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Infective endocarditis (IE) has been increasingly recognized as an important complication of Staphylococcus aureus bacteremia (SAB), leading to a low threshold for echocardiography and extended treatment with anti-staphylococcal agents. However, outside of IE, many indications for prolonged anti-staphylococcal therapy courses are present. We sought to determine the frequency in which findings from a transesophageal echocardiogram (TEE) changed clinical SAB management in a large Canadian health region. Residents (> 18 years) with SAB from 2012 to 2014 who underwent transthoracic echocardiogram (TTE) and TEE were assessed. Patients potentially benefiting from an extended course of anti-staphylococcal agents were defined a priori. Patient demographics, treatment (including surgical), and clinical outcomes were extracted and evaluated. Of the 705 episodes of SAB that underwent a screening echocardiogram, 203 episodes underwent both a TTE and TEE, of which 92.1% (187/203) contained an a priori indication for extended anti-staphylococcal therapy. Regardless of TEE results, actual duration of therapy did not differ in SAB episodes that had ≥ 1 extended anti-staphylococcal therapy criteria (36.7 days, IQR 23.4–48.6 vs. 43.8 days, IQR 33.3–49.5, p = 0.17). Additionally, there were no cases in which TEE was utilized as the sole reason to shorten duration of therapy or proceed to surgery for those with SAB. Routine performance of TEE may be unnecessary in all SAB as many patients have pre-existing indications for extended anti-staphylococcal therapy independent of TEE findings. An algorithm to selectively identify cases of SAB that would benefit from TEE can reduce resource and equipment expenditure and patient risks associated with TEE.

The rapid detection of carbapenemase-producing organisms (CPOs) directly from blood cultures (BCs) positive for Gram-negative bacilli (GNB) may accelerate the appropriate treatment of at-risk patients. To evaluate the performance of two commercial assays in the rapid detection of CPOs directly from BC positive for GNB. BC positive for GNB were tested for the presence of CPOs with β CARBA® and NG-Test® CARBA 5. A subset of sterile BC samples was seeded with multidrug-resistant (MDR) GNB. Positive BCs from clinical and seeded samples were tested directly with β CARBA and CARBA 5 from BC pellets. Sixty-five samples were tested (30 clinical, 35 seeded). β CARBA had a sensitivity, specificity, NPV, and PPV of 100%, 65.7%, 100%, and 71.4%, respectively. CARBA 5 had a sensitivity, specificity, NPV, and PPV of 90.0%, 100%, 92.1%, and 100%. False negatives for CARBA 5 occurred with 1 GES, 1 VIM-1, and 1 IMP-14. This study demonstrates that the detection of CPOs directly from positive BC can be accurately achieved. β CARBA had excellent sensitivity but suffered from poor specificity. CARBA 5 had good sensitivity and specificity but is unable to detect certain CPOs.

Background Pyogenic liver abscess (PLA), although uncommon in North America, is associated with significant morbidity and mortality. We sought to re-examine the epidemiology, risk factors, and outcomes of PLA in a large, diverse Canadian health zone. Methods All Calgary Health Zone (CHZ) residents aged ≥20 with PLA between 2015 and 2017 were identified. Incidence and mortality rates were calculated using census data. Risk factors for PLA were identified using a multivariate analysis. Data was compared to 1999–2003 data, also collected in the CHZ. Results There were 136 patients diagnosed with PLA between 2015 and 2017. Incidence rate during this period increased significantly relative to 1999–2003 (3.7 vs 2.3 cases/100,000 population, p Conclusions Pyogenic liver abscess is a health concern with rising incidence rate. The increasing prevalence of comorbidities in our population and factors that are associated with risk of PLA suggests this will continue to be an emerging diagnosis of concern. Increasing prevalence of antibiotic resistant organisms compounding unclear optimal treatment regimens is an issue that requires urgent study.

Background Escherichia coli is the most common cause of bloodstream infections (BSIs) and mortality is an important aspect of burden of disease. Using a multinational population-based cohort of E. coli BSIs, our objectives were to evaluate 30-day case fatality risk and mortality rate, and determine factors associated with each. Methods During 2014–2018, we identified 30-day deaths from all incident E. coli BSIs from surveillance nationally in Finland, and regionally in Sweden (Skaraborg) and Canada (Calgary, Sherbrooke, western interior). We used a multivariable logistic regression model to estimate factors associated with 30-day case fatality risk. The explanatory variables considered for inclusion were year (2014–2018), region (five areas), age ( Results From 38.7 million person-years of surveillance, we identified 2961 30-day deaths in 30,923 incident E. coli BSIs. The overall 30-day case fatality risk was 9.6% (2961/30923). Calgary, Skaraborg, and western interior had significantly increased odds of 30-day mortality compared to Finland. Hospital-onset and 3GC-resistant E. coli BSIs had significantly increased odds of mortality compared to community-onset and 3GC-susceptible. The significant association between age and odds of mortality varied with sex, and contrasts were used to interpret this interaction relationship. The overall standardized 30-day mortality rate was 8.5 deaths/100,000 person-years. Sherbrooke had a significantly lower 30-day mortality rate compared to Finland. Patients that were either ≥70-years-old or male both experienced significantly higher mortality rates than those Conclusions In our study populations, region, age, and sex were significantly associated with both 30-day case fatality risk and mortality rate. Additionally, 3GC resistance and location of onset were significantly associated with 30-day case fatality risk. Escherichia coli BSIs caused a considerable burden of disease from 30-day mortality. When analyzing population-based mortality data, it is important to explore mortality through two lenses, mortality rate and case fatality risk.

Background Staphylococcus aureus bacteriuria (SABU) may represent multiple processes ranging from asymptomatic colonization to a marker of S. aureus bacteremia (SAB). Our objective was to describe SABU at a population-based level and determine patient characteristics associated with SAB. Methods A retrospective study was performed using electronic databases. All urine cultures positive for S. aureus between 2010 and 2013 within the Calgary Health Zone were included. Patient characteristics were compared among patients with and without SAB and risk factors identified using multiple logistic regression modeling. Results A total of 2540 urine cultures positive for S. aureus from 2054 patients were analyzed. The incidence of SABU was greatest among geriatric males with multiple comorbidities. SAB occurred in 175 (6.9%) of SABU patients. Those with SAB were more likely to be hospitalized, male, have a recent urinary procedure, have pure S. aureus culture in urine, and have laboratory findings suggesting systemic infection. Patients with isolated SABU were more likely to be ≥65 years, have dementia, and have abnormal urinalyses with pyuria and urine nitrites. In-hospital mortality in patients with SABU and SABU+SAB was 9.2% and 17.5%, respectively. Patients with SABU detected ≥48 hours before SAB had the highest risk of death. Conclusions Less than 7% of patients with SABU have or will develop SAB. Characteristics associated with SABU were identified that established higher risk for systemic infection. Investigating SABU patients with these characteristics for systemic infection is warranted because a delay in diagnosis is associated with increased mortality.

