Robert Bortolussi

Epidemic Listeriosis — Evidence for Transmission by Food

The bacterium Listeria monocytogenes is a motile, gram-positive coccobacillus that can frequently be isolated from soil, water, and vegetation. It is a common cause of meningoencephalitis and abort...

Reducing the pain of childhood vaccination: an evidence-based clinical practice guideline (summary)

Injections for vaccinations, the most common source of iatrogenic pain in childhood,[1][1] are administered repeatedly to almost all Canadian children throughout infancy, childhood and adolescence.[2][2] The pain associated with such injections is a source of distress for children, their parents and

Role of MyD88 in Diminished Tumor Necrosis Factor Alpha Production by Newborn Mononuclear Cells in Response to Lipopolysaccharide

ABSTRACT Human newborns are more susceptible than adults to infection by gram-negative bacteria. We hypothesized that this susceptibility may be associated with a decreased response by leukocytes to lipopolysaccharide (LPS). In this study, we compared LPS-induced secretion of tumor necrosis factor alpha (TNF-α) by mononuclear cells (MNC) from adult peripheral blood and newborn umbilical cord blood in vitro and attempted to determine the mechanisms involved in its regulation. At a high concentration of LPS (10 ng/ml) and in the presence of autologous plasma, MNC from adults and newborns secreted similar amounts of TNF-α. However, in the absence of plasma, MNC from newborns secreted significantly less TNF-α compared to MNC from adults. Moreover, at a low concentration of LPS (0.1 ng/ml) and in the presence of plasma, TNF-α secretion was significantly lower for newborn MNC compared to adult MNC. Adults and newborns had similar numbers of CD14 and Toll-like receptor 4 (TLR-4)-positive cells as measured by flow cytometry. However, the intensity of the CD14 marker was greater for adult than for newborn cells. Incubation of cells with LPS led to an increase in CD14 and TLR-4 intensity for adult cells but not for newborn cells. The effect of LPS stimulation of adult or newborn cells was similar for ERK, p38, and IκBα phosphorylation, as well as IκBα degradation. Finally, we assessed levels of the TLR-4 adapter protein, the myeloid differentiation antigen 88 (MyD88). We found a direct relation between adult and newborn TNF-α secretion and MyD88, which was significantly decreased in newborn monocytes. Since TLR-4 signals intracellularly through the adapter protein, MyD88, we hypothesize that MyD88-dependent factors are responsible for delayed and decreased TNF-α secretion in newborn monocytes.

Persistence of pertussis in an immunized population: Results of the Nova Scotia Enhanced Pertussis Surveillance Program

An enhanced pertussis surveillance and laboratory diagnosis program was initiated in the Halifax metropolitan area of Nova Scotia to better delineate the epidemiology of pertussis. During the 28 months of the study, 526 cases of pertussis were identified (overall yearly incidence: 74 cases per 100,000 population). Laboratory confirmation was obtained in 168 (32%) cases, including 111 (21%) by culture. Peak incidence occurred among children 2 to 5 years of age; the highest morbidity rate was seen in children less than 1 year of age. Hospitalization was required for 22 (4.2%) patients; 14 (64%) of those hospitalized were less than 1 year of age. Most (91%) patients had received at least three doses of pertussis vaccine; vaccine efficacy was estimated at 45%. The surveillance program demonstrated that the incidence of pertussis in Nova Scotia, although among the highest in North America, is still underestimated. A ninefold increase in cases was identified over the comparable period of the previous year, largely because patients meeting clinical criteria were reported. By supplementing culture techniques with immunofluorescent staining and serologic methods, we increased the rate of laboratory confirmation from 17% to 65%, suggesting that strict clinical criteria accurately reflect accurately reflect incidence. We conclude that pertussis remains a significant health problem in Nova Scotia, despite nearly universal vaccination.

Listeriosis: a primer

Serious outbreaks of food-borne illness, whether regional or national, dramatically raise community anxiety about personal health and increase the workloads of front-line physicians. The drama further increases when the offending microbe is not well known. This primer on listeriosis hones in on the

A Randomized, Placebo-Controlled Trial of Erythromycin Estolate Chemoprophylaxis for Household Contacts of Children With Culture-Positive Bordetella pertussis Infection

Context. Household contacts of patients with pertussis are at increased risk of acquiring infection. Chemoprophylaxis has been recommended to decrease transmission, particularly to young infants who are at increased risk of severe disease. Although epidemiologic investigations of outbreaks have suggested a benefit, there have been no prospective studies evaluating the efficacy of chemoprophylaxis in preventing secondary cases of pertussis. Objective. To determine whether erythromycin estolate chemoprophylaxis is effective in household contacts of children with culture-positive pertussis. Design. Randomized, double-blind, placebo-controlled study. Setting. Community based. Subjects. All household contacts of 152 children with culture-positive pertussis who provided consent (n= 362). After withdrawals, there were 135 households with 310 contacts. Exclusions included pregnancy, age <6 months, already receiving an erythromycin-containing antibiotic, and erythromycin allergy. Interventions. Erythromycin estolate (40 mg/kg/day in 3 divided doses; maximum dose 1 g) or placebo for 10 days. Nasopharyngeal cultures, pertussis antibodies, and clinical symptoms were assessed before and after treatment. Primary Outcome. Measure efficacy of erythromycin estolate chemoprophylaxis calculated by the proportion of households in each group with a member who developed a nasopharyngeal culture positive forBordetella pertussis. Results. There was no difference in the development of respiratory tract symptoms compatible with a case definition of pertussis in the erythromycin- and placebo-treated groups. There were 20 households with secondary culture-positive cases of pertussis; 4 households in the erythromycin-treated group and 15 in the placebo-treated group (efficacy of erythromycin chemoprophylaxis for bacterial eradication 67.5% [95% confidence interval: 7.6–88.7]). However, medication-associated adverse reactions were reported by 34.0% of erythromycin and 15.7% of placebo recipients. Conclusions. Under the conditions of this study, erythromycin estolate prevented culture-positive pertussis in household contacts of patients with pertussis but did not prevent clinical pertussis.

