Project description:Background: Enterobacter cloacae complex (ECC) is a common opportunistic pathogen and is responsible for causing various infections in humans. Owing to its inducible chromosomal AmpC β-lactamase (AmpC), ECC is inherently resistant to the 1st- and 2nd- generation cephalosporins. However, whether β-lactams antibiotics enhance ECC resistance remains unclear. Results: In this study, we found that subinhibitory concentrations (SICs) of cefazolin (CFZ) and imipenem (IMP) can advance the expression of AmpC and enhance its resistance towards β-lactams through NagZ in Enterobacter cloacae (EC). Further, AmpC manifested a substantial upregulation in EC in response to SICs of CFZ and IMP. In nagZ knockout EC (ΔnagZ), the resistance to β-lactam antibiotics was rather weakened and the effect of CFZ and IMP on AmpC induction was completely abrogated. NagZ ectopic expression can rescue the induction effects of CFZ and IMP on AmpC and increase ΔnagZ resistance. More importantly, CFZ and IMP have the potential to induce the expression of AmpR's target genes in a NagZ-dependent manner. Conclusions: Our findings suggest that NagZ is a critical determinant for CFZ and IMP to promote AmpC expression and resistance and that CFZ and IMP should be used with caution since they may aggravate ECC resistance. At the same time, this study further improves our understanding of resistance mechanisms in ECC.
Project description:Background: Efflux pumps are important cofactors for carbapenem resistance in Enterobacter cloacae. The regulatory mechanism by which asmA influences efflux pump function in this species remains unclear. This study explored the regulatory role of asmA on efflux pumps in carbapenem-resistant Enterobacter cloacae. Results: Sixteen carbapenem-resistant Enterobacter cloacae were collected. All strains carried blaNDM, 87.5% of which were blaNDM-1 and 12.5% were blaNDM-5. PAβN had weak inhibition on carbapenem resistance in ST78 and strong inhibition in ST2260. ST2260(CY-8) was still resistant to carbapenems after elimination of blaNDM and could be inhibited by PAβN. However, ST78(CY-9) lost its resistance to carbapenems. Knockout of asmA reduced the MIC of ST2260 by 16-fold. ST78 showed no such changes. Growth curves revealed impaired growth only in ST2260ΔasmA. Transcriptomics/qRT-PCR revealed no significantly altered acrAB-tolC or marA expression in either strain. Membrane proteomics detected AcrB loss specifically in ST2260ΔasmA. The loss of asmA affected a wide range of membrane proteins, especially OmpW. Molecular docking predicted that AsmA could bind to AcrB, with stronger binding energy in ST78. The buried area of the CY-8 model involved 110 contact residues, while the number of contacts of the CY-9 model increased to 144. The AsmA chain of the two models had 46 common contact residues, and the AcrB chain had 60 common contact residues. AcrB of ST78 generally carries the I277V mutation. Conclusion: asmA is highly conserved in Enterobacter cloacae. It has functional heterogeneity in different ST types. In ST2260, asmA can affect efflux pump-mediated carbapenem resistance. AsmA can regulate AcrAB-TolC not by affecting marA. It is predicted that AsmA can maintain the carbapenem resistance of Enterobacter cloacae ST2260 by helping AcrB anchor to the inner membrane. The difference in carbapenem resistance mediated by efflux pumps between ST78 and ST2260 suggests that ST78 commonly carries the AcrB I277V mutation, which is a key site for efflux of β-lactams.
