bluuebunny/crossref_metadata_2025 huggingface dataset:
1266. Melatonin for Renal Protection of Patients Treated with Polymyxin B: A Double Blind Randomized Clinical Trial
Authors: Rigatto Maria Helena , Bergo Pedro , Baldissera Giulia , Beck Eduarda , David Leonardo , Santoro Lucas , Falci Diego Rodrigues , Caumo Wolnei , Zavascki Alexandre
Published: December 2021

Background

Polymyxins are one of the last resort treatments for carbapenem resistant gram-negative infections. Nephrotoxicity is its main adverse effect and has been related to oxidative stress mechanisms. Melatonin was associated to reduction in polymyxins nephrotoxicity in animal studies. Our objective is to evaluate the effect of melatonin on renal protection of patients receiving polymyxin B.

Methods

We did a single center, double blind, randomized clinical trial (NCT03725267) of melatonin 30mg versus placebo for patients treated with polymyxin B from October 2018 to April 2021, in Porto Alegre, Brazil. Patients ≥18 years old, receiving polymyxin B for ≤48 hours, who accepted informed consent terms were included and excluded if intensive care unit (ICU) admission at enrollment, estimated glomerular rate estimated glomerular rate < 10ml/min, dialysis or previous melatonin use. Treatment with melatonin or placebo was randomized in blocks of 4 and maintained until the end of polymyxin B treatment of for a maximum of 14 days. Our main outcome was any level of nephrotoxicity by RIFLE score. Secondary outcomes were renal failure and need for dialysis. We estimated a sample size of 100 patients, however the study had to be stopped earlier due to recruitment restrictions imposed by the COVID-19 pandemic.

Results

Eighty-eight patients were randomized, 44 received melatonin and 44 received identical placebo pills. Patients had a mean age of 63.6±17.3 years, 60.2% were male, and had a median Charlson index of 5 (3-8.3). Most infections (79.5%) were microbiologically confirmed, having 68.6% Klebsiella sp isolated. Urinary tract accounted for47.7% of infection sites. Median time of polymyxin B therapy was 9.1±6.6 days. Combination therapy was prescribed for 89.8% of patients and 38.6% received at least another nephrotoxic drug. All variables were equally distributed among groups. Nephrotoxicity rates occurred in 23 of 44 (52.3%) in both groups, P=0.99. Patients who developed renal failure were 8(18.2%) vs 9(20.5%) and dialysis occurred in 4(9.1%) vs 5 (11.4%) of melatonin and placebo groups respectively.

Conclusion

Melatonin did not show a clinically significant renal protective effect in patients treated with polymyxin B.

Disclosures

Maria Helena Rigatto, MD, PhD, CNPq (Grant/Research Support) Diego Rodrigues Falci, MD, MSc, PhD, Gilead Sciences (Grant/Research Support, Scientific Research Study Investigator, Speaker’s Bureau)GSK (Grant/Research Support, Scientific Research Study Investigator, Advisor or Review Panel member)MSD (Speaker’s Bureau)Pfizer (Speaker’s Bureau)United Medical (Speaker’s Bureau, Other Financial or Material Support) Alexandre Zavascki, MD, PhD, Pfizer (Grant/Research Support)
146. Intact Sense of Taste and Smell During COVID-19 Infection Is Associated with Absence of of SARS-CoV-2 Spike Protein Antibody Responses within 3 Months of Symptomatic Illness
Authors: Wilson James M , Gillani Sheena , Bencshop Robert , Poorbaugh Josh , Nirula Ajay , Zhang Lin , Keckler Kody , Weber Kathleen , Morack Ralph , Beasley Stephanie , Brothers Jennifer , Huhn Gregory
Published: December 2021

Background

Although studies show most COVID-19 survivors have post-infection immunity against SARS-CoV-2 that could prevent re-infection, there is still a need to identify the breadth of antibody (Ab) responses associated with clinical phenotypes. We characterized Ab profiles at the estimated peak of Ab diversity among adults with recovered SARS-CoV-2 infections and determined their relationships with clinical factors.

Methods

From April-June 2020, 41 health system employees with PCR-confirmed symptomatic COVID-19 infection enrolled 8-10 weeks after symptom onset. Symptom questionnaires including baseline demographics, COVID-19 symptoms, disease severity, and disease duration were collected and plasma samples were assayed using a custom Luminex Multiplex platform (Figure 1) to measure the antibody response against 20 COVID-19 related antigens (Figure 2). Differences in Ab profile titers among different groups were tested using nonparametric t test and Benjamini-Hochberg adjustment for multiplicity. Associations were considered significant at FDR< 0.05.

Figure 1: Description of the Luminex Serology Assay

Figure 2: List of the COVID-19 Related Antigens and Controls Measured

Results

Mean age was 48 years (range 27-68), with 51% female, 37% White, 32% Black, 29% Asian, and 17% LatinX. Ab profiles (Figure 3) showed 100% cross-reactivity with related alpha and beta coronavirus, and 95% with SARS-CoV-1. 78% had Abs against SARS-CoV-2 nucleocapsid protein (NCP). However, 29% of patients had no immune response against the four spike protein epitopes. These participants also reported fewer symptoms, including no cases of anosmia/ageusia, suggesting mild illness. Anosmia/ageusia, fever, and cough associated significantly with higher Ab titers (Figure 4).

Conclusion

Broad immune responses to various SARS-CoV-2 and related antigens were found among a heterogeneous patient population. However, less than 3 months after symptom onset, protective Ab responses to SARS-CoV-2 spike proteins were not detected in nearly one-third of recovered patients, primarily with mild infection. Intact sense of smell and taste demonstrated the greatest association with loss of seroprotective SARS-CoV-2 Ab responses, which may be clinically useful to predict post-infection immunity. Next steps include comparing the magnitude of Ab responses following full series completion with mRNA vaccination among this cohort.

