bluuebunny/crossref_metadata_2025 huggingface dataset:
Enteropathogen Identification by Multiplex PCR in Guatemalan Children with Acute, Non-bloody Diarrhea
Authors: Melgar Mario , Lamb Molly , Calvimontes Diva M , Asturias Edwin J , Contreras-Roldan Ingrid , Dominguez Samuel , Robinson Christine C , Berman Stephen , Gaensbauer James
Published: October 2017

Background

Diarrhea is a leading cause of morbidity and mortality in children in low and middle income countries (LMICs). Assessing diarrhea etiology in LMICs is of great importance in order to better develop both therapeutic and public health strategies, but is hampered by the complexity of potential diarrheal pathogens, and diverse methodology needed for pathogen identification

Methods

Subjects 6 to 35 months old with acute, moderate severity, non-bloody diarrhea were enrolled in a diarrheal treatment trial, conducted at one rural (N = 172) and two urban sites (N = 144) in Guatemala. Diarrheal pathogens were determined in stool by multiplex PCR (FilmArray GI® Biofire) which allows simultaneous identification of 23 bacterial, viral, parasitic pathogens. Descriptive statistics on demographics, pathogen load, and differences in pathogen occurrence by site were performed; differences were assessed with t-test and chi2 test

Results

Nearly all (96.8%) subjects had pathogens identified, and most had multiple potential pathogens identified (mean pathogen count: 2.7 urban and 4.8 rural; P < 0.001 (Figure 1). Notable pathogen differences were observed between rural and urban populations. Bacteria (particularly E.coli pathotypes and Campylobacter) and protozoa (particularly giardia) were more common in the rural population (Figure2). Viral pathogens were either similar or more common (norovirus; P = 0.04) in the urban population; rotavirus was uncommon in both sites (10 rural and 12 urban cases). A similar pattern of pathogen evolution with patient age was noted in both settings, with a decrease in the relative number of viral and increase in parasitic pathogens (Figure 3). Important demographic and socioeconomic differences between rural and urban were noted: rural subjects had poorer nutritional status, underdeveloped water and sanitation facilities and more domestic animal exposure

Conclusion

Acute diarrheal episodes in Guatemalan children were associated with a complex spectrum of pathogens when determined by multiplex PCR, with distinct patterns in rural and urban populations. Future studies to precisely determine diarrheal etiologies in LMICs will need to incorporate controls to sort causative organisms from those colonizing the intestine.

Disclosures

All authors: No reported disclosures.
Appropriateness of a Rapid Multiplex Gastrointestinal Panel in the Investigation of Suspected Infectious Diarrhea After Implementation at an Academic Medical Center
Authors: Beatty Norman , Nix David , August Jessica , Swazo Roberto , Kottey Janame , Mckeown Kyle , Alshibani Mohannad , Petty Wanda , Matthias Kathryn , Al Mohajer Mayar
Published: October 2017

Background

The BioFire FilmArray™ Gastrointestinal (GI) Panel is a 1 hour multiplex real-time PCR test that can detect the presence of 22 GI pathogens (viral, bacterial, and parasitic) known to cause infectious diarrhea. Our tertiary-care academic medical center implemented the GI Panel for all cases of suspected infectious diarrhea replacing the previous conventional testing once utilized to detect GI pathogens. Since its implementation we have not had any criteria for ordering this test to aid healthcare providers.

Methods

The aim of this IRB approved, retrospective investigation was to determine the appropriateness of ordering the GI panel at our academic institution. Cases were randomly selected, stratified by age group and result (specific pathogens or negative result) from May 2015 through April 2016 in the post-implementation period (n = 400 of 1117 total tests). We developed appropriateness criteria for ordering the GI panel which included: passage of at least 3 unformed stools in 24 hours plus one or more enteric symptom (nausea, vomiting, abdominal pain/cramps, tenesmus, fecal urgency, moderate to severe flatulence), and one of the following: grossly bloody diarrhea (dysenteric), persistent diarrhea (14 – 30 days), worsening or relapsing diarrhea, fever ≥ 101 F°, severe diarrhea > 10 bouts in 24hrs, immunosuppression, pregnancy, food handler, infant < 1 year and their care takers, age ≥ 65 years old, concern for disseminated GI infection, with no previous GI panel testing in the past 30 days.

Results

Overall appropriateness of GI panel testing based off our generated criteria was 36% (n = 144/400). This included all tests ordered in the outpatient clinics, emergency department, inpatient medical/surgical wards, and intensive care units.

Conclusion

Currently there is not a well-established standard criteria for ordering the GI panel for investigating suspected infectious diarrhea. After implementation at our academic tertiary-care medical center the GI panel was used inappropriately in most cases without a criteria for ordering in place to aid clinicians. Educating healthcare providers about appropriate testing indications is being performed. Further studies are needed to assess if our generated criteria will lead to decreased costs and unnecessary testing.

Disclosures

All authors: No reported disclosures.
Risk Factors and Clinical Outcomes of Cancer Patients with Clostridium difficile Associated Diarrhea Co-infected with a Second Enteropathogen
Authors: Yalamanchili Harika , Chao Andrew , Guevara Eduardo Yepez , Aitken Samuel L , Bhatti Micah , Okhuysen Pablo C
Published: October 2017

Background

Cancer patients are at an increased risk for C. difficile infection (CDI) which is often identified along with other enteropathogens. The impact of co-infections on outcomes has not been established in this population. We compared the risk factors and clinical characteristics of patients with CDI monoinfection (CDIM) and patients coinfected with bacterial (CDIB) or viral (CDIV) enteropathogens.

Methods

Adult patients presenting with primary or recurrent CDI (n = 88) identified on a two-step GI multiplex assay (Biofire) followed by toxin A/B EIA, were classified into CDIM (n = 66), CDIB (n = 12), and CDIV (n = 10) groups. Demographic and clinical data were collected and risk factors and outcomes compared by Fisher’s exact test, ANOVA, and the Kruskal–Wallis test. CDI severity was determined using Zar’s criteria, presence of bacteremia, and ICU stay.

