bluuebunny/crossref_metadata_2025 huggingface dataset:
537. Impact of Active Surveillance Testing (AST) on Rates of Hospital-acquired Carbapenem-Resistant Enterobacteriaceae (CRE)
Authors: Campbell Eileen , Kester Shelley , Layell Jessica , Neelakanta Anupama , Capraro Gerald A , Passaretti Catherine
Published: October 2019

Background

Active surveillance testing (AST) for Carbapenem-resistant Enterobacteriaceae (CRE) to identify and isolate asymptomatic carriers has been recommended to help prevent patient to patient transmission. Optimal screening population, frequency, and testing method remain a subject of debate.

Methods

Beginning in 2012, all clinical cultures yielding a CRE isolate in an 898-bed teaching hospital were reviewed to determine whether the isolate was hospital-acquired (HA). HA CRE rates per 10,000 patient-days were calculated. From 1/2013 to 6/2015, in-house, culture-based point prevalence surveys were performed on rectal swabs from rotating units using the CDC recommended method. 7/2015 through 8/2016, culture-based AST was outsourced to a reference laboratory and AST was expanded to include high-risk patients on admission with weekly sweeps on high-risk units. Of note, revised CLSI breakpoints were implemented by our laboratory in 7/2016, which resulted in an increase in CRE detections. Surveillance was suspended from September 2016 to January 2018 when we resumed AST utilizing in-house PCR for KPC, NDM, OXA48, IMP and VIM mechanisms. Rates of HA CRE were compared between surveillance periods. Cohorting of patients in select units, focus on hand hygiene and isolation, antibiotic stewardship, and CHG bathing were ongoing throughout all time periods.

Results

510 rectal swabs in 424 patients were positive for CRE. Additional clinical cultures yielding CRE were absent in 83% of those patients, so would otherwise have gone undetected. Of those patients with both positive AST and clinical culture, 70% had a positive AST result prior to their clinical culture (range 0–997 days, average 94 days, median 14.5 days prior to clinical culture). Compared with preceding periods with no surveillance, on admission and weekly CRE AST, whether utilizing culture based or PCR based screening, was associated with significantly lower rates of HA CRE. (See Table 1). Rates of HA CRE during the initial point prevalence AST period were unchanged compared with periods with no surveillance. Community-onset CRE did not significantly change in any of the time periods monitored (Figure 2).

Conclusion

On admission and weekly AST was associated with a significant decrease in HA CRE in a large teaching hospital.

Disclosures

All authors: No reported disclosures.
538. Extended-Spectrum β-Lactamase (ESBL): Producing Enterobacteriaceae Surveillance Pilot, New Mexico, 2017
Authors: Phipps Erin C , Flores Kristina , Hancock Emily B
Published: October 2019

Background

Extended-spectrum β-lactamase – producing (ESBL) Enterobacteriaceae pose a serious antibiotic resistance threat, yet gaps remain in our understanding of their epidemiology. New Mexico was one of five Emerging Infection Program (EIP) sites to participate in a surveillance pilot from October 1 to December 31, 2017.

Methods

A case was defined as a resident of Bernalillo County, NM with E. coli, Klebsiella pneumoniae, or Klebsiella oxytoca cultured from urine or normally sterile body sites resistant to at least one extended-spectrum cephalosporin and nonresistant to all carbapenem antibiotics tested. EIP staff assessed prior healthcare exposures, risk factors, and outcomes through medical record review.

Results

NM EIP identified 309 incident cases among 288 individuals; 263 medical records were reviewed. Cases ranged in age from 3–95 years, with a median age of 63 years. Most isolates were E. coli (n = 270, 87.4%); 35 (11.3%) were K. pneumoniae and 4 (1.3%) were K. oxytoca. The majority of isolates were cultured from urine (297, 96.1%). Blood cultures comprised 11 cases (3.6%). The majority of ESBL cultures were collected in an outpatient setting; 15% were collected from hospital inpatients and fewer than 5% from residents of a long-term care facility (LTCF) or long-term acute care hospital (LTACH). However, 21% of those collected in an outpatient setting, primarily the ED, were hospitalized within 30 days.

Over 60% of the cases had at least one relevant risk factor documented in their medical record. One-third had documented antimicrobial use in the prior month, 39% had been hospitalized in the year prior, and 19% had a urinary catheter in place in the 2 days prior to culture collection. Interestingly, while only 2% had documentation of international travel in the two months prior to culture, 18% had either documented international travel outside of that timeframe, or required the use of language interpretation, possibly indicating extensive time living internationally in the past.

Conclusion

Among residents of Bernalillo County, NM, ESBL isolates were predominantly E. coli, cultured from urine in outpatient settings. Over half had documentation of recognized risk factors, including prior hospitalizations, recent antibiotic use, or presence of indwelling devices.

Disclosures

All authors: No reported disclosures.
548. Carbapenem-Resistant Acinetobacter baumannii Antibiotic Susceptibility Testing and Antibiogram Formation, Connecticut 2017–2019
Authors: Paranandi Anu , Maloney Meghan , Grogan Erin , Macierowski Bobbie , Noel Diane , Razeq Jafar , Muyombwe Anthony , Leung Vivian
Published: October 2019

Background

Carbapenem-resistant Acinetobacter baumanii (CRAB) is an infectious disease threat with limited treatment options. Statewide CRAB reporting and isolate submission has been mandated in Connecticut (CT) since 2017, which allowed the creation of a statewide CRAB antibiogram to assist with empiric treatment options for CRAB.

