42936 pathogens from Canadian hospitals: 10 years of results (2007-16) from the CANWARD surveillance study

Real-life experience with IV dalbavancin in Canada; results from the CLEAR (Canadian LEadership on Antimicrobial Real-life usage) registry

OBJECTIVES

We report the use of IV dalbavancin in Canadian patients using data captured by the national CLEAR registry.

METHODS

The CLEAR registry uses the web-based data management program, REDCapTM (online survey https://rcsurvey.radyfhs.umanitoba.ca/surveys/?s=TPMWJX98HL) to facilitate clinicians entering details associated with their clinical experiences using IV dalbavancin.

RESULTS

Data were available for 40 patients. The most common infections treated were acute bacterial skin and skin structure infection (ABSSSI) (62.5% of patients), bone/joint infection (22.5%), bloodstream/vascular infection (7.5%) and endocarditis (5.0%). Dalbavancin was used as directed (75.0%) and empiric therapy (25.0%). MRSA was the most common identified pathogen (70.0%). Dalbavancin was used both in outpatient (e.g., emergency department) (65.0%), and inpatient treatment settings (e.g., hospital ward) (35.0%). Dalbavancin was used due to the convenience of a single dose treatment (77.5%) as well as to facilitate hospital discharge (7.5%). Dalbavancin was primarily used alone (90.0%), and most commonly using a single 1500 mg dose (77.5%). Microbiological success (pathogen eradicated or presumed eradicated) occurred in 88.2% of known cases, while clinical success (cure and/or improvement) occurred in 93.3% of known cases. No adverse events were reported.

CONCLUSIONS

In Canada, IV dalbavancin is used as both directed and empiric therapy to treat ABSSSI as well as off-label (bone/joint, bacteremia/vascular, endocarditis, device-related) infections. It is used in both outpatient and inpatient settings due primarily to its convenience as a single-dose treatment regimen and to facilitate early hospital discharge. Dalbavancin use is associated with high microbiological and clinical cure rates along with an excellent safety profile.

Exposure levels and target attainment of piperacillin/tazobactam in adult patients admitted to the intensive care unit: a prospective observational study

PURPOSE

The objective of this study was to evaluate the exposure and the pharmacodynamic target attainment of piperacillin/tazobactam (PTZ) in adult critically ill patients.

METHODS

We conducted a prospective observational study in the intensive care unit (ICU) of the Hôpital du Sacré-Cœur de Montréal (a Level I trauma centre in Montreal, QC, Canada) between January 2021 and June 2022. We included patients aged 18 yr or older admitted to the ICU who received PTZ by intravenous administration. Demographic and clinical characteristics were collected, and clinical scores were calculated. On study day 1 of antimicrobial therapy, three blood samples were collected at the following timepoints: one hour after PTZ dose administration and at the middle and at the end of the dosing interval. The sampling schedule was repeated on days 4 and 7 of therapy if possible. Samples were analyzed by ultra-high performance liquid chromatography with diode array detector to determine the total piperacillin concentration. Middle- and end-of-interval concentrations were used for target attainment analyses, and were defined as a concentration above the minimal inhibitory concentration of 16 mg·L-1, corresponding to the breakpoint of Enterobacteriaceae and Pseudomonas aeruginosa.

RESULTS

Forty-three patients were recruited and 202 blood samples were analyzed. The most prevalent dose was 3/0.375 g every six hours (n = 50/73 doses administered, 68%) with a 30-min infusion. We observed marked variability over the three sampling timepoints, and the median [interquartile range] piperacillin concentrations at peak, middle of interval, and end of interval were 109.4 [74.0-152.3], 59.3 [21.1-74.4], and 25.3 [6.8-44.6] mg·L-1, respectively. When assessing target attainment, 37% of patients did not reach the efficacy target of a trough concentration of 16 mg·L-1. The majority of patients who were underexposed were patients with normal to augmented renal clearance.

CONCLUSION

In this prospective observational study of adult ICU patients receiving intravenous PTZ, a large proportion had subtherapeutic concentrations of piperacillin. This was most notable in patients with normal to augmented renal clearance. More aggressive dosage regimens may be required for this subpopulation to ensure attainment of efficacy targets.

Phylogenomic and phenotypic analyses highlight the diversity of antibiotic resistance and virulence in both human and non-human Acinetobacter baumannii

Acinetobacter baumannii is a Gram-negative, opportunistic pathogen that causes infections in the immunocompromised. With a high incidence of muti-drug resistance, carbapenem-resistant A. baumannii is designated as a priority 1 pathogen by the WHO. The current literature has expertly characterized clinical isolates of A. baumannii. As the challenge of these infections has recently been classified as a One Health issue, we set out to explore the diversity of isolates from human and non-clinical sources, such as agricultural surface water, urban streams, various effluents from wastewater treatment plants, and food (tank milk); and, importantly, these isolates came from a wide geographic distribution. Phylogenomic analysis considering almost 200 isolates showed that our diverse set is well-differentiated from the main international clones of A. baumannii. We discovered novel sequence types in both hospital and non-clinical settings and five strains that overexpress the resistance-nodulation-division efflux pump adeIJK without changes in susceptibility reflected by this overexpression. Furthermore, we detected a bla ADC-79 in a non-human isolate despite its sensitivity to all antibiotics. There was no significant differentiation between the virulence profiles of clinical and non-clinical isolates in the Galleria mellonella insect model of virulence, suggesting that virulence is neither dependent on geographic origin nor isolation source. The detection of antibiotic resistance and virulence genes in non-human strains suggests that these isolates may act as a genetic reservoir for clinical strains. This endorses the notion that in order to combat multi-drug-resistant infection caused by A. baumannii, a One Health approach is required, and a deeper understanding of non-clinical strains must be achieved.IMPORTANCEThe global crisis of antibiotic resistance is a silent one. More and more bacteria are becoming resistant to all antibiotics available for treatment, leaving no options remaining. This includes Acinetobacter baumannii. This Gram-negative, opportunistic pathogen shows a high frequency of multi-drug resistance, and many strains are resistant to the last-resort drugs carbapenem and colistin. Research has focused on strains of clinical origin, but there is a knowledge gap regarding virulence traits, particularly how A. baumannii became the notorious pathogen of today. Antibiotic resistance and virulence genes have been detected in strains from animals and environmental locations such as grass and soil. As such, A. baumannii is a One Health concern, which includes the health of humans, animals, and the environment. Thus, in order to truly combat the antibiotic resistance crisis, we need to understand the antibiotic resistance and virulence gene reservoirs of this pathogen under the One Health continuum.

Moving towards a standardized definition of antimicrobial resistance: a comparison of the antimicrobial susceptibility profile of difficult-to-treat resistance (DTR) versus multidrug-resistant (MDR) Pseudomonas aeruginosa clinical isolates (CANWARD, 2016-2021)

Pseudomonas aeruginosa clinical isolates demonstrating difficult-to-treat resistance (DTR) and multidrug-resistant (MDR) phenotypes were evaluated by broth microdilution. Susceptibility was lower for all antimicrobials versus DTR relative to MDR isolates. Ceftazidime-avibactam, ceftolozane-tazobactam, and imipenem-relebactam susceptibility was 35.9%, 64.5%, and 47.0% for DTR isolates and 60.5%, 80.6%, and 71.5% for MDR isolates.

