Aztreonam-Avibactam Susceptibility Testing Program for Metallo-Beta-Lactamase-Producing Enterobacterales in the Antibiotic Resistance Laboratory Network, March 2019 to December 2020.

Aztreonam-avibactam is a drug combination pending phase 3 clinical trials and is suggested for treatment of severe infections caused by metallo-beta-lactamase (MBL)-producing Enterobacterales by combining ceftazidime-avibactam and aztreonam. Beginning in 2019, four Antibiotic Resistance Laboratory Network regional laboratories offered aztreonam-avibactam susceptibility testing by broth microdilution. For 64 clinical isolates tested, the MIC50 and MIC90 values of aztreonam-avibactam were 0.5/4 µg/ml and 8/4 µg/ml, respectively. Aztreonam-avibactam displayed potent in vitro activity against the MBL-producing Enterobacterales tested.

Multispecies Outbreak of Verona Integron-Encoded Metallo-ß-Lactamase-Producing Multidrug Resistant Bacteria Driven by a Promiscuous Incompatibility Group A/C2 Plasmid.

BACKGROUND: Antibiotic resistance is often spread through bacterial populations via conjugative plasmids. However, plasmid transfer is not well recognized in clinical settings because of technical limitations, and health care-associated infections are usually caused by clonal transmission of a single pathogen. In 2015, multiple species of carbapenem-resistant Enterobacteriaceae (CRE), all producing a rare carbapenemase, were identified among patients in an intensive care unit. This observation suggested a large, previously unrecognized plasmid transmission chain and prompted our investigation. METHODS: Electronic medical record reviews, infection control observations, and environmental sampling completed the epidemiologic outbreak investigation. A laboratory analysis, conducted on patient and environmental isolates, included long-read whole-genome sequencing to fully elucidate plasmid DNA structures. Bioinformatics analyses were applied to infer plasmid transmission chains and results were subsequently confirmed using plasmid conjugation experiments. RESULTS: We identified 14 Verona integron-encoded metallo-ß-lactamase (VIM)-producing CRE in 12 patients, and 1 additional isolate was obtained from a patient room sink drain. Whole-genome sequencing identified the horizontal transfer of blaVIM-1, a rare carbapenem resistance mechanism in the United States, via a promiscuous incompatibility group A/C2 plasmid that spread among 5 bacterial species isolated from patients and the environment. CONCLUSIONS: This investigation represents the largest known outbreak of VIM-producing CRE in the United States to date, which comprises numerous bacterial species and strains. We present evidence of in-hospital plasmid transmission, as well as environmental contamination. Our findings demonstrate the potential for 2 types of hospital-acquired infection outbreaks: those due to clonal expansion and those due to the spread of conjugative plasmids encoding antibiotic resistance across species.

Assessing the in vitro impact of ceftazidime on aztreonam/avibactam susceptibility testing for highly resistant MBL-producing Enterobacterales.

BACKGROUND: Aztreonam/avibactam is a combination agent that shows promise in treating infections caused by highly antibiotic-resistant MBL-producing Enterobacterales. This combination can be achieved by combining two FDA-approved drugs: ceftazidime/avibactam and aztreonam. It is unknown whether ceftazidime in the combination ceftazidime/aztreonam/avibactam has a synergistic or antagonistic effect on the in vitro activity of aztreonam/avibactam by significantly increasing or decreasing the MIC. OBJECTIVES: To determine whether increasing ceftazidime concentrations affect the MICs of aztreonam/avibactam alone. METHODS: A custom 8 × 8 chequerboard broth microdilution (BMD) panel was made using a digital dispenser (Hewlett-Packard, Corvallis, OR, USA). The panel included orthogonal 2-fold dilution series of aztreonam and ceftazidime ranging from 0.5 to 64 mg/L. Avibactam concentration was kept constant at 4 mg/L throughout the chequerboard. Thirty-seven Enterobacterales isolates from the CDC & FDA Antibiotic Resistance Isolate Bank or CDC's internal collection with intermediate or resistant interpretations to aztreonam and ceftazidime/avibactam were included for testing. All isolates harboured at least one of the following MBL genes: blaIMP, blaNDM or blaVIM. RESULTS: Regardless of the concentration of ceftazidime, aztreonam/avibactam with ceftazidime MICs for all 37 isolates were within one 2-fold doubling dilution of the aztreonam/avibactam MIC. CONCLUSIONS: Ceftazidime, in the combination ceftazidime/avibactam/aztreonam, did not affect the in vitro activity of aztreonam/avibactam in this sample of isolates. These findings can help assure clinical and public health laboratories that testing of aztreonam/avibactam by BMD can act as a reliable surrogate test when the combination of ceftazidime/avibactam and aztreonam is being considered for treatment of highly antibiotic-resistant MBL-producing Enterobacterales.

Antibiotic Susceptibility of NDM-Producing Enterobacterales Collected in the United States in 2017 and 2018.

