Use of isavuconazole antifungal medicine to treat mold infections in Asia and the Western Pacific region: a plain language summary

WHAT IS THIS SUMMARY ABOUT?

Molds are types of fungus that can invade humans. It can cause a disease called invasive mold infection (IMI) and make people sick or cause death. This is a summary of a study that looked at mold samples collected from people in Asia and the Western Pacific region to check if an antifungal medicine called isavuconazole (ISC) can stop the growth of or kill these molds.

WHAT WERE THE RESULTS?

One type of mold known as Aspergillus or type 1 molds, was more common than other molds. Antifungal medicines including ISC, posaconazole, voriconazole, and itraconazole slowed or stopped the growth of the type 1 molds. ISC was very active in slowing or stopping the growth of this mold. Other molds, known as non-Aspergillus or type 2 mold, were less common. The antifungals medicines mentioned above were able to slow or stop the growth of some but not all of the type 2 molds.

WHAT DO THE RESULTS OF THE STUDY MEAN?

ISC stopped the growth of most type 1 molds and was as good as the other antifungal medicines against type 2 molds.

WHAT IS THE PURPOSE OF THIS PLAIN LANGUAGE SUMMARY?

The purpose of this plain language summary is to help you to understand the findings from recent research. The results of this study may differ from those of other studies. Health professionals should make treatment decisions based on all available evidence not on the results of a single study.

Plain language summary: Did the COVID-19 pandemic change the resistance to current antifungal medicines?

WHAT IS THIS SUMMARY ABOUT?

Previous research shows that patients with COVID-19 have a high chance of getting fungal infections. Medicines called antifungals are used to treat fungal infections. However, some fungi are resistant, which means the fungi are not killed by the antifungals and they keep growing, which can make the patients sicker and even die. This is a summary of a study that looked at whether different types of fungi and their resistance to antifungals changed from before COVID-19 to during the pandemic.

WHAT WERE THE RESULTS?

We found that some fungi were more common before while others were more common during the pandemic. We also observed that resistance to antifungals did not change much either between fungi collected before and during the COVID-19 pandemic.

WHAT DO THE RESULTS OF THE STUDY MEAN?

Knowing which fungal species are resistant to each antifungal can help doctors choose the best treatment. The results from this study may help scientists understand the effect of the COVID-19 pandemic on antifungal resistance.

In Vitro Activity of Isavuconazole and Other Mould-Active Azoles against Aspergillus fumigatus with and without CYP51 Alterations

Azole resistance in Aspergillus fumigatus (AFM) is mainly associated with mutations in CYP51A and its promoter region or its homologue CYP51B. We evaluated the in vitro activity of isavuconazole, itraconazole, posaconazole, and voriconazole against 660 AFM collected during 2017-2020. Isolates were tested via CLSI broth microdilution. CLSI epidemiological cutoff values were applied. Non-wildtype (NWT) isolates to azoles were screened for alterations in the CYP51 sequences using whole genome sequencing. Azoles had similar activities against 660 AFM isolates. Overall, AFM displayed WT MIC values to isavuconazole (92.7%), itraconazole (92.9%), posaconazole (97.3%), and voriconazole (96.7%). Only 66 isolates (10.0%) were NWT to 1 or more of the azoles, and 32 harbored one or more alterations in the CYP51 sequences. Of these, 29/32 (90.1%) were NWT to itraconazole, 25/32 (78.1%) were NWT to isavuconazole, 17/32 (53.1%) were NWT to voriconazole, and 11/32 (34.4%) were NWT to posaconazole. The most frequent alteration was CYP51A TR34/L98H, carried by 14 isolates. Four isolates carried the alteration I242V in CYP51A, and G448S; A9T, or G138C was carried by one isolate each. Multiple alterations in CYP51A were detected in five isolates. Alterations in CYP51B were noted in seven isolates. Among 34 NWT isolates without -CYP51 alterations, WT rates to isavuconazole, itraconazole, voriconazole, and posaconazole were 32.4%, 47.1%, 85.3%, and 82.4%, respectively. Ten different CYP51 alterations were detected in 32/66 NWT isolates. Alterations in AFM CYP51 sequences can have variable effects on the in vitro activity of the azoles that are best delineated by testing all triazoles.

Evaluation of the Post-Antifungal Effect of Rezafungin and Micafungin against Candida albicans, Candida parapsilosis, and Candida glabrata

BACKGROUND

Rezafungin, a new echinocandin with an extended half-life, exhibits potent activity against Candida spp. Aside from the MIC, specific interactions between antifungal and isolate, including the duration of anti-infective activity, may impact dose interval choices and infection outcome.

OBJECTIVES

We evaluated rezafungin and micafungin post-antifungal effect (PAFE) against C. albicans, C. parapsilosis, and C. glabrata.

METHODS

Six Candida spp. isolates were tested, including 2 of each species, C. albicans, C. parapsilosis, and C. glabrata. Antifungal susceptibility testing was performed using the CLSI reference broth microdilution method. Antifungal concentrations of 1X, 4X, and 16X the baseline MIC were used for PAFE determinations. Colony counts were performed at T0 (pre-exposure), after the 1-h drug exposure, after the cell wash (T1), and at T2, T4, T8, T12, T24, and T48 hours.

RESULTS

Rezafungin PAFE results were equivalent to micafungin PAFE values for one C. albicans (>14.9 h and both C. glabrata (>40 h) isolates for all concentrations tested. The rezafungin and micafungin PAFEs could not be determined against one C. albicans isolate. Prolonged PAFE results were also noted for rezafungin (range, 18.4 h to >40 h) against both C. parapsilosis isolates at all concentrations, while no micafungin PAFE or a short PAFE (range, 1.8 h to 7.4 h) was observed against these organisms, except at 16X bMIC.

CONCLUSIONS

Rezafungin showed sustained growth inhibition following drug removal and displayed equivalent or longer PAFE values than micafungin against all tested Candida spp.

OUP accepted manuscript

Studies demonstrated the impact of the COVID-19 pandemic in the prevalence and susceptibility profiles of bacterial and fungal organisms. We analyzed 4821 invasive fungal isolates collected during 2018, 2019, and 2020 in 48 hospitals worldwide to evaluate the impact of this event in the occurrence and susceptibility rates of common fungal species. Isolates were tested using the CLSI broth microdilution method. While the percentage of total isolates that were C. glabrata (n = 710 isolates) or C. krusei (n = 112) slightly increased in 2020, the percentage for C. parapsilosis (n = 542), A. fumigatus (n = 416), and C. lusitaniae (n = 84) significantly decreased (P < .05). Fluconazole resistance in C. glabrata decreased from 5.8% in 2018–2019 to 2.0% in 2020, mainly due to fewer hospitals in the US having these isolates (5 vs. 1 hospital). Conversely, higher fluconazole-resistance rates were noted for C. parapsilosis (13.9 vs. 9.8%) and C. tropicalis (3.5 vs. 0.7%; P < .05) during 2020. Voriconazole resistance also increased for these species. Echinocandin resistance was unchanged among Candida spp. Voriconazole susceptibility rates in A. fumigatus were similar in these two periods (91.7% in 2018 and 2019 vs. 93.0% in 2020). Changes were also noticed in the organisms with smaller numbers of collected isolates. We observed variations in the occurrence of organisms submitted to a global surveillance and the susceptibility patterns for some organism-antifungal combinations. As the COVID-19 pandemic is still ongoing, the impact of this event must continue to be monitored to guide treatment of patients affected by bacterial and fungal infections.

1054. Activity of a Anti-staphylococcal Lysin, LSVT-1701: In vitro Susceptibility of Staphylococcus aureus and Coagulase-Negative Staphylococci (CoNS) Global Clinical Isolates (2002 to 2019)

Background

LSVT-1701, formerly SAL200, is a novel, recombinantly-produced, bacteriophage-encoded lysin that specifically targets staphylococci via cell wall enzymatic hydrolysis. We reported the in vitro activity of LSVT-1701 against clinical isolates of S. aureus and coagulase-negative staphylococci (CoNS) collected worldwide.

Methods

LSVT-1701 and comparators were tested against 415 S. aureus (n=315) and CoNS (n=100) clinical isolates expressing various resistance phenotypes. The isolates were collected in 2002-2019 from medical centers located in the United States (50 medical centers; 174 isolates; 41.9% overall), Europe (37 medical centers; 140 isolates; 33.7% overall), Asia-Pacific region (15 medical centers; 55 isolates; 13.3% overall), and Latin America (12 medical centers; 46 isolates; 11.1% overall). These isolates originated mostly from the year 2019 (n=323).The isolates were susceptibility tested by the CLSI broth microdilution method. MIC interpretations were based on CLSI and EUCAST criteria where available.

