Advanced Expert System Research Articles

Carbapenem Resistance inKlebsiella pneumoniaeNot Detected by Automated Susceptibility Testing

Detecting β-lactamase–mediated carbapenem resistance among Klebsiella pneumoniae isolates and other Enterobacteriaceae is an emerging problem. In this study, 15 blaKPC-positive Klebsiella pneumoniae that showed discrepant results for imipenem and meropenem from 4 New York City hospitals were characterized by isoelectric focusing; broth microdilution (BMD); disk diffusion (DD); and MicroScan, Phoenix, Sensititre, VITEK, and VITEK 2 automated systems. All 15 isolates were either intermediate or resistant to imipenem and meropenem by BMD; 1 was susceptible to imipenem by DD. MicroScan and Phoenix reported 1 (6.7%) and 2 (13.3%) isolates, respectively, as imipenem susceptible. VITEK and VITEK 2 reported 10 (67%) and 5 (33%) isolates, respectively, as imipenem susceptible. By Sensititre, 13 (87%) isolates were susceptible to imipenem, and 12 (80%) were susceptible to meropenem. The VITEK 2 Advanced Expert System changed 2 imipenem MIC results from >16 μg/mL to <2 μg/mL but kept the interpretation as resistant. The recognition of carbapenem-resistant K. pneumoniae continues to challenge automated susceptibility systems.

Carbapenem Resistance in Klebsiella pneumoniae Not Detected by Automated Susceptibility Testing

Abstract Detecting β-lactamase–mediated carbapenem resistance among Klebsiella pneumoniae isolates and other Enterobacteriaceae is an emerging problem. In this study, 15 blaKPC-positive Klebsiella pneumoniae that showed discrepant results for imipenem and meropenem from 4 New York City hospitals were characterized by isoelectric focusing; broth microdilution (BMD); disk diffusion (DD); and MicroScan, Phoenix, Sensititre, VITEK, and VITEK 2 automated systems. All 15 isolates were either intermediate or resistant to imipenem and meropenem by BMD; 1 was susceptible to imipenem by DD. MicroScan and Phoenix reported 1 (6.7%) and 2 (13.3%) isolates, respectively, as imipenem susceptible. VITEK and VITEK 2 reported 10 (67%) and 5 (33%) isolates, respectively, as imipenem susceptible. By Sensititre, 13 (87%) isolates were susceptible to imipenem, and 12 (80%) were susceptible to meropenem. The VITEK 2 Advanced Expert System changed 2 imipenem MIC results from >16 μg/mL to <2 μg/mL but kept the interpretation as resistant. The recognition of carbapenem-resistant K. pneumoniae continues to challenge automated susceptibility systems.

Utility of the VITEK 2 Advanced Expert System for Identification of Extended-Spectrum β-Lactamase Production in Enterobacter spp

Forty clinical isolates of Enterobacter spp. were identified as extended-spectrum beta-lactamase (ESBL) producers by disk diffusion. The VITEK 2 Advanced Expert System (AES) identified the ESBL phenotype in only 25 isolates (62.5%), and erroneously reported cephalosporin susceptibility in 11 isolates (28%). Refinements in the AES are required in order to improve ESBL detection in Enterobacter.

Laboratory diagnosis of bloodstream infections caused by extended-spectrum ß-lactamase-producing E. coli and Klebsiella species

Extended-spectrum ß-lactamase (ESBL)-producing organisms are resistant to the third-generation cephalosporins commonly used as empirical therapy for a wide range of serious infections. It is therefore important for laboratories to offer reliable ESBL detection methods. This study compares two combination disc methods (Oxoid and Mast Diagnostics) containing cepodoxime with and without clavulanate with Vitek 2 for routine detection of ESBLs in Escherichia coli and Klebsiella spp. isolated from blood cultures. From December 2003 to April 2005, a total of 58 potential ESBL-producing isolates (resistant to cefotaxime and/or ceftazidime) by BSAC disc susceptibility were tested by the combination discs and Vitek 2. The Advanced Expert System, a feature of Vitek 2 reports possible mechanisms of resistance, based on interpretive reading of MICs. This study detected 7.4% more ESBL-producing isolates by Vitek 2 than by Oxoid disc testing (95% CI: 0.15–14.7%; P<0.2) and 31.6% more ESBL-producing isolates were detected by Vitek 2 than by Mast disc testing, (95% CI: 16.2–46.96%; P<0.001). Batch-to-batch variation was evident in disc performance for both disc types. Thus, use of appropriate controls is recommended when testing by the combination disc methods. Although no phenotypic test is 100% sensitive and specific, the Vitek 2 was a reliable system for ESBL detection; however, it is expensive and interpretation of results can be confusing to inexperienced users. Further studies to compare Vitek 2 with cefotaxime and ceftazidime combination discs may reveal disc methodology for ESBL detection to be a more reliable alternative than using cefpodoxime combination discs alone.