The treatment of infections caused by carbapenem-resistant Enterobacterales, especially New Delhi metallo-ß-lactamase (NDM)-producing bacteria, is challenging. Although less common in the United States than some other carbapenemase producers, NDM-producing bacteria are a public health threat due to the limited treatment options available. Here, we report on the antibiotic susceptibility of 275 contemporary NDM-producing Enterobacterales collected from 30 U.S. states through the Centers for Disease Control and Prevention's Antibiotic Resistance Laboratory Network. The aims of the study were to determine the susceptibility of these isolates to 32 currently available antibiotics using reference broth microdilution and to explore the in vitro activity of 3 combination agents that are not yet available. Categorical interpretations were determined using Clinical and Laboratory Standards Institute (CLSI) interpretive criteria. For agents without CLSI criteria, Food and Drug Administration (FDA) interpretive criteria were used. The percentage of susceptible isolates did not exceed 90% for any of the FDA-approved antibiotics tested. The antibiotics with breakpoints that had the highest in vitro activity were tigecycline (86.5% susceptible), eravacycline (66.2% susceptible), and omadacycline (59.6% susceptible); 18.2% of isolates were susceptible to aztreonam. All NDM-producing isolates tested were multidrug resistant, and 116 isolates were extensively drug resistant (42.2%); 207 (75.3%) isolates displayed difficult-to-treat resistance. The difficulty in treating infections caused by NDM-producing Enterobacterales highlights the need for containment and prevention efforts to keep these infections from becoming more common.

Validation of Aztreonam-Avibactam Susceptibility Testing Using Digitally Dispensed Custom Panels.

Aztreonam-avibactam is a combination antimicrobial agent with activity against carbapenemase-producing Enterobacteriaceae (CPE) with metallo-ß-lactamases (MßLs). Although aztreonam-avibactam is not yet approved by the U.S. Food and Drug Administration (FDA), clinicians can administer this combination by using two FDA-approved drugs: aztreonam and ceftazidime-avibactam. This combination of drugs is recommended by multiple experts for treatment of serious infections caused by MßL-producing CPE. At present, in vitro antimicrobial susceptibility testing (AST) of aztreonam-avibactam is not commercially available; thus, most clinicians receive no laboratory-based guidance that can support consideration of aztreonam-avibactam for serious CPE infections. Here, we report our internal validation for aztreonam-avibactam AST by reference broth microdilution (BMD) according to Clinical and Laboratory Standards Institute (CLSI) guidelines. The validation was performed using custom frozen reference BMD panels prepared in-house at the Centers for Disease Control and Prevention (CDC). In addition, we took this opportunity to evaluate a new panel-making method using a digital dispenser, the Hewlett Packard (HP) D300e. Our studies demonstrate that the performance characteristics of digitally dispensed panels were equivalent to those of conventionally prepared frozen reference BMD panels for a number of drugs, including aztreonam-avibactam. We found the HP D300e digital dispenser to be easy to use and to provide the capacity to prepare complex drug panels. Our findings will help other clinical and public health laboratories implement susceptibility testing for aztreonam-avibactam.

Imipenemase-producing carbapenem-resistant Enterobacteriaceae transmission in a long-term-care facility during a community-wide multidrug resistant organism outbreak-North Carolina, 2017.

We describe an outbreak of imipenemase metallo-ß-lactamase-producing organisms in a long-term-care facility (LTCF) amid a larger community outbreak of extended-spectrum ß-lactamase-producing organisms. Transmission was propagated by inadequate infection prevention practices. We provided infection prevention recommendations and education, facilitated colonization screening, and increased interfacility communication. This outbreak demonstrates the unmet need for infection prevention education in long-term-care facilities and the importance of prompt public health response to ensure appropriate identification, containment, and prevention of emerging resistance.

Melioidosis after Hurricanes Irma and Maria, St. Thomas/St. John District, US Virgin Islands, October 2017.

We report 2 cases of melioidosis in women with diabetes admitted to an emergency department in the US Virgin Islands during October 2017. These cases emerged after Hurricanes Irma and Maria and did not have a definitively identified source. Poor outcomes were observed when septicemia and pulmonary involvement were present.

Implementation of an Emergency Department Screening and Care Management Referral Process for Patients With Sickle Cell Disease.

