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PubMed2005

Rapid, specific detection of Enterobacter sakazakii in infant formula using a real-time PCR assay.

Enterobacter sakazakii is a rare cause of invasive infection with high mortality rates in neonates. Powdered milk-based infant formulas have been associated with the E. sakazakii-related outbreaks in premature or other immunocompromised infants. In this study, an assay was developed for the specific detection of E. sakazakii in infant formula using an application of the fluorogenic 5' nuclease assay (TaqMan). A set of primers and probe was designed using the E. sakazakii partial macromolecular synthesis operon: the rpsU gene 3' end and the primase (dnaG) gene 5' end. The specificity of the assay was evaluated using 68 Enterobacter and 55 non-Enterobacter strains. The newly developed assay enables us to detect 100 CFU/ ml in pure culture and in reconstituted infant formula in 50 cycles of PCR without enrichment. The assay was specific enough to discriminate E. sakazakii from all other Enterobacter and non-Enterobacter strains tested. The developed real-time PCR assay could save up to 5 days and eliminate the need for plating samples on selective or diagnostic agars and for biochemical confirmation steps. The real-time PCR assay could be used to rapidly screen infant formula samples for E. sakazakii and would be a boon to food industries and regulatory agencies.

Colony Count, Microbial↗
PubMed1998

Risk factors for Enterobacter septicemia in a neonatal unit: case-control study.

Thirty cases of Enterobacter aerogenes or Enterobacter cloacae septicemia diagnosed over a 32-month period in a tertiary care neonatal unit were enrolled in a case-control study. Each case patient was matched with two controls (patients occupying the cots nearest the case patient when the latter developed septicemia). Of the 32 perinatal characteristics evaluated, 11 were identified by univariate analysis to be significantly associated with the infection. These included parents being residents of the Vietnamese refugee camps, respiratory distress syndrome, necrotizing enterocolitis, umbilical arterial catheterization, umbilical venous catheterization, bladder catheterization, mechanical ventilation, antibiotic treatment, peripheral venous catheterization, nasogastric intubation, and parenteral nutrition. Multivariate analysis, however, showed that preceding bladder catheterization and ongoing parenteral nutrition were the only independent risk factors for enterobacter septicemia. Strict aseptic technique in the preparation of parenteral nutrition fluid and avoidance of bladder catheterization are measures that may reduce the risk of enterobacter sepsis for newborns.

Bacteremia↗
PubMed1994

Increasing Enterobacter bacteremia in pediatric patients.

Thirty-two episodes of Enterobacter bacteremia were identified in 30 patients at Children's Hospital of Michigan between September, 1989, and November, 1992. Fifty-six percent of the episodes were nosocomial. Enterobacter accounted for 14% of all nosocomial bacteremias and was the most common Gram-negative organism causing such infections. Enterobacter cloacae was the most commonly isolated species (72%). Twenty-nine (97%) patients had underlying risk factors for infection, including central venous catheters in 22. The susceptibility pattern of 46 Enterobacter isolates from blood during the same study period showed high resistance to extended spectrum penicillins and third generation cephalosporins but low resistance to aminoglycosides and trimethoprim-sulfamethoxazole (TMP/SMX). Resistance to third generation cephalosporins increased throughout the study period and was higher in patients who had received these agents during the previous month. In situations where there is a high frequency of Gram-negative bacteremias with organisms resistant to third generation cephalosporins, we suggest that initial therapy be a combination of a beta-lactam agent and an aminoglycoside or TMP/SMX.

Anti-Bacterial Agents↗
PubMedDate not supplied

[Phenotypic and genotypic characterization of resistance to third-generation cephalosporins in Enterobacter spp].

