Motility behavior and physiological response mechanisms of aerobic denitrifier, Enterobacter cloacae strain HNR under high salt stress: Insights from individual cells to populations.

The motility behaviors at the individual-cell level and the collective physiological responsive behaviors of aerobic denitrifier, Enterobacter cloacae strain HNR under high salt stress were investigated. The results revealed that as salinity increased, electron transport activity and adenosine triphosphate content decreased from 15.75 µg O2/g/min and 593.51 mM/L to 3.27 µg O2/g/min and 5.34 mM/L, respectively, at 40 g/L, leading to a reduction in the rotation velocity and vibration amplitude of strain HNR. High salinity stress (40 g/L) down-regulated genes involved in ABC transporters (amino acids, sugars, metal ions, and inorganic ions) and activated the biofilm-related motility regulation mechanism in strain HNR, resulting in a further decrease in flagellar motility capacity and an increase in extracellular polymeric substances secretion (4.08 mg/g cell of PS and 40.03 mg/g cell of PN at 40 g/L). These responses facilitated biofilm formation and proved effective in countering elevated salt stress in strain HNR. Moreover, the genetic diversity associated with biofilm-related motility regulation in strain HNR enhanced the adaptability and stability of the strain HNR populations to salinity stress. This study enables a deeper understanding of the response mechanism of aerobic denitrifiers to high salt stress.

Comparative genome analyses uncovered the cadmium resistance mechanism of enterobacter cloacae.

Cadmium (Cd) can be transported into plants from polluted soils and may cause animal and human diseases through food chains, which requires the development of highly efficient methods for soil Cd remediation. Although we isolated an Enterobacter cloacae strain Cu6 with Cd resistance, this strain cannot be used for soil Cd remediation due to its lower resistance. Here, we domesticated Cu6 and obtained a highly Cd-resistant strain, LPY6, and found that this strain can attenuate the toxic effects of Cd on wheat seedling growth. We deciphered the high Cd-resistance mechanism of LPY6 by genome comparative and genetic analysis. Compared with Cu6, 75 genes were mutated in LPY6. Thirty-four of these genes were deleted, and 41 had single nucleotide polymorphisms (SNPs). Most of these mutated proteins are involved in basic metabolism, substrate transport, stress response and formate and hydrogen metabolism. RNA quantitative analysis and promoter activity assays showed that the transcription or mRNA levels of two operons (cadA and norVW) in these mutated genes were regulated by Cd, zinc (Zn) or lead (Pb) ions, suggesting that these two operons might be required for Cd, Zn or Pb resistance. Expression of cadA and norVW operons in LPY6 partially recovered Cd susceptibility, demonstrating that CadA and NorVW are involved in Cd resistance in E. cloacae. Our findings illustrate that E. cloacae acquires Cd resistance through different pathways and lay a foundation for developing highly efficient methods for soil Cd remediation.

Evaluation of anti-malaria potency of wild and genetically modified Enterobacter cloacae expressing effector proteins in Anopheles stephensi.

BACKGROUND: Malaria is one of the most lethal infectious diseases in tropical and subtropical areas of the world. Paratransgenesis using symbiotic bacteria offers a sustainable and environmentally friendly strategy to combat this disease. In the study reported here, we evaluated the disruption of malaria transmission in the Anopheles stephensi-Plasmodium berghei assemblage using the wild-type (WT) and three modified strains of the insect gut bacterium, Enterobacter cloacae. METHODS: The assay was carried out using the E. cloacae dissolvens WT and three engineered strains (expressing green fluorescent protein-defensin (GFP-D), scorpine-HasA (S-HasA) and HasA only, respectively). Cotton wool soaked in a solution of 5% (wt/vol) fructose + red dye (1/50 ml) laced with one of the bacterial strains (1 × 109cells/ml) was placed overnight in cages containing female An. stephensi mosquitoes (age: 3-5 days). Each group of sugar-fed mosquitoes was then starved for 4-6 h, following which time they were allowed to blood-feed on P. berghei-infected mice for 20 min in the dark at 17-20 °C. The blood-fed mosquitoes were kept at 19 ± 1 °C and 80 ± 5% relative humidity, and parasite infection was measured by midgut dissection and oocyst counting 10 days post-infection (dpi). RESULTS: Exposure to both WT and genetically modified E. cloacae dissolvens strains significantly (P < 0.0001) disrupted P. berghei development in the midgut of An. stephensi, in comparison with the control group. The mean parasite inhibition of E. cloacaeWT, E. cloacaeHasA, E. cloacaeS-HasA and E. cloacaeGFP-D was measured as 72, 86, 92.5 and 92.8 respectively. CONCLUSIONS: The WT and modified strains of E. cloacae have the potential to abolish oocyst development by providing a physical barrier or through the excretion of intrinsic effector molecules. These findings reinforce the case for the use of either WT or genetically modified strains of E. cloacae bacteria as a powerful tool to combat malaria.

