Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Protein folding wikipedia , lookup
Bimolecular fluorescence complementation wikipedia , lookup
Protein mass spectrometry wikipedia , lookup
Protein structure prediction wikipedia , lookup
Protein purification wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
Western blot wikipedia , lookup
Bacteriology lecture no 5 2nd class *The Neisseriae* 1-The Neisseriae are gram –negative cocci that usually occur in pairs . 2-It includes two species Neisseriae gonorrhoeae (gonococci)and Neisseria meningitidis (meningococci),both are pathogenic for human. 3-Both typically are found associated with or inside polymorphonuclear cells. 4-Some Neisseriae are normal inhabitant of the human respiratory tract rarely if ever cause disease ,and occur extracellulary . 5-Gonococci and Meningococci are closely related ,with 70%DNA homology, and are differentiated by a few laboratory tests and specific characteristic . 6-Meningococci have polysaccharide capsules ,whereas gonococci do. Most importantly ,the two species differentiated by the usual clinical presentation of the disease they cause. 7-Meningococci typically are found in the upper respiratory tract and cause meningitis ,while gonococci cause genital infections. 1 Bacteriology lecture no 5 2nd class *Morphology and identification . A-Typically organisms -Typically Neisseriae is a gram-negative ,nonmotile diplococci. -Individual cocci are kidney –shaped ,when organisms occur in pairs ,the flat or concave sides are adjacent. B-Culture : -In 48 hours on enriched media e.g. modified –Thayer Martin –Lewis and New-York city. -Gonococci and meningococci form convex ,glistening elevated ,mucoid colonies 1-5 mm in diameter . -Colonies are transparent or opaque ,nonpigmented and nonhemolytic. 2 Bacteriology lecture no 5 2nd class C-Growth characteristic . -The Neisseriae grow best under aerobic condition ,but some will grow in an anaerobic environment . -They have complex growth requirements. -Most Neisseriae oxidize CHO, producing acid but not gas ,and their CHO pattern are a mean of distinguishing them. -Neisseriae produce oxidase and give positive oxidase reaction ,the oxidase test are a key test for identifying them. -Meningococci and gonococci grow best on media containing complex organic substance such as heated blood ,hemin and animals protein and in an atmosphere containing 5% CO2 e.g., candle jar. -The organisms are rapidly killed by drying ,sunlight ,moist heat and many disinfectants. 3 Bacteriology lecture no 5 2nd class -They produce autolytic enzymes that result in rapid swelling and lysis in vitro at 25Ċ and an alkaline Ph. NEISSERIA GONORRHOEAE -Antigenic structure. N.gonorrhoeae is antigenically heterogeneous and capable of changing its surface structure in vitro –and presumably in vivo ,to avoid host defenses .Surface structure include the following . A-Pilli(Fimbriae) It is the hair like appendages that extend up to several micrometer from the gonococcal surface .They enhance attachment to host cells and resistance to phagocytosis. 4 Bacteriology lecture no 5 2nd class B-Por.por protein extend through the gonococcal cell membrane ,it occur in trimers to form pores in the surface through which some nutrient enter the cells .Por protein may impact intracellular killing of gonococci within neutrophil by preventing phagosome lysozyme fusion. C-Opa protein :These proteins function in adhesion of gonococci within colonies and in attachment of gonococci to host cell receptors, such as heparin –related compounds and CD66 or carcinoembryonic antigenrelated cells adhesion molecules. D-RMP(protein 3) This protein is antigenically conserved in all gonococci. It is a reduction –modifiable protein (RMP)and changes its apparent molecular weight when in reduced state .It associate with Por in the formation of pores in the cell surface . E-Lipooligosaccharide.Toxicity in gonococcal infection is largely due to the endotoxic effect of LOS. The gonococcal LOS and the human glycosphingolipid of the same structural class react with the same monoclonal antibody ,The presence on the gonococcal surface of the same surface of the same surface structures as human cells helps gonococci evade immune recognition. 5 Bacteriology lecture no 5 2nd class F-Others protein such as: 1-Lip(H8)is a surface exposed protein that is heat – modifiable like Opa 2-Fbp(Ferric-binding protein)similar in molecular weight to pors is expressed when the available iron supply is limited e.g.in human infection. 