A Data Mining System for Infection Control Surveillance

Nosocomial infections and antimicrobial resistance are problems of enormous magnitude that impact the morbidity and mortality of hospitalized patients as well as their cost of care. The Data Mining Surveillance System (DMSS) uses novel data mining techniques to discover unsuspected, useful patterns of nosocomial infections and antimicrobial resistance from the analysis of hospital laboratory data. This report details a mature version of DMSS as well as an experiment in which DMSS was used to analyze all inpatient culture data, collected over 15 months at the University of Alabama at Birmingham Hospital.

Comparative genotyping of Streptococcus mutans by repetitive extragenic palindromic polymerase chain reaction and multilocus sequence typing

The genetic diversity of Streptococcus mutans has been extensively studied using a variety of genotyping methods. Repetitive extragenic palindromic-polymerase chain reaction (rep-PCR) is a genotyping approach used for screening large numbers of bacterial isolates. This two-part study used multilocus sequence typing (MLST) analysis to evaluate genotypes previously identified as unique using rep-PCR. In part one, an isolate was selected from each of the 22 S. mutans rep-PCR genotype groups representing 8000 clinical isolates. For part two, four additional isolates were selected from the six most commonly occurring genotype groups (GG) for further analysis. Real-time PCR was performed using eight housekeeping S. mutans gene loci and the amplicons were sequenced. Sequence data analysis was performed using CLC DNA Workbench and alleles were compared with the PubMLST database for Oral Streptococcus using the Nakano scheme. Concatenated sequences were evaluated with MEGA using a minimum evolution method with bootstrap. All 22 rep-PCR genotypes were unique by MLST analysis. Within rep-PCR GGs, MLST matched rep-PCR in three groups demonstrating clonality; three groups exhibited more diversity with MLST. The discovery of three clonal groups is unique to this study and suggests that S. mutans genotypes are shared between unrelated subjects. Furthermore, MLST defined 19 new alleles and 26 new sequence types that have been confirmed and registered with PubMLST. Methods for processing were streamlined and a process for using MLST with rep-PCR is suggested. In conclusion, MLST verified that rep-PCR is a reliable and cost-effective method for screening large numbers of S. mutans strains for epidemiological study.

Pneumocystis pneumonia in hospitalized patients: a detailed examination of symptoms, management, and outcomes in human immunodeficiency virus (HIV)-infected and HIV-uninfected persons

BACKGROUND

Pneumocystis jirovecii pneumonia (PCP) is a life-threatening infection for immunocompromised individuals. Robust data and clear guidelines are available for prophylaxis and treatment of human immunodeficiency virus (HIV)-related PCP (HIV-PCP), yet few data and no guidelines are available for non-HIV-related PCP (NH-PCP). We postulated that prevention and inpatient management of HIV-PCP differed from NH-PCP.

METHODS

We performed a retrospective case review of all pathologically confirmed cases of PCP seen at the University of Alabama Medical Center from 1996 to 2008. Data on clinical presentation, hospital course, and outcome were collected using a standardized data collection instrument. Bivariate analysis compared prophylaxis, adjunctive corticosteroids, and clinical outcomes between patients with HIV-PCP and NH-PCP.

RESULTS

Our analysis of the cohort included 97 cases of PCP; 65 HIV and 32 non-HIV cases. Non-HIV cases rarely received primary prophylaxis (4% vs. 38%, P = 0.01) and received appropriate antibiotics later in the course of hospitalization (5.2 days vs. 1.1 days, P < 0.005). Among transplant patients, NH-PCP was diagnosed a mean of 1066 days after transplantation and most patients were on low-dose corticosteroids (87%) at the time of disease onset. No significant differences in adjunctive corticosteroid use (69% vs. 77%, P = 0.39) and 90-day mortality (41% vs. 28%, P = 0.20) were detected.

CONCLUSIONS

Patients who have undergone organ or stem cell transplant remain at risk for PCP for many years after transplantation. In our cohort, patients who developed NH-PCP were rarely given prophylaxis, and initiation of appropriate antibiotics was significantly delayed compared to cases of HIV-PCP. Medical providers should be aware of the ongoing risk for NH-PCP, even late after transplantation, and consider more aggressive approaches to both prophylaxis and earlier empirical therapy for PCP.

