Carbapenemase production among less-common Enterobacterales genera: 10 US sites, 2018.

BACKGROUND: Historically, United States' carbapenem-resistant Enterobacterales (CRE) surveillance and mechanism testing focused on three genera: Escherichia, Klebsiella, and Enterobacter (EsKE); however, other genera can harbour mobile carbapenemases associated with CRE spread. OBJECTIVES: From January through May 2018, we conducted a 10 state evaluation to assess the contribution of less common genera (LCG) to carbapenemase-producing (CP) CRE. METHODS: State public health laboratories (SPHLs) requested participating clinical laboratories submit all Enterobacterales from all specimen sources during the surveillance period that were resistant to any carbapenem (Morganellaceae required resistance to doripenem, ertapenem, or meropenem) or were CP based on phenotypic or genotypic testing at the clinical laboratory. SPHLs performed species identification, phenotypic carbapenemase production testing, and molecular testing for carbapenemases to identify CP-CRE. Isolates were categorized as CP if they demonstrated phenotypic carbapenemase production and ≥1 carbapenemase gene (bla KPC, bla NDM, bla VIM, bla IMP, or bla OXA-48-like) was detected. RESULTS: SPHLs tested 868 CRE isolates, 127 (14.6%) were from eight LCG. Overall, 195 (26.3%) EsKE isolates were CP-CRE, compared with 24 (18.9%) LCG isolates. LCG accounted for 24 (11.0%) of 219 CP-CRE identified. Citrobacter spp. was the most common CP-LCG; the proportion of Citrobacter that were CP (11/42, 26.2%) was similar to the proportion of EsKE that were CP (195/741, 26.3%). Five of 24 (20.8%) CP-LCG had a carbapenemase gene other than bla KPC. CONCLUSIONS: Participating sites would have missed approximately 1 in 10 CP-CRE if isolate submission had been limited to EsKE genera. Expanding mechanism testing to additional genera could improve detection and prevention efforts.

Acquisition of Ciprofloxacin Resistance Among an Expanding Clade of ß-Lactamase-Positive, Serogroup Y Neisseria meningitidis in the United States.

BACKGROUND: Penicillin and ciprofloxacin are important for invasive meningococcal disease (IMD) management and prevention. IMD cases caused by penicillin- and ciprofloxacin-resistant Neisseria meningitidis containing a ROB-1 ß-lactamase gene (blaROB-1) and a mutated DNA gyrase gene (gyrA) have been recently reported in the United States. METHODS: We examined 2097 meningococcal genomes collected through US population-based surveillance from January 2011 to February 2020 to identify IMD cases caused by strains with blaROB-1- or gyrA-mediated resistance. Antimicrobial resistance was confirmed phenotypically. The US isolate genomes were compared to non-US isolate genomes containing blaROB-1. Interspecies transfer of ciprofloxacin resistance was assessed by comparing gyrA among Neisseria species. RESULTS: Eleven penicillin- and ciprofloxacin-resistant isolates were identified after December 2018; all were serogroup Y, sequence type 3587, clonal complex (CC) 23, and contained blaROB-1 and a T91I-containing gyrA allele. An additional 22 penicillin-resistant, blaROB-1- containing US isolates with wild-type gyrA were identified from 2013 to 2020. All 33 blaROB-1-containing isolates formed a single clade, along with 12 blaROB-1-containing isolates from 6 other countries. Two-thirds of blaROB-1-containing US isolates were from Hispanic individuals. Twelve additional ciprofloxacin-resistant isolates with gyrA T91 mutations were identified. Ciprofloxacin-resistant isolates belonged to 6 CCs and contained 10 unique gyrA alleles; 7 were similar or identical to alleles from Neisseria lactamica or Neisseria gonorrhoeae. CONCLUSIONS: Recent IMD cases caused by a dual resistant serogroup Y suggest changing antimicrobial resistance patterns in the United States. The emerging dual resistance is due to acquisition of ciprofloxacin resistance by ß-lactamase-containing N. meningitidis. Routine antimicrobial resistance surveillance will effectively monitor resistance changes and spread.