Results

LSVT-1701 was highly active against S. aureus and CoNS isolates with MIC90 values of 2 mg/L for all S. aureus, methicillin-susceptible S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), and CoNS (Table). The highest LSVT-1701 MIC values were 4 and 8 mg/L among S. aureus and CoNS, respectively. LSVT-1701 retained potent activity against S. aureus isolates showing resistance or decreased susceptibility to oxacillin, vancomycin, teicoplanin, telavancin, linezolid, daptomycin, ceftaroline, or lefamulin; MIC50 values ranged from 0.5 to 1 mg/L and MIC90 values ranged from 1 to 4 mg/L among S. aureus resistant subsets.

Conclusion

LSVT-1701 demonstrated potent in vitro activity against contemporary clinical isolates of S. aureus and CoNS collected from medical centers worldwide and against resistant S. aureus isolates with uncommon resistance phenotypes. The results of this study support further clinical development of LSVT-1701 to treat staphylococcal infections.

Disclosures

David Huang, MD, PhD, Lysovant (Consultant) Helio S. Sader, MD, PhD, FIDSA, AbbVie (formerly Allergan) (Research Grant or Support)Basilea Pharmaceutica International, Ltd. (Research Grant or Support)Cipla Therapeutics (Research Grant or Support)Cipla USA Inc. (Research Grant or Support)Department of Health and Human Services (Research Grant or Support, Contract no. HHSO100201600002C)Melinta Therapeutics, LLC (Research Grant or Support)Nabriva Therapeutics (Research Grant or Support)Pfizer, Inc. (Research Grant or Support)Shionogi (Research Grant or Support)Spero Therapeutics (Research Grant or Support) Paul R Rhomberg, Cidara Therapeutics, Inc. (Research Grant or Support)Pfizer, Inc. (Research Grant or Support) Katyna Borroto-Esoda, PhD, Lysovant (Consultant) Eric Gaukel, BS, Lysovant (Employee)

1076. Activity of Rezafungin and Comparator Antifungal Agents Tested Against a Worldwide Collection of Contemporaneous Invasive Fungal Isolates (2019-2020)

Background

Rezafungin (RZF) is a new echinocandin (ECH) with a long half-life and front-loaded drug exposure that allow for once-weekly intravenous administration. RZF is under Phase 3 development for the treatment of candidemia and invasive candidiasis and the prevention of invasive fungal disease caused by Candida, Aspergillus, and Pneumocystis spp. in blood and marrow transplant recipients. We evaluated the activity of RZF and comparators against invasive fungal isolates from the SENTRY Antimicrobial Surveillance Program.

Methods

A total of 1,427 Candida spp., 38 Cryptococcus neoformans (CNEO), 186 Aspergillus fumigatus (AFM), and 28 Aspergillus section Flavi (AFL) collected from 24 countries in 2019-2020 were tested. CLSI antifungal broth microdilution assays were performed according to standard method (M27, M38) with the exception that panels were made by dispensing 10 µL of a 20x drug stock solution into panels that contained 90 µL of RPMI and mixing. CLSI criteria were applied (M59, M60, M61).

Results

RZF demonstrated potent activity against C. albicans (CA; MIC50/90, 0.03/0.06 mg/L), C. tropicalis (CT; MIC50/90, 0.03/0.06 mg/L), C. glabrata (CG; MIC50/90, 0.06/0.06 mg/L), C. krusei (CK; MIC50/90, 0.03/0.03 mg/L), and C. dubliniensis (MIC50/90, 0.06/0.12 mg/L). RZF inhibited 99.6% of C. parapsilosis (CP; MIC50/90,1/2 mg/L) at ≤2 mg/L. RZF activity was similar to the other ECH against these 6 Candida spp. All CA, CT, and CK isolates as well as the majority of CG (96.2-97.9%) and CP (86.2-100%) isolates were susceptible (S) to comparator ECHs. Fluconazole resistance was detected among 0.5%, 4.5%, 10.5%, and 1.2% of CA, CG, CP, and CT, respectively. The azoles were active against CNEO, but all ECHs displayed limited activity against CNEO. ECHs were active against AFM (MEC90 range, 0.015-0.06 mg/L) and AFL (MEC90 range, 0.015-0.03 mg/L). RZF activity was similar to that of the other ECHs. All but 16 (8.6%) AFM isolates were S to voriconazole, and 100% of AFL were wild-type to mould-active azoles.

Conclusion

RZF and other ECHs displayed similar activity against Candida and Aspergillus spp. isolates from invasive fungal infections. These in vitro results support the development of RZF for the treatment and prevention of invasive fungal disease.

Disclosures

Cecilia G. Carvalhaes, MD, PhD, AbbVie (formerly Allergan) (Research Grant or Support)Cidara Therapeutics, Inc. (Research Grant or Support)Cipla Therapeutics (Research Grant or Support)Cipla USA Inc. (Research Grant or Support)Melinta Therapeutics, LLC (Research Grant or Support)Pfizer, Inc. (Research Grant or Support) Abby L. Klauer, n/a, Cidara Therapeutics, Inc. (Research Grant or Support)Spero Therapeutics (Research Grant or Support) Paul R Rhomberg, Cidara Therapeutics, Inc. (Research Grant or Support)Pfizer, Inc. (Research Grant or Support) Michael A Pfaller, MD, Basilea Pharmaceutica International, Ltd. (Research Grant or Support)Cidara Therapeutics, Inc. (Research Grant or Support)Department of Health and Human Services (Research Grant or Support, Contract no. HHSO100201600002C)Pfizer, Inc. (Research Grant or Support) Mariana Castanheira, PhD, AbbVie (formerly Allergan) (Research Grant or Support)Bravos Biosciences (Research Grant or Support)Cidara Therapeutics, Inc. (Research Grant or Support)Cipla Therapeutics (Research Grant or Support)Cipla USA Inc. (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, LLC (Research Grant or Support)Pfizer, Inc. (Research Grant or Support)Qpex Biopharma (Research Grant or Support)Shionogi (Research Grant or Support)Spero Therapeutics (Research Grant or Support) Mariana Castanheira, PhD, Affinity Biosensors (Individual(s) Involved: Self): Research Grant or Support; Allergan (Individual(s) Involved: Self): Research Grant or Support; Amicrobe, Inc (Individual(s) Involved: Self): Research Grant or Support; Amplyx Pharma (Individual(s) Involved: Self): Research Grant or Support; Artugen Therapeutics USA, Inc. (Individual(s) Involved: Self): Research Grant or Support; Astellas (Individual(s) Involved: Self): Research Grant or Support; Basilea (Individual(s) Involved: Self): Research Grant or Support; Beth Israel Deaconess Medical Center (Individual(s) Involved: Self): Research Grant or Support; BIDMC (Individual(s) Involved: Self): Research Grant or Support; bioMerieux Inc. (Individual(s) Involved: Self): Research Grant or Support; BioVersys Ag (Individual(s) Involved: Self): Research Grant or Support; Bugworks (Individual(s) Involved: Self): Research Grant or Support; Cidara (Individual(s) Involved: Self): Research Grant or Support; Cipla (Individual(s) Involved: Self): Research Grant or Support; Contrafect (Individual(s) Involved: Self): Research Grant or Support; Cormedix (Individual(s) Involved: Self): Research Grant or Support; Crestone, Inc. (Individual(s) Involved: Self): Research Grant or Support; Curza (Individual(s) Involved: Self): Research Grant or Support; CXC7 (Individual(s) Involved: Self): Research Grant or Support; Entasis (Individual(s) Involved: Self): Research Grant or Support; Fedora Pharmaceutical (Individual(s) Involved: Self): Research Grant or Support; Fimbrion Therapeutics (Individual(s) Involved: Self): Research Grant or Support; Fox Chase (Individual(s) Involved: Self): Research Grant or Support; GlaxoSmithKline (Individual(s) Involved: Self): Research Grant or Support; Guardian Therapeutics (Individual(s) Involved: Self): Research Grant or Support; Hardy Diagnostics (Individual(s) Involved: Self): Research Grant or Support; IHMA (Individual(s) Involved: Self): Research Grant or Support; Janssen Research & Development (Individual(s) Involved: Self): Research Grant or Support; Johnson & Johnson (Individual(s) Involved: Self): Research Grant or Support; Kaleido Biosceinces (Individual(s) Involved: Self): Research Grant or Support; KBP Biosciences (Individual(s) Involved: Self): Research Grant or Support; Luminex (Individual(s) Involved: Self): Research Grant or Support; Matrivax (Individual(s) Involved: Self): Research Grant or Support; Mayo Clinic (Individual(s) Involved: Self): Research Grant or Support; Medpace (Individual(s) Involved: Self): Research Grant or Support; Meiji Seika Pharma Co., Ltd. (Individual(s) Involved: Self): Research Grant or Support; Melinta (Individual(s) Involved: Self): Research Grant or Support; Menarini (Individual(s) Involved: Self): Research Grant or Support; Merck (Individual(s) Involved: Self): Research Grant or Support; Meridian Bioscience Inc. (Individual(s) Involved: Self): Research Grant or Support; Micromyx (Individual(s) Involved: Self): Research Grant or Support; MicuRx (Individual(s) Involved: Self): Research Grant or Support; N8 Medical (Individual(s) Involved: Self): Research Grant or Support; Nabriva (Individual(s) Involved: Self): Research Grant or Support; National Institutes of Health (Individual(s) Involved: Self): Research Grant or Support; National University of Singapore (Individual(s) Involved: Self): Research Grant or Support; North Bristol NHS Trust (Individual(s) Involved: Self): Research Grant or Support; Novome Biotechnologies (Individual(s) Involved: Self): Research Grant or Support; Paratek (Individual(s) Involved: Self): Research Grant or Support; Pfizer (Individual(s) Involved: Self): Research Grant or Support; Prokaryotics Inc. (Individual(s) Involved: Self): Research Grant or Support; QPEX Biopharma (Individual(s) Involved: Self): Research Grant or Support; Rhode Island Hospital (Individual(s) Involved: Self): Research Grant or Support; RIHML (Individual(s) Involved: Self): Research Grant or Support; Roche (Individual(s) Involved: Self): Research Grant or Support; Roivant (Individual(s) Involved: Self): Research Grant or Support; Salvat (Individual(s) Involved: Self): Research Grant or Support; Scynexis (Individual(s) Involved: Self): Research Grant or Support; SeLux Diagnostics (Individual(s) Involved: Self): Research Grant or Support; Shionogi (Individual(s) Involved: Self): Research Grant or Support; Specific Diagnostics (Individual(s) Involved: Self): Research Grant or Support; Spero (Individual(s) Involved: Self): Research Grant or Support; SuperTrans Medical LT (Individual(s) Involved: Self): Research Grant or Support; T2 Biosystems (Individual(s) Involved: Self): Research Grant or Support; The University of Queensland (Individual(s) Involved: Self): Research Grant or Support; Thermo Fisher Scientific (Individual(s) Involved: Self): Research Grant or Support; Tufts Medical Center (Individual(s) Involved: Self): Research Grant or Support; Universite de Sherbrooke (Individual(s) Involved: Self): Research Grant or Support; University of Iowa (Individual(s) Involved: Self): Research Grant or Support; University of Iowa Hospitals and Clinics (Individual(s) Involved: Self): Research Grant or Support; University of Wisconsin (Individual(s) Involved: Self): Research Grant or Support; UNT System College of Pharmacy (Individual(s) Involved: Self): Research Grant or Support; URMC (Individual(s) Involved: Self): Research Grant or Support; UT Southwestern (Individual(s) Involved: Self): Research Grant or Support; VenatoRx (Individual(s) Involved: Self): Research Grant or Support; Viosera Therapeutics (Individual(s) Involved: Self): Research Grant or Support; Wayne State University (Individual(s) Involved: Self): Research Grant or Support

