Transcript Streptococcus pneumoniae
医学微生物学
Medical Microbiology
病原生物学教研室
Department of pathogenic Biology of Gannan Medical University
张文平
Chapter 10
Pyogenic bacterium
Pyogenic cocci
化脓性球菌 Gram-positive cocci Staphylococcus aureus 金黄色葡萄球菌 Streptococcus pyogenes Streptococcus pneumoniae 化脓性链球菌 肺炎链球菌 Gram-negative cocci Neisseria meningitides Neisseria gonorrhoeae 脑膜炎奈瑟菌 淋病奈瑟菌
Pyogenic bacillus
化脓性杆菌
Gram-negative
bacillus Pseudomonas aeruginosa 铜绿假单胞菌 Escherichia coli 大肠埃希菌属 Proteus 变形杆菌
Staphylococcus
葡萄球菌
Biological character
I. morphology II. culture III.Biochemical tests IV. typing
morphology
G + , mainly arranged in grape-like clusters
Gram staining
Culture
Individual colonies are circular, 2-3mm in diameter with a smooth, shiny surface;appear opaque and are often pigmented
Blood agar plate
Staph. aureus Staph. epidermidis
Golden-yellow
pathogenic
white
opportunists
Staph. saprophyticus
fawn
opportunists
Colonies of
Staph. Aureus
and
Staph. epidermidis
Important properties
All staphylococci produce catalase （ 触酶） H 2 O 2 →O 2 + H 2 O
S aureus
coagulase
Mannitol
fermentation
staphylococcus A protein
，
SPA
Binds to the Fc portion of IgG at the complement-binding site
Significance
Preventing the activation of complement
anti-phagocytic
coagglutination
resistance Resistant to dry, heat , salt
Pathogenesis
LTA Virulence factors Invasive enzyme : coagulase toxin
：
lysin
（
αβγ
）
leucocidin epidermolytic toxins enterotoxins TSST-1
Enterotoxin
肠毒素 Cause vomiting and watery, nonbloody diarrhea Superantigen Heat-resistant 100 ℃ 30min
Toxic shock syndrome toxin 1
毒素休克综合征毒素 -1 • • • Cause toxic shock Tampon – using menstruating women Individuals wit h wound infection Patients with nasal packing used to stop bleeding from the nose superantigen
Exfoliatin
表皮剥脱毒素 (
epidermolytic toxins)
Cause scalded-skin syndrome in young children Acts as protease( 蛋白酶 ) that cleaves desmosome( 桥粒 granular cell layer ) ， leading to the separation of the epidermis at the
coagulases
Free coagulase
Converts fibrinogen in citrated plasma into fibrin
Bound coagulase
reacts with fibrinogen to inhibit the phagocytosis of macrophages and damage of bactericide substances in humor by coating the organisms with fibrin
infections
1) purulent infection (1). local infection skin infection: hair folliculitis; boil （疖） ; carbuncle( 痈 ); impetigo （脓疱病） .
(think pus; limited local area) (2).organ infection: pneumonia; meningitis （脑膜炎）
Infections
(3).Systemic infection: Septicemia; pyemia 2) Toxin diseases (1). Food poisoning (enterotoxin) (2). TSS(Toxic shock syndrome) (3). SSSS(staphylococcal scalded skin syndrome): 3) Staphylococcal enteritis
(ii) Food poisoning. • The food becomes contaminated with the organism from human contact, grows and produces
enterotoxin
. • • • The organism
does not "infect"
on ingestion of food. Onset and recovery both occur within a few hours. Vomiting , nausea, diarrhea and abdominal pain are present.
(v)
Toxic shock syndrome
particularly after tampon use includes: • fever • • • rash （皮疹） desquamation vomiting （脱屑） • diarrhea Toxic shock toxin is involved.
The organism does not disseminate.
However, the toxin does and is responsible for the clinical features.
