Jean Longtin

Impact of the Type of Diagnostic Assay on Clostridium difficile Infection and Complication Rates in a Mandatory Reporting Program

BACKGROUND Most Clostridium difficile infection (CDI) surveillance programs neither specify the diagnostic method to be used nor stratify rates accordingly. We assessed the difference in healthcare-associated CDI (HA-CDI) incidence and complication rates obtained by 2 validated diagnostic methods. METHODS This was a prospective cohort study of patients for whom a C. difficile test was ordered between 1 August 2010 and 31 July 2011. All specimens were tested in parallel by a commercial polymerase chain reaction (PCR) assay targeting toxin B gene tcdB, and a 3-step algorithm detecting glutamate dehydrogenase and toxins A and B by enzyme immunoassay and cell culture cytotoxicity assay (EIA/CCA). CDI incidence rate ratios were calculated using univariate Poisson regression. RESULTS A total of 1321 stool samples were tested during a period totaling 95 750 patient-days. Eighty-five HA-CDI cases were detected by PCR and 56 cases by EIA/CCA (P = .01). The overall incidence rate was 8.9 per 10 000 patient-days (95% confidence interval [CI], 7.1-10.9) by PCR and 5.8 per 10 000 patient-days (95% CI, 4.4-7.4) by EIA/CCA (P = .01). The incidence rate ratio comparing PCR and EIA/CCA was 1.52 (95% CI, 1.08-2.13; P = .015). Overall complication rate was 27% (23/85) when CDI was diagnosed by PCR and 39% (22/56) by EIA/CCA (P = .16). Cases detected by PCR only were less likely to develop a complication of CDI compared with cases detected by both PCR and EIA/CCA (3% vs 39%, respectively; P < .001). CONCLUSIONS Performing PCR instead of EIA/CCA is associated with a >50% increase in the CDI incidence rate. Standardization of diagnostic methods may be indicated to improve interhospital comparison.

Human bocavirus infections in hospitalized children and adults.

The pathogenic role of this virus in infected children is unclear.

MupB, a New High-Level Mupirocin Resistance Mechanism in Staphylococcus aureus

ABSTRACT Mupirocin is a topical antibiotic used for the treatment of skin infections and the eradication of methicillin-resistant Staphylococcus aureus carriage. It inhibits bacterial protein synthesis by interfering with isoleucyl-tRNA synthetase activity. High-level mupirocin resistance (MIC of ≥512 μg/ml) is mediated by the expression of mupA (ileS2), which encodes an alternate isoleucyl-tRNA synthetase. In this study, we describe high-level mupirocin resistance mediated by a novel locus, mupB. The mupB gene (3,102 bp) shares 65.5% sequence identity with mupA but only 45.5% identity with ileS. The deduced MupB protein shares 58.1% identity (72.3% similarity) and 25.4% identity (41.8% similarity) with MupA and IleS, respectively. Despite this limited homology, MupB contains conserved motifs found in class I tRNA synthetases. Attempts to transfer high-level mupirocin resistance via conjugation or transformation (using plasmid extracts from an mupB-containing strain) were unsuccessful. However, by cloning the mupB gene into a shuttle vector, it was possible to transfer the resistance phenotype to susceptible S. aureus by electroporation, proving that mupB was responsible for the high-level mupirocin resistance. Further studies need to be done to determine the prevalence of mupB and to understand risk factors and outcomes associated with resistance mediated by this gene.

Distribution of Antiseptic Resistance Genes qacA, qacB, and smr in Methicillin-Resistant Staphylococcus aureus Isolated in Toronto, Canada, from 2005 to 2009

ABSTRACT Decreased susceptibility to chlorhexidine gluconate (CHDN) in methicillin-resistant Staphylococcus aureus (MRSA) is associated with the qacA, qacB, and smr genes, encoding efflux pumps. A total of 334 MRSA isolates were collected from two Canadian intensive care units between 2005 and 2009. We identified the qacAB genes in 7 strains (2%; 2 qacA genes and 5 qacB genes) and the smr gene in 23 (7%) strains. CHDN minimal bactericidal concentrations were slightly higher for strains harboring smr genes.

Novel Mutations in a Patient Isolate of Streptococcus agalactiae with Reduced Penicillin Susceptibility Emerging after Long-Term Oral Suppressive Therapy

ABSTRACT Penicillin nonsusceptibility has been demonstrated in group B streptococci (GBS), but there is limited information regarding mechanisms of resistance. We report a case of GBS with reduced susceptibility to penicillin emerging after long-term suppressive oral penicillin therapy for a prosthetic joint infection. Molecular characterization of the isolate before and after long-term penicillin therapy revealed 5 mutations in the ligand-binding regions of PBP1a, -2a, and -2x not previously reported in GBS.