In vitro activity of the orally bioavailable ceftibuten/VNRX-7145 (VNRX-5236 etzadroxil) combination against a challenge set of Enterobacterales pathogens carrying molecularly characterized β-lactamase genes

Objectives

This study assessed the activity of ceftibuten, ceftibuten combined with the active form (VNRX-5236) of the β-lactamase inhibitor VNRX-7145 and comparators against a challenge set of Gram-negative pathogens.

Methods

Two hundred and five Enterobacterales carrying plasmid AmpC (53 isolates), ESBL (50), KPC (50), OXA-48-like (49) or OXA-48-like with KPC (3) encoding genes were selected. Susceptibility was determined by broth microdilution. VNRX-5236 and avibactam were tested at a fixed concentration of 4 mg/L.

Results

Ceftibuten/VNRX-5236 (MIC_50/90 0.12/1 mg/L) MIC values were 256-fold lower than those of ceftibuten (MIC_50/90 32/256 mg/L) for all Enterobacterales and 2- to 4-fold lower than those of ceftazidime/avibactam (MIC_50/90 0.5/2 mg/L). For isolates producing a plasmid-encoded AmpC, VNRX-5236 decreased ceftibuten MIC (MIC_50/90 0.12/1 mg/L) by at least 512-fold compared with ceftibuten (MIC_50/90 128/>256 mg/L). Ceftibuten/VNRX-5236 (MIC_50/90 0.06/0.12 mg/L) and meropenem (MIC_50/90 ≤0.03/0.06 mg/L; 100% susceptible) showed comparable activities against ESBL isolates and these agents had MIC₉₀ values 4- to 8-fold lower than that of ceftazidime/avibactam (MIC_50/90 0.25/0.5 mg/L; 100% susceptible). Ceftibuten/VNRX-5236 (MIC_50/90 0.12/0.5 mg/L) had the lowest MIC for KPC producers, followed by ceftazidime/avibactam (MIC_50/90 2/4 mg/L; 98.0% susceptible). The same MIC₉₀ values were obtained for ceftibuten/VNRX-5236 (MIC_50/90 0.25/1 mg/L) and ceftazidime/avibactam (MIC_50/90 1/1 mg/L; 100.0% susceptible) for isolates carrying bla_OXA-48-like. VNRX-5236 decreased the ceftibuten MIC at least 16-fold for three isolates carrying bla_OXA-48-like and bla_KPC.

Conclusions

VNRX-5236 rescued the in vitro activity of ceftibuten against Enterobacterales carrying common serine β-lactamases, including ESBL, AmpC and the KPC and OXA-48-like carbapenemases. Ceftibuten/VNRX-5236 may have potential as an oral treatment for infections caused by resistant Enterobacterales, while sparing carbapenems.

Antifungal drugs work together to treat germs causing fungal infections

Life-threatening infections can be caused by a fungus called Candida auris (shortened to C. auris) that is found in the hospital environment. This study looked at how well different drugs could treat C. auris infection. Samples were collected from 36 people who had C. auris infection. The samples were treated with single drugs and in combination. We found that the main drug types did not work on most samples. Genetic differences we found in the C. auris samples could explain why the main drugs did not work. However, a drug called isavuconazole worked on almost all samples. We also found that a drug called anidulafungin worked better against C. auris when it was combined with either isavuconazole or another drug called voriconazole. To read the full Plain Language Summary of this article, click on the View Article button above and download the PDF.

Comparative activity of posaconazole and systemic azole agents against clinical isolates of filamentous fungi from a global surveillance programme

Objectives

The activity of mould-active azoles was evaluated against 397 filamentous fungi causing invasive mould infections (IMI) worldwide. In addition, a tentative posaconazole epidemiological cut-off value (ECV) against Aspergillus fumigatus was investigated.

Methods

Isolates were susceptibility tested by the CLSI reference broth microdilution methods. Species identification was confirmed by MALDI-TOF and/or sequencing analysis.

Results

Aspergillus spp. (81.9%) remained the most common organism causing IMI worldwide; approximately two-thirds of Aspergillus spp. recovered were A. fumigatus. In general, more than 90% of 220 A. fumigatus isolates were wild type (WT) to all mould-active azoles, except itraconazole (84.5% WT). The voriconazole non-susceptible (NS) A. fumigatus rate was 7.7% overall and was higher in Europe (12.9%) than in the other regions (0%–5.8%). Posaconazole (MIC₅₀/MIC₉₀, 0.25/0.5 mg/L) showed similar or slightly higher activity than voriconazole (MIC₅₀/MIC₉₀, 0.5/0.5 mg/L) and isavuconazole (MIC₅₀/MIC₉₀, 0.5/1 mg/L) against A. fumigatus. The mould-active azoles displayed similar activity against non-fumigatus Aspergillus (WT rates >93%), but differences were observed among the main species/sections. Posaconazole, voriconazole, and isavuconazole inhibited at their respective ECVs 100%, 97.0%, and 100% of A. section Nigri; 100%, 100%, and 93.8% of A. section Terrei; and 97.3%, 100%, and 100% of A. section Flavi isolates. Posaconazole displayed potency greater than or equal to the other azoles against the Mucorales group and Scedosporium spp.

