bluuebunny/crossref_metadata_2025 huggingface dataset:
1430. Novel Transmission of Burkholderia pseudomallei from a Freshwater Aquarium to a Human — Maryland, 2019
Authors: Dawson Patrick , Duwell Monique M , Thompson Ruth J , Crum David A , Blythe David , Jacobs Ruth , Elrod Mindy G , Gee Jay E , Liu Lindy , Blaney David D , Weiner Zachary , Bower William A , Hoffmaster Alex R , Salzer Johanna S
Published: January 2021

Background

Nearly all U.S. cases of melioidosis, a potentially fatal disease caused by Burkholderia pseudomallei, are associated with travel to endemic areas. In September 2019, a patient in Maryland with no international travel history developed melioidosis and whole genome sequencing (WGS) of the patient’s clinical isolate showed it clustered most closely with isolates from Southeast Asia. CDC and Maryland Department of Health (MDH) investigated possible sources of B. pseudomallei exposure to identify the source and route of transmission and evaluate risk to others.

Methods

MDH interviewed the patient and household members during October–December 2019. In consultation with CDC, MDH conducted environmental sampling of the patient’s home including drains, faucets, potted and ground soil, imported products, and two freshwater aquariums. Samples were tested for B. pseudomallei at CDC by PCR and culture. B. pseudomallei isolates underwent WGS and were analyzed along with a reference panel of geographically diverse, publicly available genomes.

Results

Three environmental samples, all from aquarium #2, were positive for B. pseudomallei. These isolates matched the patient’s clinical isolate by WGS, suggesting the aquarium was the source of exposure. According to interviews, the patient set up both aquariums in July 2019 and all the fish in aquarium #2 died in August 2019. The patient recalled reaching her bare hands and arms into the aquarium in August 2019, one month prior to illness onset.

Conclusion

This investigation led to the first documentation of transmission of B. pseudomallei from a freshwater aquarium to a human. Many freshwater ornamental fish are imported from Southeast Asia, so this newly recognized transmission route may have significant implications for the freshwater aquatics trade. Further investigations are underway at the retail location that sold the fish and the commercial vendors that supplied the freshwater animals and plants imported from Southeast Asia.

Disclosures

All Authors: No reported disclosures
1431. Occurrence of Sporadic Human Ascariasis in Non-Endemic Regions: The Importance of Zoonotic Transmission from Swine
Authors: Fritsche Thomas R , Meece Jennifer K , Meyer Susan K , Ortega Kelly L , Wolff Nicolette S , Hall Matthew C
Published: January 2021

Background

Ascariasis in developed countries occurs only sporadically, and usually in travelers or in children in rural settings with exposure to Ascaris suum from swine. Reciprocal transmission between humans and swine is possible given A. suum and A. lumbricoides are considered conspecific based on published mtDNA and nuclear ribosomal ITS-1 studies with recognized phenotypic/genotypic differences reflecting host-specific adaptive changes. Here we evaluated 15 cases of human ascariasis detected over 6 a year period in a non-endemic region of the Upper Midwest USA.

Methods

Helminth specimens (n=15) spontaneously passed per rectum were submitted for laboratory identification during 2013-19 and identified morphologically as A. lumbricoides/suum (undifferentiated). All patients attended local clinics and brought specimens in for identification. Clinical records were available for 13 patients.

Results

Ages ranged from 14 months to 41 years with 13 cases (87%) occurring in children < =12 years and 2 (13%) >30 years; 9 patients (60%) were female. Thirteen (87%) of the A. lumbricoides/suum specimens were adults and 2 (13%) were juveniles. Individuals with records available either lived on or had visited a farm (5) or hobby farm (2) where pigs were currently or likely historically present; lived at a rural address (4); used animal manure for gardening (1); or lacked discernable farm connections though was active outdoors (1). International travel history was lacking in all cases. One 2-year old child from a rural address had passed 2 worms 6 months apart. All 13 patients were treated with albendazole per guideline without complication.

Conclusion

Ascariasis attributable to poor sanitation has been largely eradicated from the USA since the early 1980s. Sporadic infections in non-travelers have continued to be recognized and likely represent zoonotic transmission from domesticated swine. While human and pig Ascaris have long been considered distinct species, recently published molecular and cross-transmission experiments point to conspecificity. This case series is a reminder of the zoonotic disease risks posed by swine-origin Ascaris, especially in young children, and reinforces the need for proper herd management and attention to personal hygiene for at-risk individuals.

Disclosures

All Authors: No reported disclosures
1433. Promoting Vaccination of Vaccine Preventable Diseases in Newly Employed Nurses and Doctors Guided by Serological Study
Authors: Lee Seungjae , Son Hyo-Ju , Lee Eunjung , Park Se Yoon , Choo Eun Ju , Kim Tark , Yu Shinae , Park Jung Wan , Kim Tae Hyong
Published: January 2021

Background

Vaccination after serological evaluation of healthcare workers is key component of vaccine preventable diseases (VPDs) preparedness in hospital. The aim of this study is to determine the seroprevalence of VPDs and the vaccination rates among newly employed nurses and doctors.

Methods

A cross-sectional study was conducted at a referral university hospital in the Republic of Korea. All newly employed nurses and doctors without immunity were recommended to have the hepatitis B virus (HBV), varicella zoster virus (VZV), measles, mumps, and rubella (MMR), hepatitis A virus (HAV) and tetanus-diphtheria-pertussis (Tdap) vaccination. HBV, VZV, MMR vaccinations were financially supported and Tdap vaccination was recommended without testing. We investigated the seroprevalence of HAV, HBV, and VZV and vaccination rate of recommended vaccination (HAV, HBV, MMR, VZV, and Tdap) from Jan 1st, 2017 to March 31th, 2020.

