668. Presence of the Narrow-Spectrum OXA-1 Beta-Lactamase Enzyme is not Associated with Elevated Ceftolozane-Tazobactam MIC Values among ESBL-Producing Escherichia coli Clinical Isolates (CANWARD, 2011-2018)

Background

Beta-lactam-beta-lactamase inhibitor combinations have been proposed as an alternative to carbapenems for the treatment of infections caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli as an antimicrobial stewardship initiative. However, in a recent randomized trial evaluating patients with bacteremia, presence of the narrow spectrum OXA-1 beta-lactamase enzyme among ESBL-producing Enterobacterales was associated with higher piperacillin-tazobactam MICs, and in turn excess mortality among patients treated with piperacillin-tazobactam relative to meropenem. The purpose of this study was to determine whether the in vitro activity of ceftolozane-tazobactam versus ESBL-producing E. coli is similarly compromised by the presence of OXA-1.

Methods

E. coli clinical isolates were obtained from patients evaluated at hospitals across Canada (January 2011 to December 2018) as part of an ongoing national surveillance study (CANWARD). ESBL production was confirmed using the Clinical and Laboratory Standards Institute phenotypic method. Susceptibility testing was carried out using custom broth microdilution panels, and all isolates underwent whole genome sequencing for beta-lactamase gene detection.

Results

In total, 485 ESBL-producing E. coli identified as part of the CANWARD study were included. The majority of isolates (91.3%; 443/485) harbored a CTX-M ESBL enzyme. OXA-1 was present in 39.6% (192/485) of isolates. OXA-1 was detected in 62.5% (187/299) of isolates with a CTX-M-15 ESBL enzyme versus only 2.7% (5/186) of isolates with other ESBL enzyme types. Ceftolozane-tazobactam MIC₅₀ and MIC₉₀ values were identical (0.25 µg/mL and 1 µg/mL, respectively) for the isolate subsets with and without OXA-1. Overall, 97.4% and 96.9% of isolates with and without OXA-1 remained susceptible (CLSI breakpoint) to ceftolozane-tazobactam.

Conclusion

The presence of OXA-1 among ESBL-producing E. coli clinical isolates was not associated with an elevation in MIC values for ceftolozane-tazobactam. These data support further evaluation of ceftolozane-tazobactam as an alternative to carbapenems for the treatment of infections caused by ESBL-producing E. coli, as is being done with the MERINO-3 trial.

Disclosures

George Zhanel, PhD, Merck: Grant/Research Support.

Antimicrobial resistance patterns of bacterial pathogens recovered from the urine of patients at Canadian hospitals from 2009 to 2020

Objectives

To investigate in vitro susceptibility patterns of bacterial pathogens recovered from the urine of outpatients (isolates from outpatient clinics or emergency departments) and hospital inpatients across Canada from 2009 to 2020 as part of the CANWARD study.

Methods

Canadian hospital microbiology laboratories submitted bacterial pathogens cultured from urine to the CANWARD study coordinating laboratory on an annual basis (January 2009 to December 2020). Antimicrobial susceptibility testing was performed by CLSI broth microdilution, with MICs interpreted by current CLSI breakpoints.

Results

In total, 4644 urinary pathogens were included in this study. Escherichia coli was recovered most frequently (53.3% of all isolates), followed by Enterococcus faecalis, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Staphylococcus aureus. Together, these six species accounted for 84.2% of study isolates. Nitrofurantoin demonstrated excellent in vitro activity versus E. coli, with 97.6% of outpatient and 96.1% of inpatient isolates remaining susceptible. In contrast, E. coli susceptibility rates were lower for ciprofloxacin (outpatient 79.5%, inpatient 65.9%) and trimethoprim/sulfamethoxazole (outpatient 75.2%, inpatient 73.5%). The percentage of E. coli isolates that were phenotypically positive for ESBL production significantly increased from 4.2% (2009-11) to 11.3% (2018-20). A similar although less pronounced temporal trend was observed with ESBL-producing K. pneumoniae.

