Impact of COVID-19 pandemic on carbapenem-resistant Enterobacterales incidence in the South-East Asia region: an observational study.

The COVID-19 pandemic led to an initial increase in the incidence of carbapenem-resistant Enterobacterales (CRE) from clinical cultures in South-East Asia hospitals, which was unsustained as the pandemic progressed. Conversely, there was a decrease in CRE incidence from surveillance cultures and overall combined incidence. Further studies are needed for future pandemic preparedness.

Evaluation of NG-Test CARBA 5 version 2, Cepheid Xpert Carba-R, and carbapenem inactivation methods in comparison to whole-genome sequencing for the identification of carbapenemases in non-fermenting Gram-negative bacilli.

NG-Test CARBA 5 (NG-Biotech) is a rapid in vitro multiplex immunoassay for the phenotypic detection and differentiation of the "big five" carbapenemase families (KPC, OXA-48-like, VIM, IMP, and NDM). Version 2 of this assay was evaluated alongside the Xpert Carba-R assay (Cepheid, Inc.), the modified carbapenem inactivation method (mCIM), and the CIMTris assay, with a collection of carbapenem-resistant non-fermenting Gram-negative bacilli comprising 138 Pseudomonas aeruginosa and 97 Acinetobacter baumannii isolates. Whole-genome sequencing (WGS) was used as the reference standard. For P. aeruginosa, NG-Test CARBA 5 produced an overall percentage agreement (OPA) with WGS of 97.1%, compared with 92.8% forXpert Carba-R and 90.6% for mCIM. For A. baumannii, as OXA-type carbapenemases (non-OXA-48) are not included, both the NG-Test CARBA 5 and Xpert Carba-R only had an OPA of 6.2%, while the CIMTris performed well with an OPA of 99.0%. The majority of A. baumannii isolates (95.9%) tested falsely positive for IMP on NG-Test CARBA 5; no IMP genes were found on WGS. No clear cause was found for this phenomenon; a cross-reacting protein antigen unique to A. baumannii is a possible culprit. NG-Test CARBA 5 performed well for carbapenemase detection in P. aeruginosa. However, results from A. baumannii isolates should be interpreted with caution.

Rapid Screening of Urinary Tract Infection Using Microfluidic Inertial-Impedance Cytometry.

Urinary tract infection (UTI) diagnosis based on urine culture for bacteriuria analysis is time-consuming and often leads to wastage of hospital resources due to false-positive UTI cases. Direct cellular phenotyping (e.g., RBCs, neutrophils, epithelial cells) of urine samples remains a technical challenge as low cell concentrations, and urine characteristics (conductivities, pH, microbes) can affect the accuracy of cell measurements. In this work, we report a microfluidic inertial-impedance cytometry technique for label-free rapid (<5 min) neutrophil sorting and impedance profiling from urine directly. Based on size-based inertial focusing effects, neutrophils are isolated, concentrated, and resuspended in saline (buffer exchange) to improve consistency in impedance-based single-cell analysis. We first observed that both urine pH and the presence of bacteria can affect neutrophil high-frequency impedance measurements possibly due to changes in nucleus morphology as neutrophils undergo NETosis and phagocytosis, respectively. As a proof-of-concept for clinical testing, we report for the first time, rapid UTI testing based on multiparametric impedance profiling of putative neutrophils (electrical size, membrane properties, and distribution) in urine samples from non-UTI (n = 20) and UTI patients (n = 20). A significant increase in cell count was observed in UTI samples, and biophysical parameters were used to develop a UTI classifier with an area under the receiver operating characteristic curve of 0.84. Overall, the developed platform facilitates rapid culture-free urine screening which can be further developed to assess disease severity in UTI and other urologic diseases based on neutrophil electrical signatures.

Dissemination of Pseudomonas aeruginosa blaNDM-1-Positive ST308 Clone in Singapore.

