Contemporary Microbiology and Antimicrobial Treatment of Complicated Appendicitis: The Value of a Short-term Study.

BACKGROUND: Antimicrobial stewardship interventions to curtail the use of third-generation cephalosporins and antipseudomonal penicillins for the treatment of complicated appendicitis in children are challenging given the tendency to treat complicated disease with broad-spectrum antimicrobials. Reasons for this are unclear, but there is a paucity of contemporary microbiologic data associated with the child presenting with either acute perforated or gangrenous appendicitis. This study aimed to justify the appropriateness of an empiric regimen consisting of ampicillin, tobramycin/gentamicin plus metronidazole and to analyze duration of postoperative therapy. METHODS: We conducted a retrospective cohort study from February 1, 2017, to October 31, 2018, in children who underwent appendectomy or interventional radiologic drainage for primary complicated appendicitis. The primary outcome was the proportion of patients who had a pathogen isolated from peritoneal fluid culture that was not susceptible to the recommended empiric therapy. The secondary outcomes were the total duration of antimicrobial therapy and the proportion of patients with a postoperative infectious complication within 30 days after intervention. RESULTS: Of 425 children with primary acute appendicitis, 158 (37%) had complicated appendicitis at presentation. Culture was performed in 53 (40%) of the 133 who underwent a surgical or interventional radiologic intervention. The group with peritoneal cultures was more likely to present with longer symptom duration before admission [3 (interquartile range, 2-5) vs 2 (interquartile range, 1-2) days; P < 0.001] and with purulent peritonitis [47% (25/53) vs 13% (10/80); P < 0.001]. The most common pathogens isolated were anaerobes (81%), Escherichia coli (74%) and Streptococcus anginosus group (62%). Only 4% of isolated bacteria were resistant to empiric therapy. Postoperative infectious complications were documented in 23 (17%) patients and were not associated with the presence of a resistant pathogen or the choice of antimicrobial agents but with more severe disease and higher C-reactive protein values (303 vs 83 mg/L; P=0.03) at presentation. CONCLUSIONS: In a cohort of previously healthy children presenting with complicated appendicitis requiring surgical drainage, the most common bacteria from peritoneal cultures continue to be S. anginosus, aminoglycoside-susceptible Gram-negative bacilli and anaerobes. In an attempt to reduce extended-spectrum cephalosporin use, these data were useful in supporting the use of metronidazole with ampicillin and an aminoglycoside, rather than third-generation cephalosporins.

Clostridium difficile: Investigating Transmission Patterns Between Infected and Colonized Patients Using Whole Genome Sequencing.

Background: Whole genome sequencing (WGS) studies can enhance our understanding of the role of patients with asymptomatic Clostridium difficile colonization in transmission. Methods: Isolates obtained from patients with Clostridium difficile infection (CDI) and colonization identified in a study conducted during 2006-2007 at 6 Canadian hospitals underwent typing by pulsed-field gel electrophoresis, multilocus sequence typing, and WGS. Isolates from incident CDI cases not in the initial study were also sequenced where possible. Ward movement and typing data were combined to identify plausible donors for each CDI case, as defined by shared time and space within predefined limits. Proportions of plausible donors for CDI cases that were colonized, infected, or both were examined. Results: Five hundred fifty-four isolates were sequenced successfully, 353 from colonized patients and 201 from CDI cases. The NAP1/027/ST1 strain was the most common strain, found in 124 (62%) of infected and 92 (26%) of colonized patients. A donor with a plausible ward link was found for 81 CDI cases (40%) using WGS with a threshold of ≤2 single nucleotide polymorphisms to determine relatedness. Sixty-five (32%) CDI cases could be linked to both infected and colonized donors. Exclusive linkages to infected and colonized donors were found for 28 (14%) and 12 (6%) CDI cases, respectively. Conclusions: Colonized patients contribute to transmission, but CDI cases are more likely linked to other infected patients than colonized patients in this cohort with high rates of the NAP1/027/ST1 strain, highlighting the importance of local prevalence of virulent strains in determining transmission dynamics.

Incidental post-partum isolation of Brucella melitensis in an asymptomatic woman.