Conclusions

E. coli was the pathogen most frequently recovered from the urine of Canadian patients, and the proportion of isolates that were ESBL producers increased over time. Susceptibility data presented here suggest that ciprofloxacin and trimethoprim/sulfamethoxazole may be suboptimal for the empirical treatment of complicated urinary infections.

1216. Presence of the Narrow-Spectrum OXA-1 Beta-lactamase Enzyme Is Associated with Elevated Piperacillin-Tazobactam MIC Values Among ESBL-producing Escherichia coli Clinical Isolates (CANWARD, 2007-2018)

Background

The clinical outcome of patients with bacteremia due to an extended-spectrum beta-lactamase (ESBL)-producing member of the family Enterobacteriaceae who are treated with piperacillin-tazobactam appears to depend, at least in part, on the piperacillin-tazobactam MIC. The purpose of this study was to determine whether there is any association between the MIC of piperacillin-tazobactam and presence of the narrow spectrum OXA-1 beta-lactamase enzyme among ESBL-producing Escherichia coli.

Methods

E. coli clinical isolates were obtained from patients evaluated at hospitals across Canada (January 2007 to December 2018) as part of an ongoing national surveillance study (CANWARD). ESBL production was confirmed using the Clinical and Laboratory Standards Institute phenotypic method. Susceptibility testing was carried out using custom broth microdilution panels, and all isolates underwent whole genome sequencing for beta-lactamase gene detection.

Results

In total, 671 ESBL-producing E. coli were identified as part of the CANWARD study. The majority of isolates (92.0%; 617/671) harbored a CTX-M ESBL enzyme. CTX-M-15 (62.3%; 418/671), CTX-M-27 (13.9%; 93/671), and CTX-M-14 (13.4%; 90/671) were the most common variants identified. The narrow spectrum OXA-1 beta-lactamase enzyme was present in 42.6% (286/671) of isolates. OXA-1 was detected in 66.3% (277/418) of isolates with a CTX-M-15 ESBL enzyme versus only 3.6% (9/253) of isolates with other ESBL enzyme types. The piperacillin-tazobactam MIC₅₀ and MIC₉₀ values were 8 µg/mL and 32 µg/mL for isolates that possessed the OXA-1 enzyme versus 2 μg/mL and 8 µg/mL for those that did not. The percentage of ESBL-producing E. coli isolates that were inhibited by a piperacillin-tazobactam MIC of ≤8 μg/mL was 68.5% for isolates that were OXA-1 positive and 93.8% for isolates that were OXA-1 negative.

Conclusion

The MIC₅₀ and MIC₉₀ values of piperacillin-tazobactam among ESBL-producing E. coli were higher for the subset of isolates that harbored a narrow spectrum OXA-1 beta-lactamase enzyme relative to the subset that did not. This association was primarily observed among ESBL-producers with the CTX-M-15 enzyme variant. OXA-1 was infrequently detected among isolates with other ESBL enzyme types.

Disclosures

George Zhanel, PhD, AVIR (Grant/Research Support)Iterum (Grant/Research Support)Merck (Grant/Research Support)Pfizer (Grant/Research Support)Sandoz (Grant/Research Support)Sunovion (Grant/Research Support)Venatorx (Grant/Research Support)Verity (Grant/Research Support)

In vitro activity of imipenem-relebactam against various resistance phenotypes/genotypes of Enterobacterales and Pseudomonas aeruginosa isolated from patients across Canada as part of the CANWARD study, 2016-2019

Broth microdilution was used to determine the in vitro activities of imipenem-relebactam and comparators versus 4260 Enterobacterales and 1324 Pseudomonas aeruginosa clinical isolates. Excluding Serratia marcescens, 96.7% to 100% of Enterobacterales species were susceptible to imipenem-relebactam. Susceptibility of P. aeruginosa isolates to imipenem-relebactam and imipenem was 91.3% and 59.1%, respectively.

