Molecular typing of Treponema pallidum strains in western Canada: predominance of 14d subtypes.

BACKGROUND: Resurgence of syphilis in Canada and worldwide requires laboratories to update their methods for molecular epidemiology investigation and surveillance. This study utilizes polymerase chain reaction diagnostic tests for syphilis, identifies macrolide resistance, and uses a molecular typing system to characterize Treponema pallidum clinical strains causing syphilis in Alberta and Northwest Territories, Canada. METHODS: In total 449 specimens including genital swabs, whole blood, sera, and cerebrospinal fluid were obtained from 374 patients with suspect syphilis in Alberta and Northwest Territories. Molecular subtyping was based on genetic characterization of treponemal repeat genes, arp and tpr. Detection of macrolide resistance was accomplished by identification of the 23S rRNA gene mutation associated with the resistance pattern. RESULTS: Forty-nine specimens obtained from 43 patients were found to be positive for T. pallidum DNA using bmp, tpp47 and polA polymerase chain reaction assays. Four molecular subtypes were identified, with one type, 14d, accounting for 70% of all cases and 83% of typeable strains. Seven patients (16%) were found to be infected by macrolide-resistant strains, of which 6 were men who have sex with men and 1 whose infection was acquired in China. CONCLUSIONS: A single molecular type of T. pallidum, characterized as 14d, caused the majority of the syphilis cases identified in this study. A more discriminatory typing method would be required to determine if these strains are clonal. Treatment of infectious syphilis with macrolide antibiotics should be restricted to patient populations where resistance is rare and clinical and serological follow up of patients is possible.

A comparison of pertussis rates in the Northwest Territories: Pre- and postacellular pertussis vaccine introduction in children and adolescents.

INTRODUCTION: During the past decade, a trend toward increasing cases of Bordetella pertussis in older children and adults has been witnessed in Canada. The National Advisory Committee on Immunization now recommends that the adult formulation of the acellular pertussis (adult dTap) vaccine combined with diphtheria and tetanus toxoids be substituted for diphtheria and tetanus toxoids alone for the 14- to 16-year-old booster dose. In October 2000, the government of the Northwest Territories was one of the first to adopt adult dTap into their territorial immunization program free of charge. OBJECTIVE: To evaluate the effect of the acellular pertussis vaccine in children and adolescents on the epidemiology of pertussis in the Northwest Territories. METHODS: Pertussis is a reportable disease in the Northwest Territories, and data on the incidence rates of pertussis are available from 1989 to 2004. The present study reviews pertussis cases during three four-year periods: the whole-cell vaccine era (1993 to 1996); the preadult dTap era (1997 to 2000); and the postadult dTap era (2001 to 2004). RESULTS: The incidence of pertussis decreased from 18.0 cases per 10,000 population in 1993 to 0.2 cases per 10,000 population in 2004. The number of cases decreased from 186 to 129 to 19 cases in the three chronological time periods (ie, whole-cell vaccine era, preadult dTap era and postadult dTap era, respectively), with the most substantial reduction coming with the introduction of postadult dTap. CONCLUSIONS: There appears to be a decrease in the incidence of pertussis with the targeted introduction of adult dTap in the Northwest Territories.

Over-expression of hydroxynitrile lyase in transgenic cassava roots accelerates cyanogenesis and food detoxification.

Cassava (Manihot esculenta, Crantz) roots are the primary source of calories for more than 500 million people, the majority of whom live in the developing countries of Africa. Cassava leaves and roots contain potentially toxic levels of cyanogenic glycosides. Consumption of residual cyanogens (linamarin or acetone cyanohydrin) in incompletely processed cassava roots can cause cyanide poisoning. Hydroxynitrile lyase (HNL), which catalyses the conversion of acetone cyanohydrin to cyanide, is expressed predominantly in the cell walls and laticifers of leaves. In contrast, roots have very low levels of HNL expression. We have over-expressed HNL in transgenic cassava plants under the control of a double 35S CaMV promoter. We show that HNL activity increased more than twofold in leaves and 13-fold in roots of transgenic plants relative to wild-type plants. Elevated HNL levels were correlated with substantially reduced acetone cyanohydrin levels and increased cyanide volatilization in processed or homogenized roots. Unlike acyanogenic cassava, transgenic plants over-expressing HNL in roots retain the herbivore deterrence of cyanogens while providing a safer food product.