Screening of antibiotics resistance to Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii by an advanced expert system

The VITEK2 advanced expert system (AES) gives information about the antibiotics-resistance mechanisms based on the biological validation derived from the VITEK2 susceptibility result. In this study, we investigated whether or not this system correctly categorized the beta-lactamase resistance mechanism data derived from the VITEK2 susceptibility result using the testing card, AST-N025, with Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii. We used 131 strains, and their phenotypes were determined according to the biological and genetic screening. The AES analysis result matched the phenotype testing in 120 (91.6%) of the 131 strains. Incorrect findings were found in six strains, including three strains of Serratia marcescens. The resistance mechanism could not be determined in five strains, including three strains of Providencia rettgeri. The analysis of those phenotypes agreed in 34 (97.1%) among 35 strains with extended spectrum beta-lactamase (ESBL), and in 27 (96.4%) among 28 strains with high-level cephalosporinase. The agreement ratio in the phenotype was very high as we expected. The incorrect and nondeterminable samples were strains with relatively high cephalosporinase that has variation of outer membrane protein. The AES was able to detect the phenotype for carbapenemase. The AES is a clinically useful system that allows taking prompt measures to treat patients because it can provide information about the resistance mechanism in less than half a day after starting the analysis.

Antimicrobial susceptibility testing of vancomycin-resistant Enterococcus by the VITEK 2 system, and comparison with two NCCLS reference methods

We evaluated the automated VITEK 2 system (bioMerieux) for antimicrobial susceptibility testing of vancomycin-resistant Enterococcus (VRE). The results obtained with the VITEK 2 system were compared to those obtained using two NCCLS reference methods. The VITEK 2 system produced MICs for penicillin G, erythromycin and vancomycin that were very similar to those of the reference agar-dilution test with all results being within a twofold dilution. When MICs of teicoplanin for these isolates were measured by the agar-dilution method and VITEK 2 system, there was one 'very major' error and seven 'minor' errors. There were no 'major' errors for any of the antibiotics tested. When the results obtained by the micro broth-dilution method were compared with those obtained by the VITEK 2 system, there was one 'very major' error for teicoplanin by the VITEK 2 system, as was the case with the agar-dilution method. There were two 'minor' errors for erythromycin and seven 'minor' errors for teicoplanin. There were no 'major' errors for any of the antibiotics tested. The 35 VRE strains identified phenotypically by the VITEK 2 Advanced Expert System included nine of Enterococcus faecalis and 23 of Enterococcus faecium. Neither Enterococcus avium nor Enterococcus hirae were identified. A total of 32 phenotypes were classified into 22 VanA and 10 VanB strains. PCR genotyping demonstrated 23 vanA+ and nine vanB+ strains. There were differences between the VITEK 2 system results and those of PCR. Overall, 54.3 % of the test results were obtained within 7 h. All MIC values for the 35 VRE isolates were determined within 13 h of completing incubation. The VITEK 2 system is a simple method for accurately detecting vancomycin-resistant strains of Enterococcus and can be used to rapidly determine MICs.

Evaluation of VITEK 2 for analysis of Enterobacteriaceae using the Advanced Expert System (AES) versus interpretive susceptibility guidelines used at Dynacare Kasper Medical Laboratories, Edmonton, Alberta

To evaluate the applicability and adaptability of the bioMérieux VITEK 2 Advanced Expert System (AES) to the customized interpretive susceptibility guidelines used at Dynacare Kasper Medical Laboratories (DKML). Three hundred isolates of Enterobacteriaceae (not more than 30% Escherichia coli) were tested on the VITEK 2 system and the API 20E for identification. Susceptibility testing for these isolates was performed on the VITEK 2 system and the Pasco broth microdilution panels. Minimal inhibitory concentrations (MICs) and interpreted results according to the AES and DKML antimicrobial susceptibility guidelines were compared. Of 300 isolates tested for susceptibility, 13 did not give AES interpretations. Of the remaining 287 isolates, interpretations between AES and DKML guidelines were compared for 10 antibiotics. The overall correlation between the AES and DKML interpretations was 96.2%. This study demonstrated the benefits and limitations of the bioMérieux AES. Automated knowledge-based systems provide a useful laboratory tool for the interpretation of susceptibility results.