Juvenile diabetes mellitus, optic atrophy, sensory nerve deafness, and diabetes insipidus—a syndrome

Four patients with diabetes mellitus, optic atrophy, and high-frequency neurosensory hearing loss, two of whom also had diabetes insipidus, are described. The frequency of this syndrome among patients with juvenile diabetes appears to be between 1/148 and 1/175. Because of the progressive nature of the disabilities and the autosomal recessive mode of inheritance, careful monitoring of all juvenile diabetic patients for other signs of the syndrome is warranted.

Lipopolysaccharide-Binding Protein- and CD14-Dependent Activation of Mitogen-Activated Protein Kinase p38 by Lipopolysaccharide in Human Neutrophils Is Associated with Priming of Respiratory Burst

ABSTRACT Neutrophil (PMN) functions can be primed for greatly increased oxidative radical release by exposure to certain agents such as lipopolysaccharide (LPS). Although a variety of signaling pathways involving both tyrosine kinases and mitogen-activated protein (MAP) kinases may be operative, the mechanisms of PMN priming are still not understood. We found that PMN priming was not achieved by treatment of cells with a very low concentration (5 ng/ml) of LPS unless additional “helper” factors were present in plasma (5%). Under these conditions, LPS induced tyrosine phosphorylation of a 38-kDa protein, which was coincident with the MAP kinase p38 action in this situation. LPS-mediated activation of p38 in human PMNs was dependent on the presence of LPS binding protein from plasma and CD14 on the surfaces of the cells. Phosphorylation of p38 was highly correlated with LPS priming of a formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated PMN respiratory burst. Treatment of PMN with the p38-specific inhibitor SB203580 significantly attenuated the respiratory burst in cells primed by LPS and stimulated by fMLP. These results suggest that the LPS signaling pathway leading to p38 activation may be an important mechanism in regulation of PMN priming. The mediator(s) linking CD14 to p38 involves proteins that are functionally sensitive to genistein but insensitive to tyrphostin AG126 and to Src- and Syk-family kinase, protein kinase C, and phosphatidylinositol 3-kinase inhibitors. Elucidating this pathway will provide insight into possible regulation of PMN priming by LPS.

Clinical course of pertussis in immunized children

To describe the clinical course of Bordetella pertussis infection in a highly immunized childhood population, we studied prospectively endemic and epidemic pertussis in a metropolitan population with an immunization rate >90% during an 8-year period from 1987 through 1994. Patients with a possible diagnosis of pertussis were referred by family or emergency room physicians for nasopharyngeal culture. Patients with a culture positive for B. pertussis were contacted by a nurse who completed a detailed questionnaire for the index case and all family members. Repeat home visits were made each week for 4 weeks. Of the 189 patients with pertussis who were evaluated 103 subjects were <5 years of age. Congestion predated the onset of cough by up to 1 week in 35 (34%) cases. Seventy (68%) subjects <5 years of age developed a paroxysmal cough within the first week of their illness. Ninety-one (88%) cases <5 years old had a persistent paroxysmal cough for >21 days. Coughing in this group lasted from 16 to 91 days (median 48). Erythromycin therapy appeared to shorten the duration of cough; however, patients were not randomized to receive erythromycin at a specific time. Despite adequate immunization some children develop pertussis. The clinical course in these patients is milder than in unimmunized subjects. Nevertheless the symptomatology in these children should still be readily identified by most physicians using classical clinical criteria of pertussis

Deficient Priming Activity of Newborn Cord Blood–Derived Polymorphonuclear Neutrophilic Granulocytes with Lipopolysaccharide and Tumor Necrosis Factor-α Triggered with Formyl-Methionyl-Leucyl-Phenylalanine

ABSTRACT: Newborn infants are more susceptible to bacterial infections than adults. This susceptibility has been attributed to defects in humoral and cellular activity. Host cellular activity can be modified by factors produced by bacteria or the host in response to infection. We assessed the effect of two factors associated with gram-negative bacterial infection, lipopolysaccharide (LPS) and TNF-α, on polymorphonuclear neutrophilic granulocytes (PMN) obtained from adult or newborns (umbilical cord blood). PMN were primed in vitro with LPS (10 μg/L) or TNF-α (10−9 M) for 45 min and then assessed, using a chemiluminescence (CL) assay as an indicator of oxidative radical production with formyl-methionyl-leucyl-phenylalanine as the trigger for CL initiation. CL activity of unprimed PMN was similar for adults and newborns (13.3 and 13.7 CL units, respectively). After priming with LPS, CL activity was increased to 43.4 CL units for PMN from adults but to only 17.6 CL units for PMN from newborns (p < 0.001, adults versus newborn increment). Priming of PMN with LPS was most effective when autologous plasma was present. Using FITC-conjugated LPS and a flow cytometry assay, we could demonstrate no difference between the binding affinity of LPS for adult and newborn PMN. However, formyl-methionyl-Ieucyl-phenylalanine binding studies indicated that adult PMN had a higher number of binding sites. TNF-α priming of new born PMN was also ineffective. Adult PMN increased CL activity by 3.9-fold when primed with TNF-α, whereas newborn PMN increased by only 1.75-fold (p < 0.005). This priming deficiency was not attributable to TNF-α receptors because phycoerythrin-conjugated TNF-α was associated with PMN from adults and newborns equally. Thus, PMN from newborns are not primed effectively in vitro with LPS or TNF-α. This defect may contribute to neonatal susceptibility to bacterial infection.