Lower Urinary Tract Inflammation and Infection: Key Microbiological and Immunological Aspects

The urinary system, primarily responsible for the filtration of blood and waste, is affected by several infectious and inflammatory conditions. Focusing on the lower tract, this review outlines the physiological and immune landscape of the urethra and bladder, addressing key immunological and microbiological aspects of important infectious/inflammatory conditions. The conditions addressed include urethritis, interstitial cystitis/bladder pain syndrome, urinary tract infections, and urosepsis. Key aspects of each condition are addressed, including epidemiology, pathophysiology, and clinical considerations. Finally, therapeutic options are outlined, highlighting gaps in the knowledge and novel therapeutic approaches.

Discovery of an adjuvant that resensitizes polymyxin B-resistant bacteria

Infections caused by antibiotic-resistant bacteria are a major threat to health, increasing mortality rates and straining health systems worldwide. Adjuvants targeted to beta-lactamase function are able to resensitize bacteria to beta-lactam antibiotics, but there is comparatively little research into the use of adjuvants against other resistance phenotypes. In this study, we performed a high-throughput screen of 74 natural products to identify adjuvants that synergized with antibiotics to eradicate resistant Gram-negative bacteria. From this, we identified six adjuvant hits which restored growth inhibition when combined with the relevant antibiotic, and pursued a lead candidate, perforone, which possessed selective adjuvant activity in combination with polymyxin B against polymyxin-resistant Escherichia coli cells. These results suggest that pairing adjuvants with antibiotics could be a useful general intervention against resistant bacteria, helping to mitigate the effects of antimicrobial resistance.

Hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP) in Canada: treatment update and the role of new IV antimicrobials

INTRODUCTION

Hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP) continue to be common infections causing significant morbidity and mortality worldwide. The timely initiation of empiric antimicrobial therapy is essential. In this paper, we provide a focused expert opinion on the current and potential empiric antimicrobial treatment options in HABP and VABP in Canada influenced by antimicrobial resistance impacting the use of older agents as well as available new intravenous (IV) antimicrobials.

AREAS COVERED

The authors discuss treatment options for HABP and VABP in Canada. In addition, we focus on the potential role of new IV antimicrobials recently introduced to Canada. A literature search of HABP and VABP treatments was performed via PubMed (up to March 2023), using the following key words: monotherapy, combination therapy, aminoglycosides, carbapenems, cephalosporins, fluoroquinolones, penicillins as well as amoxicillin/clavulanate, ceftobiprole, ceftolozane/tazobactam, dalbavancin, and fosfomycin.

EXPERT OPINION

Empiric antimicrobial treatment for HABP and VABP in Canada continues to focus on both the severity of illness and the presence/absence of patient risk factors for antimicrobial resistance. The role of new IV antimicrobials in the empiric treatment for HABP and VABP depends on their antimicrobial activity and published data on efficacy and safety and influenced by Health Canada-approved indications.

A nested cohort 5-year Canadian surveillance of Gram-negative antimicrobial resistance for optimized antimicrobial therapy

We analyzed 5 years (2016-2020) of nested Canadian data from the Study for Monitoring Antimicrobial Resistance Trends (SMART) to identify pathogen predominance and antimicrobial resistance (AMR) patterns of adult Gram-negative infections in Canadian health care and to complement other public surveillance programs and studies in Canada. A total of 6853 isolates were analyzed from medical (44%), surgical (18%), intensive care (22%) and emergency units (15%) and from respiratory tract (36%), intra-abdominal (25%), urinary tract (24%) and bloodstream (15%) infections. Overall, E. coli (36%), P. aeruginosa (18%) and K. pneumoniae (12%) were the most frequent isolates and P. aeruginosa was the most common respiratory pathogen. 18% of Enterobacterales species were ESBL positive. Collective susceptibility profiles showed that P. aeruginosa isolates were highly susceptible (> 95%) to ceftolozane/tazobactam and colistin, though markedly less susceptible (58-74%) to other antimicrobials tested. Multi-drug resistance (MDR) was present in 10% of P. aeruginosa isolates and was more frequent in those from respiratory infections and from ICU than non-ICU locations. Of P. aeruginosa isolates that were resistant to combinations of ceftazidime, piperacillin/tazobactam and meropenem, 73-96% were susceptible to ceftolozane/tazobactam over the period of the study. These national data can now be combined with clinical prediction rules and genomic data to enable expert antimicrobial stewardship applications and guide treatment policies to optimize adult patient care.

Roles of inter- and intramolecular tryptophan interactions in membrane-active proteins revealed by racemic protein crystallography

Tryptophan is frequently found on the surface of membrane-associated proteins that interact with the lipid membrane. However, because of their multifaceted interactions, it is difficult to pinpoint the structure-activity relationship of each tryptophan residue. Here, we describe the use of racemic protein crystallography to probe dedicated tryptophan interactions of a model tryptophan-rich bacteriocin aureocin A53 (AucA) by inclusion and/or exclusion of potential ligands. In the presence of tetrahedral anions that are isosteric to the head group of phospholipids, distinct tryptophan H-bond networks were revealed. H-bond donation by W40 was critical for antibacterial activity, as its substitution by 1-methyltryptophan resulted in substantial loss of activity against bacterial clinical isolates. Meanwhile, exclusion of tetrahedral ions revealed that W3 partakes in formation of a dimeric interface, thus suggesting that AucA is dimeric in solution and dissociated to interact with the phosphate head group in the presence of the lipid membrane. Based on these findings, we could predict the tryptophan residue responsible for activity as well as the oligomeric state of a distant homologue lacticin Q (48%).

Emergence of ADC-5 Cephalosporinase in environmental Acinetobacter baumannii from a German tank milk with a novel Sequence Type

Bacteria resistant to antibiotics arguably pose the greatest threat to human health in the twenty-first century. One such bacterium that typifies antibiotic resistance is Acinetobacter baumannii . Frequently, hospital strains of A. baumannii display multidrug resistant (MDR) or extensively drug resistant (XDR) phenotypes, often requiring the use of last resort antibiotics for treatment. In addition to hospital settings, A. baumannii has been isolated from many highly divergent sources including wastewater treatment plant effluent, soil, and agricultural run-off with global distribution. However, such isolates remain poorly characterized. In this study, we characterized a strain of A. baumannii, AB341-IK15, isolated from bulk tank milk in Germany that demonstrated resistance to ceftazidime and intermediate resistance to ceftriaxone and piperacillin/tazobactam. Further genetic characterization identified an ADC-5 cephalosporinase, first incidence in an environmental isolate; and an OXA-408 oxacillinase that may contribute to this phenotype. Interestingly, AB341-IK15 is of a novel sequence type. This research underscores the importance of studying isolates of A. baumannii of non-clinical origin to understand the antibiotic resistance and virulence potential of environmental isolates of A. baumannii as well to understand the diversity of this species.

Opposites Attract: Electrostatically Driven Loading of Antimicrobial Peptides into Phytoglycogen Nanocarriers

Antimicrobial peptides, such as GL13K, have a high binding selectivity toward bacterial membranes, while not affecting healthy mammalian cells at therapeutic concentrations. However, delivery of these peptides is challenging since they are susceptible to proteolytic hydrolysis and exhibit poor cellular uptake. A protective nanocarrier is thus proposed to overcome these obstacles. We investigate the potential to employ biodegradable phytoglycogen nanoparticles as carriers for GL13K using a simple loading protocol based on electrostatic association rather than chemical conjugation, eliminating the need for control of chemical cleavage for release of the peptide in situ. Both the native (quasi-neutral) and carboxymethylated (anionic) phytoglycogen were evaluated for their colloidal stability, loading capacity, and release characteristics. We show that the anionic nanophytoglycogen carries a greater cationic GL13K load and exhibits slower release kinetics than native nanophytoglycogen. Isotope exchange measurements demonstrate that the antimicrobial peptide is entrapped in the pores of the dendritic-like macromolecule, which should provide the necessary protection for delivery. Importantly, the nanoformulations are active against a Pseudomonas aeruginosa clinical isolate at concentrations comparable to those of the free peptide and representative, small molecule antibiotics. The colloidal nanocarrier preserves peptide stability and antimicrobial activity, even after long periods of storage (at least 8 months).