Institutional outbreak involving multiple clades of IMP-producing Enterobacter cloacae complex sequence type 78 at a cancer center in Tokyo, Japan.

BACKGROUND: Information about the clinical and microbiological characteristics of IMP-producing Enterobacterales has been limited. Here, we describe an institutional outbreak of IMP-producing Enterobacter cloacae complex (ECC) involving multiple clades of ECC sequence type (ST) 78 strains. METHODS: Antimicrobial susceptibility testing, whole-genome sequencing, and conjugation experiments of 18 IMP-producing ECC strains isolated during four-year study period were performed. Species and subspecies were determined by average nucleotide identity analysis and clonal relatedness of the isolates was analyzed with multilocus sequence typing and core-genome single nucleotide polymorphism (SNP) analysis. Relevant clinical information was extracted from medical records. RESULTS: Fourteen of 18 IMP-producing ECC isolates were determined as Enterobacter hormaechei ST78. Sixteen isolates, including 13 isolates belonging to ST78, carried blaIMP-1 in In316-like class 1 integron and also carried IncHI2 plasmids. Conjugation experiments were successful for 12 isolates carrying blaIMP-1 on IncHI2 plasmids and for an isolate carrying blaIMP-11 on an IncL/M plasmid. Although isolation of ST78 strains was clustered in a 14-months period suggesting nosocomial transmission, these strains were subdivided into three clades by SNP analysis: clade A (n = 10), clade B (n = 1), clade C (n = 3). A part of clonal relatedness was unexpected by the epidemiological information at the time of isolation of the strains. Most of the IMP-producing ECC strains were susceptible to non-ß-lactam antibiotics and had relatively low minimum inhibitory concentrations to carbapenems (≤4 µg/mL). Five of six infections caused by IMP-producing ECC were treated successfully. CONCLUSIONS: Whole-genome sequencing analysis revealed the outbreak was caused by three different clades of ST78 strains, where patients had favorable treatment outcome of the infections compared with that caused by Enterobacterales producing other carbapenemases, possibly due to their non-multidrug-resistant phenotype.

Characterization of Enterobacter cloacae BAGM01 Producing a Thermostable and Alkaline-Tolerant Rhamnolipid Biosurfactant from the Gulf of Mexico.

The search for novel biosurfactants (Bs) requires the isolation of microorganisms from different environments. The Gulf of Mexico (GoM) is a geographical area active in the exploration and exploitation of hydrocarbons. Recent metagenomic and microbiologic studies in this area suggested a potential richness for novel Bs microbial producers. In this work, nineteen bacterial consortia from the GoM were isolated at different depths of the water column and marine sediments. Bs production from four bacterial consortia was detected by the CTAB test and their capacity to reduce surface tension (ST), emulsion index (EI24), and hemolytic activity. These bacterial consortia produced Bs in media supplemented with kerosene, diesel, or sucrose. Cultivable bacteria from these consortia were isolated and identified by bacterial polyphasic characterization. In some consortia, Enterobacter cloacae was the predominant specie. E. cloacae BAGM01 presented Bs activity in minimal medium and was selected to improve its Bs production using a Taguchi and Box-Behnken experimental design; this strain was able to grow and presented Bs activity at 35 g L-1 of NaCl. This Bs decreased ST to around 34.5 ± 0.56 mNm-1 and presented an EI24 of 71 ± 1.27%. Other properties of this Bs were thermal stability, stability in alkaline conditions, and stability at high salinity, conferring important and desirable characteristics in multiple industries. The analysis of the genome of E. cloacae BAGM01 showed the presence of rhlAB genes that have been reported in the synthesis of rhamnolipids, and alkAB genes that are related to the degradation of alkanes. The bioactive molecule was identified as a rhamnolipid after HPLC derivatization, 1H NMR, and UPLC-QTOF-MS analysis.

