Behavioral
Bacterial and viral meningitis are contagious, but neither is as contagious as the common cold or flu. Both can be transmitted through droplets of respiratory secretions during close contact such as kissing, sneezing or coughing on someone, but bacterial meningitis cannot be spread by only breathing the air where a person with meningitis has been. Viral meningitis is typically caused by enteroviruses, and is most commonly spread through fecal contamination. The risk of infection can be decreased by changing the behavior that led to transmission. Vaccination
Since the 1980s, many countries have included immunization against Haemophilus influenzae type B in their routine childhood vaccination schemes. This has practically eliminated this pathogen as a cause of meningitis in young children in those countries. In the countries in which the disease burden is highest, however, the vaccine is still too expensive. Similarly, immunization against mumps has led to a sharp fall in the number of cases of mumps meningitis, which prior to vaccination occurred in 15% of all cases of mumps.Meningococcus vaccines exist against groups A, B, C, W135 and Y. In countries where the vaccine for meningococcus group C was introduced, cases caused by this pathogen have decreased substantially. A quadrivalent vaccine now exists, which combines four vaccines with the exception of B; immunization with this ACW135Y vaccine is now a visa requirement for taking part in Hajj.
Chemistry
Vitamin K is a fat-soluble vitamin that is stable in air and moisture but decomposes in sunlight. It is a polycyclic aromatic ketone, based on 2-methyl-1,4-naphthoquinone, with a 3-phytyl substituent. It is found naturally in a wide variety of green plants, particularly in leaves, since it functions as an electron acceptor during photosynthesis, forming part of the electron transport chain of photosystem I. Biological function
The best-known function of vitamin K in animals is as a cofactor in the formation of coagulation factors II (prothrombin), VII, IX, and X by the liver. It is also required for the formation of anticoagulant factors protein C and S. It is commonly used to treat warfarin toxicity, and as an antidote for coumatetralyl. Vitamin K is required for bone protein formation. Biosynthesis
Vitamin K1 is synthesized from chorismate, a compound produced from shikimate via the shikimate pathway. The conversion of chorismate to vitamin K1 comprises a series of nine steps:
Chorismate is isomerized to isochorismate by isochorismate synthase, or MenF (menaquinone enzyme). Addition of 2-oxoglutarate to isochorismate by PHYLLO, a multifunctional protein comprising three different enzymatic activities         (MenD, H, and C). Elimination of pyruvate by PHYLLO. Aromatization to yield o-succinyl benzoate by PHYLLO. O-succinylbenzoate activation to corresponding CoA ester by MenE. Naphthoate ring formation by naphthoate synthase (MenB/NS). Thiolytic release of CoA by a thioesterase (MenH). Attachment of phytol chain to the naphthoate ring (MenA/ABC4). Methylation of the precursor at position 3 (MenG).