Results

A total of 668 (527 female, 141 male) newly employed nurses and doctors were identified. The median age (IQR) is 25 (24-27). Seroprevalence were 59.1% (95% confidence interval [CI] 55.4-62.8) for HAV, 86.1% (95% CI 83.5-88.7) for HBV, and 92.4% (95% CI 90.4-94.4) for VZV. Vaccination rate of recommended vaccination were 24.5% (95% CI 18.5-30.5) for HAV, 23.3% (95% CI 13.6-33.0) for HBV, 48.7% (95% CI 33.0-64.4) for VZV, 30.0% (95% CI 25.5-34.5) for MMR and 33.1% (95% CI 29.0-37.2) for Tdap respectively.

Conclusion

Seroprevalence of HAV was lower than HBV and varicella in newly employed nurses and doctors. Although persistent effort to improve the healthcare worker’s vaccination, the actual rates were low. Further strategy promoting vaccination of newly employed nurses and doctors are needed.

Disclosures

All Authors: No reported disclosures
1434. Rickettsial Infections Complicated With Acute Renal Failure
Authors: Hammami Fatma , Koubaa Makram , Chakroun Amal , Rekik Khaoula , Smaoui Fatma , Elleuch Emna , Marrakchi Chakib , Jemaa Mounir Ben
Published: January 2021

Background

Rickettsiosis, an acute febrile illness, is generally considered as a benign disease. However, severe cases were reported, among which acute renal failure (ARF) represented 13 to 18% of the cases. We aimed to study the clinical and evolutionary features of rickettsiosis complicated with ARF, when compared with all rickettsial infections.

Methods

We conducted a retrospective study including all patients hospitalized for rickettsiosis in the infectious diseases department between 1995 and 2018. The diagnosis was confirmed by serologies (seroconversion).

Results

Overall, we encountered 28 patients (6.4%) with ARF among 440 patients with rickettsiosis. There were 19 males (67.9%). Patients with ARF were significantly older (53±16 vs 38±17 years; p< 0.001). They consulted for eruptive fever (78.6%), febrile cephalalgia (10.7%) or isolated fever (10.7%). Arthralgia and vomiting were noted in 75% and 35.7% of the cases, respectively. There were 4 cases (14.3%) of meningitis and 2 cases (7.1%) of meningoencephalitis. The mean creatinine levels were 158 µmol/L [120-444 µmol/L]. In comparison with all rickettsial infections, eschars were more frequently noted among patients with ARF (46.4% vs 23.8%; p=0.008). They were more frequently diagnosed with septic shock (14.3% vs 0.5%; p< 0.001) and retinitis (10.7% vs 1.5%; p=0.015). Comparison of the disease evolution showed that death was significantly more frequent among cases with ARF (7.1% vs 0.2%; p=0.011). The mean length of hospital stay was significantly longer among patients with ARF (8.7±4.7 vs 5.3±3.5 days; p=0.001). As to gender and the revealing symptoms, no significant difference was noted.

Conclusion

Rickettsial infections complicated with ARF had a poor prognosis, especially among the elderly. Prompt empiric antibiotic therapy might improve the prognosis.

Disclosures

All Authors: No reported disclosures
1437. Biochemical characterization of L1 and L2 β-lactamases from clinical isolates of Stenotrophomonas maltophilia
Authors: Mojica Maria F , Rutter Joseph , Taracila Magdalena A , Papp-Wallce Krisztina M , Spencer James , Vila Alejandro J , Bonomo Robert A
Published: January 2021

Background

Stenotrophomonas maltophilia is a Gram-negative, non-fermenting opportunistic pathogen. Two β-lactamases provide intrinsic resistance to β-lactams: a class B Metallo- β-lactamase L1, and a class A serine β-lactamase (SβL) L2. Recently, we described novel variants of the L1 and L2 in a collection of clinical S. maltophilia isolates collected in the US, and showed through analyses of the amino acid sequences that L1 and L2 grouped into 4 (A-D, B, C, and E) and 2 (A and D) clades, respectively. We aimed to characterize the new L1 and L2 clinical variants biochemically.

Methods

Representative blaL1 and blaL2 genes from each of the identified clades were cloned into pBC-SK and pET24 vectors and transformed into E. coli DH10B and BL21 (DE3) cells, respectively. Minimal inhibitory concentrations (MICs) were determined using CLSI approved methods. Cell-based assays and biochemical characterization performed on purified enzymes, including circular dichroism (CD), thermal stability, and steady-state kinetics assays, were performed.

Results

Susceptibility testing results using DH10-B E. coli strains expressing the L1 and L2 variants are shown in Table 1. Remarkably, while all L1 variants confer the same level of resistance to carbapenems, L2B conferred higher MICs to 3rd gen cephalosporins and aztreonam than L2D. Kinetics assays confirmed differences in the kcat of both enzymes to ceftazidime (32s-1 for L2B vs. 7s-1 for L2D) and avibactam inhibition constant Ki (1.7 μM for L2B vs. 4.5 μM for L2D). Structurally, L2B and L2D present distinctive CD spectra and thermal stabilities (ΔTm 5°C).

Table 1

Conclusion

As opposed to the L2 variants, our results suggest that the L1 variants may not be functionally nor structurally different. Differences between L2B and L2D might have arisen due to the use of cephalosporins and SβL inhibitors. Further experiments are on the way to determine the structural basis of these observations and the implication of these for the design of novel β-lactamase inhibitors.

Disclosures

Krisztina M. Papp-Wallce, PhD, Entasis (Grant/Research Support)Merck (Grant/Research Support)Venatorx (Grant/Research Support) Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)
1438. Dissecting the Multifaceted Nature of Antibiotic Resistance in Clinical Isolates of Neisseria gonorrhoeae by Natural Transformation
Authors: Huang Jianzhong , Ingraham Karen , Chan Pan , Rittenhouse Steve
Published: January 2021

Background

Neisseria gonorrhoeae (NG) causes the sexually transmitted disease gonorrhea. It has developed resistance to every antibiotic introduced for gonorrhea treatment such that NG clinical isolates with multidrug resistance (MDR) are increasingly common. We hypothesize that natural transformation could be used to transfer genetic determinants of antibiotic resistance from drug-resistant NG clinical isolates without pre-knowledge of the genetic determinants to a new background under antibiotic selection to generate isogenic transformants for further characterization.

