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BACKGROUND Extended-spectrum β-lactamase (ESBL)-producing Enterobacterales-(Ent) infections are increasing in pediatrics. Before CTX-M ESBL emerged, the most common infection-associated ESBL genes were TEM and SHV-type ESBLs. We sought to define the current epidemiology of Ent infections in children due to blaTEM and blaSHV (TEM-SHV-Ent). METHODS A retrospective case-control analysis of children with TEM-SHV-Ent infections at 3 Chicago-area hospitals was performed. Cases had extended-spectrum-cephalosporin (ESC)-resistant infections due to blaTEM or blaSHV. DNA analysis assessed β-lactamase (bla) genes, multilocus sequence types, and E. coli phylogenetic grouping. Controls had ESC-susceptible Ent infections, matched 3:1 to cases by age, source, and hospital. Clinical-epidemiologic infection predictors were assessed. RESULTS Of 356 ESC-R-Ent isolates from children (median 4.3 years), 38 (10.7%) were positive solely for blaTEM-ESBL (26%) or blaSHV-ESBL genes (74%). Predominant organisms were Klebsiella (34.2%) and E. coli (31.6%); 67% of E. coli were phylogroup B2. Multilocus sequence types revealed multiple strains, 58% resistant to ≥3 antibiotic classes. On multivariable analysis, children with TEM-SHV-Ent infections more often had recent inpatient care (OR, 8.2), yet were diagnosed mostly as outpatients (OR, 25.6) and less in Neonatal Intensive Care Units (OR, 0.036) than controls. TEM-SHV-Ent patients had more gastrointestinal (OR, 23.7) and renal comorbidities (OR, 4.2). Differences in demographics, antibiotic exposure, and foreign bodies were not found. CONCLUSION TEM-SHV-Ent are commonly linked to inpatient exposures in children with chronic conditions but most often present in outpatient settings. Clinicians should be aware of the potential increased risk for TEM-SHV-Ent infections in outpatients with gastrointestinal and renal comorbidities and histories of prolonged hospital stays.

BACKGROUND: Carbapenem-resistant Enterobacteriaceae (CRE) are a global threat. Here, we describe the clinical and molecular characteristics of Centers for Disease Control and Prevention (CDC)-defined CRE in the US. METHODS: The second Consortium on Resistance Against Carbapenems in Klebsiella and other Enterobacteriaceae (CRACKLE-2, ClinicalTrials.gov: NCT03646227) is a prospective, multicenter, cohort study. Patients hospitalized in 49 US hospitals, with clinical cultures positive for CDC-defined CRE between 30 April 2016 and 31 August 2017 were included. Primary outcome was desirability of outcome ranking (DOOR) at 30 days. Clinical data and bacteria were collected, and whole genome sequencing (WGS) was performed. FINDINGS: 1,040 patients with unique isolates were included; 449 (43%) with infection and 591 (57%) with colonization. CDC-defined CRE admission rate was 57 CDC-defined CRE admissions/100,000 admissions (95% CI: 45–71). Three subsets of CDC-defined CRE were identified: carbapenemase-producing Enterobacteriaceae (618/1,040, 59%); non-carbapenemase-producing CRE (194/1,040, 19%); and unconfirmed CRE (228/1,040, 22%; initially reported as CRE, but susceptible to carbapenems in two central laboratories). Klebsiella pneumoniae carbapenemase (KPC)-producing clonal group 258 K. pneumoniae was the most common carbapenemase-producing Enterobacteriaceae. In 449 patients with CDC-defined CRE infections, DOOR outcomes were not significantly different in patients with carbapenemase-producing Enterobacteriaceae, non-carbapenemase-producing CRE, and unconfirmed CRE. At 30 days 107/449 (24%, 95% CI 20–28%) patients had died. INTERPRETATION: Among patients with CDC-defined CRE, similar outcomes were observed among three subgroups, including the novel unconfirmed CRE group. CDC-defined CRE represent diverse bacteria, whose spread may not respond to interventions directed to carbapenemase-producing Enterobacteriaceae. FUNDING: National Institutes of Health

Multidrug-resistant (MDR) Pseudomonas aeruginosa infections are a major clinical challenge. Many isolates are carbapenem resistant, which severely limits treatment options; thus, novel therapeutic combinations, such as imipenem-relebactam (IMI/REL), ceftazidime-avibactam (CAZ/AVI), ceftolozane-tazobactam (TOL/TAZO), and meropenem-vaborbactam (MEM/VAB) were developed. Here, we studied two extensively drug-resistant (XDR) P. aeruginosa isolates, collected in the United States and Mexico, that demonstrated resistance to IMI/REL. Whole-genome sequencing (WGS) showed that both isolates contained acquired GES β-lactamases, intrinsic PDC and OXA β-lactamases, and disruptions in the genes encoding the OprD porin, thereby inhibiting uptake of carbapenems. In one isolate (ST17), the entire C terminus of OprD deviated from the expected amino acid sequence after amino acid G388. In the other (ST309), the entire oprD gene was interrupted by an ISPa1328 insertion element after amino acid D43, rendering this porin nonfunctional. The poor inhibition by REL of the GES β-lactamases (GES-2, -19, and -20; apparent K(i) of 19 ± 2 μM, 23 ± 2 μM, and 21 ± 2 μM, respectively) within the isolates also contributed to the observed IMI/REL-resistant phenotype. Modeling of REL binding to the active site of GES-20 suggested that the acylated REL is positioned in an unstable conformation as a result of a constrained Ω-loop.

Background Fluoroquinolones are uncommonly prescribed in children, yet pediatric multidrug resistant (MDR) enterobacteriaceae (Ent) infections often reveal fluoroquinolone resistance (FQR). We sought to define the molecular epidemiology of FQR and MDR-Ent in children. Methods A case-control analysis of children with MDR-Ent infections at 3 Chicago hospitals was performed. Cases were children with third-generation cephalosporin-resistant and/or carbapenem-resistant Ent infections. Polymerase chain reaction and DNA analysis assessed bla and plasmid-mediated FQR (PMFQR) genes. Controls were children with third-generation cephalosporin, fluoroquinolone, and carbapenem-susceptible Ent infections matched by age, source and hospital. We assessed clinical-epidemiologic predictors of PMFQR Ent infection. Results Of 169 third-generation cephalosporin-resistant and/or carbapenem-resistant Ent isolates from children (median age, 4.8 years), 85 were FQR; 56 (66%) contained PMFQR genes. The predominant organism was Escherichia coli, and most common bla gene blaCTX-M-1 group. In FQR isolates, PMFQR gene mutations included aac6'1bcr, oqxA/B, qepA and qnrA/B/D/S in 83%, 15%, 13% and 11% of isolates, respectively. FQR E. coli was often associated with phylogroup B2, ST43/ST131. On multivariable analysis, PMFQR Ent infections occurred mostly in outpatients (odds ratio, 33.1) of non-black-white-Hispanic race (odds ratio, 6.5). Residents of Southwest Chicago were >5 times more likely to have PMFQR Ent infections than those in the reference region, while residence in Central Chicago was associated with a 97% decreased risk. Other demographic, comorbidity, invasive-device, antibiotic use or healthcare differences were not found. Conclusions The strong association of infection with MDR organisms showing FQR with patient residence rather than with traditional risk factors suggests that the community environment is a major contributor to spread of these pathogens in children.