A 25-year-old Somali-born female was admitted to the hospital in active labour. Following post-partum hemorrhage, Brucella melitensis grew from a blood culture and the placenta. Identification and relatedness were determined through reverse transcriptase polymerase chain reaction (RT-PCR), single nucleotide polymorphism (SNP), and whole genome sequencing. The patient and her child were completely asymptomatic at their initial assessment.

Une femme d'origine somalienne de 25 ans a été hospitalisée en travail actif. Après une hémorragie postpartum, le Brucella melitensis s'est développé dans une hémoculture et dans le placenta. La réaction de transcriptase inverse et d'amplification en chaîne de la polymérase (RT-PCR), le polymorphisme du nucléotide simple (SNP) et le séquençage du génome entier ont permis d'identifier la bactérie et d'établir sa parenté génétique. La patiente et son enfant étaient complètement asymptomatiques à l'évaluation initiale.

Direct molecular detection of amoxicillin-susceptible E. coli in urine samples from children with suspected urinary tract infection: A potential tool to improve antibiotic stewardship and patient care.

Background: Rapid detection of amoxicillin-susceptible Escherichia coli (ASEC) urinary tract infections (UTIs) could have a significant impact on patient care and improve antibiotic stewardship. This is especially true for infants and children, for whom antibiotic choices are more limited than for adults. Methods: A real-time polymerase chain reaction (PCR) uniplex panel for detection of ASEC using PCR assays for E. coli and five resistance genes (bla TEM, bla SHV, bla OXA, bla CTX-M, and bla CMY) and an internal control was designed. PCR was then performed directly on pediatric urine samples using an inhibitor-resistant DNA polymerase. The main outcome measure was the performance of the PCR panel (sensitivity, specificity, positive predictive value [PPV], negative predictive value [NPV], accuracy) for the detection of ASEC. ASEC samples were defined as those that were E. coli PCR positive and PCR negative for all five resistance genes. PCR results were compared with the reference standard for culture and susceptibility testing. Results: Two hundred and six urine samples with pyuria (>10 white blood cells/high power field) were tested with the PCR panel. Two samples showed PCR inhibition (1%). For ASEC detection, the PCR panel showed a sensitivity of 91.53% (95% CI 81.32% to 97.19%), specificity of 98.21% (95% CI 90.45% to 99.95%), PPV of 98.18% (95% CI 88.54% to 99.74%), NPV of 91.67% (95% CI 82.61% to 96.22%), and accuracy of 94.78% (95% CI 88.99% to 98.06%). Conclusions: This PCR method could potentially enable amoxicillin or ampicillin to be used in a greater proportion of children with E. coli UTIs, improving antibiotic stewardship.

Historique: La détection rapide des infections urinaires à Escherichia coli susceptibles à l'amoxicilline (ECSA) peut avoir des effets importants sur les soins aux patients et améliorer la gérance des antibiotiques. C'est particulièrement vrai chez les nourrissons et les enfants, pour qui les choix d'antibiotiques sont plus limités que pour les adultes. Méthodologie: Les chercheurs ont fait appel à un panel uniplex d'amplification en chaîne par polymérase (PCR) pour déceler l'ECSA au moyen d'épreuves PCR d'E. coli et de cinq gènes de résistance (bla TEM, bla SHV, bla OXA, bla CTX-M et bla CMY) et ont conçu un contrôle interne. Ils ont ensuite effectué la PCR directement sur les échantillons d'urine pédiatrique à l'aide d'une polymérase d'ADN résistante aux inhibiteurs. La principale mesure de résultat était l'exécution du panel de PCR (sensibilité, spécificité, valeur prédictive positive [VPP], valeur prédictive négative [VPN], précision) pour déceler l'ECSA. Les échantillons d'ECSA étaient définis comme ceux dont la PCR était positive à l'E. coli et négative aux cinq gènes de résistance. Les chercheurs ont comparé les résultats de la PCR aux normes de référence des tests de culture et susceptibilité. Résultats: Les chercheurs ont testé 206 échantillons d'urine pyurique (>10 globules blancs/champ à fort grossissement) avec le panel de PCR. Deux échantillons ont révélé une inhibition de la PCR (1 %). Pour déceler l'ECSA, le panel de PCR a révélé une sensibilité de 91,53 % (IC à 95 %, 81,32 % à 97,19 %), une spécificité de 98,21 % (IC à 95 %, 90,45 % à 99,95 %), une VPP de 98,18 % (IC à 95 %, 88,54 % à 99,74 %), une VPN de 91,67 % (IC à 95 %, 82,61 % à 96,22 %) et une précision de 94,78 % (IC à 95 %, 88,99 % à 98,06 %). Conclusions: Cette méthode de PCR pourrait permettre de prescrire de l'amoxicilline ou de l'ampicilline à une plus grande proportion d'enfants ayant une infection urinaire à E. coli, ce qui améliorera la gérance des antibiotiques.