Disclosures

Robert Bencshop, PhD, Eli Lilly (Employee) Josh Poorbaugh, PhD, Eli Lilly (Employee) Ajay Nirula, MD/PhD, Eli Lilly (Employee, Shareholder) Lin Zhang, PhD, Eli Lilly and Company (Employee, Shareholder) Stephanie Beasley, BA, Eli Lilly (Employee)
1268. In Vitro Activity of Ceftazidime-Avibactam and Comparators against KPC-Producing Enterobacterales and Pseudomonas aeruginosa Collected in China as Part of the ATLAS Global Surveillance Program in 2019
Authors: Wise Mark G G , Kazmierczak Krystyna , Stone Gregory , Sahm Daniel F
Published: December 2021

Background

Among Gram-negative bacteria, the rapid spread of carbapenemases has limited therapeutic options. Klebsiella pneumoniae carbapenemase (KPC), an Ambler class A serine β-lactamase, presents a particular challenge as it has become widespread, first identified in an isolate collected in the United States and thereafter moving throughout the world, including China. Fortunately, the β-lactamase inhibitor avibactam is a potent inhibitor of KPC, rendering many Enterobacterales and some P. aeruginosa isolates that carry KPC susceptible to ceftazidime-avibactam (CAZ-AVI) in vitro. This study reports on the in vitro activity of CAZ-AVI and comparators against Enterobacterales and P. aeruginosa isolates collected in China as part of the Antimicrobial Testing Leadership and Surveillance (ATLAS) program in 2019.

Methods

1,443 non-duplicate Enterobacterales and 522 P. aeruginosa isolates were collected from 17 clinical sites in China in 2019. Susceptibility testing was done using broth microdilution according to CLSI guidelines and interpreted using CLSI 2021 breakpoints. 143/177 meropenem non-susceptible Enterobacterales isolates and 150/187 meropenem non-susceptible P. aeruginosa isolates were interrogated by whole genome sequencing (WGS; Illumina 2x150 bp reads).

Results

Enterobacterales isolates exhibited higher % susceptibility (% S) to CAZ-AVI than all comparators tested (96.0% S; Table). The addition of AVI to CAZ resulted in an increase in susceptibility from 61.3% to 96.0% in the overall collection of Enterobacterales isolates. 96.0% of KPC-positive Enterobacterales, and 67.8% of the meropenem non-susceptible sub-population were susceptible to CAZ-AVI, against which comparators were less active (≤42.9 % S). Among P. aeruginosa isolates, 89.8% were susceptible to CAZ-AVI, more than for any comparator except amikacin (AMK; 94.4% S). Against meropenem non-susceptible and KPC-carrying P. aeruginosa sub-populations more were susceptible to CAZ-AVI (75.9% and 83.3% S, respectively) and AMK (87.2% and 100% S, respectively) than to other comparators (≤40.6% and ≤8.3% S, respectively).

Results Table

Conclusion

CAZ-AVI demonstrated very good in vitro activity against Enterobacterales and P. aeruginosa isolates from China, including those that harbor KPC.

Disclosures

Mark G G. Wise, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Krystyna Kazmierczak, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Gregory Stone, PhD, AztraZeneca (Shareholder, Former Employee)Pfizer, Inc. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor)
1269. Infection, Clinical Syndromes and Antimicrobial Resistance by Aeromonas species: 13-Year Experience with an Emerging Pathogen at a Tertiary Care Center
Authors: Pineda-Reyes Roberto , Orndorff Joseph , Reynoso David
Published: December 2021

Background

Aeromonas spp. are emerging pathogens that cause a wide breadth of clinical syndromes, ranging from acute gastroenteritis to skin and soft tissue infections, sepsis, and “flesh-eating” necrotizing fasciitis. Aeromonads have been associated with natural disasters and have predominance in estuarine ecosystems, generating a negative impact on the fishing industry and aquaculture, as well as morbidity and mortality in human populations at risk. Antimicrobial resistance patterns differ by geographic locations worldwide, and studies to guide the therapy in the era of multidrug resistance are lacking in the US.

Methods

A retrospective case series was designed to chart review all adult subjects who had culture proven Aeromonas spp. infections during the period 2008-2020. Demographic data, water exposure, clinical syndromes on presentation, origin (community-acquired vs. nosocomial) and severity of infection, antibiograms, empirical antibiotics, time-to-appropriate therapy, and treatment outcomes were collected.

Results

Eighty-two subjects were included in the analysis. Demographic and clinical data is summarized in Table 1. Near 20% individuals had water exposure, including 53% of those with traumatic wound infections. Skin and soft tissue infection (including traumatic and surgical wound infections) was the most frequent clinical syndrome (51.2%). Sepsis was present on admission in 33% inpatients. Appropriate antibiotics were instituted in a median of 2 days (IQR=1-5), and the most prescribed empiric agents were piperacillin-tazobactam (48%) and meropenem (13.3%). Most isolates were susceptible to cefepime (70/71, 98.6%), levofloxacin (72/78, 92.3%) and TMP-SMX (69/78, 88.5%). Resistance to meropenem was reported in 18/31 isolates (58.1%) after 2015. Treatment failure was identified in 32.3% cases.

Most cases (55%) were encountered during the months of spring and summer, which have warmer temperatures and seasonal heavy rains. Tropical storms caused significant flooding in the Galveston Bay area and Southeast Texas during the summer of 2015, which interestingly coincides with the high number of cases. However, following Hurricane Ike in 2008 or Hurricane Harvey in 2017, the number of cases did not significantly increase.

Conclusion

Aeromonads are emerging pathogens that cause mainly intraabdominal and skin and soft tissue infections. Their incidence is seasonal (55% cases in spring and summer) and it is associated with water exposure in more than half of those with traumatic wound infections. In subjects with specific risk factors, the use of carbapenem-sparing strategies, such as 3rd or 4th generation cephalosporins, fluoroquinolones or TMP-SMX, may improve outcomes.