Genetic diversity of plaque mutans streptococci with rep-PCR

Mutans streptococci (MS) are key organisms associated with the etiology of dental caries. Using probabilities that were tested by oversampling, we designed this study to determine the minimal number of MS isolates from an individual required to evaluate diversity of genotypes. MS isolates were genotyped by repetitive extragenic palindromic-polymerase chain-reaction (rep-PCR). Analysis of 20 isolates from individuals resulted in a mean of 1.6 and 2.4 genotypes in children (N = 12) and adults (N = 10), respectively. In a follow-up study, reducing the number of isolates to 7-10 resulted in a theoretical probability of up to 78% for detecting up to 4 genotypes. A mean of 1.5 genotypes was found in 35 children and 10 adults. These findings provide evidence for the design of studies of MS genotyping that can serve as a model for the analysis of genotypes within individuals.

Association between antecedent intravenous antimicrobial exposure and isolation of vancomycin-resistant enterococci

Vancomycin-resistant enterococci (VRE) have become important causes of nosocomial infections. This study evaluated the association between a variety of intravenous antimicrobial exposures and the isolation of VRE using two control groups: (1) a vancomycin-susceptible enterococci (VSE) group, to assess factors associated with development of VRE, and (2) a nonenterococci control group, to assess factors associated with positive cultures for enterococci without regard to vancomycin resistance. After adjusting for the effect of other antimicrobials, time at risk, and patient morbidity, compared to vancomycin-susceptible enterococci controls, exposures to imipenem (OR = 4.9, 95% CI = 1.6-14.1) and ceftazidime (OR = 2.6, 95% CI = 1.1-6.1) were significant predictors of VRE. When compared to nonenterococci controls, exposures to ampicillin (OR = 20.1, 95% CI = 1.5-263.1) and imipenem (OR = 5.1, 95% CI = 1.5-17.1) were significantly associated with VRE. Neither piperacillin nor vancomycin was associated with VRE compared to either control group. This study offers further evidence that the replacement of broad-spectrum cephalosporins by extended-spectrum penicillins, specifically piperacillin, may be effective in reducing VRE.

Vancomycin-resistant enterococci: 15 years and counting

We review the history of vancomycin-resistant enterococci (VRE) and propose a causal model illustrating the roles of exposure to VRE reservoirs, patient characteristics, antimicrobial exposure, and prevalence of VRE in the progression from potential VRE reservoirs to active disease in hospitalized patients. Differences in VRE colonization and VRE infection are discussed with respect to hospital surveillance methodology and implications for interventions. We further document clonal transmission of VRE in a large, urban, teaching hospital and demonstrate VRE susceptibility to a wide array of antimicrobial agents. This model can guide the identification of mutable factors that are focal points for intervention.

Bacteremia after spinal cord injury in initial versus subsequent hospitalizations

BACKGROUND

Individuals with spinal cord injury (SCI) have a high lifelong risk for systemic infection. For optimal therapy, it is important to characterize the organisms involved in bacteremic episodes and the sites of primary infection. The increase in drug-resistant bacteria in recent years underscores the importance of gathering accurate microbiological information.

METHODS

We performed a retrospective study of hospitalized people with SCI using a computerized Microbiology Laboratory Database. We compared the microbiology of bacteremic episodes during initial versus unplanned subsequent hospitalizations. Data were collected on 55 bacteremic episodes in 30 people during initial hospitalization for SCI and 50 episodes in 29 people who were rehospitalized.

RESULTS

Among cases in which a site of origin could be identified, the respiratory tract was the origin of the majority of bacteremias during initial hospitalizations, and the urinary tract was the primary origin during rehospitalizations. Polymicrobial bacteremia occurred in 14 of 55 (25%) initial versus 14 of 50 (28%) subsequent hospitalization episodes. The most common pathogens were coagulase-negative staphylococci, followed by Staphylococcus aureus and Enterobacteriaceae. Bacteremia was more common in people with tetraplegia and complete neurologic lesions than in those with paraplegia and incomplete lesions. One person in the rehospitalization group died from complications of bacteremia. All others were successfully treated.

CONCLUSIONS

This study describes the frequency and characteristics of bacteremia during initial and subsequent hospitalizations following SCI and examines differences in original sites of infection. This information should be considered when planning infection control measures and empiric antibiotic regimens for patients with SCI.

Genes encoding bile salt hydrolases and conjugated bile salt transporters in Lactobacillus johnsonii 100-100 and other Lactobacillus species

