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The Enterobacter cloacae complex (ECC) includes common nosocomial pathogens capable of producing a wide variety of infections. Broad-spectrum antibiotic resistance, including the recent emergence of resistance to last-resort carbapenems, has led to increased interest in this group of organisms and carbapenem-resistant E. cloacae complex (CREC) in particular. Molecular typing methods based on heat-shock protein sequence, pulsed-field gel electrophoresis, comparative genomic hybridization, and, most recently, multilocus sequence typing have led to the identification of over 1069 ECC sequence types in 18 phylogenetic clusters across the globe. Whole-genome sequencing and comparative genomics, moreover, have facilitated global analyses of clonal composition of ECC and specifically of CREC. Epidemiological and genomic studies have revealed diverse multidrug-resistant ECC clones including several potential epidemic lineages. Together with intrinsic β-lactam resistance, members of the ECC exhibit a unique ability to acquire genes encoding resistance to multiple classes of antibiotics, including a variety of carbapenemase genes. In this review, we address recent advances in the molecular epidemiology of multidrug-resistant E. cloacae complex, focusing on the global expansion of CREC.
Recent months have seen surges of SARS-CoV-2 infection across the globe along with considerable viral evolution. Extensive mutations in the spike protein of variants B.1.1.7, B1.351, and P.1 have raised concerns that the efficacy of current vaccines and therapeutic monoclonal antibodies could be threatened. In vitro studies have shown that one mutation, E484K, plays a crucial role in the loss of neutralizing activity of some monoclonal antibodies as well as most convalescent and vaccinee sera against variant B.1.351. In fact, two vaccine trials have recently reported lower protective efficacy in South Africa, where B.1.351 is dominant. To survey for these novel variants in our patient population in New York City, PCR assays were designed to identify viruses with two signature mutations, E484K and N501Y. We observed a steady increase in the detection rate from late December to mid-February, with an alarming rise to 12.3% in the past two weeks. Whole genome sequencing further demonstrated that most of our E484K isolates (n=49/65) fell within a single lineage: NextStrain clade 20C or Pangolin lineage B.1.526. Patients with this novel variant came from diverse neighborhoods in the metropolitan area, and they were on average older and more frequently hospitalized. Phylogenetic analyses of sequences in the database further reveal that this B.1.526 variant is scattered in the Northeast of US, and its unique set of spike mutations may also pose an antigenic challenge for current interventions.
Ceftazidime-avibactam (CAZ-AVI) is a promising novel treatment for infections caused by carbapenem-resistant (CRE). Despite improved treatment outcomes compared to those achieved with aminoglycoside- and colistin-based regimens, the rapid evolution of CAZ-AVI resistance during treatment has previously been reported in sequence type 258 (ST258) -harboring isolates. Here, we report the stepwise evolution and isolation of two phenotypically distinct CAZ-AVI-resistant isolates from a patient with pancreatitis. All susceptible ( = 3) and resistant ( = 5) isolates were of the ST307 clonal background, a rapidly emerging clone. Taking advantage of short-read Illumina and long-read Oxford Nanopore sequencing and full-length assembly of the core chromosome and plasmids, we demonstrate that CAZ-AVI resistance first occurred through a 532G → T point mutation in (D179Y protein substitution) following only 12 days of CAZ-AVI exposure. While subsequent isolates exhibited substantially decreased meropenem (MEM) MICs (≤2 μg/ml), later cultures demonstrated a second CAZ-AVI resistance phenotype with a lower CAZ-AVI MIC (12 μg/ml) but also MEM resistance (MIC > 128 μg/ml). These CAZ-AVI- and MEM-resistant isolates showed evidence of multiple genomic adaptations, mainly through insertions and deletions. This included amplification and transposition of wild-type into a novel plasmid, an IS insertion upstream of , and disruption of the gene locus in these isolates. Our findings illustrate the potential of CAZ-AVI resistance to emerge in non- ST258 clonal backgrounds and alternative variants. These results raise concerns about the strong selective pressures incurred by novel carbapenemase inhibitors, such as avibactam, on isolates previously considered invulnerable to CAZ-AVI resistance. There is an urgent need to further characterize non-KPC-mediated modes of carbapenem resistance and the intrinsic bacterial factors that facilitate the rapid emergence of resistance during treatment.
Enterococcus status at ICU admission was associated with risk for death or all-cause infection, and rectal carriage of common ICU pathogens predicted specific infections. The gastrointestinal microbiome may have a role in risk stratification and early diagnosis of ICU infections.
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