Methods

Natural transformation, PCR amplification and DNA sequencing, and antibiotic susceptibility testing were used in the studies.

Results

We have validated the hypothesis using genomic DNA from an MDR including ciprofloxacin-resistant NG clinical isolate as a donor and a ciprofloxacin-susceptible NG isolate as a recipient under the selective pressure of ciprofloxacin. This led to a series of transformants that contain single or multiple genetic resistance determinants being generated depending on the resistance levels and transformation frequencies. Antibiotic susceptibility testing and genetic characterization of the transformants allowed us to (i) identify ciprofloxacin resistance determinants including efflux mutation mtrR-79 and target mutations GyrA S91F D95G and ParC D86N, (ii) quantify the contribution of each genetic determinant responsible for the ciprofloxacin resistance and (iii) regenerate the ciprofloxacin resistance phenotype of the donor isolate to detect multiple paths of possible resistance development for ciprofloxacin. Furthermore, we also validated the hypothesis with a novel antibiotic gepotidacin to identify pre-existing genetic determinants contributing to varying susceptibility to this antibiotic. Finally, we envision that, along with whole genome sequencing, natural transformation could be used to identify and quantify novel genetic resistance determinants to current or novel antibiotics in drug-resistant NG clinical isolates.

Conclusion

We demonstrated the utility of natural transformation in dissecting the multifaceted nature of antibiotic resistance in NG clinical isolates.

Disclosures

Jianzhong Huang, PhD, GlaxoSmithKline (Employee, Shareholder) Karen Ingraham, MS, GlaxoSmithKline (Employee, Shareholder) Pan Chan, PhD, GlaxoSmithKline (Employee, Shareholder) Steve Rittenhouse, PhD, GlaxoSmithKline (Employee, Shareholder)
117. Natural Language Processing: An Automated Alternative to Determining Inappropriate Group A Streptococcal Testing
Authors: Lee Brian R , Linafelter Alaina , Burns Alaina , Burris Allison , Jones Heather , Dusin Jarrod , El Feghaly Rana E
Published: January 2021

Background

Acute pharyngitis is one of the most common causes of pediatric health care visits, accounting for approximately 12 million ambulatory care visits each year. Rapid antigen detection tests (RADTs) for Group A Streptococcus (GAS) are one of the most commonly ordered tests in the ambulatory settings. Approximately 40–60% of RADTs are estimated to be inappropriate. Determination of inappropriate RADT frequently requires time-intensive chart reviews. The purpose of this study was to determine if natural language processing (NLP) can provide an accurate and automated alternative for assessing RADT inappropriateness.

Methods

Patients ≥ 3 years of age who received an RADT while evaluated in our EDs/UCCs between April 2018 and September 2018 were identified. A manual chart review was completed on a 10% random sample to determine the presence of sore throat or viral symptoms (i.e., conjunctivitis, rhinorrhea, cough, diarrhea, hoarse voice, and viral exanthema). Inappropriate RADT was defined as either absence of sore throat or reporting 2 or more viral symptoms. An NLP algorithm was developed independently to assign the presence/absence of symptoms and RADT inappropriateness. The NLP sensitivity/specificity was calculated using the manual chart review sample as the gold standard.

Results

Manual chart review was completed on 720 patients, of which 320 (44.4%) were considered to have an inappropriate RADT. When compared to the manual review, the NLP approach showed high sensitivity (se) and specificity (sp) when assigning inappropriateness (88.4% and 90.0%, respectively). Optimal sensitivity/specificity was also observed for select symptoms, including sore throat (se: 92.9%, sp: 92.5%), cough (se: 94.5%, sp: 96.5%), and rhinorrhea (se: 86.1%, sp: 95.3%). The prevalence of clinical symptoms was similar when running NLP on subsequent, independent validation sets. After validating the NLP algorithm, a long term monthly trend report was developed.

Figure Inappropriate GAS RADTs Determined by NLP, June 2018-May 2020

Conclusion

An NLP algorithm can accurately identify inappropriate RADT when compared to a gold standard. Manual chart review requires dozens of hours to complete. In contrast, NLP requires only a couple of minutes and offers the potential to calculate valid metrics that are easily scaled-up to help monitor comprehensive, long-term trends.

Disclosures

Brian R. Lee, MPH, PhD, Merck (Grant/Research Support)
1439. High Rates of Drug Resistance in Escherichia coli from a Pilot Antimicrobial Resistance Surveillance System in Cambodia
Authors: Nov Vandarith , Chau Darapheak , Chhea Chhorvann
Published: January 2021

Background

Antimicrobial resistance (AMR) is a major and growing global public health problem. The Cambodia Ministry of Health established a pilot laboratory-based AMR surveillance system for blood specimens in 2017. The objective of this study is to characterize AMR among pathogenic isolates from blood samples.

Methods

A retrospective analysis was performed using one year of data from a pilot AMR Surveillance system in Cambodia. Four blood culture isolate pathogens were included: Escherichia coli, Klebsiella pneumoniae, Salmonella Typhi /Salmonella Paratyphi A and Staphylococcus aureus. Blood culture isolates that were referred from eleven sentinel sites were analyzed at the National Public Health Laboratory for identification. Antibiotic susceptibility testing (AST) was done using disk diffusion, minimum inhibitory concentration method following Clinical Laboratory Standard Institute (CLSI) guidelines.