128. Adequacy of Commonly Prescribed Antimicrobials for Empiric Coverage of Gram-Negative Bacterial Pathogens Recovered from the Bloodstream of Patients Attending Emergency Rooms in Canada: Analysis of Data from the CANWARD Study, 2007 to 2018

Background

Inadequate empiric antimicrobial therapy for Gram-negative bacteremia is associated with adverse clinical outcomes. The purpose of this study was to evaluate the proportion of Gram-negative bacterial isolates recovered from the bloodstream of patients attending Canadian emergency rooms (ERs) that remain susceptible to commonly prescribed antimicrobials.

Methods

Annually from 2007 to 2018, sentinel hospitals across Canada collected bloodstream isolates from patients attending ERs as part of the CANWARD study. Susceptibility testing was performed using broth microdilution as described by CLSI (data analysis limited to Gram-negative bacteria in the top 10 pathogens), with current CLSI breakpoints applied. Extended-spectrum β-lactamase (ESBL)-producing isolates were confirmed using the CLSI disk diffusion method.

Results

Gram-negative bacteria among the top 10 bloodstream pathogens for patients seen at ERs across Canada were: Escherichia coli (n = 2,414), Klebsiella pneumoniae (n = 573), Pseudomonas aeruginosa (n = 211), Proteus mirabilis (n = 119), and Enterobacter cloacae (n = 114). Aggregate susceptibility of these isolates to common antimicrobials was as follows (% susceptible [S]): meropenem 99.4% S, piperacillin–tazobactam 98.5% S, gentamicin 93.3% S, ceftriaxone 88.1% S, ciprofloxacin 81.4% S, TMP-SMX 73.5% S. The most active antimicrobials evaluated vs. E. coli were meropenem (100% S), piperacillin–tazobactam (98.8% S), and ceftriaxone (93.3% S). Ceftriaxone susceptibility among E. coli isolates declined from 95.4% in 2007 to 89.8% in 2018. The average proportion of E. coli isolates that harbored an ESBL enzyme increased from 3.4% in the first three study years to 8.4% in the last three study years. The most active antimicrobials evaluated vs. K. pneumoniae isolates were meropenem (99.7% S), piperacillin–tazobactam (98.8% S), gentamicin (97.7% S), and ceftriaxone (96.9% S).

Conclusion

The most consistently active antimicrobials for empiric treatment of patients at Canadian ERs with Gram-negative bacteremia are meropenem and piperacillin–tazobactam. Ceftriaxone susceptibility among E. coli has declined over the last 12 years, mostly related to an increase in ESBL-producing isolates.

Disclosures

All authors: No reported disclosures.

708. In Vitro Activity of Plazomicin vs. Clinical Isolates of Gram-Negative Bacilli, Including Aminoglycoside Nonsusceptible and Multidrug-Resistant Subsets, Recovered from Patients Across Canada as Part of the CANWARD study, 2011–2018

Background

Plazomicin (PLZ) is a next-generation aminoglycoside currently approved by the US FDA for the treatment of complicated urinary tract infections, including pyelonephritis. The purpose of this study was to evaluate the in vitro activity of PLZ against a large collection of Gram-negative bacilli obtained from patients attending Canadian hospitals.

Methods

Annually from 2011 to 2018, sentinel hospitals across Canada submitted blood, respiratory, urine, and wound isolates from patients attending ERs, medical and surgical wards, hospital clinics, and ICUs (CANWARD). Susceptibility testing was performed using broth microdilution (and breakpoints) as described by CLSI (FDA breakpoints used for PLZ).

Results

See table.

S, susceptible; NS, nonsusceptible; ESBL, extended-spectrum β-lactamase; MDR, multidrug-resistant (NS to antimicrobials from three or more classes); n.d., not defined.

Conclusion

PLZ demonstrated excellent in vitro activity vs. E. coli and K. pneumoniae clinical isolates, including aminoglycoside NS, ESBL-positive, and MDR subsets.

Disclosures

All authors: No reported disclosures.