Laboratory diagnosis
* specimen: * pus * sputum (low respiratory tract infection) * * blood (septic shock, osteomyelitis, endocarditis) food/faeces or vomit (food poisoning) mid-stream urine cystitis 膀胱炎 ) (pyelonephritis 肾盂肾炎 or
Laboratory diagnosis
*direct smear :gram stain *isolation and identification: blood agar *coagulase test *Enterotoxin test and animal test
*Mannitol
fermentation
streptococcus
链球菌
streptococcus
Biological character
G+ ， arranged in chains of varying length culture Blood agar plate α-hemolytic streptococci β hemolytic streptococci γ streptococci antigen polysaccharide Surface protein antigen groups M R S T
Classsification:
(1).
Hemolytic activity : -hemolytic streptococcus Incomplete hemolysis, green zone around colonies * Opportunistic pathogens -hemolytic/pyogenic streptococcus Complete hemolysis, clear zone around colonies * major human pathogens -streptococcus No hemolyzation, no pathogenicity.
Classification of -hemolytic streptococcus Antigenic structure: Polysaccharide antigen (group-specific antigen). 19 groups Group A streptococci are main human pathogens protein antigen (type-specific antigen).
M protein: *presents in cell wall (group A) *Anti-phagocytosis *adhere to epithelial cells *clump platelet and leukocyte *heat stable; acid stable (pH 2)
pathogenesis
Virulance factors Invasive enzyme attachment toxin Hyaluronidas streptokinase DNAases LTA M protein Streptolysin (O,S) Pyrogenic exotoxin (scarlet fever toxin)
(1).Invasiveness
(i).surface structure * LTA(lipoteichoic acid) : adhere to sensitive cell (epithelial cell; platelet; RBC; WBC; lymphocyte; mucous membranes) * M-protein : ◆ anti-phagocytotic ◆ Common antigen---heart muscle cell (rheumatic fever) 风湿热 ◆ M-Ag Ab hypersensitivity(glomerulonephritis) 肾小球肾炎
(ii).enzyme
*Hyaluronidase (spreading factor) : Splits hyaluronic acids bacteria spread * Streptokinase (SK) : Lyse fibrin, prevent plasma clotting bacteria spread * Streptodornase (SD) : Resolve DNA bacteria spread
(2).Toxins---exotoxin (i) Streptolysin (hemolysin) StreptolysinO(SLO) oxygen-labile hemolysin O 2 (-SH-------S-S-) antigenicity-----ASO (antistreptolysin O) destroy WBC, pletelet virulence of MΦ, N.C
Streptolysin S(SLS ) oxygen stable O 2 (-SH------SH) weak antigen destroy WBC virulence of many tissues
( ⅱ ) Erythrogenic toxin toxin /scarlet fever toxin) (or pyrogenic produced by most strains of group A streptococci possess antigenicity, specifically neutralize the toxin cause scarlet fever protien heat stable antitoxin
Diseases of streptococcal infection
1 ) .
Infections of group A streptococci (1).
local purulent infections : -hemolytic *pharyngitis, 咽炎 (2).
*erysipelas 丹毒 *puerperal fever systemic infection : * septicemia 产褥热 *scarlet fever
(3). poststerptococcal diseases (hypersensitive disease) (i) acute glomerulonephritis ( group A) mechanism: *type III hypersensitivity (most) M protein-Ab immune complex *type II hypersensitivity common Ag deposition glomerular basement Membrane cross reacts with glomerular basement membrane activation C 3 ,C 5 tissue destruction tissue destruction
(ii) Rheumatic fever A streptococci) mechanism: *immune complex heart, joints (many types of group (deposition) type III hypersensitivity *common Ag reaction heart type II hypersensitivity cross-
Clinical diagnosis
Gram stain Serologic methods based on cultures from clinical specimens ASO Normal titer 1:400 Acute glomerulonephritis and acute rheumatic fever.
Prevention & treatment
*Treat the pharyngitis and tonsillitis in time, avoid the post streptococcal diseases.
*Antibiotics and chemical penicillin G for the first choice agents:
Streptococcus pneumoniae
Streptococcus pneumoniae
S. pneumoniae
is a leading cause of pneumonia in all ages (particularly the young and old), often after "damage" to the upper respiratory tract (e.g. following viral infection).