Results

Among 214 pathogenic isolates from blood samples, E.coli was the most common (56.1%), followed by Salmonella Typhi/Salmonella Paratyphi A (18.7%), Staphylococcus aureus (13.5%), and Klebsiella pneumoniae (11.7%). Methicillin Resistance Staphylococcus aureus (MRSA) was detected in half of the isolates. E.coli was resistant to ampicillin (94.4%), trimethoprim-sulfamethoxazole (84.5%), and ceftriaxone (79.2%). Salmonella Typhi was resistant to ampicillin (73.3%) and trimethoprim-sulfamethoxazole (60.0%) and Salmonella Paratyphi A were resistant to fluoroquinolones (91.7%). For last resort antibiotics, E.coli was resistant to carbapenem groups (3.2% for imipenem, 4.9% for meropenem, and 5.0% for ertapenem). Klebsiella pneumoniae was not resistant to any groups.

Conclusion

E.coli was found at high rates in blood samples and was resistant to common antibiotics used in Cambodia. These pilot data show the importance of establishing a national AMR surveillance system in Cambodia to monitor AMR trends following GLASS guidelines.

Disclosures

All Authors: No reported disclosures
1442. Acquisition and Transferability Mechanisms of Mercury Resistance Genes in Latin-American Staphylococcus aureus Strains
Authors: Ortega-Recalde Oscar , Echeverri Aura M , Rios Rafael , Carvajal Lina , Hernandez Angie K , Espitia-Acero Catalina , Solano-Gutierrez Sebastian , Shropshire William C , Arias Cesar A , Diaz Lorena , Rincon Sandra , Reyes Jinnethe
Published: January 2021

Background

Latin-American (LA) countries are among the largest mercury (Hg) polluters in the world. Fittingly, a significant high frequency (>50%) of Hg resistance genes (MRG) has been observed in LA MRSA genomes, including USA300-LV clone, which contains the genomic element COMER, encoding for copper and Hg resistance genes adjacent to SCCmecIVc/E. Co-selection of MRG and antibiotic resistance genes may be facilitated by shared transferable genetic elements, nevertheless, analyses of the genetic MRG context in strains other than USA300-LV are lacking. In this study, we aimed to characterize possible mechanisms of acquisition and transfer of MRG in LA S. aureus.

Methods

We sequenced 6 MRSA and 2 MSSA clinical isolates harboring MRG from Colombia, Ecuador, Peru and Chile using short-read (Illumina) and long-read (ONT) sequencing. Hybrid assemblies were constructed using Flye and iterative polishing with Medaka and Racon. Identification of insertion sequences, rearrangements and assessment of the genomic context was investigated using ISfinder, MAUVE, PlasmidFinder and SnapGene.

Results

Highly contiguous genome assemblies allowed us to identify the localization and genetic background of MRG. For MRSA belonging to USA300-LV (SCCmecIVc/E) and Brazilian (SCCmecIII) clones, we confirmed the presence of MRG within SCCmec. In contrast, for the 4 MRSA belonging to Chilean/Cordobes clone (SCCmecI), collected from Colombia, Chile and Peru, MRG were located on ~30kbp plasmids genetically related that also contained the blaZ beta-lactamase and cadmium/arsenic resistance genes. In MSSA strains, we observed both plasmidic and chromosomal localizations of MGR. Interestingly, in one of the MSSA, MRG were inserted downstream of orfX, along with repA, suggesting a plasmidic origin. In all these cases, MRG were flanked by IS6 family elements.

Conclusion

Genomic architecture of SCCmec types IVc/E and III might facilitate MRG transferability, whereas for the highly prevalent Chilean/Cordobes clone (SCCmecI) MRG acquisition occurs through plasmids. Our findings underscore the mechanisms of MRG transference in LA S. aureus likely related to antibiotic resistance co-selection.

Disclosures

Cesar A. Arias, MD, MSc, PhD, FIDSA, Entasis Therapeutics (Scientific Research Study Investigator)MeMed (Scientific Research Study Investigator)Merck (Grant/Research Support)
1444. Characterization of a Novel Pathogen in Immunocompromised Patients: Elizabethkingia Anopheles
Authors: Yasmin Mohamad , Marshall Steven , Marshall Emma , Cmolik Anna , Boucher Helen , Vila Alejandro , Bonomo Robert A
Published: January 2021

Background

A 60-year-old woman with acute myeloid leukemia developed fever and cough post induction chemotherapy. Meropenem and vancomycin were administered as empiric therapy. A bloodstream infection due to resistant E. meningoseptica was initially identified. Ceftazidime-avibactam and aztreonam (ATM) were next administered. Minocycline and trimethoprim/sulfamethoxazole (TMP/SMX) were added as the patient deteriorated and died ten days later.

Methods

MIC testing /disc diffusion assays were done according to CLSI guidelines. Whole genome sequencing (WGS) was performed, assembled, and annotated using PATRIC.org and compared to Institute Pasteur cgMLST instance of the BIGSdb database tool. Resistant genes and plasmids were identified by the Center for Genomic epidemiology.

Results

Core genome MLST and average nucleotide identity of 99.46% revealed the organism as E. anophelis, not E. meningoseptica. The WGS assembly resulted in 118 contigs with a chromosome of 4,110,726 bp. Plasmids were not identified. Resistance genes blaB11, blaGOB-13 (a metallo beta-lactamase) and blaCME-1 were detected. E. anophelis was resistant to multiple drug classes including aminoglycosides, vancomycin, cephalosporins, and carbapenems. Mechanism based susceptibility testing using double-disc diffusion assays demonstrated susceptibility to cefiderocol (MIC 1 µg/ml), minocycline, TMP/SMX, linezolid, and modestly wider zones of inhibition with the addition of ATM. Susceptibility results are shown in Table 1.

Antimicrobial susceptibility testing using various BLIs and combinations with Aztreonam

Conclusion

This is one of the first reports describing E. anophelis in immunocompromised hosts. More thorough testing methods are needed for distinguishing between species in the Elizabethkingia genus in hospital settings as there is concern that this may represent a novel opportunistic infection. Per CDC, E. anophelis outbreaks have occurred in three Midwestern states in 2016. Vigilance is warranted to the role of this pathogen in immunocompromised hosts.