Prevalence, predictors, and consequences of inappropriate empiric antimicrobial therapy for complicated urinary tract and intra-abdominal infections in Winnipeg hospitals

Information on inappropriate empiric antimicrobial therapy (ET) in Canadian hospitals is scarce. All Manitobans 18 years of age and over who were admitted to a hospital in Winnipeg with a complicated urinary tract infection (cUTI) or complicated intra-abdominal infection (cIAI) from January 2006 to December 2014 were eligible for inclusion in this cohort study. The prevalence of inappropriate ET was 11% for cUTI patients and 9% for cIAI patients. The risk of receiving inappropriate ET was higher for older patients (cUTI patients 65 or older had 2-fold increased risk compared to younger patients; odds ratio 2.1, 95% confidence interval 1.3-3.6; this was 1.6 [0.7-3.5] for cIAI patients) and those hospitalized in the previous year: 1.5 (1.0-2.4) in cUTIs and 1.5 (0.6-3.4) in cIAIs. The risk for a hospital stay over 3 weeks was increased for inappropriate ET in cUTI patients, 2.3 (1.4-3.7), but not in cIAI patients, 0.9 (0.4-2.1).

2383. In Vitro Activity of Ceftolozane–Tazobactam in Comparison With Ceftazidime–Avibactam vs. Antimicrobial Non-Susceptible Pseudomonas aeruginosa Clinical Isolates, Including Multidrug-Resistant and Extensively Drug-Resistant Subsets: CANWARD, 2007–2017

Background

Methods

Results

Conclusion

Disclosures

In Vitro Activity of Newer Antimicrobials and Relevant Comparators Vs. 349 Stenotrophomonas maltophilia Clinical Isolates Obtained from Patients in Canadian Hospitals (CANWARD, 2011–2016)

Background

Stenotrophomonas maltophilia is a non-fermentative gram-negative bacillus that has emerged as an important opportunistic pathogen among hospitalized, debilitated patients. Treatment options for infections caused by this organism are limited because it is intrinsically resistant to antimicrobials from multiple different classes. The purpose of this study was to evaluate the in vitro activity of several newer antimicrobial agents (ceftazidime-avibactam [CZA], ceftolozane-tazobactam [C/T], moxifloxacin [MXF], tigecycline [TGC]) and relevant comparators [e.g., trimethoprim-sulfamethoxazole [TMP-SMX]) against a large collection of S. maltophilia clinical isolates obtained as part of an ongoing national surveillance study (CANWARD, 2011–2016).

Methods

From January 2011 to December 2016, inclusive, 12 to 15 sentinel hospitals across Canada submitted clinical isolates from patients attending ERs, medical and surgical wards, hospital clinics, and ICUs (CANWARD). Each center was asked to annually submit clinical isolates (consecutive, one per patient/infection site) from blood (100), respiratory (100), urine (25), and wound (25) infections. Susceptibility testing was performed using broth microdilution as described by CLSI. MICs were interpreted using CLSI breakpoints, where available.

Results

349 S. maltophilia clinical isolates were obtained as a part of CANWARD (86% from a respiratory source). The susceptibility profile of these isolates is presented below.

Conclusion

TMP-SMX continues to demonstrate excellent in-vitro activity against S. maltophilia clinical isolates. MXF and TGC may also prove useful in the treatment of infections caused by this pathogen.

Disclosures

G. Zhanel, Achaogen: Research relationship, Research support Astellas: Research relationship, Research support Merck Canada: Research relationship, Research support Merck USA: Research relationship, Research support Paratek Pharma: Research relationship, Research support Pharmascience: Research relationship, Research support Sunovion: Research relationship, Research support Tetraphase: Research relationship, Research support The Medicines Co.: Research relationship, Research support Zoetis: Research relationship, Research support

In Vitro Activity of Ceftolozane-Tazobactam vs. Antimicrobial Non-Susceptible Pseudomonas aeruginosa Clinical Isolates Obtained from Across Canada as Part of the CANWARD Study, 2008–2016

Background

Ceftolozane-tazobactam (C/T) is a novel β-lactam β-lactamase inhibitor combination with a broad spectrum of activity that includes Pseudomonas aeruginosa. The purpose of this study was to evaluate the in vitro activity of C/T and relevant comparators vs. a large collection of antimicrobial non-susceptible (NS) P. aeruginosa clinical isolates obtained from patients across Canada (CANWARD, 2008–2016).