Lactobacillus johnsonii strain 100-100 expresses two antigenically distinct conjugated bile salt hydrolases (BSH), alpha and beta, that combine to form native homo- and heterotrimers. This paper reports characterization of loci within the genome that encode this capacity. A locus that encodes BSH beta (cbsH beta), a partial (cbsT1) and a complete conjugated bile salt transporter (cbsT2) was identified previously. DNA sequence analysis at this locus was extended and revealed a complete ORF for cbsT1 and no other ORFs in tandem. The three genes, cbsT1, cbsT2 and cbsH beta, probably constitute an operon; a putative promoter was identified upstream of cbsT1. A second locus that expresses BSH activity in strain 100-100 was identified. Sequence analysis of the clone predicted a 978 nt ORF that did not share tandem organization with other ORFs, was similar in sequence to other BSH genes, and matched, in predicted protein sequence, the first 25 amino acids of BSH alpha. A phenotypic screen for BSH activity and a genetic screen for the cbsH beta locus were performed on 50 Lactobacillus isolates from humans or dairy products. Nearly all of the isolates that were positive for cbsH beta were from human sources. Variability in the BSH phenotype and cbsH beta genotype was identified in isolates of the same species. DNA sequence was obtained and analysed from the cbsH beta locus of one human isolate, L. acidophilus strain KS-13. This organism has cbsT1, cbsT2 and cbs beta genes that are 84, 87 and 85% identical in DNA sequence to those of strain 100-100. DNA sequence identity to strain 100-100 ends in regions flanking this locus. The findings of this study suggest that BSH genes have been acquired horizontally and that BSH activity is important at some level for lactobacilli to colonize the lower gastrointestinal tract.

Bile salt hydrolase activity and resistance to toxicity of conjugated bile salts are unrelated properties in lactobacilli

Bacteria of numerous species isolated from the human gastrointestinal tract express bile salt hydrolase (BSH) activity. How this activity contributes to functions of the microorganisms in the gastrointestinal tract is not known. We tested the hypothesis that a BSH protects the cells that produce it from the toxicity of conjugated bile salts. Forty-nine strains of numerous Lactobacillus spp. were assayed to determine their capacities to express BSH activities (taurodeoxycholic acid [TDCA] hydrolase and taurocholic acid [TCA] hydrolase activities) and their capacities to resist the toxicity of a conjugated bile acid (TDCA). Thirty of these strains had been isolated from the human intestine, 15 had been recovered from dairy products, and 4 had originated from other sources. Twenty-six of the strains expressed both TDCA hydrolase and TCA hydrolase activities. One strain that expressed TDCA hydrolase activity did not express TCA hydrolase activity. Conversely, in one strain for which the assay for TDCA hydrolase activity gave a negative result there was evidence of TCA hydrolase activity. Twenty-five of the strains were found to resist the toxicity of TDCA. Fourteen of these strains were of human origin, nine were from dairy products, and two were from other sources. Of the 26 strains expressing both TDCA hydrolase and TCA hydrolase activities, 15 were resistant to TDCA toxicity, 6 were susceptible, and 5 gave inconclusive results. Of the 17 strains that gave negative results for either of the enzymes, 7 were resistant to the toxicity, 9 were susceptible, and 1 gave inconclusive results. These findings do not support the hypothesis tested. They suggest, however, that BSH activity is important at some level for lactobacillus colonization of the human intestine.

Trends in frequency and susceptibilities of Candida glabrata bloodstream isolates at a university hospital

The frequency of isolation and antifungal susceptibility patterns to fluconazole and itraconazole were determined for 166 Candida glabrata isolates causing bloodstream infection at a single institution from 1995-2000. Findings demonstrated a trend of increasing resistance to itraconazole among the isolates, but no trend in resistance to fluconazole. The frequency of C. glabrata isolates among all blood culture isolates of Candida spp. causing bloodstream infection remained stable during the study period and ranged from 18-31%.

A data mining system for infection control surveillance

Nosocomial infections and antimicrobial resistance are problems of enormous magnitude that impact the morbidity and mortality of hospitalized patients as well as their cost of care. The Data Mining Surveillance System (DMSS) uses novel data mining techniques to discover unsuspected, useful patterns of nosocomial infections and antimicrobial resistance from the analysis of hospital laboratory data. This report details a mature version of DMSS as well as an experiment in which DMSS was used to analyze all inpatient culture data, collected over 15 months at the University of Alabama at Birmingham Hospital.

Reduction of vancomycin-resistant enterococcal infections by limitation of broad-spectrum cephalosporin use in a trauma and burn intensive care unit

Both vancomycin and third-generation cephalosporin use are believed to contribute to a rise in vancomycin-resistant enterococci (VRE) infections. In 1998, the largest number of VRE infections in our hospital occurred in the trauma/burn intensive care unit (TBICU), accounting for nearly 20% of hospital infections. In an attempt to control the VRE infection rate, antibiotic protocols for prophylaxis, empiric, and definitive therapy were initiated during the final quarter of 1998 to minimize cephalosporin use by the introduction of piperacillin/tazobactam. Therefore, we undertook a study of the VRE infection rate for the TBICU in relation to vancomycin, piperacillin/tazobactam, piperacillin, third-generation cephalosporin, and total cephalosporin use before and after efforts to limit cephalosporins. These data were compared to those in the medical and surgical intensive care units. During 1998, seven VRE infections occurred in the TBICU. Following initiation of antibiotic protocols, one case of VRE infection occurred in the subsequent month and no cases in the 17 months since. The decrease in the VRE infection rate corresponded with a significant increase in the use of piperacillin/tazobactam and a reduction in third-generation and total cephalosporin use. In contrast, cephalosporin use in the medical and surgical intensive care units remains significantly higher than in the TBICU, and neither unit has had a reduction in their VRE infection rates.

