ABSTRACT
Background: Group A streptococcus (GAS) causes a wide variety of diseases ranging from mild skin and soft-tissue infections to severe, life-threatening conditions. A fluctuating trend has been observed in the antibiotic resistance pattern from different parts of the world. The present study was undertaken to determine the prevalence of antibiotic resistance among GAS isolates and the underlying genetic mechanisms. Materials and Methods: Two hundred and six GAS isolates were characterised by antimicrobial susceptibility pattern, macrolide resistance phenotype (double-disc test) and resistance determinants by multiplex polymerase chain reaction. Results: All the isolates were susceptible to penicillin, vancomycin and linezolid. Erythromycin resistance was found in 53% of isolates with inducible macrolide, lincosamide and streptogramin B the predominant phenotype (63%) with ermB the major genetic determinant. Clindamycin resistance was observed in 33% of isolates with all being inducible resistant. Tetracycline resistance was found in 58% of isolates with tetM as the major genetic determinant (97%). Erythromycin and tetracycline co-resistance was found in 39% of tested GAS isolates. Conclusion: The erythromycin and tetracycline resistance in GAS continues to exist at high levels and may be attributed to the over-prescription and use of these antibiotics. Our findings indicate that the use of these antibiotics especially macrolides as empiric therapy in penicillin-allergic patients may not be appropriate.
ABSTRACT
Bone mass and strength achieved at the end of the growth period, simply designated as "Peak Bone Mass (PBM)", plays an essential role in the risk of osteoporotic fractures occurring in adulthood. It is considered that an increase of PBM by one standard deviation would reduce the fracture risk by 50 percent. As estimated from twin studies, genetics is the major determinant of PBM, accounting for about 60 to 80 percent of its variance. During pubertal maturation, the size of the bone increases whereas the volumetric bone mineral density remains constant in both genders. At the end of puberty, the sex difference is essentially due to a greater bone size in male than female subjects. This is achieved by larger periosteal deposition in boys, thus conferring at PBM a better resistance to mechanical forces in men than in women. Sex hormones and the IGF-1 system are implicated in the bone sexual dimorphism occurring during pubertal maturation. The genetically determined trajectory of bone mass development can be modulated to a certain extent by modifiable environmental factors, particularly physical activity, calcium and protein intakes. Prepuberty appears to be an opportune time to modify environmental factors that impinge on bone mineral mass acquisition.
La masa y fortaleza ósea conseguida al final del periodo de crecimiento, designada simplemente como masa ósea máxima (MOM), constituye un factor crítico en cuanto al riesgo de fracturas osteoporóticas en la edad adulta. Se considera que un aumento de MOM de una desviación estándar reduciría el riesgo de fracturas en 50 por ciento. Los estudios en gemelos han mostrado que la genética es el principal determinante de MOM, siendo responsable de 60 a 80 por ciento de su variación. Durante la maduración puberal el tamaño de los huesos aumenta mientras que su densidad mineral volumétrica permanece constante en ambos géneros. Al final de la pubertad la diferenciación sexual se debe básicamente al mayor tamaño de los huesos en hombres que en mujeres. Esto se consigue mediante una mayor deposición periosteal en los muchachos, confiriéndole así a la MOM mayor resistencia a las fuerzas mecánicas en hombres que en mujeres. Este dimorfismo sexual óseo que se presenta durante la maduración puberal se debe sobre todo a las hormonas sexuales y al factor de crecimiento insulínco 1 (IGF-1). La trayectoria genéticamente determinada de desarrollo de la masa ósea puede modularse hasta cierto punto mediante factores ambientales modificables, sobre todo la actividad física y la ingesta de calcio y proteínas. El periodo prepuberal parece ser el momento oportuno para modificar los factores ambientales que afectan la adquisición de masa mineral ósea.