Staphylococcus aureus bacteremia (SAB) is associated with significant morbidity and mortality. We sought to re-define the burden, epidemiology and mortality-associated risk factors of SAB in a large Canadian health region. Residents (> 18 years) experiencing SAB from 2012 to 2014 were assessed. Incidence rates were calculated using civic census results. Factors associated with 30-day mortality were determined through multivariate logistic regression. Incidence and risk factors for SAB were compared to 2000–2006 data. 780 residents experienced 840 episodes of SAB (MRSA; 20%). Incidence rates increased from 23.5 to 32.0 cases/100,000 from 2012 to 2014; [IRR 1.15 (95% CI 1.07–1.23); p

Background PLA is a significant cause of morbidity and mortality. However, its epidemiology and outcomes have not been recently evaluated in the CHZ. Understanding current trends will help guide management. Methods In this population-based study, we evaluated epidemiology, risk factors, and treatment of patients with PLA in the CHZ. CHZ residents aged ≥ 20 years diagnosed with PLA in 2015-2017 were included. Charts were reviewed for demographics and clinical outcomes. Multivariate logistic regression was used to determine factors associated with 30-day mortality. Findings were compared to a previous assessment of PLA in the CHZ from 1999-2003 (Kaplan et al., 2004). Results A total of 136 patients with PLA were identified, representing an annual incidence rate of 3.7 cases per 100,000 population. Compared to 1999-2003, incidence of PLA was increased (2.3 per 100,000; p< 0.01) but mortality was similar (1999-2003: 0.22 per 100,000 vs. 2015-2017: 0.26 per 100,000; p=0.6). The most common culprit organisms were Streptococcus anginosus group (40%), Klebsiella species (25%), Escherichia coli (18%), and obligate anaerobes (16%). Pathogen prevalence was similar to the prior cohort. Compared to 1999-2003, antibiotic resistant organisms were more frequent (8% vs 1%, p=0.04). In our cohort, liver aspirations were less frequent (p=0.02) but aspirate culture was more often positive (p< 0.01). The median duration of intravenous antibiotic therapy was longer compared to previous (2015-2017: 23 days (IQR 9-38) vs. 1999-2003: 17 days (IQR 10-29); p=0.001). Similarly, the total duration of antibiotic therapy was longer (2015-2017: 42 days (IQR 25-65) vs. 1999-2003: 31 days (IQR 18-45); p< 0.001). Thirty-day mortality from admission was 7% and did not differ amongst cohorts. Risk factors are shown in Table-1. Table-1: Risk factors for 30-day mortality in PLA Conclusion Incidence of PLA in the CHZ is rising with more antimicrobial resistance. Diagnostic liver aspirations are less frequent. Antibiotic durations are longer with no reduction in mortality. Understanding changing trends is valuable in directing future care. Encouraging liver aspirations to obtain a microbiologic diagnosis, especially with increasing resistance, is crucial. Considering shorter antibiotic durations in light of stable mortality warrants further exploration. Disclosures All Authors: No reported disclosures

Background The recognition of infective endocarditis (IE) as a serious complication of SAB has led to a low threshold for echocardiography, extended treatment (eTx) with anti-staphylococcal agents (anti-SA), and even surgery. However, indications for eTx outside of IE are numerous. We sought to determine the frequency in which findings from a TEE changed clinical SAB management. Methods Adults with SAB within the Calgary Health Zone between 2012 and 2014 were included if both a transthoracic echocardiogram (TTE) and TEE were performed within 7 days of each other. Patients potentially benefiting from eTx courses were a priori defined as having ≥1 of; (1) metastatic phenomena, (2) complicated SAB (defined as community acquired (CA), persistent fever/bacteremia at ≥48 hours), (3) intracardiac devices, and/or (4) Duke criteria defined IE (separately evaluated using TTE or TEE). Patient demographics, treatment (including changes to anti-SA duration and surgical indications), and clinical outcomes were extracted and evaluated. Results Of 961 SAB episodes, 179 (18% MRSA) met inclusion criteria (median 3.0 days, IQR 1.9–5.1 between TTE and TEE). Within the cohort 29% (n = 51) had metastatic phenomena (intracranial; 9% [n = 16], vertebral; 8% [n = 14]; empyema; 6% [n = 11]). Complicated bacteremia was present in 89% (n = 159), while 13% (n = 23) had intravascular hardware (39% pacemakers, 65% valve prostheses). IE was diagnosed in 22% (n = 40) of SAB episodes, with TTE identifying 58% of vegetations (n = 23) and TEE identifying an additional 30% (n = 15). Of the cohort, 89% (n = 160), 37% (n = 67), 4% (n = 7) of SAB had ≥1, 2, and 3 nonechocardiographic indications for eTx, respectively. Only one patient met criteria for eTx solely based on IE diagnosed from concordant TTE and TEE. Actual duration of therapy did not differ in SAB episodes that had ≥1 a priori eTx criteria but had a negative TEE relative to those who had a positive TEE (36.7 days, IQR 23.4–48.6 vs. 43.8 days, IQR 33.3–49.5, P = 0.17). Of the 15 episodes of TEE-only evident IE, 14 were CA, 12 had prolonged BSI, and nine embolic phenomena. Only 11 patients in the cohort required cardiac surgery, none were identified exclusively by TEE. Conclusion Routine performance of TEE may not be required in all SAB as many patients have alternate indications for eTx with anti-SA regardless of TEE findings. Disclosures All authors: No reported disclosures.

The characteristics of hypermucoviscosity isolates amongKlebsiella pneumoniaecausing community-acquired bacteremia were investigated. The hypermucoviscous phenotype was present in 8.2% ofK pneumoniaeisolates, and was associated with rmpA and the K2 serotype; liver abscesses were the most common clinical presentation. The present analysis represents the first population-based surveillance study of hypermucoviscosity amongK pneumoniaecausing bacteremia.