3-IgA1 protease that splits and inactivates IgA1,a major mucosal immunoglobulin of humans ,and this protein also elaborates by Haemophilus influenzae and streptococcus pneumonia. *Antigenic Heterogeneity. -Gonococci have evolved mechanisms for frequently switching from one antigenic form (pilin ,opa or LPS)to another antigenic form of the same molecules. -since pilin ,opa and LPS are surface exposed antigen on gonococci ,they are important in the immune response to infection ;the molecules rapid switching from one antigenic form to another helps the gonococci elude the host immune system. *Pathogenesis and clinical finding : -Gonococci exhibit several morphological types of colonies ,but only piliated bacteria appear to be virulent . 6 Bacteriology lecture no 5 2nd class -Gonococci that form opaque colonies are isolated from men with symptomatic urethritis and from uterine cervical culture ,while those that form transparent colonies are isolated from those that are a symptomatic urethral infection ;and from invasive form of gonorrhea including salpingitis and disseminated infection . -Gonococci attack mucous membranes of the genitourinary tract ,eye ,rectum, and throat ,producing acute suppuration that may lead to tissue invasion ,this is followed by chronic inflammation and fibrosis. -In males :There is usually urethritis ,with yellow creamy pus and painful urination .This process may extend to the epididymis. -In females: The primary infection is in the endocervix and extend to the urethra and vagina ,giving rise to mucopurulent discharge ,this may extend to the uterine tubes causing salpingitis ,fibrosis ,so infertility occur in 20% of women with gonococcal infection . -Gonococcal bacteremia leads to skin lesion especially hemorrhagic papules and pustules on the hands ,forearm ,feet and leg and also cause suppurative arthritis ,usually of knee ,ankles and wrists. 7 Bacteriology lecture no 5 2nd class -Gonococci can be cultured from blood or joint fluid of only 30% of patient with gonococcal arthritis . -Gonococcal ophthalmia neonatarum an infection of the eye of the newborn is required during passage through an infected birth canal .The initial conjunctivitis rapidly progresses and if untreated result in blindness. -To prevent gonococcal ophthalmia neonatarum ,instillation of tetracycline erythromycin ,or silver nitrate into the conjunctival sac of the newborn is compulsory in the U.S . 8 Bacteriology lecture no 5 2nd class -Immunity: Repeated gonococcal infection are common ,protective immunity to reinfection does not appear to develop as part of the disease process ,because of the antigenic variety of gonococci. Neisseria meningitidis *Antigenic structure :at least 13 serogroup of meningococci have been identified by immunological specifity of capsular polysaccharide -The most important serogroup associated with disease in humans are A,B,C,X,and W-135. -Meningococcal antigens are found in blood and CSF of patients with active disease . -The outer membrane proteins of meningococci have been divided into classes on the basis of molecular weight .All strain have either class1,class2,or class3 proteins these are analogous to the por protein of gonococci and are responsible for the serotypes specificity of meningococci. -This protein help form pores in the meningococcal cell wall, meningococci are piliated ,but unlike gonococci ,they don’t form distinctive colony types indicating piliated bacteria 9 Bacteriology lecture no 5 2nd class -Meningococcal LPS is responsible for many of the toxic effect found in meningococcal disease . *Pathogenesis and clinical finding. -Human are the only natural hosts for whom meningococci are pathogenic. -The nasopharynx is the portal of entry ,there the organism attach to epithelial cells with the aid of Pilli, they may form part of the transient flora without producing symptoms. -From the nasopharynx ,organisms may reach the blood stream producing bacteremia ,the symptoms may be like those of an upper respiratory tract infection. -Fulminant meningococcemia is more severe ,with high fever and hemorrhagic rash ,there may be disseminated intravascular coagulation and circulatory collapse. -Meningitis is the most common complication of meningococcemia ,it usually begins with intense headache ,vomiting ,and stiff neck and progresses to coma within a few hours. -Neisseria bacteremia is favored by the absence of bactericidal antibodies (IgM,and IgG)inhibition of serum bactericidal action by a blocking IgA antibodies ,or a 10 Bacteriology lecture no 5 2nd class complement deficiency (C5,C6,C7,or C8). *Immunity. -Immunity to meningococcal infection is associated with the presence of specific ,complement-dependent ,bactericidal antibodies in the serum *Other Neisseriae such as Neisseria luctimica,Neisseria sicca,Neisseria subflara,Neisseria cinerea,Neisseria mucosa are also numbers of normal flora of the respiratory tract ,particularly nasopharynx. 11