Methods

From January 2008 to December 2016, inclusive, 12 to 15 sentinel hospitals across Canada submitted clinical isolates from patients attending ERs, medical and surgical wards, hospital clinics, and ICUs (CANWARD). Each center was asked to annually submit clinical isolates (consecutive, one per patient/infection site) from blood, respiratory, urine, and wound infections. Susceptibility testing was performed using broth microdilution as described by CLSI. Multidrug-resistant (MDR) P. aeruginosa were defined as isolates that tested NS to at least one antimicrobial from ≥3 classes. Extensively drug-resistant (XDR) P. aeruginosa were defined as isolates that tested NS to at least one antimicrobial from ≥5 classes.

Results

3229 P. aeruginosa isolates were obtained as a part of CANWARD. The in vitro activity of C/T and relevant comparators is presented below.

Conclusion

C/T demonstrated excellent in vitro activity vs. antimicrobial NS P. aeruginosa clinical isolates, including MDR, XDR, and meropenem NS subsets. It may prove useful in the treatment of infections caused by these organisms.

Disclosures

D. Hoban, Abbott: Research relationship, Research support Achaogen: Research relationship, Research support Astellas: Research relationship, Research support Merck Canada: Research relationship, Research support Merck USA: Research relationship, Research support Paratek Pharma: Research relationship, Research support Pharmascience: Research relationship, Research support Sunovion: Research relationship, Research support Tetraphase: Research relationship, Research support The Medicines Co.: Research relationship, Research support Zoetis: Research relationship, Research support; G. Zhanel, Achaogen: Research relationship, Research support Astellas: Research relationship, Research support Merck Canada: Research relationship, Research support Merck USA: Research relationship, Research support Paratek Pharma: Research relationship, Research support Pharmascience: Research relationship, Research support Sunovion: Research relationship, Research support Tetraphase: Research relationship, Research support The Medicines Co.: Research relationship, Research support Zoetis: Research relationship, Research support

Impact of Antivirals in the Prevention of Serious Outcomes Associated with Influenza in Hospitalized Canadian Adults: A Pooled Analysis from the Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN)

Background

Antiviral treatment of influenza in outpatient settings is associated with modest improvement in outcomes but benefit in inpatient settings remains unclear. We assessed the impact of antiviral treatment on the severe outcomes death and intensive care unit (ICU) admission and/or need for mechanical ventilation (MV) in hospitalized influenza patients.

Methods

Patients admitted to hospitals of the CIRN SOS Network with an acute respiratory illness from 2011/12–2013/14 who tested polymerase chain reaction (PCR) positive for influenza were included. Demographic and medical information were obtained from patient interview or the medical chart. Main outcomes of interest were ICU admission and/or need for MV, and death. Logistic regression with backwards stepwise selection was used to estimate odds ratios (ORs) and 95% confidence limits (CIs) for the association between antiviral use and severe outcomes overall, and stratified by time from symptom onset to antiviral start (<48hours, 48hours <5 days, 5–21 days).

Results

Over 3 influenza seasons, 4,679 patients were enrolled; 59% were aged ≥65 years, 52% were female, and 89% had a comorbidity. Influenza vaccination status was available for 4,019 (86%) patients, of whom 1,796 (45%) had received current season vaccine. Of 4,679 patients, 16% of patients were admitted to ICU and/or required MV and 9% died. Overall, 54% of hospitalized influenza patients received an antiviral; mean time from the onset of symptoms to antiviral start was 4.28 days (range: 0–21 days). Treatment with antivirals was associated with a significant reduction in admission to ICU and/or need for MV (OR = 0.10; 95% CI: 0.08–0.13; P < 0.001), but was not significantly associated with a reduction in death (P = 0.454) irrespective of time between symptom onset and start of antivirals.