Methods

Clinical CRAB isolates from 2017 through the first quarter of 2019 underwent carbapenemase and expanded susceptibility testing at the CT State Public Health Laboratory or the Antibiotic Resistance Laboratory Network regional lab for carbapenemase and expanded susceptibility testing. Susceptibility testing was done by broth microdilution and disk diffusion, and interpreted using Clinical and Laboratory Standards Institute breakpoints. Carbapenemase producers were detected by the modified carbapenem inactivation method. Polymerase chain reaction testing identified carbapenemase genes.

Results

Of the 64 CRAB isolates submitted, 40 remained after confirmation of carbapenem resistance, i.e., resistance to at least one carbapenem, and deduplication of patients. Of these, 19 were carbapenemase producers (CP), and 21 were non-carpabenemase producers (Non-CP). All isolates were non-susceptible to cefepime, ceftazidime, levofloxacin and all carbapenems. Colistin susceptibilities were available for 33 isolates, 32 (97%) of which were susceptible. Tobramycin susceptibilities were available for 31 isolates, only 10 (32%) of which were susceptible. Of the CP, all 15 were susceptible to colistin, but only 2 (14%) were susceptible to tobramycin. Of the Non-CP, 16 (89%) were susceptible to colistin, and 8 (47%) were susceptible to tobramycin. Most CRABs had a tigecycline minimum inhibitory concentration (MIC) of ≤2 μg/mL, with a higher proportion of Non-CP with lower MIC values than CP.

Conclusion

CRAB shows resistance to all carbapenems, and most non-carbapenem antibiotics except colistin and in rare circumstances tobramycin. Most CRAB isolates had tigecycline MICs of ≤2 μg/mL. The statewide antibiogram illustrates the lack of approved antibiotics for the treatment of CRAB, underscoring the importance of further antibiotic development for CRAB treatment.

Disclosures

All authors: No reported disclosures.
556. Phylogenomic Epidemiology of Methicillin-Resistant Staphylococcus aureus (MRSA) Chilean-Cordobes Clone in Latin America
Authors: Martínez Jose R W , Diaz Lorena , Rojas Marcelo , Rios Rafael , Hanson Blake , Rivas Lina M , Spencer Maria , Moustafa Ahmed M , Araos Bralic Rafael , Peters Anne , Reyes Jinnethe , Carvajal Lina P , Luna Carlos , Salles Mauro , Alvarez Carlos , Labarca Jaime , Seas Carlos , Seas Carlos , Guzmán Manuel , Planet Paul J , Planet Paul J , Arias Cesar A , Munita Jose
Published: October 2019

Background

The MRSA Chilean-Cordobes (ChC) clone belongs to the clonal complex 5 (CC5) and typically carries SCCmec I. The ChC clone predominated widely throughout several countries of Latin America (LA), but during the mid-2000s a CA-MRSA CC8 LA variant (USA300-LV) quickly replaced the ChC in Colombia and Ecuador. Most notably, this replacement was not observed in Peru or Chile. Here, we aimed to understand the phylogenomic relatedness of the CC5 ChC clone obtained from different countries of LA.

Methods

We sequenced and analyzed the genomes of 115 MRSA isolates obtained between 2011–2014 from bloodstream infections in 6 LA countries (Argentina, Brazil, Colombia, Chile, Peru, and Venezuela). All isolates were confirmed as ChC clone by pulsed-field gel electrophoresis (PFGE). We used core genome-based phylogenomic reconstructions and molecular clock analysis to infer the relationships and time of divergence between clades.

Results

Whole-genome-based multilocus sequence typing determined that 110/115 isolates belonged to ST5 and carried SCCmec I. The phylogenomic reconstruction showed ChC isolates clustered into 4 major clades distinctly segregated by country of origin (Figure 1). Interestingly, isolates recovered from Chile divided into 2 different clades that segregate according to the city of origin (Santiago [SCL] or Concepción [CON]), suggesting these clades evolved independently. Molecular clock analyses suggested all clades share a common ancestor with the divergence of the Chilean clades occurring earlier (Figure 2). Of note, analysis of heavy metal genes suggested the divergence between Chilean isolates was characterized by the loss of a mercury resistance gene cluster, which is present in an 88% of CON isolates, but only in 28% of SCL (Figure 2).

Conclusion

MRSA isolates belonging to the ChC clone from 6 LA countries clustered in 4 clades according to the geographical region of isolation. This segregation suggests divergent adaptations that may respond to different selective pressures. Heavy metal resistance could play a role in the ability of the MRSA ChC to disseminate in specific geographical locations.

Disclosures

All authors: No reported disclosures.
559. Two Different Beasts: Comparing Epidemiology of Healthcare-Associated vs. Community-Acquired Methicillin-Resistant Staphylococcus aureus Bacteremia
Authors: McLaughlin Luke , Smith Stephanie
Published: October 2019

Background

Methicillin-resistant staphylococcus aureus (MRSA) bloodstream infection (BSI) is associated with significant morbidity and mortality. Healthcare-associated (HCA) MRSA infection (occurring >48 hours after hospitalization or in those with prior healthcare exposure) has traditionally been associated with severe invasive disease, while community-associated (CA) MRSA infection (occurring within 48 hours of hospitalization and without prior healthcare exposure) has been observed in otherwise healthy individuals. We characterized the epidemiology, resistance patterns, and clinical outcomes associated with MRSA BSI over a 5 year period comparing patients with community-onset bacteremia to those with hospital onset bacteremia.

Methods

We performed a retrospective chart review of 151 MRSA bloodstream infections from 2013–2018 at the University of Alberta Hospital (Edmonton, Canada). We assessed each BSI by: classification (CA vs. HCA), presence of MRSA risk factors, source of infection, MRSA resistance, rate of ICU admission, and 30-day mortality.