A study was designed to assess the importance of sequence types among extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates causing bacteremia over an 11-year period (2000 to 2010) in a centralized Canadian region. A total of 197 patients with incident infections were identified; the majority presented with community-onset urosepsis, with a significant increase in the prevalence of ESBL-producing E. coli during the later part of the study. The majority of E. coli isolates produced either CTX-M-15 or CTX-M-14. We identified 7 different major sequence types among 91% of isolates (i.e., the ST10 clonal complex, ST38, ST131, ST315, ST393, ST405, and ST648) and provided insight into their clinical and molecular characteristics. ST38 was the most antimicrobial-susceptible sequence type and predominated during 2000 to 2004 but disappeared after 2008. ST131 was the most antimicrobial-resistant sequence type, and the influx of a single pulsotype of this sequence type was responsible for the significant increase of ESBL-producing E. coli strains since 2007. During 2010, 49/63 (78%) of the ESBL-producing E. coli isolates belonged to ST131, and this sequence type had established itself as a major drug-resistant pathogen in Calgary, Alberta, Canada, posing an important new public health threat within our region. We urgently need well-designed epidemiological and molecular studies to understand the dynamics of transmission, risk factors, and reservoirs for E. coli ST131. This will provide insight into the emergence and spread of this multiresistant sequence type.

Summary Objectives Time to blood culture positivity (TTP) has been suggested as a prognostic factor for adverse clinical outcome. This study describes the relationship between TTP and clinical outcome in all patients with Staphylococcus aureus bacteremia (SAB) in a large Canadian health region. Methods We performed a retrospective study of all first episodes of SAB occurring in the former Calgary Health Region (population ∼1.2 million) from July 1, 2006 to December 31, 2008. Results Overall, 684 cases of SAB were evaluated. The median TTP was 16 h and 31/684 (5%) cases had TTP at >48 h. Time to positivity was shorter for methicillin-susceptible Staphylococcus aureus compared with methicillin-resistant S. aureus (MRSA) and for endovascular sources compared with other sources of infection. The overall 30-day case-fatality rate was 18% (124/684). Patients with delayed TTP (>48 h) suffered the highest case-fatality rate (39%) compared to those with earlier TTP (17%; P = 0.002). Multivariable logistic regression modeling showed that age, nosocomial acquisition, MRSA, focus of infection, liver disease, and TTP ≤12 and >48 h were associated with 30-day mortality. Conclusion Although uncommon, delayed TTP may be associated with increased mortality. Empiric antimicrobial therapy should continue beyond 48 h in patients at high risk for SAB.

A study was designed to characterize extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli isolates causing bacteremia over an 8-year period (2000 to 2007) in a large well-defined geographical region. Molecular characterization was done by using isoelectric focusing; PCR; and sequencing of the bla CTX-M -, bla TEM -, bla OXA -, bla SHV -, and plasmid-mediated quinolone resistance determinants. Genetic relatedness was determined by pulsed-field electrophoresis with XbaI and multilocus sequence typing. A total of 67 patients with incident bloodstream infections were identified, and the majority presented with community-acquired infections involving the urinary and biliary tracts. Of the 67 ESBL-producing E. coli isolates recovered, 60 (90%) were positive for bla CTX-M genes; 32 (48%) produced CTX-M-15, 25 (37%) produced CTX-M-14, 1 (2%) produced CTX-M-24, 1 (2%) produced CTX-M-2, and 1 (2%) produced CTX-M-3, while 2 (3%) produced TEM-52 and 5 (7%) produced SHV-2. Twenty-four (36%) isolates were positive for aac(6′)-Ib-cr. The majority of isolates were resistant to ciprofloxacin (60 [90%] isolates) and gentamicin (40 [60%] isolates). The occurrence of ESBL-producing isolates was stable during the first 5 years, but there was a substantial increase from 2005 to 2007, mostly due to clone ST131, which produces CTX-M-15 and CTX-M-14, in blood cultures submitted from the community. Our results illustrated that E. coli clone ST131, which coproduces CTX-M-15, OXA-1, TEM-1, and aac(6′)-Ib-cr , has emerged as an important cause of community-onset bacteremia caused by ESBL-producing E. coli isolates; and this is the first study to identify CTX-M-14 in E. coli clone ST131.

Background: The epidemiology of pediatric bloodstream infection has not been well defined in general populations. The primary objective of this study was to describe the burden of illness of pediatric bloodstream infections in a large Canadian region and secondarily to assess the effect of implementation of universal infant immunization with 7-valent pneumococcal conjugate vaccine (PCV7) in 2002. Methods: Surveillance for all bloodstream infections was conducted among pediatric (

Intensive care unit-acquired (ICU-acquired) bloodstream infections (BSI) are an important complication of critical illness. The objective of this study was to quantify the excess length of stay, mortality and cost attributable to ICU-acquired BSI. A matched cohort study was conducted in all adult ICUs in the Calgary Health Region between 1 May 2000 and 30 April 2003. One hundred and forty-four patients with ICU-acquired BSI were matched (1:1) to patients without ICU-acquired BSI. Patients with ICU-acquired BSI had a significantly increased median length of ICU stay {15.5 [interquartile range (IQR) 8-26] days vs 12 [IQR 7-18.5] days, P=0.003} and median costs of hospital care [85,137 dollars (IQR 45,740-131,412 dollars) vs 67,879 dollars (IQR 35,043-115,915 dollars, P=0.02) compared with patients without ICU-acquired BSI. The median excess length of ICU stay was two days and the median cost attributable to ICU-acquired BSI was 12,321 dollars per case. Sixty (42%) of the cases died compared with 37 (26%) of the controls [P=0.002, attributable mortality 16%, 95% confidence interval (CI) 5.9-26.0%]. Patients with ICU-acquired BSI were at increased risk for in-hospital death (odds ratio=2.64, 95%CI 1.40-5.29). Among survivor-matched pairs, the median excess lengths of ICU and hospital stay attributable to development of ICU-acquired BSI were two and 13.5 days, respectively, and the attributable cost due to ICU-acquired BSI was 25,155 dollars per case survivor. Critically ill patients who develop ICU-acquired BSI suffer excess morbidity and mortality, and incur significantly increased healthcare costs. These data support expenditures on infection prevention and control programmes and further research into reducing the impact of these infections.