A comparison of the Allplex™ bacterial and viral assays to conventional methods for detection of gastroenteritis agents.

OBJECTIVE: Molecular methods to detect diarrheal pathogens are increasingly being used in place of conventional methods. We compared a new multiplex real-time PCR assay for detection of both bacterial and viral gastroenteritis agents, the Allplex™ Gastrointestinal Panel Assays (AGPA), to conventional methods (stool culture for bacterial pathogens and electron microscopy (EM) for viral pathogens). RESULTS: Gastrointestinal viruses, in particular norovirus genogroup II viruses, were detected by the AGPA in a high number of specimens that were negative by EM. For bacterial pathogens, the AGPA was able to detect the organisms grown in culture with high sensitivity and additionally detected several types of E. coli, such as enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), and non-O157 Shiga toxin-producing E. coli (STEC), that could not be detected with conventional culture methods. Overall, the AGPA had a > 2-fold higher detection rate than the conventional methods, with 24/135 (17.8%) samples positive by conventional methods and 60/135 (44.4%) by AGPA. Thus, diarrhea pathogen detection rates increased substantially with the use of the AGPA as compared to conventional methods.

Outcomes in a nurse-led peripherally inserted central catheter program: a retrospective cohort study.

BACKGROUND: Peripherally inserted central catheters (PICCs) provide enormous benefit to patients. However, recent publications have highlighted relatively high PICC-associated complication rates. We report on patient and device outcomes from a nurse-led program. METHODS: We performed a retrospective analysis of a prospective cohort of consecutive patients undergoing PICC insertion at The Ottawa Hospital between Jan. 1, 2013 and Dec. 31, 2014. Of the 8314 BioFlo PASV PICCs inserted, we randomly selected a sample of 700 and obtained a complete data set for 656. We measured the cumulative incidence of major complications (catheter-related bloodstream infections and deep vein thrombosis) and use of a thrombolytic to alleviate occlusions. RESULTS: The total number of catheter days was 58 486, and the median dwell time 45 days. We observed 4 cases of catheter-related bloodstream infection (0.6% [95% CI 0.17%-1.55%]) (0.07/1000 catheter days). Ten patients (1.5% [95% CI 0.83%-2.78%]) (0.17/1000 catheter days) had catheter-related deep venous thrombosis. At least 1 dose of thrombolytic was required in 75 catheters (11.4% [95% CI 8.61%-13.39]), 31 (7.1%) of the 436 single-lumen catheters and 113 (25.7%) of the 440 lumina of dual-lumen catheters (p < 0.001). INTERPRETATION: We attribute our low rates of major complications to a nurse-led expert insertion team, standardized care and maintenance protocols, high insertion volumes, novel catheter material and continuous quality-improvement initiatives that are implemented and evaluated regularly. We conclude that the considerable benefits PICCs provide to patients are attained with a low risk of major complications.

Pneumocystis pneumonia outbreak among renal transplant recipients at a North American transplant center: Risk factors and implications for infection control.

BACKGROUND: Pneumocystis pneumonia is a severe opportunistic fungal infection. Outbreaks among renal transplant recipients have been reported in Europe and Japan, but never in North America. METHODS: We conducted a retrospective case-control study among adult renal transplant recipients at a Canadian center, using a 3:1 matching scheme. Ten cases and 30 controls were matched based on initial transplantation date, and all patients received prophylaxis with trimethoprim-sulfamethoxazole for 1 year posttransplantation. RESULTS: The median time between transplantation and infection was 10.2 years, and all patients survived. Compared with controls, case patients had statistically lower estimated glomerular filtration rate (29.3 mL/min vs 66.3 mL/min; P = .028) and lymphopenia (0.51 × 10(9)/L vs 1.25 × 10(9)/L; P = .002). Transmission mapping revealed significant overlap in the clinic and laboratory visits among case vs control patients (P = .0002). One hundred percent of patients (4 out of 4) successfully genotyped had the same strain of Pneumocystis jirovecii. CONCLUSIONS: Our study demonstrated an outbreak of pneumocystis more than 10 years following initial transplantation, despite using recommended initial prophylaxis. We identified low estimated glomerular filtration rate and lymphopenia as risk factors for infection. Overlapping ambulatory care visits were identified as important potential sources of infection transmission, suggesting that institutions should re-evaluate policy and infrastructure strategies to interrupt transmission of respiratory pathogens.