Results

During the study period, 2,017 diarrheal samples were submitted to the microbiology laboratory. An enteric pathogen was identified in 311 (15%) patients. CDI was identified in 88 cases of which 22 (25%) had a second pathogen. CDIM was found in 66 (21%), CDIB in 12 (4%), and CDIV in 10 (3%) subjects. The most common co-pathogens identified were diarrheagenic E. coli in the CDIB group (9/12, 75%) and norovirus in the CDIV group (8/10, 80%). Groups were similar in terms of demographics, number of recurrences, health care acquisition, co-morbidities, disease severity, serum creatinine at presentation, presence of toxin by EIA, and mortality. Patients with CDIM were more likely to have a recent hospitalization than the CDIB group (44/66 67% vs.. 3/12 25%, P = 0.01). Clinical symptoms at presentation were similar for the three groups except for nausea which was more common in the CDIV group when compared with CDIM (8/10, 80% vs. 25/66, 38%; P = 0.02). The use of proton pump inhibitors was similar in the three groups. There was however, a higher proportion of patients taking GABA-like drugs within 90 days among the CDIB patients (10/12, 83%) than the group with CDIM (26/66, 40%) P = 0.01.

Conclusion

In CDI cancer patients, co-infection with other enteropathogens is common. Patients with CDIB were less likely to have a recent admission to a health care facility. The use of GABA-like drugs was associated with a higher risk of bacterial co-infection.

Disclosures

All authors: No reported disclosures.
Genetic Variation in Shiga Toxin-producing Escherichia coli Recovered from Patients in Michigan and Connecticut
Authors: Selheimer Heather , Mosci Rebekah , Rudrik James , Manning Shannon
Published: October 2017

Background

Shiga toxin-producing Escherichia coli (STEC) is a gram-negative foodborne pathogen that causes approximately 265,000 illnesses in the US annually. STEC O157 and six non-O157 STEC serotypes are most commonly associated with illness, though variation exists in the ability of different STEC types to cause disease. Consequently, we sought to examine genetic variation in virulence genes and clustered regularly interspaced repeat (CRISPR) loci among clinical strains of diverse lineages from different geographic locations.

Methods

Isolates were collected from a sentinel surveillance in 2000–2006 by the Michigan Department of Health and Human Services (n = 44) and Connecticut Department of Public Health (n = 115). Whole genome sequencing was performed and genes for O-antigen (serotype), multilocus sequence typing (MLST) and virulence factors were extracted. CRISPRFinder and Geneious were used for CRISPR loci.

Results

A phylogenetic tree based on MLST found no geographic clustering of the strains. Similarly, no difference was observed for stx1 (MI: 89.6%, CT: 83.5%), stx2 (MI: 6.9%, CT: 7.1%), stx1/stx2 (MI: 3.4%, CT: 9.4%), ehxA (MI: 80.0%, CT: 81.2%) and eae (MI: 86.7%, CT: 94.1%) frequencies across geographical locations. Although the CRISPR loci were similar within related STs, which was independent of serotype, some variation was detected between locations.

Conclusion

These data highlight the circulation of common non-O157 STEC lineages capable of causing disease in different populations. Strains had similar virulence gene profiles, though the diversity of the CRISPR loci varied across strains. The latter could be impacted by varying selective pressures that could affect disease frequencies and symptom severity. Continued surveillance of non-O157 STEC is needed to elucidate the genetic characteristics that are most important for disease severity.

Disclosures

All authors: No reported disclosures.
Microbiology of Infected Walled-off Necrosis Following Severe Acute Pancreatitis
Authors: Chihara Shingo , Sahar Nadav , Kozarek Richard , Gluck Michael
Published: October 2017

Background

Formation of fluid collection occur in about 15–20% following severe acute pancreatitis. These fluid collections could become infected with bacterial and fungal organisms and form infected walled-off necrosis (WON). Management options for WON have evolved over the last decade from invasive surgical intervention to combined percutaneous and endoscopic approach (dual modality drainage (DMD). We describe the culture result of WON obtained with DMD.

Methods

The study was performed at Virginia Mason Medical Center, a tertiary medical center located in Seattle. We used a prospective, institutional review board-approved database which include onset of pancreatitis, size of WON, timing of drainage, duration of drain, culture result, antibiotics given, and patient information (gender, age and BMI). The data from December 2007 to December 2016 were analyzed. SAS was used for analysis.

Results

A total of 182 patients underwent DMD for symptomatic and infected walled off necrosis of which 76 grew organism with culture. Forty-two were monomicrobial while 34 were polymicrobial. For the monomicrobial isolates, coagulase negative staphylococcus was isolated most frequently (6), followed by Staphylococcus aureus (4) and viridans streptococcus (3). WON was significantly more likely to be seen in older patients (P = 0.008) and in obese patients (P = 0.06). The longest diameter of WON nor sex of the patient did not significantly factor into whether the culture grew no organism, one organism, or multiple organisms.

Conclusion

This is the largest data evaluating microbiology of infected walled off necrosis. Organisms isolated are mostly colonizers of skin and gastrointestinal tract. Positive cultures were seen more in obese and elder patients. Clinical correlation is needed when deciding whether to treat these organisms or not.

Disclosures

R. Kozarek, Boston Scientific: Investigator, Research support
Antimicrobial Activity of Ceftolozane–Tazobactam Tested against Contemporary (2012–2016) Enterobacteriaceae and Pseudomonas aeruginosa from ICU vs. non-ICU Isolates Collected in US Medical Centers
Authors: Shortridge Dee , Duncan Leonard R , Pfaller Michael A , Flamm Robert K
Published: October 2017

Background

Ceftolozane-tazobactam (C-T) is a combination of a novel antipseudomonal cephalosporin and a well-described β-lactamase inhibitor. C-T was approved by the United States (US) Food and Drug Administration in 2014 for complicated urinary tract infections, including acute pyelonephritis and complicated intra-abdominal infections. C-T is currently in clinical trials for the treatment of hospital-acquired pneumonia. The Program to Assess Ceftolozane-Tazobactam Susceptibility (PACTS) monitors C-T resistance to gram-negative (GN) isolates worldwide. This study compares the activities of C-T and comparators against GN isolates from ICU patients and non-ICU patients.