Disclosures

Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)
1445. Deciphering the Role of the Y221H Ω-loop Substitution in Pseudomonas-derived Cephalosporinase (PDC) in Cephalosporin Resistance
Authors: Mack Andrew R , Barnes Melissa D , Taracila Magdalena A , Mojica Maria F , Kumar Vijay , Rutter Joseph , van den Akker Focco , Page Malcolm , Haider Shozeb , Bonomo Robert A
Published: January 2021

Background

Antimicrobial resistance is a major global health threat. Pseudomonas aeruginosa is a leading cause of nosocomial infections and a key opportunistic pathogen in cystic fibrosis. Multidrug resistant strains are classified as a “serious threat” by the CDC. Pseudomonas-derived cephalosporinase (PDC) is largely responsible for β-lactam antibiotic resistance in P. aeruginosa. Single amino acid substitutions in the essential Ω-loop region (e.g. Y221H by structural alignment-based numbering of class C β-lactamases) have been shown to enhance hydrolysis of ceftazidime (CAZ) and ceftolozane (TOL), limiting therapeutic options for P. aeruginosa.

Methods

We undertook detailed studies to explore the mechanisms by which Y221H enhances CAZ and TOL MICs. MIC measurements were performed per CLSI guidelines using MH Agar. Thermal stability was determined by circular dichroism. Enzyme kinetic properties were determined using spectrophotometric techniques. Molecular dynamics techniques were used to predict structural changes.

Results

E. coli expressing blaPDC-3-Y221H is less susceptible to CAZ (MIC 0.5 mg/L WT → 8 mg/L Y221H) and TOL (MIC 2 mg/L WT → 16 mg/L Y221H). Using steady-state kinetic analysis, Y221H was found to hydrolyze CAZ with a KM = 585 µM, a kcat = 3.4 sec-1, and kcat/KM = 0.0058 µM-1s-1. With cephalothin, a good PDC substrate, we observed KM = 26.6 µM, kcat = 70.1 s-1, and kcat/KM = 2.6 µM-1 s-1 for Y221H. Using Electrospray ionization mass spectrometry (ESI-MS), CAZ was detected covalently bound to WT, but not Y221H when incubated at 1000-fold molar excess. Avibactam (AVI) inhibited Y223H (Ki = 70 nM vs. 19 nM for WT). Y221H thermal stability decreased by 5°C (Tm = 47°C vs 52°C WT). AVI at 10-fold molar excess does not increase Tm in Y221H or WT. WT-MetaDynamics (WT MDS) predicts the opening of a hidden pocket by repositioning residue 221 (Figure 1).).

Figure 1: (Left) We carried out enhanced sampling metadynamics simulations to generate free-energy landscapes as a function of the dihedral angles of residue 221. This identifies the differences in the dynamics of the tyrosyl side chains in the wild type Y221 and the imidazole ring of the H221 variant. (Right) The rotation of the side chain in H221 opens a cryptic pocket (green mesh), which is occluded in the wild type. The Ω-loop is colored red.

Conclusion

PDC-3 Y221H increases CAZ & TOL MICs and alters catalytic activity, primarily by a change in kcat. Our modelling analyses suggest altered conformational flexibility and structure-function relationships in the Ω-loop. These results help to advance our understanding of PDC and will inform development of novel antibiotics and inhibitors.

Disclosures

Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)
1448. Forgiveness of BIC/FTC/TAF: In Vitro Simulations of Intermittent Poor Adherence Find Limited HIV-1 Breakthrough and High Barrier to Resistance
Authors: Mulato Andrew , Acosta Rima K , Yant Stephen R , Cihlar Tomas , White Kirsten L
Published: January 2021

Background

Short lapses in adherence to ARVs can lead to virologic failure and emergence of resistance. Previous in vitro studies of regimen “forgiveness” simulated drug exposures of perfect adherence or short-term suboptimal adherence with bictegravir+emtricitabine+tenofovir alafenamide (BIC+FTC+TAF) and with dolutegravir and lamivudine (DTG+3TC). Here, viral breakthrough (VB) and resistance development were evaluated under alternating high and low drug exposures simulating variable adherence levels.

Methods

Wild-type HIV-1 (IIIb)-infected MT-2 cells were exposed to drug combinations and monitored for VB. Experiments alternated between high and low drug concentrations of either BIC+FTC+TAF or DTG+3TC (Table 1). Drug concentrations for each regimen were determined using human plasma-free adjusted clinical trough concentrations (Cmin), at simulated Cmin after missing 2 or 4 consecutive doses (Cmin-2 and Cmin-4) based on drug half-lives. Emergent HIV-1 were genotyped by deep sequencing and a 2% threshold.

Results

In these experiments, constant drug concentrations corresponding to full adherence (Cmin) did not lead to VB. Using Cmin concentrations for one week followed by constant Cmin-2 exposures for 4 weeks, DTG+3TC had VB and emergence of M184V/I in reverse transcriptase (RT) but there was no VB for BIC+FTC+TAF. Using alternating drug exposures of Cmin (weeks 1 and 3) and Cmin-2 or Cmin -4 (weeks 2, 4, and 5), VB was not observed with BIC+FTC+TAF, and VB was decreased or delayed with DTG+3TC compared to DTG+3TC held at Cmin-2 or Cmin-4. Resistance development was observed in some cultures with VB: 1 culture with BIC+FTC+TAF had G163R in IN and 19 cultures with DTG+3TC had INSTI and RT resistance including 10 with M184V/I.

