The first report of a novel IncHI1B bla SIM-1-carrying megaplasmid pSIM-1-BJ01 from a clinical Klebsiella pneumoniae isolate

Carbapenem-resistant Klebsiella pneumoniae: the role of plasmids in emergence, dissemination, and evolution of a major clinical challenge

INTRODUCTION

Klebsiella pneumoniae is a major agent of healthcare-associated infections and a cause of some community-acquired infections, including severe bacteremic infections associated with metastatic abscesses in liver and other organs. Clinical relevance is compounded by its outstanding propensity to evolve antibiotic resistance. In particular, the emergence and dissemination of carbapenem resistance in K. pneumoniae has posed a major challenge due to the few residual treatment options, which have only recently been expanded by some new agents. The epidemiological success of carbapenem-resistant K. pneumoniae (CR-Kp) is mainly linked with clonal lineages that produce carbapenem-hydrolyzing enzymes (carbapenemases) encoded by plasmids.

AREAS COVERED

Here, we provide an updated overview on the mechanisms underlying the emergence and dissemination of CR-Kp, focusing on the role that plasmids have played in this phenomenon and in the co-evolution of resistance and virulence in K. pneumoniae.

EXPERT OPINION

CR-Kp have disseminated on a global scale, representing one of the most important contemporary public health issues. These strains are almost invariably associated with complex multi-drug resistance (MDR) phenotypes, which can also include recently approved antibiotics. The heterogeneity of the molecular bases responsible for these phenotypes poses significant hurdles for therapeutic and diagnostic purposes.

Characterization of a Novel Carbapenem-Resistant Klebsiella michiganensis Strain Coharboring the blaSIM-1, blaOXA-1, blaCTX-M-14, qnrS, and aac(6')-Ib-cr Genes

Carbapenem-resistant Klebsiella michiganensis (CRKM) and Klebsiella oxytoca (CRKO) strains have occasionally been reported to cause severe infections. However, SIM-producing K. michiganensis strains have never been described. In this study, we phenotypically and genetically characterized 6 CRKM and CRKO strains isolated over the past 10 years at a Chinese tertiary hospital. All six strains were positive for the mCIM test, and five were positive for the MBL test. Carbapenemase-encoding genes (bla_KPC, bla_NDM, bla_VIM, bla_IMP, bla_OXA-23, bla_OXA-24, bla_OXA-51, and bla_OXA-58) and another 12 resistance genes were screened by PCR, and bla_KPC, bla_NDM, and bla_IMP were identified in five strains. However, the CRKM strain KM41, which was resistant to IPM and MEM with minimum inhibitory concentrations (MICs) of 4 µg/ml and 16 µg/ml, respectively, had positive mCIM and MBL results but lacked the eight carbapenemase-encoding genes. Whole-genome sequencing of the KM41 strain revealed more than 20 drug resistance genes; in particular, bla_SIM-1, bla_OXA-1, bla_CTX-M-14, qnrS, aac(6')-Ib-cr, aadA17, and aar-3 were found to be located in a single plasmid. To the best of our knowledge, this is the first description of a K. michiganensis strain coharboring bla_SIM-1, bla_OXA-1, bla_CTX-M-14, qnrS, and aac(6')-Ib-cr in China.

The Emergence of Carbapenem Resistant Enterobacteriaceae Producing GIM-1 and SIM-1 Clinical Isolates in Khartoum-Sudan

Purpose

The aim of this study was to detect multidrug resistant GIM-1 and SIM-1 producing Enterobacteriaceae clinical isolates from hospitalized patients across three Khartoum State Teaching Hospitals, Sudan.

Patients and Methods

From May 2018 to October 2019, Enterobacteriaceae clinical isolates from inpatients admitted to different Khartoum state hospitals. Genes for carbapenemase (GIM-1 and SIM-1) were amplified by polymerase chain reaction (PCR). Agar dilution method was used to determine MICs for imipenem and meropenem after antimicrobial susceptibility testing.

Results

Five (1.29%) isolates of Enterobacteriaceae [2 (0.51%) Escherichia coli isolates produce GIM-1, 2 (0.51%) Klebsiella pneumoniae isolates (one [0.25%] of each produce of GIM-1 and of SIM-1), and 1 (0.25%) Enterobacter cloacae isolate produce GIM-1]. Susceptibility profiling of the isolates showed a low-level resistance to imipenem and meropenem MICs (8, 16 and 32 μg/mL). It also had resistance to ampicillin, extended-spectrum cephalosporin's, aztreonam, and amoxicillin-clavulanate and with the two K. pneumoniae strains showing resistance to colistin.

Conclusion

We report the emergence of four GIM-1 producing Enterobacteriaceae strains and one strain of SIM-1 producing K. pneumoniae genes, isolated from hospitalized patients, with a high resistance pattern to antimicrobial agents. Whole-genome sequencing (WGS) is necessary for precise identification of clonal diversity backgrounds of acquired carbapenemase genes in diagnostic laboratories as the number of cases of carbapenem resistant Enterobacteriaceae infection increases annually.

The Current Burden of Carbapenemases: Review of Significant Properties and Dissemination among Gram-Negative Bacteria

Carbapenemases are β-lactamases belonging to different Ambler classes (A, B, D) and can be encoded by both chromosomal and plasmid-mediated genes. These enzymes represent the most potent β-lactamases, which hydrolyze a broad variety of β-lactams, including carbapenems, cephalosporins, penicillin, and aztreonam. The major issues associated with carbapenemase production are clinical due to compromising the activity of the last resort antibiotics used for treating serious infections, and epidemiological due to their dissemination into various bacteria across almost all geographic regions. Carbapenemase-producing Enterobacteriaceae have received more attention upon their first report in the early 1990s. Currently, there is increased awareness of the impact of nonfermenting bacteria, such as Acinetobacter baumannii and Pseudomonas aeruginosa, as well as other Gram-negative bacteria that are carbapenemase-producers. Outside the scope of clinical importance, carbapenemases are also detected in bacteria from environmental and zoonotic niches, which raises greater concerns over their prevalence, and the need for public health measures to control consequences of their propagation. The aims of the current review are to define and categorize the different families of carbapenemases, and to overview the main lines of their spread across different bacterial groups.