Céline Laferrière

Sensitivities of Antigen Detection and PCR Assays Greatly Increased Compared to That of the Standard Culture Method for Screening for Group B Streptococcus Carriage in Pregnant Women

ABSTRACT Group B streptococcus (GBS) is a major cause of serious infections in neonates. The 2002 revised guidelines of the Centers for Disease Control and Prevention (CDC) for the prevention of perinatal GBS disease recommend that all pregnant women be screened for GBS carriage at between 35 and 37 weeks of gestation and that intrapartum antibiotic prophylaxis be given to carriers. We studied the performances of four different GBS detection assays in the context of antenatal screening. Between May and August 2004, the 605 vaginorectal swab specimens received at our bacteriology laboratory for GBS antenatal detection were tested by the four assays. The standard culture method was done according to the CDC recommendations. The three experimental assays performed with the growth from the selective enrichment (LIM) broth (Todd-Hewitt broth with 15 μg/ml nalidixic acid and 10 μg/ml colistin) after overnight incubation were a GBS antigen detection assay (PathoDx) and two PCR assays (for cfb and scpB). The most accurate assay was the scpB PCR (sensitivity, 99.6%; specificity, 100%), followed by the cfb PCR (sensitivity, 75.3%; specificity, 100%), GBS antigen detection (sensitivity, 57.3%; specificity, 99.5%), and standard culture (sensitivity, 42.3%; specificity, 100%). The GBS antigen detection assay was found to be more sensitive than the standard culture method, and moreover, the assay has a low cost and is easy to perform in all obstetrical centers which have access to the most basic of diagnostic microbiology services. We believe that antigen detection on incubated LIM broth should replace the standard culture method for screening for GBS carriage at 35 to 37 weeks of gestation. The impact of the greater sensitivities of PCR assays on the diminution of neonatal GBS infections remains to be demonstrated.

Bacteriology of Amniotic Fluid in Women With Suspected Cervical Insufficiency

OBJECTIVE To determine the prevalence of mid-trimester microbial invasion of the amniotic cavity (MIAC) in women with suspected cervical insufficiency. METHODS A prospective observational cohort study was performed in women with suspected cervical insufficiency and visible fetal membranes who were undergoing amniocentesis to rule out MIAC between 16 and 26 weeks of gestation. Women with preterm premature rupture of membranes, regular uterine contractions, or who had a cervical cerclage were excluded. Gram staining of amniotic fluid, glucose and lactate dehydrogenase (LDH) levels in amniotic fluid, and aerobic and anaerobic amniotic fluid cultures were performed, along with polymerase chain reaction (PCR) for the detection of Ureaplasma and Mycoplasma species. RESULTS Fifteen women with a mean gestational age of 22.6 +/- 2.3 weeks were included in the study. The diagnosis of MIAC was confirmed in 47% (7/15), of whom 20% (3/15) were infected with more than one bacterial strain and 33% (5/15) with Ureaplasma species. According to receiver-operator curve analyses, amniotic fluid levels of glucose were associated with MIAC (P = 0.02), but not amniotic fluid LDH (P = 0.25). CONCLUSION MIAC is present in approximately one half of women with suspected cervical insufficiency and visible fetal membranes at speculum examination.

Pediatric injuries from needles discarded in the community: epidemiology and risk of seroconversion.

OBJECTIVES. Although anxiety exists concerning the perceived risk of transmission of bloodborne viruses after community-acquired needlestick injuries, seroconversion seems to be rare. The objectives of this study were to describe the epidemiology of pediatric community-acquired needlestick injuries and to estimate the risk of seroconversion for HIV, hepatitis B virus, and hepatitis C virus in these events. METHODS. The study population included all of the children presenting with community-acquired needlestick injuries to the Montreal Childrens Hospital between 1988 and 2006 and to Hôpital Sainte-Justine between 1995 and 2006. Data were collected prospectively at Hôpital Sainte-Justine from 2001 to 2006. All of the other data were reviewed retrospectively by using a standardized case report form. RESULTS. A total of 274 patients were identified over a period of 19 years. Mean age was 7.9 ± 3.4 years. A total of 176 (64.2%) were boys. Most injuries occurred in streets (29.2%) or parks (24.1%), and 64.6% of children purposely picked up the needle. Only 36 patients (13.1%) noted blood on the device. Among the 230 patients not known to be immune for hepatitis B virus, 189 (82.2%) received hepatitis B immunoglobulin, and 213 (92.6%) received hepatitis B virus vaccine. Prophylactic antiretroviral therapy was offered beginning in 1997. Of the 210 patients who presented thereafter, 82 (39.0%) received chemoprophylaxis, of whom 69 (84.1%) completed a 4-week course of therapy. The use of a protease inhibitor was not associated with a significantly higher risk of adverse effects or early discontinuation of therapy. At 6 months, 189 were tested for HIV, 167 for hepatitis B virus, and 159 for hepatitis C virus. There were no seroconversions. CONCLUSIONS. We observed no seroconversions in 274 pediatric community-acquired needlestick injuries, thereby confirming that the risk of transmission of bloodborne viruses in these events is very low.