Pseudomonas aeruginosa ST308 clone has been reported to carry carbapenemase genes such as blaIMP and blaVIM but has been rarely associated with blaNDM-1. A total of 199 P. aeruginosa ST308 clinical and environmental isolates obtained between April 2019 and November 2020 from a tertiary-care hospital in Singapore were characterized using whole-genome sequencing. In addition, 71 blaNDM-1-positive ST308 whole-genome sequences from two other local tertiary-care hospitals in Singapore and 83 global blaNDM-1-negative ST308 whole-genome sequences in public databases were included to assess phylogenetic relationships and perform genome analyses. Phylogenetic analysis and divergent time estimation revealed that blaNDM-1-positive P. aeruginosa ST308 was introduced into Singapore in 2005 (95 % highest posterior density: 2001 to 2008). Core genome, resistome, and analyses of all local blaNDM-1-positive ST308 isolates showed chromosomal integration of multiple antibiotic resistance genes (ARGs) [aac(3)-Id, aac(6')-Il, aadA6, aadA11, dfrB5, msr(E), floR, sul2, and qnrVC1], which was absent in global blaNDM-1-negative ST308 sequences. Most ARGs and virulence genes were conserved across isolates originating from the three different local hospitals. Close genetic relatedness of the blaNDM-1-positive ST308 clinical and environmental isolates suggests cocirculation between the hospital environment and human hosts with the hospital environment as a potential reservoir. Core genome single nucleotide polymorphism analyses revealed possible clonal transmission of blaNDM-1-positive ST308 isolates between the three hospitals over 7 years. Bloodstream isolates accounted for six of 95 (6.3%) clinical isolates. This study reports the introduction of a pathogenic blaNDM-1-positive P. aeruginosa ST308 more than a decade ago in Singapore and warrants surveillance for wider dissemination. IMPORTANCE P. aeruginosa is a Gram-negative opportunistic pathogen ubiquitously found in the environment and a major cause of nosocomial infections. While the P. aeruginosa ST308 clone has been known to bear blaIMP and blaVIM among global isolates, reports of blaNDM-1-positive P. aeruginosa ST308 are rare. The local blaNDM-1-positive P. aeruginosa ST308 isolates detected in this study appear to be unique to this region, with evidence of chromosomal acquisition of multiple ARGs compared to global blaNDM-1-negative P. aeruginosa ST308 isolates. Surveillance in Singapore and beyond for dissemination is essential to determine whether existing measures are sufficient to control the spread of this ST308 clone.

Genomic surveillance uncovers ongoing transmission of carbapenem-resistant Acinetobacter baumannii (CRAB) and identifies actionable routes of transmissions in an endemic setting.

OBJECTIVE: In our center, previous infection prevention and control (IPC) resources were concentrated on multidrug-resistant organisms other than CRAB because the rate of CRAB was stable with no evidence of outbreaks. Triggered by an increase in the baseline rate of CRAB isolated in clinical cultures, we investigated horizontal transmission of CRAB to guide targeted IPC actions. METHODS: We prospectively collected clinical data of patients with positive CRAB cultures. We identified genetic relatedness of CRAB isolates using whole-genome sequencing. Findings were regularly presented to the IPC committee, and follow-up actions were documented. RESULTS: During the study period, 66 CRAB isolates were available for WGS. Including 12 clinical isolates and 10 environmental isolates from a previous study, a total of 88 samples were subjected to WGS, of which 83 were successfully sequenced and included in the phylogenetic analysis. We identified 5 clusters involving 44 patients. Genomic transmissions were explained by spatiotemporal overlap in 12 patients and by spatial overlap only in 12 patients. The focus of transmission was deduced to be the intensive care units. One cluster was related to a retrospective environmental isolate, suggesting the environment as a possible route of transmission. Discussion of these findings at multidisciplinary IPC meetings led to implementation of measures focusing on environmental hygiene, including hydrogen peroxide vapor disinfection in addition to terminal cleaning for rooms occupied by CRAB patients. CONCLUSIONS: We showed that WGS could be utilized as a "tool of persuasion" by demonstrating the presence of ongoing transmission of CRAB in an endemic setting, and by identifying actionable routes of transmission for directed IPC interventions.

Whole genome sequencing reveals hidden transmission of carbapenemase-producing Enterobacterales.