Infectious Period of Severe Acute Respiratory Syndrome Coronavirus 2 in 17 Nursing Home Residents-Arkansas, June-August 2020.

BACKGROUND: To estimate the infectious period of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in older adults with underlying conditions, we assessed duration of coronavirus disease 2019 (COVID-19) symptoms, reverse-transcription polymerase chain reaction (RT-PCR) positivity, and culture positivity among nursing home residents. METHODS: We enrolled residents within 15 days of their first positive SARS-CoV-2 test (diagnosis) at an Arkansas facility from July 7 to 15, 2020 and instead them for 42 days. Every 3 days for 21 days and then weekly, we assessed COVID-19 symptoms, collected specimens (oropharyngeal, anterior nares, and saliva), and reviewed medical charts. Blood for serology was collected on days 0, 6, 12, 21, and 42. Infectivity was defined by positive culture. Duration of culture positivity was compared with duration of COVID-19 symptoms and RT-PCR positivity. Data were summarized using measures of central tendency, frequencies, and proportions. RESULTS: We enrolled 17 of 39 (44%) eligible residents. Median participant age was 82 years (range, 58-97 years). All had ≥3 underlying conditions. Median duration of RT-PCR positivity was 22 days (interquartile range [IQR], 8-31 days) from diagnosis; median duration of symptoms was 42 days (IQR, 28-49 days). Of 9 (53%) participants with any culture-positive specimens, 1 (11%) severely immunocompromised participant remained culture-positive 19 days from diagnosis; 8 of 9 (89%) were culture-positive ≤8 days from diagnosis. Seroconversion occurred in 12 of 12 (100%) surviving participants with ≥1 blood specimen; all participants were culture-negative before seroconversion. CONCLUSIONS: Duration of infectivity was considerably shorter than duration of symptoms and RT-PCR positivity. Severe immunocompromise may prolong SARS-CoV-2 infectivity. Seroconversion indicated noninfectivity in this cohort.

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.

ß-Lactamase-Producing, Ciprofloxacin-Resistant Neisseria meningitidis Isolated From a 5-Month-Old Boy in the United States.

Worldwide, there have been few reports of ß-lactamases causing penicillin resistance in Neisseria meningitidis. The first known case of disease in the United States due to a ß-lactamase-producing, ciprofloxacin-resistant N. meningitidis was recently identified. This has potential implications on standard laboratory testing and empiric management of meningococcal disease.

Detection of Ciprofloxacin-Resistant, ß-Lactamase-Producing Neisseria meningitidis Serogroup Y Isolates - United States, 2019-2020.

Meningococcal disease is a sudden-onset, life-threatening illness caused by the bacterium Neisseria meningitidis. Prompt empiric antibiotic treatment can reduce morbidity and mortality among patients, and antibiotic prophylaxis can prevent secondary disease in close contacts. Historically, N. meningitidis isolates in the United States have largely been susceptible to the antibiotics recommended for treatment and prophylaxis, including penicillin and ciprofloxacin. This report describes detection of penicillin-resistant and ciprofloxacin-resistant N. meningitidis serogroup Y (NmY) isolates in the United States. NmY isolates containing a blaROB-1 ß-lactamase enzyme gene conferring resistance to penicillins (1) were recovered from 33 cases reported during 2013-2020. Isolates from 11 of these cases, reported during 2019-2020, harbored a ciprofloxacin resistance-associated mutation in a chromosomal gene (gyrA). Cases were reported from 12 geographically disparate states; a majority of cases (22 of 33, 67%) occurred in Hispanic persons. These cases represent a substantial increase in penicillin-resistant and ciprofloxacin-resistant meningococci in the United States since 2013. Ceftriaxone and cefotaxime, the recommended first-line agents for empiric bacterial meningitis treatment, can continue to be used for treatment, but health care providers should ascertain susceptibility of meningococcal isolates to penicillin before switching to penicillin or ampicillin. Ongoing monitoring for antimicrobial resistance among meningococcal isolates and prophylaxis failures will be important to inform treatment and prophylaxis recommendations.

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.