Antimicrobial resistance in gram-negative bacteria isolated from the urinary tract in community-residing persons with spinal cord injury

OBJECTIVE

To assess the epidemiology of antimicrobial resistance among community-residing persons with spinal cord injury (SCI).

DESIGN

Retrospective analysis of existing data.

SETTING

Data were obtained from persons with SCI attending clinic for annual examinations.

PARTICIPANTS

Two hundred eighty-seven SCI outpatients.

INTERVENTION

None.

MAIN OUTCOME MEASURE

Occurrence of bacteriuria with gram-negative organisms demonstrating resistance to antimicrobial agents in 2 or more classes.

RESULTS

There were 706 gram-negative isolates from 444 urine specimens. Resistance to drugs in 2 or more classes occurred in 33% of bacterial isolates, but did not significantly increase in frequency among those injured for longer periods or more severely. Significantly higher rates of multidrug-resistant bacteria occurred in specimens from males, younger age group (< or =45 yrs), and persons with indwelling and condom catheters.

CONCLUSIONS

Antimicrobial resistance in outpatients with SCI is common and is related to widespread use of specific drugs, type of bladder management, and other host factors.

The effects of branched-chain amino acids on sow and litter performance

Sows (n = 306; PIC, Line C-19; average parity 2.1) were used to evaluate the interrelationship between valine, isoleucine, and leucine on sow and litter performance. Our objective was to determine whether the increase in litter weaning weight associated with added dietary valine is specific for valine or a result of the total branched-chain amino acid (i.e., isoleucine and[or] leucine) concentration of the diet. Eight dietary treatments (36 to 41 sows/treatment) were arranged as a 2 x 2 x 2 factorial with two levels of valine (.80 and 1.20%), isoleucine (.68 and 1.08%), and leucine (1.57 and 1.97%). This provided total branched-chain amino acid levels of 3.05, 3.45, 3.85, and 4.25%. The lowest level of each branched-chain amino acid was similar to that in a .90% lysine corn-soybean meal diet containing .15% L-lysine HCl. Amino acids other than valine, isoleucine, and leucine met or exceeded their suggested estimates relative to lysine using ratios derived from the National and Agricultural Research Councils. Average number of pigs on d 2 of lactation was 11.2, and average lactation length was 20.9 d. Number of pigs weaned (x = 10.6), sow ADFI (x = 5.85 kg), and sow weight loss (x = 4.25 kg) were not affected by dietary treatment (P > .10). Sow backfat loss (P < .02), litter weaning weight (P < .04), and litter weight gain from d 2 to weaning (P > .05) increased as dietary valine increased. Litter weight at weaning and litter weight gain were not affected by dietary isoleucine (P > .80) or leucine (P > .60). Sixteen or 17 sows per treatment (129 total) were milked manually on d 14 to 16 of lactation. Increasing dietary valine tended to increase milk urea N (P < .07) but did not affect milk DM, CP, fat, lactose, or ash. Increasing dietary isoleucine or leucine had no effects on milk composition. These results confirm the importance of dietary valine for increased litter weaning weight, independent of either additional dietary leucine or isoleucine.

Microascus cinereus (Anamorph scopulariopsis) brain abscess in a bone marrow transplant recipient

We report the first documented case of brain abscess due to the dematiaceous fungus Microascus cinereus, an organism common in soil and stored grain. M. cinereus was isolated from brain abscess material from a bone marrow transplant recipient. The patient responded well to treatment by amphotericin B lipid complex, itraconazole, and a craniotomy but later died from secondary complications caused by graft-versus-host disease.

Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group

BACKGROUND

The purpose of this study was to evaluate the safety and efficacy of a temperature-controlled radiofrequency catheter ablation system.

