Neisseria Microbiology Lecture Notes 2024-2025 PDF

Ninevah University Medicine College Microbiology Department 2024 - 2025 Dr. Saba Abdul Salam Hamid Al-Sultan [email protected]  3. Neisseria (Gram Negative Cocci) The lecture overview about 1. Clinical features of Neisser...

Ninevah University Medicine College Microbiology Department 2024 - 2025 Dr. Saba Abdul Salam Hamid Al-Sultan [email protected]  3. Neisseria (Gram Negative Cocci) The lecture overview about 1. Clinical features of Neisseria 2. Important properties of Neisseria 3. virulence factors of Neisseria P:2 Neisseria The genus Neisseria contains two important human pathogens: Neisseria meningitidis and Neisseria gonorrhoeae. First: N meningitidis: mainly causes meningitis and meningococcemia (When someone has meningococcal septicemia, the bacteria enter the bloodstream and multiply, damaging the walls of the blood vessels. Meningococcemia. Note purpuric rash lesions on the leg caused by endotoxin-mediated disseminated intravascular coagulation (DIC) In the United States, it is the leading cause of death from infection in children. P:3 Second: N gonorrhoeae causes 1. gonorrhea , the second most common notifiable bacterial disease in the United States 2. It also causes neonatal conjunctivitis (ophthalmia neonatorum) ((The other common cause of neonatal conjunctivitis is Chlamydia trachomatis )) 3. and pelvic inflammatory disease (PID). Note that Neisseria meningitidis is also known as the meningococcus (plural, meningococci), and Neisseria gonorrhoeae is also known as the gonococcus (plural, gonococci). P:4 Clinical features of Neisseria P:5 Important properties of Neisseria Neisseria spp. is a Gram-negative Cocci. Aerobic (Oxidative metabolism ) Do not possess flagella or spores Capsulated and possess pili require enriched complex media and CO2 diplococcus that has a flattened or concave the shape resembles paired kidney beans within neutrophils; Strict parasites, do not survive long outside of the host its size ranges between 0.6–0.8 μm. They are oxidase, Oxidase-positive, non-acid-fast cocci Produce catalase and oxidase P:6 P:7 Important Properties and virulence factors of Neisseria 1- N meningitidis (meningococcus) has a prominent polysaccharide capsule P:8 P:9  Properties of the polysaccharide Capsule of Meningococcus 1- N meningitidis (meningococcus) has a prominent polysaccharide capsule that enhances virulence by its antiphagocytic action and induces protective antibodies antigenic properties. Meningococci are divided into at least 13 serologic groups on the basis of the antigenicity of their capsular polysaccharides. Five serotypes cause most cases of meningitis and meningococcemia: A, B, C, Y, and W. Serotype A is the leading cause of epidemic meningitis worldwide. Serotype B accounts for most diseases in the United States. The antigen detected In the spinal fluid of patients with meningitis Capsule antigens are used in the formulation and manufacture of vaccines P : 10 P : 11 2- N. gonorrhoeae (gonococus) has no polysaccharide capsule but has multiple serotypes based on the antigenicity of its pilus protein. There is marked antigenic variation in the gonococcal pili as a result of chromosomal rearrangement; more than 100 serotypes are known. Gonococci have three outer membrane proteins (proteins I, II, and III). Protein II plays a role in attachment of the organism to cells and varies antigenically as well. P : 12 Antigenic properties P : 13 Neisseriae are gram-negative bacteria and contain endotoxin in their outer membrane. Note that the endotoxin of Neisseriae consist of lipo- oligosaccharide (LOS), in contrast to the lipopolysaccharide (LPS) found in enteric gram-negative rods. Both LPS and LOS contain lipid A, but the oligosaccharide part of LOS contains few sugars, whereas the polysaccharide part of LPS contains a long repeating sugar side chain. P : 14  The growth of both organisms (N. meningitidis and N. gonorrhoeae). Is inhibited by toxic trace metals and fatty acids found in certain culture media ( e.g., blood agar plates). They are therefore cultured on "chocolate" agar containing blood heated to 80°C, which inactivates the inhibitors. Neisseriae are oxidase-positive (i.e., they possess the enzyme cytochrome c). This is an important laboratory diagnostic test in which colonies exposed to phenylenediamine turn purple or black as a result of oxidation of the reagent by the enzyme P : 15 P : 16 Chocolate Agar: is a highly nutritious medium for the isolation and cultivation of fastidious microorganisms such as Neisseria. Bacterial colonies usually appear after 24–48 hours of growth. Chocolate agar Blood agar P : 17 Dr. Saba Al-Sultan P : 18