Table 1. Summary of Breakthrough Frequency and Resistance Development

Conclusion

BIC+FTC+TAF has high in vitro forgiveness and consistent protection against emergence of drug resistance during simulations of short lapses in adherence. Higher DTG+3TC exposure, whether constant or intermittent, was better at preventing or delaying VB than lower DTG+3TC exposures, but DTG+3TC was less forgiving than BIC+FTC+TAF. Prevention of viral replication and resistance development is necessary to maintain lifelong viral suppression, particularly in the real world where drug adherence is often imperfect.

Disclosures

Andrew Mulato, BS, MBA, Gilead Sciences, Inc. (Employee, Shareholder) Rima K. Acosta, BS, Gilead Sciences, Inc. (Employee, Shareholder) Stephen R. Yant, PhD, Gilead Sciences, Inc. (Employee, Shareholder) Tomas Cihlar, PhD, Gilead Sciences, Inc. (Employee, Shareholder) Kirsten L. White, PhD, Gilead Sciences, Inc. (Employee, Shareholder)
118. Optimizing the management of coagulase-negative staphylococci (CoNS) contaminants by reporting the species name
Authors: Stone Tyler J , Palavecino Elizabeth , Palavecino Elizabeth , Jessica Smith , Beardsley James , Johnson James , Luther Vera , Ohl Christopher , Ohl Christopher , Williamson John
Published: January 2021

Background

CoNS are common isolates in blood cultures (BCx), but many are contaminants contributing to unnecessary antibiotic use. When CoNS are isolated from multiple BCx, different species and/or different susceptibility patterns may suggest contamination. Species reporting of CoNS is not performed at all hospitals. The purpose of this study was to characterize antibiotic use attributable to CoNS positive (pos) BCx and determine if reporting CoNS species could help reduce unnecessary antibiotics.

Methods

A retrospective chart review was conducted of inpatients at an academic medical center before (Jan-June 2017) and after (Sept 2019-Feb 2020) implementation of CoNS species reporting. CoNS species were hidden to providers in the before group. Patients (pts) ≥18 years old with ≥1 BCx pos for CoNS were included. Pts who were neutropenic, treated with anti-staphylococcal antibiotics (SAbx) for a non-CoNS infection, or treated for CoNS with non-SAbx were excluded. Pts were categorized by number of pos BCx (1 vs ≥2). In each period, a random sample of pts was screened until 50 pts with 1 CoNS pos BCx were included. Additional data were collected until at least 50 pts with ≥2 pos BCx were included in each period. The primary outcome was use of SAbx among pts in each group before and after species reporting. Additional analyses were performed to compare the use of SAbx among subsets with same/different species and/or susceptibilities.

Results

203 pts were included, 102 before and 101 after. 51% and 50% had ≥2 pos BCx in the before and after groups, respectively. S. epidermidis was isolated more frequently in pts with ≥2 pos BCx (75% vs 50%, p< 0.001). 77% of pts received at least 1 SAbx (97% vancomycin). Median SAbx days of therapy per pt (DOTs) was greater among pts with ≥2 pos BCx (1 vs 5, p< 0.001). There was no difference in overall DOTs between the two periods (3 vs 2, p=0.25). However, among pts with ≥2 pos BCx, median DOTs was less in the after period (6.5 vs 3, p=0.016). Among pts with 1 pos BCx, median DOTs was 1 in both periods.

Median Anti-Staphylococcal Antibiotic Days of Therapy per Patient (≥ 2 positive cultures)

Conclusion

CoNS species reporting was associated with decreased SAbx use for pts with ≥2 pos BCx, suggesting that knowing the species helps in determining likelihood of true infection. Institutions may realize improved stewardship metrics of SAbx by implementing CoNS species reporting for pos BCx.

Disclosures

Tyler J. Stone, PharmD, Paratek (Research Grant or Support) Elizabeth Palavecino, MD, Paratek (Grant/Research Support)Paratek (Grant/Research Support) John Williamson, PharmD, Paratek (Research Grant or Support)
1450. Frequency of Carbapenem-resistant Pseudomonas aeruginosa Among Respiratory Pathogens Impacts First-Line Beta-Lactam Susceptibility: Potential Role for Ceftolozane/Tazobactam (C/T) and/or Imipenem/Relebactam (I/R)
Authors: Klinker Kenneth , DePestel Daryl , Motyl Mary , DeRyke C Andrew
Published: January 2021

Background

Carbapenem-resistant P. aeruginosa (CRPA) are associated with increased mortality and impose significant treatment challenges for clinicians. Among CRPA, co-resistance to 1st line antipseudomonal agents piperacillin/tazobactam (TZP) and cefepime (FEP) is common and often results in delays to timely effective therapy. A simple strategy for identifying patients at risk for suboptimal therapy is evaluation of institutional or unit specific frequency of CRPA. The purpose of this analysis is to identify beta-lactam (BL) susceptibility trends based on CRPA frequency observed in intensive care units (ICU).

Methods

In 2016-2019, ~20 US institutions per year submitted up to 250 consecutive, aerobic or facultatively anaerobic, gram-negative pathogens from blood, intra-abdominal, urinary, and lower respiratory tract infections as part of the Study for Monitoring Antimicrobial Resistance Trends. A total of 871 P. aeruginosa (PA) isolates were collected from lower respiratory tract specimens obtained from ICU patients. MICs were determined using CLSI broth microdilution method and interpreted with CLSI 2020 or FDA breakpoints. Institutions were then stratified into one of three categories based on CRPA frequency: CRPA rates ≤20% (CR1), 21 – 40% (CR2), and ≥41% (CR3). BL susceptibility was then evaluated relative to CRPA frequency.

Results

Thirty-seven (46%), 25 (31%), and 18 (23%) institutions were stratified into CR1, CR2, and CR3, respectively. Overall, CRPA was identified in 28.4% of all ICU lower respiratory isolates. Significant declines in FEP and TZP susceptibility were observed in institutions that demonstrated higher CRPA frequency (p< 0.00001) (Table 1) with >25% of isolates showing resistance in CR2 and CR3. In contrast, C/T susceptibility remained above 90% for all categories. I/R susceptibility remained above 90% for CR1 and CR2.