METHODS AND RESULTS

The patient population included 1050 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia (AVNRT), an accessory pathway (AP), or the atrioventricular junction (AVJ). Ablation was successful in 996 patients. The probability of success was highest among patients who had undergone ablation of the AVJ, lowest in patients who had undergone ablation of an AP, and in between for patients who had undergone ablation of AVNRT. A major complication occurred in 32 patients. Four variables predicted ablation success (AVJ, AVNRT, or left free wall AP ablation and an experienced center). Four factors predicted arrhythmia recurrence (right free wall, posteroseptal, septal, and multiple APs). Two variables predicted development of a complication (structural heart disease and the presence of multiple targets), and 3 variables predicted an increased risk of death (heart disease, lower ejection fraction, and AVJ ablation).

CONCLUSIONS

These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

Application of data mining to intensive care unit microbiologic data

We describe refinements to and new experimental applications of the Data Mining Surveillance System (DMSS), which uses a large electronic health-care database for monitoring emerging infections and antimicrobial resistance. For example, information from DMSS can indicate potentially important shifts in infection and antimicrobial resistance patterns in the intensive care units of a single health-care facility.

Comparison of the MB/BacT system with a revised antibiotic supplement kit to the BACTEC 460 system for detection of mycobacteria in clinical specimens

The MB/BacT system (MB/BacT) with a revised antibiotic supplement kit was compared with the BACTEC 460 system (BACTEC 460) in a test of 488 specimens submitted for mycobacterial culture from 302 patients. Twenty-four Mycobacterium tuberculosis isolates were detected by the BACTEC 460 versus 23 isolates by the MB/BacT. Mean time until detection of M. tuberculosis isolates identified by both systems was 11.9 days for the BACTEC 460 versus 13.7 days for the MB/BacT (P = 0.046). M. avium complex was detected in 12 specimens by the MB/BacT versus 10 specimens by the BACTEC 460. Only 8 of 14 (57%) M. avium isolates were detected by both systems, with a mean time until detection of 10.1 days for the BACTEC 460 and 14.2 days for the MB/BacT (P = 0.009). The BACTEC 460 and the MB/BacT detected M. gordonae in four specimens, but only a single specimen was positive by both systems. One M. fortuitum isolate and one of five M. kansasii isolates were recovered only by the BACTEC 460. The bacterial overgrowth rate was 7.0% for the MB/BacT versus 4.1% for the BACTEC 460. We found the MB/BacT to be comparable to the BACTEC 460 for mycobacterial detection. Even though time until detection with the MB/BacT was slightly longer (1.8 days longer for M. tuberculosis and 4.1 days for M. avium [mean values]) and the bacterial overgrowth rate was somewhat higher, the decreased labor, the availability of a computerized data management system, and the noninvasive, nonradiometric aspects of the MB/BacT offset these relative disadvantages and make it an acceptable alternative for use in the diagnostic laboratory.

Direct bacterial identification from positive BacT/Alert blood cultures using MicroScan overnight and rapid panels

Studies were conducted on a method of direct inoculation of MicroScan overnight and rapid panels from positive BacT/Alert blood culture bottles containing standard aerobic media to determine the correlation with inoculation of the corresponding panels with a standardized bacterial suspension obtained following subculture to agar. For Gram-negative organisms, 122 of 127 (96%) overnight panels and 85 of 118 (72%) rapid panels showed complete agreement with the standard method for species identification. Highest concordance (99%) occurred with Enterobacteriaceae inoculated directly into overnight panels. For Gram-positive organisms, 70 of 85 (82%) overnight panels and 45 of 86 (52%) rapid panels showed complete agreement. These findings suggest that direct inoculation of Gram-negative overnight MicroScan panels yields results most comparable to standard methods when Enterobacteriaceae are detected and allows reporting of results 18 to 24 h sooner. Direct inoculation of Gram-positive overnight or rapid panels and Gram-negative rapid panels from this blood culture medium did not yield acceptable identification results and is not recommended.

Direct susceptibility testing with positive BacT/Alert blood cultures by using MicroScan overnight and rapid panels

Studies were conducted on a method of direct inoculation of MicroScan dried overnight and of rapid panels with positive aerobic blood cultures obtained from the BacT/Alert to determine antimicrobial susceptibilities. Inocula were limited to specimens that appeared unimicrobic on Gram stain. Results were compared to those obtained from panels inoculated following subculture. For 133 gram-negative bacilli, there were 94.7 and 93.5% categorical agreements between direct and standard methods for all drugs tested with overnight and rapid panels, respectively. For 104 gram-positive cocci, there were 93.2 and 93.1% categorical agreements for overnight and rapid panels, respectively. The major error (false resistance) rate for gram negatives was 1.4% for overnight versus 0.7% for rapid panels. The very major error (false susceptibility) rate was 2.7% for overnight versus 8.1% for rapid panels. The total error rates were 1.6% for overnight panels and 1.5% for rapid panels. The major error rates for gram-positive direct susceptibility tests were 2.6% for overnight and 2.5% for rapid panels. The very major error rates were 8.8 and 7.2% for overnight and rapid panels, respectively. Total error rates were 3.6% for overnight and rapid gram-positive panels. These findings suggest that susceptibility results obtained from directly inoculated gram-negative overnight panels have the greatest correlation to those obtained by standard methods. When discrepant results occur with direct-susceptibility testing, they are more likely to show false susceptibility than false resistance.