Conclusion

In this study, treatment with antivirals in hospitalized patients with influenza was associated with a significant reduction in ICU admission and MV, even when initiated a mean of 4.28 days from symptom onset. Reduction in death was not demonstrated. These findings support current recommendations for antiviral use in hospitalized adults and suggest increased compliance with these guidelines may reduce morbidity and cost.

Disclosures

M. K. Andrew, GSK: Grant Investigator, Research grant; Pfizer: Grant Investigator, Research grant; Sanofi-Pasteur: Grant Investigator, Research grant; A. Chit, Sanofi pasteur: Employee, Salary; G. Dos Santos, GSK: Employee, Salary; Business and Decision Life Sciences (Contractor for GSK Vaccines): Independent Contractor, Salary; M. Elsherif, Canadian Institutes of Health Research: Investigator, Research grant; Public Health Agency of Canada: Investigator, Research grant; GSK: Investigator, Research grant; F. Haguinet, GSK: Employee, Salary; S. A. Halperin, GSK: Scientific Advisor, Consulting fee; GSK: Grant Investigator, Research grant; T. Hatchette, GSK: Grant Investigator, Grant recipient; Pfizer: Grant Investigator, Grant recipient; Abbvie: Speaker for a talk on biologics and risk of TB reactivation, Speaker honorarium; B. Ibarguchi, GSK: Employee, Salary; J. M. Langley, GSK: Investigator, Research grant; Canadian Institutes of Health Research: Investigator, Research grant; J. Mcelhaney, GSK: Scientific Advisor, Honorarium to institution; Sanofi pasteur: Scientific Advisor, Honorarium to institution; A. Mcgeer, Hoffman La Roche: Investigator, Research grant; GSK: Investigator, Research grant; Sanofi pasteur: Investigator, Research grant; J. Powis, Merck: Grant Investigator, Research grant; GSK: Grant Investigator, Research grant; Roche: Grant Investigator, Research grant; Synthetic Biologicals: Investigator, Research grant; M. Semret, GSK: Investigator, Research grant; Pfizer: Investigator, Research grant; V. Shinde, Novavax: Employee, Salary; GSK: Shareholder, Stocks; GSK: Employee, Salary; S. Trottier, Canadian Institutes of Health Research: Investigator, Research grant; L. Valiquette, GSK: Investigator, Research grant; S. McNeil, GSK: Contract Clinical Trials and Grant Investigator, Research grant; Merck: Contract Clinical Trials and Speaker’s Bureau, Speaker honorarium; Novartis: Contract Clinical Trials, No personal renumeration; Sanofi pasteur: Contract Clinical Trials, No personal renumeration

Antimicrobial susceptibility of 2906 Pseudomonasaeruginosa clinical isolates obtained from patients in Canadian hospitals over a period of 8 years: Results of the Canadian Ward surveillance study (CANWARD), 2008-2015

Pseudomonas aeruginosa is an important nosocomial pathogen. The purpose of this study was to evaluate the antimicrobial susceptibility profile of P. aeruginosa clinical isolates obtained from inpatients and outpatients at hospitals across Canada from January 2008 to December 2015 (CANWARD Study). Susceptibility testing was performed using broth microdilution, as described by the Clinical and Laboratory Standards Institute. In total, 2906 P. aeruginosa isolates were evaluated. The percentage of isolates susceptible to common antipseudomonal antimicrobials was: colistin 94.9%, amikacin 93.2%, piperacillin-tazobactam 84.3%, ceftazidime 83.1%, gentamicin 82.7%, meropenem 80.5%, ciprofloxacin 76.5%. In general, susceptibility to the antipseudomonal antimicrobials tested remained fairly stable or slightly improved (ciprofloxacin, gentamicin, colistin) over the 8year study period. Multidrug-resistant (MDR = non-susceptible to at least one antimicrobial from ≥3 classes) and extensively drug-resistant (XDR = non-susceptible to at least one antimicrobial from 5 classes) P. aeruginosa accounted for 14.5% and 2.6% of the isolates, respectively. Colistin remained active against 92.9% of MDR and 88.3% of XDR P. aeruginosa.