医学授课蓝黑模板之微生物学MedicalMicrob课件

1、Medical MicrobiologyLecture 3Dr. Saleh M Y OTHPhDMedical Molecular Biotechnology and Infectious Diseases02/10/2010IMS - MSUSystemic BactreiologyMedical MicrobiologyLecture STREPTOCOCCI Systemic Bactreiology STREPTOCOCCI Systemic BactreiWords must to be knownGroup A streptococcus (S. pyogenes)Lancefi

2、eld groupsHemolysis (alpha, beta, gamma)Bacitracin susceptibility test M, T, R proteinsStreptolysins O and SF protein/lipoteichoic acidRheumatic fever/carditis/arthritisGlomerulonephritisScarlet feverToxic shock-like syndrome/bacteremia“Flesh-eating bacteria”Pyrogenic toxinErythrogenic toxinGroup B

3、streptococcus (S.agalactiae)Neonatal septicemia/meningitis CAMP testHippurate hydrolysis testGroup D streptococcusUrinary tract infection/ endocarditis Bile-esculin testEnterococci Non-enterococciLarge colonyMinute colony Viridans streptococciDental caries/endocarditis Words must to be knownGroup A

4、Streptococcus pyogenesDuring the infection, this bacteria produce pus - One of the most important pathogens- Gram positive cocci in chains- Lancefield Serological Group A- Beta Hemolytic on blood agarStreptococcus pyogenesDuringGram Stain of S. pyogenesStreptcoccus pyogenesS. agalactiaS. peumoniaeGr

5、am Stain of S. pyogenesStrepHemolysis on Blood Agar PlatesBeta hemolysis-organisms excretes potent hemoysins which completely lyse RBCs (complete hemolysis) thus a clear zone appears around colony. S. pyogenesAlpha hemolysis-organism excretes hemolysins which partially break down rbc (incomplete hem

6、olysis) thus a greenish zone appears around colony. S. pneumoniaeHemolysis on Blood Agar PlatesS.pyogenesS. pneumoniaBeta hemolysisAlpha hemolysisS.pyogenesS. pneumoniaBeta hemStreptococci facultative anaerobe Gram-positive chains or pairs catalase negative (staphylococci are catalase positive)Strep

7、tococcus in chains (Gram stain) Streptococci Streptococcus in Streptococci Lancefield groupsone or more species per groupcarbohydrate antigensStreptococci Groupable streptococci 1- A, B and Dfrequent2- C, G, F less frequentGroupable streptococci 1- A, BNon-groupable1- S. pneumoniaepneumonia 2- virid

8、ans streptococcie.g. S. mutansdental cariesNon-groupable1- S. pneumoniaehemolysis reaction - sheep blood agar a- (beta-) complete clearing A and Bb- (alpha-)partial hemolysis green colorc- (gamma-) no lysisWhite colonieshemolysis reaction - sheep bloHemolysis1- Groups A an B -hemolysis2- Group D or

9、-hemolysis3- S. pneumoniae and S. viridans -hemolysisHemolysis1- Groups A an B hemolysis reaction + one characteristic presumptive identification hemolysis reaction + one charaGroup A streptococcus (S. pyogenes)Group A streptococcal infections affect all agespeak incidence at 5-15 years of ageGroup

10、A streptococcus (S. pyoS. pyogenes suppurative 1- non-invasive - pharyngitis - skin infection, impetigo2- invasive bacteremia - toxic shock-like syndrome - flesh eating bacteria- pyrogenic toxinS. pyogenes suppurative 1- noPyrogenic toxinStreptococcus pyogenes and Staphylococcus aureus express pyrog

11、enic toxin superantigens (PTSAgs) that are associated with toxic shock syndrome (TSS) and staphylococcal food poisoning (SFP). Most PTSAgs cause TSS in deep-tissue infections, whereas only TSS toxin 1 (TSST-1) is associated with menstrual, vaginal TSS. In contrast, SFP has been linked only with stap

12、hylococcal enterotoxins (SEs). Pyrogenic toxinStreptococcus pPyrogenic toxin Because of the differential abilities of PTSAgs to cause systemic or localized symptoms in a site-dependent manner, these toxins have abilities to cross mucosal barriers. The activity of three PTSAgs when delivered orally,

13、vaginally, or intravenously to rabbits and orally to monkeys in some experimental studies.Pyrogenic toxin Because of thPyrogenic toxin1- superantigen2- T cell mitogen 3- activates immune systemPyrogenic toxin1- superantigenScarlet fever- rash - erythrogenic toxinScarlet fever- rash 医学授课蓝黑模板之微生物学Medi

14、calMicrob课件non-suppurativerheumatic fever - inflammatory disease- life threatening- chronic sequalae fever heart jointsrheumatic NOT rheumatoid arthritisRheumatic fever is an inflammatory disease that occurs following a Group A streptococcal infection, (such as strep throat or scarlet fever). Believ

15、ed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after a streptococcal infection. Acute rheumatic fever commonly appears in children between the ages of 5 and 15, with only 20% of first-time attacks oc

16、curring in adults. The illness is so named because of its similarity in presentation to rheumatism. non-suppurativerheumatic feverRheumatic fever -etiologyM protein cross-reacts heart myosin autoimmunityCell wall antigens poorly digested in vivopersist indefinitelyRheumatic fever -etiologyM proRheum

17、atic feverPenicillinterminates pharyngitisdecreases carditis Rheumatic feverPenicillinAcute glomerulonephritisimmune complex disease of kidneyAcute glomerulonephritisimmuneMajor pathogenesis factorslipoteichoic acid /F proteinfimbriaebinds to epithelial cells M protein anti-phagocyticMajor pathogene

18、sis factorslipoS. pyogenesfibronectinlipoteichoic acid/F-proteinepithelial cellsS. pyogenesfibronectinlipoteicM protein M proteinfibrinogenrrrpeptidoglycanrrrIgGComplement IMMUNENON-IMMUNEM protein M proteinfibrinogenrM proteinmajor target natural immunitystrain variationantigenicityre-infectionoccu

19、rs with different strainM proteinmajor target CapsulesAnti-phagocyticmucoid strainsCapsulesAnti-phagocyticIsolation and identification -hemolytic colonies bacitracin inhibits growth -hemolytic colonies group A antigenBacitracin is a mixture of related cyclic polypeptides produced by organisms of the

20、 licheniformis group of Bacillus subtilis var Tracy, isolation of which was first reported in 1945.As a toxic and difficult-to-use antibiotic, bacitracin does not work well orally. However, it is very effective topically, and is a common ingredient of eye and skin antibiotic preparations. Its action

21、 is on gram-positive cell walls. It can cause contact dermititis due to allergic sensitivity to it.Isolation and identification -hemolysishemolysin O sensitive oxygenhemolysin Sinsensitive oxygen-hemolysishemolysin O Modern Rapid “Strep” TestThroat swab extract (+/- streptococcal antigen)AntibodyLip

22、osome+-Streptococcal antigenModern Rapid “Strep” TestThroaPost-infectious diagnosis (serology)antibodies to streptolysin O important if delayed clinical sequelae occurPost-infectious diagnosis (serTraditional serotyping of proteins:- M - T - R TypingModern:- Sequencing of M protein geneTraditional s

23、erotyping of protGroup B streptococcusneonatal meningitissepticemiatransmission vaginal floraGroup B streptococcusneonatal Group B streptococcus - identification hemolysishippurate hydrolysisCAMP reactionincreases hemolysis of S. aureus Group B streptococcus - idenGroup D streptococcusGrowth on bile esculin agarblack precipitate 6.5% saline grow enterococcino growth non-enter