Disclosures

All Authors: No reported disclosures
1270. Molecular Characterization of Carbapenemase Producing Enterobacterales, Acinetobacter spp. and Pseudomonas spp. in Nosocomial and Community-acquired Clinical Isolates in Bogota, Colombia
Authors: Reyes Luis F , Bustos-Moya Ingrid G , Josa Diego , Gamboa-Silva Enrique , Ibañez-Prada Elsa Daniela , Africano Hector , Urrego-Reyes Juan , Beltrán Claudia , Leon Sebastian , Ruiz-Cuartas Alejandra , Baron Oscar , Leal Rafael , Hawkey Jane , Wyres Kelly , Stewardson Andrew
Published: December 2021

Background

Antimicrobial resistance (AMR) in low-income and middle-income countries (LMICs) is a public health problem. AMR is a concerning problem in Gram-negative bacteria such are Enterobacterales, which are frequently carbapenem-resistant pathogens (CRP), and few therapeutic options are available. However, scarce data is known regarding the clinical, molecular characteristics, and clinical outcomes of patients infected with carbapenem-resistant pathogens in LMICs. Thus, this study will attempt to bring novel data in these regards.

Methods

This is a retrospective cohort study conducted in two reference hospitals in Colombia, South America. All consecutive patients infected with CRPs between 2017 and 2021 were included. Clinical data were gathered by retrospective chart review. Bacterial pathogens and antibiotic susceptibility were prospectively identified and stored by each hospital. Molecular characterization was performed by PCR in isolated bacteria.

Results

A total of 220 patients were included. The mean (SD) age was 60.6 (18.4) years, and 32% (71/220) were female. The most frequently identified CRPs were Pseudomonas aeruginosa (85/220, 39%) and Klebsiella pneumoniae (81/220, 37%). CRPs were most frequently identified in urine, blood, and respiratory samples (Figure 1). Community-acquired infections were frequently diagnosed in patients infected with CRPs in our study (73% [161/220]), and most of the patients were admitted to the ICU (163/220, 74%). The in-hospital mortality rate was 28% (62/220) and 38% (62/163) in ICU admitted patients. PCR was carried out in 105 CRP; KPC (69%, 73/105) and VIM (37%, 39/105) were the most frequently identified mechanisms. Of the K. pneumoniae isolates with PCR assessment, 94% (33/35) had KPC and 3% (1/35) had VIM. In contrast, in P. aeruginosa isolates with PCR assessment, 53% (29/54) had KPC and 59% (32/54) had VIM. Seven (13%) patients infected with P. aeruginosa had both KPC and VIM genes identified.

Conclusion

The most frequently identified carbapenem-resistant pathogens in these two Colombian reference hospitals were P. aeruginosa and K. pneumoniae, with high mortality rates. KPC was the most commonly identified mechanism of carbapenem resistance in our cohort.

Disclosures

All Authors: No reported disclosures
1271. In vitro Activities of Ceftaroline and Comparator Agents Against Bacterial Pathogens Frequently Causing Community-Acquired Respiratory Tract Infections in Patients from a Global Population: ATLAS Surveillance Program 2016-2019
Authors: Hackel Meredith , Stone Gregory , Sahm Daniel F
Published: December 2021

Background

Community-acquired bacterial pneumonia (CABP) is a frequent cause of patient morbidity and mortality. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are frequent etiologic agents of CABP. Ceftaroline fosamil is a parenteral cephem approved for treatment of patients with CABP caused by S. pneumoniae (including cases with concurrent bacteremia), methicillin-susceptible Staphylococcus aureus (MSSA), H. influenzae, and some species of Enterobacterales. In this study we report the in vitro activity of ceftaroline and comparators against isolates from community-acquired respiratory tract infections (CARTI) collected through a global surveillance program.

Methods

Clinically relevant, non-duplicate, isolates cultured from respiratory specimens by clinical laboratories in 54 countries in 2016-2019 were collected by the ATLAS Surveillance Program central laboratory (IHMA, Schaumburg, IL, USA). In total, 2,636 isolates of S. pneumoniae, H. influenzae, M. catarrhalis, MSSA, and methicillin-resistant S. aureus (MRSA) were tested. The isolates (n/percent of total) originated from Asia/South Pacific (722/27.4%); Europe (1481/56.2%); Latin America (292/11.1%); Middle East/Africa (57/2.2%); and North America (Canada only) (84/3.2%). Ceftaroline and comparator agent MICs were determined by CLSI M07 broth microdilution methodology. MICs were interpreted using 2021 CLSI M100 MIC breakpoints.

Results

Ceftaroline and comparator agent in vitro activities are summarized in the table. Greater than 98% of S. pneumoniae and >99% of MSSA were susceptible to ceftaroline, including penicillin-nonsusceptible S. pneumoniae based on a dosage of 600 mg every 12h. Sixty-four (24.4%) MRSA were ceftaroline-susceptible-dose-dependent (MIC 2-4 µg/mL) based on a dosage of 600 mg every 8h administered over 2h, with the majority from (n) China (70), S. Korea (19), Japan (10), and Chile (8). Three isolates, all from China, were resistant to CPT (MIC of 8 µg/mL). 99.2% of H. influenzae were susceptible to ceftaroline.

Results Table

Conclusion

Ceftaroline demonstrated potent in vitro activity against current pathogens associated with CABP from a global collection.

Disclosures

Meredith Hackel, PhD MPH, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Gregory Stone, PhD, AztraZeneca (Shareholder, Former Employee)Pfizer, Inc. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor)
1273. Activity of Ceftolozane/Tazobactam and Comparators Against Enterobacterales and P. aeruginosa Isolates from Pediatric Patients—SMART United States 2017-2019
Authors: Lob Sibylle , Hackel Meredith , Andrew DeRyke C , Harris Kelly , Young Katherine , Motyl Mary , Sahm Daniel F
Published: December 2021

Background

Ceftolozane/tazobactam (C/T) is an antipseudomonal cephalosporin combined with a β-lactamase inhibitor approved by FDA and EMA for complicated urinary tract (cUTI) and complicated intraabdominal infections (cIAI), as well as hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP) in patients ≥18 years. Clinical trials studying the use of C/T for pediatric patients with cUTI and cIAI are completed, and HABP/VABP pediatric studies are underway. We evaluated the antimicrobial activity of C/T against gram-negative isolates collected from patients ≤17 years in the United States (US) as part of the global SMART surveillance program.