Degradation of low-density poly ethylene (LDPE) by Enterobacter cloacae AKS7: a potential step towards sustainable environmental remediation.

Plastics composed of polyethylene are non-biodegradable and are mostly harmful to the environment. Literature studies documented that the extent of microbial degradation of low-density polyethylene (LDPE) seems to be insufficient and the underlying mechanisms of such degradation remain unexplored. In the present study, efforts were given to degrade LDPE by a recently isolated bacteria Enterobacter cloacae AKS7. Scanning electron microscopic (SEM) image, tensile strength, and weight loss analysis confirmed the efficient degradation of LDPE by AKS7. To investigate the mechanism, it was observed that with the progression of time, the extent of microbial colonization got increased considerably over the LDPE surface. It was also observed that the organism (AKS7) gradually increased the secretion of extracellular polymeric substances (EPS) suggesting the formation of efficient biofilm over the LDPE surface. Furthermore, to comprehend the role of cell-surface hydrophobicity towards biofilm formation, two mutants of AKS7 were screened that showed a considerable reduction in cell-surface hydrophobicity in contrast to its wild type. The result showed that the mutants revealed compromised LDPE degradation than wild-type cells of AKS7. Further investigation revealed that the mutant cells of AKS7 were incapable of adhering to LDPE in contrast to wild-type cells. Thus, the results demonstrated that the cell-surface hydrophobicity of AKS7 favors the development of microbial biofilm over LDPE that leads to the enhanced degradation of LDPE by AKS7. Therefore, the organism holds the assurance to be considered as a promising bio-remediating agent for the sustainable degradation of polythene-based hazardous waste.

Emergence and Spread of Carbapenem-Resistant and Aminoglycoside-Panresistant Enterobacter cloacae Complex Isolates Coproducing NDM-Type Metallo-ß-Lactamase and 16S rRNA Methylase in Myanmar.

Surveillance of 10 hospitals and a regional public health laboratory in Myanmar identified 31 isolates of carbapenem-resistant Enterobacter cloacae complex harboring blaNDM-type Of these isolates, 19 were highly resistant to aminoglycosides and harbored one or more genes encoding 16S rRNA methylases, including armA, rmtB, rmtC, and/or rmtE Of the 19 isolates, 16 were Enterobacter xiangfangensis ST200, with armA on the chromosome and a plasmid harboring blaNDM-1 and rmtC, indicating that these isolates were clonally disseminated nationwide in Myanmar.IMPORTANCE The emergence of multidrug-resistant E. cloacae complex has become a public health threat worldwide. E. xiangfangensis is a recently classified species belonging to E. cloacae complex. Here, we report a clonal dissemination of multidrug-resistant E. xiangfangensis ST200 producing two types of New Delhi metallo-ß-lactamase (NDM-type MBL), NDM-1 and -4, and three types of 16S rRNA methylases, ArmA, RmtC, and RmtE, in hospitals in Myanmar. The observation of these multidrug-resistant E. xiangfangensis ST200 isolates stresses the urgency to continue molecular epidemiological surveillance of these pathogens in Myanmar and in South Asian countries.

A recurrent and transesophageal echocardiography-associated outbreak of extended-spectrum ß-lactamase-producing Enterobacter cloacae complex in cardiac surgery patients.