Enterobacter spp. are becoming increasingly frequent nosocomial pathogens with multiple resistance mechanism to beta-lactam antibiotics. We carried out the phenotypic and genotypic characterization of beta-lactamases in 27 Enterobacter spp. (25 Enterobacter cloacae y 2 Enterobacter aerogenes), as well as the ability of different extended spectrum-lactamase (ESBL) screening methods. Resistance to third generation cephalosporins was observed in 15/27 (63%) isolates. Twelve resistant isolates produced high level chromosomal encoded AmpC beta-lactamase; 6 of them were also producers of PER-2. Resistance to third generation cephalosporins in the remaining 3 isolates was due to the presence of ESBLs, PER-2 in 2 cases, and CTX-M-2 in the other. Only CTX-M-2 production was detected with all tested cephalosporins using difusion synergy tests, while cefepime improved ESBLs detection in 7/8 PER-2 producers, 4/8 in the inhibitor approximation test and 7/8 with double disk test using cefepime containing disk with and without clavulanic acid. Dilution method, including cephalosporins with and without the inhibitor detected 1/9 ESBLs producers.

Cephalosporin Resistance↗
PubMed1993

Enterobacter cloacae cross-colonization in neonates demonstrated by ribotyping.

The intestinal colonization by Enterobacter cloacae strains with a derepressed cephalosporinase was studied in a paediatric ward between February 1990 and January 1991. Environmental sampling was performed simultaneously. Fifty-two isolates were recovered from 200 neonates (stool, blood) and 14 strains were isolated from the neonatal environment. An epidemiological study based on the typing of 36 Enterobacter cloacae isolates was carried out using antibiotyping, biotyping and ribotyping methods. The isolates selected were from 21 neonates (24 isolates), the neonatal ward environment (8 isolates) and from other wards (4 isolates). Thirty-two isolates had the same antibiotic resistance pattern, corresponding to a derepressed cephalosporinase and resistance to the following aminoglycosides: kanamycin, gentamicin, tobramycin and netilmicin. No predominant biotyping pattern could be established. Ribotyping done with two endonucleases (EcoRI and BamHI) showed 28 Enterobacter cloacae isolates to have a single pattern. Ribotyping was the most discriminating method used in this study, permitting identification of cross-contamination with Enterobacter cloacae in the paediatric ward.

Bacteremia↗
PubMed1994

Epidemiologic perspectives on Enterobacter for the infection control professional.

Enterobacter species have emerged as important nosocomial pathogens. Common reservoirs for these organisms include wounds and the gastrointestinal, urinary, and respiratory tracts. Enterobacter bacteremia typically occurs in patients with long-standing underlying illnesses who received antimicrobial agents before their bacteremia. The wide use of broad-spectrum antibiotics has contributed to the increased prominence of Enterobacter infections. Enterobacter species have a propensity to emerge resistant to the antibiotic therapy administered. Plasmid analysis, restriction endonuclease analysis of total cellular DNA, pulsed-field electrophoresis, and ribotyping can be valuable in investigating the spread of antibiotic-resistant strains.

Anti-Bacterial Agents↗
PubMed2005

Biosorption of lead, copper and cadmium by an indigenous isolate Enterobacter sp. J1 possessing high heavy-metal resistance.

This study was undertaken to investigate biosorption kinetics and equilibria of lead (Pb), copper (Cu) and cadmium (Cd) ions using the biomass of Enterobacter sp. J1 isolated from a local industry wastewater treatment plant. Efficiency of metal ion recovery from metal-loaded biomass to regenerate the biosorbent was also determined. The results show that Enterobacter sp. J1 was able to uptake over 50mg of Pb per gram of dry cell, while having equilibrium adsorption capacities of 32.5 and 46.2mg/g dry cell for Cu and Cd, respectively. In general, Langmuir and Freundlich models were able to describe biosorption isotherm fairly well, except that prediction of Pb adsorption was relatively poor with Langmuir model, suggesting a different mechanism for Pb biosorption. Adjusting the pH value to 3.0 led to nearly complete desorption of Cd from metal-loaded biomass, while over 90% recovery of Pb and Cu ions was obtained at pH<or=2. After four repeated adsorption/desorption cycles, biomass of Enterobacter sp. J1 retained 75, 79 and 90% of original capacity for adsorption of Pb, Cu and Cd, respectively, suggesting good reusability of the biosorbent. A combinative model was proposed to describe the kinetics of heavy-metal adsorption by Enterobacter sp. J1 and the model appeared to have an excellent prediction of the experimental data. The model simulation results also seemed to suggest that intracellular accumulation may occur during the uptake of Pb.