Background Fluoroquinolones (FQs) are not commonly prescribed in children, yet the increasing incidence of multidrug resistant (MDR) Ent infections in this population often reveals FQ resistance. We sought to define the role of FQ resistance in the epidemiology of MDR Ent in children, with an overall goal to devise treatment and prevention strategies. Methods A case-control study of children (0-18 years) at 3 Chicago hospitals was performed. Cases had infections by FQ susceptible, 3rd generation cephalosporin-resistant (3GCR) and/or carbapenem-resistant (CR) Ent harboring a non or low level expressed PMFQR gene (PMFQS Ent). Controls had FQR infections due to 3GCR and/or CR Ent with expressed PMFQR genes (PMFQR Ent). We sought bla genes by PCR or DNA (BD Max Check-Points assay®) and PMFQR genes by PCR. We performed Rep-PCR, MLST, and E. coli phylogenetic grouping. Demographics; comorbidities; and device, antibiotic, and healthcare exposures were evaluated. Predictors of infection were assessed. Results Of 170 G3CR and/or CR Ent isolates, 85 (50%) were FQS; 23 (27%) had PMFQR genes (PMFQS cases). 85 (50%) were FQR; 53 (62%) had PMFQR genes (PMFQR controls). The median age for children with PMFQS Ent and PMFQR Ent were 4.3 and 6.2 years, respectively (p=NS). Of 23 PMFQS Ent, 53% were Klebsiella and of 53 PMFQR Ent, 76% were E. coli. The most common bla and PMFQR genes in PMFQS Ent were blaSHV ESBL (44%); oqxB (57%) and aac-6’1b-cr (52%) and in PMFQR Ent were blaCTX-M-1 group (76%); aac-6’1b-cr (91%) and oqxA (17%). Multivariable regression analysis showed children with PMFQS Ent infections were more likely to have hospital onset infection (OR 5.7, 95% CI 1.6-22) and isolates with multiple bla genes (OR 3.8, 95% CI 1.1-14.5). The presence of invasive devices mediated the effects of healthcare setting in the final model. Differences in demographics, comorbidities, or antibiotic use were not found. Conclusion Paradoxically, PMFQS Ent infections were often hospital onset and PMFQR Ent infections were community onset. PMFQS Ent commonly co-harbored multiple bla and PMFQR genes, affecting therapeutic options and suggesting need for contact precautions. Control of PMFQS Ent infections in children will require validating sources and risk factors. Disclosures Robert A. Bonomo, MD, entasis (Research Grant or Support)Merck (Grant/Research Support)NIH (Grant/Research Support)VA Merit Award (Grant/Research Support)VenatoRx (Grant/Research Support)

Treatment of multidrug-resistant Gram-negative bacterial pathogens represents a critical clinical need. Here, we report a novel γ-lactam pyrazolidinone that targets penicillin-binding proteins (PBPs) and incorporates a siderophore moiety to facilitate uptake into the periplasm. The MIC values of γ-lactam YU253434, 1, are reported along with the finding that 1 is resistant to hydrolysis by all four classes of β-lactamases. The druglike characteristics and mouse PK data are described along with the X-ray crystal structure of 1 binding to its target PBP3.

BackgroundOvercoming β-lactam resistance in pathogens such as Pseudomonas aeruginosa is a major clinical challenge. Rapid molecular diagnostics (RMDs) have the potential to inform selection of empiric therapy in patients infected by P. aeruginosa.MethodsIn this study, we used a heterogeneous collection of 197 P. aeruginosa that included multidrug-resistant isolates to determine whether 2 representative RMDs (Acuitas Resistome test and VERIGENE gram-negative blood culture test) could identify susceptibility to 2 newer β-lactam/β-lactamase inhibitor (BL-BLI) combinations, ceftazidime/avibactam (CZA) and ceftolozane/tazobactam (TOL/TAZO).ResultsWe found that the studied RMD platforms were able to correctly identify BL-BLI susceptibility (susceptibility sensitivity, 100%; 95% confidence interval [CI], 97%, 100%) for both BLs-BLIs. However, their ability to detect resistance to these BLs-BLIs was lower (resistance sensitivity, 66%; 95% CI, 52%, 78% for TOL/TAZO and 33%; 95% CI, 20%, 49% for CZA).ConclusionsThe diagnostic platforms studied showed the most potential in scenarios where a resistance gene was detected or in scenarios where a resistance gene was not detected and the prevalence of resistance to TOL/TAZO or CZA is known to be low. Clinicians need to be mindful of the benefits and risks that result from empiric treatment decisions that are based on resistance gene detection in P. aeruginosa, acknowledging that such decisions are impacted by the prevalence of resistance, which varies temporally and geographically.

Colistin and polymyxin B MICs were determined for 106 carbapenem-resistant Klebsiella pneumoniae (CR-Kp) isolates using Sensititre Research Use Only GNX2F plates (Thermo Fisher) and compared to CLSI broth macrodilution (BMD) as the reference method. For colistin, EUCAST breakpoints were applied and testing of isolates with very major (VM) errors was repeated in duplicate by both methods to determine a majority result. Essential agreement (MIC ± one dilution) of GNX2F with the reference method was 97.1% for polymyxin B and 92.5% for colistin (7 VM errors, 22.6%). After discrepancy testing, there were 28 colistin resistant isolates by BMD and essential agreement was 94.3% with 4 VM errors (14.3%). Colistin and polymyxin B GNX2F results showed acceptable essential agreement with BMD for MICS without interpretation. Colistin VM errors with EUCAST breakpoints were due to MIC variability in the 2 to 4 μg/mL range that could be addressed by establishing an intermediate category.

Plazomicin was tested against 697 recently acquired carbapenem-resistant Klebsiella pneumoniae isolates from the Great Lakes region of the United States. Plazomicin MIC 50 and MIC 90 values were 0.25 and 1 mg/liter, respectively; 680 isolates (97.6%) were susceptible (MICs of ≤2 mg/liter), 9 (1.3%) intermediate (MICs of 4 mg/liter), and 8 (1.1%) resistant (MICs of >32 mg/liter). Resistance was associated with rmtF -, rmtB -, or armA -encoded 16S rRNA methyltransferases in all except 1 isolate.

BACKGROUND: Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae (KPC-CRE) are multidrug-resistant organisms (MDRO) causing morbidity and mortality worldwide. KPC-CRE prevalence is increasing in pediatric populations, though multi-centered data are lacking. Identifying risk factors for KPC-CRE infection in children and classifying genotypes is a priority in this vulnerable population. METHODS: A case-case-control study of patients (0–22 years) at 3 tertiary-care Chicago-area medical centers, 2008–2015, was conducted. Case group 1 children possessed KPC-CRE infections; case group 2 harbored carbapenem-susceptible Enterobacteriaceae (CSE) infections; control had negative cultures. Case-control matching was 1:1:3 by age, infection site, and hospital. Statistical and molecular analyses were performed. RESULTS: Eighteen KPC-CRE infections were identified; median patient age was 16.5 years. Of 4 available KPC-CRE, two were unrelated, non-ST258 KP strains harboring bla(KPC-2), one was a ST258 KP harboring bla(KPC-3), and the last was an E. coli containing bla(KPC-2). KPC-CRE and CSE-infected patients had more MDRO infections, long-term care facility admissions, and lengths of stay (LOS) >7 days before culture. KPC-CRE and CSE patients had more gastrointestinal (GI) comorbidities (ORs 28.0 and 6.4) and ≥3 comorbidities (ORs 15.4 and 3.5) compared to controls; KPC-CRE patients had significantly more pulmonary and neurologic comorbidities (both ORs 4.4) or GI and pulmonary devices (ORs 11.4 and 6.1). Compared to controls, CSE patients had more prior fluoroquinolone use (OR 7.4); KPC-CRE patients had more carbapenem or aminoglycoside use (ORs 10.0 and 8.0). Race, gender, LOS, and mortality differences were insignificant. CONCLUSIONS: Pediatric patients with KPC-CRE infection suffer from high multi-system disease/device burdens and exposures to carbapenems and aminoglycosides. Different from adult reports, non-ST258 KP strains were more common, and LOS and mortality rates were similar in all groups. Pediatric CRE control in should focus on modifiable risk factors including antibiotic and device utilization.