Results

The median age of all patients with MRSA BSI was 53 years (range 23–94). MRSA BSI occurred more commonly in males for both CA and HCA infection (53% and 62%). HCA-MRSA infections had a higher rate of previous MRSA colonization (64.8%) compared with CA-MRSA patients (41.7%). Injection drug use was higher in CA-MRSA infections (47% vs. 11%). The most common source of CA-BSI was bone/joint (30%) while line-associated infections were the most common in HCA-BSI. Clindamycin resistance was common (46–53% susceptible) while resistance to tetracyclines (91–97% susceptible) and trimethoprim/sulfamethoxazole (98–100% susceptible) was uncommon. HCA-MRSA BSI was associated with a higher rate of ICU admission (44% vs. 33%) and 30-day mortality (18.7% vs. 11.7%).

Conclusion

Invasive MRSA infection continues to be associated with significant morbidity and mortality. We found that healthcare-associated MRSA BSI was associated with a high rate of prior MRSA colonization as well as a higher rate of ICU admission and 30-day mortality. There are significant differences in the demographics of patients with CA BSI compared with HCA BSI. Interventions to prevent these infections need to be targeted to the geographic location of acquisition.

Disclosures

All authors: No reported disclosures.
583. Improving Catheter Scrub Technique and Compliance in a Level IV Neonatal ICU
Authors: Ellsworth Misti G , Milligan Sarah , Yager Lauren , Kubanda Ann , Webber Krysten , Khan Amir M
Published: October 2019

Background

Central line-associated bloodstream infections (CLABSIs) are challenging to prevent in the neonatal population due to the long-term necessity of central access for nutrition and medication. Neonates are a population at high risk for CLABSIs, and infections in this group are associated with prolonged hospitalization, greater healthcare costs, and increased mortality. Current bundles for CLABSI prevention include a friction scrub of the catheter hub prior to each use. Real-time audits of correct technique can be challenging. In July of 2018, our team developed a new strategy for auditing scrub technique in an attempt to reduce CLABSI rates.

Methods

This project took place in a NICU with 118 level 4 beds from July 2018 to February 2019. Our NICU is located in a large metropolitan area and serves as a referral center for complex neonates throughout the region. The intervention period encompassed 25,085 patient-days and 6,206 line days. Real-time friction scrub audits were performed for both dedicated line team staff as well as bedside nurses. In order to determine whether a healthcare worker’s (HCW) scrub technique was successful, a colorless luminescent product was applied to a practice catheter hub that adhered to the hub, but was not visible to the HCW. The HCW would then demonstrate a friction scrub on the practice catheter, and the hub was placed under a black light to show where any residual product may be present. This process was repeated until the staff member was able to remove the product from the hub. Once the staff was successful, monthly real-time audits were continued to reinforce the correct technique.

Results

Between July 2018 and February 2019, compliance with scrub technique and ability to clear product from catheter hubs increased by 50%. The CLABSI rate in the first 9 months after intervention was 0.806 per 1000 line days as compared with 2.170 per 1000 line days in the previous fiscal year.

Conclusion

The number of CLABSI’s during the intervention period was 63% less when compared with the previous fiscal year. This process, in conjunction with our other CLABSI prevention practices, has significantly decreased both our CLABSI rate and overall numbers. This project emphasizes the importance of focusing on the basics of infection prevention practices and continual auditing to prevent practice creep.

Disclosures

All authors: No reported disclosures.
586. Multidrug-Resistant Organisms from Three Pedaitric Inpatient Units in the Domincan Republic
Authors: De Luna David , Mena Lora Alfredo J , Roque Yori , López Franceschini Micheilisse , del Carmen Perez Maria , Cabán Lizamarie
Published: October 2019

Background

Multidrug-resistant organisms (MDRO) are a major global public health threat. Antimicorbial consumption and resistance in low- and middle-income countries (LMICs) are rising. This trend can be consequential for vulnerable populations such as children who have high rates of febrile illnesses. The aim of our study is to asses the burden of MDRO in hospitalized pediatric patients in the Dominican Republic (DR).

Methods

Retrospective review of all positive cultures in patients ages 0–17 at three tertiary referral centers in Santiago, DR. Culture-positive cases from January 2016 to December 2017 were reviewed. Repeat cultures from the same patient were excluded. Phenotypic susceptibility data were collected from automated susceptibility testing systems using WHOnet interface.

Results

A total of 1,584 cultures were reviewed, of which 1,041 (65%) were Gram-negative and 514 (32%) Gram-positive. The most common microorganisms were E. coli (23%)and S. aureus (11%). Sample were obtained from stool (26.9%), blood (23.5%), urine (16.2%), secretions (5.4%), and central line catheters (7.2%). Phenotypic resistance consistent with extended-spectrum β-lactamase (ESBL) and carbapenem-resistant Enterobacteriaceae (CRE) was found in 524 (50.3%) and 179 (17.2%) of Gram-negatives, respectively. MDRO rates by organism are in Figure 2. A total of 72 (21.0%) S aureusisolates were methicillin resistant (MRSA) and 62 (18%) showed suspected inducible resistance to clindamycin (Figure 3).

Conclusion

Data from automated culture systems suggests a high prevalence of ESBL and CRE in this city-wide cohort from three pediatric facilities. Prospective confirmatory studies with manual susceptibility testing may help clarify the true prevalence of MDRO. Further studies are needed to understand the epidemiology and risk factors pediatric patients colonized or infected with MDROs in LMICs and in the DR. Exposure to antimicrobials may be an important risk factor. Understanding antimicrobial use in children and possible exposure to antimicrobials in the environment may help identify antimicrobial stewardship targets and help curb antimicrobial pressure and resistance.