Methods

In 2017-2019, 27 US clinical labs each collected up to 250 consecutive gram-negative pathogens per year. A total of 1336 isolates were collected from pediatric patients. MICs were determined using CLSI broth microdilution and breakpoints. C/T-nonsusceptible Enterobacterales (Ebact) and P. aeruginosa were screened for genes encoding β-lactamases.

Results

Among the 944 collected Ebact and 220 P. aeruginosa isolates, 40.7% and 76.4%, respectively, were collected from patients with respiratory tract infections, 37.0% and 10.0% from UTI, 13.7% and 8.2% from IAI, and 8.3% and 5.0% from bloodstream infections. The table shows antimicrobial susceptibility of Ebact, P. aeruginosa, and select phenotypes. C/T was active against 98% of Ebact, including 50 of 51 and 12 of 13 ESBL-non-CRE phenotype E. coli and K. pneumoniae, respectively. Among P. aeruginosa, C/T was active against 95% of isolates, 9-21 percentage points higher than the comparator β-lactams, and it maintained activity against 71-75% of P. aeruginosa isolates nonsusceptible to commonly used β-lactams. Among the 21 C/T-nonsusceptible Ebact, 2 isolates carried KPC and ESBL and 3 isolates carried only ESBL; in 16 isolates no β-lactamases were detected, of which 15 were species with intrinsic AmpC. Among 12 C/T-nonsusceptible P. aeruginosa, no acquired β-lactamases were detected, likely indicating chromosomally-mediated resistance mechanisms.

Results Table

Conclusion

C/T could be a potential new treatment option for US pediatric patients with infections caused by Ebact and P. aeruginosa, including resistant phenotypes.

Disclosures

Sibylle Lob, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Meredith Hackel, PhD MPH, IHMA (Employee)Pfizer, Inc. (Independent Contractor) C. Andrew DeRyke, PharmD, Merck & Co., Inc. (Employee, Shareholder) Kelly Harris, PharmD, BCPS, Merck & Co. Inc (Employee) Katherine Young, MS, Merck (Employee) Mary Motyl, PhD, Merck & Co., Inc. (Employee, Shareholder) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor)
1274. Activity of Ceftolozane/Tazobactam, Imipenem/Relebactam, and Comparators Against Pseudomonas aeruginosa Isolates from Patients with Bloodstream and Other Infection Types—SMART United States/Canada 2018-2019
Authors: Lob Sibylle , Hackel Meredith , Andrew DeRyke C , Harris Kelly , Young Katherine , Motyl Mary , Sahm Daniel F
Published: December 2021

Background

Ceftolozane/tazobactam (C/T), an antipseudomonal cephalosporin combined with a β-lactamase inhibitor, was approved for treatment of complicated urinary tract (cUTI) and intraabdominal infections (cIAI), and hospital-acquired/ventilator-associated bacterial pneumonia (HAP/VAP). Imipenem/relebactam (IMI/REL) is a combination of imipenem/cilastatin with relebactam, an inhibitor of class A and C β-lactamases. IMI/REL was approved for HAP/VAP and for infections due to aerobic gram-negative organisms in adults with limited treatment options (e.g., cUTI, cIAI). We compared the activity of C/T and IMI/REL against P. aeruginosa from bloodstream infections (BSI) to those from other infection types.

Methods

As part of the SMART program, 24 hospitals in the US and 8 in Canada each collected up to 250 consecutive gram-negative isolates per year in 2018-2019 from patients with BSI, lower respiratory tract infections (LRTI), IAI, and UTI. A total of 2351 Pa isolates were collected. MICs were determined using CLSI broth microdilution and breakpoints.

Results

Pa isolates from BSI tended to show higher susceptibility than IAI, UTI, and especially LRTI isolates (Table). Susceptibility to the tested comparator β-lactams was 11-12 percentage points lower among LRTI than BSI isolates, while C/T and IMI/REL susceptibility was only 2-5% lower. Even among BSI isolates, the comparator β-lactams were active against only 75-88% of isolates, while C/T and IMI/REL were active against >95%. Only amikacin showed higher activity. Analyzing coverage by either C/T or IMI/REL, 98.7% of Pa isolates from BSI were susceptible to one or both agents. C/T and IMI/REL maintained activity against 89% and 69% of meropenem-nonsusceptible (MEM-NS) Pa isolates from BSI (n=36), respectively, and 87% and 76% of piperacillin/tazobactam (P/T)-NS Pa (n=38).

Results Table

Conclusion

Even among BSI isolates, which were generally more susceptible than those from other infection types, Pa susceptibility to commonly used β-lactams like MEM and P/T was < 90%, 7-23% lower than C/T and IMI/REL. Given the desirability of β-lactams among clinicians and the >98% coverage by either C/T or IMI/REL of Pa isolates from BSI, both agents represent important options in the treatment of patients with BSI.

Disclosures

Sibylle Lob, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Meredith Hackel, PhD MPH, IHMA (Employee)Pfizer, Inc. (Independent Contractor) C. Andrew DeRyke, PharmD, Merck & Co., Inc. (Employee, Shareholder) Kelly Harris, PharmD, BCPS, Merck & Co. Inc (Employee) Katherine Young, MS, Merck (Employee) Mary Motyl, PhD, Merck & Co., Inc. (Employee, Shareholder) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor)
1275. Dynamics of Enterococcus faecalis Cardiolipin Synthase Gene Expression Reveal Compensatory Roles in Daptomycin Resistance
Authors: Nguyen April , Polamraju Vinathi , Zhang Rutan , Tran Truc T , Panesso Diana , Khan Ayesha , Mileykovskaya Eugenia , Shamoo Yousif , Xu Libin , Vitrac Heidi , Arias Cesar A
Published: December 2021

Background

Daptomycin (DAP) is a lipopeptide antibiotic targeting membrane anionic phospholipids (APLs) at the division septum, and resistance (DAP-R) has been associated with activation of the E. faecalis (Efs) LiaFSR response and redistribution of APL microdomains (predicted to contain cardiolipin) away from the septum. Efs encodes two putative cardiolipin synthase genes, cls1 and cls2. While changes in Cls1 are associated with DAP-R, the exact roles of each enzyme in resistance are unknown. This work aims to establish the contributions for both enzymes in the development of DAP-R.

