Title Page
Contents
ABSTRACT 10
Ⅰ. Introduction 12
Ⅱ. Methods 17
1. Selection of the CR-ECC isolates and analysis of clinical characteristics of patients 17
2. Microbiological analysis 18
2-1. Identification of bacteria by hsp60 gene and genotyping 18
2-2. Antibiotic susceptibility test (BMD) and detection of antibiotic resistance genes 21
2-3. Whole genome sequencing (WGS) analysis and transconjugation assays of XDR Enterobacter ludwigii 24
3. Statistical analysis 25
Ⅲ. Results 27
1. Identification and antibiotic susceptibility tests of CR-ECC isolates 27
2. Comparison of antibiotic susceptibility tests between E. hormaechei and non-E. hormaechei isolates 33
3. Carbapenemase-producing CR-ECC 37
4. Multilocus sequence typing of CR-ECC isolates 39
5. Characteristics of colistin-resistant CR-ECC isolates 41
6. Clinical characteristics of patients with isolated CR-ECC 44
6-1. Clinical characteristics of CR-ECC groups classified according to colistin susceptibility 44
6-2. Risk factors of colistin resistant CR-ECC 50
6-3. Characteristics of CR-ECC causing true infection 52
7. Extensively drug-resistant E. ludwigii co-producing mcr-9 and blaIMP₋₁[이미지참조] 54
7-1. Clinical information of the patient and antibiotics resistance 54
7-2. Genotypic properties of the carbapenem-resistant E. ludwigii CRE2104-31 57
7-3. Multicopies of blaIMP₋₁ and aac(6')-Il on the plasmid pCRE2104-31a[이미지참조] 65
7-4. The genetic structure of region B including mcr-9.1 68
7-5. Transmissibility of plasmid pCRE2104-31a and high incompatibility in E. coli J53 68
Ⅳ. Discussion 69
References 81
논문요약 93
Table 1. The similarity of partial hsp60 sequences between reference strains and clinical isolates of subspecies of E. hormaechei. 20
Table 2. Primers used to detect carbapenemase and mcr genes 22
Table 3. Comparison of results of species identification using VITEK MS and heat shock protein 60 gene analysis 29
Table 4. Antibiotics susceptibility test results using broth microdilution methods in carbapenem-resistant Enterobacter cloacae complex isolates(n＝108) 32
Table 5. Antibiotic susceptibility test results of carbapenemase-producing carbapenem-resistant Enterobacter cloacae complex isolates (n＝9) 38
Table 6. Antibiotic susceptibility test results and mcr gene, carbapenemase status of colistin-resistance CR-ECC strains (n＝22). MIC was indicated for colistin, and resistance to other antibiotics was indicated. (S, susceptible; I,... 42
Table 7. Baseline characteristics of patients with colistin non-susceptible carbapenem-resistant Enterobacter cloacae complex versus colistin... 46
Table 8. Risk factors for colistin-resistant carbapenem-resistant Enterobacter cloacae complex 51
Table 9. Species identification of carbapenem-resistant Enterobacter cloacae complex isolates which caused true infection (n＝43) 53
Table 10. Antibiotic susceptibility results of extensively drug-resistant Enterobacter ludwigii CRE2104-31 56
Table 11. Resistance determinants identified in plasmids of E. ludwigii CRE2104-31 by genome analysis. 58
Figure 1. Identification of carbapenem-resistant Enterobacter cloacae complex species by hsp60 gene analysis (n＝108) 28
Figure 2. Antibiotics resistance in carbapenem-resistant Enterobacter cloacae complex isolates (n＝108) 31
Figure 3. Comparison of the antimicrobial resistance rate between carbapenem-resistant E. hormaechei (n＝83) and carbapenem-resistant non- E. hormaechei (n＝25) 35
Figure 5. Multilocus sequence typing with minimum spanning tree of the carbapenem-resistant Enterobacter cloacae complex isolates 40
Figure 6. Structural comparison of plasmid pCRE2104-31a with five other plasmids: pCNR48 of K. pneumoniae(LT994835.1), pD16EC0456-2 of E. coli (CP088601.1), pRIVM_C019770 of K. pneumoniae (CP081340.1),... 61
Figure 7. The comparison of two regions of the plasmid pCRE2104-31a with other sequences. (A) Linear comparison of region A containing the blaIMP₋₁ gene and aac(6')-Il with related mobile elements. Colored arrows...[이미지참조] 63
Figure 8. The presence of five repeats of the blaIMP₋₁ gene and aac(6')-Il on the plasmid was confirmed using long range PCR with conversely designed primer sets. To distinguish PCR products with the same size, we designed the...[이미지참조] 66