Disclosures

All authors: No reported disclosures.
602. Mechanism of LiaY-Mediated Daptomycin Resistance in Enterococcus faecalis
Authors: Nguyen April , Tran Truc T , Panesso Diana , Khan Ayesha , Mileykovskaya Eugenia , Vitrac Heidi , Arias Cesar A
Published: October 2019

Background

Daptomycin (DAP) is a lipopeptide antibiotic that targets the cell membrane (CM) at the division septum. DAP resistance (DAP-R) in E. faecalis (Efs) has been linked to mutations in genes encoding the LiaFSR stress response system and lipid biosynthetic enzymes, including cardiolipin synthase (Cls). The signature phenotype of DAP-R is redistribution of CM anionic phospholipid (APL) microdomains. Using a genetic approach, we have identified a transmembrane protein (LiaY) as a major mediator of cell membrane APL redistribution associated with DAP-R. Here, we explore the mechanism of LiaY-mediated changes in the CM under the hypothesis that CM remodeling occurs through interactions with Cls.

Methods

Efs encodes two cls genes (cls1 and cls2). Deletion mutants of both cls genes were generated using the Crispr/cas9 system in the daptomycin-sensitive strain Efs OG117 and Efs OG117∆liaX (a DAP-R derivative of OG117). DAP minimum inhibitory concentration (MIC) was determined using E-test on Mueller–Hinton II agar. Visualization of APL microdomains was performed by staining mid-logarithmic phase cells with 1 µM of 10-N-nonyl-acridine orange (NAO) and fluorescence microscopy. Bacterial two-hybrid system was used to study interactions between LiaY with Cls1 or Cls2.

Results

Single or double deletion of cls1 or cls2 in Efs OG117 did not affect DAP MIC, and no changes in CM architecture were seen by NAO staining. In contrast,deletion of cls1 (alone or in conjunction with a deletion of cls2) in a DAP-R derivative of OG117 OG117∆liaX, resulted in a marked decrease in DAP MIC, and NAO staining of Efs OG117∆liaX∆cls1∆cls2 shows a restoration of septal APL microdomain localization.In the same DAP-R background, deletion of cls2 alone did not have any effect on DAP MIC or APL microdomain distribution. Additionally, bacterial two-hybrid assays showed a positive interaction of LiaY with Cls1 but not with Cls2.

Conclusion

We have identified the biochemical basis for DAP-R associated CM remodeling. In a proposed model, the LiaR-mediated activation of the LiaY triggers specific interactions with Cls1 displacing the protein away from the septum, resulting in local generation of APL microdomains that prevents DAP-mediated damage to the CM.

Disclosures

All authors: No reported disclosures.
606. Identification and Characterization of HMB-2, a Novel Metallo-β-Lactamase in a Pseudomonas aeruginosa Isolate
Authors: Zhu Wenming , McAllister Gillian A , Jose Machado Maria , Campbell Davina , Karlsson Maria , Rasheed James , Kainer Marion A , Muleta Daniel , Walters Maroya S , Grass Julian E , Halpin Alison L , Stanton Richard A
Published: October 2019

Background

Carbapenemases, a global health threat, are a diverse group of β-lactamases active against cephalosporins and carbapenems, which are often last resort treatments for multidrug-resistant gram-negative infections. The most common carbapenemases reported among Pseudomonas aeruginosa are metallo-β-lactamase (MBLs). We describe a novel MBL (designated HMB-2) identified in a P. aeruginosa isolate from a urine specimen collected in 2015 as part of CDC’s Emerging Infections Program.

Methods

We performed antimicrobial susceptibility testing (AST) by broth microdilution, real-time PCR to screen for common carbapenemases (IMP, KPC, NDM, VIM, and OXA-48), and modified carbapenem inactivation method (mCIM) to test for carbapenemase production. The isolate underwent whole-genome sequencing (WGS) using Illumina MiSeq and PacBio RS II (Pacific Biosciences) platforms. Long read sequences were polished using Quiver and corrected by Pilon utilizing Illumina reads. We further characterized a putative novel MBL identified in WGS data by amplifying and cloning the gene into the pCR2.1-TOPO II vector (Invitrogen), which was then sub-cloned into a pET21 expression vector (Sigma–Aldrich). The resulting hmb2+ pET21 plasmid was transformed into a susceptible Escherichia coli for AST, including the imipenem-EDTA method to confirm MBL activity.

Results

The isolate displayed resistance to carbapenems and demonstrated phenotypic carbapenemase activity (mCIM positive), but was negative for carbapenemase genes by PCR. WGS analyses identified a putative MBL gene located on the chromosome. The gene shared 98% DNA and protein sequence identity with an MBL reported in 2016 in a P. aeruginosa isolate from Germany (HMB-1) and thus was named hmb-2. The cloned hmb-2 gene conferred resistance to carbapenems (meropenem and ertapenem) and third-generation cephalosporins (cefotaxime and ceftazidime) in transformed E. coli. The Minimum Inhibitory Concentrationratio for the imipenem-EDTA method was ≥4.

Conclusion

A putative, novel β-lactamase gene, blaHMB-2, was identified and cloned. The imipenem-EDTA results indicated that HMB-2 is an MBL. This discovery underscores the important role WGS plays in identifying new mechanisms of antimicrobial resistance.