Methods

cls1 and cls2 were deleted individually and in tandem from Efs OG117∆liaX (a DAP-R strain with an activated LiaFSR response). Mutants were characterized by DAP minimum inhibitory concentration (MIC) using E-test and localization of APL microdomains with 10-N-nonyl-acridine orange staining. Quantitative PCR (qRT-PCR) was used to study gene expression profiles of cls1 and cls2 in Efs OG117∆liaX relative to Efs OG117. Membrane lipid content was analyzed using hydrophilic interaction chromatography-mass spectrometry (HILIC-MS).

Results

cls1 was highly upregulated in stationary phase concurrent with a decrease in cls2 expression. However, independent deletion of cls1 or cls2 in the DAP-R background resulted in no significant phenotypic changes from the parent strain. Interestingly, qRT-PCR showed that cls2 expression was upregulated upon deletion of cls1 (and vice-versa), suggesting a compensatory role for one enzyme upon deletion of the other (Fig 1). When comparing membrane lipid content between Efs OG117∆liaX∆cls1 and Efs OG117∆liaX∆cls2, there were no significant differences in both the overall amount or species of cardiolipin generated, further supporting a potential redundancy between the cardiolipin synthases (Fig 2). Ultimately, double deletion of both cls genes lowered the DAP MIC relative to the parent strain and restored septal localization of APL microdomains.

Conclusion

Overall, Cls1 has a predominant role in the development of DAP-R in E. faecalis. However, here, we describe a novel compensatory role for Cls2 under conditions in which there is no functional Cls1 to maintain the DAP-R phenotype.

Disclosures

Truc T. Tran, PharmD, Merck (Grant/Research Support) Cesar A. Arias, M.D., MSc, Ph.D., FIDSA, Entasis Therapeutics (Grant/Research Support)MeMed Diagnostics (Grant/Research Support)Merk (Grant/Research Support)
1276. Assessment of Anti-biofilm Activity of Staphylococcus aureus Bacteriophages Against Clinical Isolates from Patients with Left Ventricular Assist Device Infections
Authors: Ramirez-Sanchez Claudia , Attai Hedieh , Van Tyne Daria , Shields Ryan K , Yerushalmy Ortal , Hazan Ronen , Nir-Paz Ran , Pride David , Aslam Saima
Published: December 2021

Background

Staphylococcus aureus is a common cause of biofilm-mediated left ventricular device (LVAD) infections which are difficult to resolve with antibiotics alone and are associated with substantial morbidity and mortality. Recently, bacteriophages (phage) therapy has been used to resolve LVAD infections in a few cases. Our goal was to assess in vitro susceptibility and anti-biofilm activity of two S. aureus bacteriophages against clinical isolates from patients with S. aureus LVAD infections in order to develop a S. aureus phage cocktail for clinical use.

Methods

Two bacteriophages, OMS1 and OMS2, from the Israeli Phage Bank, were assessed for lytic activity against 15 S.aureus isolates (9 methicillin resistant, MRSA and 6 methicillin susceptible, MSSA) via agar overlay method and plaque forming units (PFU)/mL were enumerated. We then formed bacterial biofilms after overnight incubation at 120 rpm in a 96-well plates in duplicate; experiments were repeated thrice. Wells were then treated with tryptic soy broth (TSB, control) or TSB containing phage at 109 PFU/mL for 24 hours. After washing, biofilms were stained with crystal violet and biomass quantified via optical density at 570mm.

Results

All bacterial isolates were susceptible to both phages via agar overlay to varying degrees as determined by phage titers obtained via serial dilutions (Figure 1a, 1b). OMS1 led to significant reduction in biofilm of 7/9 MRSA and 3/6 MSSA isolates and OMS2 reduced biofilms in 9/9 MRSA and 4/6 MSSA isolates (Figure 1c).

Phage titers and Biofilm Biomass

Figure 1a) Phage titers in PFU/ml obtained from each bacterial isolate via agar overlay method. 1b) Representative agar plate demonstrating lytic plaques from OMS1 and OMS2 on a Staphylococcus aureus LVAD isolate. 1c) Biofilm biomass of Staphylococcus aureus isolates alone (SA) or with individual phage (SA+OMSA1 and SA=OMS2) assessed by optical density readings at 570 nm; error bars represent standard error of the mean.

Conclusion

We demonstrated in vitro lytic and anti-biofilm activity of 2 S. aureus phages against clinical S. aureus isolates from patients with LVAD infection. Our data suggests that phage susceptibility measured with agar overlay does not always correlate with phage susceptibility of S. aureus biofilms, suggesting that more than one method should be used to assess in vitro activity. We plan to assess for synergistic activity with the phage combination.

Disclosures

Ryan K. Shields, PharmD, MS, Shionogi (Consultant, Research Grant or Support) Ran Nir-Paz, MD, BiomX (Consultant)Technophage (Scientific Research Study Investigator, Advisor or Review Panel member) Saima Aslam, MD, MS, BioMx (Consultant)Cystic Fibrosis Foundation (Grant/Research Support)Gilead (Consultant)Johnson and Johnson (Consultant)Merck (Consultant)
1277. Colonization Rates for Antimicrobial-resistant Bacteria in Kenya: An Antibiotic Resistance in Communities and Hospitals (ARCH) Study
Authors: Omulo Sylvia , Luvsansharav Ulzii-Orshikh , Ita Teresa , Mugoh Robert , Caudell Mark , Ramay Brooke M , Palmer Guy H , Ndegwa Linus , Verani Jennifer , Bollinger Susan , Sharma Aditya , Call Douglas , Smith Rachel
Published: December 2021

Background

Characterization of antimicrobial-resistant organism (ARO) colonization is critical to understand transmission dynamics and infection risk, however data in resource-limited settings are scare. We estimated the prevalence of Enterobacterales colonization with extended-spectrum cephalosporin-resistance (ESCrE), carbapenem-resistance (CRE) and methicillin-resistant Staphylococcus aureus (MRSA) among community residents and hospitalized patients in rural (Siaya County) and urban (Kibera) Kenya.