Table 1. P. aeruginosa susceptibility among ICU lower respiratory tract isolates stratified by unit specific frequency of carbapenem resistance

Conclusion

C/T and I/R provide robust activity against PA isolates obtained from the lower respiratory tract of critically ill patients, regardless of CR frequency. Assessing CRPA frequency may be useful for identifying inflection points in which novel agents could be considered. In settings where CRPA frequency exceeded 20%, additional testing or early switch to C/T or I/R may be warranted.

Disclosures

Kenneth Klinker, PharmD, Merck & Co, Inc (Employee) Daryl DePestel, PharmD, BCPS-ID, Merck & Co, Inc (Employee) Mary Motyl, PhD, Merck & Co, Inc (Employee, Shareholder) C. Andrew DeRyke, PharmD, Merck & Co., Inc. (Employee, Shareholder)
1452. Molecular Profile of β-Lactamase Genes and Siderophore-Dependent Iron Transporter Genes of Cefiderocol High MIC Isolates from SIDERO-WT Studies
Authors: Yamano Yoshinori , Takemura Miki , Kazmierczak Krystyna , Wise Mark G G , Hackel Meredith , Sahm Daniel F , Echols Roger
Published: January 2021

Background

Cefiderocol (CFDC) is a novel siderophore cephalosporin with efficacy against Gram-negative (GN) bacteria, including carbapenem-resistant Enterobacterales and non-glucose-fermenters such as Pseudomonas aeruginosa and Acinetobacter baumannii. In consecutive multinational surveillance (SIDERO-WT) studies (2014–2017), CFDC demonstrated activity with minimum inhibitory concentrations (MICs) of ≤4 mg/mL against 99.4% of 28,629 GN clinical isolates. We conducted molecular characterization of 161 isolates with CFDC MICs >4 mg/mL from the SIDERO-WT studies.

Methods

A total of 161 isolates underwent whole genome sequencing by Illumina Hiseq. Analyses were done using the CLC genomics workbench (Qiagen) for possible resistance-related genes (e.g. β-lactamases, porin channels or penicillin-binding protein genes) and some TonB-dependent siderophore uptake receptor genes (fiu, cir, piu, pir). Fiu and Cir in Escherichia coli and Piu in P. aeruginosa are the iron transporters involved in CFDC transport.

Results

Of 161 isolates with CFDC MIC >4 mg/mL, 128 were A. baumannii, 22 Enterobacterales, 7 Burkholderia multivorans, 2 P. aeruginosa, and 2 Stenotrophomonas maltophilia. Genes encoding PER/VEB extended-spectrum β-lactamases and NDM-type metallo-β-lactamases were detected in some isolates, but other β-lactamase genes (bla) were not shown to be linked to high CFDC MICs. blaPER/blaVEB were found only in A. baumannii and blaNDM was found in A. baumannii and Klebsiella pneumoniae. In 128 A. baumannii isolates, 103 harbored PER or VEB, including PER positive isolates from Russia (n=87) and Turkey (n=6) and 4 VEB positive isolates from USA. Nine NDM-positive isolates (7 K. pneumoniae, 2 A. baumannii) were found. Disruption of iron transport genes was also detected in some isolates, including piuA (11 A. baumannii, 1 P. aeruginosa), pirA (2 A. baumannii), and fiuA (4 B. multivorans, 1 Proteus mirabilis). No cir homologs were found in 2 B. multivorans.

Conclusion

PER and NDM could reduce susceptibility to CFDC, as such isolates have been seen in some countries. Iron transporter disruption was also observed in some isolates with high CFDC MICs; the contribution of these deficiencies in A. baumannii and B. multivorans requires further study.

Disclosures

Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Krystyna Kazmierczak, PhD, Shionogi & Co., Ltd. (Independent Contractor) Mark G G. Wise, PhD, Shionogi & Co., Ltd. (Independent Contractor) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor) Roger Echols, MD, Shionogi Inc. (Consultant)
1455. Potential Mechanisms of Cefiderocol MIC Increase in Enterobacterales in In Vitro Resistance Acquisition Studies
Authors: Yamano Yoshinori , Nakamura Rio , Takemura Miki , Echols Roger
Published: January 2021

Background

Cefiderocol (CFDC) is a novel siderophore, iron-chelating cephalosporin, which is transported into bacteria via iron transporters. CFDC has potent in vitro and in vivo activity against all aerobic Gram-negative bacteria, including carbapenem-resistant strains. To date, clinical isolates with cefiderocol MIC >4 µg/mL have been found infrequently, in which the presence of a few β-lactamases or altered iron transport was found. We investigated potential new mechanisms causing CFDC MIC increases in non-clinical studies.

Methods

The mutation positions were determined by whole genome sequencing using four K. pneumoniae mutants including two KPC producers and one NDM producer that had shown CFDC MIC increases in previous in vitro resistance-acquisition studies. The mutant strains were obtained at the frequency of 10-7 to < 10-8 by spreading bacteria on standard Mueller‒Hinton agar medium containing CFDC at concentrations of 10× MIC, with or without apo-transferrin (20 μg/mL). CFDC MIC was determined by broth microdilution using iron-depleted cation-adjusted Mueller-Hinton broth based on Clinical and Laboratory Standards Institute guidelines. The emergence of MIC increase mutants was also assessed by in vitro chemostat models under humanized plasma pharmacokinetic exposures of CFDC.

Results

The possible resistance mechanisms were investigated. Mutation of baeS or envZ, sensors of two-component regulation systems, were found in three or two mutants among the tested four isolates, respectively, and caused the MIC to increase by 4–32-fold. The altered expression level of specific genes by the baeS or envZ mutation could affect CFDC susceptibility, but the specific genes have not been identified. In addition, the mutation of exbD, an accessory protein related to iron transport, was identified in one case and caused the MIC to increase by >8-fold. In vitro chemostat studies using two isolates (one NDM producer and one KPC producer) showed no resistance acquisition during 24-hour exposure.