Background A study was conducted in the Calgary Health Region between May 2002 and April 2004 to define the population-based epidemiological characteristics of infections caused by imipenem-resistant Pseudomonas aeruginosa and to explore the clinical outcomes due to metallo- beta -lactamase (MBL)-producing and non-MBL-producing strains. Methods Detailed clinical information was obtained by chart review, and phenotypic and molecular characterizations were performed using the MBL E-test, polymerase chain reaction with sequencing, and pulsed-field gel electrophoresis. Results A total of 228 patients with infections caused by imipenem-resistant P. aeruginosa were identified (annual incidence, 10.5 cases/100,000 population), with the highest incidence rate in those >or=75 years old. MBL-producing strains (98/228) were associated with higher rates of multidrug resistance and bacteremia. Ninety MBL-producing strains also produced VIM-2, 4 produced IMP-7, and 4 were unclassified. A cluster of VIM-2-producing strains was responsible for a nosocomial outbreak during 2003. The case-fatality rate was significantly higher for infections caused by MBL-producing strains than for those caused by non-MBL-producing strains (25% vs. 13%; relative risk, 1.98 [95% confidence interval, 1.00-3.90]; P=.05). Conclusion MBL-producing P. aeruginosa strains were associated with a higher case-fatality rate and invasive disease. Our study highlights the potential importance of molecular laboratory techniques in infection control and patient care.

Context.—Bacterial cultures of bronchoscopic samples require 1 to 2 days for results to be available for use in clinical decisions. We developed a rapid diagnostic testing strategy that is highly sensitive for screening bacteria in bronchoalveolar lavage (BAL) samples, with results available within hours of collection. Objective.—To validate the ability of a bacterial adenosine triphosphate (ATP) assay and routine Gram stain microscopy to detect significant bacterial counts in BAL samples. Design.—Four hundred seventy-seven BAL samples from 319 patients suspected of having pneumonia were tested using a rapid diagnostic strategy, consisting of Gram stain and a bacterial ATP assay. Rapid results were compared with quantitative cultures with a positive cutoff of 104 CFU/mL or higher. Results.—Significant bacterial counts were identified in 107 samples (22%). The most common etiologic agents were Staphylococcus aureus (25%), Haemophilus influenzae (17%), and Streptococcus pneumoniae (12%). The rapid test results were false negative in 5 cases (S aureus in 2, both Klebsiella pneumoniae and S aureus in 1, and Stenotrophomonas maltophilia and S pneumoniae in 1 case each). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the rapid diagnostic strategy were 95.3%, 54.9%, 37.9%, 97.6%, and 63.9%, respectively. Conclusion.—A negative result with this rapid diagnostic testing strategy rules out significant bacterial counts in BAL samples with a high degree of certainty and may allow use of narrow-spectrum antimicrobial agents or withholding of empiric antimicrobial therapy in patients suspected of having ventilator-associated pneumonia.

Pyogenic liver abscess (PLA) is relatively uncommon in North America but is associated with significant morbidity and mortality. Our objective was to characterize the incidence of, risk factors for, and outcomes of PLA in a nonselected population.Population-based surveillance was conducted in the Calgary Health Region (CHR) between April 1, 1999 and March 31, 2003. All adult CHR residents with PLA were identified, and charts were reviewed.Seventy-one CHR residents developed a PLA for an annual incidence of 2.3 per 100,000 population. There was an increasing incidence of PLA with advancing age. Men were at much higher risk of acquiring a PLA as compared to women (3.3 vs 1.3 per 100,000; relative risk [RR], 2.6; 95% confidence interval [CI], 1.5-4.6; P.001), and this was observed across all age groups. A number of comorbid conditions were associated with significantly higher risk for developing a PLA including liver transplantation patients (RR, 444.8; 95% CI, 89.5-1356.0; P.0001), diabetics (RR, 11.1; 95% CI, 6.3-19; P.0001), and patients with a history of malignancy (RR, 13.3; 95% CI, 6.9-24.4; P.0001). No other solid organ transplantation patient was at increased risk. All patients required admission to hospital (median length of stay, 16 days), and 7 (10%) patients died in hospital, corresponding to a mortality rate of 0.22 per 100,000 population.This study provides important data on the burden of PLA and identifies risk groups that might potentially benefit from preventive efforts.

Context.—A regional centralized laboratory service for the rapid diagnosis of malaria was implemented 3 years ago in May 1999 within the Division of Microbiology, Calgary Laboratory Services. Objective.—To describe the design and performance of this unique microbiology laboratory service. Design.—Blood specimens must arrive at the central laboratory within 2 hours of collection. Thin blood smears are read and reported from suspected acute cases within 1 hour of receipt, 24 hours per day, 7 days a week, by trained and experienced microbiology technologists. All positive malaria smears are reviewed by a medical microbiologist and confirmed by polymerase chain reaction at a reference laboratory. Setting.—Calgary Laboratory Services provides integrated laboratory services to the Calgary Health Region, an urban area of more than 1 million people. Main Outcome Measures.—Performance of the service has been continuously monitored by measuring preanalytic and analytic test turnaround times, test accuracy, clinical relevance, and the results of proficiency testing. Results.—More than 90% of blood specimens for malaria from community locations have consistently arrived within 2 hours of collection, and hospitals have reached this target within the past year. Although polymerase chain reaction was more sensitive at detecting the presence of malaria, the expert microscopists were as accurate at determining the type of Plasmodium infection. More than 95% of all positive smear results are consistently reported within 2 hours of receipt of a blood specimen. Conclusions.—Implementation of a regional centralized microbiology service has improved our ability to make a rapid and accurate diagnosis of malaria in this region.

Background Although the nares represent the most common carriage site for traditional hospital-associated strains of Staphylococcus aureus (SA), the predominant site of carriage of SA in the community is less certain. Methods We conducted a cross-sectional study in 285 patients attending sexually transmitted diseases and inner-city clinics to evaluate the prevalence, body site colonisation and risk factors associated with carriage of methicillin susceptible SA (MSSA). All isolates were characterized by pulsed field gel electrophoresis, staphylococcal cassette chromosome mec, staphylococcal protein A and multilocus sequence typing. Results The prevalence of colonisation with SA was 57.5% (164/285); 162 (56.8%) participants were colonized with MSSA, and 4 (1.4%) with methicillin-resistant SA (MRSA), 2 of them were co-colonised with both MRSA and MSSA. The most common sites of colonisation were the throat (73.1%), nares (65.2%) and interdigital web spaces of the hand (21.3%). Three out of 4 MRSA isolates were USA300-MRSA strains. Twelve MSSA isolates were closely related to the USA300 CA-MRSA. We identified sexual behaviours such as having more than 6 heterosexual sexual partners in the last 6 months and trimming pubic hair to be independently associated with MSSA colonisation, and more specifically practicing oral sex as a risk factor for throat colonisation. Conclusion There is a high prevalence of MSSA carriage in this population, with a low prevalence of MRSA. The throat was the most common site of carriage and sexual behaviours were found to be risk factors for MSSA colonisation. Close strain relatedness of MSSA and USA300-MRSA isolates suggests either gain or loss of the SCCmec element, respectively.