Background: We report a recurrent outbreak of postoperative infections with extended-spectrum ß-lactamase (ESBL)-producing E. cloacae complex in cardiac surgery patients, describe the outbreak investigation and highlight the infection control measures. Methods: Cases were defined as cardiac surgery patients in Ghent University Hospital who were not known preoperatively to carry ESBL-producing E. cloacae complex and who postoperatively had a positive culture for this multiresistant organism between May 2017 and January 2018. An epidemiological investigation, including a case-control study, and environmental investigation were conducted to identify the source of the outbreak. Clonal relatedness of ESBL-producing E. cloacae complex isolates collected from case patients was assessed using whole-genome sequencing-based studies. Results: Three separate outbreak episodes occurred over the course of 9 months. A total of 8, 4 and 6 patients met the case definition, respectively. All but one patients developed a clinical infection with ESBL-producing E. cloacae complex, most typically postoperative pneumonia. Overall mortality was 22% (4/18). Environmental cultures were negative, but epidemiological investigation pointed to transesophageal echocardiography (TEE) as the outbreak source. Of note, four TEE probes showed a similar pattern of damage, which very likely impeded adequate disinfection. The first and second outbreak episode were caused by the same clone, whereas a different strain was responsible for the third episode. Conclusions: Health professionals caring for cardiac surgery patients and infection control specialists should be aware of TEE as possible infection source. Caution must be exercised to prevent and detect damage of TEE probes.

Nosocomial outbreak of extended-spectrum ß-lactamase-producing Enterobacter cloacae among cardiothoracic surgical patients: causes and consequences.

BACKGROUND: Enterobacteriaceae are recognized as leading pathogens of healthcare-associated infections. AIM: To report the investigation of a nosocomial outbreak of extended-spectrum ß-lactamase-producing Enterobacter cloacae affecting cardiothoracic surgery patients in a Belgian academic hospital. METHODS: Cases were defined based on epidemiological and microbiological investigations, including molecular typing using repetitive element-based polymerase chain reaction and multi-locus sequence typing. Case-control studies followed by field evaluations allowed the identification of a possible reservoir, and the retrospective assessment of human and financial consequences. FINDINGS: Over a three-month period, 42 patients were infected or colonized by CTX-M-15-producing E. cloacae strains that belonged to the same clonal lineage. Acquisition mainly occurred in the intensive care unit (N = 23) and in the cardiothoracic surgery ward (N = 16). All but one patient had, prior to acquisition, undergone a cardiothoracic surgical procedure, monitored by the same transoesophageal echocardiography (TOE) probe in the operating room. Despite negative microbiological culture results, the exclusion of the suspected probe resulted in rapid termination of the outbreak. Overall, the outbreak was associated with a high mortality rate among infected patients (40%) as well as significant costs (€266,550). CONCLUSION: The outbreak was indirectly shown to be associated with the contamination of a manually disinfected TOE probe used per-operatively during cardiothoracic surgery procedures, because withdrawal of the putative device led to rapid termination of the outbreak.

Genomic features of a multidrug-resistant Enterobacter cloacae ST279 producing CTX-M-15 and AAC(6')-Ib-cr isolated from fatal infectious stomatitis in a crossed pit viper (Bothrops alternatus).

OBJECTIVES: The widespread dissemination of extended-spectrum ß-lactamase-producing Enterobacteriaceae has become a major issue in veterinary medicine. However, until now, there has been no report of bacteria with such a phenotype in infected snakes. The aim of this study was to report the first draft genome sequence of an Enterobacter cloacae isolate (SERP1) recovered from a snake with infectious stomatitis. METHODS: The whole genome of E. cloacae strain SERP1 was sequenced on an Illumina NextSeq platform and was de novo assembled using CLC NGS Cell v.10. Data analysis was performed using online tools from the Center of Genomic Epidemiology. RESULTS: The genome size was calculated at 4966856bp, containing a total of 4796 protein-coding sequences. The strain was assigned to sequence type 279 (ST279) and, besides the clinically relevant blaCTX-M-15 and aac(6')-Ib-cr genes, it also presented resistance genes to ß-lactams, aminoglycosides, phenicols, sulphonamides, tetracyclines, trimethoprim, quinolones and fosfomycin. CONCLUSION: These data offer novel information regarding multidrug-resistant E. cloacae dissemination in wild animals and might contribute to further comparative genomic analysis.

Crystal structures and biochemical characterization of DNA sliding clamps from three Gram-negative bacterial pathogens.