Table. Overview of mutation emergence in five isolates of K. pneumoniae

Conclusion

The mutation of two-component regulation systems (BaeSR and OmpR/EnvZ) and iron transport-related proteins were shown to be possible mechanisms causing CFDC MIC increases, but these mutants did not appear under human exposures.

Disclosures

Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Rio Nakamura, BSc, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant)
1458. Uncharted territories: applying “precision medicine” to understand the treacherous landscape of extensively and multidrug resistant (XDR and MDR) Pseudomonas aeruginosa in a patient with cystic fibrosis and lung transplantation
Authors: Rojas Laura J , Yasmin Mohamad , Benjamino Jacquelynn , Marshall Steven , DeRonde Kailynn , Krishnan Nikhil , Perez Federico , Colin Andrew , Cardenas Monica , Martinez Octavio , Perez-Cardona Armando , Rhoads Daniel , Jacobs Michael , Scott Jacob , Adams Mark D , Abbo Lilian M , Abbo Lilian M , Bonomo Robert A
Published: January 2021

Background

Pseudomonas aeruginosa is a persistent and difficult-to-treat pathogen in many patients, especially those with cystic fibrosis (CF). Herein, we describe our experience managing a young woman suffering from CF with XDR P. aeruginosa who underwent lung transplantation. We highlight the contemporary difficulties reconciling the clinical, microbiological, and genetic information.

Methods

Mechanism-based-susceptibility disk diffusion synergy testing with double and triple antibiotic combinations aided in choosing tailored antimicrobial combinations to control the infection in the pre-transplant period, create an effective perioperative prophylaxis regimen, and manage recurrent infections in the post-transplant period. Thirty-six sequential XDR and PDR P. aeruginosa isolates obtained from the patient within a 17-month period, before and after a double-lung transplant were analyzed by whole genome sequencing (WGS) and RNAseq in order to understand the genetic basis of the observed resistance phenotypes, establish the genomic population diversity, and define the nature of sequence changes over time

Results

Our phylogenetic reconstruction demonstrates that these isolates represent a genotypically and phenotypically heterogeneous population. The pattern of mutation accumulation and variation of gene expression suggests that a group of closely related strains was present in the patient prior to transplantation and continued to evolve throughout the course of treatment regardless of antibiotic usage.Our findings challenge antimicrobial stewardship programs that assist with the selection and duration of antibiotic regimens in critically ill and immunocompromised patients based on single-isolate laboratory-derived resistant profiles. We propose that an approach sampling the population of pathogens present in a clinical sample instead of single colonies be applied instead when dealing with XDR P. aeruginosa, especially in patients with CF.

Conclusion

In complex cases such as this, real-time combination testing and genomic/transcriptomic data could lead to the application of true “precision medicine” by helping clinicians choose the combination antimicrobial therapy most likely to be successful against a population of MDR pathogens present.

Disclosures

Federico Perez, MD, MS, Accelerate (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support) Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)
1468. Culture Conversion and Mortality in Patients With Mycobacterium abscessus (MAB) Lung Disease: A Systematic Literature Review
Authors: Winthrop Kevin L , Mange Kevin C , Jumadilova Zhanna , Cline Kristan B , Flume Patrick A
Published: January 2021

Background

Prognosis for patients with MAB lung disease is poor. We sought to examine the potential association between culture conversion and outcomes (progression, mortality) in patients with MAB lung disease.

Methods

English-language MAB lung disease studies with ≥ 10 patients and reporting mortality and/or microbiological outcomes were identified from Embase, PubMed, relevant congress abstracts, and the Cochrane Library (data cutoff, September 24, 2019) using the National Institute for Health and Clinical Excellence guidance for systematic literature reviews. Two independent reviewers screened 1,551 indexed records; relevant extracted data are expressed as population-weighted means.

Results

Mean all-cause mortality across 17 studies (N=1,291) was 12.1% (range, 3%–33%); mortality attributable to MAB lung disease was 7.6% (range, 0%–27%; N=526, 9 studies). Culture conversion across 44 studies (N=2,237) was 46.7% (range, 0%–98.6%), with higher rates reported for M. massiliense subspecies (76.9%; N=507,15 studies) than M. abscessus subspecies (35.8%; N=834,18 studies). No direct comparisons were made between mortality and culture conversion; in the 13 studies (N=1,202) that reported both outcomes there was a moderate correlation between increased rate of culture conversion and decreased MAB-attributable mortality (R2=0.60). The most common definition of progression (21 studies) was radiographic worsening supported by persistent symptoms and/or positive cultures. Across 8 studies (N=415) 57.8% patients had improvement while 35.2% progressed with treatment. A broad variance in treatment regimen and duration (range, 32 days to > 3 years) was observed. Limitations include a small number of studies, and inconsistency in methods and outcomes definitions.

Conclusion

In this systematic literature review, available data suggest that culture conversion was achieved in less than half of patients and was lower in patients with M. abscessus compared with M. massiliense. One third of patients had disease progression despite treatment. Some data suggest lower MAB-attributed mortality outcomes in studies with higher culture conversion rates, more evidence is needed to demonstrate a survival benefit associated with culture conversion.

Disclosures

Kevin L Winthrop, MD, MPH, Insmed Incorporated (Consultant, Grant/Research Support) Kevin C Mange, MD, MSCE, Insmed Incorporated (Employee) Zhanna Jumadilova, MD, Insmed Incorporated (Employee) Kristan B Cline, PhD, Insmed Incorporated (Employee) Patrick A Flume, MD, Insmed Incorporated (Grant/Research Support, Scientific Research Study Investigator, Advisor or Review Panel member)