The activity of the siderophore cephalosporin cefiderocol is targeted against carbapenem-resistant Gram-negative bacteria. In this study, the activity of cefiderocol against characterized carbapenem-resistant Acinetobacter baumannii complex, Stenotrophomonas maltophilia , Pseudomonas aeruginosa , and Enterobacteriaceae strains was determined by microdilution in iron-depleted Mueller-Hinton broth.

In the Consortium on Resistance Against Carbapenems in Klebsiella and other Enterobacteriaceae (CRACKLE), trimethoprim-sulfamethoxazole (TMP-SMX) had a limited role in the treatment of less severe carbapenem-resistant Enterobacteriaceae (CRE) infections, especially urinary tract infections. Of tested CRE, only 29% were susceptible to TMP-SMX. Development of resistance further limits the use of TMP-SMX in CRE infections.

BackgroundThe pandemic of extended-spectrum-beta-lactamase (ESBL)-producing-Enterobacteriaceae (Ent) is strongly linked to the dissemination of CTX-M-type-ESBL-Ent. We sought to define the epidemiology of infections in children due to an emerging resistance type, CTX-M-9-group-producing-Ent (CTX-M-9-grp-Ent).MethodsA multi-centered case-control analysis of Chicago children with CTX-M-9-grp-Ent infections was performed. Cases were defined as children possessing extended-spectrum-cephalosporin-resistant (ESC-R) infections. PCR and DNA analysis assessed beta-lactamase (bla) genes, multi-locus sequence types (MLST) and phylogenetic grouping of E. coli. Controls were children with ESC-susceptible (ESC-S)-Ent infections matched 3:1 by age, source, and hospital. The clinical-epidemiologic predictors of CTX-M-9-grp-Ent infection were assessed.ResultsOf 356 ESC-R-Ent isolates from children (median age 4.1 years), CTX-M-9-group was the solely detected bla gene in 44(12.4%). The predominant species was E. coli (91%) of virulent phylogroups D(60%) and B2(40%). MLST revealed multiple strain types. On multivariable analysis, CTX-M-9-grp-Ent occurred more often in E. coli (OR 7.0), children of non-black-white-Hispanic race (OR 6.5), and outpatients (OR 4.5) which was a very unexpected finding for infections due to antibiotic-resistant bacteria. Residents of South Chicago were 6.7 times more likely to have CTX-M-9-grp-Ent infections than those in the reference region (West), while residence in Northwestern Chicago was associated with an 81% decreased risk. Other demographic, comorbidity, invasive-device, and antibiotic use differences were not found.ConclusionsCTX-M-9-grp-Ent infection is strikingly associated with patient residence and is occurring in children without traditional in-patient exposure risk factors. This suggests that among children, the community environment may be a key contributor in the spread of these resistant pathogens.

The activity of the siderophore cephalosporin cefiderocol is targeted against carbapenem-resistant Gram-negative bacteria. In this study, the activity of cefiderocol against characterized carbapenem-resistant Acinetobacter baumannii complex, Stenotrophomonas maltophilia, Pseudomonas aeruginosa, and Enterobacteriaceae strains was determined by microdilution in iron-depleted Mueller-Hinton broth. The MIC(90)s against A. baumannii, S. maltophilia, and P. aeruginosa were 1, 0.25, and 0.5 mg/liter, respectively. Against Enterobacteriaceae, the MIC(90) was 1 mg/liter for the group harboring OXA-48-like, 2 mg/liter for the group harboring KPC-3, and 8 mg/liter for the group harboring TEM/SHV ESBL, NDM, and KPC-2.

Background:Fluoroquinolones (FQs) are uncommonly prescribed in children, yet pediatric multidrug-resistant (MDR)-Enterobacteriaceae (Ent) infections often reveal FQ resistance (FQR). We sought to define the molecular epidemiology of FQR and MDR-Ent in children.Methods:A case-control analysis of children with MDR-Ent infections at 3 Chicago hospitals was performed. Cases were children with third-generation-cephalosporin-resistant (3GCR) and/or carbapenem-resistant (CR)-Ent infections. PCR and DNA analysis assessed bla and plasmid-mediated FQR (PMFQR) genes. Controls were children with 3GC and carbapenem susceptible-Ent infections matched by age, source and hospital. We assessed clinical-epidemiologic predictors of PMFQR Ent infection.Results:Of 169 3GCR and/or CR Ent isolates from children (median age 4.8 years), 85 were FQR; 56 (66%) contained PMFQR genes. The predominant organism was E. coli and most common bla gene blaCTX-M-1 group. In FQR isolates, PMFQR gene mutations included aac6’1b-cr, oqxA/B, qepA, and qnrA/B/D/S in 83%, 15%, 13% and 11% of isolates, respectively. FQR E. coli was often associated with phylogroup B2, ST43/ST131. On multivariable analysis, PMFQR Ent infections occurred mostly in outpatients (OR 33.1) of non-black-white-Hispanic race (OR 6.5). Residents of Southwest Chicago were >5 times more likely to have PMFQR-Ent infections than those in the reference region, while residence in Central Chicago was associated with a 97% decreased risk. Other demographic, comorbidity, invasive-device, antibiotic use, or healthcare differences were not found.Conclusions:The strong association of infection with MDROs showing FQR with patient residence rather than with traditional risk factors suggests that the community environment is a major contributor to spread of these pathogens in children.

We report the emergence of colistin resistance in Klebsiella pneumoniae carbapenemase (KPC)–producing Klebsiella pneumoniae after 8 days of colistin-based therapy, resulting in relapse of bloodstream infection and death. Disruption of the mgrB gene by insertion of a mobile genetic element was found to be the mechanism, which was replicated in vitro after exposure to subinhibitory concentrations of colistin and meropenem.

We report the emergence of colistin resistance in Klebsiella pneumoniae carbapenemase (KPC)–producing Klebsiella pneumoniae after 8 days of colistin-based therapy, resulting in relapse of bloodstream infection and death. Disruption of the mgrB gene by insertion of a mobile genetic element was found to be the mechanism, which was replicated in vitro after exposure to subinhibitory concentrations of colistin and meropenem.