Background. The early detection of cytomegalovirus (CMV) after liver transplantation may form the basis of a preemptive strategy for prevention of active CMV disease. Methods. We prospectively analyzed the clinical use of weekly quantitative polymerase chain reaction-(PCR) based plasma viral load determinations and the antigenemia assay for predicting the development of active CMV disease in 97 consecutive liver transplant recipients. Results. CMV disease occurred in 21/97 patients. Using a positive cut-off of >400 copies/ml plasma, PCR had a sensitivity of 100%, specificity 47.4%, positive predictive value 34.4% and negative predictive value 100% for prediction of CMV disease. Respective values for a positive antigenemia (>0 positive cells/slide) were 95.2, 55.3, 37.0, and 97.7%. Different cut-off points for a positive test were analyzed using receiver-operating characteristic (ROC) curves. The optimal cut-off for viral load was in the range of 2000-5000 copies/ml (sensitivity 85.7%, specificity 86.8%, PPV 64.3%, NPV 95.7% for >5000 copies/ml). The optimal cut-off for antigenemia was in the range of four to six positive cells/ slide. Mean peak viral load in symptomatic patients was 73,715 copies per/ml versus 3615 copies/ml in patients with asymptomatic CMV reactivation (P

The clinical presentation and diagnosis of malaria involving a family with seven children who arrived in Canada as refugees is reported. Discrepancies in front-line testing using microscopy and rapid diagnostic tests compared with confirmatory testing using real-time polymerase chain reaction in this cluster of symptomatic and asymptomatic patients were identified.

Background Bloodstream infections (BSI) have been traditionally classified as either community acquired (CA) or hospital acquired (HA) in origin. However, a third category of healthcare-associated (HCA) community onset disease has been increasingly recognized. The objective of this study was to compare and contrast characteristics of HCA-BSI with CA-BSI and HA-BSI. Methods All first episodes of BSI occurring among adults admitted to hospitals in a large health region in Canada during 2000-2007 were identified from regional databases. Cases were classified using a series of validated algorithms into one of HA-BSI, HCA-BSI, or CA-BSI and compared on a number of epidemiologic, microbiologic, and outcome characteristics. Results A total of 7,712 patients were included; 2,132 (28%) had HA-BSI, 2,492 (32%) HCA-BSI, and 3,088 (40%) had CA-BSI. Patients with CA-BSI were significantly younger and less likely to have co-morbid medical illnesses than patients with HCA-BSI or HA-BSI (p < 0.001). The proportion of cases in males was higher for HA-BSI (60%; p < 0.001 vs. others) as compared to HCA-BSI or CA-BSI (52% and 54%; p = 0.13). The proportion of cases that had a poly-microbial etiology was significantly lower for CA-BSI (5.5%; p < 0.001) compared to both HA and HCA (8.6 vs. 8.3%). The median length of stay following BSI diagnosis 15 days for HA, 9 days for HCA, and 8 days for CA (p < 0.001). Overall the most common species causing bloodstream infection were Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. The distribution and relative rank of importance of these species varied according to classification of acquisition. Twenty eight day all cause case-fatality rates were 26%, 19%, and 10% for HA-BSI, HCA-BSI, and CA-BSI, respectively (p < 0.001). Conclusion Healthcare-associated community onset infections are distinctly different from CA and HA infections based on a number of epidemiologic, microbiologic, and outcome characteristics. This study adds further support for the classification of community onset BSI into separate CA and HCA categories.

Although infections withStaphylococcus aureuscan implicate multiple organ systems, involvement of the biliary tract is rare. A case of acute cholecystitis and bacteremia with methicillin-resistantS aureus(MRSA) in a patient with HIV infection is presented. The MRSA isolate was found to be a community-associated strain. The present case highlights the invasive nature of staphylococcal infections and the emerging importance of community-associated MRSA strains.

HIV clinics in Canada provide care to an increasing number of patients born outside of Canada with HIV-1 non-B subtype infections. Because the Easy Q HIV-1 v1.2 assay (EQ; bioMérieux) failed to detect some non-B subtype infections, a multiassay HIV-1 viral load (VL) study was conducted with patients with diverse HIV subtype infections. Patients were enrolled from the Southern Alberta HIV Clinic (SAC), Calgary, Alberta, Canada ( n = 349) and the McGill HIV Clinic (MHC), Montreal, Quebec, Canada ( n = 20) and had four or five tubes of blood drawn for testing by EQ and three other commercial HIV VL assays: (i) the Versant 3.0 HIV-1 test, with the Versant 440 instrument (branched DNA [bDNA]; Siemens), (ii) the RealTime HIV-1 test, with the m 2000rt instrument ( m 2000rt; Abbott Molecular Diagnostics), and (iii) the COBAS AmpliPrep TaqMan HIV-1 48 test (CAP-CTM; Roche Molecular Diagnostics). Blood was processed according to the individual manufacturer's requirements and stored frozen at −86°C. The HIV subtype was known for patients who had undergone HIV genotypic resistance testing (Virco, Belgium). Data analyses were done using standard statistical methods within Stata 9.0 (StataCorp, College Station, TX). A total of 371 samples were tested on 369 patients, of whom 291 (81%) had a Virco genotype result of B (195; 53%) or non-B (96; 26%) subtypes A to D and F to K, as well as circulating recombinant forms (CRFs) (i.e., CRF01_AE and CRF02_AG). Most (58/78; 74%) patients of unknown subtype were recent African emigrants who likely have non-subtype B infection. Overall bias was small in pairwise Bland-Altman plots, but the limits of agreement between assays were wide. Discordant viral load results occurred for 98 samples and were due to missing values, false negatives, and significant underquantification that varied by HIV subtype. Results were obtained for all 371 samples with m 2000rt, but for only 357 (97%) with CAP-CTM, 338 (92%) with EQ, and 276 (75%) with bDNA due to errors/equipment failures. False-negative results (nondetection of viral RNA versus other assay results) occurred for all platforms, as follows: for m 2000rt, 8 (2%) [B(4) and non-B(4) subtypes], CAP-CTM, 9 (2.5%) [B(6) and non-B(3) subtypes]; EQ, 20 (6%) [B(7) and non-B(13) subtypes]; bDNA, 5 (2%) [B(1) and C(4)]. EQ and bDNA had the highest rates of underquantification by ≥1.0 log 10 copies/ml, mainly for HIV non-B subtypes. Performance significantly varied between HIV VL platforms according to subtype. HIV viral diversity in the population being tested must be considered in selection of the viral load platform.