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.

In vitro activity of sulopenem against 1880 bacterial pathogens isolated from Canadian patients with urinary tract infections (CANWARD, 2014-21)

INTRODUCTION

There are limited oral antimicrobial options for the treatment of urinary infections caused by ESBL-producing and MDR Enterobacterales. Sulopenem is an investigational thiopenem antimicrobial that is being developed as both an oral and IV formulation. The purpose of this study was to evaluate the in vitro activity of sulopenem versus bacterial pathogens recovered from the urine of patients admitted to or assessed at hospitals across Canada (CANWARD).

MATERIALS AND METHODS

The in vitro activity of sulopenem and clinically relevant comparators was determined for 1880 Gram-negative and Gram-positive urinary isolates obtained as part of the CANWARD study (2014 to 2021) using the CLSI broth microdilution method.

RESULTS

Sulopenem demonstrated excellent in vitro activity versus members of the Enterobacterales, with MIC90 values ranging from 0.06 to 0.5 mg/L for all species tested. Over 90% of ESBL-producing, AmpC-producing and MDR (not susceptible to ≥1 antimicrobial from ≥3 classes) Escherichia coli were inhibited by ≤0.25 mg/L of sulopenem. Sulopenem had an identical MIC90 to meropenem for ESBL-producing and MDR E. coli. The MIC90 of sulopenem and meropenem versus MSSA was 0.25 mg/L. Sulopenem was not active in vitro versus Pseudomonas aeruginosa (similar to ertapenem), and it demonstrated poor activity versus Enterococcus faecalis (similar to meropenem).

CONCLUSIONS

Sulopenem demonstrated excellent in vitro activity versus bacterial pathogens recovered from the urine of Canadian patients. These data suggest that sulopenem may have a role in the treatment of urinary infections caused by antimicrobial-resistant Enterobacterales, but additional clinical studies are required.

A One Health Genomic Investigation of Gentamicin Resistance in Escherichia coli from Human and Chicken Sources in Canada, 2014 to 2017

We investigated whether gentamicin resistance (Gen^r) in Escherichia coli isolates from human infections was related to Gen^r E. coli in chicken and whether resistance may be due to coselection from use of lincomycin-spectinomycin in chickens on farms. Whole-genome sequencing was performed on 483 Gen^r E. coli isolates isolated between 2014 and 2017. These included 205 human-source isolates collected by the Canadian Ward (CANWARD) program and 278 chicken-source isolates: 167 from live/recently slaughtered chickens (animals) and 111 from retail chicken meat collected by the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS). The predominant Gen^r gene was different in human and chicken sources; however, both sources carried aac(3)-IId, aac(3)-VIa, and aac(3)-IVa. Forty-one percent of human clinical isolates of Gen^r E. coli contained a bla_CTX-M extended-spectrum beta-lactamase (ESBL) gene (84/205), and 53% of these were sequence type 131 (ST131). Phylogenomic analysis revealed a high diversity of Gen^r isolates; however, there were three small clusters of closely related isolates from human and chicken sources. Gen^r and spectinomycin resistance (Spec^r) genes were colocated in 148/167 (89%) chicken animal isolates, 94/111 (85%) chicken retail meat isolates, and 137/205 (67%) human-source isolates. Long-read sequencing of 23 isolates showed linkage of the Gen^r and Spec^r genes on the same plasmid in 14/15 (93%) isolates from chicken(s) and 6/8 (75%) isolates from humans. The use of lincomycin-spectinomycin on farms may be coselecting for gentamicin-resistant plasmids in E. coli in broiler chickens; however, Gen^r isolates and plasmids were mostly different in chickens and humans.

In Vitro Activity of Cefiderocol against Extensively Drug-Resistant Pseudomonas aeruginosa: CANWARD, 2007 to 2019

Cefiderocol was evaluated by broth microdilution versus 1,050 highly antimicrobial-resistant Pseudomonas aeruginosa clinical isolates from the CANWARD study (2007 to 2019). Overall, 98.3% of isolates remained cefiderocol susceptible (MIC, ≤4 μg/mL), including 97.4% of extensively drug-resistant (XDR) (n = 235) and 97.9% of multidrug-resistant (MDR) (n = 771) isolates. Most isolates testing not susceptible to ceftolozane-tazobactam, ceftazidime-avibactam, and imipenem-relebactam remained susceptible to cefiderocol. In vitro data suggest that cefiderocol may be a treatment option for infections caused by MDR and XDR P. aeruginosa. IMPORTANCE After testing cefiderocol against a large collection of clinical isolates of highly antimicrobial-resistant Pseudomonas aeruginosa, we report that cefiderocol is active versus 97.4% of extensively drug-resistant (XDR) and 97.9% of multidrug-resistant (MDR) (n = 771) isolates. These data show that cefiderocol may be a treatment option for infections caused by MDR and XDR P. aeruginosa.

In vitro activity of fosfomycin against bacterial pathogens isolated from urine specimens in Canada from 2007 to 2020: CANWARD surveillance study

BACKGROUND

Multiple susceptible breakpoints are published to interpret fosfomycin MICs: ≤64 mg/L for Escherichia coli and Enterococcus faecalis grown from urine (CLSI M100); ≤32 mg/L for Enterobacterales and staphylococci when parenteral fosfomycin is prescribed (EUCAST); and ≤8 mg/L for uncomplicated urinary tract infection with E. coli when oral fosfomycin is used (EUCAST). Clinical laboratories are frequently requested to test fosfomycin against antimicrobial-resistant urinary isolates not included in standard documents.

METHODS

The in vitro activity of fosfomycin was determined using the CLSI agar dilution method for a 2007-20 collection of clinically significant Gram-negative (3656 Enterobacterales; 140 Pseudomonas aeruginosa) and Gram-positive (346 E. faecalis; 94 Staphylococcus aureus) urinary isolates from the CANWARD surveillance study. Comparator agents were tested using CLSI broth microdilution.

RESULTS

Using the CLSI MIC breakpoint (≤64 mg/L), 99.2% of E. coli (n = 2871; MIC90, 4 mg/L), including 96.7% of ESBL-positive isolates, were fosfomycin susceptible. Similarly, 95.8% of E. coli, including 95.2% of ESBL-positive isolates, were fosfomycin susceptible at ≤8 mg/L (EUCAST oral susceptible MIC breakpoint). All other species of Enterobacterales (except Citrobacter freundii) and P. aeruginosa had higher fosfomycin MICs (MIC90s, 64 to >512 mg/L) than E. coli. Using published breakpoints, 88.4% of E. faecalis (MIC ≤64 mg/L) and 97.9% of S. aureus (MIC ≤32 mg/L) isolates were fosfomycin susceptible.

CONCLUSIONS

Fosfomycin demonstrated in vitro activity against frequently encountered Gram-positive and Gram-negative urinary pathogens; however, the extrapolation of current CLSI and EUCAST MIC breakpoints to pathogens not specified by standard methods requires further study and is currently not recommended.