An advanced integrated expert system for wastewater treatment plants control: an addendum

An advanced integrated expert system for wastewater treatment plants control: an addendum

Killing the right bug. Phenotypic and genotypic approaches for identifying infectious agents and antibiotic resistance can help to slow the increasing antibiotic resistance among infectious bacteria.

When antibiotics became available after World War II, they were little short of a miracle. Since then, their ability to fight bacterial infections quickly and effectively has literally saved the lives of millions around the globe. But their efficiency has also been their greatest weakness, as people now rely on antibiotics to fight any infection whether it makes sense to use them or not. Added to which, most clinicians and physicians, under pressure to save time and money, will prescribe a broad‐spectrum one‐size‐fits‐all antibiotic to any patient with a bacterial infection rather than choosing a narrow‐spectrum antibiotic targeted to the specific causative pathogen. In the case of life‐threatening infections this is certainly justified. But this over‐use of antibiotics in hospitals and private practices has inevitably selected for resistant bacteria that are increasingly able to withstand the very drugs designed to combat them. Public health experts therefore urge clinicians and physicians to prescribe more narrow‐spectrum antibiotics in order to slow the spread of resistance among bacterial strains. But to do so, clinicians must know as soon as possible which bug they are dealing with and to which antibiotic the strain is susceptible, and this can take up to weeks using traditional culture‐based methods. Some automated systems are available to determine the infectious strain and its susceptibility to antibiotics within hours, but they come with a price. In the long run, therefore, they will most likely be replaced by DNA‐based solutions that will cost a fraction of traditional methods and will be able to indentify an infectious agent and its resistance in less than an hour. > The over‐use of antibodies in hospitals and private practices has inevitably selected for resistant bacteria that are increasingly able to withstand the very drugs designed to combat them The problem of emerging resistance is greatest in …

Ability of the VITEK 2 Advanced Expert System To Identify β-Lactam Phenotypes in Isolates of Enterobacteriaceae and Pseudomonas aeruginosa

The Advanced Expert System (AES) was used in conjunction with the VITEK 2 automated antimicrobial susceptibility test system to ascertain the beta-lactam phenotypes of 196 isolates of the family Enterobacteriaceae and the species Pseudomonas aeruginosa. These isolates represented a panel of strains that had been collected from laboratories worldwide and whose beta-lactam phenotypes had been characterized by biochemical and molecular techniques. The antimicrobial susceptibility of each isolate was determined with the VITEK 2 instrument, and the results were analyzed with the AES to ascertain the beta-lactam phenotype. The results were then compared to the beta-lactam resistance mechanism determined by biochemical and molecular techniques. Overall, the AES was able to ascertain a beta-lactam phenotype for 183 of the 196 (93.4%) isolates tested. For 111 of these 183 (60.7%) isolates, the correct beta-lactam phenotype was identified definitively in a single choice by the AES, while for an additional 46 isolates (25.1%), the AES identified the correct beta-lactam phenotype provisionally within two or more choices. For the remaining 26 isolates (14.2%), the beta-lactam phenotype identified by the AES was incorrect. However, for a number of these isolates, the error was due to remediable problems. These results suggest that the AES is capable of accurate identification of the beta-lactam phenotypes of gram-negative isolates and that certain modifications can improve its performance even further.

An advanced integrated expert system for wastewater treatment plants control

The activated sludge process is a commonly used method for treating wastewater. Due to the biological nature of the process it is characterized by poorly understood basic biological behavior mechanisms, a lack of reliable on-line instrumentation, and by control goals that are not always clearly stated. It is generally recognized that an Expert System (ES) can cope with many of the common problems relative with the operation and control of the activated sludge process. In this work an integrated and distributed ES is developed which supervises the control system of the whole treatment plant. The system has the capability to learn from the correct or wrong solutions given to previous cases. The structure of the suggested ES is analyzed and the supervision of the local controllers is described. In this way, the main problems of conventional control strategies and individual knowledge-based systems are overcome.