Conclusions

Posaconazole and other mould-active azoles showed good activity against Aspergillus spp. causing IMI, but clinicians should be aware of regional rates of voriconazole-NS A. fumigatus.

Tedizolid activity against a multicentre worldwide collection of Staphylococcus aureus and Streptococcus pneumoniae recovered from patients with pneumonia (2017-2019)

OBJECTIVES

The antimicrobial activity of tedizolid and comparators was evaluated against a large worldwide collection of Staphylococcus aureus and Streptococcus pneumoniae isolates recovered from patients with pneumonia.

METHODS

Clinical isolates were collected from patients in 96 medical centres in the Asia-Pacific region, Europe, Latin America and the USA between 2017 and 2019, and tested for susceptibility by reference broth microdilution.

RESULTS

The most active agents against S. aureus (n = 4667) were tedizolid (100.0% susceptible), linezolid (100.0% susceptible), ceftaroline (96.2% susceptible) and vancomycin (100.0% susceptible), but only tedizolid, linezolid and vancomycin retained activity against >95% of meticillin-resistant S. aureus isolates from all regions. In general, linezolid, ceftriaxone, ceftaroline, levofloxacin, penicillin and vancomycin showed susceptibility rates >95% against S. pneumoniae (n = 3008). However, only linezolid, ceftaroline, levofloxacin and vancomycin remained active (>95% susceptibility) against isolates displaying penicillin-non-susceptible or multidrug-resistant phenotypes. Penicillin-non-susceptible S. pneumoniae isolates were recovered less frequently from patients aged <5 years compared with other age groups.

CONCLUSION

The in-vitro data presented here confirm the high potency of tedizolid against S. aureus and S. pneumoniae causing pneumonia worldwide. There is a need for further clinical evaluations of tedizolid for treating pneumonia caused by these pathogens.

In vitro activity of iclaprim and comparator agents against Listeria monocytogenes clinical isolates from 2012 to 2018

OBJECTIVES

This study examined the in vitro activity of iclaprim and comparators against 40 Listeria monocytogenes clinical isolates mostly (95%) from patients with bloodstream infection (BSI) from the USA, Australia/New Zealand, Latin America and Europe collected between 2012-2018.

METHODS

Antimicrobial susceptibility testing was performed according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Minimum inhibitory concentration (MIC) interpretations were based on CLSI criteria.

RESULTS

The iclaprim MIC₉₀ value for all L. monocytogenes was 0.015 μg/mL. The MIC_50/90 values for iclaprim were 4-fold lower than trimethoprim, the only FDA-approved dihydrofolate reductase inhibitor, against all L. monocytogenes.

CONCLUSION

Iclaprim demonstrated lower MIC values than trimethoprim against a collection (2012-2018) of L. monocytogenes clinical isolates mostly from patients with BSI from the USA, Australia/New Zealand, Latin America and Europe.

1258. Activity of a Series of Investigational Compounds Tested Against Invasive Fungal Isolates

Background

Fox Chase Chemical Diversity Center (FCC) is developing non-peptide analogs of host defense proteins for the treatment of invasive fungal infections mainly caused by Candida (CAN) and Aspergillus (ASP). We evaluated the activity of 6 novel compounds and 2 comparators against 150 isolates from 15 fungal groups.

Methods

Susceptibility testing was performed per CLSI broth microdilution methods for investigational compounds and comparators against 70 CAN and 40 ASP isolates in addition to 10 Cryptococcus spp. (CRYP), 10 Fusarium spp. (FUS), 10 Mucorales, and 10 Scedosporium spp. (SCED) isolates from recent (2017-2019) clinical infections. MIC results were determined as ≥ 50% reduction at 24 and 72 hours for CAN and CRYP respectively, and 100% reduction at 24, 72, and 48 hours for Mucorales, SCED, and other moulds, respectively. CLSI clinical breakpoint (CBP) and epidemiological cutoff value (ECV) interpretive criteria were applied for comparators.

Results

Compounds FC10790, FC11083, FC11212, and FC11275 had MIC₅₀ results at ≤ 0.015 mg/L and MIC₉₀ results at ≤ 0.015 to 0.12 mg/L against CRYP, ASP, and FUS isolates. Compounds FC5096 and FC11022 were 2- to 4-fold less active while demonstrating MIC₅₀ and MIC₉₀ results of 0.03 to 0.5 mg/L against CAN, CRYP, ASP, and FUS isolates. The Mucorales isolate set showed the widest range of MIC results for FC compounds. FC10790 exhibited the greatest potency with a MIC_50/90 at 0.5/2 mg/L. FC compounds showed potent activity against SCED with MIC₉₀ results of 0.03 to 0.25 mg/L. Fluconazole showed a wide range of MIC results, from 0.06 to >64 mg/L, but the highest results observed were for Candida auris (MIC_50/90, 64/ > 64 mg/L) and Candida krusei (MIC_50/90; 16/32 mg/L). Itraconazole was active against all ASP (MIC_50/90, 1/1 mg/L), but showed poor activity against FUS (MIC_50/90, > 8/ > 8 mg/L). Amphotericin B showed a narrow range of MIC results (0.5 to 2 mg/L) for all isolates except 1 ASP and most SCED.

Conclusion

Novel FCC compounds showed equal or greater activity than comparators against most CAN, ASP, SCED, and FUS. FC10790, FC11212, and FC11275 showed the greatest activity against all tested fungal isolates. development of this series of compounds for clinical studies.

Table 1

Disclosures

Paul R. Rhomberg, n/a, Cidara Therapeutics (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Merck (Research Grant or Support) Shawn A. Messer, PhD, Amplyx Pharmaceuticals (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support) Richard W. Scott, PhD, Fox Chase Chemical Diversity Center (Employee) Simon DP Baugh, PhD, Fox Chase Chemical Diversity Center (Employee) Michael A. Pfaller, MD, Amplyx Pharmaceuticals (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support) Mariana Castanheira, PhD, 1928 Diagnostics (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support) Cecilia G. Carvalhaes, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Pfizer (Research Grant or Support)

1547. Activity of Tedizolid and Comparator Agents against Gram-Positive Bacterial Isolates Causing Skin and Skin Structure Infections in Pediatric Patients during 2015-2019 in the US

Background

New strategies to treat acute bacterial skin and skin structure infections (ABSSSI) are needed due to the spread of methicillin-resistant Staphylococcus aureus (MRSA), a common multidrug resistant pathogen of ABSSSIs. Tedizolid (TZD) was approved by the US FDA for treating ABSSSI in adults and is under evaluation for treating pediatric patients. Accordingly, the activity of TZD and comparators was evaluated against clinical surveillance isolates collected from pediatric patients with SSSI in the US.

Methods

A total of 2,758 Gram-positive isolates were collected from pediatric patients with SSSIs in 33 sites in the US between 2015 and 2019 as part of the Surveillance of Tedizolid Activity and Resistance (STAR) Program. Bacterial identification was confirmed by MALDI-TOF MS and susceptibility (S) testing performed by the CLSI reference broth microdilution method. Current CLSI interpretative criteria was applied.

Results

S. aureus (SA; n=2,163; 78.4%) was the most frequent pathogen recovered from all age groups (≤ 1y; 2-5y; 6-12y; 13-17y), followed by β-hemolytic streptococci (BHS; n=460; 16.7%), and coagulase-negative staphylococci (CoNS; n=70; 2.5%). TZD was active against all SA (MIC50/90, 0.12/0.25 mg/L; 100% S). Equivalent TZD MIC50/90 values (0.12/0.25 mg/L) were observed against MRSA (n=886; 41.0%; MIC50/90, 0.12/0.25 mg/L) and methicillin susceptible (MSSA; MIC50/90, 0.12/0.25 mg/L) isolates, regardless the age group. TZD also was very active against BHS (MIC50/90, 0.12/0.25 mg/L; 100% S, regardless of species). TZD, linezolid, and daptomycin had 100.0% S rates against the main Gram-positive species and organism groups (Figure). Ceftaroline and clindamycin showed S rates of &gt;90% against MRSA, MSSA, S. pyogenes and S. dysgalactiae. Lower S rates were observed for clindamycin against VGS (88.2%) and S. agalactiae (64.1%). TZD was the most potent agent (MIC90, 0.25 mg/L) against Enterococcus faecalis (n=30, 1.1%), and a vancomycin-resistance phenotype was observed in 1 (3.3%) isolate.