Applying fluorescent dye assays to discriminate Escherichia coli chlorhexidine resistance phenotypes from porin and mlaA deletions and efflux pumps

Bacterial resistance to the antiseptic chlorhexidine (CHX), is a growing problem, recently shown to be caused by deleterious mutations to the phospholipid transport system component (mlaA) as well as efflux pump overexpression. Comparisons of CHX resistance mechanisms, such as porin deletions (ompCF), and over-expressed efflux pumps (acrB, qacE, aceI), are lacking and may be distinguishable using antiseptic rapid fluorescent dye testing assays. Using E. coli K-12 CHX adapted isolates (CHXR1), gene deletion mutants, and over-expressed transformants the phenotypes of these CHX resistance genes were compared using antimicrobial susceptibility tests (AST), rapid fluorescent propidium iodide dye-based membrane integrity assays (RFDMIA), and scanning electron microscopy (SEM). AST findings showed CHXR1, ΔacrB, ΔompCF, and transformants pCA24N-aceI and pCA24N-mlaA conferred greater (two to fourfold) MIC changes when compared to matched controls. Examination of these mutants/transformants using CHX RFDMIA showed that porin dual-deletions (ΔompCF) and mlaA alterations (ΔmlaA; pCA24N-mlaA, CHXR1) were distinguishable from controls. Results for over-expressed (pMS119EH-aceI) and deleted (ΔacrB) efflux pump RFDMIA could not be distinguished with propidium iodide, only with ethidium bromide, suggesting propidium iodide is better suited for detecting porin and mlaA associated CHX resistance mechanisms. SEM of CHXR1 and unadapted E. coli cells exposed to increasing CHX concentrations revealed that CHX does not visibly damage cell envelope integrity at any tested concentration but did identify elongated CHXR1 cells. ΔmlaA confers similar levels of CHX resistance as efflux overexpression and porin deletions, however, only outer membrane-altering porin and mlaA deletions can be reliably distinguished using RFDMIA.

An Update of Mobile Colistin Resistance in Non-Fermentative Gram-Negative Bacilli

Colistin, the last resort for multidrug and extensively drug-resistant bacterial infection treatment, was reintroduced after being avoided in clinical settings from the 1970s to the 1990s because of its high toxicity. Colistin is considered a crucial treatment option for Acinetobacter baumannii and Pseudomonas aeruginosa, which are listed as critical priority pathogens for new antibiotics by the World Health Organization. The resistance mechanisms of colistin are considered to be chromosomally encoded, and no horizontal transfer has been reported. Nevertheless, in November 2015, a transmissible resistance mechanism of colistin, called mobile colistin resistance (MCR), was discovered. Up to ten families with MCR and more than 100 variants of Gram-negative bacteria have been reported worldwide. Even though few have been reported from Acinetobacter spp. and Pseudomonas spp., it is important to closely monitor the epidemiology of mcr genes in these pathogens. Therefore, this review focuses on the most recent update on colistin resistance and the epidemiology of mcr genes among non-fermentative Gram-negative bacilli, especially Acinetobacter spp. and P. aeruginosa.

Sulopenem: An Intravenous and Oral Penem for the Treatment of Urinary Tract Infections Due to Multidrug-Resistant Bacteria

Sulopenem (formerly known as CP-70,429, and CP-65,207 when a component of a racemic mixture with its R isomer) is an intravenous and oral penem that possesses in vitro activity against fluoroquinolone-resistant, extended spectrum β-lactamases (ESBL)-producing, multidrug-resistant (MDR) Enterobacterales. Sulopenem is being developed to treat patients with uncomplicated and complicated urinary tract infections (UTIs) as well as intra-abdominal infections. This review will focus mainly on its use in UTIs. The chemical structure of sulopenem shares properties of penicillins, cephalosporins, and carbapenems. Sulopenem is available as an oral prodrug formulation, sulopenem etzadroxil, which is hydrolyzed by intestinal esterases, resulting in active sulopenem. In early studies, the S isomer of CP-65,207, later developed as sulopenem, demonstrated greater absorption, higher drug concentrations in the urine, and increased stability against the renal enzyme dehydropeptidase-1 compared with the R isomer, which set the stage for its further development as a UTI antimicrobial. Sulopenem is active against both Gram-negative and Gram-positive microorganisms. Sulopenem's β-lactam ring alkylates the serine residues of penicillin-binding protein (PBP), which inhibits peptidoglycan cross-linking. Due to its ionization and low molecular weight, sulopenem passes through outer membrane proteins to reach PBPs of Gram-negative bacteria. While sulopenem activity is unaffected by many β-lactamases, resistance arises from alterations in PBPs (e.g., methicillin-resistant Staphylococcus aureus [MRSA]), expression of carbapenemases (e.g., carbapenemase-producing Enterobacterales and in Stenotrophomonas maltophilia), reduction in the expression of outer membrane proteins (e.g., some Klebsiella spp.), and the presence of efflux pumps (e.g., MexAB-OprM in Pseudomonas aeruginosa), or a combination of these mechanisms. In vitro studies have reported that sulopenem demonstrates greater activity than meropenem and ertapenem against Enterococcus faecalis, Listeria monocytogenes, methicillin-susceptible S. aureus (MSSA), and Staphylococcus epidermidis, as well as similar activity to carbapenems against Streptococcus agalactiae, Streptococcus pneumoniae, and Streptococcus pyogenes. With some exceptions, sulopenem activity against Gram-negative aerobes was less than ertapenem and meropenem but greater than imipenem. Sulopenem activity against Escherichia coli carrying ESBL, CTX-M, or Amp-C enzymes, or demonstrating MDR phenotypes, as well as against ESBL-producing Klebsiella pneumoniae, was nearly identical to ertapenem and meropenem and greater than imipenem. Sulopenem exhibited identical or slightly greater activity than imipenem against many Gram-positive and Gram-negative anaerobes, including Bacteroides fragilis. The pharmacokinetics of intravenous sulopenem appear similar to carbapenems such as imipenem-cilastatin, meropenem, and doripenem. In healthy subjects, reported volumes of distribution (V_d) ranged from 15.8 to 27.6 L, total drug clearances (CL_T) of 18.9-24.9 L/h, protein binding of approximately 10%, and elimination half-lives (t_½) of 0.88-1.03 h. The estimated renal clearance (CL_R) of sulopenem is 8.0-10.6 L/h, with 35.5% ± 6.7% of a 1000 mg dose recovered unchanged in the urine. An ester prodrug, sulopenem etzadroxil, has been developed for oral administration. Initial investigations reported a variable oral bioavailability of 20-34% under fasted conditions, however subsequent work showed that bioavailability is significantly improved by administering sulopenem with food to increase its oral absorption or with probenecid to reduce its renal tubular secretion. Food consumption increases the area under the curve (AUC) of oral sulopenem (500 mg twice daily) by 23.6% when administered alone and 62% when administered with 500 mg of probenecid. Like carbapenems, sulopenem demonstrates bactericidal activity that is associated with the percentage of time that free concentrations exceed the MIC (%f T > MIC). In animal models, bacteriostasis was associated with %f T > MICs ranging from 8.6 to 17%, whereas 2-log₁₀ kill was seen at values ranging from 12 to 28%. No pharmacodynamic targets have been documented for suppression of resistance. Sulopenem concentrations in urine are variable, ranging from 21.8 to 420.0 mg/L (median 84.4 mg/L) in fasted subjects and 28.8 to 609.0 mg/L (median 87.3 mg/L) in those who were fed. Sulopenem has been compared with carbapenems and cephalosporins in guinea pig and murine systemic and lung infection animal models. Studied pathogens included Acinetobacter calcoaceticus, B. fragilis, Citrobacter freundii, Enterobacter cloacae, E. coli, K. pneumoniae, Proteus vulgaris, and Serratia marcescens. These studies reported that overall, sulopenem was non-inferior to carbapenems but appeared to be superior to cephalosporins. A phase III clinical trial (SURE-1) reported that sulopenem was not non-inferior to ciprofloxacin in women infected with fluoroquinolone-susceptible pathogens, due to a higher rate of asymptomatic bacteriuria in sulopenem-treated patients at the test-of-cure visit. However, the researchers reported superiority of sulopenem etzadroxil/probenecid over ciprofloxacin for the treatment of uncomplicated UTIs in women infected with fluoroquinolone/non-susceptible pathogens, and non-inferiority in all patients with a positive urine culture. A phase III clinical trial (SURE-2) compared intravenous sulopenem followed by oral sulopenem etzadroxil/probenecid with ertapenem in the treatment of complicated UTIs. No difference in overall success was noted at the end of therapy. However, intravenous sulopenem followed by oral sulopenem etzadroxil was not non-inferior to ertapenem followed by oral stepdown therapy in overall success at test-of-cure due to a higher rate of asymptomatic bacteriuria in the sulopenem arm. After a meeting with the US FDA, Iterum stated that they are currently evaluating the optimal design for an additional phase III uncomplicated UTI study to be conducted prior to the potential resubmission of the New Drug Application (NDA). It is unclear at this time whether Iterum intends to apply for EMA or Japanese regulatory approval. The safety and tolerability of sulopenem has been reported in various phase I pharmacokinetic studies and phase III clinical trials. Sulopenem (intravenous and oral) appears to be well tolerated in healthy subjects, with and without the coadministration of probenecid, with few serious drug-related treatment-emergent adverse events (TEAEs) reported to date. Reported TEAEs affecting ≥1% of patients were (from most to least common) diarrhea, nausea, headache, vomiting and dizziness. Discontinuation rates were low and were not different than comparator agents. Sulopenem administered orally and/or intravenously represents a potentially well tolerated and effective option for treating uncomplicated and complicated UTIs, especially in patients with documented or highly suspected antimicrobial pathogens to commonly used agents (e.g. fluoroquinolone-resistant E. coli), and in patients with documented microbiological or clinical failure or patients who demonstrate intolerance/adverse effects to first-line agents. This agent will likely be used orally in the outpatient setting, and intravenously followed by oral stepdown in the hospital setting. Sulopenem also allows for oral stepdown therapy in the hospital setting from intravenous non-sulopenem therapy. More clinical data are required to fully assess the clinical efficacy and safety of sulopenem, especially in patients with complicated UTIs caused by resistant pathogens such as ESBL-producing, Amp-C, MDR E. coli. Antimicrobial stewardship programs will need to create guidelines for when this oral and intravenous penem should be used.