Methods

A total of 3,100 GN ICU isolates and 3,271 isolates from non-ICU patients were collected from 30 US hospitals in 2012–2016. Isolates were tested for susceptibility (S) to C-T and comparators by CLSI broth microdilution methodology in a central monitoring laboratory. Other antibiotics tested included amikacin (AMK), cefepime (FEP), ceftazidime (CAZ), colistin (COL), meropenem (MER), and piperacillin-tazobactam (TZP). CLSI (2017) interpretive criteria were used for all except COL with Enterobacteriaceae (ENT), for which EUCAST (2017) criteria were used.

Results

The most common ENT species from ICU and non-ICU patients were similar. The 3 most common ENT for ICU and non-ICU isolates were Klebsiella pneumoniae, 24.1% and 25.8%; Escherichia coli, 19.4% and 18.2%; and Serratia marcescens, 14.7% and 14.3%, respectively. The most common non-enteric species was Pseudomonas aeruginosa (PSA) for ICU and non-ICU (72.7% and 78.2%). ICU ENT isolates generally had a lower %S than non-ICU (Table). ENT showed more variability than PSA for %S between ICU and non-ICU.

Conclusion

For ENT overall, MER and AMK were the most active, followed by C-T. Comparing ICU and non-ICU, MER and C-T were slightly more active vs. non-ICU ENT, while AMK %S was similar for both. For PSA, COL was the most active; C-T and AMK were similar. Activities between ICU and non-ICU isolates were similar for C-T and COL while AMK was more active vs. ICU isolates, and MER was more active vs. non-ICU. C-T showed potent activity against ICU and non-ICU isolates for ENT and PSA.

Disclosures

D. Shortridge, Merck: Research Contractor, Research grant; L. R. Duncan, Merck: Research Contractor, Research grant; M. A. Pfaller, Merck: Research Contractor, Research grant; R. K. Flamm, Merck: Research Contractor, Research grant
In Vitro Activity of Newer Antimicrobials and Relevant Comparators Vs. 349 Stenotrophomonas maltophilia Clinical Isolates Obtained from Patients in Canadian Hospitals (CANWARD, 2011–2016)
Authors: Walkty Andrew , Baxter Melanie , Adam Heather J , Lagace-Wiens Philippe , Karlowsky James , Zhanel George
Published: October 2017

Background

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

Methods

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

Results

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

Conclusion

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

Disclosures

G. Zhanel, Achaogen: Research relationship, Research support Astellas: Research relationship, Research support Merck Canada: Research relationship, Research support Merck USA: Research relationship, Research support Paratek Pharma: Research relationship, Research support Pharmascience: Research relationship, Research support Sunovion: Research relationship, Research support Tetraphase: Research relationship, Research support The Medicines Co.: Research relationship, Research support Zoetis: Research relationship, Research support
Assessment of the In Vitro Antifungal Activity of SCY-078 Against a Collection of C. parapsilosis Clinical Isolates
Authors: Barat Stephen , Angulo David , Borroto-Esoda Katyna , Ghannoum Mahmoud
Published: October 2017

Background

Global rates of candidemia caused by C. parapsilosis are increasing with differences detected between neonates and adult patients (50% vs. 12%, respectively) and across geographic regions (5% vs. 25% in Iceland and Spain, respectively). SCY-078 is a novel, oral and intravenous, triterpenoid glucan synthase inhibitor under development for the treatment of invasive candidiasis. This study evaluated the in vitro antifungal activity of SCY-078 against a collection of clinical C. parapsilosis isolates.

Methods

Retrospective analysis of data from 7 independent studies evaluating the activity of SCY-078 is presented. Data were available for 206 C. parapsilosis isolates collected between 2008 and 2015 in the US and EU. The collection included 186 wild-type isolates as well as 14 azole-resistant, and 6 echinocandin-resistant isolates. Minimum inhibitory concentrations (MIC) were determined according to the CLSI M27-A3 and EUCAST E.DEF 7.3 guidelines. Comparator compounds varied across studies and included fluconazole, micafungin (MCF), caspofungin (CSP), and anidulafungin (ANI). MIC50 and MIC90 values were defined as the concentrations inhibiting growth of 50% and 90% of isolates, respectively. Echinocandin and azole resistance were determined based on CLSI M27-A4 guidelines.

Results

The MIC50 values obtained for SCY-078 against the wild-type C. parapsilosis isolates across the 7 studies ranged from 0.25 to 1 μg/mL and the MIC90 values ranged from 0.25 -2 µg/mL. Among the echinocandins, MIC90 values ranged from 0.5 to 2 µg/mL (CSP), 1 to 4 µg/mL (MCF) and 2 to 4 µg/mL (ANI). SCY-078 was active against the 14 azole-resistant isolates (MIC ranging from 0.25 to 2 µg/mL). Similar activity was observed across the 6 echinocandin-resistant isolates with MIC values for SCY-078 ranging from 0.25 to 1 µg/mL. Among the 4 most recent studies in the US and EU (2013–2015) C. parapsilosis isolates represented 14 – 20% of the Candidaisolates; rates were similar in the EU and US.

Conclusion

SCY-078 demonstrated potent activity against C. parapsilosis clinical isolates. Notably, SCY-078 was effective against all the echinocandin and azole resistant C. parapsilosis isolates tested.

Disclosures

S. Barat, Scynexis, Inc: Employee, Salary; D. Angulo, Scynexis, Inc.: Employee, Salary; K. Borroto-Esoda, Scynexis Inc.: Consultant, Consulting fee; M. Ghannoum, Scynexis, Inc.: Consultant, Investigator and Scientific Advisor, Consulting fee, Research grant and Research support
In Vitro Activity of Eravacycline and Comparator Antimicrobials Against 143 Strains of Bacteroides Species.
Authors: Citron Diane , Tyrrell Kerin , Goldstein E
Published: October 2017

Background

Eravacycline (ERV is the first fully synthetic fluorocycline with activity against tetracycline (TET)-resistant organisms. In addition, it is 2–8 times more potent than tigecycline (TGC). Like other tetracyclines, it inhibits protein synthesis by binding to the 30S ribosomal subunit exhibiting a broad spectrum of activity. To further explore its activity, we tested 143 clinical isolates of Bacteroides and included TET, TGC and other drugs frequently used to treat serious infections.