Risk Factors for and Outcomes of Bacteremia Caused by Extended-Spectrum ß-Lactamase-Producing Escherichia coli and Klebsiella Species at a Canadian Tertiary Care Hospital.

BACKGROUND: Antimicrobial resistance due to production of extended-spectrum ß-lactamases by Escherichia coli and Klebsiella species (ESBL-EK) is concerning. Previous studies have shown that bacteremia due to ESBL-producing organisms is associated with increases in length of stay and/or mortality rate. Rates of infection by ESBL-EK vary worldwide, and regional differences in the prevalence of risk factors are likely. Few Canadian studies assessing risk factors for ESBL-EK infections or the outcomes of empiric therapy have been published. OBJECTIVES: To determine risk factors for and patient outcomes associated with ESBL-EK bacteremia. The appropriateness of empiric antibiotic therapy and the effect of inappropriate empiric therapy on these outcomes were also examined. METHODS: In a retrospective, 1:1 case-control study conducted in a tertiary care hospital between 2005 and 2010, data for 40 patients with ESBL-EK bacteremia were compared with data for 40 patients who had non-ESBL-EK bacteremia. RESULTS: Of all variables tested, only antibiotic use within the previous 3 months was found to be an independent risk factor for acquisition of ESBL-EK bacteremia (odds ratio 5.2, 95% confidence interval 1.6-16.9). A greater proportion of patients with non-ESBL-EK bacteremia received appropriate empiric therapy (88% [35/40] versus 15% [6/40], p < 0.001). Time to appropriate therapy was longer for those with ESBL-EK bacteremia (2.42 days versus 0.17 day, p < 0.001). Patient outcomes, including length of stay in hospital, admission to the intensive care unit (ICU), length of stay in the ICU (if applicable), and in-hospital mortality were not affected by the presence of ESBL-EK or the appropriateness of empiric therapy. CONCLUSIONS: Previous antibiotic use was a significant, independent risk factor for acquiring ESBL-EK. Thus, prior antibiotic use is an important consideration in the selection of empiric antibiotic therapy and should increase the concern for resistant pathogens.

CONTEXTE: La résistance aux antimicrobiens attribuable à la production de ß-lactamases à spectre étendu (BLSE) par les espèces Escherichia coli et Klebsiella est préoccupante. Des études antérieures ont démontré que les bactériémies causées par les organismes producteurs de BLSE sont associées à une augmentation de la durée du séjour à l'hôpital ou du taux de mortalité. Les taux d'infection par les espèces E. coli ou Klebsiella productrices de BLSE varient de par le monde et les différences régionales de la prévalence des facteurs de risque sont vraisemblables. Peu d'études canadiennes évaluant les facteurs de risque de ces infections ou les résultats cliniques des antibiothérapies empiriques ont été publiées. OBJECTIFS: Déterminer quels sont les facteurs de risque des bactériémies à E. coli ou à Klebsiella productrices de BLSE ainsi que les résultats cliniques associés à ces bactériémies. De plus, étudier la pertinence de l'antibiothérapie empirique ainsi que l'effet d'une antibiothérapie empirique inappropriée sur ces résultats. MÉTHODES: Au cours d'une étude cas-témoins rétrospective d'un ratio de 1 pour 1 et réalisée dans un centre hospitalier de soins tertiaires entre 2005 et 2010, les données de 40 patients présentant une bactériémie à E. coli ou Klebsiella productrices de BLSE ont été comparées aux données de patients présentant une bactériémie à organisme non producteur de BLSE. RÉSULTATS: Parmi toutes les variables évaluées, seul l'emploi d'une antibiothérapie dans les trois derniers mois s'est révélé être un facteur de risque indépendant du développement d'une bactériémie à E. coli ou Klebsiella productrices de BLSE (risque relatif approché de 5,2, intervalle de confiance à 95 % de 1,6­16,9). Une plus grande proportion de patients présentant une bactériémie autre que celles à E. coli ou Klebsiella productrices de BLSE ont reçu une antibiothérapie empirique appropriée (88 % [35/40] contre 15 % [6/40], p < 0,001). Le temps requis pour trouver le traitement adéquat était plus long pour ceux présentant une bactériémie à E. coli ou Klebsiella productrices de BLSE (2,42 jours contre 0,17 jour, p < 0,001). La présence des espèces E. coli ou Klebsiella productrices de BLSE de même que la pertinence d'une antibiothérapie empirique n'ont pas eu de répercussion sur les résultats cliniques, notamment la durée du séjour à l'hôpital, l'admission à l'unité des soins intensifs (USI), la durée du séjour à l'USI (le cas échéant) ainsi que le taux de mortalité en hôpital. CONCLUSIONS: L'emploi d'une antibiothérapie préalable représentait un important facteur de risque indépendant de la survenue des espèces E. coli ou Klebsiella productrices de BLSE. Ce faisant, l'emploi d'une antibiothérapie préalable représente un facteur important à considérer au moment du choix d'une antibiothérapie empirique et devrait rendre sensible aux dangers des pathogènes résistants.