Disclosures

All authors: No reported disclosures.
616. Evaluation of In Vitro Susceptibility to Ceftazidime/Avibactam of Clinical Isolates of Carbapenem Nonsusceptible Gram-Negative Bacilli from Colombia
Authors: Appel Tobias M , Mojica Maria F , De La Cadena Elsa , Pallares Christian , Virginia Villegas Maria
Published: October 2019

Background

Ceftazidime/avibactam (CZA) is a combination of a third-generation cephalosporin and a diazabicyclooctane β-lactamase inhibitor, which is active against a broad range of class A, C and D β-lactamases. In Colombia, high rates of multidrug-resistant Enterobacteriaceae (Ent)and P. aeruginosa (Pae) have been reported. Of special concern are KPC enzymes endemic in Ent and found in Pae, which are associated with higher mortality and healthcare costs, as well as limited therapeutic options. Herein, we evaluate the susceptibility of clinical isolates of carbapenem nonsusceptible Ent (CNS-E) and Pae (CNS-P) to CZA with the aim of understanding its role as a therapeutic option for these bacteria.

Methods

Three hundred ninety-nine nonduplicate clinical isolates of carbapenem nonsusceptible Gram-negative bacilli were collected in 13 medical centers from 12 Colombian cities, from January 2016 to October 2017 (137 K. pneumoniae [Kpn], 76 E. coli, 34 Enterobacter spp., 21 S. marcescens [Sma] and 131 Pae). CNS-E was defined as minimum inhibitory concentrations (MIC) ≥1 mg/L for ertapenem and CNS-P was defined as MIC ≥4 mg/L for meropenem. MIC were determined by broth microdilution and interpreted according to current CLSI guidelines. CZA MIC were determined using double dilutions of ceftazidime and a fixed concentration of avibactam of 4 mg/L. Comparator agents were ceftazidime, cefepime, piperacillin/tazobactam, imipenem, meropenem, tigecycline (TGC), and fosfomycin (FOS).

Results

Antimicrobial activity of CZA and comparators is shown in Table 1. CZA susceptibility ranged from 69% in Kpn to 81% in Sma, whereas 49% of CNS-P were susceptible to CZA. In both, CNS-E and CNS-P, CZA was superior to all other tested β-lactam compounds. Notably, in CNS-E CZA susceptibility was comparable to FOS and TGC (except for TGC in Sma).

Conclusion

CZA is the most active β-lactam against CNS-E and CNS-P. CZA nonsusceptibility suggests the presence of other resistance mechanisms, such as class B β-lactamases that are not inhibited by avibactam, and which are more frequently reported in CNS-P. Our results highlight the key role of new agents such as CZA in KPC endemic countries and the need for surveillance studies to determine the nature of resistance mechanisms.

Disclosures

All authors: No reported disclosures.
626. Mobile Genetic Element Dynamics of Co-Circulating Klebsiella pneumoniae Sequence Types Carrying blaKPC in Houston, Texas
Authors: Shropshire William C , Dinh An Q , Miller William R , Ecklund Heather , Wanger Audrey , Tran Truc T , Arias Cesar A , Hanson Blake
Published: October 2019

Background

Carbapenem-resistant Klebsiella pneumoniae (CR-Kpn) are a significant cause of hospital-associated infections. Class A β-lactamases, e.g., Klebsiella pneumoniae carbapenemases (KPCs), are major contributors to carbapenem resistance. Sequence type 258 (ST258) is the most common genetic lineage of CR-Kpn associated with blaKPC carriage. Recently, a newly emergent lineage ST307 has been identified within the Houston metropolitan region. The transmission of blaKPC and other antimicrobial resistance (AMR) genes is driven largely by exchange of mobile genetic elements (MGEs). We sought to describe the dynamics of horizontal gene transfer (HGT) in particular between co-circulating strains of ST307 and ST258.

Methods

Long-read sequencing technologies allow us to resolve plasmid sequences and their associated AMR genes as well as characterize a comprehensive range of MGEs enabling transmission of these clinically important resistance mechanisms. CR-Kpn isolates were collected as part of a study to describe CRE burden within a Houston metropolitan hospital system. The Oxford Nanopore Technology (ONT) GridION X5 was used for long-read sequencing with Illumina short-read data used to refine and generate high-quality, consensus assemblies. A custom bioinformatic pipeline was used to resolve plasmid structures and identify the genomic context of plasmids carrying blaKPC variants.

Results

95 Kpn isolates were collected from May to December 2017. Phylogenetic and in silico MLST analysis revealed 38/95 (40%) and 35/95 (37%) were ST258 and ST307, respectively. 86% of Kpn isolates carried one or more IncF-type conjugative plasmids, which were the prime vectors for blaKPC intercellular transmission. Interestingly, we found similar AMR-harboring plasmids within ST258 and ST307 composed of mosaic, modular IS26 and Tn3-like transposase mediated elements that carried multiple AMR determinants including blaKPC variants (Figure 1).

Conclusion

We were able to characterize mechanisms by which ST307 and ST258 lineages may transfer AMR determinants. There are clinically relevant implications to these HGT events that occur between these lineages as they may provide insights into how resistance differentially develops.

Disclosures

All authors: No reported disclosures.
632. Genetic Diversity of Carbapenem-Resistant Klebsiella pneumoniae Causing Late-Onset Neonatal Sepsis in Intensive Care Unit of Caro University Hospital, Cairo, Egypt
Authors: Ghaith Doaa , Mufeed Halaa , Elanwary Sherif , Zafer Mai , Alagamy Mohamed , Bohol Marie , Elsaban Salwa , Qahtani Ahmed , Al-Ahdal Mohammed
Published: October 2019

Background

Neonatal sepsis poses a great challenge for clinicians and infection control practitioners. Carbapenem-resistant Klebsiella pneumoniae (CRKP) is rapidly increasing and poses a major threat to neonates. Our research aim was to examine the phenotypes, genotypes, and genetic relatedness of CRKP in late-onset neonatal sepsis in the neonatal intensive care unit (NICU) at Cairo University Hospital.