Methods

Clinical isolates recovered during the past 3 years from patients in southern California were saved as pure cultures in 20% skim milk at −70°C. Prior to testing, they were transferred at least twice to ensure purity and good growth. Antimicrobials included ERV, TET, TGC, piperacillin-tazobactam (P-T), meropenem (MER), clindamycin (CLI), and metronidazole (MET). The method was agar dilution as described in the CLSI M11-A8 document for testing anaerobes using Brucella agar and incubation in the anaerobic chamber at 36°C for 44h. The MIC was defined as the lowest dilution that completely inhibited growth or resulted in a marked reduction compared with a drug-free growth control.

Results

The MIC90 values (µg/ml) for Bacteroides and Parabacteroides are presented in the table:

Conclusion

This study confirmed the improved activity of ERV over TGC against Bacteroides and suggests that ERV may be an appropriate choice for infections involving these organisms.

Disclosures

E. Goldstein, Tetraphase Pharmaceuticals: Research Contractor, Research grant
Activity of Tedizolid against Gram-Positive Clinical Isolates Causing Nosocomial- and Community-Acquired Infections in United States Hospitals (2014–2016)
Authors: Mendes Rodrigo E , Shortridge Dee , Arends S J Ryan , Sader Helio S , Castanheira Mariana , Flamm Robert K
Published: October 2017

Background

Tedizolid (TZD) was approved for the treatment of acute bacterial skin and skin structure infections and is also under investigation for the treatment of hospital-acquired (HA) bacterial pneumonia. The activity of TZD and comparators were evaluated against gram-positive (GP) pathogens causing community (CA)-acquired and HA infections in the US.

Methods

During the Surveillance of Tedizolid Activity and Resistance (STAR) Program, 10,091 GP isolates were recovered from patients in 31 US hospitals. Isolates were identified by standard biochemical algorithms and MALDI-TOF MS. Susceptibility (S) testing followed CLSI methods and CLSI/EUCAST interpretation. CA and HA infections were defined based on CDC criteria.

Results

TZD (MIC50/90, 0.12/0.12 µg/mL; 100.0%S) showed equivalent MIC50 and MIC90 values against MSSA and MRSA, regardless of infection type or origin of isolate (Table). Linezolid (LZD; MIC50/90, 0.5–1/1 µg/mL; 100.0%S), daptomycin (DAP; MIC50/90, 0.25/0.5 µg/mL; 99.5–100.0%S), vancomycin (VAN; MIC50/90, 0.5–1/1 µg/mL; 100.0%S) and trimethoprim-sulfamethoxazole (MIC50/90, ≤0.5/≤0.5 µg/mL; 93.0–99.5%S) were also active throughout against MSSA and MRSA, while MICs for other agents varied. TZD (MIC50/90, 0.12/0.25 µg/mL; 100.0%S) activities were consistent against E. faecalis causing various infections from different origins, as were LZD (MIC50/90, 1/1 µg/mL; 100.0%S), ampicillin (MIC50/90, 1/1–2 µg/mL; 100.0%S), DAP (MIC50/90, 1/1–2 µg/mL; 100.0%S), and VAN (MIC50/90, 1/2 µg/mL; 94.9–97.0%S), although these agents had MIC50 and MIC90 values 4- to 8-fold higher than TZD. TZD (MIC50/90, 0.12/0.25 µg/mL), LZD (MIC50/90, 1/1–2 µg/mL; 97.6–100.0%S) and DAP (MIC50/90, 1/2–4 µg/mL; 97.4–100.0%S) were active in vitro against E. faecium, regardless of infection type. S. pneumoniae isolates were S to several drugs tested, and ceftaroline showed the lowest MICs (MIC50/90, ≤0.015/0.06 µg/mL; 100.0%S).

Conclusion

TZD had potent in vitro activity against GP isolates causing CA and HA infections in US hospitals, regardless of infection site or bacterial species. The TZD in vitro potency was also generally higher than clinically available comparator agents.

Disclosures

R. E. Mendes, Merck: Research Contractor, Research grant;  D. Shortridge, Merck: Research Contractor, Research grant; S. J. R. Arends, Merck: Research Contractor, Research grant; H. S. Sader, Merck: Research Contractor, Research grant; M. Castanheira, Merck: Research Contractor, Research grant;  R. K. Flamm, Merck: Research Contractor, Research grant
Antimicrobial Activity of Ceftolozane–Tazobactam Tested against Contemporary (2012–2016) Enterobacteriaceae and Pseudomonas aeruginosa Isolates by US Census Division
Authors: Shortridge Dee , Duncan Leonard R , Pfaller Michael A , Flamm Robert K
Published: October 2017

Background

Ceftolozane-tazobactam (C-T) is a combination of a novel antipseudomonal cephalosporin and a well-described β-lactamase inhibitor. C-T was approved by the United States (US) Food and Drug Administration in 2014 for complicated urinary tract infections, including acute pyelonephritis and complicated intra-abdominal infections. C-T is currently in clinical trials for the treatment of nosocomial pneumonia. The Program to Assess Ceftolozane-Tazobactam Susceptibility (PACTS) monitors C-T resistance to gram-negative (GN) isolates worldwide. In this study, the activities of C-T and comparators vs. GN isolates from each of the 9 US Census divisions were compared.

Methods

A total of 18,856 Enterobacteriaceae (ENT) and 4,735 Pseudomonas aeruginosa (PSA) isolates were collected from 32 US hospitals in 2012–2016. Isolates were tested for susceptibility (S) to C-T and comparators by CLSI broth microdilution methodology in a central monitoring laboratory. Other antibiotics tested included amikacin (AMK), ceftazidime (CAZ), colistin (COL), meropenem (MER), and piperacillin-tazobactam (TZP). The following resistant phenotypes were analyzed for ENT: carbapenem resistant (CRE); extended-spectrum β-lactamase phenotype screen-positive (ESBL); and ESBL, nonCRE. or PSA, MER-nonsusceptible (NS), TZP-NS, and CAZ-NS isolates were analyzed. CLSI (2017) interpretive criteria were used.