Conclusion

TZD was highly active against Gram-positive clinical isolates responsible for SSSI in pediatric patients across US hospitals from a 5-year period. TZD was equipotent or more potent than comparators against MSSA and MRSA isolates.

Table 1

Disclosures

Cecilia G. Carvalhaes, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Pfizer (Research Grant or Support) Helio S. Sader, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Melinta (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support) Paul R. Rhomberg, n/a, Cidara Therapeutics (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Merck (Research Grant or Support) Mariana Castanheira, PhD, 1928 Diagnostics (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support) Rodrigo E. Mendes, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support)

Media for colistin susceptibility testing does not improve the detection of Klebsiella pneumoniae isolates carrying MgrB disruption and other mutation driven colistin resistance mechanisms

We evaluated different susceptibility testing media against 200 Klebsiella pneumoniae isolates that have been genetically characterized for the presence of polymyxin resistance mechanisms. The media evaluated included calcium enriched media that was described to promote separation of mcr-carrying Enterobacterales isolates and standard cation-adjusted Mueller-Hinton broth with and without polysorbate 80. The testing conditions evaluated did not show improvement in the separation of isolates carrying MgrB alterations and other mutation-driven polymyxin resistance mechanisms.

Activity of a Long-Acting Echinocandin, Rezafungin, and Comparator Antifungal Agents Tested against Contemporary Invasive Fungal Isolates (SENTRY Program, 2016 to 2018)

We evaluated the activity of rezafungin and comparators, using Clinical and Laboratory Standards Institute (CLSI) broth microdilution methods, against a worldwide collection of 2,205 invasive fungal isolates recovered from 2016 to 2018. Candida (n = 1,904 isolates; 6 species), Cryptococcus neoformans (n = 73), Aspergillus fumigatus (n = 183), and Aspergillus flavus (n = 45) isolates were tested for their susceptibility (S) to rezafungin as well as the comparators caspofungin, anidulafungin, micafungin, and azoles. Interpretive criteria were applied following CLSI published clinical breakpoints (CBPs) and epidemiological cutoff values (ECVs). Isolates displaying non-wild-type (non-WT) echinocandin MIC values were sequenced for hot spot (HS) mutations. Rezafungin inhibited 99.8% of Candida albicans isolates (MIC50/90, 0.03/0.06 μg/ml), 95.7% of Candida glabrata isolates (MIC50/90, 0.06/0.12 μg/ml), 97.4% of Candida tropicalis isolates (MIC50/90, 0.03/0.06 μg/ml), 100.0% of Candida krusei isolates (MIC50/90, 0.03/0.06 μg/ml), and 100.0% of Candida dubliniensis isolates (MIC50/90, 0.06/0.12 μg/ml) at ≤0.12 μg/ml. All (329/329 [100.0%]) Candida parapsilosis isolates (MIC50/90,1/2 μg/ml) were inhibited by rezafungin at ≤4 μg/ml. Fluconazole resistance was detected among 8.6% of C. glabrata isolates, 12.5% of C. parapsilosis isolates, 3.2% of C. dubliniensis isolates, and 2.6% of C. tropicalis isolates. The activity of rezafungin against these 6 Candida spp. was similar to the activity of the other echinocandins. Detection of the HS mutation was performed by sequencing echinocandin-resistant or non-WT Candida isolates. Good activity against C. neoformans was observed for fluconazole and the other azoles, whereas the echinocandins, including rezafungin, displayed limited activity. Rezafungin displayed activity similar to that of the other echinocandins against A. fumigatus and A. flavus These in vitro data contribute to accumulating research demonstrating the potential of rezafungin for preventing and treating invasive fungal infections.

701. Comparison of MIC Results for Gepotidacin by Agar Dilution and Broth Microdilution Methods

Background

Gepotidacin (GSK2140944) is a novel triazaacenaphthylene bacterial type II topoisomerase inhibitor in clinical development for the treatment of gonorrhea and uncomplicated UTI (acute cystitis). Gepotidacin selectively inhibits bacterial DNA gyrase and topoisomerase IV by a unique mechanism not utilized by any currently approved therapeutic agent and demonstrates in vitro activity against most target pathogens resistant to established antibacterials, including fluoroquinolones. This study tested the equivalency of minimal inhibitory concentrations (MICs) obtained by 2 reference susceptibility testing methods, agar dilution (AD) and broth microdilution (BMD), for gepotidacin against Gram-positive and Gram-negative organisms.

Methods

Susceptibility testing for both methods was performed on a total of 733 clinical isolates recovered largely in 2016 from over 120 medical centers worldwide. For N. gonorrhoeae, only the AD method is recommended by CLSI, therefore BMD was performed using Fastidious Broth for comparison purposes. Essential agreement (EA) based on evaluable results was calculated as the number of isolates with MICs within one 2-fold dilution of the reference method divided by the total number of results. Equivalency was defined using the 95% criteria from the FDA’s class II controls document.

Results

The EA observed for gepotidacin with these 2 methods was 85.8% overall and 98.3% when H. influenzae and N. gonorrhoeae isolates were excluded. Slightly higher gepotidacin MICs were observed when tested by BMD for each of these species/groups; this trend was especially prominent for E. coli and S. pyogenes. Gepotidacin tested against H. influenzae (73.1%) or N. gonorrhoeae (28.6%) species had much lower EAs.

Conclusion

Equivalency (EA >95%) was established between AD and BMD methods for determining gepotidacin susceptibility results against Staphylococcus spp., Streptococcus spp. and E. coli. However, for N. gonorrhoeae and H. influenzae, equivalency between the 2 methods was not established; therefore, future antimicrobial susceptibility testing for gepotidacin against these organisms should adhere to the methods for which quality control ranges and breakpoints are approved.

Disclosures

All authors: No reported disclosures.

2115. Activity of a Long-Acting Echinocandin Rezafungin and Comparator Antifungal Agents Tested against Contemporary Invasive Fungal Isolates: SENTRY 2018

Background

Echinocandins are the first-line treatment of candidemia. We evaluated the activity of rezafungin (RZF), a novel long-acting echinocandin with front-loaded drug exposure and extensive distribution to sites of infection, and comparators using CLSI broth microdilution methods against 709 invasive fungal isolates collected worldwide during 2018.

Methods

Susceptibility (S) tests on 663 Candida spp. (6 species), 21 C. neoformans (CNEO), and 25 A. fumigatus (ASF) were conducted for RZF, anidulafungin (ANF), caspofungin (CSF), micafungin (MCF), and azoles. CLSI clinical breakpoint (CBP) and epidemiological cutoff value (ECV) interpretive criteria were applied. Isolates displaying echinocandin MIC>ECV were sequenced for fks hot spot (HS) mutations.

Results

RZF inhibited 99.7% of C. albicans (CA) isolates (MIC_50/90, 0.015/0.06 mg/L), 100.0% of C. tropicalis (CT) (MIC_50/90, 0.03/0.06 mg/L), 98.9% of C. glabrata (CG) (MIC_50/90, 0.03/0.06 mg/L), 100.0% of C. krusei (CK) (MIC_50/90, 0.015/0.12 mg/L), and 100.0% of C. dubliniensis (CD) (MIC_50/90, 0.03/0.06 mg/L) at ≤0.12 mg/L. All (104/104 [100.0%]) C. parapsilosis (CP) isolates (MIC_50/90,1/2 mg/L) were inhibited by RZF at ≤2 mg/L. Fluconazole resistance was detected among 9.0% of CG, 17.3% of CP, and 1.6% of CT. The activity of RZF against these 6 Candida spp. was similar to that of the other echinocandins, the vast majority of which were susceptible/wild type (WT) using CBP/ECV. A total of 5 isolates (3 CG, 1 CA, and 1 CT) displayed 1 or more non-WT or-resistant MIC values and were sequenced for fks HS mutations. Fluconazole and other azoles displayed good activity against CNEO whereas echinocandins including RZF displayed limited activity against CNEO isolates. Echinocandins displayed good activity against ASF, and RZF activity was similar to that of anidulafungin, caspofungin, and micafungin. All but 1 isolate (non-WT MIC for itraconazole, 2 mg/L) displayed WT MIC values for the mould-active azoles.

Conclusion

Rezafungin was as active as other echinocandins against common organisms recovered from invasive fungal infections. These in vitro data contribute to accumulating research demonstrating rezafungin potential for prevention and treatment of invasive fungal infection.

Disclosures

All authors: No reported disclosures.