Methods

Our study included 88 neonates diagnosed with sepsis; 58 with late-onset sepsis (LOS) and 30 with early-onset sepsis (EOS) admitted to the NICU between November 2015 and April 2016. Laboratory investigations included (vomplete blood count, C-reactive protein, serum interleukin-6 level by ELISA technique and blood culture). bacterial identification and antibiotic susceptibility testing were done by automated VITEK 2 compact system (BioMérieux, France). Detection of carbapenemases (OXA-48, NDM, IMP, KPC, and VIM) by multiplex PCR and pulsed-field gel electrophoresis (PFGE).

Results

K. pneumoniae was the most common encountered pathogen in the LOS group (37.9%) with a mean sepsis score of 6.39 when compared with the 33 EOS group (P < 0.005). The interleukin ratio, C-reactive protein, and interleukin-6 levels were significantly high in the K. group (P ˂ 0.001). The most prevalent 35 carbapenemase gene in the NICU, OXA-48, was identified in 14/23 (60.8%) 36 isolates followed by NDM-1 in 12/23 (52.2%) isolates as detected by multiplex 37 PCR. Coexistence of both carbapenemases was found in 52.2% (12/23). By investigating the genetic relatedness of CRKP by pulsed-field gel electrophoresis, 23 isolates of K. pneumoniae revealed various PFGE patterns, demonstrating that 40 the isolates were nonclonal.

Conclusion

In conclusion, carbapenam-resistant Klebsiella pneumoniae remains the most frequent organism detected in neonatal sepsis. Our results revealed that CRKP isolates were not clonal. Extra data are required on the rates of birth asphyxia and microbiology of neonatal infection since reduced records of diseases sets gaps in understanding how to improve existing practices. Infection control actions including antibiotic stewardship programs with continuous surveillance to trace emerging CRKP infections in the early hours as possible particularly in units at risk as NICUs.

Disclosures

All authors: No reported disclosures.
637. Whole-Genome Sequencing (WGS) of Isolates from Resolving (RB) and Persistent (PB) Methicillin-Resistant Staphylococcus aureus Bacteremia
Authors: Sharma-Kuinkel Batu K , Medie Felix , Ruffin Felicia , Wattam Rebecca , Shukla Maulik , Davis James , Yeaman Michael , Fowler Vance G
Published: October 2019

Background

The basis for PB in MRSA is poorly understood. We tested the hypothesis that PB isolates will exhibit distinct genetic variation vs. resolving bacteremia (RB).

Methods

MRSA isolates from an existing cohort of prospectively enrolled patients with PB (n = 81) and RB (n = 81) were matched by sex, age, dialysis, diabetes mellitus, and presence of any implantable medical device. WGS was performed via MiSeq 2x150 runs (Illumina®) with a targeted depth of 150-fold at Duke Genome Sequencing Core (DUGSIM). The genome sequence was analyzed, assembled, and annotated in PATRIC.

Results

No genetic signature was associated with PB or RB isolates at the genome-wide significance level. Phylogenetic analysis separated the genomes into two distinct clades [Clade 1 (C1): 77 genomes; predominantly CC5; Clade 2 (C2): 74 genomes; predominantly CC8; Figure 1]. Most isolates in C1 genome carried SCC Mec type II (2A) vs. the SCC Mec type IV (2B) in C2. C1 and C2 had a total of 3602 (407 unique only to C1) and 3563 (368 unique only to C2) protein families, respectively, with 3195 families shared across the two groups. Out of the 407 unique C1 protein families, majority were not shared across all the genomes and only 28 were found in more than 40 of the genomes. A detailed look of 28 protein families showed that majority were found to be in 3 distinct genomic regions (R1—5.6 kb, 7 genes, also contains mecI; R2—18.2 kb; 16 genes; R3—6.3 kb, 6 genes, 2 predicted erythromycin resistance gene). Furthermore, 12 of C1 genomes lack these unique regions. Most of the genomes in C1 (Other than 12 genomes) carry genes responsible for erythromycin and clindamycin resistance. Out of the 368 protein families unique to C2, only 3 are widely shared (2 hypothetical proteins and 1 two-component transcriptional regulator. Patient characteristics were not associated with clade type.

Conclusion

The basis for the PB phenotype in patients with MRSA bacteremia is not due to sequence-based variation in the bacterial genome.

Disclosures

All authors: No reported disclosures.
655. Detection of Antibiotic Resistance Genes in Clinical Samples using T2 Magnetic Resonance
Authors: Snyder Jessica L , Manning Brendan , Shivers Robert , Gamero Daniel , Giese Heidi , Phung Nu , Chang Benjamin , Lapp Heather , Paggi Riccardo , Posteraro Brunella , Sanguinetti Maurizio , De Angelis Giulia , Mencacci Antonella , Lowery Thomas J
Published: October 2019

Background

Antibiotic-resistant bacteria are spread through selective pressure from the use of broad-spectrum empirical therapies, mobile genetic elements that pass resistance genes between species, and the inability to rapidly and appropriately respond to their presence. Resistance gene identification is often performed with post culture molecular diagnostic tests. The T2Resistance Panel, which detects methicillin resistance genes mecA/C; vancomycin resistance genes vanA/B; carbapenemases blaKPC, blaOXA-48,blaNDM, blaVIM, and blaIMP; AmpC β-lactamases blaCMY and blaDHA; and extended-spectrum β-lactamases blaCTX-M directly from patient blood samples, is based on T2 magnetic resonance (T2MR), an FDA-cleared technology with demonstrated high sensitivity and specificity for culture-independent bacterial and fungal species identification. Here we report the clinical performance of T2MR detection of resistance genes directly from patient blood samples.