Absorption↗
PubMed1985

Enterobacter mediastinitis following cardiac surgery.

Eight cases of sternal/mediastinal infection due to Enterobacter species were seen in postoperative cardiac patients during 1980 to 1981. The attack rate was 14.5% (8/55), compared to 3.7% (2/54) for an identical period in 1979 to 1980 (p less than 0.05). Cases varied in severity from fulminant, acute bacteremic infections (one death) to less severe wound infection. Late complications or recurrences were not seen. There was a hospital-wide increase, relative to all other gram-negative bacillary isolates, in Enterobacter laboratory isolations, but no increased rate of infection in any other specific surgical condition. No personnel, materials, or techniques were associated with the outbreak, and all but two environmental cultures were negative. Case-control analysis suggested that surgical complications and prophylactic cephalosporins were associated with infection. Prospectively, an additional 85 cardiac surgery patients had increased Enterobacter skin/wound colonization following perioperative prophylaxis with cephalosporin antibiotics. After introduction of barrier isolation and restriction of contacts no further mediastinitis occurred in 100 subsequent cardiac surgery patients. This study indicates that Enterobacter may be major pathogens causing post-cardiac-surgery infection not prevented by cephalosporin prophylaxis.

Cardiac Surgical Procedures↗
PubMed2002

Klebsiella and enterobacter: antibiotic resistance and treatment implications.

KLEBSIELLA: spp. and Enterobacter spp. are widespread throughout the environment and also carried by humans. Both genera are well-recognized community and nosocomial pathogens and cause significant infections. They are a common cause of respiratory and nonrespiratory infections. Klebsiella spp. is responsible for 1% to 5% of all cases of community-acquired pneumonia and between 0% to 23% of those acquired in the hospital, and its frequency is greater in alcoholic patients. The majority of cases are unilateral in the posterior segment of the right upper lobe. Lung abscess can occur after a pneumonic process or secondarily to Klebsiella spp. infections and have high rates of morbidity and mortality. K. pneumoniae is one of the most common microorganisms responsible for empyema. Klebsiella spp. and Enterobacter spp. rank fourth and third, respectively, as causes of hospital-acquired pneumonia mainly in patients during the early period of mechanical ventilation. Klebsiella spp. are intrinsically resistant to penicillins and can acquire resistance to third- and fourth-generation cephalosporins owing to the production of plasmid-mediated extended-spectrum beta-lactamases (ESBLs). These plasmids frequently carry aminoglycoside-modifying enzymes. Enterobacter spp. are intrinsically resistant to ampicillin, amoxicillin, amoxicillin-clavulanate, first-generation cephalosporins, and cefoxitin owing to the production of constitutive AmpC beta-lactamase. The derepression of this enzyme is increasingly frequent among clinical isolates and confers resistance to third-generation cephalosporins, and ureido- and carboxypenicillins; fourth-generation cephalosporins retain reasonable activity against depressed strains. Most isolates of Klebsiella spp. and Enterobacter spp. are susceptible to fluoroquinolones, trimethoprimsulfamethoxazole, aminoglycosides, and carbapenems. In some instances, treatment of severe infections caused by these microorganisms may benefit from the combination of beta-lactams (or fluoroquinolones) with aminoglycosides. Because of the high risk for developing resistance during treatment, all severe infections should be carefully watched during therapy.

Anti-Bacterial Agents↗
PubMed2000

Enterobacter cloacae sepsis outbreak in a newborn unit caused by contaminated total parenteral nutrition solution.