Analysis of global antifungal surveillance results reveals predominance of Erg11 Y132F alteration among azole-resistant Candida parapsilosis and Candida tropicalis and country-specific isolate dissemination

This study evaluated the activity of echinocandins, azoles and amphotericin B against Candida spp. isolates and other yeasts and characterised azole resistance mechanisms in Candida parapsilosis and Candida tropicalis. Invasive Candida spp. isolates (n = 2936) collected in 60 hospitals worldwide during 2016-2017 underwent antifungal susceptibility testing by broth microdilution. Azole-resistant C. parapsilosis and C. tropicalis were submitted to qPCR for ERG11, CDR1 and MDR1, and the whole genome sequence was analysed. Results of non-susceptibility to echinocandins ranged from 0.0-2.3%, being highest in Candida glabrata. More than 99.0% of the Candida albicans isolates were susceptible to both fluconazole and voriconazole. Fluconazole resistance in C. glabrata was 6.5% overall, being highest in the USA (13.0%). Resistance to voriconazole in Candida krusei was only noted in the USA (5.0%). Azoles inhibited 89.1-91.6% of C. parapsilosis isolates, with most resistant isolates noted in Europe (15.1%), including 36 isolates from Italy (three hospitals), of which 34 harboured Erg11 Y132F mutations and overexpressed MDR1. Azole non-wild-type C. tropicalis (7/227) were found in five countries: 3 isolates from Thailand had the same Erg11 Y132F alteration. Fluconazole non-wild-type isolates were noted among 3/77 (3.9%) Candida dubliniensis, 4/17 (23.5%) Candida guilliermondii, 4/47 (8.5%) Candida lusitaniae and other less common yeast species. Echinocandin use has been recommended over fluconazole for invasive Candida infections. However, azoles are still active against the most common Candida spp. and resistance appears to be restricted to certain geographic regions and associated with Erg11 Y132 alterations in C. parapsilosis and C. tropicalis.

Antimicrobial Resistance Surveillance and New Drug Development

Surveillance represents an important informational tool for planning actions to monitor emerging antimicrobial resistance. Antimicrobial resistance surveillance (ARS) programs may have many different designs and can be grouped in 2 major categories based on their main objectives: (1) public health ARS programs and (2) industry-sponsored/product-oriented ARS programs. In general, public health ARS programs predominantly focus on health care and infection control, whereas industry ARS programs focus on an investigational or recently approved molecule(s). We reviewed the main characteristics of industry ARS programs and how these programs contribute to new drug development. Industry ARS programs are generally performed to comply with requirements from regulatory agencies responsible for commercial approval of antimicrobial agents, such as the US Food and Drug Administration, European Medicines Agency, and others. In contrast to public health ARS programs, which typically collect health care and diverse clinical data, industry ARS programs frequently collect the pathogens and perform the testing in a central laboratory setting. Global ARS programs with centralized testing play an important role in new antibacterial and antifungal drug development by providing information on the emergence and dissemination of resistant organisms, clones, and resistance determinants. Organisms collected by large ARS programs are extremely valuable to evaluate the potential of new agents and to calibrate susceptibility tests once a drug is approved for clinical use. These programs also can provide early evaluations of spectrum of activity and postmarketing trends required by regulatory agencies, and the programs may help drug companies to select appropriate dosing regimens and the appropriate geographic regions in which to perform clinical trials. Furthermore, these surveillance programs provide useful information on the potency and spectrum of new antimicrobial agents against indications and organisms in which clinicians have little or no experience. In summary, large ARS programs, such as the SENTRY Antimicrobial Surveillance Program, contribute key data for new drug development.

Evaluation of the Revised Ceftaroline Disk Diffusion Breakpoints When Testing a Challenge Collection of Methicillin-Resistant Staphylococcus aureus Isolates

We assessed ceftaroline disk diffusion breakpoints for Staphylococcus aureus when applying revised Clinical and Laboratory Standards Institute (CLSI) ceftaroline MIC breakpoints. Disk-MIC correlation was evaluated by testing a challenge collection (n = 158) of methicillin-resistant S. aureus (MRSA) isolates composed of 106 randomly selected isolates plus 52 isolates with decreased susceptibility to ceftaroline (MIC, 1 to 16 μg/ml). Disk diffusion was performed with 30-μg disks and Mueller-Hinton agar from 2 manufacturers each. Revised CLSI susceptible (S)/susceptible dose-dependent (SDD)/resistant (R) MIC breakpoints of ≤1/2 to 4/≥8 μg/ml were applied. The disk breakpoints that provided the lowest error rates were CLSI S/R breakpoints of ≥25 mm/≤19 mm, with no very major (VM) or major (Ma) errors and with minor (Mi) error rates of 0.0% for ≥2 doubling dilutions above the I or SDD (≥I + 2), 22.1% for I or SDD plus or minus 1 doubling dilution (I ± 1), and 2.3% for ≤2 doubling dilutions below the I or SDD ≤I - 2 (overall Mi error rate, 16.5%). No mutation in the penicillin-binding protein 2a (PBP2a) was observed in 5 of 15 isolates with a ceftaroline MIC of 2 μg/ml; 3 of 11 isolates with a ceftaroline MIC of 1 μg/ml exhibited mutations in the penicillin-binding domain (PBD; 1 isolate) or in the non-PBD (2 isolates). All isolates except 1, with a ceftaroline MIC of ≥4 μg/ml, showed ≥1 mutation in the PBD and/or non-PBD. In summary, results from the disk diffusion method showed a good correlation with those from the reference broth microdilution method. Our results also showed that the ceftaroline MIC distribution of isolates with no mutations in the PBP2a goes up to 4 μg/ml, and reference broth microdilution and disk diffusion methods do not properly separate wild-type from non-wild-type isolates.

2373. Evaluation of Delafloxacin Activity and Treatment Outcome for Phase 3 Acute Bacterial Skin and Skin Structure Infection Clinical Trial Anaerobic Isolates

Background

Delafloxacin (DLX) is a broad-spectrum fluoroquinolone (FQ) antibacterial; approved in 2017 by the Food and Drug Administration for treatment of acute bacterial skin and skin structure infections (ABSSSIs). DLX is in clinical development for community-acquired bacterial pneumonia (CABP). In this study, in vitro susceptibility (S) for DLX and comparator agents for Gram-negative (GN) and Gram-positive (GP) anaerobic isolates from Phase 3 ABSSSI clinical trials were determined and compared with the microbiologic response for evaluable isolates.

Methods

A total of 84 anaerobic isolates were collected during Phase 3 ABSSSI clinical trials and 9 additional Bacteroides fragilis (BF) were collected as part of the 2017 SENTRY surveillance program. The isolates tested included 11 BF, 13 Clostridium perfringens (CP), and other species with <10 isolates (table). Isolate identifications were confirmed by molecular methods. Susceptibility testing was performed according to CLSI agar dilution methodology (M11, 2012). Other antimicrobials tested included clindamycin (CD), metronidazole (MTZ), and moxifloxacin (MXF). In addition, the activity of DLX and MXF were compared at standard pH 7.0 and at pH 6.0.

Results

DLX had the lowest MIC_50/90 values against both GP and GN species and was 32-fold more active than MXF for all organisms. For BF, DLX was 4- to 16-fold more active than the other comparators. For CP, DLX was 32- to 64-fold more active than the 3 comparators. When comparing the activity of DLX and MXF at pH 6 vs. pH 7, DLX had the same MIC_50/90 values while MXF MIC_50/90 values were 2-fold less active at the lower pH (Table 1). Of the 84 clinical trial isolates, 21 were recovered from subjects in the microbiologically evaluable at follow-up (MEFU) population. All of the subjects had a favorable microbiological response (presumed eradication) at FU.

Conclusion

DLX demonstrated potent in vitro antibacterial activity against anaerobic isolates tested, including BF and CP and was more active than MXF. For all isolates combined, DLX activity was unchanged at lower pH while MXF MIC values increased 2-fold. These data suggest that DLX activity remains potent at a lower pH common at sites of infection.

Disclosures

D. Shortridge, Melinta Therapeutics: Research Contractor, Research support. S. P. McCurdy, Melinta Therapeutics: Employee, Salary. P. R. Rhomberg, Melinta Therapeutics: Research Contractor, Research support. M. D. Huband, Melinta Therapeutics: Research Contractor, Research support. R. K. Flamm, Melinta Therapeutics: Research Contractor, Research support.

2400. Activity of a Long-Acting Echinocandin, Rezafungin, Tested Against Invasive Fungal Isolates Collected Worldwide

Background

Methods

Results

Conclusion

Disclosures

Activity of fosfomycin when tested against US contemporary bacterial isolates

Fosfomycin and comparators were susceptibility tested against over 2200 contemporary clinical isolates from US medical centers. Fosfomycin was active against Enterobacterales (MIC_50/90, 4/16 μg/mL), including multidrug-resistant isolates. Potent activity was exhibited against gram-positive organisms, including Staphylococcus aureus (MIC_50/90, 4/8 μg/mL). Fosfomycin may provide a promising alternative option for treatment of infections where resistant bacteria may occur.