Carbapenem antibiotics are among the mainstays for treating infections caused by Acinetobacter baumannii , especially in the Northwest United States, where carbapenem-resistant A. baumannii remains relatively rare. However, between June 2012 and October 2014, an outbreak of carbapenem-resistant A. baumannii occurred in 16 patients from five health care facilities in the state of Oregon. All isolates were defined as extensively drug resistant. Multilocus sequence typing revealed that the isolates belonged to sequence type 2 (international clone 2 [IC2]) and were >95% similar as determined by repetitive-sequence-based PCR analysis. Multiplex PCR revealed the presence of a bla OXA carbapenemase gene, later identified as bla OXA-237 . Whole-genome sequencing of all isolates revealed a well-supported separate branch within a global A. baumannii phylogeny. Pacific Biosciences (PacBio) SMRT sequencing was also performed on one isolate to gain insight into the genetic location of the carbapenem resistance gene. We discovered that bla OXA-237 , flanked on either side by IS Aba1 elements in opposite orientations, was carried on a 15,198-bp plasmid designated pORAB01-3 and was present in all 16 isolates. The plasmid also contained genes encoding a TonB-dependent receptor, septicolysin, a type IV secretory pathway (VirD4 component, TraG/TraD family) ATPase, an integrase, a RepB family plasmid DNA replication initiator protein, an alpha/beta hydrolase, and a BrnT/BrnA type II toxin-antitoxin system. This is the first reported outbreak in the northwestern United States associated with this carbapenemase. Particularly worrisome is that bla OXA-237 was carried on a plasmid and found in the most prominent worldwide clonal group IC2, potentially giving pORAB01-3 great capacity for future widespread dissemination.

Background: Extremely drug-resistant (XDR) Acinetobacter baumannii is one of the most commonly encountered, highly resistant pathogens requiring novel therapeutic interventions. Methods: We developed C8, a monoclonal antibody (mAb), by immunizing mice with sublethal inocula of a hypervirulent XDR clinical isolate. Results: C8 targets capsular carbohydrate on the bacterial surface, enhancing opsonophagocytosis. Treating with a single dose of C8 as low as 0.5 μg/mouse (0.0167 mg/kg) markedly improved survival in lethal bacteremic sepsis and aspiration pneumonia models of XDR A. baumannii infection. C8 was also synergistic with colistin, substantially improving survival compared to monotherapy. Treatment with C8 significantly reduced blood bacterial density, cytokine production (tumor necrosis factor α, interleukin [IL] 6, IL-1β, and IL-10), and sepsis biomarkers. Serial in vitro passaging of A. baumannii in the presence of C8 did not cause loss of mAb binding to the bacteria, but did result in emergence of less-virulent mutants that were more susceptible to macrophage uptake. Finally, we developed a highly humanized variant of C8 that retains opsonophagocytic activity in murine and human macrophages and rescued mice from lethal infection. Conclusions: We describe a promising and novel mAb as therapy for lethal, XDR A. baumannii infections, and demonstrate that it synergistically improves outcomes in combination with antibiotics.

Background This study was performed to characterize the epidemiology, management, and outcomes of skin and soft tissue infection (SSTI) and colonization due to carbapenem-resistant Enterobacteriaceae (CRE). Methods Patients from the Consortium on Resistance Against Carbapenem in Klebsiella and Other Enterobacteriaceae (CRACKLE-1) from December 24, 2011 to October 1, 2014 with wound cultures positive for CRE were included in the study. Predictors of surgical intervention were analyzed. Molecular typing of isolates was performed using repetitive extragenic palindromic polymerase chain reaction (PCR). Carbapenemase genes were detected using PCR. Results One hundred forty-two patients were included: 62 had SSTI (44%) and 56% were colonized. Mean age was 61 years, and 48% were male: median Charlson score was 3 (interquartile range, 1–5). Forty-eight percent of patients were admitted from long-term care facilities (LTCFs), and 31% were from the community. Two strain types (ST258A and ST258B) were identified (73% of 45 tested). Carbapenemase genes were detected in 40 of 45 isolates (blaKPC-3 [47%], blaKPC-2 [42%]). Sixty-eight patients (48%) underwent surgical intervention, 63% of whom had SSTI. Patients admitted from LTCFs were less likely to undergo surgical intervention (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.18–0.71). In multivariable analysis, among patients with SSTI, those admitted from LTCFs were less likely to undergo debridement (OR, 0.18; 95% CI, 0.04–0.93). Conclusions Patients admitted from LTCFs with CRE SSTI were less likely to undergo surgical intervention. Sixteen percent of the patients died, and approximately 50% of survivors required more intensive care upon discharge. These findings suggest a unique, impactful syndrome within the CRE infection spectrum. Further studies are needed to assess the role of surgical debridement in management of CRE-SSTI, particularly among LTCF residents.

Carbapenems are a mainstay of treatment for infections caused by Pseudomonas aeruginosa. Carbapenem resistance mediated by metallo-β-lactamases (MBLs) remains uncommon in the United States, despite the worldwide emergence of this group of enzymes. Between March 2012 and May 2013, we detected MBL-producing P. aeruginosa in a university-affiliated health care system in northeast Ohio. We examined the clinical characteristics and outcomes of patients, defined the resistance determinants and structure of the genetic element harboring the blaMBL gene through genome sequencing, and typed MBL-producing P. aeruginosa isolates using pulsed-field gel electrophoresis (PFGE), repetitive sequence-based PCR (rep-PCR), and multilocus sequence typing (MLST). Seven patients were affected that were hospitalized at three community hospitals, a long-term-care facility, and a tertiary care center; one of the patients died as a result of infection. Isolates belonged to sequence type 233 (ST233) and were extensively drug resistant (XDR), including resistance to all fluoroquinolones, aminoglycosides, and β-lactams; two isolates were nonsusceptible to colistin. The blaMBL gene was identified as blaVIM-2 contained within a class 1 integron (In559), similar to the cassette array previously detected in isolates from Norway, Russia, Taiwan, and Chicago, IL. Genomic sequencing and assembly revealed that In559 was part of a novel 35-kb region that also included a Tn501-like transposon and Salmonella genomic island 2 (SGI2)-homologous sequences. This analysis of XDR strains producing VIM-2 from northeast Ohio revealed a novel recombination event between Salmonella and P. aeruginosa, heralding a new antibiotic resistance threat in this region's health care system Fil: Perez, Federico. Louis Stokes Cleveland Department of Veterans Affairs Medical Center. Cleveland; Estados Unidos. Case Western Reserve University School of Medicine. Cleveland; Estados Unidos Fil: Hujer, Andrea M.. Louis Stokes Cleveland Department of Veterans Affairs Medical Center. Cleveland; Estados Unidos. Case Western Reserve University School of Medicine. Cleveland; Estados Unidos Fil: Marshall, Steven H.. Louis Stokes Cleveland Department of Veterans Affairs Medical Center. Cleveland; Estados Unidos Fil: Ray, Amy, J.. Case Western Reserve University School of Medicine. Cleveland; Estados Unidos. University Hospitals Case Medical Center. Cleveland; Estados Unidos Fil: Rather, Philip N.. Emory University School of Medicine. Atlanta; Estados Unidos. Department of Veterans Affairs Medical Center. Decatur; Estados Unidos Fil: Suwantaratf, Nuntra. University Hospitals Case Medical Center. Cleveland; Estados Unidos Fil: Dumford III, Donald. University Hospitals Case Medical Center. Cleveland; Estados Unidos Fil: O'Shea, Patrick. Louis Stokes Cleveland Department of Veterans Affairs Medical Center. Cleveland; Estados Unidos Fil: Domitrovic, T. Nicholas J.. Louis Stokes Cleveland Department of Veterans Affairs Medical Center. Cleveland; Estados Unidos Fil: Salata, Robert A.. Case Western Reserve University School of Medicine. Cleveland; Estados Unidos. University Hospitals Case Medical Center. Cleveland; Estados Unidos Fil: Chavda, Kalyan D.. Rutgers University; Estados Unidos Fil: Chen, Liang. Rutgers University; Estados Unidos Fil: Kreiswirth, Barry N. Rutgers University; Estados Unidos Fil: Vila, Alejandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentina Fil: Haussler, Susanne. Hannover Medical School and Helmholtz Center for Infection Research; Alemania Fil: Jacobs, Michael R.. Case Western Reserve University School of Medicine. Cleveland; Estados Unidos Fil: Bonomo, Robert A.. Louis Stokes Cleveland Department of Veterans Affairs Medical Center. Cleveland; Estados Unidos. Case Western Reserve University School of Medicine. Cleveland; Estados Unidos