Methods

Patients with a clinical diagnosis of sepsis and an order for blood culture (BC) were enrolled in the study at two sites. BCs were managed using standard procedures and MALDI-TOF for species identification. Resistance testing with the T2MR assay was performed on a direct patient draw and compared with diagnostic test results from concurrent BC specimen and BC specimen taken at other points in time. The potential impact on therapy was evaluated through patient chart review.

Results

T2MR detected the same resistance genes as detected by post culture diagnostics in 100% of samples from concurrent blood draws. Discordant results occurred when T2MR was taken ≥48 hours after BC for patients on antimicrobial therapy. The average time to positive result was 5.9 hours with T2MR vs. 30.6 hours with post-culture molecular testing.

Conclusion

The T2Resistance Panel detected antibiotic resistance genes in clinical samples and displayed agreement with post culture genetic testing. T2MR results were achieved faster than culture-dependent diagnostic testing results and may allow for an earlier change from empiric to directed therapy. The use of culture-independent diagnostics like T2MR could enable a quicker response to antibiotic-resistant organisms for individual patients and developing outbreaks.

Disclosures

All authors: No reported disclosures.
669. Twelve-Month Durability of Microbiota-Based Therapy RBX2660 for Prevention of Recurrent Clostridium difficile Infection
Authors: Jones Courtney , Mische Sarah , Blount Ken , Shannon Bill
Published: October 2019

Background

Recurrent Clostridium difficile infections (rCDI) are a public health threat with insufficient treatment options at present. Two Phase 2 clinical studies have reported the efficacy of RBX2660, a standardized, stabilized microbiota-based drug, in preventing rCDI. For one of these trials, we report herein the durability of clinical response (lack of CDI recurrence) and microbiome restoration to 12 months after RBX2660 treatment.

Methods

Data were drawn from an interim analysis of a multicenter, open-label Phase 2 study in which participants with multi-recurrent rCDI received up to 2 doses of RBX2660 delivered via enema 7 days apart; this analysis includes data to 12 months after treatment, with follow-up ongoing. Efficacy was defined as the absence of CDI recurrence to 56 days after the last dose; and durability is defined as a continued lack of reported recurrence. Participant stool samples collected prior to and at 1, 7, 30, 60 days and 6 and 12 months after treatment were sequenced using a shallow shotgun method, with only treatment responders reported herein. Operational taxonomic unit (OTU) data were used to calculate relative abundance at the class level and Microbiome Health Indices.

Results

This study included 149 RBX2660-treated participants and 110 historical control patients, in the United States and Canada. As previously reported, the efficacy of RBX2660 in preventing rCDI (79.9%; 119/149) was higher than CDI-free rates in the historical control group (51.8%, 57/110; P < 0.001). Of 109 participants who had a 6-month follow-up, 97.2% (106/109) remained CDI-free, and no new CDI recurrences were reported at 12 months. Among treatment responders, the microbiome composition was restored after treatment to predominance by Bacteroidia- and Clostridia-class bacteria, and these compositions remained stable to 12 months after treatment among participants who provided samples.

Conclusion

RBX2660, a microbiota-based drug, was efficacious for preventing rCDI, with clinical and microbiome restoration durability to at least 12 months after treatment. The follow-up of efficacy, safety, and microbiome restoration are ongoing.

Disclosures

All authors: No reported disclosures.
670. VRE Clearance in Patients with Recurrent Clostridium difficile Infection Following Treatment with Microbiota-Based Drug RBX2660
Authors: Hau Heidi , Mische Sarah , Klein Sarah , Blount Ken
Published: October 2019

Background

Vancomycin-resistant Enterococcus (VRE) infection is frequently associated with immunocompromised and critically ill patients. VRE carriers are at increased risk for infection due to VRE colonization and they pose a risk as a transmission source. VRE infection and Clostridium difficile infection (CDI) share common risk factors, including disruption of the intestinal microbiome. Thus, therapeutic approaches that decolonize VRE would be valuable. Herein, we report on stool VRE clearance in a cohort analysis from a Phase 2 open-label study of RBX2660, standardized microbiota-based drug, for recurrent CDI.

Methods

This prospective, multicenter, open-label Phase 2 study enrolled subjects with recurrent CDI. Participants received up to 2 doses of RBX2660 delivered via enema with doses 7 days apart. Patients were requested to voluntarily submit stool samples at baseline and at 7, 30 and 60 days, 6, 12, and 24 months after the last administration of RBX2660. Stool samples were tested for VRE using bile esculin azide agar with 6 µg/mL vancomycin and gram staining. Vancomycin resistance was confirmed via blood agar and etest.

Results

Stool samples were available for 143 patients. Twenty-one patients were VRE-positive at the first test (baseline or 7 day). Of the 19 VRE-positive patients that provided additional samples at later timepoints, 18 (94.7%) converted to negative as of the last available follow-up (30 or 60 days and 6, 12, or 24 months). The remaining patient remained positive at all follow-ups.

Conclusion

This cohort analysis of VRE-positive patients within an rCDI population provides additional support that microbiota-based formulations, such as RBX2660, may have additional benefit beyond reducing the recurrence of CDI. Additional study is needed to confirm the role of microbiome restoration on VRE clearance.