Hospital-acquired phaeohyphomycosis due to Exserohilum rostratum in a child with leukemia

The present study describes a case of cutaneous phaeohyphomycosis caused by Exserohilum rostratum in a child undergoing treatment for leukemia. The infection was possibly due to contaminated intravenous dressings and was successfully treated with surgical excision combined with liposomal amphotericin B. Consequently, new infection control policies have been implemented at CHU Sainte-Justine (Montreal, Quebec).

Post-Outbreak Investigation of Pseudomonas aeruginosa Faucet Contamination by Quantitative Polymerase Chain Reaction and Environmental Factors Affecting Positivity

OBJECTIVE To perform a post-outbreak prospective study of the Pseudomonas aeruginosa contamination at the faucets (water, aerator and drain) by culture and quantitative polymerase chain reaction (qPCR) and to assess environmental factors influencing occurrence SETTING A 450-bed pediatric university hospital in Montreal, Canada METHODS Water, aerator swab, and drain swab samples were collected from faucets and analyzed by culture and qPCR for the post-outbreak investigation. Water microbial and physicochemical parameters were measured, and a detailed characterization of the sink environmental and design parameters was performed. RESULTS The outbreak genotyping investigation identified drains and aerators as the source of infection. The implementation of corrective measures was effective, but post-outbreak sampling using qPCR revealed 50% positivity for P. aeruginosa remaining in the water compared with 7% by culture. P. aeruginosa was recovered in the water, the aerator, and the drain in 21% of sinks. Drain alignment vs the faucet and water microbial quality were significant factors associated with water positivity, whereas P. aeruginosa load in the water was an average of 2 log higher for faucets with a positive aerator. CONCLUSIONS P. aeruginosa contamination in various components of sink environments was still detected several years after the resolution of an outbreak in a pediatric university hospital. Although contamination is often not detectable in water samples by culture, P. aeruginosa is present and can recover its culturability under favorable conditions. The importance of having clear maintenance protocols for water systems, including the drainage components, is highlighted.

Perinatal Listeriosis: Canada’s 2008 Outbreaks

BACKGROUND Listeriosis is one of the most severe foodborne illnesses worldwide. Most infections with Listeria are sporadic, but outbreaks do occur. Pregnant women exposed to this organism are at increased risk of chorioamnionitis, preterm labour, prematurity and intrauterine fetal demise. Severe neonatal infection can also occur. CASES Two recent outbreaks in Canada prompted a reassessment of the prevalence and the perinatal impact of this disease. We describe here three cases of perinatal listeriosis. The aim of our report is to demonstrate the variable clinical presentations and to emphasize the difficulty in diagnosing perinatal listeriosis. CONCLUSION Perinatal listeriosis is a severe disease with many possible clinical presentations. Clinical diagnosis may be difficult, so clinicians must maintain a high index of suspicion.

Impact of Electronic Faucets and Water Quality on the Occurrence of Pseudomonas aeruginosa in Water: A Multi-Hospital Study

OBJECTIVE To compare Pseudomonas aeruginosa prevalence in electronic and manual faucets and assess the influence of connecting pipes and water quality. SETTING Faucets in 4 healthcare centers in Quebec, Canada. METHODS Water samples from 105 electronic, 90 manual, and 14 foot-operated faucets were analyzed for P. aeruginosa by culture and enzymatic detection, and swab samples from drains and aerators were analyzed by culture. Copper and residual chlorine concentrations, temperature, and flow rate were measured. P. aeruginosa concentrations were analyzed in 4 consecutive volumes of cold water and a laboratory study was conducted on copper pipes and flexible hoses. RESULTS P. aeruginosa contamination was found in drains more frequently (51%) than in aerators (1%) or water (culture: 4%, enzyme detection: 16%). Prevalence in water samples was comparable between manual (14%) and 2 types of electronic faucets (16%) while higher for foot-operated faucets (29%). However, type 2 electronic faucets were more often contaminated (31%) than type 1 (14%), suggesting that faucet architecture and mitigated volume (30 mL vs 10 mL) influence P. aeruginosa growth. Concentrations were 100 times higher in the first 250 mL than after flushing. Flexible hoses were more favorable to P. aeruginosa growth than copper and a temperature of 40°C led to higher counts. CONCLUSIONS The types of faucets and connecting pipes, flow rate, and water quality are important parameters influencing the prevalence and the concentrations of P. aeruginosa in faucets. High concentrations of P. aeruginosa in the first 250 mL suggest increased risk of exposure when using the first flush.