Background Plazomicin is a next-generation aminoglycoside with in vitro activity against multidrug-resistant Gram-negative species, including carbapenem-resistant isolates. The Consortium on Resistance Against Carbapenems in Klebsiella and other Enterobacteriaceae (CRACKLE) is a federally funded, prospective multicenter consortium of 20 hospitals from nine US healthcare systems to track carbapenem-resistant Enterobacteriaceae. Methods Minimum inhibitory concentrations (MICs) of plazomicin were determined by broth microdilution according to current CLSI guidelines against a collection of 697 carbapenem-resistant Klebsiella pneumoniae with defined carbapenem resistance mechanisms, including KPC and OXA carbapenemases. Isolates were submitted by participating CRACKLE centers. Results Carbapenemases present in study isolates included KPC-2 (n = 323), KPC-3 (n = 364), KPC-4 (n = 2), OXA-48 like (n = 7), and NDM (n = 1). Plazomicin MICs ranged from ≤0.12 to >32 mg/L, with MIC50 and MIC90 values of 0.25 and 1 mg/L, respectively (figure). MICs of 689 (98.8%) isolates were ≤4 mg/L, while MICs of the remaining eight isolates were >32 mg/L. Plazomicin MICs were related to specific carbapenemases present in isolates: of eight isolates with MICs >32 mg/L, seven contained OXA-48 like and one contained KPC-3, suggesting that these isolates possess an aminoglycoside-resistance mechanism on the same plasmid as their carbapenemase gene, such as a 16S ribosomal RNA methyltransferase, against which plazomicin is not active. Conclusion Plazomicin has good in vitro potency against a collection of carbapenemase-producing K. pneumoniae, with MIC90 value of 1 mg/L and MICs of ≤4 mg/L for 98.9% of isolates. Disclosures M. R. Jacobs, Achaogen: Investigator, Research grant. Shionogi: Investigator, Research grant. L. Connolly, Achaogen, Inc.: Consultant, Consulting fee. K. M. Krause, Achaogen: Employee, Salary. S. S. Richter, bioMerieux: Grant Investigator, Research grant. BD Diagnostics: Grant Investigator, Research grant. Roche: Grant Investigator, Research grant. Hologic: Grant Investigator, Research grant. Diasorin: Grant Investigator, Research grant. Accelerate: Grant Investigator, Research grant. Biofire: Grant Investigator, Research grant. D. Van Duin, achaogen: Scientific Advisor, Consulting fee. shionogi: Scientific Advisor, Consulting fee. Allergan: Scientific Advisor, Consulting fee. Astellas: Scientific Advisor, Consulting fee. Neumedicine: Scientific Advisor, Consulting fee. Roche: Scientific Advisor, Consulting fee. T2 Biosystems: Scientific Advisor, Consulting fee.

Background Cefiderocol is a novel siderophore cephalosporin targeted for activity against carbapenem and multidrug-resistant Gram-negative species, including extended-spectrum β-lactamase (ESBL) and carbapenemase-producing strains. The Consortium on Resistance Against Carbapenems in Klebsiella and other Enterobacteriaceae (CRACKLE) is a federally funded, prospective multi-center consortium of 20 hospitals from nine US healthcare systems to track carbapenem-resistant Enterobacteriaceae. Methods Minimum inhibitory concentrations (MICs) of cefiderocol and meropenem were determined by broth microdilution according to current CLSI guidelines. Cefiderocol was tested in iron-depleted cation-adjusted Mueller–Hinton (MH) broth, meropenem was tested in cation-adjusted MH broth. Cefiderocol MICs were read as the first drug well in which the growth was significantly reduced (i.e., a button of Results Cefiderocol MICs ranged from ≤0.03 to >64 mg/L, with overall MIC50 of 0.5 mg/L and MIC90 of 4 mg/L (table). MIC90 value (≤0.03 mg/L) was lowest against isolates with no ESBLs or carbapenemases. MIC90 was 1 mg/L for OXA and TEM/SHV groups, 2–4 mg/L for KPC-3 groups and 8 mg/L for NDM and KPC-2 groups. Conclusion Compared with isolates without ESBLs and carbapenemases, cefiderocol shows higher MICs against isolates with ESBLs, including TEM, SHV, and CTX-M and carbapenemases including KPC, NDM, and OXA. The clinical utility of cefiderocol against ESBL and carbapenemase-producing Enterobacteriaceae is dependent on the pharmacokinetic and pharmacodynamic properties of cefiderocol. Disclosures M. R. Jacobs, Achaogen: Investigator, Research grant. Shionogi: Investigator, Research grant. S. S. Richter, bioMerieux: Grant Investigator, Research grant. BD Diagnostics: Grant Investigator, Research grant. Roche: Grant Investigator, Research grant. Hologic: Grant Investigator, Research grant. Diasorin: Grant Investigator, Research grant. Accelerate: Grant Investigator, Research grant. Biofire: Grant Investigator, Research grant. D. Van Duin, Shionogi: Scientific Advisor, Consulting fee. achaogen: Scientific Advisor, Consulting fee. Allergan: Scientific Advisor, Consulting fee. Astellas: Scientific Advisor, Consulting fee. Neumedicine: Consultant, Consulting fee. T2 Biosystems: Scientific Advisor, Consulting fee. Roche: Scientific Advisor, Consulting fee.

Background AmpC producing Ent are an important cause of multidrug-resistant (MDR) infections in pediatrics. Since most AmpC Ent studies have been conducted in adults, we characterized the molecular epidemiology of AmpC Ent strains with transmissible resistance and identified factors associated with AmpC Ent infections in children. Methods A case–control study of children (0–18 years) at 4 Chicago hospitals during 2011–18 was performed. Cases were 44 children with infections due to Ent harboring an AmpC as detected by DNA microarray (Check-Points®). PCR, DNA sequencing, MLST, and phylogenetic analyses were performed. Controls (ctrls) were 132 children with expanded-spectrum cephalosporin-susceptible Ent infections matched by age and hospital. Demographics; residence; comorbidities; device, antibiotic, and healthcare exposures were evaluated. Predictors of AmpC Ent infection were assessed by logistic regression. Results The median age of AmpC Ent patients was 3.0 years; 50% were male. Of blaAmpC genes, 68% were blaACT/MIR-type and 25% blaCMY-type. Predominant organisms were Enterobacter cloacae (59%) and Escherichia coli (32%); 27% of AmpC E. cloacae belonged to ST114 and 62% co-harbored a blaESBL gene, predominately blaSHV (94%). Most AmpC E. coli strains were unrelated; 71% carried blaCMY, 64% belonged to phylogroups B2/D, and 50% co-harbored blaCTX-M. On bivariate analysis vs. ctrls, AmpC Ent infections were more likely to be respiratory (39% vs. 18%, P < 0.01) and less likely to be urinary tract (41% vs. 67%, P < 0.01) or community-acquired (14% vs. 33%, P < 0.02). By multivariable analysis, children with AmpC Ent infections were more likely to be nonwhite, non-black, non-Hispanic (OR 4.7, CI 1.4–16.1) and have infections due to Enterobacter (OR 7.7, CI 3.5–17). Differences in gender, healthcare location, residential neighborhood, antibiotic exposures, comorbidities, devices or outcomes were not found. Conclusion AmpC Ent infections often had healthcare onset, were due to Enterobacter, and occurred in nonwhite, non-black, non-Hispanic children. AmpC Ent commonly co-harbored blaSHV and blaCTX-M ESBL genes which affects therapeutic options and suggests the need for contact precautions. Control of AmpC Ent infections in children will require validating sources and risk factors. Disclosures All authors: No reported disclosures.