Disclosures

All authors: No reported disclosures
671. Impact of Dose-Administration Strategies of the Antistaphylococcal Lysin Exebacase, (CF-301), in Addition to Daptomycin (DAP) in an Experimental Infective Endocarditis (IE) Model due to Methicillin-Resistant Staphylococcus aureus (MRSA)
Authors: Xiong Yan , Abdelhady Wessam , Li Liang , Schuch Raymond , Cassino Cara , Lehoux Dario , Bayer Arnold
Published: October 2019

Background

MRSA infections, especially involving the endovascular system (e.g., IE), are associated with unacceptably high morbidity and mortality rates. The use of bacteriophage-derived lysin, which acts as direct lytic agents, represents a novel adjunctive approach against virulent Gram-positive bacteria, such as MRSA. The current study examined the efficacy of DAP alone or DAP plus CF-301administered on a single day using various dosing regimens, in a rabbit model of MRSA IE.

Methods

Aortic valve IE due to MRSA strain MW2 was induced by the IV administration of ~1 × 105–2 × 105 cfu in aortic-catheterized rabbits. At 24-hour post-infection, animals were randomized into one of the 13 groups: (1) vehicle controls given once daily (QD); 2–13) DAP alone (at 4 mg/kg iv QD × 4d; this dose yields significant but modest clearance of MRSA in experimental IE); DAP + CF-301 (given as an IV dose on the first day of DAP treatment only by 5–10 min slow bolus at (mg/kg): 0.70 QD, 0.35 Q12h, 0.23 Q8h, 0.35 QD, 0.175 Q12h, 0.117 Q8h, 0.09 QD, 0.045 Q12h, 0.03 Q8h, 0.06 QD, 0.03 Q12h or 0.03 QD. At 24 hours after the last DAP dose, three target organs were quantitatively cultured (cardiac vegetations; kidneys and spleen). Data for each organ were calculated as mean log10 cfu/g of tissue (±SD).

Results

Treatment with DAP alone caused ~2–3 log10 cfu/g reduction in MRSA densities in all three target tissues vs. vehicle controls. All CF-301 doses given in addition to DAP, even at the lowest CF-301 dose (0.03 mg/kg), significantly reduced MRSA densities further in all target tissues vs. DAP alone (~3 log10 cfu/g) and vehicle control groups (~6 log10 cfu/g). In general, DAP plus CF-301 given as a single dose trended toward better microbiologic efficacy than CF-301 given at Q12h or Q8h, although this difference was not statistically significant.

Conclusion

These results demonstrate that CF-301, given at multiple dose strategies and at different dose regimens, in addition to sublethal DAP, had significant efficacy in further decreasing MRSA densities in relevant target tissues in the IE model (vs. DAP alone and untreated controls). DAP plus a single dose of CF-301 trended to better efficacy than when it was administered in fractionated dose-strategies.

Disclosures

All authors: No reported disclosures.
682. In Vivo Pharmacodynamics of VNRX-7145 in the Neutropenic Murine Thigh Infection Model When Administered in Combination with Humanized Exposures of Twice Daily Ceftibuten (CTB) Against Serine β-Lactamase-Producing Enterobacteriaceae (SBL-EB)
Authors: Avery Lindsay M , Abdelraouf Kamilia , Nicolau David P
Published: October 2019

Background

There is a pressing need for development of oral antibiotics with activity against SBL-EB, particularly carbapenemase-producers, for use in the community or as step-down therapy for complicated urinary tract infection. VNRX-7145 is a novel boronic acid-based SBL inhibitor with no intrinsic activity that was designed as an orally bioavailable prodrug. The active moiety (VNRX-5236) is known to restore in vitro susceptibility to (CTB), an oral cephalosporin, among CTB-resistant SBL-EB.

Methods

CTB-resistant SBL-EB (N = 21) with CTB MICs ≥32 µg/mL and CTB/VNRX-5236 MIC range 0.12–2 µg/mL (VNRX-5236 fixed at 4 µg/mL) were evaluated. Carbapenemases were produced by 9 strains (4 OXA, 5 KPC). Bacterial suspensions (~107 CFU/mL) were used to inoculate the thighs of neutropenic mice. A human-simulated regimen of ceftibuten (CTB HSR) equivalent to a 400 mg q12h dosage was developed in infected mice. In dose ranging studies, groups of 3 animals each received the CTB HSR as monotherapy or combined with escalating VNRX-5236 exposures (CTB:VNRX-5236 dose ratios ranging from 10:1 to 1:4). Efficacy was assessed as the change in log10 CFU/thigh at 24 hours from 0 hour burden. With previous in vivo dose fractionation studies indicating the free area under the VNRX-5236 concentration–time curve to MIC ratio (fAUC0-24/MIC) as the PK/PD driver of efficacy, the Hill equation was used to estimate the magnitude required to achieve a static endpoint.

Results

Compared with 0 hour controls (mean log10 CFU/thigh, 5.7 ± 0.3), the bacterial burden for all isolates increased in saline-dosed controls and CTB HSR groups by 3.1 ± 0.8 and 2.5 ± 0.8 log10 CFU/thigh, respectively. The addition of VNRX-5236 resulted in bacterial stasis in 20/21 strains; the mean reduction in bacterial burden with the 1:1 CTB:VNRX-5236 dose ratio was −0.2 ± 0.7 log10 CFU/thigh. A composite assessment of exposure-responses indicated a fAUC0-24/MIC of 9.0 (R2 = 0.70) was associated with stasis.

Conclusion

Against CTB-resistant SBL-EB, inclusive of OXA-48- and KPC-producing strains, VNRX-5236 potentiated the in vivo activity of the CTB human-simulated exposure. The identified fAUC0-24/MIC target associated with bacterial stasis should be considered when selecting VNRX-7145 doses for clinical studies.

Disclosures

All authors: No reported disclosures.