Methods

Community-dwelling adults and children were enrolled via cluster randomized sampling. Inpatients of all ages were enrolled by simple random sampling. Stool/rectal and nasal swabs were collected and screened for ESCrE, CRE and MRSA, respectively, using HardyChrom™ media. Vitek2® was used for isolate confirmation and antibiotic susceptibility testing. Fisher’s exact tests were used to compare prevalence of AROs.

Results

The prevalence of ESCrE was higher for the urban hospital (69.8%, 263/377) compared to rural hospitals (62.7%, 298/475, P=0.04); a similar pattern was evident for CRE (16.7%, 63/377 and 6.5%, 31/475, respectively, P< 0.01). The prevalence of MRSA was 3.2% for both urban and rural hospitals (P=0.99). For adults, the prevalence of ESCrE was higher in Kibera households (51.4%, 346/673) compared to Siaya (44.6%, 283/634, P=0.02) while the prevalence of both CRE and MRSA was < 3% for both areas and did not differ significantly (CRE, P=0.13, MRSA, P=0.14). There was no significant difference between urban and rural children for ESCrE (47.7%, 74/155 and 53.4%, 135/253, P=0.31); both CRE and MRSA were rarely detected (< 2%) with no difference across settings (CRE, P=1.0, MRSA, P=0.42). Among Enterobacteriaceae recovered, Escherichia coli and Klebsiella spp. predominated.

Conclusion

Colonization with AROs were widespread in households and hospitals in urban and rural areas. Hospitals with elevated prevalence of highly transmissible AROs should consider whether implementation of colonization screening can be incorporated as part of their infection prevention and control programs. Risk factors for ARO colonization should be elucidated to identify novel prevention strategies.

Disclosures

All Authors: No reported disclosures
1278. Testing the Synergistic Effect of Ceftazidime-Avibactam Plus Aztreonam on Metallobetalactamase-Producing Non-Fermenting Gram-negative Bacteria
Authors: Crouch Elena M , Johnson Sheila , Bennett Jason
Published: December 2021

Background

Metallo-betalactamases (MBL) are rapidly becoming a more widespread form of antimicrobial resistance. MBL are class B betalactamases that use zinc rather than serine in their active site and are only inactivated by monobactams, such as aztreonam. Unfortunately, most MBL-producing organisms also produce aztreonam-inactivating beta-lactamases. Synergy between ceftazidime-avibactam and aztreonam is well documented for MBL-producing Enterobacteriaceae but has not been tested extensively in non-fermenting Gram-negative bacteria. This study evaluates the susceptibilities of non-fermenting Gram-negative bacteria via E-test to this combination in vitro, in order to provide support for use to treat infections from these organisms.

Methods

The antibiotic combination ceftazidime-avibactam+aztreonam was tested against a total of 33 isolates, including MBL-producing Pseudomonas aeruginosa, Pseudomonas putida, and the intrinsically aztreonam resistant Acinetobacter baumanii using the E-test method. MBL-producing Enterobacteriaceae were included as positive controls. All isolates were also tested against ceftazidime alone, aztreonam alone, and ceftazidime-avibactam. Bacterial isolates were procured from the Multidrug-resistant organism Repository & Surveillance Network at the Walter Reed Army Institute of Research. Antimicrobial resistance genes were previously identified by whole genome sequencing

Results

Of 13 Pseudomonas spp. isolates tested, 9 were resistant, 3 were intermediate, and 1 was susceptible to aztreonam. Synergistic testing of ceftazidime-avibactam+aztreonam reduced the MIC of 4 Pseudomonas isolates by 1-2 doubling dilutions. While Acinetobacter spp. are usually considered intrinsically resistant to aztreonam, synergistic testing of ceftazidime-avibactam+aztreonam reduced the MIC of all 12 isolates tested by 1 to 3 doubling dilutions.

Conclusion

The ability of ceftazidime-avibactam+aztreonam to reduce the MICs of Acinetobacter baumanii and MBL-producing Pseudomonas aeruginosa is a potentially promising therapeutic option when faced with growing antimicrobial resistance.

Disclosures

All Authors: No reported disclosures
1283. High Dose Minocycline for the Treatment of Acinetobacter Infections
Authors: Herbin Shelbye R , Ammar Amina , Gumbleton Ryan , Zhao Jing , Olson Shannon , Smith Stephanie M , Scipione Marco R
Published: December 2021

Background

Acinetobacter (ACB) infections are difficult to treat due to increasing drug resistance. The aim of this study is to evaluate the effectiveness of high-dose (HD) minocycline (MIN) 200mg q12h for the treatment of ACB infections

Methods

This is a retrospective study of pts with ACB from 1/1/19 to 10/31/20. Exclusions included non-susceptibility to MIN, age < 18 yrs, hospice care w/in 72 hrs of culture, or urine source. Use of HD MIN (IV or PO), was compared to alternative treatment (AT). Clinical and micro success at the end of therapy (EOT) was evaluated. Clinical success was elimination or improvement in signs and symptoms of infection. Micro success was eradication of ACB from the same site of infection at EOT. Length of stay (LOS), 30-day readmission (with or without ACB), isolation of a MIN non-susceptible ACB within 30 days of EOT, and adverse events related to MIN, were evaluated.

