Enterobacter aerogenes is often spread by cross-contamination from surgery or consistant treatment in hospitals for patients who use catheters. Enterobacter aerogenes is highly resistant to antibiotics so most drugs are ineffective at treating infections.
The best way to fight these bacteria is to have proactive prevention practices. Active adherence to standard hand-hygiene regimens, environmental decontamination procedures, controlled use of antibiotics and aseptic insertion of catheters and implanted devices can help reduce transmission of the bacteria. One of the bi-products of fermentation is hydrogen gas. Many bacteria can produce hydrogen through fermentation at a neutral pH, and E.
Its optimal pH for hydrogen production is between 6 and 7. However, maintaining that high of a pH is difficult during fermentation because the process yields acidic products such as acetic acid, succinic acid, and lactic acid, and the accumulation of those products causes a decrease in pH. Typically, bacteria cease fermentation and thus cease the production of hydrogen at such low pH levels. However, one strain of E. This quality makes strain HO desirable as an energy source because it will continue energy production without much regulation of the bacterial environment.
When bacterial fermentation is inhibited at low pH levels, alkali must continually be added to the bacterial culture in order to counteract the low pH that is caused by the accumulation of the organic acids. Alkali is expensive and, consequently, is uneconomical for the harnessing of energy.
Using an aciduric facultative anaerobe such as E. Thus, this bacterium could be used as a cost-effective, clean energy source Brooks, Geo F. Carrol, MD; Janet S.
Butel, PhD; Stephen A. Morse, PhD. New York: McGraw Hill, Lederberg, Joshua; Martin Alexander [et al. Encyclopedia of Microbiology. San Diego, Ca. Sankaran, Neeraja. Phoenix, Az. Collins, C. Lune, J. Grange, J. O Falkinham III. Microbiological Methods. London: Arnold, Atlas, Ronald M.
Microbial Ecology Fundamentals and Applications. Menlo Park, Ca. Greenwood, David; Richard C. Slack; John F. Edinburgh: Churchill Livingstone, Janda, J. Michael; Sharon L. The Enterobacteria 2nd ed. Washington D. Bailey, W. Diagnostic Microbiology , 4th ed. Louis, Mo. Mosby Co. De Gheldre, Y. J Clin Microbiol. Rhondina, Matthew T. Distinguishing colonization from infection is extremely difficult unless the patient has the same strain of Enterobacter isolated from respiratory secretions and bloodstream or pleural fluid.
No data exists to guide therapy for respiratory Enterobacter infections, other than the general guidelines outlined in the discussion of the bacteremia study 7.
For bacteremia, the drug of choice for Enterobacter is probably a carbapenem if in vitro susceptibility results are not available. Stepdown to cefepime is reasonable once susceptibility results are confirmed. Enterobacter is an uncommon cause of meningitis, with two exceptions: postneurosurgical meningitis and neonatal meningitis.
The agents with the best activity against Enterobacter and the best CSF penetration are the carbapenems and fourth generation cephalosporins. Members of both classes have shown success in treating gram-negative meningitis 47 , Until further clinical data is available, meropenem may be the preferred agent; it has a superior safety profile when compared to i mipenem in treating central nervous system infections.
In this retrospective study, 13 patients with Enterobacter meningitis complicating trauma or neurosurgical procedures were treated with TMP-SMX with or without other agents extended-spectrum cephalosporins, aminoglycosides, chloramphenicol and all were cured.
Although the vast majority of Enterobacter infections are due to E. In a review of 15 cases, risk factors for a fatal outcome included prematurity and low birth weight. About half of reported cases had cyst or abscess formation. The epidemiology of this organism is poorly understood.
A recent report described E. This organism has been reported to cause community -acquired infection complicating severe trauma or crush injuries 1. In this report, 5 cases were described among trauma victims. All isolates in this report were susceptible to extended-spectrum cephalosporins and quinolones.
This agent is used infrequently in the treatment of Enterobacter infections. The newer quinolones such as moxifloxacin and gatifloxacin have greater activity against gram-positive pathogens than the older members of this class, but have no greater activity against gram-negative rods in general and Enterobacter in particular.