Disseminated histoplasmosis associated with acquired hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a potentially life-threatening clinical syndrome caused by uncontrolled activation of lymphocytes and histiocytes resulting in high levels of cytokines. Acquired HLH occurs in autoimmune, inflammatory, infectious, and immunosuppressive disorders. Prompt identification and treatment of an underlying triggering cause improves clinical outcome.

Predictors of asymptomatic Clostridium difficile colonization on hospital admission.

BACKGROUND: Clostridium difficile (CD) is the leading cause of health care-associated diarrhea and can result in asymptomatic carriage. Rates of asymptomatic CD colonization on hospital admission range from 1.4%-21%. The objective of this study was to evaluate host and bacterial factors associated with colonization on admission. METHODS: The Consortium de recherche québécois sur le Clostridium difficile study provided data for analysis, including demographic information, known risk factors, and potential confounding factors, prospectively collected for 5,232 patients from 6 hospitals in Quebec and Ontario over 15 months from 2006-2007. Stool or rectal swabs were obtained for culture on admission. Pulsed-field gel electrophoresis was performed on the isolates. The presence of antibody against CD toxins A and B was measured. RESULTS: There were 212 (4.05%) patients colonized with CD on admission, and 5,020 patients were not colonized with CD. Multivariate logistic regression analysis showed that hospitalization within the last 12 months, use of corticosteroids, prior CD infection, and presence of antibody against toxin B were associated with colonization on admission. Of patients colonized on admission, 79.4% had non-NAP1, non-NAP2 strains. CONCLUSION: There are identifiable risk factors among asymptomatic CD carriers that could serve in their detection and provide a basis for targeted screening.

Antimicrobial susceptibility of clinical isolates of anaerobic bacteria in Ontario, 2010-2011.

The local epidemiology of antimicrobial susceptibility patterns in anaerobic bacteria is important in guiding the empiric treatment of infections. However, susceptibility data are very limited on anaerobic organisms, particularly among non-Bacteroides organisms. To determine susceptibility profiles of clinically-significant anaerobic bacteria in Ontario Canada, anaerobic isolates from sterile sites submitted to Public Health Ontario Laboratory (PHOL) for identification and susceptibility testing were included in this study. Using the E-test method, isolates were tested for various antimicrobials including, penicillin, cefoxitin, clindamycin, meropenem, piperacillin-tazobactam and metronidazole. The MIC results were interpreted based on guidelines published by Clinical and Laboratory Standards Institute. Of 2527 anaerobic isolates submitted to PHOL, 1412 were either from sterile sites or bronchial lavage, and underwent susceptibility testing. Among Bacteroides fragilis, 98.2%, 24.7%, 1.6%, and 1.2% were resistant to penicillin, clindamycin, piperacillin-tazobactam, and metronidazole, respectively. Clostridium perfringens was universally susceptible to penicillin, piperacillin-tazobactam, and meropenem, whereas 14.2% of other Clostridium spp. were resistant to penicillin. Among Gram-positive anaerobes, Actinomyces spp., Parvimonas micra and Propionibacterium spp. were universally susceptible to ß-lactams. Eggerthella spp., Collinsella spp., and Eubacterium spp. showed variable resistance to penicillin. Among Gram-negative anaerobes, Fusobacterium spp., Prevotella spp., and Veillonella spp. showed high resistance to penicillin but were universally susceptible to meropenem and piperacillin-tazobactam. The detection of metronidazole resistant B. fragilis is concerning as occurrence of these isolates is extremely rare. These data highlight the importance of ongoing surveillance to provide clinically relevant information to clinicians for empiric management of infections caused by anaerobic organisms.