Results

For all ENT, 94.2% were S to C-T, 91.5% were S to TZP, 98.0% were S to MER, and 98.8% were S to AMK; 1,697 (9.0%) were ESBL, nonCRE and 356 (1.9%) were CRE. For all PSA isolates, 97.4% were S to C-T, 99.3% were S to COL, 96.9% were S to AMK, and 81.2% were S to MER. The % C-T S for each division (DIV) are shown in the table. The % C-T S for ENT ranged from 98.1% (DIV 4) to 87.4% (DIV 2) and % C-T S for ESBL, nonCRE ranged from 93.8% in DIV 4 to 79.8% in DIV 7. For PSA, the % C-T S ranged from 99.6% in DIV 4 to 94.9% in DIV 9. Activity of C-T against PSA NS to MER, CAZ or TZP varied by division and was >80% for all except DIV 9.

Conclusion

Against PSA, only COL was more active than C-T. C-T demonstrated potent activity against PSA NS to other β-lactams. For ENT, overall activity was good. For both PSA and ENT, C-T varied by DIV.

Disclosures

D. Shortridge, Merck: Research Contractor, Research grant; L. R. Duncan, Merck: Research Contractor, Research grant; M. A. Pfaller, Merck: Research Contractor, Research grant; R. K. Flamm, Merck: Research Contractor, Research grant
Effects of Iclaprim and Trimethoprim on Exotoxin Production by Methicillin-resistant Staphylococcus aureus
Authors: Bryant Amy , Katahira Eva , Huang David , Stevens Dennis
Published: October 2017

Background

Methicillin-resistant Staphylococcus aureus (MRSA) causes serious, often life-threatening, infections. Exotoxins such as alpha-hemolysin (AH), Panton Valentine leukocidin (PVL), and Toxic shock syndrome toxin 1 (TSST-1) mediate pathogenesis and inhibition of toxin production is an important consideration in choosing appropriate treatments. Vancomycin is recommended for severe MRSA infections; however, increasing vancomycin resistance, poor clinical outcomes and nephrotoxicity are serious concerns. Thus newer agents are needed, including those that block bacterial toxin production. In the current study, we compared the effects of sub-inhibitory doses (sub-MIC) of two folic acid inhibitor antibiotics (iclaprim, trimethoprim) with cell wall-active agents (nafcillin, vancomycin) on transcription and translation of AH, PVL and TSST-1 in two clinical MRSA isolates.

Methods

Community-acquired MRSA strains 1560 (a USA400 strain; AH+, TSST-1+, PVL-) and 04014 (CDC strain 368–04; AH+, TSST-1-, PVL+) were studied. MICs were determined by standard microbroth dilution. Gene expression was studied by northern blotting and/or qRT-PCR; toxins were quantitated by ELISA (PVL and TSST-1) and rabbit erythrocyte lysate assay (AH).

Results

In agreement with our previous findings, nafcillin increased production of AH, TSST-1, and PVL compared with untreated control cultures. In both MRSA strains, iclaprim and trimethoprim delayed the onset of mRNA production and shifted its peak production to later time points. Both iclaprim and trimethoprim suppressed AH production in both strains of MRSA and delayed, but did not reduce, maximal TSST-1 production in MRSA1560. Trimethoprim significantly increased maximal PVL production over both untreated and iclaprim-treated cultures.

Conclusion

The folic acid antagonist antibiotics, iclaprim and trimethoprim, altered both mRNA synthesis dynamics and protein toxin production in MRSA at concentrations below those that inhibit bacterial growth. These results, plus the fact that iclaprim is 15-fold more active than trimethoprim (MICs = 0.13 and 2.0 ug/ml, respectively), provide additional rationale for the use of iclaprim to treat complicated MRSA infections.

Disclosures

A. Bryant, Motif Biosciences: Grant Investigator, Research grant; D. Huang, Motif Bio: Employee, Salary; D. Stevens, Motif Biosciences: Grant Investigator, Research grant
Activity of Delafloxacin When Tested Against Bacterial Surveillance Isolates Collected in the US and Europe During 2014–2016 as Part of a Global Surveillance Program
Authors: Flamm Robert K , Shortridge Dee , Huband Michael D , McCurdy Sandra , Pfaller Michael A
Published: October 2017

Background

Delafloxacin (DLX) is an investigational anionic fluoroquinolone with an NDA that is under US FDA review to treat acute bacterial skin and skin structure infections and is undergoing Phase 3 studies to treat community-acquired bacterial pneumonia.

Methods

A total of 36,683 Gram-positive (GP) and -negative (GN) bacteria isolated during 2014–2016 were selected from medical centers in the US and Europe. Susceptibility testing (S) was performed by frozen-form broth microdilution methods for DLX and comparators.

Results

DLX was very active against Staphylococcus aureus (SA, n = 9,355; MIC50/90, 0.008/0.5 mg/L) while the levofloxacin (LEV) MIC50/90 was 0.25/>4 mg/L (67.9%S). The MIC50/90 for methicillin-resistant SA (MRSA) was 0.12/1 mg/L. For MRSA, all isolates were S to vancomycin and daptomycin (DAP), linezolid and tigecycline (TGC) S was ≥99.9%. Decreased rates of S were noted for LEV (29.8%), clindamycin (72.9%), and erythromycin (17.3/17.8%; CLSI/EUCAST). Minocycline (MIC50/90, 0.12/0.25 mg/L), ceftaroline (MIC50/90, 0.25/0.5 mg/L), DAP (MIC50/90, 0.5/0.5 mg/L), and DLX (MIC50/90, 0.015/0.5 mg/L) were the most active agents tested against coagulase-negative staphylococci. Against Streptococcus pneumoniae (SPN), the MIC50/90 for DLX (0.015/0.03 mg/L) and TGC (0.03/0.06 mg/L) were the lowest among the agents tested. The DLX MIC50/90 values did not vary among the penicillin-S, -intermediate, and -R subgroups of SPN. The MIC50/90 values for DLX against S. pyogenes and S. agalactiae were 0.015/0.03 mg/L. DLX was highly active against Haemophilus influenzae. The DLX MIC50/90 (≤0.001/0.004 mg/L) was the same for β-lactamase positive and negative H. influenzae. Against Enterobacteriaceae, 76.0% of DLX MIC values were ≤1 mg/L. Susceptibility to LEV was 80.8%, and S to ceftriaxone, ceftazidime (CAZ), and cefepime ranged from 78.5–86.3%. A total of 72.6% of Pseudomonas aeruginosa isolates exhibited DLX MIC values ≤1 mg/L, while LEV S was 73.2% and CAZ was 81.6%. The MIC50/90 for both DLX and LEV were 0.5/>4 mg/L, respectively.