Bacterial sliding clamps bind to DNA and act as protein-protein interaction hubs for several proteins involved in DNA replication and repair. The partner proteins all bind to a common pocket on sliding clamps via conserved linear peptide sequence motifs, which suggest the pocket as an attractive target for development of new antibiotics. Herein we report the X-ray crystal structures and biochemical characterization of ß sliding clamps from the Gram-negative pathogens Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacter cloacae. The structures reveal close similarity between the pathogen and Escherichia coli clamps and similar patterns of binding to linear clamp-binding motif peptides. The results suggest that linear motif-sliding clamp interactions are well conserved and an antibiotic targeting the sliding clamp should have broad-spectrum activity against Gram-negative pathogens.

Surfing Motility: a Conserved yet Diverse Adaptation among Motile Bacteria.

Bacterial rapid surfing motility is a novel surface adaptation of Pseudomonas aeruginosa in the presence of the glycoprotein mucin. Here, we show that other Gram-negative motile bacterial species, including Escherichia coli, Salmonella enterica, Vibrio harveyi, Enterobacter cloacae, and Proteus mirabilis, also exhibit the physical characteristics of surfing on the surface of agar plates containing 0.4% mucin, where surfing motility was generally more rapid and less dependent on medium viscosity than was swimming motility. As previously observed in Pseudomonas aeruginosa, all surfing species exhibited some level of broad-spectrum adaptive resistance, although the antibiotics to which they demonstrated surfing-mediated resistance differed. Surfing motility in P. aeruginosa was found to be dependent on the quorum-sensing systems of this organism; however, this aspect was not conserved in other tested bacterial species, including V. harveyi and S. enterica, as demonstrated by assaying specific quorum-sensing mutants. Thus, rapid surfing motility is a complex surface growth adaptation that is conserved in several motile bacteria, involves flagella, and leads to diverse broad-spectrum antibiotic resistance, but it is distinct in terms of dependence on quorum sensing.IMPORTANCE This study showed for the first time that surfing motility, a novel form of surface motility first discovered in Pseudomonas aeruginosa under artificial cystic fibrosis conditions, including the presence of high mucin content, is conserved in other motile bacterial species known to be mucosa-associated, including Escherichia coli, Salmonella enterica, and Proteus mirabilis Here, we demonstrated that key characteristics of surfing, including the ability to adapt to various viscous environments and multidrug adaptive resistance, are also conserved. Using mutagenesis assays, we also identified the importance of all three known quorum-sensing systems, Las, Rhl, and Pqs, in P. aeruginosa in regulating surfing motility, and we also observed a conserved dependence of surfing on flagella in certain species.

Complete Sequence of pCY-CTX, a Plasmid Carrying a Phage-Like Region and an ISEcp1-Mediated Tn2 Element from Enterobacter cloacae.

A plasmid pCY-CTX carrying a phage-like backbone from an extensively drug-resistant Enterobacter cloacae strain Guangzhou-ECL001 (previously known as CY01) was identified in this study. By Illumina MiSeq 2 × 250-bp paired-end sequencing, de novo assembly, and PCR, full sequence of pCY-CTX was obtained. Plasmid pCY-CTX was a circular plasmid with a length of 116,700 bp, harboring 136 putative open reading frames with the average G + C content of 50.8%. The backbone of pCY-CTX showed high identity to previously reported phage-like plasmid pHCM2 and phage SSU5. In addition, pCY-CTX contained a distinctive ISEcp1-mediated Tn2 region with two resistance genes blaTEM-1 and blaCTX-M-3. Transposition unit "ISEcp1- blaCTX-M-3- orf477" was inserted into the Tn2 structure, dividing Tn2 into two parts. This represents the first identification of a plasmid carrying a phage-like backbone and a distinctive ISEcp1-mediated Tn2 region within blaTEM-1 and blaCTX-M-3 in clinical E. cloacae. The finding of phage-like regions located in plasmids provides a new perspective in gene transfer associated with antimicrobial resistance.