Characterization of methicillin-resistant Staphylococcus aureus isolates from patients with persistent or recurrent bacteremia.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSI) are associated with considerable morbidity and mortality, especially with persistent (PB) or recurrent bacteremia (RB). OBJECTIVE: To determine the frequency of PB and RB in patients with MRSA BSI, and to characterize the isolates from these patients. METHODS: Surveillance for MRSA BSI was performed for one year in 13 Canadian hospitals. PB was defined as a positive blood culture that persisted for ≥7 days; RB was defined as the recurrence of a positive blood culture ≥14 days following a negative culture. Isolates were typed using pulsed-field gel electrophoresis (PFGE). Vancomycin susceptibility was determined using Etest. RESULTS: A total of 183 patients with MRSA BSI were identified; 14 (7.7%) had PB and five (2.7%) had RB. Ten (5.5%) patients were known to have infective endocarditis, and five of these patients had PB or RB. Initial and subsequent MRSA isolates from patients with PB and RB had the same PFGE type. There were no significant differences in the distribution of PFGE types in patients with PB or RB (37% CMRSA-2/USA100; 37% CMRSA-10/USA300) compared with that in other patients (56% CMRSA-2/USA100; 32% CMRSA-10/USA300). All isolates were susceptible to vancomycin, but patients with PB or RB were more likely to have initial isolates with vancomycin minimum inhibitory concentration = 2.0 µg/mL (26% versus 10%; P=0.06). CONCLUSIONS: Persistent or recurrent MRSA bacteremia occurred in 10.4% of patients with MRSA BSIs. Initial isolates from patients with persistent or recurrent MRSA BSIs were more likely to exhibit reduced susceptibility to vancomcyin, but were not associated with any genotype.

HISTORIQUE: Les infections sanguines (IS) par le Staphylococcus aureus résistant à la méthicilline (SARM) s'associent à une morbidité et une mortalité considérables, particulièrement en présence d'une bactériémie persistante (BP) ou récurrente (BR). OBJECTIF: Déterminer la fréquence de BP et de BR chez les patients atteints d'une IS par le SARM et en caractériser les isolats. MÉTHODOLOGIE: Les chercheurs ont surveillé les IS par le SARM dans 13 hôpitaux canadiens pendant un an. La BP se définissait par une hémoculture positive qui persistait au moins sept jours, tandis que la BR désignait la récurrence d'une hémoculture positive au moins 14 jours après une hémoculture négative. Les chercheurs ont typé les isolats au moyen de l'électrophorèse sur gel en champ pulsé (ECP). Ils ont déterminé la susceptibilité à la vancomycine par Etest. RÉSULTATS: Les chercheurs ont retracé un total de 183 patients ayant une IS par le SARM. De ce nombre, 14 (7,7 %) avaient une BP et cinq (2,7 %), une BR. Dix patients (5,5 %) étaient atteints d'une endocardite infectieuse diagnostiquée, dont cinq avaient une BP ou une BR. Les isolats initiaux et subséquents de SARM chez les patients ayant une BP ou une BR présentaient le même type d'ECP. Il n'y avait pas de différence significative dans la distribution des types d'ECP chez les patients ayant une BP ou une BR (37 % de souche CSARM-2/USA100; 37% de souche CSARM-10/USA300) par rapport à celle des autres patients (56 % de souche CSARM-2/USA100; 32 % de souche CSARM-10/USA300). Tous les isolats étaient susceptibles à la vancomycine, mais les patients atteints d'une BP ou d'une BR étaient plus susceptibles de présenter des isolats initiaux de vancomycine dont la CMI = 2,0 µg/mL (26 % par rapport à 10 %; P=0,06). CONCLUSIONS: Les chercheurs ont observé une BP ou une BR par le SARM chez 10,4 % des patients atteints d'une IS par le SARM. Les isolats initiaux des patients atteints d'une IS persistante ou récurrente par le SARM risquaient davantage d'être moins susceptibles à la vancomycine, mais ne s'associaient à aucun génotype.

