Clonal outbreak caused by VIM-4-producing Proteus mirabilis in a Greek tertiary-care hospital

Replacement of the Double Meropenem Disc Test with a Lateral Flow Assay for the Detection of Carbapenemase-Producing Enterobacterales and Pseudomonas aeruginosa in Clinical Laboratory Practice

The prompt detection of carbapenemases among Gram-negative bacteria isolated from patients' clinical infection samples and surveillance cultures is important for the implementation of infection control measures. In this context, we evaluated the effectiveness of replacing phenotypic tests for the detection of carbapenemase producers with the immunochromatographic Carbapenem-Resistant K.N.I.V.O. Detection K-Set lateral flow assay (LFA). In total, 178 carbapenem-resistant Enterobacterales and 32 carbapenem-resistant Pseudomonas aeruginosa isolated in our hospital were tested with both our established phenotypic and molecular testing procedures and the LFA. The Kappa coefficient of agreement for Enterobacterales was 0.85 (p < 0.001) and 0.6 (p < 0.001) for P. aeruginosa. No major disagreements were observed and notably, in many cases, the LFA detected more carbapenemases than the double meropenem disc test, especially regarding OXA-48 in Enterobacterales and VIM in P. aeruginosa. Overall, the Carbapenem-Resistant K.N.I.V.O. Detection K-Set was very effective and at least equivalent to the standard procedures used in our lab. However, it was much faster as it provided results in 15 min compared to a minimum of 18-24 h for the phenotypic tests.

Study of the molecular characteristics and homology of carbapenem-resistant Proteus mirabilis by whole genome sequencing

Introduction. Proteus mirabilis is part of the family Enterobacteriaceae, and is naturally resistant to various antimicrobial drugs. In recent years, outbreaks of severe nosocomial infections caused by carbapenem-resistant P. mirabilis (CR-PMI) have been frequently reported. Few studies exist on the whole-genome molecular characteristics of this bacterium in China and elsewhere, which stimulated the implementation of this study.Hypothesis. CR-PMI strains contained the multiple drug resistance genes and exhibited a high resistance rate to commonly used antimicrobial drugs.Aim. Our goals here were to identify resistance mechanisms and homology of CR-PMI strains and provide a theoretical basis for clinical treatment and controlling nosocomial infections.Methodology. Bacterial species identification was carried out using matrix-assisted laser desorption/ionization time of flight MS (MALDI-TOF-MS). Antimicrobial susceptibility was determined using the VITEK 2 system and Kirby-Bauer (K-B) disc-diffusion method. Whole-genome sequencing (WGS) was conducted by the Illumina platform NovaSeq sequencer. Antibiotic resistance genes (ARGs) were identified using the NCBI database with Abricate. Plasmid replicon types were identified using PlasmidFinder, available at the Center for Genomic Epidemiology.Results. Five CR-PMI strains collected in our hospital from July 2019 to September 2021 were resistant to almost all antimicrobial agents except aztreonam (ATM), amikacin (AMK) and cefotetan (CTT). All CR-PMI strains contained the carbapenem resistance gene New Delhi metallo-β-lactamase 1 (bla _NDM-1), and two strains harboured extended-spectrum β-lactamase (ESBL) genes bla _PER-4 and bla _CTX-M-65. The five CR-PMI strains contained 27, 18, 30, 25 and 24 drug-resistance genes, respectively. Most antimicrobial resistance genes were detected for aminoglycosides (n=14), followed by cephalosporins (n=7). The phylogenetic tree was divided into five evolutionary groups, and the five CR-PMI strains were in the four evolutionary groups B-E.Conclusion Overall, CR-PMI strains exhibited a high resistance rate to commonly used antimicrobial drugs, and contained the carbapenem resistance gene bla _NDM-1. The CR-PMI strains showed a polyclonal trend in different wards at different times. Most importantly, all strains identified contained important antimicrobial resistance genes, which may lead to severe drug resistance transmission and fatal multiple resistant bacterial infections.

Description of a new non-Tn4401 element (NTEKPC-IIe) harboured on IncQ plasmid in Citrobacter werkmanii from recreational coastal water

OBJECTIVES

Here we describe an IncQ1-like plasmid carrying blaKPC-2 in a new non-Tn4401 element found in Citrobacter werkmanii recovered from coastal water.

METHODS

In vitro and in silico approaches were used to assess antimicrobial resistance determinants, as well as blaKPC-2 vicinities.

RESULTS

The LB-887 isolate showed a multidrug-resistant phenotype and was identified as C. werkmanii. Resistome analysis identified further acquired resistance determinants to β-lactams, aminoglycosides, sulphonamides/trimethoprim, tetracyclines, chloramphenicol, macrolides, rifampicin and fluoroquinolones. Plasmidome included incompatibility groups IncA, IncC2, IncR, Col and IncQ families. The blaKPC-2 was inserted on a new variant of NTEKPC-II, called here NTEKPC-IIe, carried by an InQ1-like plasmid of 7930 kb (pKPC-LB887). NTEKPC-IIe differed from NTEKPC-IId by the complete absence of ISKpn6-tnpA. The InQ1-like backbone harbouring this element had been described in Enterobacterales recovered from clinical and environmental settings.

CONCLUSION

Unravelling genetic structures related to blaKPC dissemination in different settings may provide clues on the main forces driving evolution of this important resistance determinant. Indeed, the occurrence of blaKPC in a new NTEKPC variant from an environmental source highlights the ongoing evolution of this mobile genetic element. In addition, blaKPC carriage on a small and highly mobilizable IncQ plasmid in C. freundii complex from recreational water, similar to others found in clinical isolates, may suggest its relevance for blaKPC-2 dissemination among different compartments.

First report of a blaVIM-1 metallo-β-lactamase-possessing Klebsiella michiganensis

OBJECTIVES

Klebsiella michiganensis is an emerging pathogen. Like Klebsiella pneumoniae, this species is able to acquire antibiotic resistance genes (ARGs) via mobile genetic elements. In this context, K. michiganensis isolates producing carbapenemases of KPC, NDM, IMP and OXA-48-like types have already been reported. Here we characterised a strain (BD-50-Km) isolated from a rectal swab of a Turkish patient hospitalised in Switzerland.

METHODS

Species identification was initially performed using MALDI-TOF/MS. Antimicrobial susceptibility testing was done by the microdilution method. Whole-genome sequencing (WGS) was performed with both Illumina and Nanopore platforms and was used to confirm species identification, to characterise plasmids and to perform core-genome analyses.

RESULTS

BD-50-Km was initially identified as Klebsiella oxytoca and showed reduced susceptibility to imipenem. However, WGS indicated that the isolate was actually K. michiganensis. BD-50-Km carried the bla_VIM-1 gene associated with a rare class 1 integron (In87) located on a pST1 196 kb IncC plasmid. This plasmid shares its backbone with many other IncC plasmids found in different species (including five K. michiganensis), but not the same In87 and the remaining region harbouring various ARGs. BD-50-Km belongs to the novel ST342. Moreover, core-genome analysis (single nucleotide variant analysis) showed that BD-50-Km was not closely related to any K. michiganensis strains deposited in NCBI (n = 212), including the 38 so far reported as possessing carbapenemase genes.

CONCLUSION

This is the first report of a bla_VIM-possessing K. michiganensis clinical isolate. The spread of plasmid-mediated VIM carbapenemases in this emerging pathogen represents an additional threat to our therapeutic armamentarium.