OBJECTIVE: The study aimed to investigate an outbreak caused by Enterobacter cloacae in a neonate intensive care unit. DESIGN: A descriptive study of an outbreak of sepsis in high-risk neonates was used. SETTING: The study was set in a tertiary care university teaching hospital. PATIENTS: The patients were 11 neonates infected with Enterobacter cloacae whose symptoms and signs of sepsis developed during a 16-hour period. All but one neonate received parenteral nutrition. Isolates from blood cultures, in-use parenteral nutrition solutions, and control aliquots of parenteral nutrition solution were typed by pulsed-field gel electrophoresis. RESULTS: Enterobacter cloacae was found in the refrigerated aliquots of parenteral nutrition solution, in blood cultures from infected newborns, and from in-use parenteral nutrition solutions. All these strains of Enterobacter cloacae had the same antibiotic susceptibility pattern and the same genomic DNA profile. The strain isolated from the one patient who did not receive parenteral nutrition presented a different susceptibility profile and genotype. CONCLUSION: The source of the nosocomial sepsis was the parenteral nutrition solution in 10 neonates. This contamination apparently occurred during preparation of the parenteral solution.

Disease Outbreaks↗
PubMed2001

Retro-nitroreductase, a putative evolutionary precursor to Enterobacter cloacae strain 96-3 nitroreductase.

Enterobacter cloacae strain 96-3 nitroreductase (NR) is a homodimeric flavoenzyme that catalyzes the pyridine nucleotide-dependent four-electron reduction of a variety of nitroaromatic compounds, including the explosives TNT (2,4,6-trinitrotoluene), RDX (1,3,5-trinitro-1,3,5-triazine), tetryl (2,4,6-trinitrophenyl-N-methylnitramine), and pentryl (2,4,6-trinitrophenyl-N-nitroaminoethylnitrate). The enzyme was initially characterized by Bryant et al. from a strain of Enterobacter that had been isolated from a weapons dump in La Jolla, CA. The enzyme displays a catalytic efficiency for nitroreduction at least 10-fold higher than that of several highly homologous bacterial nitroreductases and has long been thought to have evolved to be a more efficient nitroreductase due to the high nitroaromatic compound concentrations in its environment. We report the cloning and biochemical characterization of a nitroreductase gene from a clinical isolate of Enterobacter cloacae, a strain that presumably had not encountered high concentrations of nitroaromatics. The new enzyme, which we term retro-nitroreductase, had an amino acid sequence 96.7% identical to NR, and most differences are relatively conservative. The catalytic efficiency of the new enzyme is twofold less than that of NR for the oxidation of NADH and is not significantly different from the value observed for NR for the reduction of dinitrobenzyl alcohol. We conclude that NR has not significantly evolved to be a more efficient nitroreductase as a result of its environment, and the relatively high catalytic activity of the enzyme is a general property of Enterobacter cloacae nitroreductases.

Amino Acid Sequence↗
PubMed1993

Canadian survey of antimicrobial resistance in Klebsiella spp. and Enterobacter spp. The Canadian Antimicrobial Resistance Study Group.

Increasing antimicrobial resistance has been reported for Klebsiella spp. and Enterobacter spp. The in-vitro activities of 14 antimicrobial agents against 656 clinical isolates of Klebsiella spp. and 630 isolates of Enterobacter spp. collected from seven cities in Canada were determined by microbroth dilution. There was no regional variation in the susceptibility patterns. Klebsiella spp. remain highly susceptible to most antimicrobials, only one isolate was resistant to third-generation cephalosporins. However, many isolates of Enterobacter spp. (> 16%) were resistant to the third-generation cephalosporins with marked cross-resistance to piperacillin (63.1%), piperacillin/tazobactam (44.9%), and aztreonam (76.6%). Gentamicin, tobramycin, imipenem, ciprofloxacin, cefepime, and cefpirome were consistently active against most isolates of Enterobacter spp. including those resistant to the third-generation cephalosporins.