Community-Acquired Pneumonia in Canada During COVID-19

Dealing with coronavirus disease 2019 (COVID-19) has been a monumental test of medical skills and resources worldwide. The management of community-acquired pneumonia (CAP) can at times be difficult, but treating CAP in the setting of COVID-19 can be particularly trying and confusing and raises a number of challenging questions relating to etiology, diagnosis, and treatment. This article is based on the authors’ experiences and presents an overview of how CAP during COVID-19 is handled in Canada. We touch on the issues of microbial etiology in patients with CAP in the setting of COVID-19 as well as diagnostic, site of care, and treatment approaches. Published guidelines are the basis of management of CAP and are discussed in the context of Canadian data. We also outline the usual treatment approaches to COVID-19, particularly in patients who have been hospitalized.

Use of Fosfomycin Etest To Determine In Vitro Susceptibility of Clinical Isolates of Enterobacterales Other than Escherichia coli, Nonfermenting Gram-Negative Bacilli, and Gram-Positive Cocci

Clinical isolates of Enterobacterales other than Escherichia coli (EOTEC), nonfermenting Gram-negative bacilli, and Gram-positive cocci were tested for susceptibility to fosfomycin using Etest and reference agar dilution. Applying EUCAST (v. 11.0, 2021) intravenous fosfomycin breakpoints, Etest MICs for EOTEC showed essential agreement (EA), categorical agreement (CA), major error (ME), and very major error (VME) rates of 70.4%, 88.4%, 4.1%, and 32.1%, respectively. No species of EOTEC tested with acceptable rates for all of EA (≥90%), CA (≥90%), ME (≤3%), and VME (≤3%). Etest MICs for Enterococcus faecalis, interpreted using CLSI oral/urine criteria (M100, 2021) showed EA, CA, minor error, ME, and VME rates of 98.5%, 81.2%, 18.8%, 0%, and 0%. Against Staphylococcus aureus, EA, CA, and ME rates were 84.1%, 98.7%, and 1.3% (EUCAST intravenous criteria). S. aureus isolates with fosfomycin MICs of >32 μg/ml (resistant) were not identified by agar dilution. We conclude that performing fosfomycin Etest on isolates of S. aureus will reliably identify fosfomycin-susceptible isolates with low, acceptable rates of MEs and VMEs. Testing of urinary isolates of E. faecalis by Etest is associated with an unacceptably high rate of minor errors (18.8%) but low, acceptable rates of MEs and VMEs when results are interpreted using CLSI criteria. Isolates of EOTEC tested by Etest with resulting MICs interpreted by EUCAST criteria were associated with an unacceptably high VME rate (32.1%). In vitro testing of clinical isolates beyond E. coli, E. faecalis, and S. aureus to determine susceptibility to fosfomycin is problematic with current methods and breakpoints.

Global colistin use: A review of the emergence of resistant Enterobacterales and the impact on their genetic basis

The dramatic global rise of MDR and XDR Enterobacterales in human medicine forced clinicians to the reintroduction of colistin as last-resort drug. Meanwhile, colistin is used in the veterinary medicine since its discovery, leading to a steadily increasing prevalence of resistant isolates in the livestock and meat-based food sector. Consequently, transmission of resistant isolates from animals to humans, acquisition via food and exposure to colistin in the clinic are reasons for the increased prevalence of colistin-resistant Enterobacterales in humans in the last decades. Initially, resistance mechanisms were caused by mutations in chromosomal genes. However, since the discovery in 2015, the focus has shifted exclusively to mobile colistin resistances (mcr). This review will advance the understanding of chromosomal-mediated resistance mechanisms in Enterobacterales. We provide an overview about genes involved in colistin resistance and the current global situation of colistin-resistant Enterobacterales. A comparison of the global colistin use in veterinary and human medicine highlights the effort to reduce colistin sales in veterinary medicine under the One Health approach. In contrast, it uncovers the alarming rise in colistin consumption in human medicine due to the emergence of MDR Enterobacterales, which might be an important driver for the increasing emergence of chromosome-mediated colistin resistance.