It is reasonable to anticipate that quinolone resistance rates will continue to increase over time as these agents are increasingly employed in the treatment of serious Enterobacter infections. A cautionary note is raised by the report of Davin-Regli et al These authors reported an outbreak of Enterobacter hormachei infections among patients in a French hospital who had been treated with quinolones.
Twenty-one resistant isolates were detected over a one-year period. All were clonally related by the random amplification of DNA technique. Quinolone resistance in Enterobacter is usually due to chromosomal genes that may upregulate efflux pumps 42 or confer resistance due to altered DNA gyrase As with other bacterial infections, abscesses should be surgically drained in conjunction with appropriate antibiotic therapy.
There are no guidelines specific for Enterobacter infections. However, given the high propensity of this organism to acquire resistance during therapy, it would be prudent to repeat blood cultures at the end of therapy in patients treated for bacteremia.
Op timizing Pharmacodynamics: One of the potential strategies to improve outcomes in the treatment of gram negative infections in general, and Enterobacter in particular, is to optimize pharmacokinetic and pharmacodynamic properties of antimicrobial regimens. This may lead to better clinical outcomes 54 and less bacterial resistance Thomas and colleagues 54 examined the relationship between antibiotic pharmacokinetics and organism MICs in four clinical trials for nosocomial pneumonia.
Phamacodynamic models were developed to identify factors associated with the development of bacterial resistance. Enterobacter species were the second most common pathogen recovered from these patients after P. The authors found that combination therapy resulted in much lower rates of emergence of resistance than monotherapy.
Ratios under were associated with emergence of resistance. K ashuba and colleagues 30 analyzed data from 78 patients with nosocomial pneumonia treated with aminoglycosides. Again Enterobacter was the second most common pathogen recovered from these patients, after P. The authors found that optimizing aminoglycoside dosing predicted better clinical outcomes. W orkers at the LDS Hospital in Salt Lake City, Utah, have been developing computerized clinical-decision-support programs to assist clinicians treating infectious diseases for many years These tools are intended to improve the use of antiinfective drugs for surgical prophylaxis as well as empiric and directed therapy.
The program is linked to the information center of the medical center to maximize the amount of patient-specific information provided to clinicians. W hen gram-negative bacilli are isolated from blood, the program provides a recommendation for empiric therapy based on recommendations from infectious disease physicians. As microbiology data becomes available, it is incorporated into the logic and recommendations are refined.
Patient data is used to generate specific drug and dosing recommendations. Alerts are provided for susceptibility mismatches as well as allergies and dosing errors. T his approach has been shown to diminish the number of adverse drug events, amount of unnecessary therapy, and costs of antimicrobial agents. T his program was developed over many years and is not yet commercially available. The use of infectious disease consultants and antibiotic guidelines have been shown in some cases to diminish antibiotic utilization and the incidence of multiply resistant pathogens The two main engines driving resistance in the hospital are selective pressures due to antibiotics and inadequate attention to infection control measures, especially handwashing.
This is a major problem at medical centers worldwide. An illustrative paper is the work of Pittet and colleagues from the University of Geneva, Switzerland In addition, noncompliance was higher in the ICU, during high-risk procedures, when intensity of care was highest, and on weekends.
A lthough the use of gloves for all patient contact as part of universal precautions was expected to lead to a significant reduction in cross contamination, the effect appears to be modest In part this is because caregivers may wear the same gloves between patients In an intriguing study, Harbarth and colleagues 24 reported an outbreak of Enterobacter cloacae infections in a neonatal ICU which was linked to inadequate staffing.
Three epidemic clones were identified. Cross-transmission was facilitated by understaffing and overcrowding. Twenty-five neonates had been housed in a unit built for Observed compliance with handwashing was poor.
Termination of the outbreak was accomplished by a decrease in crowding and workload and increased attention to aseptic technique, especially handwashing.
Several studies document that solutions containing alcohol are superior to conventional handwashing with soap. In a controlled clinical trial at the University of Barcelona, Zaragoza and colleagues 61 compared these 2 techniques head to head in a clinical trial. A total of 47 health care workers were studied. The average reduction in the number of colony-forming units from hand samples was Most of the organisms recovered from these samples were staphylococci and enteric bacilli.