During an investigation of potential sources of transmission of multidrug-resistant gram-negative bacilli on a spinal cord injury unit, we recovered genetically related carbapenem-resistant Acinetobacter baumannii isolates from the stool of 3 patients, the hands of a nurse, and an ice machine water outlet spout and drain. Our findings suggest that contaminated ice machines could serve as a potential reservoir for dissemination of multidrug-resistant gram-negative bacilli.

Background This study was performed to characterize the epidemiology, management, and outcomes of skin and soft tissue infection (SSTI) and colonization due to carbapenem-resistant Enterobacteriaceae (CRE). Methods Patients from the Consortium on Resistance Against Carbapenem in Klebsiella and Other Enterobacteriaceae (CRACKLE-1) from December 24, 2011 to October 1, 2014 with wound cultures positive for CRE were included in the study. Predictors of surgical intervention were analyzed. Molecular typing of isolates was performed using repetitive extragenic palindromic polymerase chain reaction (PCR). Carbapenemase genes were detected using PCR. Results One hundred forty-two patients were included: 62 had SSTI (44%) and 56% were colonized. Mean age was 61 years, and 48% were male: median Charlson score was 3 (interquartile range, 1–5). Forty-eight percent of patients were admitted from long-term care facilities (LTCFs), and 31% were from the community. Two strain types (ST258A and ST258B) were identified (73% of 45 tested). Carbapenemase genes were detected in 40 of 45 isolates (blaKPC-3 [47%], blaKPC-2 [42%]). Sixty-eight patients (48%) underwent surgical intervention, 63% of whom had SSTI. Patients admitted from LTCFs were less likely to undergo surgical intervention (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.18–0.71). In multivariable analysis, among patients with SSTI, those admitted from LTCFs were less likely to undergo debridement (OR, 0.18; 95% CI, 0.04–0.93). Conclusions Patients admitted from LTCFs with CRE SSTI were less likely to undergo surgical intervention. Sixteen percent of the patients died, and approximately 50% of survivors required more intensive care upon discharge. These findings suggest a unique, impactful syndrome within the CRE infection spectrum. Further studies are needed to assess the role of surgical debridement in management of CRE-SSTI, particularly among LTCF residents.

Among Gram-negative bacteria, carbapenem-resistant infections pose a serious and life-threatening challenge. Here, the CRACKLE network reports a sentinel detection and characterization of a carbapenem-resistant Klebsiella pneumoniae ST147 isolate harboring bla NDM-5 and bla OXA-181 from a young man who underwent abdominal surgery in India. bla NDM-5 was located on an IncFII plasmid of ≈90 kb, whereas bla OXA-181 was chromosomally encoded. Resistome and genome analysis demonstrated multiple copies of the transposable element IS 26 and a “hot-spot region” in the IncFII plasmid.

The widespread dissemination of carbapenem-resistant Acinetobacter spp. has created significant therapeutic challenges. At present, rapid molecular diagnostics (RMDs) that can identify this phenotype are not commercially available. Two RMD platforms, PCR combined with electrospray ionization mass spectrometry (PCR/ESI-MS) and molecular beacons (MB), for detecting genes conferring resistance/susceptibility to carbapenems in Acinetobacter spp. were evaluated. An archived collection of 200 clinical Acinetobacter sp. isolates was tested. Predictive values for susceptibility and resistance were estimated as a function of susceptibility prevalence and were based on the absence or presence of beta-lactamase ( bla ) NDM, VIM, IMP, KPC, and OXA carbapenemase genes (e.g., bla OXA-23 , bla OXA-24/40 , and bla OXA-58 found in this study) against the reference standard of MIC determinations. According to the interpretation of MICs, 49% ( n = 98) of the isolates were carbapenem resistant (as defined by either resistance or intermediate resistance to imipenem). The susceptibility sensitivities (95% confidence interval [CI]) for imipenem were 82% (74%, 89%) and 92% (85%, 97%) for PCR/ESI-MS and MB, respectively. Resistance sensitivities (95% CI) for imipenem were 95% (88%, 98%) and 88% (80%, 94%) for PCR/ESI-MS and MB, respectively. PRIMERS III establishes that RMDs can discriminate between carbapenem resistance and susceptibility in Acinetobacter spp. In the context of a known prevalence of resistance, SPVs and RPVs can inform clinicians regarding the best choice for empiric antimicrobial therapy against this multidrug-resistant pathogen.

A rare case of MDR P. aeruginosa causing PVE is analyzed at the genetic level with the goal of understanding acquired resistance mechanisms. The molecular basis of evolving antibiotic resistance gives clinicians insight into the nature of persistent P. aeruginosa infections., Background. Successful treatment of infections caused by multidrug-resistant (MDR) Pseudomonas aeruginosa is thwarted by the emergence of antibiotic resistance and biofilm formation on prosthetic devices. Our aims were to decipher the molecular basis of resistance in a unique case of prosthetic valve endocarditis (PVE) caused by MDR P. aeruginosa. Methods. Five sequential MDR P. aeruginosa blood isolates collected during a 7-month period were recovered from a patient suffering from PVE previously exposed to β-lactam antibiotics. Minimum inhibitory concentrations (MICs) of several classes of antibiotics were used to indicate clinical resistance characteristics; relatedness of the isolates was determined using multilocus sequence typing and repetitive sequence-based polymerase chain reaction. Amplification and sequencing of regulatory and resistance genes was performed. Results. All isolates belonged to ST 298, possessed bla PDC-16, and were resistant to fluoroquinolones and carbapenems. In the course of therapy, we observed a >2-fold increase in cephalosporin resistance (4 µg/mL to >16 µg/mL). Sequencing of the AmpC regulator, ampR, revealed a D135N point mutation in cephalosporin-resistant isolates. Common carbapenemase genes were not identified. All isolates demonstrated a premature stop codon at amino acid 79 of the outer membrane protein OprD and mutations in the quinolone resistance-determining regions of gyrA and parC. Point mutations in nalC, an efflux pump regulator, were also observed. Conclusions. In this analysis, we chart the molecular evolution of β-lactam resistance in a case of PVE. We show that mutations in regulatory genes controlling efflux and cephalosporinase production contributed to the MDR phenotype.