Conclusion

DLX was active against a broad range of GP and GN bacteria, including MRSA and multidrug-resistant SPN. DLX merits further study as therapy in infections in which these organisms may occur.

Disclosures

R. K. Flamm, Melinta Therapeutics: Research Contractor, Research grant D. Shortridge, Melinta Therapeutics: Research Contractor, Research grant M. D. Huband, Melinta Therapeutics: Research Contractor, Research grant S. McCurdy, Melinta Therapeutics: Employee, Salary M. A. Pfaller, Melinta Therapeutics: Research Contractor, Research grant
AAI101, a Novel β-Lactamase Inhibitor: Microbiological and Enzymatic Profiling
Authors: Papp-Wallace Krisztina M , Bethel Christopher R , Barnes Melissa D , Rutter Joseph D , Taracila Magdalena A , Bajaksouzian Saralee , Jacobs Michael R , Bonomo Robert A
Published: October 2017

Background

AAI101 is a novel β-lactamase inhibitor (BLI), active against ESBLs and other β-lactamases. AAI101 combined with cefepime (FEP) is in Phase 2 clinical trials. The objective of this study was to determine differences between AAI101 and tazobactam in their inhibition of selected β-lactamases of clinical relevance.

Methods

Isogenic E. coli strains expressing single clinically relevant β-lactamases were tested for susceptibility (broth microdilution MIC) to FEP, FEP/AAI101 and piperacillin-tazobactam (P/T). Periplasmic β-lactamase extracts from selected strains then were used to determine IC50s for AAI101 and for tazobactam. β-Lactamases with low IC50s for AAI101 were purified, and steady-state inactivation kinetics determined for AAI101 and for tazobactam.

Results

AAI101 restored activity of FEP against E. coli strains producing defined β-lactamases, and FEP/AAI101 was more potent than P/T (Table).

Conclusion

Addition of AAI101 enhances cefepime activity vs. a selected array of β-lactamases expressed in E. coli in an isogenic Background. The inhibitory kinetics of β-lactamases by AAI101 compared with those of tazobactam indicate different mechanisms of β-lactamase inhibition.

Disclosures

K. M. Papp-Wallace, Entasis: Grant Investigator, Research grant Allecra: Grant Investigator, Research grant Merck: Grant Investigator, Research grant; Roche: Grant Investigator, Research grant Allergan: Grant Investigator, Research grant M. R. Jacobs, Allecra: Grant Investigator, Research grant Roche: Grant Investigator, Research grant Shionogi: Grant Investigator, Research grant; R. A. Bonomo, Entasis: Grant Investigator, Research grant Allecra: Grant Investigator, Research grant Wockhardt: Grant Investigator, Research grant Merck: Grant Investigator, Research grant Roche: Grant Investigator, Research grant GSK: Grant Investigator, Research grant Allergan: Grant Investigator, Research grant Shionogi: Grant Investigator, Research grant
In Vitro Activity of Cefiderocol against Multi-Drug Resistant Carbapenemase-Producing Gram-Negative Pathogens
Authors: Boyd Sandra , Anderson Karen , Albrecht Valerie , Campbell Davina , Karlsson Maria S , Rasheed J Kamile
Published: October 2017

Background

Few options remain for treatment of infections caused by multi-drug resistant (MDR), carbapenemase-producing gram-negative pathogens. Cefiderocol (CFDC; Shionogi & Co. Ltd), is a novel parenteral siderophore cephalosporin that enters the bacterial cell through the iron–siderophore uptake system. Here we report on the in vitro activity of CFDC against a set of well-characterized MDR gram-negative isolates collected by the Centers for Disease Control and Prevention.

Methods

Minimum inhibitory concentrations (MIC) values for CFDC in iron-depleted cation-adjusted Mueller Hinton broth were determined using reference broth microdilution. Study isolates (n = 315) included Enterobacteriaceae (59%), Pseudomonas aeruginosa (19%), Acinetobacter baumannii (17%), Stenotrophomonas maltophilia (4%), and Burkholderia cepacia complex (1%). Of these, 229 (73%) were carbapenemase-producers including Ambler Class A- (37%), Class B- (29%) and Class D- type (29%) enzymes. The remaining isolates included 51 β-lactam-resistant isolates that were non-carbapenemase-producers, and 35 β-lactam-susceptible isolates. Results were interpreted using suggested CFDC breakpoints of Sensitive ≤4 μg/mL and Resistant ≥16 μg/mL.

Results

The majority of the isolates (90.8%) were categorized as CFDC susceptible; the percentage of isolates with a CFDC MIC ≤4 μg/mL among Enterobacteriaceae, P. aeruginosa, and A. baumannii was 87.5%, 100%, and 89%, respectively. Percentage of isolates with a CFDC MIC ≤4 μg/mL that harbored a carbapenemase of the Class A-, Class B-, and Class D-type was 91.8%, 74.8%, 98.0%, respectively. By applying suggested breakpoints, 12 isolates were categorized as intermediate and 17 as resistant. The resistant isolates included 11 NDM-, 2 OXA-23- and 4 KPC-positive organisms.

Conclusion

Cefiderocol showed potent activity against MDR gram-negative pathogens including Class A, B, and D carbapenemase-producing isolates. Of note, all P. aeruginosa, including Class B metallo-β-lactamase producers, were susceptible to CFDC.