Comparison of two rapid latex agglutination tests for detection of cryptococcal capsular polysaccharide

The Murex Cryptococcus Test was compared with the Cryptococcal Antigen Latex Agglutination System (CALAS) for detecting cryptococcal polysaccharide in 173 cerebrospinal fluid (CSF) specimens and 117 serum samples with 99% and 97% concordance, respectively. Eighteen CSF samples and 17 serum samples were positive in both assays, and 249 were negative. The sensitivity and specificity of the Murex relative to the CALAS were 90% and 100%, respectively, for CSF, and 81% and 100%, respectively, for serum. Six discrepancies were arbitrated by retesting, using a third analytic method, review of other laboratory and clinical data, or both. The reaction in 1 CSF specimen was considered false positive by the CALAS, and the reactions in 2 serum samples were false negatives by the Murex. For 3 patients with previous cryptococcal meningitis but no active disease, only the CALAS detected antigen, suggesting that the Murex has less analytic sensitivity in this context. Titer differences dictate that direct comparisons between the 2 tests are not feasible. There were no false-positive reactions in limited testing with either method using specimens from patients with concurrent noncryptococcal infections or in rheumatoid factor-positive serum samples. Infections caused by Cryptococcus neoformans serotypes A or AD were detected equally by both assays. Based on our study, we have elected to continue to use the CALAS for routine testing for cryptococcal antigen.

Pathology information systems: data mining leads to knowledge discovery

Information systems in pathology provide opportunities for pathologists and clinical laboratory scientists to impact both clinical care and modern research agendas. The paradigm shift in health care from individualized care to population-based and standardized delivery systems has created both of these opportunities. In research, pathology information systems can provide key databases for health services research and new informatics-based approaches to database research. The latter is characterized by utilization of pathology databases for data mining to discover new patterns that provide new knowledge. The multidisciplinary knowledge discovery and data mining program at the University of Alabama at Birmingham focuses on this health care application, which has the potential to make a major impact on health care research and delivery.

Cytokine involvement in immunomodulatory activity affected by Candida albicans mannan

Candida albicans mannoprotein (MAN) administered intravenously to mice stimulates the production of splenic CD8+ effector cells which downregulate delayed hypersensitivity (DH) in immunized mice. Cytokine involvement in the induction and/or elicitation of downregulation was studied by (i) examining murine splenocytes qualitatively for mRNA for interleukin-2 (IL-2), IL-4, IL-10, IL-12p40, and gamma interferon (IFN-gamma), (ii) quantitating splenocyte mRNA for IL-12p40 by quantitative-competitive reverse transcriptase-mediated PCR, and (iii) measuring serum levels of IL-12p40 and IL-12p70 by capture enzyme-linked immunosorbent assay, each performed at selected intervals over 96 h after giving MAN. Further, the effect of in vivo administration of anti-IL-4 on the induction and elicitation of MAN-specific DH in MAN-treated mice was measured. Expression of IL-12p40 mRNA in the spleen was reduced to near 0 during the first 24 h but rebounded thereafter. Transcripts for IL-10 were present throughout the 96-h period, whereas those for IL-4 and IFN-gamma were either weak or undetectable prior to 24 to 48 h. In vivo administration of anti-IL-4 partially abrogated the downregulatory effect of MAN only when given at the time of MAN administration. Serum levels of IL-12p40, but not IL-12p70, were increased by 24 h and maximal at 48 h. The antagonistic effect of IL-12p40 could contribute to the mechanism(s) for downregulation of DH. Moreover, IL-10, IL-4, and/or IFN-gamma, interacting with MAN-activated cells in the absence of biologically active IL-12, may induce the production of CD8+ downregulatory effector cells. Partial abrogation of downregulatory activity in animals treated with anti-IL-4 at the time of induction of such activity lends support to this hypothesis.

Association rules and data mining in hospital infection control and public health surveillance

OBJECTIVES

The authors consider the problem of identifying new, unexpected, and interesting patterns in hospital infection control and public health surveillance data and present a new data analysis process and system based on association rules to address this problem.