Background.Electronic surveillance systems (ESSs) that utilize existing information in databases are more efficient than conventional infection surveillance methods.Objective.To develop an ESS for monitoring bloodstream infections (BSIs) and assess whether data obtained from the ESS were in agreement with data obtained by traditional manual medical-record review.Methods.An ESS was developed by linking data from regional laboratory and hospital administrative databases. Definitions for excluding BSI episodes representing contamination and duplicate episodes were developed and applied. Infections were classified as nosocomial infections, healthcare-associated community-onset infections, or community-acquired infections. For a random sample of episodes, data in the ESS were compared with data obtained by independent medical chart review.Results.From the records of the 306 patients whose infections were selected for comparative review, the ESS identified 323 episodes of BSI, of which 107 (33%) were classified as healthcare-associated community-onset infections, 108 (33%) were classified as community-acquired infections, 107 (33%) were classified as nosocomial infections, and 1 (0.3%) could not be classified. In comparison, 310 episodes were identified by use of medical chart review, of which 116 (37%) were classified as healthcare-associated community-onset infections, 95 (31%) as community-acquired infections, and 99 (32%) as nosocomial infections. For 302 episodes of BSI, there was concordance between the findings of the ESS and those of traditional manual chart review. Of the additional 21 discordant episodes that were identified by use of the ESS, 17 (81%) were classified as representing isolation of skin contaminants, by use of chart review. Of the additional 8 discordant episodes further identified by use of chart review, most were classified as repeat or polymicrobial episodes of disease. There was an overall 85% agreement between the findings of the ESS and those of chart review (K = 0.78; standard error, K = 0.04) for classification according to location of acquisition.Conclusion.Our novel ESS allows episodes of BSI to be identified and classified with a high degree of accuracy. This system requires validation in other cohorts and settings.

Immunoglobin A-dominant postinfectious glomerulonephritis is a distinct clinicopathologic entity that has been linked to staphylococcal infection, including methicillin-resistant Staphylococcus aureus. An association with diabetic nephropathy has been suggested. Although the morphologic features resemble other forms of postinfectious glomerulonephritis, immunofluorescence shows dominant or codominant immunoglobulin A immune-complex deposits. We encountered 7 patients with immunoglobulin A-dominant postinfectious glomerulonephritis over 2½ years at a single center. All patients presented with renal failure and with varying degrees of hematuria, proteinuria, and hypertension. All patients had clinical infections at the time of presentation. Four patients had documented S aureus infections. Three patients had methicillin-resistant S aureus infection within 2 weeks before the renal biopsy; 2 of these had an infection with a community-associated methicillin-resistant S aureus-10 clone, equivalent to USA300. One patient had methicillin-sensitive S aureus infection. Diffuse proliferative endocapillary glomerulonephritis was found in all cases; 1 had a membranoproliferative glomerulonephritic pattern, and 1 patient had a crescentic glomerulonephritis. Immunofluorescence microscopy showed dominant immunoglobulin A subepithelial and mesangial immune complexes in 5 patients and codominant immunoglobulin A with immunoglobulin G in 2 patients. Electron microscopy revealed large subepithelial deposits ("humps") in all cases. Only 1 patient had clinical diabetes mellitus but without biopsy-proven diabetic nephropathy. Two patients died, including the patient with diabetes mellitus. Renal function improved after therapy in 5 nondiabetic patients, but full recovery was not seen during the follow-up. We confirm that immunoglobulin A-dominant postinfectious glomerulonephritis is often associated with S aureus and methicillin-resistant S aureus infections, and, for the first time, we document an association with community-associated methicillin-resistant S aureus.

Staphylococcus aureus is recognized as an important cause of invasive disease in children (1,2). It has assumed an increasing relative importance as an agent of community-acquired outpatient bacteremia, especially in regions where successful widespread implementation of infant conjugate vaccines has reduced the incidence of invasive Haemophilus influenzae and Streptococcus pneumoniae diseases (3). S aureus is a frequent cause of hospital-acquired bacteremia, with patients admitted to neonatal and paediatric intensive care units at the highest risk (4–6). While nosocomial infections due to methicillin-resistant S aureus (MRSA) have been recognized in many jurisdictions for decades, in recent years, severe invasive infections due to MRSA strains have increasingly been reported (7–11) in patients, including children, without significant previous health care exposure. A number of studies (1,12,13) have been published describing the occurrence, clinical attributes and outcomes of S aureus bloodstream infections among children admitted to hospitals. However, studies conducted in selected hospitals may be biased by referral patterns, and incidence rates cannot be calculated using these designs (14,15). Population-based studies that identify all new cases of disease occurring among residents of a defined population at risk are optimal for defining the epidemiology of an infectious disease. However, only a few population-based studies of invasive or bacteremic S aureus infections have been conducted (2,16–25). To our knowledge, only two of these studies – one from Denmark (18) and the other from New Zealand (25) – have focused on children. The objective of the present study was to describe the incidence, clinical features and outcomes associated with S aureus bacteremia in all children living in a large Canadian health region from 2000 to 2006.

Background. Reports have suggested that the epidemiological profile of invasive Staphylococcus aureus infections is changing. We sought to describe the epidemiological profile of S. aureus bacteremia and to assess whether the incidence and severity of and the antimicrobial resistance rates associated with this bacteremia are increasing. Methods. Population-based surveillance for S. aureus bacteremias was conducted in the Calgary Health Region (population, 1.2 million) during 2000-2006. Results. The annual incidence of S. aureus bacteremia was 19.7 cases/100,000 population. Although rates of health care-associated and nosocomial methicillin-susceptible S. aureus (MSSA) bacteremia were similar throughout the study, rates of community-acquired MSSA bacteremia gradually decreased, and rates of methicillin-resistant S. aureus (MRSA) bacteremia dramatically increased. The clonal type predominantly isolated was CMRSA-2 (i.e., Canadian [C] MRSA-2), but CMRSA-10 (USA300) strains have been increasingly isolated, especially from community-onset infections, since 2004. Dialysis dependence, organ transplantation, HIV infection, cancer, and diabetes were the most important risk factors and were comparable for MSSA and MRSA bacteremias. The overall case-fatality rate was higher among individuals with MRSA (39%) than among those with MSSA (24%; P

Serratia marcescenshas rarely been reported as an agent of invasive disease in patients presenting from the community. Furthermore,S marcescensis frequently opportunistic, affecting individuals with serious medical comorbidities including immune suppression and diabetes. A case of a community-acquiredS marcescensspontaneous lumbar epidural abscess presenting as cauda equina syndrome is reported in a previously well 36-year-old man with no identifiable risk factors. To the authors’ knowledge, this is the first report of invasiveS marcescenscausing disease in a patient with no medical comorbidities.