Detection of virulence and ß-lactamase encoding genes in Enterobacter aerogenes and Enterobacter cloacae clinical isolates from Brazil

ABSTRACT Enterobacter cloacae and E. aerogenes have been increasingly reported as important opportunistic pathogens. In this study, a high prevalence of multi-drug resistant isolates from Brazil, harboring several β-lactamase encoding genes was found. Several virulence genes were observed in E. aerogenes, contrasting with the E. cloacae isolates which presented none.

Clinical and Molecular Epidemiology of Carbapenem-Resistant Enterobacteriaceae Among Adult Inpatients in Singapore.

BACKGROUND: Since 2010, the incidence of carbapenem-resistant Enterobacteriaceae (CRE) has been increasing in Singapore. We analyzed the clinical and molecular epidemiology of CRE among adult inpatients in Singapore. METHODS: Quarterly incidence of unique subjects (per 100000 patient-days) with positive clinical and surveillance cultures for CRE were estimated based on mandatory data submitted to the National Public Health Laboratory by public hospitals between 2010 and 2015. CRE-positive adult inpatients were prospectively recruited from 6 public sector hospitals between December 2013 and April 2015. Subjects answered a standardized epidemiologic questionnaire and provided samples for this study. Further clinical information was extracted from subjects' electronic medical records. Whole-genome sequencing was performed on study isolates to determine transmission clusters. RESULTS: Incidence of CRE clinical cultures among adult inpatients plateaued from 2013 (range: 7.73 to 10.32 per 100000 patient-days) following an initial increase between 2010 and end-2012. We prospectively recruited 249 subjects. Their median age was 65 years, 108 (43%) were female, and 161 (64.7%) had carbapenemase-producing Enterobacteriaceae (CPE). On multivariate analysis, prior carbapenem exposure (OR: 3.23; 95% CI: 1.67-6.25) and hematological malignancies (OR: 2.85; 95% CI: 1.10-7.41) were associated with non-carbapenemase-producing CRE (NCPE) (n = 88) compared with CPE (n = 161) subjects. Among 430 CRE isolates from the 249 subjects, 307(71.3%) were CPE, of which 154(50.2%) were blaKPC-positive, 97(31.6%) blaNDM-positive, and 42 (13.7%) blaOXA-positive. Klebsiella pneumoniae (n = 180, 41.9%), Escherichia coli (n = 129, 30.0%) and Enterobacter cloacae (n = 62, 14.4%) were the main Enterobacteriaceae species. WGS (n = 206) revealed diverse bacterial strain type (STs). The predominant blaKPC-positive plasmid was pHS102707 (n = 62, 55.4%) and the predominant blaNDM-positive plasmid was pNDM-ECS01 (n = 46, 48.9%). Five transmission clusters involving 13 subjects were detected. CONCLUSIONS: Clinical CRE trend among adult inpatients showed stabilization following a rapid rise since introduction in 2010 potentially due to infection prevention measures and antimicrobial stewardship. More work is needed on understanding CPE transmission dynamics.

Antimicrobial activity of ceftazidime-avibactam and comparator agents when tested against bacterial isolates causing infection in cancer patients (2013-2014).

We evaluated the antimicrobial susceptibility of 623 Gram-negative organisms causing infection in patients with cancer in 52 United States hospitals (2013-2014) as part of the International Network for Optimal Resistance Monitoring (INFORM) program. Isolates were tested for susceptibility by broth microdilution method. ß-lactamase encoding genes were evaluated for all Escherichia coli and Klebsiella spp. with an extended-spectrum ß-lactamase (ESBL) phenotype by microarray-based assay. ESBL-phenotype was observed among 17.3 and 9.9% of E. coli and Klebsiella pneumoniae, respectively; and 25.0% of Enterobacter cloacae were ceftazidime-non-susceptible. All Enterobacteriaceae (n=486) were susceptible to ceftazidime-avibactam (MIC50/90, 0.12/0.25µg/mL) with the highest MIC value at 1µg/mL. Meropenem was active against Enterobacteriaceae overall (MIC50/90, ≤0.06/≤0.06µg/mL; 99.6% susceptible); but showed more limited activity against Klebsiella spp. with an ESBL-phenotype (84.6% susceptible) and multidrug-resistant Enterobacteriaceae (93.3% susceptible). The most active agents tested against Pseudomonas aeruginosa were colistin (100.0% susceptible), amikacin (97.7% susceptible) and ceftazidime-avibactam (96.6% susceptible).