DESIGN

The authors first illustrate the need for automated pattern discovery and data mining in hospital infection control and public health surveillance. Next, they define association rules, explain how those rules can be used in surveillance, and present a novel process and system--the Data Mining Surveillance System (DMSS)--that utilize association rules to identify new and interesting patterns in surveillance data.

RESULTS

Experimental results were obtained using DMSS to analyze Pseudomonas aeruginosa infection control data collected over one year (1996) at University of Alabama at Birmingham Hospital. Experiments using one-, three-, and six-month time partitions yielded 34, 57, and 28 statistically significant events, respectively. Although not all statistically significant events are clinically significant, a subset of events generated in each analysis indicated potentially significant shifts in the occurrence of infection or antimicrobial resistance patterns of P. aeruginosa.

CONCLUSION

The new process and system are efficient and effective in identifying new, unexpected, and interesting patterns in surveillance data. The clinical relevance and utility of this process await the results of prospective studies currently in progress.

Genotypic investigation of multidrug-resistant Acinetobacter baumannii infections in a medical intensive care unit

Multi-resistant Acinetobacter baumannii isolates obtained from 13 hospitalized patients over a six-month period were evaluated. One patient had an isolate susceptible only to imipenem; the next three had isolates susceptible to imipenem and ampicillin/sulbactam; the next six patients had isolates which were susceptible to imipenem, amikacin, and ampicillin/sulbactam; while the final three patients had isolates which were susceptible to imipenem and ampicillin/sulbactam. Ten patients died, five within 10 days of a positive culture. Five of six patients with bacteraemia succumbed to the infection. DNA extracted from all isolates was amplified by polymerase chain reaction using four random primers (RAPD). The resulting band patterns were compared and strains identified. In addition, all isolates were biotyped. RAPD analysis and biotyping showed that there were two distinct strains involved. The first four patients were infected with one strain (genotype ¿A', biotype 9), the subsequent nine patients were infected with a second strain (genotype ¿B', biotype 1). These results suggested that there was patient-to-patient spread of strains. Institution of, and strict adherence to, isolation procedure and other infection control practices controlled the spread of infection. These data emphasize the need for active surveillance for multidrug-resistant organisms in critically ill patients, and the value of molecular typing of strains in a hospital setting to investigate spread of infection.

Alterations to the cell wall of Histoplasma capsulatum yeasts during infection of macrophages or epithelial cells

Many Histoplasma capsulatum strains have alpha-(1,3)-glucan in their cell walls and spontaneously produce variants that lack this polymer. The variants, in contrast to the parents, exist in aberrant shapes within macrophages. Here, the ultrastructure of the parental and variant cell walls was examined. All yeasts had identical electron-lucent, thick walls when grown in broth culture. However, ingestion by either macrophages or hamster trachea epithelial (HTE) cells caused the walls of variants to become electron-dense, thin, and sinuous. Parental strains remained unchanged in macrophages. Within HTE cells inoculated with parental strains, some organisms retained a thick wall and alpha-(1,3)-glucan but appeared to be degrading. In contrast, apparently intact intracellular yeasts had thin, wavy walls lacking alpha-(1,3)-glucan. A microenvironment within HTE cells that is unfavorable for the parental phenotype may trigger this ultrastructural change, potentially explaining why only variant yeasts are harvested from such cultures.

Comparative in vitro antimicrobial susceptibilities of nosocomial isolates of Acinetobacter baumannii and synergistic activities of nine antimicrobial combinations

The in vitro susceptibilities of 69 nosocomial Acinetobacter isolates were determined by the broth microdilution method. Fourteen (20%) isolates were resistant to at least two aminoglycosides and two extended-spectrum penicillins. Nine antimicrobial combinations were then tested for synergy against these 14 isolates by checkerboard titration: imipenem with ciprofloxacin, amikacin, and tobramycin and ampicillin-sulbactam, piperacillin-tazobactam, and ticarcillin-clavulanate with amikacin and tobramycin. Synergy was detected with one or more antimicrobial combinations against 9 of 14 (64%) isolates, partial synergy was detected with one or more combinations against all 14 isolates, and an additive effect alone was observed with two different combinations against two isolates. No antagonism was detected with any combination. Imipenem plus either amikacin or tobramycin resulted in a synergistic or partial synergistic response against all 14 isolates. Specific combinations showing synergy against A. baumannii isolates were imipenem with tobramycin (four isolates), imipenem with amikacin (three isolates), ampicillin-sulbactam with tobramycin (six isolates), ampicillin-sulbactam with amikacin (three isolates), and ticarcillin-clavulanate with tobramycin (one isolate). Genotyping by randomly amplified polymorphic DNA analysis showed that 9 of the 14 isolates were of one strain, 4 isolates were of a second strain, and the remaining isolate was of a different strain. Eight of 14 (57%) patients infected with resistant A. baumannii isolates died. Only 3 of 14 patients had received a therapeutic regimen which was tested for synergy. Clinical studies are needed to determine the significance of these findings.