Legionella infection causes 2 to 14% of community-acquired pneumonia (CAP). Legionella micdadei constitutes L. micdadei CAP in a myeloma patient receiving thalidomide treatment. The importance of considering pneumonia and problems in diagnosing pneumonia caused by L. micdadei in this patient population are reviewed.

Objectives Candida species have emerged as important causes of invasive infections and rates of resistance to standard antifungal therapies are rising. The objective of this study was to define the occurrence of, risk factors for, and antifungal susceptibilities of invasive Candida species infections in a large Canadian health region. Methods Population-based surveillance was conducted for invasive Candida species infections in the Calgary Health Region during a 5 year period and susceptibility testing was performed. Results The annual incidence of invasive Candida species infection was 2.9 per 100,000 population (0.2 and 2.8 per 100,000 for central nervous system and bloodstream infection, respectively). The very young and elderly were at highest risk for invasive Candida species infections. Several risk factors for developing invasive Candida species infection were identified with chronic haemodialysis, organ transplant recipient, and cancer patients at highest risk. Thirty percent (56/184; 43 susceptible, dose-dependent and 13 resistant) of isolates demonstrated reduced susceptibility to fluconazole. Only one (1%) isolate had reduced susceptibility to amphotericin B and six (3%) and three (2%) isolates had minimum inhibitory concentrations of >or=1 mg/L to voriconazole and caspofungin, respectively. Overall, 40% of patients died in-hospital for an annual mortality rate of 1.2 per 100,000. Conclusions Candida species are an important cause of invasive infection and patients with co-morbidities and extremes of age are at highest risk. Alternatives to fluconazole should be considered for initial empiric therapy in patients with severe invasive Candida species infections.

Although bloodstream infection commonly results in critical illness, population-based studies of the epidemiology of severe bloodstream infection are lacking. We sought to define the incidence and microbiology of severe bloodstream infection (bloodstream infection associated with intensive care unit admission within 48 hrs) and assess risk factors for acquisition and death.Population-based surveillance cohort.Multidisciplinary and cardiovascular surgical intensive care units.All adults with severe bloodstream infection in the Calgary Health Region (population approximately 1 million) during 2000-2002.None.Three hundred forty patients had 342 episodes of severe bloodstream infection (15.7 per 100,000 population/year). Several demographic and chronic conditions were significant risk factors for acquiring severe bloodstream infection (relative risk, 95% confidence interval) including ageor =65 yrs (7.0, 5.6-8.7), male gender (1.3, 1.1-1.6), urban residence (2.4, 1.2-5.6), hemodialysis (208.7, 142.9-296.3), diabetes mellitus (5.9, 4.4-7.8), alcoholism (5.6, 3.8-8.0), cancer (7.5, 5.3-10.3), and lung disease (3.8, 2.6-5.4). The most common etiologies were Staphylococcus aureus, Escherichia coli, and Streptococcus pneumoniae (3.0, 3.0, and 1.9 per 100,000/year, respectively). The case-fatality rate was 142 of 340 (42%) for an annual mortality rate of 6.5 per 100,000. Increased Acute Physiology and Chronic Health Evaluation II score (odds ratio, 1.1 per point; 95% confidence interval, 1.1-1.2) and presence of a comorbidity (odds ratio, 2.5; 95% confidence interval, 1.4-4.3) were significant independent predictors of death.Bloodstream infections are commonly severe enough to require management in an intensive care unit and are associated with a high mortality rate. Identification of risk factors for severe bloodstream infection may allow targeting of preventive efforts to individuals at greatest potential benefit.

A novel application of a rapid diagnostic technique for the detection of significant bacterial pathogens (>/=10(4) cfu/mL) in bronchoalveolar lavage (BAL) samples from critically ill ventilated patients is described. This rapid diagnostic assay (UTIscreen, Coral Biotechnology, San Diego, CA) utilizes a luciferin-luciferase reaction to detect bacterial adenosine triphosphate (ATP) and is currently commercially available for screening bacteriuria in urine specimens. One hundred and twenty-eight BAL samples were examined microscopically with Gram's stain and tested in parallel using the bacterial ATP assay and standard quantitative culture. The sensitivity (Sn), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) for the detection of bacteria >/=10(4) cfu/ml in BAL specimens for the bacterial ATP assay was 87%, 59%, 39%, and 94%, and for the Gram's stain was 73%, 65%, 39%, and 89%, respectively. The diagnostic utility was improved by combining the results of Gram's stain/bacterial ATP assay results with Sn, Sp, PPV, and NPV of 97%, 38%, 32%, and 97% respectively. A combined negative rapid test consisting of Gram's stain/bacterial ATP assay rules out significant bacteria in BAL samples with a high degree of certainty. Future studies are needed to clinically validate these observations.

Context.—Group B streptococcus (GBS) is the most common cause of early-onset neonatal sepsis in developed countries, and determination of the GBS colonization status in pregnant patients near term is essential for the provision of prophylactic measures to prevent early-onset disease. Objectives.—To determine if GBS recovery rates and/or result turnaround times for vaginal or combined vaginal/rectal swab specimens from pregnant patients near term are enhanced if swabs are inoculated initially onto selective versus nonselective agar media, in addition to the standard Centers for Disease Control and Prevention method. Design.—Prospective laboratory analysis. Setting.—Urban health region/centralized diagnostic microbiology laboratory. Patients.—Pregnant women presenting for routine obstetrical care and collection of vaginal or combined vaginal/rectal swab specimens for GBS testing at 35 to 37 weeks' gestation. Intervention.—Culture of specimens directly onto selective (5% sheep blood with colistin and nalidixic acid) or nonselective (5% sheep blood) agar media, in addition to LIM broth enrichment and terminal subculture. Main Outcome Measures.—Group B streptococcus recovery rate and culture result turnaround time. Results.—A total of 639 specimens were tested, with 128 (20%) positive for GBS. Sixty-three isolates were recovered on direct agar media at 24 hours, of which 16 (12.5%) were isolated on selective plates only. An additional 38 isolates were recovered at 48 hours from direct plates. Twenty-seven (21.1%) isolates that failed to grow on direct plates were recovered from the LIM broth subculture only. Three (2.3%) isolates not recovered from LIM broths were detected at 48 hours on the direct selective (2 isolates) and nonselective (1 isolate) agar plates. A 24-hour result turnaround time was achieved for 63 (49.2%) and 47 (36.7%) of the 128 culture-positive specimens for direct selective and nonselective plates, respectively (χ2 = 76.63, P < .001). Conclusions.—Use of direct selective agar media, in addition to LIM broth enrichment, for the determination of the GBS colonization status in pregnant patients near term results in decreased turnaround time for reporting positive results.

