Dynamic evolution of ceftazidime-avibactam resistance due to interchanges between blaKPC-2 and blaKPC-145 during treatment of Klebsiella pneumoniae infection

Dynamic evolution of KPC-230-mediated resistance to ceftazidime-avibactam during the treatment of carbapenem-resistant Klebsiella pnenmoniae

The molecular mechanisms driving the development of KPC-230-mediated resistance to ceftazidime-avibactam during treatment of carbapenem-resistant Klebsiella pneumoniae infection was elucidated by analyzing specimens collected from a patient, including one blaKPC-230-positive and three blaKPC-2-positive Klebsiella pnenmoniae isolates.

Analysis of the virulence of a lethal, carbapenem-resistant hypervirulent KPC-33-producing Klebsiella pneumoniae: Emergence of ST11-KL64 hv-CRKP in ICU

OBJECTIVE

Hypervirulent and carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) poses a serious threat to public health. Here, we analyse a case of systemic infection caused by a hv-CRKP, which ultimately led to the patient's death from sepsis. And a total of 30 CRKPs were analyzed to elucidate the molecular epidemiological features of CRKPs in the hospital, and to provide a basis for clinical anti-infective therapy.

METHODS

In this case, a total of 7 K. pneumoniae strains were isolated from the blood, sputum, urine, and feces of the patient. The Vitek-2 compact system was used to identify the strains and perform antimicrobial susceptibility testing. Biofilm formation, siderophore production assays and Galleria mellonella infection model were used to verify the virulence phenotypes of the strains in the case. Whole-genome sequencing was conducted on the four hv-CRKP isolated from different samples in the case and 26 other CRKP collected in our hospital from September to November in 2022, using the Illumina Hiseq 6000 high-throughput sequencing platform to analyse the resistance and virulence genes.

RESULTS

In the case, after 7 days of treatment with ceftazidime-avibactam (CZA), the resistance profile of the strains changed. The strain that was initially sensitive to CZA developed to resistant, resistant to imipenem (IPM) developed to sensitive, and resistant to meropenem (MEM) developed to intermediate. Whole-genome sequencing revealed that the four strains in the case were all ST11-KL64 K. pneumoniae, and the change in resistance phenotype was due to the mutation from blaKPC-2 to blaKPC-33. KPN7 had a total of six plasmids, with siderophore-related genes iucABCD and iutA, and mucoid phenotype-related gene rmpA2 located on plasmid p4-KPN7; resistance genes blaKPC-33, blaTEM-1B, and blaCTX-M-65 located on plasmid p5-KPN7; and virulence genes fim, irp, iutA, and ybt located on the chromosome. Biofilm formation and siderophore production assays confirmed that the seven K. pneumoniae strains isolated in this case had strong biofilm formation and siderophore production capabilities. Galleria mellonella Infection Model showed that KPN4 and KPN7 was phenotypically highly virulent and KPN7 performed lower virulence compared to KPN4. Apart from the 4 hv-CRKP strains, other 26 CRKP strains all carried blaKPC-2, and 69.2% (18/26) were ST-11 and 30.8%(8/26) were ST-15. And 83.3% (15/18) were ST11-KL64 strains, followed by ST11-KL25 strains 11.1%(2/18) and ST11-KL47 strain 5.6%(1/18). All the eight ST-15 strains were KL-19.

CONCLUSION

The ST11-KL64 hv-CRKP clone spread widely in ICU carried numerous resistance and virulence genes, and under antibiotic pressure, they easily underwent mutations resulting in changes in resistance phenotypes, especially in mutations of blaKPC-2 gene in acquiring resistance to CZA. Therefore, clinical attention should be paid to such strains, and the use of antibiotics should be adjusted promptly based on the susceptibility of the strains to antimicrobial agents.

A large-scale surveillance revealed that KPC variants mediated ceftazidime-avibactam resistance in clinically isolated Klebsiella pneumoniae

To monitor the resistance rate and gain a deeper understanding of the resistance mechanisms, we conducted over a 2-year surveillance focusing on the Klebsiella pneumoniae associated with the clinical usage of ceftazidime-avibactam (CZA) in a teaching hospital. A total of 4,641 K. pneumoniae isolates were screened to identify the CZA resistance through antimicrobial susceptibility testing. Comprehensive analyses, including homology analysis, conjugation experiments, clone assays, and whole genome sequencing, were furtherly performed on the CZA-resistant strains. In total, four CZA-resistant K. pneumoniae (CZA-R-Kp) strains were separated from four patients, in which three of them received CZA treatment during the hospitalization, accounting for a 4% (3/75) resistance development rate of K. pneumoniae under CZA stress. All CZA-R-Kp isolates were found to possess variants of blaKPC-2. The identified mutations included blaKPC-33, blaKPC-86, and a novel variant designated as blaKPC-129, all of which were located in the Ω loop of the KPC enzyme. These mutations were found to impact the amino acid sequence and spatial structure of the enzyme's active center, consequently affecting KPC carbapenemase activity. This study underscores the importance of active surveillance to monitor the emergence of resistance to CZA, highlighting the need for ongoing research to develop effective strategies for combating antimicrobial resistance. Understanding the mechanisms behind resistance is crucial in maintaining the efficacy of CZA, a vital tool in the battle against multidrug-resistant infections.IMPORTANCEAs an effective drug for the treatment of carbapenem-resistant Klebsiella pneumoniae, ceftazidime-avibactam (CZA) began to develop resistance in recent years and showed an increasing trend. In order to effectively monitor the resistance rate of CZA and understand its resistance mechanism, we monitored K. pneumoniae for more than 2 years to find CZA-resistant strains. Through comprehensive analysis of the selected CZA-resistant strains, it was found that all the CZA-resistant strains had mutation, which could affect the activity of KPC carbapenemase. This study highlights the importance of proactive surveillance to monitor the emergence of CZA resistance, which highlights the need for ongoing research to develop effective strategies to combat antimicrobial resistance. Understanding the mechanisms behind resistance is critical to maintaining the effectiveness of CZA, an important tool in the fight against multidrug-resistant infections.