Disclosures

All authors: No reported disclosures.
Activity of Ceftolozane/tazobactam (C/T) and Ceftazidime/avibactam (CZA) against Extended-spectrum Β-lactamase (ESBL)-producing Enterobacteriaceae and Multidrug-resistant (MDR) Pseudomonas aeruginosa Isolates
Authors: Hirsch Elizabeth B , Zucchi Paola , Cheung Nicole , Krevolin Kyle , Emery Christopher , Bias Tiffany
Published: October 2017

Background

Antibiotic resistance among Gram-negative bacterial pathogens is a serious public health threat underscored by a diminishing antibiotic development pipeline. This study evaluated the in vitro activity of two new β-lactam/β-lactamase inhibitors, C/T and CZA, against the problematic pathogens ESBL-producing Enterobacteriaceae and MDR P. aeruginosa.

Methods

A convenience sample of 74 ESBL-producing Enterobacteriaceae and 32 MDR P. aeruginosa clinical isolates (1 per patient episode), collected between 2012 and 2017 from 2 academic medical centers in Boston and Philadelphia, was used. MDR was defined as non-susceptibility to ≥1 agent in at least 3 antibiotic classes. Phenotypic confirmation of ESBL isolates was conducted via double disk testing. MICs were determined by broth microdilution in at least duplicate, on separate days, as recommended by CLSI. Klebsiella pneumoniae ATCC 700603 was used as a quality control strain with each experiment. Interpretive criteria for C/T per CLSI were: ≤2 (susceptible) / 4 (intermediate) / ≥8 (resistant) mg/L (Enterobacteriaceae) and ≤4 (susceptible) / 8 (intermediate) / ≥16 (resistant) mg/L (P. aeruginosa). Interpretive criteria for CZA per FDA were: ≤8 (susceptible) / ≥16 mg/L (resistant) (all organisms).

Results

Culture sites for the total isolate collection consisted of urine (n = 62), sputum (n = 30), wounds (n = 9), blood (n = 3), and bone (n = 2). ESBL-producing Enterobacteriaceae included Escherichia coli (n = 60), Klebsiella spp. (n = 12), Enterobacter cloacae (n = 1), and Citrobacter freundii (n = 1). ESBL Enterobacteriaceae isolates were 97.3% and 100% susceptible to C/T and CZA, respectively. The corresponding MIC50/90 values were 0.5/2 mg/L for C/T and 0.25/0.5 mg/L for CZA. MDR P. aeruginosa isolates were 90.6% and 96.9% susceptible to C/T and CZA, respectively. The corresponding MIC50/90 values were 1/4 mg/L for C/T and 2/8 mg/L for CZA.

Conclusion

C/T and CZA, two recently approved β-lactam/β-lactamase inhibitor combinations, maintained reliable activity against a collection of 106 MDR isolates from 2 geographically diverse medical centers.

Disclosures

E. B. Hirsch, Merck: Grant Investigator, Research grant The Medicines Company: Speaker’s Bureau, Speaker honorarium; T. Bias, Merck: Grant Investigator, Research grant The Medicines Company: Speaker’s Bureau, Speaker honorarium
Antimicrobial Activity of Ceftazidime-Avibactam Tested against Multidrug-Resistant Enterobacteriaceae and Pseudomonas aeruginosa Isolates from United States (US) Medical Centers (2013–2016)
Authors: Sader Helio S , Castanheira Mariana , Shortridge Dee , Mendes Rodrigo E , Flamm Robert K
Published: October 2017

Background

The in vitro activity of ceftazidime-avibactam (CAZ-AVI) and many comparator agents were tested against various resistant subsets of organisms selected among 36,380 Enterobacteriaceae and 7,868 P. aeruginosa isolates.

Methods

Isolates were consecutively collected from 94 US hospitals in 2013–2016 and tested for susceptibility by reference broth microdilution methods in a central monitoring laboratory (JMI Laboratories) as part of the International Network for Optimal Resistance Monitoring (INFORM) program. Enterobacteriaceae strains with elevated CAZ-AVI MIC values (≥16 μg/mL) were evaluated for the presence of genes encoding extended-spectrum β-lactamases, KPC, NDM, and transferable AmpC enzymes.

Results

CAZ-AVI inhibited >99.9% of all Enterobacteriaceae at the susceptible (S) breakpoint of ≤8 μg/mL and was active against multidrug-resistant (MDR; n = 2,953; MIC50/90, 0.25/1 μg/mL; 99.2%S, extensively drug-resistant (XDR; n = 448; MIC50/90, 0.5/2 μg/mL; 97.8%S), and carbapenem-resistant isolates (CRE; n = 513; MIC50/90, 0.5/2 μg/mL; 97.5%S). Only 82.2% of MDR Enterobacteriaceae and 64.2% of ceftriaxone-nonsusceptible (NS) Klebsiella pneumoniae (n = 1,063) were meropenem-S. Among Enterobacter cloacae (n = 3,740; 22.2% ceftazidime-NS), 99.8% of isolates, including 99.3% of ceftazidime-NS isolates, were CAZ-AVI-S. Only 22 of 36,380 Enterobacteriaceae (0.06%) isolates were CAZ-AVI-NS, including 8 MBL-producers (0.02%) and 2 KPC-producing strains with porin alteration; the remaining 12 strains showed negative results for all β-lactamases tested. CAZ-AVI showed potent activity against P. aeruginosa (n = 7,868; MIC50/90, 2/4 μg/mL; 97.1% S), including meropenem-NS (n = 1,471; MIC50/90, 4/16 μg/mL; 87.2%S) and MDR (n = 1,562; MIC50/90, 4/16 μg/mL; 86.5%S) isolates, and inhibited 71.8% of isolates NS to meropenem, piperacillin-tazobactam, and ceftazidime (n = 628).

Conclusion

CAZ-AVI demonstrated potent activity against a large US collection (n = 44,248) of contemporary gram-negative bacilli, including organisms resistant to most currently available agents, such as CRE and meropenem-NS P. aeruginosa.