Antibiogramme automatisé et expertise : concept et application

A new generation of expert systems is under development. These systems are no longer based on interpretative rules which have several limitations since they are not universally accepted, expert-dependant and based on interpreted results. A new expert system developped by bioMérieux and provisionally named Advanced Expert System uses a data base including for each bacterial species distributions of published antibiotic MICs according to resistance mechanisms. These data are independant from experts and allow the description of phenotypes. The first step of the analysis of an antibiogram allows the biological validation on the basis of comparison of measured MICs to that of the data base for each resistance mechanism. This step represents a quality control of the susceptibility test. The next step is the therapeutic interpretation which is derived from the interpretative reading of antibiogram. The last step is the edition of commentaries for clinicians.

UHF partial discharge monitoring and expert system diagnosis

This paper examines the ultra high frequency (UHF) partial discharge (PD) measuring technique and its use in online monitoring for gas insulated substations (GIS). Taking two special PD defects as examples, some crucial aspects of PD monitoring are highlighted. Furthermore, the interpretation of measuring results is discussed on the basis of these examples, and an advanced expert system for automatic defect type interpretation is presented. Early fault recognition can be achieved by continuous UHF PD monitoring.

Design of Large Systems for Packaging and Launch on Multiple, Heterogeneous Vehicles

An algorithm to aid designers and planners of large integrated space systems requiring on-orbit assembly has been prototyped. This methodology is being implemented in an advanced knowledge-based expert system intended for conceptual design studies. Intended to work interactively with a commercial three-dimensional computer-aided design solid modeler, it studies the feasibility of packing multiple space system hardware elements into a given launch vehicle shroud. Previous study results have indicated that to minimize assembly complexity, while avoiding potentially unreliable deployments, the designers would have to either design systems that can be launched in a single large vehicle, or use multiple smaller vehicles and risk manifesting relatively inefficient launches (e.g. a low mass density truss with fluid and electrical systems installed). This algorithm is one of a suite of tools being developed to aid the conceptual design engineer in identifying and quantifying space vehicle design alternatives, and the corresponding launch vehicles and shrouds that minimize overall cost and mission risk from a launch and flight assembly operations perspective.

Advanced operation guidance system for 500 kV substation

An advanced expert system for operation guidance in a 500 kV substitution is presented. The system performance is significantly improved reflecting experience in developing the previous system. When a fault or trouble occurs in the substation, real-time interence from on-line information is executed, and guidance of the whole restoration process is offered on the operator's request. Histories of measured values are also presented using data from the equipment diagnosis system. Faults and troubles are identified by inference using detailed input informaton and knowledge on all equipment, relays, and situations. Frames and rules described in the knowledge base can be maintained easily by end-users with a knowledge-base maintenance utility. The system installed in a 500 kV switching station has been in actual use since February 1991 in good condition.

技を持ちファジィネスを扱えるエキスパートシステムの醸造への応用

[in Japanese]

Redex: The ranging equipment diagnostic expert system

This paper describes REDEX, an advanced prototype expert system that diagnoses hardware failures in the Ranging Equipment (RE) at NASA's Ground Network tracking stations. REDEX will help the RE technician identify faulty circuit cards or modules that must be replaced, and thereby reduce troubleshooting time. It features a highly graphical user interface that uses color block diagrams and layout diagrams to illustrate the location of a fault. A semantic network knowledge representation technique was used to model the design structure of the RE. A catalog of generic troubleshooting rules was compiled to represent heuristics that are applied in diagnosing electronic equipment. Specific troubleshooting rules were identified to represent additional diagnostic knowledge that is unique to the RE Over 50 genetic and 250 specific troubleshooting rules have been derived. REDEX is implemented in Prolog on an IBM PC AT-compatible workstation. Block diagram graphics displays are color-coded to identify signals that have been monitored or inferred to have nominal values, signals that are out of tolerance, and circuit cards and functions that are diagnosed as faulty. A hypertext-like scheme is used to allow the user to easily navigate through the space of diagrams and tables. Over 50 graphic and tabular displays have been implemented. REDEX is currently being evaluated in a stand-alone mode using simulated RE fault scenarios. It will soon be interfaced to the RE and tested in an online environment. When completed and fielded, REDEX will be a concrete example of the application of expert systems technology to the problem of improving performance and reducing the lifestyle costs of operating NASA's communications networks in the 1990's.