PURPOSE OF STUDY: The purpose of the project was to describe the implementation and evaluation of a care management referral program from emergency departments (EDs) to care management services for patients with sickle cell disease (SCD). PRIMARY PRACTICE SETTING: Patients were referred to Community Care of North Carolina (CCNC), which is a private-public collaboration providing care management services and served as a referral hub for the program. Patients received follow-up from either CCNC or the North Carolina Sickle Cell Syndrome Program. METHODOLOGY AND SAMPLE: A multidisciplinary, multiorganizational group streamlined the referral process for patients with SCD who have ongoing care needs by linking patients from the ED to care management services. The article presents a review of program implementation and evaluation over a 3½-year period. The target population were patients who had a diagnosis of SCD and presented to the ED for treatment. Emergency department staff used a modified version of the Emergency Department Sickle Cell Needs Assessment of Needs and Strengths tool to screen for social behavioral health needs in areas such as emotional, financial, pain management, and resources. All forms were faxed to a central number at CCNC for follow-up care management services. Community Care of North Carolina then linked the patient with the appropriate agency and staff for follow-up. RESULTS: More than 900 referrals were received in 3½ years. Pain was the most common reason for referral. An increase in care management intensity was observed over time. All levels of care management intensity saw an increase in the number of patients. IMPLICATIONS FOR CASE MANAGEMENT: Care management occurred across organizations after careful planning among stakeholders. The interagency cooperation permitted the development of a streamlined process. In particular, the creation of a single point for referral was an important component to allow for population-level monitoring and ease of making referrals. Patients with ongoing care needs were identified and there was an increase in the intensity of outpatient care management services delivered.

Development and Validation of a Clinical Laboratory Improvement Amendments-Compliant Multiplex Real-Time PCR Assay for Detection of mcr Genes.

Increased use of colistin in both human and veterinary medicine has led to the emergence of plasmid-mediated colistin resistance (mcr genes). In this study, we report the development of a real-time PCR assay using TaqMan probe-based chemistry for detection of mcr genes from bacterial isolates. Positive control isolates harboring mcr-1 and mcr-2 yielded exponential amplification curves with the assay, and the amplification efficiency was 98% and 96% for mcr-1 and mcr-2, respectively. Each target gene could be reproducibly detected from a sample containing 103 cfu/mL of mcr-harboring bacteria, and there was no cross-reactivity with DNA extracted from several multidrug-resistant bacteria harboring other resistance genes, but lacking mcr genes. Both sensitivity and specificity of the mcr real-time PCR assay were 100% in a method validation performed with a set of 25 previously well-characterized bacterial isolates containing mcr-positive and -negative bacteria. This newly developed assay is a rapid and sensitive tool for detecting emerging mcr genes in cultured bacterial isolates. The assay was successfully validated according to quality standards of the Clinical Laboratory Improvement Amendments (CLIA).

Decline in CD4 T lymphocytes with monotherapy bridging strategy for non-adherent adolescents living with HIV infection: Results of the IMPAACT P1094 randomized trial.

INTRODUCTION: Management of persistently non-adherent youth living with HIV (YLHIV) with virologic failure (VF) on combination antiretroviral therapy (cART) remains challenging. One strategy has been using 3TC/ FTC monotherapy (3TC/FTC), which in the presence of the M184V resistance mutation, does not suppress viral replication nor select for additional drug resistance mutations, and reduces viral fitness with limited side effects. P1094 compared the immunologic outcome of continuing failing cART vs. switching to 3TC/FTC as a "bridging strategy" to subsequent suppressive cART for non-adherent YLHIV with pre-existing M184V resistance. MATERIALS & METHODS: Participants with documented nonadherence, M184V mutation, CD4+ T cell count ≥100 cells/mm3 and VF (HIV-1 plasma RNA ≥400 copies/mL (2.6 log10 HIV-1 RNA) were enrolled and randomized to continue failing cART vs. switch to 3TC/FTC. The primary endpoint (time to ≥30% CD4+ T cell decline or development of CDC class C events) at 28-weeks were assessed by Kaplan-Meier (K-M) curves in an intent-to-treat analysis. RESULTS: Thirty-three perinatally acquired YLHIV participants (16 continuing cART and 17 3TC/FTC) enrolled in the study. The median age, entry CD4+ T cell count, and viral load were 15 years (Inter-quartile range (IQR) 14-20), 472 cells/mm3 (IQR 384-651), and 4.0 log10HIV-1 RNA copies/ml (IQR 3.2-4.5), respectively. Five participants, all in the 3TC/FTC arm, reached the primary endpoint for absolute CD4+ T cell decline (p = 0.02, exact log-rank test comparing monotherapy to cART). The Kaplan-Meier estimate of probability of primary endpoint on 3TC/FTC at 28 weeks was 0.41 (standard error 0.14). There were no CDC class C events or deaths and no statistically significant difference in frequencies of adverse events between the arms. CONCLUSIONS: Non-adherent participants randomized to 3TC/FTC were more likely than those maintained on failing cART to experience a confirmed decline in CD4+ count of ≥30%. Although this study suffers from limitations of small sample size and premature discontinuation, the randomized comparison to continuing failing cART indicates that 3TC/FTC provides inferior protection from immunologic deterioration for non-adherent youth with M184V resistance. Better alternatives to 3TC/FTC such as ART with higher barriers to resistance and novel adherence and treatment strategies for nonadherent youth are urgently needed. TRIAL REGISTRATION: Clinical Trials.gov NCT01338025.