Activity of omadacycline tested against Streptococcus pneumoniae from a global surveillance program (2014)

The activity of omadacycline and comparators when tested against a subset of Streptococcus pneumoniae from US and European regions of a 2014 global surveillance program (304 isolates) are reported. These MIC results were compared to those obtained when testing S. pneumoniae from 2010 surveillance (1,834 isolates). The omadacycline MIC_50/90 for S. pneumoniae (2014) was 0.06/0.06μg/mL, similar to 2010 (MIC_50/90, 0.06/0.12μg/mL). The omadacycline MIC₉₀ (0.06-0.12μg/mL) was similar for the penicillin-susceptible, -intermediate, -resistant, multidrug-resistance (MDR; ≥3 classes), and ceftriaxone nonsusceptible subgroups. Omadacycline MIC₉₀ values were 0.06-0.12μg/mL for S. pneumoniae from the US and Europe. There was a high degree of resistance with doxycycline, erythromycin and trimethoprim-sulfamethoxazole in both US and EU. For penicillin-resistant S. pneumoniae, resistance to doxycycline and tetracycline in US/Europe was 64.2/61.0% and 63.8/60.5%, respectively, erythromycin 91.2/75.1, and ceftriaxone 7.3/4.0%. The potent activity of omadacycline against S. pneumoniae indicates that omadacycline merits further study in bacterial pneumonia, especially where MDR may be a concern.

In Vitro Evaluation of Delafloxacin Activity when Tested Against Contemporary community-Acquired Bacterial Respiratory Tract Infection Isolates (2014–2016): Results from the Sentry Antimicrobial Surveillance Program

Background

Delafloxacin (DLX) is a broad-spectrum fluoroquinolone (FQ) antibacterial that has completed clinical development (oral and intravenous formulations) with the new drug application currently under the Food and Drug Administration review for the treatment of acute bacterial skin and skin structure infections (ABSSSI). DLX is also in clinical trials for community-acquired bacterial pneumonia. In this study, in vitro susceptibility results for DLX and comparator agents were determined for clinical isolates from community-acquired respiratory tract infections (CA-RTI) collected in medical centers in the United States and Europe participating in the SENTRY surveillance program during 2014–2016.

Methods

A total of 3,093 isolates that included 1,673 Streptococcus pneumoniae (SPN), 805 Haemophilus influenzae (HI) and 555 Moraxella catarrhalis (MC) were collected during 2014–2016 and included only 1 isolate/patient/infection episode. Isolate identifications were confirmed at JMI Laboratories. Susceptibility testing was performed according to CLSI reference broth microdilution methodology, and results were interpreted per CLSI (2017) breakpoints. Other antibacterials tested included levofloxacin (LVX) and penicillin. Β-lactamase production for HI and MC was determined by the nitrocephin disk test.

Results

DLX demonstrated potent in vitro activity against SPN (MIC50/90 0.015/0.03 mg/L). Activity remained the same for penicillin-intermediate or -resistant isolates. For 23 LVX nonsusceptible SPN, the DLX MIC50/90 were 0.12/0.25 mg/L with all isolates having DLX MIC values ≤1 mg/L. For HI, the DLX MIC50/90 were ≤0.001/0.004 mg/L, and for MC the MIC50/90 were 0.008/0.008 mg/L. DLX activity was unaffected by the presence of β-lactamase for either HI or MC. Activity of DLX was similar for US and European isolates.

Conclusion

Delafloxacin demonstrated potent in vitro antibacterial activity against CA-RTI pathogens, including SPN, HI, and MC. These data support the continued study of DLX as a potential treatment for community-acquired pneumonia.

Disclosures

D. Shortridge, Melinta Therapeutics: Research Contractor, Research grant;

J. M. Streit, Melinta Therapeutics: Research Contractor, Research grant; M. D. Huband, Melinta Therapeutics: Research Contractor, Research grant; P. R. Rhomberg, Melinta Therapeutics: Research Contractor, Research grant; R. K. Flamm, Melinta Therapeutics: Research Contractor, Research grant

CD101, a long-acting echinocandin, and comparator antifungal agents tested against a global collection of invasive fungal isolates in the SENTRY 2015 Antifungal Surveillance Program

CD101 is a novel echinocandin with exceptional chemical stability and long-acting pharmacokinetics. The activity of CD101 and comparators was evaluated using CLSI broth microdilution methods against 713 invasive fungal isolates, including 589 Candida spp. (6 species), 14 C. neoformans, 97 A. fumigatus and 13 A. flavus species complex collected worldwide during 2015. All C. tropicalis, C. krusei and C. dubliniensis, 99.7% of C. albicans and 98.3% of C. glabrata were inhibited by ≤0.12 µg/mL of CD101, and these isolates were susceptible/wild type to other echinocandins using CLSI clinical breakpoint and epidemiological cutoff value (ECV) interpretive criteria. C. parapsilosis displayed higher MIC values (range 0.25-2 µg/mL), but similar results were observed for other echinocandins. One C. glabrata and one C. albicans with CD101 MIC value at 1 and 0.25 µg/mL possessed F625S and S645P alterations on FKS1, respectively. These isolates also displayed elevated MIC values for at least one clinically available echinocandin. Fluconazole resistance was noted for 6.6% of C. glabrata and 3.6% C. parapsilosis. Echinocandins had limited activity against C. neoformans. CD101 activity against A. fumigatus and A. flavus (MEC ≤0.03 µg/mL) was comparable to other echinocandins (MEC ≤0.03 µg/mL). These moulds had MIC values below ECVs for the mould-active azoles. CD101 was as active as other echinocandins against common fungal organisms recovered from invasive fungal infections. The extended half-life profile is very desirable as less frequent dosing of this agent should facilitate shorter and more cost-effective hospital stays, improve compliance for outpatients, and provide more convenient outpatient prophylaxis.

In Vitro Activity of Delafloxacin Tested against Isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis

Delafloxacin, an investigational anionic fluoroquinolone, is active against a broad range of Gram-positive and Gram-negative bacteria. In this study, 200 Streptococcus pneumoniae (plus 30 levofloxacin-resistant isolates), 200 Haemophilus influenzae, and 100 Moraxella catarrhalis isolates selected primarily from the United States (2014) were tested against delafloxacin and comparator agents. Delafloxacin was the most potent agent tested. MIC50 and MIC90 values against all S. pneumoniae isolates were 0.008 and 0.015 μg/ml. Delafloxacin susceptibility was not affected by β-lactamase status against H. influenzae and M. catarrhalis.

In vitro spectrum of pexiganan activity; bactericidal action and resistance selection tested against pathogens with elevated MIC values to topical agents

Pexiganan, in Phase 3 clinical development for topical use, exhibited bactericidal activity in vitro against Gram-positive and -negative isolates and was also shown to have a low potential for resistance development in broth serial passage experiments. Susceptibility studies were performed against bacterial isolates (110 total from 2004 to 2013; primarily from skin and soft tissue infections) selected for elevated MIC values (non-wildtype [WT] distributions) to bacitracin, polymyxin B, neomycin, mupirocin, retapamulin, fusidic acid, or gentamicin. A narrow range of pexiganan MIC values (4-32 μg/mL) against Staphylococcus aureus was observed (MIC50 and MIC90 values, 16 μg/mL) with a pexiganan mode and MIC50 value for the subsets of isolates with non-WT MIC values to bacitracin and neomycin (n = 14), fusidic acid (n = 11), mupirocin (n = 12) and retapamulin (n = 11) at 16 μg/mL. For coagulase-negative staphylococci (CoNS), the pexiganan mode and MIC50 values were 4 μg/mL. The pexiganan mode and MIC50 for each non-WT CoNS subset was also 4 μg/mL. Pexiganan MIC values for Enterococcus faecium was 8 μg/mL, but E. faecalis isolates exhibited MIC values that ranged from 128-256 μg/mL. Pexiganan was active against β-hemolytic streptococci including non-WT subsets (MIC range, 4-64 μg/mL). MIC values for pexiganan varied by species for viridans group streptococci, with highest values occurring for Streptococcus oralis. The broad bactericidal spectrum of pexiganan activity and low potential for resistance selection offers the possibility that this experimental agent may be able to play an important role in the current environment of emerging multi-drug resistant pathogens.