Carbapenemase-producing Enterobacterales (CPE) infection control practices are based on the paradigm that detected carriers in the hospital transmit to other patients who stay in the same ward. The role of plasmid-mediated transmission at population level remains largely unknown. In this retrospective cohort study over 4.7 years involving all multi-disciplinary public hospitals in Singapore, we analysed 779 patients who acquired CPE (1215 CPE isolates) detected by clinical or surveillance cultures. 42.0% met putative clonal transmission criteria, 44.8% met putative plasmid-mediated transmission criteria and 13.2% were unlinked. Only putative clonal transmissions associated with direct ward contact decreased in the second half of the study. Both putative clonal and plasmid-mediated transmission associated with indirect (no temporal overlap in patients' admission period) ward and hospital contact did not decrease during the study period. Indirect ward and hospital contact were identified as independent risk factors associated with clonal transmission. In conclusion, undetected CPE reservoirs continue to evade hospital infection prevention measures. New measures are needed to address plasmid-mediated transmission, which accounted for 50% of CPE dissemination.

Accuracy of a Rapid Multiplex Polymerase Chain Reaction Plus a Chromogenic Phenotypic Test Algorithm for Detection of Extended-Spectrum ß-Lactamase and Carbapenemase-Producing Gram-Negative Bacilli in Positive Blood Culture Bottles.

We studied the performance of an algorithm combining multiplex polymerase chain reaction with phenotypic detection of extended-spectrum ß-lactamases and carbapenemases directly from positive blood culture bottles in patients with gram-negative bacteremia and found good concordance with routine cultures. Such an algorithm may be a tool to improve time to optimal therapy in patients with gram-negative bacteremia.

Mixed-charge pseudo-zwitterionic copolymer brush as broad spectrum antibiofilm coating.

Zwitterionic polymers are classical antifouling polymers but they require specialized monomers that have cationic and anionic charges integrated into a single monomer. Herein, we show that pseudo-zwitterionic copolymers synthesized from a mixture of 2 monomers each having a single opposite polarity has excellent antibiofilm efficacy. We have discovered a new mixed-charge copolymer brush (#1-A) synthesized from 2 oppositely charged monomers, the anionic SPM (3-Sulfopropyl methacrylate) and the cationic AMPTMA ((3-Acrylamidopropyl) trimethylammonium chloride), that achieves broad spectrum in vitro antibiofilm effect of greater than 99% reductions against all six Gram-positive and Gram-negative bacteria tested. In the murine subcutaneous wound catheter infection models, the #1-A has good long-term anti-biofilm efficacy against MRSA and Pseudomonas aeruginosa of 3.41 and 3.19 orders respectively, outperforming previous mixed-charge copolymer coatings. We discovered a new method to choose the cationic/anionic pair combination to form the best antibiofilm copolymer brush coating by exploiting the solution polymerization kinetics disparity between the cationic and anionic monomers. We also showed that #1-A is softer and has higher hydration than the classical zwitterionic polymer. This study shows the possibility of achieving potent antibiofilm efficacy by combining readily available opposite singly charged monomers.

Antimicrobial Effect of a Novel Chitosan Derivative and Its Synergistic Effect with Antibiotics.

Cationic polymers are promising antibacterial agents because bacteria have a low propensity to develop resistance against them, but they usually have low biocompatibility because of their hydrophobic moieties. Herein, we report a new biodegradable and biocompatible chitosan-derived cationic antibacterial polymer, 2,6-diamino chitosan (2,6-DAC). 2,6-DAC shows excellent broad-spectrum antimicrobial activity with minimum inhibitory concentrations (MICs) of 8-32 µg/mL against clinically relevant and multidrug-resistant (MDR) bacteria including Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Furthermore, 2,6-DAC shows an excellent synergistic effect with various clinically relevant antibiotics proved by decreasing the MICs of the antibiotics against MDR A. baumannii and methicillin-resistant Staphylococcus aureus to <1 µg/mL. In vivo biocompatibility of 2,6-DAC is proved by a dosage of 100 mg/kg compound via oral administration and 25 mg/kg compound via intraperitoneal injection to mice; 2,6-DAC does not cause any weight loss and any significant change in liver and kidney biomarkers or the important blood electrolytes. The combinations of 2,6-DAC together with novobiocin and rifampicin show >2.4 log10 reduction of A. baumannii in murine intraperitoneal and lung infection models. The novel chitosan derivative, 2,6-DAC, can be utilized as a biocompatible broad-spectrum cationic antimicrobial agent alone or in synergistic combination with various antibiotics.