Anti-Bacterial Agents↗
PubMed2026

Extensive hidden prophage diversity in Enterobacter species reveals host specificity and local distribution.

Bacteriophages are key drivers of bacterial evolution, particularly through their integration as prophages within host genomes. However, the diversity and host specificity of prophages in relevant pathogens such as Enterobacter species remain poorly characterized. In this study, we revealed the diversity of prophages, mapped their distribution and explored their relationships with their bacterial hosts. We analysed 3,661 prophage sequences identified from the genomes of 20 different Enterobacter species. This analysis uncovered an extensive hidden diversity, comprising 1,617 phage genera and 2,423 phage species - nearly 80% of which were singletons - highlighting an exceptionally rich prophage landscape. We found substantial variation in prophage species richness across host species and isolation sources, with Enterobacter kobei and environmental isolates exhibiting the highest richness. Prophage populations showed strong host specificity and limited cross-species transmission. Moreover, prophages exhibited geographic structuring and significant congruence between host and prophage phylogenies, as well as with the ecological lifestyles of their bacterial hosts. Although we found phages of the same species infecting different host species, these events were infrequent. Finally, bacterial genomes encoded diverse defence systems, mainly PDC-S07, RM type I-II and gabija, whereas only 8.9% of prophages encoded anti-defence systems, mostly anti-CBASS and anti-RM. Overall, this study provides new insights into the diversity of Enterobacter prophages and underscores their ecological and clinical relevance in shaping host adaptation and phage-host dynamics.

Prophages↗
PubMed2003

Treatment with a broad-spectrum cephalosporin versus piperacillin-tazobactam and the risk for isolation of broad-spectrum cephalosporin-resistant Enterobacter species.

Receipt of a broad-spectrum cephalosporin is a strong risk factor for isolation of broad-spectrum cephalosporin-resistant Enterobacter species, and yet the risk from other broad-spectrum beta-lactams hydrolyzed by group 1 beta-lactamases has not been well characterized. We compared the risk conferred by broad-spectrum cephalosporins to that conferred by piperacillin-tazobactam, alone or in combination with an aminoglycoside or a fluoroquinolone. A retrospective cohort was monitored from treatment onset until a broad-spectrum cephalosporin-resistant Enterobacter strain was isolated or the patient was discharged. There were 447 patients in the piperacillin-tazobactam group and 2,341 patients in the broad-spectrum cephalosporin group. Groups were similar in age (mean, 62.5 years). The piperacillin-tazobactam group had a smaller percentage of men (32% versus 44%, P < 0.001) and a lower rate of intensive care unit stay (25% versus 38%, P < 0.001) but a higher rate of surgery (41% versus 26%, P < 0.001). Groups differed in the distribution of comorbidities. Resistant Enterobacter strains were isolated from 62 patients, 2% in each group (hazard ratio [RR] = 1.02 [P = 0.95]). In multivariable analysis, risk was similar among treatment groups (RR = 0.71 [P = 0.32]). Intensive care unit stay and surgery were associated with increased risk (RR = 4.53 [P < 0.001] and RR = 1.97 [P = 0.015], respectively), fluoroquinolones were protective (RR = 0.24 [P = 0.003]), and aminoglycosides did not affect risk (RR = 0.98 [P = 0.95]). The protective effect of fluoroquinolones against isolation of broad-spectrum cephalosporin-resistant Enterobacter spp. and the equivalence in risk associated with piperacillin-tazobactam and broad-spectrum cephalosporins may have important clinical and epidemiologic implications.

Anti-Bacterial Agents↗
PubMed1969

Characterization of ornithine decarboxylase-positive, nonmotile strains of the Klebsiella-Enterobacter group.