Whole genome characterization of Streptococcus pneumoniae from respiratory and blood cultures collected from Canadian hospitals before and after PCV-13 implementation in Canada: Focus on serotypes 22F and 33F from CANWARD 2007-2018

The population of pneumococci circulating in Canada is constantly shifting under the pressures of antimicrobial and conjugate vaccine use. A new 15-valent pneumococcal conjugate vaccine (PCV), containing PCV-13 serotypes plus additional serotypes 22F and 33F, is currently undergoing clinical trials. The purpose of this study was to utilize whole genome sequencing to characterize invasive and respiratory Streptococcus pneumoniae isolates collected from Canadian hospitals pre- (2007-2011) and post-PCV-13 implementation (2012-2018) in Canada, particularly serotypes 22F and 33F. Isolates were obtained from the CANWARD 2007 to 2018 study. Overall, 597 S. pneumoniae isolates were sequenced using the Illumina MiSeq platform: 180 (101 respiratory, 79 blood) isolates of serotype 22F, 74 (41 respiratory, 33 blood) isolates of serotype 33F and 343 isolates randomly selected to broadly encompass pneumococci in Canada. Genomes were clustered using PopPUNK v2.0.2 and assigned to a Global Pneumococcal Sequencing Cluster (GPSC) and MLST sequence type (ST), and visualized using Cytoscape v3.8.0. Acquired resistance genes were identified using ResFinder 2.1, and genes with chromosomal mutations conferring resistance were extracted and compared to standard reference genome R6. PopPUNK clustering suggests that a clone of S. pneumoniae serotype 22F/ST433/GPSC19 demonstrating mefA-mediated macrolide resistance is emerging in Canada post-PCV-13 introduction, collected from both invasive and respiratory sources. Similarly, there is evidence to support a post-PCV-13 shift towards macrolide- and trimethoprim/sulfamethoxazole-resistant serotype 33F/ST100/GPSC3, including a cluster associated with invasive isolates. While some lineages containing vaccine serotypes were predominantly identified pre-PCV-13 implementation (serotype 5/GPSC8, serotype 7F/GPSC15), others (serotype 19A/GPSC1 and 4, serotype 3/GPSC12) continue to maintain a significant presence over time despite inclusion in PCV-13. Further genomic surveillance is necessary to determine additional trends over time in these upcoming vaccine serotypes, as well as the overall pneumococcal population in Canada.

Escalating antimicrobial resistance among Enterobacteriaceae: focus on carbapenemases

Introduction: Over the past few decades, antimicrobial resistance (AMR) has skyrocketed globally among bacteria within the Family Enterobacteriaceae (i.e. Enterobacter spp, Klebsiella spp, Escherichia coli, Proteus spp, Serratia marcescens, Citrobacter spp, and others). Enterobacteriaceae are intestinal flora and are important pathogens in nosocomial and community settings. Enterobacteriaceae spread easily between humans and may acquire AMR via plasmids or other mobile resistance elements. The emergence and spread of multidrug resistant (MDR) clones have greatly limited therapeutic options. Some infections are untreatable with existing antimicrobials.Areas covered: The authors discuss the escalation of CRE globally, the epidemiology and outcomes of CRE infections, the optimal therapy, and the potential role of several new antimicrobials to combat MDR organisms. An exhaustive search for literature related to Enterobacteriaceae was performed using PubMed, using the following key words: antimicrobial resistance; carbapenemases; Enterobacterales; Enterobacteriaceae; Klebsiella pneumoniae; Escherichia coli; global epidemiology; metallo-β-lactamases; multidrug resistance; New Delhi Metalloproteinase-1 (NDM-1); plasmidsExpert opinion: Innovation and development of new classes of antibacterial agents are critical to expand effective therapeutic options. The authors encourage the judicious use of antibiotics and aggressive infection-control measures are essential to minimize the spread of AMR.

Comparison of phenotypic antimicrobial susceptibility testing results and WGS-derived genotypic resistance profiles for a cohort of ESBL-producing Escherichia coli collected from Canadian hospitals: CANWARD 2007-18

OBJECTIVES

To determine whether the genotypic resistance profile inferred from WGS could accurately predict phenotypic resistance for ESBL-producing Escherichia coli isolated from patient samples in Canadian hospital laboratories.

METHODS

As part of the ongoing CANWARD study, 671 E. coli were collected and phenotypically confirmed as ESBL producers using CLSI M100 disc testing criteria. Isolates were sequenced using the Illumina MiSeq platform, resulting in 636 high-quality genomes for comparison. Using a rules-based approach, the genotypic resistance profile was compared with the phenotypic resistance interpretation generated using the CLSI broth microdilution method for ceftriaxone, ciprofloxacin, gentamicin and trimethoprim/sulfamethoxazole.

RESULTS

The most common genes associated with non-susceptibility to ceftriaxone, gentamicin and trimethoprim/sulfamethoxazole were CTX-M-15 (n = 391), aac(3)-IIa + aac(6')-Ib-cr (n = 121) and dfrA17 + sul1 (n = 169), respectively. Ciprofloxacin non-susceptibility was most commonly attributed to alterations in both gyrA (S83L + D87N) and parC (S80I + E84V), with (n = 187) or without (n = 197) aac(6')-Ib-cr. Categorical agreement (susceptible or non-susceptible) between actual and predicted phenotype was 95.6%, 98.9%, 97.6% and 88.8% for ceftriaxone, ciprofloxacin, gentamicin and trimethoprim/sulfamethoxazole, respectively. Only ciprofloxacin results (susceptible or non-susceptible) were predicted with major error (ME) and very major error (VME) rates of <3%: ciprofloxacin (ME, 1.5%; VME, 1.1%); gentamicin (ME, 0.8%-31.7%; VME, 4.8%); ceftriaxone (ME, 81.8%; VME, 3.0%); and trimethoprim/sulfamethoxazole (ME, 0.9%-23.0%; VME, 5.2%-8.5%).

CONCLUSIONS

Our rules-based approach for predicting a resistance phenotype from WGS performed well for ciprofloxacin, with categorical agreement of 98.9%, an ME rate of 1.5% and a VME rate of 1.1%. Although high categorical agreements were also obtained for gentamicin, ceftriaxone and trimethoprim/sulfamethoxazole, ME and/or VME rates were ≥3%.

ESBL-positive Escherichia coli and Klebsiella pneumoniae isolates from across Canada: CANWARD surveillance study, 2007-18

OBJECTIVES

ESBL-producing Escherichia coli and Klebsiella pneumoniae are pathogens of increasing importance in Canada and elsewhere in the world. The purpose of this study was to phenotypically and molecularly characterize ESBL-producing E. coli and K. pneumoniae clinical isolates obtained from patients attending Canadian hospitals over a 12 year period.

METHODS

Isolates were collected between January 2007 and December 2018 as part of an ongoing national surveillance study (CANWARD). ESBL production was confirmed using the CLSI (M100) phenotypic method. Susceptibility testing was carried out using custom broth microdilution panels, and all isolates underwent WGS.

RESULTS

In total, 671 E. coli and 141 K. pneumoniae were confirmed to be ESBL producers. The annual proportion of ESBL-producing isolates increased for both E. coli (from 3.3% in 2007 to 11.2% in 2018; P < 0.0001) and K. pneumoniae (from 1.3% in 2007 to 9.3% in 2018; P < 0.0001). The most frequent STs were ST131 for E. coli [62.4% (419/671) of isolates] and ST11 [7.8% (11/141)] and ST147 [7.8% (11/141)] for K. pneumoniae. Overall, 97.2% of ESBL-producing E. coli and K. pneumoniae isolates were MDR. blaCTX-M-15 predominated in both ESBL-producing E. coli (62.3% of isolates) and ESBL-producing K. pneumoniae (48.9% of isolates).