Multidrug-resistant (MDR) Enterobacteriaceae infections are increasing in U.S. children; however, there is a paucity of multicentered analyses of antibiotic resistance genes responsible for MDR phenotypes among pediatric Enterobacteriaceae isolates. In this study, 225 isolates phenotypically identified as extended-spectrum β-lactamase (ESBL) or carbapenemase producers, recovered from children ages 0 to 18 years hospitalized between January 2011 and April 2015 at three Chicago area hospitals, were analyzed. We used DNA microarray platforms to detect ESBL, plasmid-mediated AmpC (pAmpC), and carbapenemase type β-lactamase ( bla ) genes. Repetitive-sequence-based PCR and multilocus sequence typing (MLST) were performed to assess isolate similarity. Plasmid replicon typing was conducted to classify plasmids. The median patient age was 4.2 years, 56% were female, and 44% presented in the outpatient setting. The majority (60.9%) of isolates were Escherichia coli and from urinary sources (69.8%). Of 225 isolates exhibiting ESBL- or carbapenemase-producing phenotypes, 90.7% contained a bla gene. The most common genotype was the bla CTX-M-1 group (49.8%); 1.8% were carbapenem-resistant Enterobacteriaceae (three bla KPC and one bla IMP ). Overall, pAmpC ( bla ACT/MIR and bla CMY ) were present in 14.2%. The predominant E. coli phylogenetic group was the virulent B2 group (67.6%) associated with ST43/ST131 (Pasteur/Achtman MLST scheme) containing the bla CTX-M-1 group (84%), and plasmid replicon types FIA, FII, and FIB. K. pneumoniae harboring bla KPC were non-ST258 with replicon types I1 and A/C. Enterobacter spp. carrying bla ACT/MIR contained plasmid replicon FIIA. We found that β-lactam resistance in children is diverse and that certain resistance mechanisms differ from known circulating genotypes in adults in an endemic area. The potential impact of complex molecular types and the silent dissemination of MDR Enterobacteriaceae in a vulnerable population needs to be studied further.

Background There is an increasing incidence of extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae infections in children. However, most studies focus only on CTX-M-1 group (CTX-M-15). We sought to define the epidemiology of the CTX-M-9 group (CTX-M-9) producing Enterobacteriaceae infections in children to devise more effective treatment and prevention strategies. Methods A case–control study of children (0–21 y), cared for by 3 Chicago area hospitals during 2011–16, was performed. Cases were 44 children diagnosed with third-generation cephalosporin (3GC) resistant and/or carbapenem-resistant (CR) Enterobacteriaceae infections who had CTX-M-9 genes accounting for β-lactam resistance. PCR amplification, DNA sequencing, and DNA microarray analysis (Check-Points®) assessed for bla genes. MLST, rep-PCR and phylogenetic analysis were also performed. Controls were 135 children with 3GC and carbapenem susceptible Enterobacteriaceae infections matched by age range and hospital. Demographics; comorbidities; device, antibiotic, and healthcare exposures; and the impact of location of patient residence were evaluated. Race categories were white, black, Hispanic, and other. Stratified analysis and multivariable logistic regression were used to explore associations between predictors and CTX-M-9 infection. Data were analyzed in SAS 9.4. Results The median age of cases was 4.1 years. The predominant organism (39/44, 89%) was E. coli of virulent phylogroups B2 (41%) and D (59%). MLST analysis revealed that this collection of strains was polyclonal. On multivariable analysis, children with CTX-M-9 Enterobacteriaceae infections were more likely to be diagnosed in an outpatient clinic (OR 4.5), have E. coli infection (OR 7.0), and be of race “other” (OR 7.6) vs. controls. Residents of South Chicago were 6.7 times more likely to have a CTX-M-9 Enterobacteriaceae infection than controls; while residence in Northwest Chicago was associated with a 81% decreased risk. Significant differences in other demographics, comorbidities, invasive devices, antibiotic use, or recent healthcare were not found. Conclusion We observed striking regional differences in occurrence of CTX-M-9 producing Enterobacteriaceae, suggesting that environmental influences and plasmid transfer may contribute to acquisition. It is worrisome that a large number of ESBL Enterobacteriaceae strains bearing CTX-M ESBLs circulate in the community among children. Disclosures All authors: No reported disclosures.

Background: Polymyxins including colistin are an important "last-line" treatment for infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKp). Increasing use of colistin has led to resistance to this cationic antimicrobial peptide. Methods: A cohort nested within the Consortium on Resistance against Carbapenems in Klebsiella pneumoniae (CRACKLE) was constructed of patients with infection, or colonization with CRKp isolates tested for colistin susceptibility during the study period of December, 2011 to October, 2014. Reference colistin resistance determination as performed by broth macrodilution was compared to results from clinical microbiology laboratories (Etest) and to polymyxin resistance testing. Each patient was included once, at the time of their first colistin-tested CRKp positive culture. Time to 30-day in-hospital all-cause mortality was evaluated by Kaplan-Meier curves and Cox proportional hazard modeling. Results: In 246 patients with CRKp, 13% possessed ColR CRKp. ColR was underestimated by Etest (very major error rate = 35%, major error rate = 0.4%). A variety of rep-PCR strain types were encountered in both the ColS and the ColR groups. Carbapenem resistance was mediated primarily by blaKPC-2 (46%) and blaKPC-3 (50%). ColR was associated with increased hazard for in-hospital mortality (aHR 3.48; 95% confidence interval, 1.73-6.57; P < .001). The plasmid-associated ColR genes, mcr-1 and mcr-2 were not detected in any of the ColR CRKp. Conclusions: In this cohort, 13% of patients with CRKp presented with ColR CRKp. The apparent polyclonal nature of the isolates suggests de novo emergence of ColR in this cohort as the primary factor driving ColR. Importantly, mortality was increased in patients with ColR isolates.

Pseudomonas aeruginosa is a notoriously difficult-to-treat pathogen that is a common cause of severe nosocomial infections. Investigating a collection of β-lactam-resistant P. aeruginosa clinical isolates from a decade ago, we uncovered resistance to ceftazidime-avibactam, a novel β-lactam/β-lactamase inhibitor combination. The isolates were systematically analyzed through a variety of genetic, biochemical, genomic, and microbiological methods to understand how resistance manifests to a unique drug combination that is not yet clinically released. We discovered that avibactam was able to inactivate different AmpC β-lactamase enzymes and that bla PDC regulatory elements and penicillin-binding protein differences did not contribute in a major way to resistance. By using carefully selected combinations of antimicrobial agents, we deduced that the greatest barrier to ceftazidime-avibactam is membrane permeability and drug efflux. To overcome the constellation of resistance determinants, we show that a combination of antimicrobial agents (ceftazidime/avibactam/fosfomycin) targeting multiple cell wall synthetic pathways can restore susceptibility. In P. aeruginosa , efflux, as a general mechanism of resistance, may pose the greatest challenge to future antibiotic development. Our unexpected findings create concern that even the development of antimicrobial agents targeted for the treatment of multidrug-resistant bacteria may encounter clinically important resistance. Antibiotic therapy in the future must consider these factors.