Results

A total of 320 pts were screened with the most common exclusion being MIN non-susceptible isolate. Of the 204 pts included, 38 received HD MIN and 166 received AT. The most common were cefepime (53/166) and meropenem (36/166). Median age (IQR) was 41 (30-50) yrs for HD MIN vs. 40 (27-48) yrs for AT. Both groups were mostly male (HD MIN: 63% vs. AT: 60%) and respiratory was the most common site (HD MIN: 61% vs. AT: 60%). HD MIN group had 74% of cultures that were polymicrobial vs. 86% in AT group. Lack of clinical response at the EOT occurred in 42% of pts on HD MIN and 37% on AT. Infection related mortality occurred in 24% on HD MIN vs. 15% on AT. In HD MIN group, 16 pts had a repeat culture from the same site after treatment with 25% still positive for ACB. In the AT group 61 pts had a repeat culture and 28% were positive for ACB. Duration of treatment (9 [6-11] days vs. 10 [2-18] days) and LOS (16 [18.25-26.75] vs. 29 [14-49]) were shorter in the HD MIN group. There was only one adverse event reported with the use of HD MIN

Conclusion

Pts in the HD MIN group had shorter treatment duration and a shorter LOS. Pts who received HD MIN had a lower rate of clinical cure and a higher mortality rate compared to pts in the AT group. Reasons for this difference will need to be investigated further. HD MIN should be reserved for pts who are unable to tolerate other treatment options or who have an ACB resistant to other treatment options.

Disclosures

All Authors: No reported disclosures
1285. Identification of KPC Omega Loop Variant R163S Conferring Ceftazidime-Avibactam Resistance
Authors: Maris Alexander S , Tao Lili , Wada Paul , Humphries Romney , Humphries Romney , Schmitz Jonathan
Published: December 2021

Background

We report on a 56 year-old male with prolonged COVID-19 pneumonia who initially improved with dexamethasone and intubation but quickly decompensated. Clinical and radiologic features were consistent with VAP. Tracheal aspirate cultures grew carbapenem-resistant Enterobacter cloacae; meropenem (MEM) MIC was >8 ug/ml (resistant) while ceftazidime-avibactam (CZA) MIC was 2/4 ug/ml (susceptible). Lateral flow antigen assay detected a KPC enzyme. The patient was treated with CZA with steady improvement in respiratory function over the next two weeks. He then experienced an episode of tachycardia, prompting repeat culture. At this point the patient had been extubated: sputum culture grew KPC+ E. cloacae that now showed CZA-resistance (MIC >8/4 ug/ml) and paradoxical decrease in MEM MIC (4 ug/ml); meropenem-vaborbactam (< 2/8 ug/ml) was susceptible.

Methods

The pre- & post-CZA therapy E. cloacae isolates underwent whole genome sequencing using the Illumina 150bp paired end protocol; sequences were quality trimmed and compared.

Results

A point mutation in the plasmid blaKPC3 gene was identified in the post-CZA therapy isolate, an R163S mutation in the omega loop of the enzyme. ompC and ompF porin genes were analyzed to rule-out decreased influx as a mechanism for CZA-resistance: the pre- and post-CZA isolates had identical porin sequences.

Conclusion

This case highlights emerging mutations within KPC carbapenemases that lead to resistance to ‘last-line’ antimicrobials like CZA. The presumptive mechanism is increased KPC active site promiscuity due to increased omega loop flexibility, allowing increased ceftazidime binding and hydrolysis, and decreased avibactam binding and beta lactamase inhibition. Paradoxically, MEM susceptibility improves after such omega loop mutations, likely due to decreased active site binding affinity, a ‘seesaw’ effect between MEM and CZA. While authors have reported MEM MICs falling into the ‘susceptible’ category after an omega loop variant, these bacteria invariably develop secondary mutations leading to MEM treatment failure. Fortunately, given our patient’s improved respiratory status, the post-CZA E. cloacae isolate was felt to reflect colonization and the patient was discharged home without antimicrobial therapy.

Disclosures

Romney Humphries, PhD D(ABMM), Accelerate Diagnostics (Individual(s) Involved: Self): Consultant, Shareholder; IHMA (Individual(s) Involved: Self): Consultant; Melinta (Individual(s) Involved: Self): Consultant; Momentum (Individual(s) Involved: Self): Grant/Research Support; Pattern (Individual(s) Involved: Self): Consultant; QPex (Individual(s) Involved: Self): Consultant; ThermoFisher (Individual(s) Involved: Self): Consultant; Torus (Individual(s) Involved: Self): Consultant
1287. Double Disk Diffusion Study to Evaluate the Synergistic Effect Between Cefiderocol and Ceftazidime-Avibactam Against Cefiderocol-Non-susceptible Acinetobacter baumannii
Authors: Yamano Yoshinori , Takemura Miki , Anan Naomi , Echols Roger , Longshaw Christopher
Published: December 2021

Background

Cefiderocol (CFDC), a siderophore cephalosporin, has broad coverage of Gram-negative bacteria and has been approved for clinical use in USA and Europe. The SIDERO-WT surveillance studies showed that CFDC shows >95% susceptibility against Acinetobacter baumannii. Against many of CFDC non-susceptible isolates, most of which had blaPER gene, the combination use of avibactam significantly decreased the MIC by broth microdilution (BMD). In this study, we evaluated the appropriate methodology to evaluate the synergistic effect by disk diffusion studies.

Methods

The susceptibility testing was conducted as recommended by the CLSI using CFDC non-susceptible isolates (MIC of >4 µg/mL based on CLSI breakpoint). The MIC by BMD was determined using iron-depleted cation-adjusted Mueller-Hinton broth, in the presence or absence of 4 µg/mL of avibactam. The disk diffusion was evaluated using Mueller-Hinton agar, and the synergy was evaluated by using disk stacking methods. For disk stacking methods, CFDC disk was placed on agar on which bacterial suspension of 0.5 McFarland units was spread, then the ceftazidime-avibactam (CZA) disks was stacked on the top, followed by adding a drop (30 µL) of saline on the stacked disks. As an alternative method, CZA was immersed in saline for 1 second instead of adding a drop of saline, followed by the stacking on the top. The disk zone size was determined after 24-hour incubation at 37°C.