Invasive Pasteurella multocida infection, although uncommon, has been recognized to occur more frequently among patients with hepatic cirrhosis. This study reports a fatal case of bacteremic P. multocida empyema without pneumonia associated with refractory septic shock in a patient with both cirrhosis and asplenia.

Since the 1960s, group A streptococcus (GAS) has accounted for less than 1% of cases of community-acquired pneumonia. During the past 2 decades there has been a resurgence of invasive GAS infection, but no large study of GAS pneumonia has been performed.To determine the clinical and epidemiologic features of GAS pneumonia, we conducted prospective, population-based surveillance of all invasive GAS infection in residents of Ontario from January 1, 1992, through December 31, 1999.Of 2079 cases of invasive GAS infection, 222 (11%) represented GAS pneumonia. The incidence of GAS pneumonia ranged from 0.16 per 100 000 in 1992 to 0.35 per 100 000 in 1999. Most cases were community acquired (81%). Forty-four percent of nursing home-acquired cases occurred during outbreaks. The case fatality rate was 38% for GAS pneumonia, compared with 12% for the entire cohort with invasive GAS infection and 26% for patients with necrotizing fasciitis. The presence of streptococcal toxic shock syndrome (odds ratio, 19; 95% confidence interval, 8.4-42; P =.001) and increasing age (odds ratio per decade, 1.45; 95% confidence interval, 1.2-1.7; P.001) were associated with fatal outcome. Time to death was rapid, with a median of 2 days despite antimicrobial therapy and supportive measures.Group A streptococcal pneumonia is a common form of invasive GAS disease but remains an uncommon cause of community-acquired pneumonia. Progression is rapid despite appropriate therapy. The incidence is similar to, and the case fatality rate higher than, that of necrotizing fasciitis.

A prospective, population-based, surveillance study of invasive soft-tissue infections due to group A streptococci was conducted in Ontario, Canada, from 1992 through 1996. Demographic and clinical information was obtained by patient interview and chart review. Isolates were characterized by M protein and T agglutination typing. The incidence of necrotizing fasciitis (NF) increased from 0.08 cases per 100,000 population in 1992 to 0.49 cases per 100,000 population in 1995. The case-fatality rate was 13% (68 of 520 patients died). Hypotension and multiorgan dysfunction complicated 64 cases (12%), and NF complicated 119 cases (23%). Underlying diabetes, alcohol abuse, cancer, and cardiac and pulmonary disease increased the risk of disease. Prior use of nonsteroidal anti-inflammatory agents did not influence disease severity. All 197 patients without NF, underlying illness, and hypotension at presentation survived, as did 95 (99%) of 96 normotensive patients who were

We compared the presence and identities of isolates from blood culture samples obtained by percutaneous venipuncture with those of commensal skin organisms cultured from respective venipuncture sites after skin cleansing; 677 blood and skin site culture pairs from 488 infants were compared. Organisms grew in 58 blood cultures; nine of these cultures had corresponding venipuncture site cultures that also grew organisms. Forty-two blood culture isolates were coagulase-negative staphylococci; five of these were associated with similar venipuncture site cultures. According to restriction-endonuclease fingerprinting of chromosomal DNA and plasmid analysis, three pairs of blood and venipuncture site cultures were identical and two pairs were different. Thus only 7% (3/42) of coagulase-negative staphylococcal blood isolates were associated with identical contamination at the venipuncture site. We conclude that, if the venipuncture site has been carefully cleansed, the growth of coagulase-negative staphylococci in blood cultures of specimens from premature neonates indicates bacteremia rather than skin contamination in the vast majority of cases.

In a regional oncology hospital using cotrimoxazole (trimethoprim-sulphamethoxazole) prophylaxis during chemotherapy-induced neutropenia, a single strain ofEscherichia coli(indole negative) caused 15 of 27 episodes of Gram-negative rod bacteremia in 1987, and four of 32 such episodes in 1988. This biotype had not been recovered in 1986. Investigations during this ‘outbreak’ of bacteremias revealed enteric colonization with this strain ofE coliin 37% of patients on leukemia or bone marrow transplant wards and in several staff members in July 1987. In 1988, 11 of 32 Gram-negative rod bacteremias were secondary to other strains of indole positiveE coliof several different biotypes and plasmid profiles. Indole negative strains all exhibited low level trimethoprim resistance, whereas indole positive strains which subsequently appeared exhibited high level trimethoprim resistance. Failure of cotrimoxazole prophylaxis was initially due to the clonal dissemination of a single strain ofE coliwithin the institution, with the subsequent appearance of multipleE colistrains with probable differing genetic bases for their resistance.

Background Blood cultures are a gold standard specific test for diagnosing many infections. However, the low yield may limit their usefulness, particularly in low-risk populations. This study was conducted to assess the utility of blood cultures drawn from ambulatory outpatients. Methods Blood cultures drawn at community-based collection sites in the Calgary Health Region (population 1 million) in 2001 and 2002 were included in this study. These patients were analyzed by linkages to acute care health care databases for utilization of acute care facilities within 2 weeks of blood culture draw. Results 3102 sets of cultures were drawn from 1732 ambulatory outpatients (annual rate = 89.4 per 100,000 population). Significant isolates were identified from 73 (2.4%) sets of cultures from 51 patients, including Escherichia coli in 18 (35%) and seven (14%) each of Staphylococcus aureus and Streptococcus pneumoniae. Compared to patients with negative cultures, those with positive cultures were older (mean 49.6 vs. 40.1 years, p < 0.01), and more likely to subsequently receive care at a regional emergency department, outpatient antibiotic clinic, or hospital (35/51 vs. 296/1681, p < 0.0001). Of the 331 (19%) patients who received acute care treatment, those with positive cultures presented sooner after community culture draw (median 2 vs. 3 days, p < 0.01) and had longer median treatment duration (6 vs. 2 days, p < 0.01). Conclusion Blood cultures drawn in outpatient settings are uncommonly positive, but may define patients for increased intensity of therapy. Strategies to reduce utilization without excluding patients with positive cultures need to be developed for this patient population.

Background Community-onset (CO) bloodstream infections (BSI) are those BSI where the blood culture is drawn