An tibiotic cycling, or rotation, is a strategy of employing different antibiotic classes, usually for a specified time, in an attempt to minimize selective pressure This is commonly done in a defined unit, such as an ICU. The data to support this approach is modest at present but several trials are underway which may shed additional light on its utility. The first controlled observations of cycling were studies of aminoglycoside rotation conducted by Gerding and colleagues 23 over a 10 year period at the Minneapolis Veterans Hospital.
The motivation to attempt this was provided by a steady rise in the prevalence of gentamicin resistance in gram negative bacilli. Using cycles of 12 to 51 months, these investigators found significantly reduced resistance to gentamicin when amikacin was substituted. More recent work has been conducted by Kollef and colleagues at Washington University in St.
Louis, Missouri 31 , These investigators have shown that inadequate empiric therapy for sepsis in ICU patients is associated with a high mortality rate. During the ciprofloxacin period, there were fewer patients receiving inadequate therapy for gram negative infections, especially ventilator-associated pneumonia.
Gram negative bacilli resistant to third-generation cephalosporins, particularly P. Ho w much of the improvement in reducing inadequate therapy in these studies can be attributed solely to using a fluoroquinolone to which resident flora were quite susceptible instead of a cephalosporin in a unit with a high resistance rate to these agents , as opposed to cycling per se, remains to be seen. The Centers for Disease Control is sponsoring a multicenter study which is in progress as of the time of this writing, which may shed additional light on the utility of this approach.
Abbott S, Janda J. Enterobacter cancerogenus " Enterobacter taylorae" Infections associated with severe trauma or crush injuries. Am J Clin Pathol. For the determination of MICs, approximately 10 6 cells were inoculated into 1 ml MH broth containing twofold serial dilutions of each antibiotic.
In this study, a fixed concentration of The MIC was the lowest concentration of the antimicrobial agent at which no growth was detected and resistance was defined as previously described [10] , [13]. It is important to mention that, today no chloramphenicol breakpoint is proposed for E.
Briefly, the E. Electrophoresis was performed for 22 hours with a pulsed time ranging from 1 to 50 s. Measurement of 14 C chloramphenicol accumulation by intact cells has been described previously [13] , [24]. Samples removed at set intervals were filtered and washed. The filters were dried and radioactivity was measured in a Packard scintillation counter. Samples amount corresponding to 0. Immunoreactive proteins were visualized with alkaline phosphatase -conjugated anti-rabbit secondary antibodies [13] , [16].
This study is submitted in memoriam to Claude Bollet deceased during this work. We thank L. Amaral, J. Bolla and C. James for fruitful discussion. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract Background The high mortality impact of infectious diseases will increase due to accelerated evolution of antibiotic resistance in important human pathogens.
Introduction Among Enterobacteriaceae associated hospital infections, Enterobacter aerogenes has emerged during the last twenty years due to its efficient adaptative response to environmental stresses [1].
Results Strain characterization and antibiotic susceptibility of E. Download: PPT. Figure 1. Table 1. Susceptibilities of the E. Table 2. Table 3. Percentages of Enterobacter aerogenes resistant strains. Table 4. Effect of EPI on chloramphenicol susceptibility of E.
Evidence of active efflux for chloramphenicol in multiresistant E. Figure 2. Uptake of 14 C chloramphenicol by E. Table 5. Antimicrobial susceptibilities and chloramphenicol accumulation in E. Detection of an immunorelated-AcrA component of the efflux pump To analyse the correlation between multidrug resistance and the presence of an efflux system we investigated the production of an immunorelated-AcrA component in the isolates exhibiting an energy dependent efflux of chloramphenicol [29] , [30].
Discussion Emergence and evolution of drug resistance mechanisms in bacteria is an unavoidable phenomenon because it represents a natural adaptative response to environmental stress. Methods Bacterial strains and growth media A total of 93 strains of Enterobacter aerogenes were isolated in and in the hospitals of Marseille France from a variety of clinical specimens respiratory tract, secretions, blood, urinary tract, etc ….
Epidemiological typing E. Measurement of chloramphenicol accumulation Measurement of 14 C chloramphenicol accumulation by intact cells has been described previously [13] , [24].
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