Cluster Differences in Antibiotic Resistance, Biofilm Formation, Mobility, and Virulence of Clinical Enterobacter cloacae Complex

Abstract

Due to the lack of research on the characteristics of different clusters of Enterobacter cloacae complex (ECC), this study aimed to characterize and explore the differences among species of the ECC. An analysis based on hsp60 showed that Enterobacter hormaechei was predominant in ECC. Interestingly, the antibiotic resistance rates of clusters were different, among which E. hormaechei subsp. steigerwaltii (cluster VIII) and Enterobacter cloacae IX (cluster IX) possessed high resistant rates to ciprofloxacin and levofloxacin, but cluster II (Enterobacter kobei) had low resistant rates. Cluster II exhibited a strong biofilm formation ability. Different motility and protease production ability were shown for distinct clusters. A PCR analysis showed that clusters I, III, VI, VIII, and IX carried more virulence genes, while cluster II had fewer. Clusters I, VIII, and IX with high pathogenicity were evaluated using the Galleria mellonella infection model. Thus, the characteristics of resistance, biofilm-forming ability, mobility, and virulence differed among the clusters. The strains were divided into 12 subgroups based on hsp60. The main clusters of ECC clinical strains were I, II, III, VI, VIII, and IX, among which IX, VIII, and I were predominant with high resistance and pathogenicity, and cluster II (E. kobei) was a special taxon with a strong biofilm formation ability under nutrient deficiency, but was associated with low resistance, virulence, and pathogenicity. Hence, clinical classification methods to identify ECC subgroups are an urgent requirement to guide the treatment of clinical infections.

Species identification, antibiotic resistance, and virulence in Enterobacter cloacae complex clinical isolates from South Korea

“…In the present study, diverse species of ECC were identified in patients, including four recently described species ( E. bugandensis , E. chengduensis , E. roggenkampii , and E. mori ; Zhu et al, 2011 ; Doijad et al, 2016 ; Sutton et al, 2018 ; Wu et al, 2019 ). Among the ECC isolates from South Korea, E. hormaechei was the predominant species, as was also the case in a recent study from China ( Liu et al, 2022 ). Unlike the results from China, E. hormaechei subsp.…”

“…Thus, many papers have mistakenly labeled the clinical isolates as E. cloacae or reported different species as ECC indiscriminately ( Hong et al, 2018 ; Sutton et al, 2018 ). Meanwhile, hsp60 gene sequences contain enough variation among the species of ECC for these distinctions to be made, indeed this gene has been recently utilized for ECC species identification ( Hoffmann and Roggenkamp, 2003 ; Liu et al, 2022 ; Sato et al, 2022 ). However, there are few data on the species distribution of ECC and species characteristics ( Liu et al, 2022 ), particularly in South Korea.…”

The Resistance Mechanisms and Clinical Impact of Resistance to the Third Generation Cephalosporins in Species of Enterobacter cloacae Complex in Taiwan

“…In this study, we did not observe a significant difference between E. hormaechei and the other species in terms of demographic data, comorbidities, therapeutic devices and procedures, and clinical outcomes (30-day and 100-day mortality). With regard to the virulence of specific clusters, Liu et al reported the virulence of cluster I strains was significantly higher than that of the other cluster strains according to the results of the Galleria mellonella infection model [ 46 ]. Cluster II ( E. kobei ) has strong biofilm formation ability under nutrient-deficient conditions but is associated with low virulence and pathogenicity [ 46 ].…”

“…With regard to the virulence of specific clusters, Liu et al reported the virulence of cluster I strains was significantly higher than that of the other cluster strains according to the results of the Galleria mellonella infection model [ 46 ]. Cluster II ( E. kobei ) has strong biofilm formation ability under nutrient-deficient conditions but is associated with low virulence and pathogenicity [ 46 ]. However, the case number of cluster I in our study is too small to obtain enough clinical finding.…”

Factors Influencing Biofilm Formation by Salmonella enterica sv. Typhimurium, E. cloacae, E. hormaechei, Pantoea spp., and Bacillus spp. Isolated from Human Milk Determined by PCA Analysis

“…In addition to the temperature and time factors, the study showed that the individual characteristics of the strains significantly affect the production of biofilm. The ability to produce biofilm by E. hormaechei bacteria was confirmed by the studies of Liu et al (2022) [ 49 ]. The differences in biofilm production by B. cereus depending on environmental factors have been described in numerous studies.…”