An algebraic Kekulé structure of a benzenoid hydrocarbon is obtained from an ordinary Kekulé structure by inscribing into each hexagon the number of pi-electrons which (according to this Kekulé structure) belong to this hexagon. We show that in the case of catafusenes, there is a one-to-one correspondence between ordinary and algebraic Kekulé structures. On the other hand, in the case of perifusenes, one algebraic Kekulé structure may correspond to several ordinary Kekulé structures.

The endodontium and periodontium are closely related and disease of one may lead to secondary disease in the other. The differential diagnosis of endodontic and periodontal disease is of vital importance, so that the appropriate treatment can be done. Microorganisms play a primary role in endodontic and periodontal infections. The magnitude of the host response will be directly proportional to the virulence and the number of microbial cells present. Tissue damage caused by bacteria is mediated by either direct or indirect mechanisms. Direct harmful effects caused by bacteria involve their products, such as enzymes (collagenase, hyaluronidase, condroitinase, acid phosphatase), exotoxins and metabolites (bytrate, propionate, ammonium polyamines, sulphured compounds). In addition, bacterial components such as peptidoglycan, teichoic acid, fimbriae, outer membrane proteins, capsule, and lypopolysaccharide, stimulate the development of host immune reaction capable of causing severe tissue destruction.

Neonatal BCG vaccination reduces the risk of tuberculosis and provides protection higher than 80% against the development of meningeal and miliary tuberculosis in newborns. Tuberculosis meningitis remains a major problem and also an important cause of death in some countries. In countries with high and moderate incidence of tuberculosis, prevention from the most severe complications of tuberculosis can be achieved only with a high coverage of the universal BCG neonatal immunization, being higher than 98% in the cohort of newborns. The decrease in BCG immunization coverage within immunization program during the year 2003 in Bosnia and Herzegovina influenced the increase in tuberculous meningitis. During 2002, when coverage with BCG vaccination in cohort of newborns was 90%, the incidence rate of tuberculous meningitis was 19. 04%oo. With the 68% decrease in BCG immunization coverage in the cohort of newborns in Bosnia and Herzegovina during the year 2003, the incidence of tuberculous meningitis raised to 33 33%oo. It has been proven that the 22% decrease of the neonatal BCG immunization coverage in the cohort of newborns /vaccination program of children/ caused 175 times higher number of the tuberculous meningitis cases. Newborns affected by the tuberculous meningitis were not BCG vaccinated. BCG vaccine provided effective protection against tuberculous meningitis, as well against the death of newborns caused by tuberculosis.