Linezolid resistance in Enterococcus faecium isolated in Ontario, Canada.

Recent studies have described linezolid-resistant MRSA and vancomycin-resistant enterococci (VRE) occurring worldwide, including an outbreak of linezolid-resistant MRSA. The objective of this study was to determine if linezolid-resistant enterococci are present in clinical isolates in Ontario, Canada. From January 2010 to June 2012, all enterococcal isolates submitted to the Public Health Ontario Laboratory (PHOL) for confirmation of VRE and susceptibility testing were included in this study. Of 2829 enterococcal isolates tested, 12 Enterococcus faecium were found to be resistant to linezolid. All linezolid-resistant isolates were also resistant to ampicillin, ciprofloxacin, and vancomycin. In addition, 33% of isolates were non-susceptible to daptomycin, whereas 41% were resistant to quinupristin/dalfopristin. Molecular characterization of these isolates showed that 8/12 isolates (66.7%) contained the mutation G2576T in 23S rRNA, which has been associated with linezolid resistance. Amplification and sequencing of L3- and L4-coding genes did not reveal mutations associated with linezolid resistance. One isolate contained the cfr gene, which is associated with linezolid resistance, and has been found in staphylococcal species and E. faecalis. These data show that occurrence of linezolid resistance is still rare among enterococcal isolates referred to PHOL though detection of cfr in E. faecium is concerning as it has the potential to disseminate among other enterococci.

Antimicrobial susceptibilities of clinical isolates of HACEK organisms.

The "HACEK" organisms are a group of fastidious Gram-negative bacteria that cause a variety of infections, including infective endocarditis. Antimicrobial susceptibility testing is not universally available, and therapy for these infections is often empirical. We report the antimicrobial susceptibilities of 70 clinical HACEK isolates to 18 antimicrobials. All isolates were susceptible to ceftriaxone and levofloxacin, indicating that these agents remain appropriate empirical choices for the treatment of infections with this group of organisms.

Direct mecA polymerase chain reaction testing of blood culture bottles growing Gram-positive cocci and the clinical potential in optimizing antibiotic therapy for staphylococcal bacteremia.

This study evaluated the performance of direct mecA polymerase chain reaction (PCR) from blood culture bottles growing Gram-positive cocci in clusters and its role in optimization of antibiotic therapy. A total of 266 blood cultures including 121 methicillin-resistant and 122 methicillin-susceptible Staphylococci were tested for mecA. Compared to phenotypic testing, the overall performance of direct mecA PCR was 99% for sensitivity, specificity, positive predictive value, and negative predictive value, respectively. Assessment of antibiotic therapy upon microbiology reporting of direct mecA PCR results from 38 patients prior to (phase I) and 48 patients after implementation of testing and reporting (phase II) showed that the mean time to antibiotic optimization in phase II (0.9 ± 0.9 day) was significantly shorter than that in phase I (2.2 ± 3.2 days) (P < 0.05). Methicillin-susceptible staphylococcal bacteremias had significantly higher frequency of antibiotic adjustment upon direct mecA reporting, compared to methicillin-resistant staphylococcal bacteremias. Our study indicated that direct mecA PCR improved timely antibiotic optimization.

A 7-year retrospective review from 2005 to 2011 of Propionibacterium acnes shoulder infections in Ottawa, Ontario, Canada.

This study evaluated the clinical factors associated with Propionibacterium acnes shoulder infection and the standard culture procedures for isolating P. acnes from shoulder specimens by a 7-year retrospective analysis. P. acnes was incriminated as the second most common pathogen in 17 of 80 patients with positive shoulder cultures. All of the 17 patients had prior shoulder implant. The cumulative rates for isolating P. acnes were 1.9%, 1.9%, 41.9%, 96.4%, and 100% at day 1 to day 5 of incubation, respectively. The standard practice of anaerobic culture was able to detect P. acnes from shoulder specimens in patients with a clinical suspicion of infection. The sensitivity and specificity of prolonged incubation remain to be determined.