CONCLUSIONS

The proportion of ESBL-producing E. coli, especially ST131, and K. pneumoniae, especially ST11 and ST147, in Canada increased significantly from 2007 to 2018. Continued prospective surveillance of these evolving MDR and at times XDR pathogens is imperative.

In vitro activity and resistance rates of topical antimicrobials fusidic acid, mupirocin and ozenoxacin against skin and soft tissue infection pathogens obtained across Canada (CANWARD 2007-18)

BACKGROUND

Current antimicrobial susceptibility/resistance data versus skin and soft tissue infection (SSTI) pathogens help to guide empirical treatment using topical antimicrobials.

OBJECTIVES

To assess the in vitro activity and resistance rates of fusidic acid, mupirocin, ozenoxacin and comparator agents against pathogens isolated from patients with SSTIs in Canada.

METHODS

SSTI isolates of MSSA (n = 422), MRSA (n = 283) and Streptococcus pyogenes (n = 46) obtained from CANWARD 2007-18 were tested using CLSI broth microdilution. Fusidic acid low-level resistance was defined as an MIC of ≥2 mg/L and high-level resistance as an MIC ≥512 mg/L. Mupirocin high-level resistance was defined as an MIC ≥512 mg/L and low-level resistance was an MIC of 2-256 mg/L.

RESULTS

Low-level and high-level fusidic acid resistance in MSSA was 10.9% and 1.7%, respectively. Low-level and high-level fusidic acid resistance in MRSA was 10.6% and 3.5%, respectively. High-level mupirocin resistance was identified in 1.4% of MSSA and 14.1% of MRSA, respectively. Versus MSSA, ozenoxacin demonstrated MIC50 and MIC90 of 0.004 and 0.25 mg/L, respectively. Against MRSA, ozenoxacin inhibited all isolates at an MIC of ≤0.5 mg/L, including isolates with ciprofloxacin MICs >2 mg/L, clarithromycin-resistant, clindamycin-resistant, high-level fusidic acid-resistant and high-level mupirocin-resistant isolates.

CONCLUSIONS

We conclude that fusidic acid low-level resistance exceeded 10% for both MSSA and MRSA while fusidic acid high-level resistance was ≤3.5%. Mupirocin high-level resistance exceeded 10% in MRSA. Ozenoxacin is active versus SSTI pathogens including MRSA resistant to fluoroquinolones, macrolides, clindamycin, fusidic acid and mupirocin.

In vitro susceptibility of common bacterial pathogens causing respiratory tract infections in Canada to lefamulin, a new pleuromutilin

BACKGROUND

Community-acquired pneumonia (CAP) is a significant global health concern. Pathogens causing CAP demonstrate increasing resistance to commonly prescribed empiric treatments. Resistance in Streptococcus pneumoniae, the most prevalent bacterial cause of CAP, has been increasing worldwide, highlighting the need for improved antibacterial agents. Lefamulin, a novel pleuromutilin, is a recently approved therapeutic agent highly active against many lower respiratory tract pathogens. However, to date minimal data are available to describe the in vitro activity of lefamulin against bacterial isolates associated with CAP.

METHODS

Common bacterial causes of CAP obtained from both lower respiratory and blood specimen isolates cultured by hospital laboratories across Canada were submitted to the annual CANWARD study's coordinating laboratory in Winnipeg, Canada, from January 2015 to October 2018. A total of 876 bacterial isolates were tested against lefamulin and comparator agents using the Clinical and Laboratory Standards Institute (CLSI) reference broth microdilution method, and minimum inhibitory concentrations (MICs) were interpreted using accepted breakpoints.

RESULTS

All S. pneumoniae isolates tested from both respiratory (n = 315) and blood specimens (n = 167) were susceptible to lefamulin (MIC ≤0.5 μg/mL), including isolates resistant to penicillins, clarithromycin, doxycycline, and trimethoprim-sulfamethoxazole. Lefamulin also inhibited 99.0% of Haemophilus influenzae isolates (regardless of β-lactamase production) (99 specimens; MIC ≤2 μg/mL) and 95.7% of methicillin-susceptible Staphylococcus aureus (MSSA) (MIC ≤0.25 μg/mL; 70 specimens) at their susceptible breakpoints. Conclusions: Lefamulin demonstrated potent in vitro activity against all respiratory isolates tested and may represent a significant advancement in empiric treatment options for CAP.

Real-life experience with ceftolozane/tazobactam in Canada: results from the CLEAR (Canadian LEadership on Antimicrobial Real-life usage) registry

OBJECTIVES

Ceftolozane/tazobactam is a cephalosporin/β-lactamase inhibitor combination with activity against Gram-negative bacilli. Here we report the use of ceftolozane/tazobactam in Canada using a national registry.

METHODS

The CLEAR registry uses a REDCap^TM online survey to capture details associated with clinical use of ceftolozane/tazobactam.

RESULTS

Data from 51 patients treated in 2020 with ceftolozane/tazobactam are available. Infections treated included hospital-acquired bacterial pneumonia (37.3% of patients), ventilator-associated bacterial pneumonia (15.7%), bone and joint infection (11.8%), complicated intra-abdominal infection (7.8%) and complicated skin and skin-structure infection (7.8%). Moreover, 17.6% of patients had bacteraemia and 47.1% were in intensive care. Ceftolozane/tazobactam was primarily used as directed therapy for Pseudomonas aeruginosa infections (92.2% of patients). Ceftolozane/tazobactam was used because of resistance to (86.3%), failure of (11.8%) or adverse effects from (2.0%) previously prescribed antimicrobials. Ceftolozane/tazobactam susceptibility testing was performed on isolates from 88.2% of patients. Ceftolozane/tazobactam was used in combination with another antimicrobial active against Gram-negative bacilli in 39.2% of patients [aminoglycosides (15.7%), fluoroquinolones (9.8%) and colistin/polymyxin B (7.8%)]. The dosage regimen was customised in all patients based on creatinine clearance. The treatment duration was primarily >10 days (60.8% of patients), with microbiological success in 60.5% and clinical success in 64.4% of patients. Moreover, 7.8% of patients had adverse effects not requiring drug discontinuation.

CONCLUSION

In Canada, ceftolozane/tazobactam is used as directed therapy to treat a variety of severe infections caused by multidrug-resistant P. aeruginosa. It is commonly used in combination with other antimicrobials with relatively high microbiological/clinical cure rates and an excellent safety profile.

An Update on Eight "New" Antibiotics against Multidrug-Resistant Gram-Negative Bacteria

Infections in the ICU are often caused by Gram-negative bacteria. When these microorganisms are resistant to third-generation cephalosporines (due to extended-spectrum (ESBL) or AmpC beta-lactamases) or to carbapenems (for example carbapenem producing Enterobacteriales (CPE)), the treatment options become limited. In the last six years, fortunately, there have been new antibiotics approved by the U.S. Food and Drug Administration (FDA) with predominant activities against Gram-negative bacteria. We aimed to review these antibiotics: plazomicin, eravacycline, temocillin, cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, meropenem/vaborbactam, and imipenem/relebactam. Temocillin is an antibiotic that was only approved in Belgium and the UK several decades ago. We reviewed the in vitro activities of these new antibiotics, especially against ESBL and CPE microorganisms, potential side effects, and clinical studies in complicated urinary tract infections (cUTI), intra-abdominal infections (cIAI), and hospital-acquired pneumonia/ventilator-associatedpneumonia (HAP/VAP). All of these new antibiotics are active against ESBL, and almost all of them are active against CPE caused by KPC beta-lactamase, but only some of them are active against CPE due to MBL or OXA beta-lactamases. At present, all of these new antibiotics are approved by the U.S. Food and Drug Administration for cUTI (except eravacycline) and most of them for cIAI (eravacycline, ceftazidime/avibactam, ceftolozane/tazobactam, and imipenem/relebactam) and for HAP or VAP (cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, and imipenem/relebactam).

