Bloodstream infection caused by KPC-producing Klebsiella pneumoniae resistant to ceftazidime/avibactam: epidemiology and genomic characterization

Abstract

Aim of this study was to evaluate the incidence of ceftazidime/avibactam resistance among KPCproducing Klebsiella pneumoniae (KPC-Kp) strnins isolated from patients with bloodstream infection. MethodsWe collected 120 carbapenemase producing Enterobacteriaceae (CPE) strnins from unique patients hospitalized in two Italian hospitals between Januaiy 2018 to Febmaiy 2019. Strains were phenotypically characterized for the type of carbapenemase production and susceptibility to ceftazidime/avibactam. Ceftazidime/avibactam-resistant strains were chai• acterized by wholegenome sequencmg. ResultsDm-ing the study period, we characterized 105 (87,5%) KPC producers among a total of 120 CPE strains. Ceftazidime-avibactam resistance was found in three KPC-Kp strnins isolated from patients with no histo1y of previous ceftazidime/avibactam-based treatment. Of note, two out of three ceftazidime-avibactam-resistant KPC-Kp were also resistant to meropenem/vaborbactam. Genomic chai•acterization showed that a ceftazidime/avibactam-resistant KPC-Kp hai•bored a mixed population with D179Y mutated KPC-2, while the other two ceftazidime-avibactam-resistant KPC-Kp possessed non-functional ompK35-ompK37 and mutated ompK36 porins associated with higher copy number of blaKPC gene. Conclusion 48Om results showed that incidence of ceftazidime/avibactam resistance emerged in KCP-Kp strains independently from previous antimicrobial exposme. Resistance to ceftazidime/avibactam was associated to mutations within blaKPc gene or porins deficiency associated to higher blaKPc copy number that is also related to the meropenem/vaborbactam resistance.

Emergence of meropenem/vaborbactam resistance in KPC-producing Klebsiella pneumoniae causing bloodstream infections in northern Italy, 2018

“…At the same time, our results showed that no speci c mutations were observed in KPC-Kp isolates resistant both to meropenem/vaborbactam and ceftazidime/avibactam in comparison to strains resistant to meropenem/vaborbactam alone. These results are in accordance with previous ndings that showed as cross-resistance to meropenem/vaborbactam and ceftazidime/avibactam was due to loss-of-function mutations in the OmpK35 and OmpK36 porins which are also associated to elevated MICs for ß-lactams [4,5].…”

“…Bacteria was identi ed by MALDI-TOF (Bruker Daltonics, Germay) and antimicrobial susceptibility testing was performed by MicroScan Walkaway system and con rmed by MIC test strip (Lio lchem, Italy). The MIC value for colistin was determined by reference broth microdilution method [4]. MIC results were interpreted according to EUCAST clinical breakpoints v11.0 (http://www.eucast.org/clinical_breakpoints/).…”

“…However, limited information is still available on the e cacy of MEM/VAB in clinical practice and the in vivo evolution of emerging resistant strains [3]. Recently, in vitro studies demonstrated that mutations causing loss-of-function of OmpK35 and OmpK36 porins or reduced production can generate resistance to MEM/VAB and/or ceftazidime/avibactam (CAZ/AVI) [4,5].…”

Distribution of β-Lactamase Genes and Genetic Context of blaKPC-2 in Clinical Carbapenemase-Producing Klebsiella pneumoniae Isolates

“… 27 Since there is no history of previous antimicrobial exposure to CAZ/AVI treatment or specific mutations were observed in the bla KPC-2 gene, hyperexpression of the bla KPC-2 gene associated with alteration in the outer membrane or other unknown mechanisms might account for this low level of CAZ/AVI resistance. 28 The transconjugants exhibited reduced resistance levels to carbapenems compared with clinical isolates. The copy number of genes and selective expression of promoters in strains of different species or genera, 29 restoration of deficient Omp proteins, and antibiotic selection pressure could influence the MIC level of the transconjugants.…”

Distribution of β-lactamase Gene and Genetic Context of blaKPC-2 in Clinical Carbapenemase-producing Klebsiella Pneumoniae Isolates

“…Intriguingly, in addition to the high level of carbapenem resistance with a meropenem MIC of 1,024 mg/L, the strain KP3034 exhibited a higher MIC level for CAZ/AVI (16/4 mg/L) than the other strains detected. As no history of previous antimicrobial exposure to CAZ/AVI treatment or speci c mutations were observed in the bla KPC−2 gene, hyper-expression of the bla KPC−2 gene associated with porin de ciency in the outer membrane, or other unknown mechanisms might account for this low level of CAZ/AVI resistance [25] .…”