Abstract
The genus Enterobacter is a member of the ESKAPE group, which contains the major resistant bacterial pathogens. Enterobacter cloacae complex (ECC) has emerged as a clinically significant cause of a wide variety of nosocomial infections. Carbapenem-nonsusceptible Enterobacter cloacae complex (CnsECC) has become an emerging threat to public health but there is still a lack of comprehensive molecular and clinical epidemiological analysis. A total of 157 CnsECC isolates were recovered during October 2011 to August 2017. hsp60 gene sequencing and pulsed-field gel electrophoresis (PFGE) were applied to discriminate the species, genetic clusters and clonal relatedness. All the isolates were subjected to polymerase chain reaction (PCR) analysis for carbapenemase, AmpC-type β-lactamase, and extended spectrum β-lactamase (ESBL) genes. Clinical data were collected on all patients for comparing clinical risks and outcomes between patients with carbapenemase-producing (CP)-CnsECC compared with non-CP-CnsECC infection. The most commonly identified species was E. hormaechei subsp. hoffmannii (47.1%), followed by E. hormaechei subsp. steigerwaltii (24.8%). Different species of CnsECC isolates showed heterogeneity in resistance patterns to piperacillin/tazobactam, cefepime and levofloxacin. In the present study, we observed that E. hormaechei subsp. hoffmannii was characterized with higher cefepime and levofloxacin resistance rate but lower piperacillin/tazobactam resistance rate relative to other species of CnsECC. CP-CnsECC comprised 41.1% (65 isolates) and all of these isolates carried IMP-8. In this study, 98% of patients had antimicrobial therapy prior to culture, with a total of 57/150 (38%) patients being exposed to carbapenems. Chronic pulmonary disease (OR: 2.51, 95% CI: 1.25–5.06), received ventilator support (OR: 5.54, 95% CI: 2.25–12.03), steroid exposure (OR: 3.88, 95% CI: 1.91–7.88) and carbapenems exposure (OR: 2.17, 95% CI: 1.10–4.25) were considered risk factors associated with CP-CnsECC infection. The results suggest that CP-CnsECC are associated with poorer outcomes including in-hospital mortality, 30-day mortality and 100-day mortality. Our study provides insights into the epidemic potential of IMP-8-producing E. cloacae for healthcare-associated infections and underscores the importance of understanding underlying resistance mechanisms of CnsECC to direct antibiotic treatment decisions.
Highlights
The Enterobacter cloacae complex (ECC) is a group of Enterobacteriaceae widely distributed in nature [1,2]
We demonstrated that the most common species of Carbapenem-nonsusceptible Enterobacter cloacae complex (CnsECC) in southern Taiwan was E. hormaechei subsp. hoffmannii (47.1%), which is similar to previous study for ECC isolates co-resistant to carbapenem and colistin in southeast China [3]
Our study showed the predominant mechanism of CnsECC isolates were carbapenemase production (41.4%) and AmpC overproduction (37.3%)
Summary
The Enterobacter cloacae complex (ECC) is a group of Enterobacteriaceae widely distributed in nature [1,2]. Molecular and genomic techniques are needed to identify the ECC species precisely. Sequencing of the heat shock protein 60 (hsp60) gene, which can discriminate of this complex into 13 genetic clusters (C-I to CXIII) appears to be a valuable tool to identify of ECC species [3]. Despite the fact that misidentification of ECC species has little impact on antibiotic therapy previously, as the species of the ECC have the similar antibiotic resistance profiles, these molecular approaches still have been used recently for precise identification of the species in the ECC for understanding the epidemiology, pathogenesis, and microbiological features [10]
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