Real-life experience with ceftobiprole in Canada: Results from the CLEAR (CanadianLEadership onAntimicrobialReal-life usage) registry

OBJECTIVES

Ceftobiprole is an advanced-generation cephalosporin with a favourable safety profile. Published data on the clinical use of ceftobiprole are limited. We report use of ceftobiprole in Canadian patients using data captured by the CLEAR registry.

METHODS

The CLEAR registry uses the web-based research data management program REDCap™ (online survey) to facilitate clinicians entering details associated with their clinical experiences using ceftobiprole.

RESULTS

Data were available for 38 patients treated with ceftobiprole. The most common infections treated were endocarditis (42.1% of patients), bone and joint infection (23.7%) and hospital-associated bacterial pneumonia (15.8%). 92.1% of patients had bacteraemia and 21.1% were in intensive care. Ceftobiprole was used because of failure of (71.1%), resistance to (18.4%) or adverse effects from (10.5%) previously prescribed antimicrobial agents. Ceftobiprole was primarily used as directed therapy for methicillin-resistant Staphylococcus aureus (MRSA) infections (94.7% of patients). Ceftobiprole susceptibility testing was performed on isolates from 47.4% of patients. It was used concomitantly with daptomycin in 55.3% of patients and with vancomycin in 18.4% of patients. Treatment duration was primarily >10 days (65.8% of patients) with microbiological success in 97.0% and clinical success in 84.8% of patients. 2.6% of patients had gastrointestinal adverse effects.

CONCLUSION

In Canada to date, ceftobiprole is used as directed therapy to treat a variety of severe infections caused by MRSA. It is primarily used in patients failing previous antimicrobials, is frequently added to, and thus used in combination with daptomycin or vancomycin with high microbiological and clinical cure rates and an excellent safety profile.

Susceptibility of Clinical Isolates of Escherichia coli to Fosfomycin as Measured by Four In Vitro Testing Methods

Clinical isolates of Escherichia coli (n = 554) were tested against fosfomycin using agar dilution, disk diffusion, and Etest. Agar dilution (reference method) identified few isolates with fosfomycin MICs of 64 (n = 3), 128 (n = 4), and ≥256 μg/ml (n = 2). Applying CLSI (M100, 2020) and EUCAST (v. 10.0, 2020) breakpoints, 98.9% and 98.4% (agar dilution), 99.3% and 99.1% (disk diffusion), and 99.1% and 98.9% (Etest) of isolates were fosfomycin susceptible, respectively. Essential agreement (agar dilution versus Etest) was low (40.8%); 59.3% (131/221) of isolates with agar dilution MICs of 2 to 128 μg/ml tested 2 to 4 doubling dilutions lower by Etest. Applying CLSI breakpoints, categorical agreement was >99% for both disk diffusion and Etest; no major errors (MEs) or very major errors (VMEs) were identified, and rates of minor errors (mEs) were <1%. EUCAST breakpoints yielded categorical agreements of >99% and no MEs for both disk diffusion and Etest; however, VMEs occurred at unacceptable rates of 44.4% (disk diffusion) and 33.3% (Etest). All isolates with agar dilution MICs of ≥32 μg/ml (n = 12) and a subset of isolates with MICs of ≤16 μg/ml (n = 49) were also tested using the Vitek 2 AST-N391 card and generated fosfomycin MICs 1 to ≥3 doubling dilutions lower than agar dilution for 11/12 isolates with agar dilution MICs of ≥32 μg/ml. We conclude that performing fosfomycin disk diffusion or Etest on urinary isolates of E. coli and interpreting results using CLSI breakpoints reliably identified fosfomycin-susceptible isolates regardless of differences in endpoint reading criteria. EUCAST breakpoints generated excessive rates of VMEs for our isolate collection of high fosfomycin susceptibility.

In Vitro Activity of Cefiderocol, a Novel Siderophore Cephalosporin, against Gram-Negative Bacilli Isolated from Patients in Canadian Intensive Care Units

The in vitro activity of cefiderocol was evaluated against Gram-negative bacilli isolated from patients in Canadian intensive care units from 2015 to 2017 using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method and interpretive criteria. All 800 isolates of Gram-negative bacilli tested were susceptible to cefiderocol (MIC ≤4 μg/ml), including isolates of ESBL-producing (n=40), AmpC-producing (n=6), and carbapenem-nonsusceptible (n=21) Enterobacterales, carbapenem-nonsusceptible (n=54) and multidrug-resistant (n=29) Pseudomonas aeruginosa, Stenotrophomonas maltophilia (n=66), and Acinetobacter baumannii (n=11).

An overview of ceftolozane sulfate + tazobactam for treating hospital acquired pneumonia

INTRODUCTION

Ceftolozane-tazobactam is a combination of a new cephalosporin, with activity similar to that of ceftazidime, and a known inhibitor of beta-lactamases. This compound shows excellent activity against most gram-negative organisms causative of hospital-acquired pneumonia (HAP) or ventilator-acquired pneumonia (VAP), including extended spectrum beta-lactamase (ESBL)-producing Enterobacterales and multidrug-resistant (MDR) Pseudomonas aeruginosa.

AREAS COVERED

This article reviews the spectrum of activity, the main pharmacokinetic and pharmacodynamic characteristics and the clinical efficacy and safety of ceftolozane-tazobactam in the treatment of HAP/VAP in adult patients.

EXPERT OPINION

The results of a randomized clinical trial have demonstrated an efficacy and safety profile of ceftolozane-tazobactam similar to that of its comparator for the treatment of patients with HAP/VAP. Several retrospective studies have shown good efficacy of the drug for the treatment of respiratory infections caused by MDR P. aeruginosa. The use of this drug may be incorporated as a new therapeutic option for the treatment of patients with HAP/VAP in a carbapenem-saving setting or as a therapeutic alternative with a better safety profile than other therapeutic options in patients with infections caused by MDR P. aeruginosa.

Rapid differentiation between bacterial infections and cancer using a near-infrared fluorogenic probe

The reliable differentiation between bacterial infections and other pathologies is crucial for both diagnostics and therapeutic approaches. To accommodate such needs, we herein report the development of an activatable near-infrared fluorescent probe 1 that could be applied in the ultrafast, ultrasensitive and specific detection of nitroreductase (NTR) activity in bacterial pathogens both in vitro and in vivo. Upon reaction with NTR, the nitro-group of the para-nitro phenyl sulfonic moiety present in probe 1 was reduced to an amino-group, resulting in a near-infrared fluorescence turn-on of the latent cyanine 7 fluorophore. Probe 1 was capable of rapid and real-time quantitative detection of 0–150 ng mL⁻¹ NTR with a limit of detection as low as 0.67 ng mL⁻¹in vitro. In addition, probe 1 exhibited an outstanding performance of ultrafast measurements and suitable selectivity toward NTR to accurately sense intracellular basal NTR in ESKAPE bacterial pathogens. Most remarkably, probe 1 was capable of noninvasively identifying bacterial infection sites without showing any significantly increased signal of tumour sites in the same animal within 30 min.

A new nitroreductase-responsive near-infrared fluorogenic probe can specifically image live bacteria in mouse models and does not accumulate at sites of inflammation or tumor.