Disclosures

H. S. Sader, Allergan: Research Contractor, Research grant; M. Castanheira, Allergan: Research Contractor, Research grant; D. Shortridge, Allergan: Research Contractor, Research grant; R. E. Mendes, Allergan: Research Contractor, Research grant; R. K. Flamm, Allergan: Research Contractor, Research grant
Antimicrobial Activity of Aztreonam-Avibactam and Comparator Agents Tested against Contemporary (2016) Clinical Enterobacteriaceae Isolates
Authors: Sader Helio S , Mendes Rodrigo E , Shortridge Dee , Flamm Robert K , Castanheira Mariana
Published: October 2017

Background

Avibactam (AVI) is a non-β-lactam β-lactamase (BL) inhibitor that inhibits Ambler class A, C, and some class D enzymes (eg, ESBL, KPC, and AmpC), and aztreonam (ATM) is a monobactam stable to hydrolysis by metallo-β-lactamases (MBL).

Methods

A total of 10,451 Enterobacteriaceae(ENT) consecutively collected from 84 United States (US) medical centers and 250 carbapenem-resistant ENT (CRE) collected from 38 centers in 25 other countries (ex-US) were tested for susceptibility (S) by reference broth microdilution methods in a central monitoring laboratory (JMI Laboratories). CRE strains were screened for the presence of carbapenemase (CBP)-encoding genes using whole genome sequencing analysis.

Results

All ENT isolates from US (MIC50/90, ≤0.03/0.12 μg/mL), except for 1 Escherichia coli strain with an ATM-AVI MIC of 8 μg/mL, and all ex-US CRE isolates (MIC50/90, 0.25/0.5 μg/mL) were inhibited at ATM-AVI MIC of ≤4 µg/mL (CLSI S breakpoint for ATM). Among US isolates, ATM-AVI was also very active against CRE (n = 120; MIC50/90, 0.12/0.5 μg/mL; highest MIC, 4 μg/mL), multidrug-resistant (MDR; n = 876; MIC50/90, 0.06/0.25 μg/mL), extensively drug-resistant (XDR; n = 111; MIC50/90, 0.12/0.5 μg/mL), pan-drug resistant (n = 2; MICs ≤0.03 and 0.12 μg/mL), and ceftazidime-non-S Enterobacter cloacae (MIC50/90, 0.25/1 μg/mL) isolates. Meropenem was very active against US ENT overall (MIC50/90, 0.03/0.06 μg/mL; 98.8%S per CLSI), but showed limited activity against MDR (86.2%S) and XDR (30.6%S) isolates. Amikacin and colistin were active against 74.2% and 81.7% of US CRE, 93.4% and 58.3% US MDR, 65.8% and 57.7% of US XDR, and 58.0% and 79.2% of ex-US CRE isolates, respectively. A total of 106 CBPs were detected in 106 US CRE isolates, including 102 KPC-like, 2 SME-4, 1 NDM-1, and 1 IMP-27. Also, 248 CBPs were identified on 241 ex-US CRE isolates, including 124 KPC-like, 64 OXA-like, 50 NDM-like, 7 VIM-1, 2 IMP-4, and 1 SME-4. All CRE isolates, including all CBP-producing ENT (US and ex-US), were inhibited at ATM-AVI MIC of ≤4 μg/mL.

Conclusion

ATM-AVI demonstrated potent in vitro activity against a large collection of contemporary (2016) ENT isolated from patients in US hospitals and CRE isolates collected worldwide, including NDM, KPC, OXA, VIM, and SME producers.

Disclosures

H. S. Sader, Allergan: Research Contractor, Research grant; R. E. Mendes, Allergan: Research Contractor, Research grant; D. Shortridge, Allergan: Research Contractor, Research grant; R. K. Flamm, Allergan: Research Contractor, Research grant; M. Castanheira, Allergan: Research Contractor, Research grant
Activity of Plazomicin against Enterobacteriaceae Isolates Collected in the United States Including Isolates Carrying Aminoglycoside-Modifying Enzymes Detected by Whole Genome Sequencing
Authors: Castanheira Mariana , Deshpande Lalitagauri M , Hubler Cory M , Mendes Rodrigo E , Serio Alisa W , Krause Kevin M , Flamm Robert K
Published: October 2017

Background

Plazomicin (PLZ) is a next-generation aminoglycoside (AMG) stable against aminoglycoside-modifying enzymes (AME) that completed Phase 3 studies for complicated urinary tract infections and serious infections due to carbapenem-resistant Enterobacteriaceae (ENT). We evaluated the activity of PLZ and AMGs against ENT collected in US hospitals during 2016.

Methods

A total of 2,097 ENT were susceptibility (S) tested by CLSI reference broth microdilution methods. E. coli, Klebsiella spp. Enterobacter spp., and P. mirabilis isolates displaying non-S MICs (CLSI criteria) for gentamicin (GEN), amikacin (AMK), and/or tobramycin (TOB) were submitted to WGS, de novo assembly and screening for AME genes.

Results

Against ENT, PLZ was more active than all 3 clinically available AMGs (Table). PLZ and AMK activities were stable regardless of the infection type; however, differences were observed for GEN and TOB. Bloodstream isolates displayed higher GEN MICs when compared with the other infection sites. TOB activity varied 4-fold, being higher for bloodstream and pneumonia infections and lower for skin/soft tissue and other/unknown specimens. Against 198 isolates carrying 1 or more AME-encoding genes detected among 208 AMG-non-S isolates, the activity of PLZ was 8- to 16-fold greater when compared with the activity of AMK and at least 16-fold higher than the activity of GEN or TOB.

Conclusion

PLZ was active against ENT isolates from US hospitals regardless of infection type. PLZ displayed activity against isolates carrying AME genes that represent 12.0% of selected species. AME-carrying isolates were considerably more resistant to AMK, GEN, and TOB, highlighting the potential value of PLZ to treat infections caused by these organisms.

This project has been funded under BARDA Contract No. HHSO100201000046C.

Disclosures

M. Castanheira, Achaogen: Research Contractor, Research grant; L. M. Deshpande, Achaogen: Research Contractor, Research grant; C. M. Hubler, Achaogen: Research Contractor, Research grant; R. E. Mendes, Achaogen: Research Contractor, Research grant; A. W. Serio, Achaogen: Employee, Salary; K. M. Krause, Achaogen: Employee, Salary; R. K. Flamm, Achaogen: Research Contractor, Research grant