PurposeCarbapenem-resistant Enterobacteriaceae (CRE) have been increasingly reported worldwide and pose a serious public threat, but the clinical significance of extended-spectrum β-lactamase (ESBL) production in CRE is not well established.Patients and methodsA retrospective case–case–control study was conducted to identify the clinical characteristics of patients with ESBL-CRE. The susceptibility of isolates obtained from these patients was assessed. The detection of ESBL and carbapenemase-related genes was performed by PCR methods. Predictors of 30-day mortality in patients with ESBL-CRE infection were also identified in our study.ResultsA total of 149 patients with CRE infection caused by Enterobacter cloacae (n=74), Escherichia coli (n=38), and Klebsiella pneumoniae (n=37) were identified in Chongqing, Southwestern China, between January 2011 and December 2014. Of the 35 isolates detected with carbapenemase-related genes, 16 isolates had New Delhi metallo-β-lactamase (NDM), nine isolates had K. pneumoniae carbapenemase (KPC), seven isolates had imipenemase (IMP), and four isolates had oxacillinase (OXA)-1. One strain of enterobacter cloacae carried both NDM-1 and IMP-8 genes. ESBL isolates included the genes CTX-M (72/149), SHV (64/149), and TEM (54/149). All ESBL-CRE isolates exhibited ertapenem resistance, and the rate of cephalosporin resistance was relatively high in general. Independent risk factors for infection with ESBL-CRE included previous exposure to β-lactam antibiotics, transfer from another hospital, and some underlying diseases. In addition, solid tumors, hypoalbuminemia, and central venous catheters were independent predictors of mortality in patients with ESBL-CRE infection.ConclusionPhysicians should understand the peculiar predictors for the identification of these organisms among high-risk patients.

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Background: The emergence and spread of carbapenem-resistant Enterobacter cloacae (CR-ECL) have posed a serious threat to clinical management. This retrospective study assessed the epidemiological characteristics of CR-ECL to explore the risk factors and predictors of mortality in patients with CR-ECL infection. Methods: We performed a retrospective 1:2 case-control study of hospitalized patients from January 2014 to December 2017. A total of 85 consecutive unique CR-ECL strains comprised the case group, and 170 matched patients with carbapenem-susceptible Enterobacter cloacae (CS-ECL) infection at the same period as the control group. Isolates were screened for potential resistance genes by polymerase chain reaction (PCR) and molecular typing was performed by multilocus sequence typing (MLST). Results: The results of drug resistance gene detection showed that blaNDM-1 was the most common carbapenem resistance gene. The MLST results showed that ST51 was the predominant epidemic type, followed by ST88. ICU admission (P<0.001), drainage tube (P=0.002), central venous catheter (P=0.005), and carbapenem exposure (P=0.003) were independent risk factors for CR-ECL infection. Significant predictors for 28-day mortality included solid tumours (P=0.005), septic shock (P=0.019), and mechanical ventilation (P=0.027). Conclusion: Our study indicated that ST51 and ST88, which are closely related, were the predominant epidemic types of CR-ECL producing blaNDM-1 in southwestern China. Strengthening the surveillance of patients with solid tumours, septic shock and mechanical ventilation is an urgent need.

Background: The increasing prevalence of extensively drug-resistant Klebsiella pneumoniae (XDR-KP) poses a serious threat to clinical anti-infective treatment. This retrospective study assessed the molecular epidemiology of and risk factors for infections with XDR-KP to investigate the mechanism of drug resistance and the epidemiological characteristics.Methods: A retrospective 1:2 case-control study was conducted at Chongqing Renji Affiliated Hospital of the Chinese Academy of Sciences University from January 2015 to December 2017. A total of 69 non-repetitive XDR-KP strains were collected. Patients infected with XDR-KP comprised the case group, and 138 matched patients with non-XDR-KP infection at the same site comprised the control group. The chi-square test and logistic regression were performed to evaluate the related risk factors. Molecular typing was performed by multilocus sequence typing (MLST). Potential resistance genes were detected by polymerase chain reaction (PCR) and sequencing. Predictors of 28-day mortality in patients with XDR-KP infection were also identified in our study.Results: Only tigecycline and polymyxin B showed favorable in vitro drug sensitivity tests. These XDR-KP strains had a high prevalence rate (n = 66, 95.7%) of carbapenemase-related drug resistance genes. Among them, KPC-2 was the most frequently detected gene (n = 52, 75.4%). Particularly, all of the isolates harbored multiple drug resistance genes. Epidemiological analysis showed that fifty-eight XDR-KP isolates were resistant strains with the ST-11 genotype. Multivariate logistic regression analysis showed that ICU admission (OR: 3.28, 95% CI: 1.66–6.49, P < 0.001), tracheal cannula (OR: 3.16, 95% CI: 1.48–6.76, P = 0.003), and carbapenem exposure (OR: 3.16, 95% CI: 1.25–7.98, P = 0.015) were independent risk factors for XDR-KP infection. Solid tumors (OR: 7.22, 95% CI: 1.84–28.34, P = 0.005) and septic shock (OR: 9.46, 95% CI: 2.00–44.72, P = 0.005) were independent risk factors for 28-day mortality from XDR-KP infection.Conclusion: This study showed that XDR-KP isolates were highly resistant and exhibited clonal transmission. ST11 was the predominant epidemic type of XDR-KP producing KPC-2 in Southwestern China. Physicians should be aware of these high-risk patients with notable predictive factors for XDR-KP infection. These findings may provide some recommendation for the diagnosis and treatment of patients infected with XDR-KP strains in Southwestern China.