ABSTRACT
Objective:To analyze the characteristics of drug resistance genes in a Klebsiella pneumoniae strain coproducing carbapenemases KPC-2 and NDM-5. Methods:Klebsiella pneumoniae KPN-hnqyy was separated from the stool specimen of a patient in the Hematology Department of Affiliated Cancer Hospital of Zhengzhou University. The strain was identified with a BD Phenix-M50 automated microbiology system and the minimum inhibitory concentration against the strain was measured as well. The genotypes of the carbapenemases were tested by enzyme immunochromatographic assay and PCR method. The transferability of related plasmids was analyzed by conjugation test. Whole-genome sequencing of the strain was conducted using PacBio and Illumina platforms. The MLST type, resistance gene and plasmid type of the strain were retrieved in BacWGSTdb. The genome and open reading frame sequence of the strain were compared using Easyfig_2.2.3. Visual cycle graphs were generated using BRIG v0.95. Results:Klebsiella pneumoniae KPN-hnqyy was resistant to carbapenem antibiotics. It belonged to ST11 and carried two carbapenemase genes of blaKPC-2 and blaNDM-5. The conjugant only harbored the blaKPC-2 gene. Whole-genome sequencing revealed that the strain contained one chromosome and three plasmids. Its chromosome genome shared more than 99.9% similarity with that of Klebsiella pneumonia KP69 and KP19-2029. Moreover, a similar IncR and IncFⅠ resistance gene fusion region was contained in different types of plasmids carried by them: the blaKPC-2 gene was located in a structure—which evolved from the Tn3-△Tn4401-Tn1721/Tn1722 sequence—inside this fusion region with its ends inserted into the transposase IS26 gene; the blaNDM-5 gene was located on a transposon containing the special plasmids of the insertion fragment in phages, with its ends inserted into the transposase IS26 gene too. Conclusions:The IncR and IncFⅡ resistance gene fusion region of blaKPC-2 carried by Klebsiella pneumoniae ST11 might be widely coexistent with the chromosomal genome. The blaNDM-5 gene carried by special plasmids might be accidentally obtained through gene recombination mediated by transposable element IS26. The wide transmission of Klebsiella pneumoniae ST11 carrying the blaKPC-2 gene in China and its ability to obtain other carbapenemase genes through transposable element IS26 were well worth attention.
ABSTRACT
Objective:To analyze the characteristics of plasmids in KPC-2-producing Serratia marcescens ( S. marcescens) isolates. Methods:Four carbapenem-resistant S. marcescens strains were isolated from four patients admitted to the hepatobiliary ward of Affiliated Cancer Hospital of Zhengzhou University in 2016. BD Phenix-100 was used to identify the strains and detect the minimum inhibitory concentrations (MICs). Homology analysis was performed using pulsed-field gel electrophoresis (PFGE). The modified Hodge test was used to detect the phenotypes of carbapenemase. PCR and gene sequencing were used to detect the types of carbapenem resistance genes. The transferability of plasmids was detected by conjugation test. The characteristics of plasmids were analyzed by genomic alignment method after whole genome sequencing. DNAMAN V9 software was used to compare the amino acid sequences of the replication initiation proteins. A phylogenetic tree was constructed with neighbor-joining method using MEGA7.0. Results:All of the four S. marcescens strains were resistant to carbapenem antibiotics. They were highly homologous according to PFGE. Hodge test results were all positive and the carbapenemase genotype was blaKPC-2. Conjugation test results were positive. The plasmid was a circular DNA of 42 742 bp in length. It had the similar skeleton of incX6 plasmid and the similar amino acid sequence of replication initiation protein. Moreover, it and incX6 plasmid were at the same node in the phylogenetic tree. The blaKPC-2 was located in the core of drug resistance, which was composed of insertion elements including Tn3 family transposons, recombinant enzyme genes, △ISKpn6 and ISKpn27. Conclusions:The plasmid was incX6-like. The blaKPC-2 gene was located in the transposon of △Tn6296. More attention should be paid to the bacteria carrying KPC-2 in incX plasmids.
ABSTRACT
Objects: To clarify the risk factors of candidemia and to assess the clinical differences that may exist between infection with Candida parapsilosis and that with other Candida species in cancer patients. To statistically analyze the clinical characteristics of Candi-da albicans candidemia and C. parapsilosis candidemia and risk factors for their infections. We aimed at a timely intervention through this type of analysis to avoid susceptible factors and improve the prognosis of patients with candidemia. Methods: We retrospectively included 323 patients with candidemia in Affiliated Cancer Hospital of Zhengzhou University between March 2012 and February 2018 and analyzed the clinical characteristics of these patients to establish the risk factors of candidemia. We performed a comparative anal-ysis of the clinical characteristics of C. parapsilosis infections and non-parapsilosis Candida spp. infections and of C. albicans infections and non-albicans Candida spp. infections. In addition, drug sensitivity tests and analyses were performed with the common antifungal drugs used in Candida infections by a micro-broth dilution method. The statistical software SPSS version 22 was used for the analyses. Results: A total of 323 patients were enrolled and analyzed in this study. Of the isolates, 34.37% were C. albicans and 65.63% were non-albicans Candida spp. Multivariate regression analysis showed that the following factors were associated with the occurrence of C. parapsilosis candidemia: parenteral nutrition (P<0.001), neutropenia (P<0.001), history of receiving chemotherapy (P=0.002), and history of previous antifungal use (P<0.001). Parenteral nutrition was found to be an independent risk factor for C. albicans candi-demia (OR=0.183; 95%CI:0.098?0.340; P<0.001). Conclusions: C. parapsilosis was found to be the primary pathogen in cancer patients with candidemia. Total parenteral nutrition in the intensive care unit at diagnosis and abdominal surgery were independent risk factors of candidemia, and parenteral nutrition was an independent risk factor of C. parapsilosis candidemia. At present, C. parapsilosis is sur-passing C. albicans as the main pathogen of candidemia in cancer patients at our hospital. This study emphasizes the need to assess the possible risk factors for candidemia in cancer patients and aims at strengthening and developing a hospital-based control strategy to prevent the spread of candidemia.