Background KPC-CRE are multidrug-resistant organisms (MDRO) associated with morbidity and mortality worldwide. KPC-CRE infection prevalence is increasing in the pediatric population; however, multi-centered pediatric data are lacking. We sought to identify factors for KPC-CRE infections in children and to classify genotypes of infecting strains. Methods We conducted a case–case–control study of patients (0–22 years) at 3 tertiary care medical centers in Chicago, 2008–2015. Case group 1 were children identified with KPC-CRE infections; case group 2 possessed carbapenem-susceptible Enterobacteriaceae (CSE) infections; controls (ctrls) were patients with completely negative cultures. Cases were matched to ctrls 1:1:3 by age, infection site, and hospital. Bivariate and stratified statistical analyses were performed. Molecular analysis was conducted on available isolates. Results We identified 18 KPC-CRE infections. Of 4 KPC-CRE available for molecular analysis, 3 were non-ST258 strains harboring blaKPC-2; no strains were related. Median age of KPC-CRE patients 16 (1–22) years. Differences in race, gender, LOS, and mortality were not significant. KPC-CRE and CSE infected patients were more likely to have prior MDRO (KPC-CRE 95%, CSE 11%, Ctrl 0%), long-term care facility admission (KPC-CRE 21%, CSE 17%, Ctrl 0%), and LOS >7 days before culture. Both KPC-CRE and CSE more likely had gastrointestinal (GI) comorbidities (OR: 21.9, KPC-CRE; 6.9, CSE) and >3 comorbidities (OR: 12.0, KPC-CRE; 3.5, CSE) compared with ctrls; however only KPC-CRE patients had more pulmonary and neurologic comorbidities (ORs 5.4 and 4.6), or GI and pulmonary devices (ORs 9.3 and 5.3). Compared with ctrls, CSE patients more often had prior fluoroquinolone use (OR 7.4), while KPC-CRE patients were more likely exposed to carbapenems or aminoglycosides (ORs 9.1 and 7.1). Conclusion In these children, factors associated with KPC-CRE infection reveal a high burden of disease and included pulmonary and neurologic comorbidities, GI and pulmonary devices, or exposure to carbapenems and aminoglycosides. Non-ST258 KPC-CRE strains were more common, and LOS and mortality rates were similar in all groups, which differs from adult reports. Control of CRE in children should focus on validating and mitigating these risk factors. Disclosures A. H. Bartlett, CVS Caremark: Consultant, Consulting fee; R. A. Bonomo, Merck: Grant Investigator, Research support; Allergan: Investigator, Research support; Wokhardt: Investigator, Research support; Glaxo Smith Kline: Investigator, Research support; Astra Zeneca: Investigator, Research support; Actavis: Speaker’s Bureau, Speaker honorarium

Volume 55, no. 1, p. 134–144, 2017, [https://doi.org/10.1128/JCM.01524-16][1]. Table S1 in the supplemental material: Isolates PR-369 and PR-469 were mislabeled, and a column containing an alternate list of isolate names (ARLG IDs) was inadvertently omitted. Revised supplemental material is posted

An increase in the number of infections with fluoroquinolone (FQ)-resistant Escherichia coli following transrectal ultrasound-guided biopsy of the prostate (TRUBP) was observed in Louis Stokes Cleveland Department of Veterans Affairs Medical Center. This study investigated whether these infections were caused by a single strain of E. coli possessing distinct resistance and virulence determinants. Of 15 patients with urinary tract infection, 5 were complicated with bacteraemia and 1 with prostate abscess. Thirteen FQ-resistant isolates demonstrated mutations in the quinolone resistance-determining regions (QRDRs) of gyrA and parC but did not contain plasmid-mediated quinolone resistance determinants; blaCTX-M and blaCMY as well as genes coding for extended-spectrum β-lactamases were also absent. Genes encoding aminoglycoside-modifying enzymes were discovered in an isolate that was gentamicin-resistant. The most prevalent sequence type (ST) was ST43 (n = 7), corresponding to ST131 in Achtman's multilocus sequence typing (MLST) scheme. These isolates (i) were distinguished as >95% similar by repetitive sequence-based PCR (rep-PCR), (ii) belonged to the virulent phylogenetic group B2 and (iii) contained plasmid types FIB, FIA and Frep. Several other strain types were present (ST2, ST27, ST30, ST44, ST472, ST494, ST511 and ST627). Non-ST43 isolates infected patients with more co-morbidities but contained similar virulence factors (kpsMTII, iutA, papAH/papC and sfa/focDE). In our hospital, E. coli isolates causing TRUBP-related infection are quite heterogeneous (ST131 and other ST types) and are part of phylogenetic groups containing multiple virulence factors.

Background ESBL Ent infections are increasingly prevalent in the pediatric population; however, most ESBL Ent studies have focused on adults and/or CTX-M-type strains. We sought to characterize the molecular epidemiology of ESBL Ent strains and to identify factors associated with TEM- and SHV-type ESBL Ent (TEMSHV Ent) infections in children. Methods A case–control study of children (0–18 years) cared for by 3 Chicago hospitals during 2011–2016 was performed. Cases were 38 children with infections due to Ent harboring a lone TEM- or SHV-type ESBL as detected by DNA microarray (Check-Points®). PCR, DNA sequencing, Rep-PCR, plasmid typing, and phylogenetic grouping were also performed. Controls (ctrls) were 137 children with third-generation cephalosporin susceptible Ent infections matched by age and hospital. Demographics; patient residence; comorbidities; device, antibiotic, and healthcare exposures were evaluated. Bivariate and multivariable logistic regression analyses explored associations between predictors and TEMSHV Ent infection. Results Of 38 TEMSHV Ent infections, 74% were SHV-type and 26% TEM-type. The median age of TEMSHV Ent patients was 4.3 (0–17.9) years. Predominant organisms were Klebsiella spp. (34.2%) and E. coli (31.6%); 67% of E. coli were phylogroup B2. Most strains were unrelated; 47% were MDRO. On bivariate analysis, TEMSHV Ent patients were more likely to be male (53% vs. 34%, P = 0.04), have longer LOS after infection (35d vs. 14d, P < 0.001) but no difference in mortality, and have less UTIs (53% vs. 75%, P = 0.01) than ctrls. On multivariable analysis, children with TEMSHV Ent infections more often had recent inpatient care (OR 8.2), yet were diagnosed more frequently as outpatients (OR 25.6) and less often in NICUs (OR 0.036) than ctrls. TEMSHV Ent patients had more gastrointestinal (GI) (OR 23.7) and renal comorbidities (OR 4.2) vs. ctrls. Differences in race, gender, residential neighborhood, antibiotic exposure, and foreign bodies were not significant after controlling for other factors. Conclusion In children, factors associated with TEMSHV Ent infections include recent inpatient care and GI and renal comorbidities. Infections are associated with longer LOS but not greater mortality. Control of TEMSHV Ent infections in children should focus on validating and responding to these risk factors. Disclosures M. K. Hayden, Sage, Inc: Sage is contributing product to healthcare facilities participating in a regional collaborative on which I am a co-investigator. Neither I nor my hospital receive product., Sage is contributing product to healthcare facilities participating in a regional collaborative on which I am a co-investigator. Neither I nor my hospital receive product.; Clorox, Inc.: I have received funding from Clorox for an investigator-initiated clinical trial., Research support; CDC: Grant Investigator, Research grant; OpGen: receipt of in kind laboratory services, Research support; R. A. Bonomo, Merck: Grant Investigator and Investigator, Consulting fee and Research support; Allergan: Grant Investigator, Research support; Wockhardt: Grant Investigator, Research support; Glaxo Smith Kline: Grant Investigator, Research support; Astra Zeneca: Grant Investigator, Research support; Actavis: Speaker’s Bureau, Speaker honorarium