It also causes
middle ear infections
(otitis media). The organism often spreads causing
bacteremia
and
meningitis
.
S. pneumoniae
is α-hemolytic and there is no group antigen.
Direct Gram staining or detection of capsular antigen in
sputum
can be diagnostic.
The organism grows well on sheep blood agar.
Autolysin
Pneumococci are identified by solubility in bile.
An autolysin (peptidoglycan degrading enzyme) is released by bile from the cell membrane and binds to a choline-containing teichoic acid attached to the peptidoglycan. The autolysin then digests the bacterial cell wall resulting in lysis of the cell.
The optochin test is a presumptive test that is used to identify strains of
Streptococcus pneumoniae
. Optochin disks are placed on inoculated blood agar plates. Because
S. pneumoniae
is not optochin resistant, a zone of inhibition will develop around the disk where the bacteria have been lysed. This zone is typically 14mm from the disk or greater.
Not optochin sensitive optochin sensitive
Capsule
This is highly prominent in virulent strains and its carbohydrate antigens vary greatly in structure among strains. The capsule is anti-phagocytic and immunization is primarily against the capsule. Capsular vaccines are available for susceptible individuals; immunity is serotype-specific.
Neisseria
Gram negative cocci, usually arranged in pairs.
Some are normal inhabitants in respiratory tract. Others are human pathogens (eg: gonococcus,meningococcus ) …
Common biological characteristics
1.Gram negative cocci, kidney-shaped, in pairs have capsules and pili 2.Need enriched medium (chocolate blood agar ) 3. 5 ~ 10%CO2 4.Resistance: very weak “ fragile ” , extremely sensitive to drying, heat, cold
Neisseria meningitidis
脑膜炎奈氏菌
Meningococci and their colonies
Pathogenicity and immunity
1. Pathogenicity: (1) Human is the only natural host for pathogenic meningococci.
Child: susceptible (lacking specific Abs) (2) virulence factor: *Pili – attach to nasopharyngeal mucosa *capsule – antiphagocytosis *endotoxin – main pathogenic substance capillary tube, small blood vessel
2.Pathogenesis: epidemic cerebrospinal meningitis 流行性脑脊髓膜炎 clinical typing: common, outbreak, septicemic type
Clinical cause: 3 stages
(1)Organisms only 2 ~ cross nasoparynx ( nasopharyngeal infection : asymptomatic , most are carriers, 3% go to next stage ) (2) blood stream
blood contain cocci ) (3)meninges (meningitis. meninges pyogenic inflammation. spinal fluid contain cocci )
Immunity: group-specific antibody, cross-immunity between groups.
III. Laboratory diagnosis
1. specimen: spinal fluid, blood, nasopharyngeal swabs .
(*note: “ fragile ” bed-side inoculation) 2. direct smear : smear Gram stain (G diplococci, within white cells) 3. isolation and identification: specimen serum broth chocolate blood agar plate (5 and biochemical, serological identification 4.
serologic test : to detect the unknown Ag with given Ab ~ 10% CO2 ,37 C ) Gram stain
Prevention and treatment
1. Polysaccharide vaccine (group A, C) 2.Penicillin;cefotaxime; chloramphenicol
Neisseria gonorrhoeae
Gonococci and their colonies
1. Pathogenic factors
* Pilli: attach to epithelial cells (urinary gentital, RBC) * IgA 1 -protease: break down surface IgA antibodies.
*Outer membrane protein (OMP):
Diseases:
*Gonorrhea (STD: sexually transmitted disease) acute urethritis 尿道炎 (male); pelvic inflammatory 盆 腔 炎 (female) *Ophthalmia neonatorum→blindness 新生儿眼结膜炎
Laboratory diagnosis
Specimen: purulent genitourinary tract secretion of Isolation and identification: direct smear, culture, biochemical tests
Prevention and treatment
*penicillin----- Gonorrhea *silver nitrate neonatorum --- ophthalmia