Precisely Structured Nitric-Oxide-Releasing Copolymer Brush Defeats Broad-Spectrum Catheter-Associated Biofilm Infections In Vivo.

Gram-negative bacteria cannot be easily eradicated by antibiotics and are a major source of recalcitrant infections of indwelling medical devices. Among various device-associated infections, intravascular catheter infection is a leading cause of mortality. Prior approaches to surface modification, such as antibiotics impregnation, hydrophilization, unstructured NO-releasing, etc., have failed to achieve adequate infection-resistant coatings. We report a precision-structured diblock copolymer brush (H(N)-b-S) composed of a surface antifouling block of poly(sulfobetaine methacrylate) (S) and a subsurface bactericidal block (H(N)) of nitric-oxide-emitting functionalized poly(hydroxyethyl methacrylate) (H) covalently grafted from the inner and outer surfaces of a polyurethane catheter. The block copolymer architecture of the coating is important for achieving good broad-spectrum anti-biofilm activity with good biocompatibility and low fouling. The coating procedure is scalable to clinically useful catheter lengths. Only the block copolymer brush coating ((H(N)-b-S)) shows unprecedented, above 99.99%, in vitro biofilm inhibition of Gram-positive and Gram-negative bacteria, 100-fold better than previous coatings. It has negligible toxicity toward mammalian cells and excellent blood compatibility. In a murine subcutaneous infection model, it achieves >99.99% biofilm reduction of Gram-positive and Gram-negative bacteria compared with <90% for silver catheter, while in a porcine central venous catheter infection model, it achieves >99.99% reduction of MRSA with 5-day implantation. This precision coating is readily applicable for long-term biofilm-resistant and blood-compatible copolymer coatings covalently grafted from a wide range of medical devices.

Designer broad-spectrum polyimidazolium antibiotics.

For a myriad of different reasons most antimicrobial peptides (AMPs) have failed to reach clinical application. Different AMPs have different shortcomings including but not limited to toxicity issues, potency, limited spectrum of activity, or reduced activity in situ. We synthesized several cationic peptide mimics, main-chain cationic polyimidazoliums (PIMs), and discovered that, although select PIMs show little acute mammalian cell toxicity, they are potent broad-spectrum antibiotics with activity against even pan-antibiotic-resistant gram-positive and gram-negative bacteria, and mycobacteria. We selected PIM1, a particularly potent PIM, for mechanistic studies. Our experiments indicate PIM1 binds bacterial cell membranes by hydrophobic and electrostatic interactions, enters cells, and ultimately kills bacteria. Unlike cationic AMPs, such as colistin (CST), PIM1 does not permeabilize cell membranes. We show that a membrane electric potential is required for PIM1 activity. In laboratory evolution experiments with the gram-positive Staphylococcus aureus we obtained PIM1-resistant isolates most of which had menaquinone mutations, and we found that a site-directed menaquinone mutation also conferred PIM1 resistance. In similar experiments with the gram-negative pathogen Pseudomonas aeruginosa, PIM1-resistant mutants did not emerge. Although PIM1 was efficacious as a topical agent, intraperitoneal administration of PIM1 in mice showed some toxicity. We synthesized a PIM1 derivative, PIM1D, which is less hydrophobic than PIM1. PIM1D did not show evidence of toxicity but retained antibacterial activity and showed efficacy in murine sepsis infections. Our evidence indicates the PIMs have potential as candidates for development of new drugs for treatment of pan-resistant bacterial infections.

Detection of air and surface contamination by SARS-CoV-2 in hospital rooms of infected patients.