Molecular Epidemiology of a Vancomycin-Intermediate Heteroresistant Staphylococcus epidermidis Outbreak in a Neonatal Intensive Care Unit

ABSTRACT Coagulase-negative staphylococci (CoNS) have become the leading cause of bloodstream infections (BSIs) in intensive care units (ICUs), particularly in premature neonates. Vancomycin-intermediate heteroresistant CoNS (hVICoNS) have been identified as sources of BSIs worldwide, and their potential to emerge as significant pathogens in the neonatal ICU (NICU) remains uncertain. This study describes the molecular epidemiology of an outbreak of vancomycin-heteroresistant (hV) Staphylococcus epidermidis central-line-associated BSI (CLABSI) in a single tertiary care NICU and compares it to a second tertiary care NICU that had not been associated with an outbreak. Between November 2009 and April 2014, 119 S. epidermidis CLABSIs were identified in two tertiary care NICUs in Quebec, Canada. Decreased vancomycin susceptibility was identified in about 88% of all collected strains using Etest methods. However, discrepancies were found according to the Etest and population analysis profiling–area under the concentration-time curve (PAP-AUC) methods used. All strains were susceptible to linezolid, and a few isolates were nonsusceptible to daptomycin. Great genetic diversity was observed within the collection, with 31 pulsed-field gel electrophoresis (PFGE) patterns identified. The outbreak strains were all determined to be heteroresistant to vancomycin and were polyclonal. The study identified two major clones, PFGE patterns E and G, which were found in both NICUs across the 5-year study period. This suggests the persistence of highly successful clones that are well adapted to the hospital environment. hV S. epidermidis seems more common than currently realized in the NICU, and certain hV S. epidermidis clones can become endemic to the NICU. The reservoirs for these clones remain unknown at this time, and identification of the reservoirs is needed to better understand the impact of hV S. epidermidis in the NICU and to inform infection prevention strategies. In addition, there is a need to investigate and validate hV determination protocols for different species of CoNS.

Pharmacokinetics and pharmacodynamics of oral cephalexin in children with osteoarticular infections.

Background: Osteoarticular infections lead to significant morbidity in children. Cephalexin has in vitro activity against methicillin-susceptible Staphylococcus aureus, a predominant pathogen in osteoarticular infection. However, cephalexin pharmacokinetics (PK) and pharmacodynamics (PD) are poorly described in children. This study described cephalexin PK in children treated for osteoarticular infection and assessed the proportion of children achieving surrogate PK/PD target for efficacy in methicillin-susceptible S. aureus infection. Methods: Children with osteoarticular infection, 1 to 18 years of age, were eligible for this study if they were receiving oral cephalexin per standard of care. PK plasma samples were collected at specified times after multiple doses. PK parameters were estimated using noncompartmental analysis. PK/PD target for efficacy was calculated using the child’s PK parameters, minimum inhibitory concentration (MIC) of the isolate when available and previously described MIC of 2 and 4 mg/L. Results: Twelve children were enrolled and PK profiles were obtained from 11 of them. Median age was 7 years, and median cephalexin dose was 40 mg/kg/dose every 8 hours. Median apparent oral clearance, apparent oral volume of distribution and elimination half-life (T1/2) were 0.29 L/h/kg, 0.44 L/kg and 1.1 h, respectively. Time above MIC (T>MIC) was greater than 40% of the dosing interval in 100%, 90% and 80% of the children when MICs were 0.25, 2 and 4 mg/L, respectively. Conclusions: Oral cephalexin achieved optimal plasma exposure and was well tolerated in children with osteoarticular infection. Correlation between osteoarticular infection clinical outcome and PK/PD parameters needs further evaluation.

Invasive group A Streptococcus disease in French-Canadian children is not associated with a defect in MyD88/IRAK4-pathway

BackgroundBeta-hemolytic Group A Streptococcus invasive disease (iGASd) has been subject to intense research since its re-emergence in the late 1980s. In Quebec, an increase in the number of severe iGASd cases has recently been observed. Because of the inter-individual variability in the severity of iGASd, a hereditary predisposition to invasive disease can be suspected. Given that iGASd occurs in MyD88- and IRAK4-deficient patients, although rarely, the increasing frequency of iGASd in the population of French-Canadian children may be associated with a deficiency in the host’s innate immune response.MethodsIn this report, we assessed the influence of: (i) bacterial genotype and virulence factors, (ii) immune-cellular features, and (iii) Myd88/IRAK4-dependent response to GAS in vitro on the susceptibility to iGASd in a paediatric cohort of 16 children: 11 French-Canadian and 5 from diverse origin.FindingsGAS virulence factors and genotype are not implicated in the susceptibility toward iGASd, and cellular and MyD88/IRAK4 deficiencies are excluded in our patients.ConclusionsAlthough it has been shown that the MyD88/IRAK4-dependent signal is involved in the response to invasive GAS, our data indicates that a MyD88/IRAK4-mediated signalling defect is not the main factor responsible for the susceptibility to severe iGASd in a paediatric population from the province of Quebec.