Double blaKPC-2 copies quadrupled minimum inhibitory concentration of ceftazidime-avibactam in hospital-derived Klebsiella pneumoniae

To illustrate the genomic and drug resistance traits of the Klebsiella pneumoniae Kpn_XM9, which harbors a transposon (Tn) As1 and was barely susceptible to ceftazidime-avibactam (CZA). Whole-genome sequencing, gene deletion, antimicrobial susceptibility, and conjugation tests were carried out to illustrate the traits of Kpn_XM9. As confirmed by whole-genome sequencing, the Kpn_XM9 harbored a 5,523,536 bp chromosome and five plasmids with lengths being 128,129, 196,512, 84,812, 43,695, and 5,596 bp, respectively. Plasmid p1_Kpn_XM9 (128,219 bp) contained four resistance genes, blaCTX-M-65, blaTEM-1B, rmtB, and two copies of blaKPC-2. Genes blaKPC-2 were bracketed by ISKpn17 and ISKpn16 within a new composite Tn3-like TnAs1. The two tandem repeats, positioned opposite each other, were spaced 93,447 bp apart in p1_Kpn_XM9. Kpn_XM9 belonged to K64 and sequence type (ST) 11. The Kpn_XM9 was resistant to amikacin, aztreonam, ticarcillin/clavulanic acid, piperacillin/tazobactam, ceftazidime, cefepime, imipenem, meropenem, tobramycin, ciprofloxacin, levofloxacin, doxycycline, minocycline, tigecycline, colistin, and trimethoprim/sulfamethoxazole; it was barely susceptible to CZA with a minimum inhibitory concentration of 8/4 µg/mL, which declined to 2/4 µg/mL after a 18,555 bp nucleotide was knocked out and one copy of blaKPC-2 was sustained on p1_Kpn_XM9. Kpn_XM9 had virulence genes encoding Types 1 and 3 fimbriae, four siderophores, and capsular polysaccharide anchoring protein but no genes upregulating capsular polysaccharide synthesis. The Kpn_XM9 presented a classical phenotype with extreme drug resistance. The emergence of double copies of blaKPC-2 in a single plasmid from the predominant ST11 K. pneumoniae represents a new therapeutic challenge.IMPORTANCEWith the wide use of ceftazidime-avibactam against carbapenem-resistant organisms, its resistance is increasingly documented; among the corresponding resistance mechanisms, mutations of blaKPC-2 or blaKPC-3 into other subtypes are dominant to date. However, more copies of blaKPC-2 may also greatly increase the minimum inhibitory concentration of ceftazidime-avibactam, which could be conferred by transposon As1 and insertion sequence 26 and should be of concern.

Emergence of ceftazidime-avibactam resistance in blaKPC-33-harbouring ST11 Klebsiella pneumoniae in a paediatric patient

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses immense threats to the health of infected patients worldwide, especially children. This study reports the infection caused by CRKP in a paediatric intensive care unit (PICU) child and its drug-resistant mutation during the treatment. Twelve Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains were isolated from the child. Broth microdilution method, plasmid transformation assay, and whole genome sequencing (WGS) were performed to investigate the antimicrobial susceptibility, resistance mechanisms, and genetic structural features of CRKPs. The results showed that 12 strains were highly resistant to most available antimicrobial agents. Among them, K. pneumoniae FD11 and K. pneumoniae FD12 were resistant to ceftazidime-avibactam (CZA, MIC >64 mg/L) and restored the carbapenem susceptibility (Imipenem, MIC =0.25 mg/L; Meropenem, MIC =2 mg/L). The patient improved after treatment with CZA in combination with aztreonam. Plasmid transformation assay demonstrated that the blaKPC-33-positive transformant increased MICs of CZA by at least 33-fold and 8-fold compared with the recipient Escherichia coli DH5α and blaKPC-2-positive transformants. WGS analysis revealed that all strains belonged to the ST11-KL64 type and showed highly homologous (3-26 single nucleotide polymorphisms [SNPs]). A single base mutation (G532T) of blaKPC-2 resulted in a tyrosine to aspartic acid substitution at Ambler amino acid position 179 (D179Y), which conferred CZA resistance in K. pneumoniae. This is the first report of a drug-resistant mutation evolving into blaKPC-33 during the treatment of blaKPC-2-positive CRKP in paediatric-infected patients. It advises clinicians that routine sequential antimicrobial susceptibility testing and KPC genotyping are critical during CZA therapy in children infected with CRKP.

Targeted metagenomic assessment reflects critical colonization in battlefield injuries

IMPORTANCE

Microbial contamination in combat wounds can lead to opportunistic infections and adverse outcomes. However, current microbiological detection has a limited ability to capture microbial functional genes. This work describes the application of targeted metagenomic sequencing to profile wound bioburden and capture relevant wound-associated signatures for clinical utility. Ultimately, the ability to detect such signatures will help guide clinical decisions regarding wound care and management and aid in the prediction of wound outcomes.