Understanding the particle size distribution in the air and patterns of environmental contamination of SARS-CoV-2 is essential for infection prevention policies. Here we screen surface and air samples from hospital rooms of COVID-19 patients for SARS-CoV-2 RNA. Environmental sampling is conducted in three airborne infection isolation rooms (AIIRs) in the ICU and 27 AIIRs in the general ward. 245 surface samples are collected. 56.7% of rooms have at least one environmental surface contaminated. High touch surface contamination is shown in ten (66.7%) out of 15 patients in the first week of illness, and three (20%) beyond the first week of illness (p = 0.01, χ2 test). Air sampling is performed in three of the 27 AIIRs in the general ward, and detects SARS-CoV-2 PCR-positive particles of sizes >4 µm and 1-4 µm in two rooms, despite these rooms having 12 air changes per hour. This warrants further study of the airborne transmission potential of SARS-CoV-2.

A Glycosylated Cationic Block Poly(ß-peptide) Reverses Intrinsic Antibiotic Resistance in All ESKAPE Gram-Negative Bacteria.

Carbapenem-resistant Gram-negative bacteria (GNB) are heading the list of pathogens for which antibiotics are the most critically needed. Many antibiotics are either unable to penetrate the outer-membrane or are excluded by efflux mechanisms. Here, we report a cationic block ß-peptide (PAS8-b-PDM12) that reverses intrinsic antibiotic resistance in GNB by two distinct mechanisms of action. PAS8-b-PDM12 does not only compromise the integrity of the bacterial outer-membrane, it also deactivates efflux pump systems by dissipating the transmembrane electrochemical potential. As a result, PAS8-b-PDM12 sensitizes carbapenem- and colistin-resistant GNB to multiple antibiotics in vitro and in vivo. The ß-peptide allows the perfect alternation of cationic versus hydrophobic side chains, representing a significant improvement over previous antimicrobial α-peptides sensitizing agents. Together, our results indicate that it is technically possible for a single adjuvant to reverse innate antibiotic resistance in all pathogenic GNB of the ESKAPE group, including those resistant to last resort antibiotics.

Enantiomeric glycosylated cationic block co-beta-peptides eradicate Staphylococcus aureus biofilms and antibiotic-tolerant persisters.

The treatment of bacterial infections is hindered by the presence of biofilms and metabolically inactive persisters. Here, we report the synthesis of an enantiomeric block co-beta-peptide, poly(amido-D-glucose)-block-poly(beta-L-lysine), with high yield and purity by one-shot one-pot anionic-ring opening (co)polymerization. The co-beta-peptide is bactericidal against methicillin-resistant Staphylococcus aureus (MRSA), including replicating, biofilm and persister bacterial cells, and also disperses biofilm biomass. It is active towards community-acquired and hospital-associated MRSA strains which are resistant to multiple drugs including vancomycin and daptomycin. Its antibacterial activity is superior to that of vancomycin in MRSA mouse and human ex vivo skin infection models, with no acute in vivo toxicity in repeated dosing in mice at above therapeutic levels. The copolymer displays bacteria-activated surfactant-like properties, resulting from contact with the bacterial envelope. Our results indicate that this class of non-toxic molecule, effective against different bacterial sub-populations, has promising potential for the treatment of S. aureus infections.

The higher prevalence of extended spectrum beta-lactamases among Escherichia coli ST131 in Southeast Asia is driven by expansion of a single, locally prevalent subclone.

The ST131 multilocus sequence type (MLST) of Escherichia coli is a globally successful pathogen whose dissemination is increasing rates of antibiotic resistance. Numerous global surveys have demonstrated the pervasiveness of this clone; in some regions ST131 accounts for up to 30% of all E. coli isolates. However, many regions are underrepresented in these published surveys, including Africa, South America, and Asia. We collected consecutive bloodstream E. coli isolates from three countries in Southeast Asia; ST131 was the most common MLST type. As in other studies, the C2/H30Rx clade accounted for the majority of ST131 strains. Clinical risk factors were similar to other reported studies. However, we found that nearly all of the C2 strains in this study were closely related, forming what we denote the SEA-C2 clone. The SEA-C2 clone is enriched for strains from Asia, particularly Southeast Asia and Singapore. The SEA-C2 clone accounts for all of the excess resistance and virulence of ST131 relative to non-ST131 E. coli. The SEA-C2 strains appear to be locally circulating and dominant in Southeast Asia, despite the intuition that high international connectivity and travel would enable frequent opportunities for other strains to establish themselves.

