diseases caused by coagulase staphylococci
• Diseases: – S.epidermidis
• urinary tract infection (UTI) • Bacterial endocarditis • Septicemia • Wound infection
– S.saprophyticus • communityacquired UTI
pathogenic cocci
– G + cocci: Staphylococcus S. aureus
Streptococcus S. pyogenes S. pneumoniae
– G cocci: Neisseria N. meningitidis N. gonorrhea
Section 2 Streptococcus
widely exist:
water, air, feces, human nasopharynx.
diseases:
①pyogenic infection;
②scarlet fever;
③streptococcal hypersensitive disease;
④rheumatic fever;
Biological characteristics
• Morphology & cultivation properties • G + , arranged in chains,
no special structure • Nutrient requirement: high
Fastidious (“flesheating bacteria”)
• Facultative/obligate anaerobe • On blood agar:
different hemolysis
Biological characteristics
• Morphology & cultivation properties • G + , arranged in chains,
no special structure • Nutrient requirement: high
Fastidious (“flesheating bacteria”)
• facultative/obligate anaerobe • On blood agar:
different hemolysis
Biological characteristics • Classification ØHemolytic activity • αhemolytic strep.
Incomplete hemolysis (α) Opportunistic pathogens e.g., S.pneumoniae, S.viridans
• βhemolytic strep. Complete hemolysis (β) Main human pathogens e.g., S. pyogenes
• γstreptococcus No hemolysis, No pathogenicity e.g., enterococci.
Biological characteristics
ØAntigenic structure • Carbohydrate antigens
– groupspecific antigen – 20 groups (A~H, K~V) – Group A main human pathogens
• Protein antigens – typespecific antigen – M, R, T protein – Group A >60 serotypes
Cell wall
Streptococcus
Capsule Protein
Polysaccharide
Peptidoglycan
Biological characteristics • Resistance • Heat labile: killed at 60, 30 min
• Antibiotics sensitivity: penicillin, erythromycin, tetracycline, etc.
Pathogenicity (Strep. Group A)
• Virulence factors
– Surface structures LTA: adhere to host cells Mprotein:
a.Antiphagocytosis b.Be associated with rheumatic heart disease &
glomerulonephritis c.Adhere to epithelial cells
d.Clump platelet and leukocyte
Pathogenicity (Strep. Group A)
– Invasive enzymes Hyaluronidase (spreading factor) Streptokinase (SK)
Streptodornase (SD)
< Toxinsexotoxins • Streptolysin (hemolysin) • Erythrogenic toxin
Streptolysins
Polypeptide (28aa) Protein (MW60,000) Chemical
destroy WBC virulence of many tissues
destroy WBC, platelet virulence of MΦ, N.C
Biological activity
Weak Strong (ASO test) Antigenicity
oxygenstable oxygenlabile O 2
Streptolysin S (SLS) Streptolysin O (SLO) Properties
ASO: AntistreptolysinO, antibody
AntiSLO Test (ASO test) • Definition: a neutralization test between the toxin (SLO) and its specific antitoxin (ASO) which is used to diagnose or monitor rheumatic fever caused by Group A strep..
Pathogenicity (Strep. Group A)
• Diseases – Transmission:
Respiratory tract, trauma, gastrointestinal tract
< 3 types of infections <Pyogenic infection <Toxinassociated diseases <Hypersensitive disease
Pyogenic infection
–Local purulent infections: pharyngitis, tonsillitis; cellulitis, puerperal fever, erysipelas, impetigo; otitis, pneumonia, meningitis
<Systemic infection: septicemia
Abscess with surrounding cellulitis
• scarlet fever: – Pharyngitis → scarlet fever
Strawberry tongue
red rash paly around mouth
Toxinassociated diseases
Acute glomerulonephritis edema, hypertension, hematuria and proteinuria
Rheumatic fever involve: heart, joints, subcutaneous tissue, and CNS; fever, migratory polyarthritis, carditis
Hypersensitive disease
Diseases caused by other streptococci – Group B strep.
neonatal infection adult infections: endometritis, pneumonia, meningitis,
endocarditis – Group C strep.
epidemic sore throat, acute glomerulonephritis – Group G strep.sore throat, cellulitis, erysipelas – Group D strep. and enterococci
nosocomial infection urinary infection, biliary tract infection, peritonitis
Prevention and treatment
• Treat the pharyngitis and tonsillitis in time • Antibiotics: penicillin for the first choice
General properties • G + , arranged in pairs, bullet shape
• Capsule: polysaccharide • Blood agar or chocolate blood agar, fastidious
• αhemolysis • Autolysis • Bile solubility test: “+”
distinguish from other α hemolytic streptococci.
• Ferment inulin
Pathogenicity
• Virulence factor: • Capsule • Pneumolysin & Neuraminidase
• Main disease: • Pneumonia
Laboratory diagnosis
• Differentiate S.pneumoniae from other αhemolytic streptococcus
R Bile solubility test R Optochin sensitivity test
Positive Negative
R Capsule swollen reaction R Animal test
Treatment & prevention
(S.pneumoniae) • sensitive to a wide range of antimicrobial agents: Penicillin, erythromycin, chloramphenicol, Sulphonamides, clindamycin, vancomycin.
• Prevention: polysaccharide vaccine
Section 4 Neisseria
N. Meningitidis meningitis low prevalence but high mortality
N. Gonorrhoeae human gonorrhea high prevalence but low mortality
Genus Neisseria: >10 species
Common biological characteristics
• G , coffee beanshaped or kidneyshaped, in pairs
• capsules and pili • fastidious • Resistance: very low
polymorphonuclear cells
N. Meningitidis / meningococcus
• Pathogenesis ØVirulence factor: • Pili attach to nasopharyngeal mucosa • Capsule • Endotoxin damage capillary blood vessel Ø transmission: respiratory droplets ØDisease: epidemic cerebrospinal meningitis
N. Gonorrhoeae /gonococcus
• Virulence factors • Pili • IgA 1 protease • Outer membrane protein
(OMP) • LPS (endotoxin)
• Transmission: sexual contact; indirect contact; (basin, towel, etc)
• Diseases: Gonorrhea
Gonorrhea
Adults ØTransmission: STD (sexually transmitted disease) ØClinical disease: Genitourinary tract infection
Urethritis, prostatitis; epididymitis (male); cervix inflammation (female); infertility
Newborns ØOphthalmia neonatorum