Results

Against blaPER-positive A. baumannii which showed >64 µg/mL MIC of CFDC and CZA, CFDC MIC decreased to 0.25 µg/mL in the presence of avibactam. The disk diffusion methods also showed isolates resistant to CFDC and CZA and showed susceptiblilty disk zone to CFDC by stacking both disks. On the other hand, against blaNDM-positive A. baumannii which showed 64 µg/mL MIC of CFDC and CZA, the disk diffusion methods showed resistance even when stacking both disks. Against multiple isolates, the MIC of CFDC without or with avibactam was correlated well with the disk zone produced by CFDC disk alone or stacked with CZA disks, respectively (Figure).

Conclusion

The synergistic effect between CFDC and avibactam by BMD methods could be detected by disk stacking methodology using CFDC and CZA disks.

Disclosures

Yoshinori Yamano, PhD, Shionogi (Employee) Miki Takemura, MS, SHIONOGI & CO., LTD. (Employee) Roger Echols, MD, Shionogi (Consultant) Christopher Longshaw, PhD, Shionogi (Employee)
1290. Ceftazidime-Avibactam Resistance Report in a Third Level Hospital in Mexico City
Authors: Molina Aaron , Salinas-Hernandez Abigail , Olmedo-Reneaum Alejandro
Published: December 2021

Background

The surge of resistant Gram-negative organisms has been worrying infectious disease physicians and physicians in general because of the lack of a large number of antibiotics to which these organisms remain susceptible. Ceftazidime-Avibactam (CAZ-AVI) is a drug approved by the FDA to treat complicated urinary tract infections (cUTI), complicated intra-abdominal infections (cIAIs) in combination with metronidazole, and recently for the treatment of nosocomial pneumonia. Worldwide resistance rates of Enterobacteriaceae to CAZ-AVI have been reported below 2.6%, and 4-8% for Pseudomonas aeruginosa. The FDA, CLSI, and EUCAST assigned the clinical breakpoints of susceptibility: MIC < /=8 mg/liter susceptible, and >/=8mg/liter, resistant. In Mexico, CAZ-AVI was approved in 2018, and its cost is very high compared to other antimicrobials, so its use is limited in very specific cases. The resistance rates to this antibiotic in the Mexican population remain largely unknown.

Methods

We tested 106 specimens for susceptibility to ceftazidime-avibactam using the disk Kirby-Bauer method. The inhibition zone diameter was determined in all cases and we considered the organism susceptible when the inhibition zone diameter was >=21 mm, and resistant with an inhibition zone diameter < = 20 mm.

Results

We found 5 specimens (4.71%) resistant to ceftazidime-avibactam, corresponding to E. coli (3) and P. aeruginosa (2). Two of these were also resistant to colistin, and 4 to meropenem. All carbapenem-resistant isolates harbored Metallo-beta-lactamases genes, for E. coli was NDM gen, and for P. aeruginosa the VIM gene(GeneXpert® Cepheid).

Conclusion

The ceftazidime-avibactam resistance among Gram-negative bacteria in our study is similar to the one reported in other international studies. We need more studies in our population to know the nationwide resistance to this antibiotic.

Disclosures

All Authors: No reported disclosures
1292. Evaluation of Synergy with Piperacillin/Tazobactam plus Meropenem Against Carbapenemase-Producing Klebsiella pneumoniae and Enterobacter cloacae Using ETEST
Authors: Ashcraft Deborah S , Vortisch Royanne H , Pankey George A
Published: December 2021

Background

Carbapenem-resistant Enterobacterales are considered an urgent threat for patients in healthcare facilities, causing infections with significant morbidity and mortality. Most isolates are multidrug resistant with limited treatment options, so combination therapy is an alternative. Recently, synergy with piperacillin/tazobactam (P/T) + meropenem (MP) was demonstrated against 7/10 (70%) KPC-producing Escherichia coli and 9/10 (90%) OXA-48-producing K. pneumoniae using time-kill assay (Lawandi et al, 2021). The aim of the present study was to further evaluate the combination of P/T + MP against KPC-producing Enterobacter cloacae, in addition to OXA-producing K. pneumoniae using our rapid ETEST MIC:MIC synergy method.

Methods

14 carbapenemase-producing isolates: 7 OXA-48-like K. pneumoniae (1 OXA-48, 4 OXA-181, 2 OXA-232) and 7 KPC-producing E. cloacae (1 KPC-2, 4 KPC-3, 1 KPC-4, 1 KPC-6) were obtained from the CDC and FDA Antibiotic Resistance Isolate Bank. ETEST MICs for P/T and MP and our ETEST synergy method were performed in triplicate for each isolate. The summation fractional inhibitory concentration was calculated, and the mean value was interpreted as: < 0.5 synergy; > 0.5-1 additivity; > 1-4 indifference; and > 4 antagonism.

Results

MICs (µg/mL) ranged: MP, 0.5 to > 32 (14% susceptible) and P/T, 96/4 to > 256/4 (all resistant). The combination of P/T + MP showed synergy (3) or additivity (2) against 5/7 (71%) OXA-producing K. pneumoniae and synergy (6) or additivity (1) against all 7 KPC-producing E. cloacae. No antagonism was detected.

Conclusion

Using our ETEST MIC:MIC method, the combination of P/T + MP demonstrated synergy or additivity in 5/7 OXA-producing K. pneumoniae and 7/7 KPC-producing E. cloacae, similar to previously published findings showing synergy in 7/10 KPC-producing E. coli and 9/10 OXA-48-producing K. pneumoniae using time-kill assay. Our ETEST synergy method is simple to use and should be evaluated more extensively. Regardless of the method used, results may or may not correlate in an in vivo setting. In vivo studies are needed.

Disclosures

All Authors: No reported disclosures