Antecedent Carbapenem Exposure as a Risk Factor for Non-Carbapenemase-Producing Carbapenem-Resistant Enterobacteriaceae and Carbapenemase-Producing Enterobacteriaceae.

Carbapenem-resistant Enterobacteriaceae (CRE) can be mechanistically classified into carbapenemase-producing Enterobacteriaceae (CPE) and non-carbapenemase-producing carbapenem nonsusceptible Enterobacteriaceae (NCPCRE). We sought to investigate the effect of antecedent carbapenem exposure as a risk factor for NCPCRE versus CPE. Among all patients with CRE colonization and infection, we conducted a case-control study comparing patients with NCPCRE (cases) and patients with CPE (controls). The presence of carbapenemases was investigated with phenotypic tests followed by PCR for predominant carbapenemase genes. We included 843 unique patients with first-episode CRE, including 387 (45.9%) NCPCRE and 456 (54.1%) CPE. The resistance genes detected in CPEs were blaNDM (42.8%), blaKPC (38.4%), and blaOXA-48-like (12.1%). After adjusting for confounders and clustering at the institutional level, the odds of prior 30-day carbapenem exposure was three times higher among NCPCRE than CPE patients (adjusted odds ratio [aOR], 3.48; 95% confidence interval [CI], 2.39 to 5.09; P < 0.001). The odds of prior carbapenem exposure and NCPCRE detection persisted in stratified analyses by Enterobacteriaceae species (Klebsiella pneumoniae and Escherichia coli) and carbapenemase gene (blaNDM and blaKPC). CPE was associated with male gender (aOR, 1.45; 95% CI, 1.07 to 1.97; P = 0.02), intensive care unit stay (aOR, 1.84; 95% CI, 1.24 to 2.74; P = 0.003), and hospitalization in the preceding 1 year (aOR, 1.42; 95% CI, 1.01 to 2.02; P = 0.05). In a large nationwide study, antecedent carbapenem exposure was a significant risk factor for NCPCRE versus CPE, suggesting a differential effect of antibiotic selection pressure.

Environmental colonization and onward clonal transmission of carbapenem-resistant Acinetobacter baumannii (CRAB) in a medical intensive care unit: the case for environmental hygiene.

Background: In May 2015, we noticed an increase in carbapenem-resistant Acinetobacter baumannii (CRAB) infections in the Medical Intensive Care Unit (MICU). To investigate this, we studied the extent of environmental contamination and subsequent onward clonal transmission of CRAB. Methods: We conducted a one-day point prevalence screening (PPS) of the patients and environment in the MICU. We screened patients using endotracheal tube aspirates and swabs from nares, axillae, groin, rectum, wounds, and exit sites of drains. We collected environmental samples from patients' rooms and environment outside the patients' rooms. CRAB isolates from the PPS and clinical samples over the subsequent one month were studied for genetic relatedness by whole genome sequencing (WGS). Results: We collected 34 samples from seven patients and 244 samples from the environment. On the day of PPS, we identified 8 CRAB carriers: 3 who screened positive and 5 previously known clinical infections. We detected environmental contamination in nearly two-thirds of the rooms housing patients with CRAB. WGS demonstrated genetic clustering of isolates within rooms but not across rooms. We analysed 4 CRAB isolates from clinical samples following the PPS. One genetically-related CRAB was identified in the respiratory sample of a patient with nosocomial pneumonia, who was admitted to the MICU five days after the PPS. Conclusion: The extensive environmental colonization of CRAB by patients highlights the importance of environmental hygiene. The transmission dynamics of CRAB needs further investigation.

Pharmacokinetic/Pharmacodynamic Determinants of Vancomycin Efficacy in Enterococcal Bacteremia.