Activity of a long-acting echinocandin, CD101, determined using CLSI and EUCAST reference methods, against Candida and Aspergillus spp., including echinocandin- and azole-resistant isolates

Objectives

The objective of this study was to evaluate the in vitro activity of CD101, a novel echinocandin with a long serum elimination half-life, and comparator (anidulafungin and caspofungin) antifungal agents against a collection of Candida and Aspergillus spp. isolates.

Methods

CD101 and comparator agents were tested against 106 Candida spp. and 67 Aspergillus spp. isolates, including 27 isolates of Candida harbouring fks hotspot mutations and 12 itraconazole non-WT Aspergillus, using CLSI and EUCAST reference susceptibility broth microdilution (BMD) methods.

Results

Against WT and fks mutant Candida albicans, Candida glabrata and Candida tropicalis, the activity of CD101 [MIC₉₀ = 0.06, 0.12 and 0.03 mg/L, respectively (CLSI method values)] was comparable to that of anidulafungin (MIC₉₀ = 0.03, 0.12 and 0.03 mg/L, respectively) and caspofungin (MIC₉₀ = 0.12, 0.25 and 0.12 mg/L, respectively). WT Candida krusei isolates were very susceptible to CD101 (MIC = 0.06 mg/L). CD101 activity (MIC_50/90 = 1/2 mg/L) was comparable to that of anidulafungin (MIC_50/90 = 2/2 mg/L) against Candida parapsilosis. CD101 (MIC mode = 0.06 mg/L for C. glabrata) was 2- to 4-fold more active against fks hotspot mutants than caspofungin (MIC mode = 0.5 mg/L). CD101 was active against Aspergillus fumigatus, Aspergillus terreus, Aspergillus niger and Aspergillus flavus (MEC₉₀ range = ≤0.008–0.03 mg/L). The essential agreement between CLSI and EUCAST methods for CD101 was 92.0%–100.0% among Candida spp. and 95.0%–100.0% among Aspergillus spp.

Conclusions

The activity of CD101 is comparable to that of other members of the echinocandin class for the prevention and treatment of serious fungal infections. Similar results for CD101 activity versus Candida and Aspergillus spp. may be obtained with either CLSI or EUCAST BMD methods.

Ceftaroline activity tested against viridans group streptococci from US hospitals

A total of 840 clinically relevant viridans group streptococci (VGS) isolates (1/patient episode) were collected from 71 US medical centers in 2013-2014. These organisms were tested for susceptibility by reference broth microdilution methods against ceftaroline and selected comparator agents. All isolates were speciated by matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry and were primarily from skin/soft tissue (32.6%) and bloodstream (32.3%) infections. Ceftaroline was highly active against all VGS species/groups with MIC50 and MIC90 values ranging from ≤0.015 to 0.03μg/mL and ≤0.015 to 0.06μg/mL, respectively. The highest ceftaroline MIC value was only 0.5μg/mL (0.5% of strains) and ceftaroline (MIC50/90, 0.03/0.06μg/mL) was 8-fold more active than ceftriaxone (MIC50/90, 0.25/0.5μg/mL). The VGS groups most susceptible to ceftaroline were Streptococcus mutans and Streptococcus bovis (MIC90, ≤0.015μg/mL), whereas the highest ceftaroline MIC values were observed among Streptococcus mitis and Streptococcus sanguinis groups. In summary, ceftaroline exhibited potent in vitro activity against VGS, including many uncommonly isolated species/groups for which very limited susceptibility information is currently available to guide therapy.

Antifungal susceptibility patterns of a global collection of fungal isolates: results of the SENTRY Antifungal Surveillance Program (2013)

Among 1846 fungal clinical isolates from 31 countries, echinocandin resistance in Candida spp. ranged from 0.0% to 2.8% (highest for anidulafungin versus Candida glabrata), and fluconazole resistance was noted among 11.9% and 11.6% of the C. glabrata and Candida tropicalis, respectively. Two isolates of Aspergillus fumigatus displayed elevated MICs for itraconazole and carried cyp51a mutations encoding TR34 L98H. All Cryptococcus neoformans had azole MIC values below epidemiological cutoff values. The increasing resistance among certain species and more frequent reports of breakthrough infections in patients undergoing antifungal therapy highlights the importance of antifungal surveillance to guide therapy for patients with invasive fungal infections.

Differences in potency and categorical agreement between colistin and polymyxin B when testing 15,377 clinical strains collected worldwide

Gram-negative bacilli (n=15,377) were tested against colistin (polymyxin E) and polymyxin B by a commercial broth microdilution method (Sensititre®). Among Pseudomonas aeruginosa and Acinetobacter spp., colistin and polymyxin B MIC values were within ±1 doubling dilution for >99.0% of strains. Among Klebsiella spp. and Escherichia coli, 55.0 and 53.2% of strains displayed a colistin MIC 2-fold lower than polymyxin B, but polymyxin B was slightly more potent than colistin against strains with decreased susceptibility to either polymyxin.

Isavuconazole, micafungin, and 8 comparator antifungal agents' susceptibility profiles for common and uncommon opportunistic fungi collected in 2013: temporal analysis of antifungal drug resistance using CLSI species-specific clinical breakpoints and proposed epidemiological cutoff values

The in vitro activities of isavuconazole, micafungin, and 8 comparator antifungal agents were determined for 1613 clinical isolates of fungi (1320 isolates of Candida spp., 155 of Aspergillus spp., 103 of non-Candida yeasts, and 35 non-Aspergillus molds) collected during a global survey conducted in 2013. The vast majority of the isolates of the 21 different species of Candida, with the exception of Candida glabrata (MIC90, 2 μg/mL), Candida krusei (MIC90, 1 μg/mL), and Candida guilliermondii (MIC90, 8 μg/mL), were inhibited by ≤0.25 μg/mL of isavuconazole. C. glabrata and C. krusei were largely inhibited by ≤1 μg/mL of isavuconazole. Resistance to fluconazole was seen in 0.5% of Candida albicans isolates, 11.1% of C. glabrata isolates, 2.5% of Candida parapsilosis isolates, 4.5% of Candida tropicalis isolates, and 20.0% of C. guilliermondii isolates. Resistance to the echinocandins was restricted to C. glabrata (1.3-2.1%) and C. tropicalis (0.9-1.8%). All agents except for the echinocandins were active against 69 Cryptococcus neoformans isolates, and the triazoles, including isavuconazole, were active against the other yeasts. Both the mold active triazoles as well as the echinocandins were active against 155 Aspergillus spp. isolates belonging to 10 species/species complex. In general, there was low resistance levels to the available systemically active antifungal agents in a large, contemporary (2013), global collection of molecularly characterized yeasts and molds. Resistance to azoles and echinocandins was most prominent among isolates of C. glabrata, C. tropicalis, and C. guilliermondii.

Isavuconazole and nine comparator antifungal susceptibility profiles for common and uncommon Candida species collected in 2012: application of new CLSI clinical breakpoints and epidemiological cutoff values

The in vitro activity of isavuconazole and nine antifungal comparator agents was assessed using reference broth microdilution methods against 1,421 common and uncommon species of Candida from a 2012 global survey. Isolates were identified using CHROMagar, biochemical methods and sequencing of ITS and/or 28S regions. Candida spp. were classified as either susceptible or resistant and as wild type (WT) or non-WT using CLSI clinical breakpoints or epidemiological cutoff values, respectively, for the antifungal agents. Isolates included 1,421 organisms from 21 different species of Candida. Among Candida spp., resistance to all 10 tested antifungal agents was low (0.0-7.9 %). The vast majority of each species of Candida, with the exception of Candida glabrata, Candida krusei, and Candida guilliermondii (modal MICs of 0.5 µg/ml), were inhibited by ≤0.12 µg/ml of isavuconazole (99.0 %; range 94.3 % [Candida tropicalis] to 100.0 % [Candida lusitaniae and Candida dubliniensis]). C. glabrata, C. krusei, and C. guilliermondii were largely inhibited by ≤1 µg/ml of isavuconazole (89.7, 96.9 and 92.8 %, respectively). Decreased susceptibility to isavuconazole was most prominent with C. glabrata where the modal MIC for isavuconazole was 0.5 µg/ml for those strains that were SDD to fluconazole or WT to voriconazole, and was 4 µg/ml for those that were either resistant or non-WT to fluconazole or voriconazole, respectively. In conclusion, these data document the activity of isavuconazole and generally the low resistance levels to the available antifungal agents in a large, contemporary (2012), global collection of molecularly characterized species of Candida.