Change in Pneumococcus Serotypes but not Mortality or Morbidity in Pre- and Post-13-Valent Polysaccharide Conjugate Vaccine Era: Epidemiology in a Pediatric Intensive Care Unit over 10 Years.

Aim: Pneumococcus is a common commensal and an important pathogen among children for which immunization is available. Some serotypes occasionally cause severe pneumococcal disease with high mortality and morbidity. We reviewed all pneumococcal serotypes and mortality/morbidity in a pediatric intensive care unit (PICU) following universal pneumococcal conjugate vaccine (PCV) immunization. Methods: A 13-valent PCV was introduced in the universal immunization program in late 2011 in Hong Kong. We retrospectively reviewed all pneumococcal serotypes in the pre-(2007-11) and post-(2012-16) 13-valent PCV era. Results: There were 29 (1.9%) PICU patients with pneumococcal isolation, of which 6 died (20% motality). Serogroups 6 and 19 predominated before and Serogroup 3 after 2012. In the post-13-valent PCV era, the prevalence of pneumococcus isolation in PICU was increased from 1 to 2% (p = 0.04); Serogroup 3 was the major serotype of morbidity, despite supposedly under vaccine coverage. The majority of pneumococcus were penicillin-sensitive (94%) in the post 13-valent PCV era. All pneumococcus specimens were sensitive to cefotaxime and vancomycin. Binary logistic regression showed that there were reductions in Serogroup 6 (odds ratio [OR], 0.050; 95% confidence interval [CI], 0.004-0.574; p = 0.016) and Serogroup 19 (odds ratio [OR], 0.105; 95% confidence interval [CI], 0.014-0.786; p = 0.028) but not mortality or morbidity for patients admitted after 2012. Conclusions: SPD is associated with significant morbidity and mortality, despite treatment with systemic antibiotics and ICU support. The expanded coverage of 13-valent PCV results in the reduction of Serotypes 6 and 19 but not mortality/morbidity associated with SPD in the setting of a PICU.

Late Onset Streptococcus agalactiae Meningitis following Early Onset Septicemia: A Preventable Disease?

We report a neonate who presented with early onset Streptococcus agalactiae or group B streptococcus (GBS) septicemia within 24 hours of birth. After discharge at day 14, she went on to develop late onset GBS meningitis at 36 days of age. The infant was treated with intravenous antibiotics on both occasions and eventually discharged home with no apparent sequelae. We address issues associated with GBS infection in infancy including the demographics, risk factors, and the risk of late onset GBS meningitis following an early onset GBS infection. The major source of GBS in early onset GBS disease is maternal birth canal GBS colonization. On the other hand, nosocomial cross-infection is an important source of GBS in late onset disease. Penicillin remains the current treatment of choice for GBS infection. Given the rapid onset and progression within hours of birth and lack of an effective solution for preventing late onset GBS, administration of an effective GBS vaccine in pregnancy could provide a sensible and cost-effective solution in all settings.

A molecular and chemical perspective in defining melatonin receptor subtype selectivity.

Melatonin is primarily synthesized and secreted by the pineal gland during darkness in a normal diurnal cycle. In addition to its intrinsic antioxidant property, the neurohormone has renowned regulatory roles in the control of circadian rhythm and exerts its physiological actions primarily by interacting with the G protein-coupled MT1 and MT2 transmembrane receptors. The two melatonin receptor subtypes display identical ligand binding characteristics and mediate a myriad of signaling pathways, including adenylyl cyclase inhibition, phospholipase C stimulation and the regulation of other effector molecules. Both MT1 and MT2 receptors are widely expressed in the central nervous system as well as many peripheral tissues, but each receptor subtype can be linked to specific functional responses at the target tissue. Given the broad therapeutic implications of melatonin receptors in chronobiology, immunomodulation, endocrine regulation, reproductive functions and cancer development, drug discovery and development programs have been directed at identifying chemical molecules that bind to the two melatonin receptor subtypes. However, all of the melatoninergics in the market act on both subtypes of melatonin receptors without significant selectivity. To facilitate the design and development of novel therapeutic agents, it is necessary to understand the intrinsic differences between MT1 and MT2 that determine ligand binding, functional efficacy, and signaling specificity. This review summarizes our current knowledge in differentiating MT1 and MT2 receptors and their signaling capacities. The use of homology modeling in the mapping of the ligand-binding pocket will be described. Identification of conserved and distinct residues will be tremendously useful in the design of highly selective ligands.