Project description:Members of the ECC complex (E. cloacae, E. hormaechei) and Klebsiella aerogenes which was previously known as Enterobacter aerogenes. Genome sequencing and assembly
Project description:Reducing bacterial pathogen contamination not only improves overall global public health but also diminishes food waste and loss. The use of lytic bacteriophages (phages) that infect and kill bacteria could be a beneficial tool for suppressing bacterial growth during dairy products storage time. Four Enterobacter cloacae (E. cloacae) complex isolates which were previously isolated from contaminated dairy products were used to identify lytic phages in wastewater. Phages specific to multi-drug resistant (MDR) E. cloacae complex 6AS1 were isolated from local sewage. Two novel phages vB_EclM-EP1 and vB_EclM-EP2 were identified as myoviral particles and have double-stranded DNA genome. Their host range and lytic capabilities were detected using spot test and efficiency of plating (EOP) against several bacterial isolates. The phages had a latent period of 30 min, and a large burst size of about 100 and 142 PFU/cell for vB_EclM-EP1 and vB_EclM-EP2, respectively. Both phages were viable at pH ranging 5-9 and stable at 70 °C for 60 min. The individual phages and their cocktail preparations (vB_EclM-EP1 and vB_EclM-EP2) reduced and inhibited the growth of E. cloacae complex 6AS1 during challenge test in milk and yogurt samples. These results indicate that the E. cloacae complex-specific phages (vB_EclM-EP1 and vB_EclM-EP2) have a potential application as microbicidal agents in packaged milk and milk derivatives during storage time. In addition, our environment is a rich sources of lytic phages which have potential use in eliminating multidrug-resistant isolates in food industry as well as in biocontrol.
Project description:Heteroresistance in bacteria describes a subpopulational phenomenon of transient antibiotic resistance variation among cells of a generally susceptible population. Here, we investigated the molecular mechanisms and phenotypic characteristics underlying heteroresistance to ceftazidime (CAZ) in a clinical Enterobacter cloacae complex strain (ECC). We identified a plasmid-borne gene duplication-amplification (GDA) event of a region harboring an ampC gene encoding a β-lactamase blaDHA-1 as the key determinant of heteroresistance. Individual colonies exhibited variations in the copy number of the genes resulting in resistance level variation which correlated with growth onset (lag times) and growth rates in the presence of CAZ, analysed in linear models. GDA copy number heterogeneity occurred within single resistant colonies, demonstrating heterogeneity of GDA on the single-cell level. The interdependence between GDA, lag time and antibiotic treatment and the strong plasticity underlying heteroresistance underlines the high risk for misdetection of antimicrobial heteroresistance and subsequent treatment failure.
Project description:Enterobacter cloacae is an important nosocomial pathogen. Here, we report the completion of the genome sequence of E. cloacae ATCC 13047, the type strain of E. cloacae subsp. cloacae. Multiple sets of virulence determinant and heavy-metal resistance genes have been found in the genome. To the best of our knowledge, this is the first complete genome sequence of the E. cloacae species.
Project description:Enterobacter cloacae subsp. cloacae strain ENHKU01 is a Gram-negative endophyte isolated from a diseased pepper (Capsicum annuum) plant in Hong Kong. This is the first complete genome sequence report of a plant-endophytic strain of E. cloacae subsp. cloacae.
Project description:We report draft genomes of Enterobacter cloacae strain S611, an endophytic bacterium isolated from surface-sterilized germinating wheat seeds. We present the assembly and annotation of its genome, which may provide insights into the metabolic pathways involved in adaptation.
Project description:BackgroundIsolates of the Enterobacter cloacae complex have been increasingly isolated as nosocomial pathogens, but phenotypic identification of the E. cloacae complex is unreliable and irreproducible. Identification of species based on currently available genotyping tools is already superior to phenotypic identification, but the taxonomy of isolates belonging to this complex is cumbersome.Methodology/principal findingsThis study shows that multilocus sequence analysis and comparative genomic hybridization based on a mixed genome array is a powerful method for studying species assignment within the E. cloacae complex. The E. cloacae complex is shown to be evolutionarily divided into two clades that are genetically distinct from each other. The younger first clade is genetically more homogenous, contains the Enterobacter hormaechei species and is the most frequently cultured Enterobacter species in hospitals. The second and older clade consists of several (sub)species that are genetically more heterogeneous. Genetic markers were identified that could discriminate between the two clades and cluster 1.Conclusions/significanceBased on genomic differences it is concluded that some previously defined (clonal and heterogenic) (sub)species of the E. cloacae complex have to be redefined because of disagreements with known or proposed nomenclature. However, further improved identification of the redefined species will be possible based on novel markers presented here.