Correlation between Clostridium difficile Bacterial Load, Commercial Real-Time PCR Cycle Thresholds, and Results of Diagnostic Tests Based on Enzyme Immunoassay and Cell Culture Cytotoxicity Assay

ABSTRACT The impact of Clostridium difficile fecal loads on diagnostic test results is poorly understood, but it may have clinical importance. In this study, we investigated the relationship between C. difficile fecal load and the results of four assays: a glutamate dehydrogenase (GDH) enzyme immunoassay (EIA), a toxin A/B antigen EIA (ToxAB), a cell culture cytotoxicity assay (CCA), and PCR targeting the tcdB gene. We also compared the PCR cycle threshold (CT ) with the results of quantitative culture using Spearmans rank correlation coefficient. Finally, we sequenced the genomes of 24 strains with different detection profiles. A total of 203 clinical samples harboring toxigenic C. difficile were analyzed and sorted into one of four groups: 17 PCR+ (group 1), 37 PCR+ GDH+ (group 2), 24 PCR+ GDH+ CCA+ (group 3), and 125 PCR+ GDH+ ToxAB+ (group 4). The overall median fecal load in log10 CFU/g was 6.67 (interquartile range [IQR], 5.57 to 7.54). The median fecal bacterial load of groups 1, 2, 3, and 4 were 4.15 (IQR, 3.00 to 4.98), 5.74 (IQR, 4.75 to 6.16), 6.20 (IQR, 5.23 to 6.80), and 7.08 (IQR, 6.35 to 7.83), respectively. Group 1 samples had lower fecal loads than those from each of the other groups (P < 0.001). Group 2 samples had lower fecal loads than those from groups 3 and 4 (P < 0.001). There was a significant correlation between PCR CT and fecal loads (ρ = −0.697; P < 0.001). NAP1 strains were associated with the detection of toxins by EIA or CCA (P = 0.041). This study demonstrates an association between C. difficile fecal load and the results of routinely used diagnostic tests.

Rhinovirus outbreaks in long-term care facilities, Ontario, Canada.

Diagnostic difficulties may have led to underestimation of rhinovirus infections in long-term care facilities. Using surveillance data, we found that rhinovirus caused 59% (174/297) of respiratory outbreaks in these facilities during 6 months in 2009. Disease was sometimes severe. Molecular diagnostic testing can differentiate these outbreaks from other infections such as influenza.

Neuraminidase-inhibitor resistance testing for pandemic influenza A (H1N1) 2009 in Ontario, Canada

BACKGROUND Oseltamivir resistance-associated H275Y mutation in the neuraminidase (NA) gene of pandemic influenza A (H1N1) 2009 was occasionally reported worldwide during the 2009-2010 influenza season. A significant proportion of those were found in immunocompromised or severely ill persons. This phenomenon remains infrequent and clear recommendations for resistance testing are lacking. OBJECTIVES Present the suggested clinical selection criteria for antiviral susceptibility testing for influenza in Canada and to describe the Ontarian experience during the 2009-2010 influenza season. STUDY DESIGN Using a defined algorithm, we prospectively screened for OsR with pyrosequencing and phenotypic testing during the 2009-2010 influenza season. Zanamivir resistance was screened using phenotypic and sequencing technique on selected occasions. Clinical data was gathered for the resistant cases. RESULTS A total of 804 clinical H1N1 (2009) positive samples from Ontario were screened for oseltamivir resistance between June 2009 and March 2010. We identified oseltamivir resistance in 5 (0.6%) distinct patients aged 9-62 years. All the resistant strains bore the H275Y mutation. Susceptibility to zanamivir was maintained in all of them. Three patients harboring oseltamivir resistant strain were intensive care unit patients and four were immunocompromised. All were tested for susceptibility because of a repeat positive result for influenza A PCR. CONCLUSION Oseltamivir resistance was not frequent during the 2009-2010 influenza season but was identified with a systematic and prospective approach to resistance testing. In order to be as sensitive as possible in the detection of those few cases, we report the suggested indications for antiviral susceptibility testing in Canada.

SEVERE HUMAN RHINOVIRUS OUTBREAK ASSOCIATED WITH FATALITIES IN A LONG-TERM CARE FACILITY IN ONTARIO, CANADA

1. Yamaya M, Yanai M, Ohrui T et al. Interventions to prevent pneumonia among older adults. J Am Geriatr Soc 2001;49:85–90. 2. Matsumura T, Arai M, Yonemitsu Y et al. The traditional Japanese medicine Rikkunshito increases the plasma level of ghrelin in humans and mice. J Gastroenterol 2010;45:300–307. 3. De Vriese C, Perret J, Delporte C. Focus on the shortand long-term effects of ghrelin on energy homeostasis. Nutrition 2010;26:579–584.

Cooperative Recognition of Internationally Disseminated Ceftriaxone-Resistant Neisseriagonorrhoeae Strain

Ceftriaxone remains a first-line treatment for patients infected by Neisseria gonorrhoeae in most settings. We investigated the possible spread of a ceftriaxone-resistant FC428 N. gonorrhoeae clone in Japan after recent isolation of similar strains in Denmark (GK124) and Canada (47707). We report 2 instances of the FC428 clone in Australia in heterosexual men traveling from Asia. Our bioinformatic analyses included core single-nucleotide variation phylogeny and in silico molecular typing; phylogenetic analysis showed close genetic relatedness among all 5 isolates. Results showed multilocus sequence type 1903; N. gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR) 233; and harboring of mosaic penA allele encoding alterations A311V and T483S (penA-60.001), associated with ceftriaxone resistance. Our results provide further evidence of international transmission of ceftriaxone-resistant N. gonorrhoeae. We recommend increasing awareness of international spread of this drug-resistant strain, strengthening surveillance to include identifying treatment failures and contacts, and strengthening international sharing of data.