First Report of German Cockroaches (Blattella germanica) as Reservoirs of CTX-M-15 Extended-Spectrum-ß-Lactamase- and OXA-48 Carbapenemase-Producing Enterobacteriaceae in Batna University Hospital, Algeria.

Here we report the isolation of extended-spectrum ß-lactamase (ESBL)- and carbapenemase-producing Enterobacteriaceae from German cockroaches caught in the burn unit of Batna University Hospital in Algeria. Nine of 12 isolates harbored the blaCTX-M-15 ESBL gene. One Enterobacter cloacae isolate belonging to sequence type 528 coexpressed the blaOXA-48, blaCTX-M-15, and blaTEM genes. Our findings indicate that cockroaches may be one of the most dangerous reservoirs for ESBL and carbapenemase producers in hospitals.

High prevalence of plasmid-mediated quinolone resistance determinants in Enterobacter cloacae isolated from hospitals of the Qazvin, Alborz, and Tehran provinces, Iran

Abstract: INTRODUCTION: Plasmid-mediated quinolone resistance (PMQR) is a growing clinical concern worldwide. The main aims of this study were to detect qnr-encoding genes and to evaluate the clonal relatedness of qnr-positive Enterobacter cloacae isolates. METHODS: A total of 116 E. cloacae isolates that were not susceptible to quinolone were obtained from seven hospitals in Tehran, five hospitals in Qazvin, and two hospitals in Karaj (Iran). Bacterial identification was performed using standard laboratory methods and API 20E strips. Quinolone resistance was determined using the Kirby-Bauer disk diffusion method according to the Clinical Laboratory Standards Institute (CLSI) guidelines. PCR and sequencing were employed to detect qnrA, qnrB, and qnrS genes, and clonal relatedness was assessed using the enterobacterial repetitive intergenic consensus (ERIC)-PCR method. RESULTS: In total, 45 (38.8%) and 71 (61.2%) of isolates showed high- and low-level quinolone resistance, respectively, and qnr-encoding genes were detected in 70 (60.3%) of them. qnrB1 [45 (38.8%) isolates] was the most commonly detected gene, followed by qnrS1 [28 (24.1%) isolates] and qnrB4 [18 (15.5%) isolates] either alone or in combination with other genes. The results of the ERIC-PCR revealed that 53 (75.7%) qnr-positive isolates were genetically unrelated. CONCLUSIONS: This study describes, for the first time, the high prevalence of the qnrB1, qnrS1, and qnrB4 genes among E. cloacae isolates in Iran. The detection of qnr genes emphasizes the need for establishing tactful policies associated with infection control measures in hospital settings in Iran.

First identification of an IMI-1 carbapenemase-producing colistin-resistant Enterobacter cloacae in China.

BACKGROUND: Carbapenem resistance among the Enterobacteriaceae is a serious healthcare challenge. bla IMI is a carbapenemase gene mediating resistance to carbapenems but has not been commonly found. A bla IMI-carrying Enterobacter cloacae, which was also resistant to colistin, is reported here. FINDINGS: E. cloacae strain WCHECl-1060 was recovered from a blood sample of a leukemia patient, who was not previously exposed to colistin. Strain WCHECl-1060 belongs to a new sequence type, ST410, and was resistant to carbapenems and colistin but was susceptible to third-generation cephalosporins. A new allelic variant of bla IMI-1, which has two silent mutations compared to the original bla IMI-1 variant, was found in strain WCHECl-1060. Conjugation and transformation experiments failed to transfer bla IMI-1, suggesting a likely chromosome origin. CONCLUSIONS: To our knowledge, this is the first report of an IMI-1 carbapenemase-producing colistin-resistant E. cloacae in China. Microbiological laboratories should be aware of the unusual carbapenem-resistant but third-generation cephalosporin-susceptible profiles of these IMI-producing isolates. The trend of colistin resistance among the Enterobacteriaceae should be also monitored.