Thirty-seven strains of ornithine decarboxylase-positive, nonmotile Klebsiella-Enterobacter organisms isolated from 36 patients were studied by biochemical and serological testing. Five strains gave biochemical reactions which conformed closely to those of Escherichia coli; three strains gave positive Quellung reactions to specific Klebsiella antisera. (Two of these were thought to be Enterobacter in spite of this typing reaction.) The remaining 29 strains were classified as Enterobacter. These results demonstrate the necessity of doing both an ornithine decarboxylase test and a motility test to differentiate Klebsiella from Enterobacter. Had only a motility test been done, they all would have been called Klebsiella.

Carboxy-Lyases↗
PubMed1990

Cloning and nucleotide sequence of the Enterobacter aerogenes signal peptidase II (lsp) gene.

In Escherichia coli, prolipoprotein signal peptidase is encoded by the lsp gene, which is organized into an operon consisting of ileS, lsp, and three open reading frames, designated genes x, orf-149, and orf-316. The Enterobacter aerogenes lsp gene was cloned and expressed in E. coli. The nucleotide sequence of the Enterobacter aerogenes lsp gene and a part of its flanking sequences were determined. A high degree of homology was found between the E. coli ileS-lsp operon and the corresponding genes in Enterobacter aerogenes. Furthermore, the same five genes which constitute an operon in E. coli were found in Enterobacter aerogenes in the same order.

Amino Acid Sequence↗
PubMed2001

PCR analyses of tRNA intergenic spacer, 16S-23S internal transcribed spacer, and randomly amplified polymorphic DNA reveal inter- and intraspecific relationships of Enterobacter cloacae strains.

PCR analysis of tRNA intergenic spacer (tDNA-PCR) and of the 16S-23S internal transcribed spacer (ITS-PCR) and random amplified polymorphic DNA (RAPD) analysis were evaluated for their usefulness in characterization of Enterobacter cloacae strains isolated from both clinical origins and vaccine microbial contamination. tDNA-PCR presented specific and reproducible patterns for Enterobacter sakazakii ATCC 29004, Enterobacter aerogenes ATCC 13048, and Enterobacter cloacae ATCC 13047 and 23355 that presented the same profile for all 16 E. cloacae isolates, offering an alternative tool for species-level identification. ITS-PCR and RAPD analysis yielded completely different banding patterns for the 20 strains studied, except for E. cloacae strains isolated from different batches of vaccine that exhibited a unique pattern, suggesting contamination by the same strain. The combined use of tDNA-PCR and ITS-PCR in a one-step protocol allows accurate identification and typing of E. cloacae strains a few hours after the colony has been isolated.

DNA, Intergenic↗
PubMed1987

Synergy of imipenem--a novel carbapenem, and rifampin and ciprofloxacin against Pseudomonas aeruginosa, Serratia marcescens and Enterobacter species.

Although imipenem inhibits most bacteria at very low concentrations, some Pseudomonas aeruginosa, Serratia marcescens and Enterobacter species are resistant or become resistant after exposure. At concentrations of rifampin equivalent to those attainable in man after daily oral ingestion of 600 mg, synergy of imipenem and rifampin was found for 52% of 62 P. aeruginosa and an additive effect for 37%. Against 30 S. marcescens synergy of imipenem and rifampin was not found, but an additive effect was noted for 47% of the isolates. With 32 Enterobacter isolates 35% were synergically inhibited, and an additive effect was found against 38% of the strains. Imipenem and ciprofloxacin were synergistic for 8% of P. aeruginosa and 22% of Enterobacter. Eighty-seven percent of P. aeruginosa isolates with imipenem MIC greater than or equal to 4 micrograms/ml were synergistically inhibited by the combination of imipenem-rifampin. Imipenem MIC and MBC were lowered to 1-2 micrograms/ml and to 2-4 micrograms/ml for rifampin. MIC of imipenem and ciprofloxacin were 0.5-2 and 0.05-0.1 micrograms/ml, respectively. When a triple combination of imipenem-rifampin-ciprofloxacin was studied, 62% of P. aeruginosa, 32% of Enterobacter spp. and 47% of S. marcescens were synergistically inhibited.

Ciprofloxacin↗