While pharmacokinetic-pharmacodynamic targets for vancomycin therapy are recognized for invasive methicillin-resistant Staphylococcus aureus infections, scant data are available to guide therapy for other Gram-positive infections. A retrospective single-center cohort of patients with Enterococcus bacteremia hospitalized between 1 January 2009 and 31 May 2015 were studied. The average vancomycin AUC0-24 was computed using a Bayesian approach. The MIC was determined by gradient diffusion (Etest; bioMérieux), and the average AUC0-24/MIC value over the initial 72 h of therapy was calculated. We assessed 30-day all-cause mortality as the primary outcome. Classification and regression tree analysis (CART) was used to identify the vancomycin AUC0-24/MIC value associated with 30-day mortality. Fifty-seven patients with enterococcal bacteremia (32 E. faecium, 21 E. faecalis, and 4 other Enterococcus spp.) were studied. The median vancomycin MIC was 0.75 mg/liter (range, 0.38 to 3 mg/liter). All-cause 30-day mortality occurred in 10 of 57 patients (17.5%). A CART-derived vancomycin AUC/MICEtest value of ≥389 was associated with reduced mortality (P = 0.017); failure to achieve this independently predicted 30-day mortality (odds ratio, 6.83 [95% confidence interval = 1.51 to 30.84]; P = 0.01). We found that a vancomycin AUC/MICEtest value of ≥389 achieved within 72 h was associated with reduced mortality. Larger, prospective studies are warranted to verify the vancomycin pharmacodynamic targets associated with maximal clinical outcomes and acceptable safety.

Clinical and Molecular Epidemiology of Carbapenem-Resistant Enterobacteriaceae Among Adult Inpatients in Singapore.

BACKGROUND: Since 2010, the incidence of carbapenem-resistant Enterobacteriaceae (CRE) has been increasing in Singapore. We analyzed the clinical and molecular epidemiology of CRE among adult inpatients in Singapore. METHODS: Quarterly incidence of unique subjects (per 100000 patient-days) with positive clinical and surveillance cultures for CRE were estimated based on mandatory data submitted to the National Public Health Laboratory by public hospitals between 2010 and 2015. CRE-positive adult inpatients were prospectively recruited from 6 public sector hospitals between December 2013 and April 2015. Subjects answered a standardized epidemiologic questionnaire and provided samples for this study. Further clinical information was extracted from subjects' electronic medical records. Whole-genome sequencing was performed on study isolates to determine transmission clusters. RESULTS: Incidence of CRE clinical cultures among adult inpatients plateaued from 2013 (range: 7.73 to 10.32 per 100000 patient-days) following an initial increase between 2010 and end-2012. We prospectively recruited 249 subjects. Their median age was 65 years, 108 (43%) were female, and 161 (64.7%) had carbapenemase-producing Enterobacteriaceae (CPE). On multivariate analysis, prior carbapenem exposure (OR: 3.23; 95% CI: 1.67-6.25) and hematological malignancies (OR: 2.85; 95% CI: 1.10-7.41) were associated with non-carbapenemase-producing CRE (NCPE) (n = 88) compared with CPE (n = 161) subjects. Among 430 CRE isolates from the 249 subjects, 307(71.3%) were CPE, of which 154(50.2%) were blaKPC-positive, 97(31.6%) blaNDM-positive, and 42 (13.7%) blaOXA-positive. Klebsiella pneumoniae (n = 180, 41.9%), Escherichia coli (n = 129, 30.0%) and Enterobacter cloacae (n = 62, 14.4%) were the main Enterobacteriaceae species. WGS (n = 206) revealed diverse bacterial strain type (STs). The predominant blaKPC-positive plasmid was pHS102707 (n = 62, 55.4%) and the predominant blaNDM-positive plasmid was pNDM-ECS01 (n = 46, 48.9%). Five transmission clusters involving 13 subjects were detected. CONCLUSIONS: Clinical CRE trend among adult inpatients showed stabilization following a rapid rise since introduction in 2010 potentially due to infection prevention measures and antimicrobial stewardship. More work is needed on understanding CPE transmission dynamics.