Automating clinical practice guidelines: a corporate-academic partnership

Implementation of guidelines offers one of the largest opportunities for quality improvement, utilization review, and cost control for the health-care enterprise. If guidelines could be implemented on a large scale, their adoption could result in $100 billion in annual savings as well as improve the quality of patient care. However, infrastructural barriers impede progress. Collaboration between the Laboratory Medicine Health Services Program at the University of Alabama at Birmingham, Columbia-Presbyterian Medical Center, and the Cerner Corporation, funded by the National Institute of Standards and Technology as part of the Advanced Technology Program involving ¿Information Infrastructure for Healthcare,¿ is focused on developing and delivering: 1) methods for creating operational forms of guidelines; 2) an effective computer-based architecture for implementing guidelines in clinical practice; 3) methods for packaging guidelines for wide distribution; 4) methods for testing the efficacy, safety, and acceptability of guidelines; and 5) a model for collecting, aggregating, and normalizing data from disparate systems. This hypothesis-driven research program is focused on laboratory medicine-based guidelines as a tool for developing, testing, and evaluating methods that can be implemented widely.

Detection of oxacillin-resistance in Staphylococcus aureus by MicroScan MIC panels in comparison to four other methods

Two hundred fifty-two isolates of Staphylococcus aureus were tested for oxacillin susceptibility by MicroScan Gram positive overnight and rapid MIC panels. Results were compared with nonautomated methods including disk diffusion, MRSA Crystal ID, and Etests using MRSA Screen Agar as reference. One hundred sixty-nine isolates (67.1%) were oxacillin-susceptible and 83 (32.9%) were resistant. All methods agreed for 234 (92.9%) isolates. Very major error rates were 1.2% for disk diffusion, 3.6% for Etest, and 0 for all other methods. Major error rates were 5.3% for MicroScan overnight panels, 3% for rapid panels, 2.4% for disk diffusion, 1.2% for Etest, and 0.6% for MRSA Crystal ID. Nine oxacillin-susceptible isolates with borderline MICs and discrepant results for 1 or more methods were tested for the mec A gene and all were negative. Each was susceptible to beta lactam/beta lactamase inhibitor combinations, suggesting that false resistance may have been due to excessive beta lactamase production. Oxacillin-resistant S. aureus with borderline MICs determined by MicroScan should be confirmed by an alternate method. The most practical and cost-effective means among those we tested is the MRSA Screen Agar.

Comparison of four DNA-based methods for strain delineation of Candida lusitaniae

Four methods for the accurate delineation of epidemiologically related and unrelated strains of Candida lusitaniae were compared. Three pulsed-field electrophoretic methods, including two contour-clamped homogeneous field gel electrophoresis methods (EKP-1 and EKP-2) yielding electrophoretic karyotype patterns of intact chromosomal DNA and a method in which the chromosomal DNA was macrodigested with the endonuclease SfiI prior to pulsed-field electrophoresis (MDP), and a random amplified polymorphic DNA (RAPD) assay were evaluated. A selected panel of 21 well-characterized isolated representing 13 strains of C. lusitaniae, including 7 epidemiologically related isolates of one strain (group I-A), 3 epidemiologically related isolates of another strain (group I-B), and 11 epidemiologically unrelated isolates (group II), were tested. All isolates were coded and tested in a blinded manner. All seven group I-A isolates were confirmed to be a single strain by the EKP-1 and MDP methods, and the three group I-B isolates were shown to be a single strain by the EKP-1, EKP-2, MDP, and RAPD methods. Subtle differences were noted with two of the group I-A isolates by the EKP-2 method, whereas three of these isolates were different by the RAPD method. Each group II isolate had distinct patterns by all four methods. These data support the fact that the three pulsed-field electrophoretic methods and the RAPD method can be used to delineate strains of C. lusitaniae. The EKP-1, EKP-2, and MDP gave results that correlated with the epidemiologic characteristics of the isolates tested in the study, whereas the RAPD method was perhaps too sensitive in detecting DNA changes for epidemiologic studies.

Usefulness of follow-up electrophysiologic study and event monitoring after successful radiofrequency catheter ablation of supraventricular tachycardia. Atakr Multicenter Investigators Group

We assessed the usefulness of routine follow-up electrophysiologic studies after successful catheter ablation for supraventricular tachycardia and the role of event monitoring as an alternative modality in 310 patients at 11 centers using an investigational catheter ablation system with closed-loop temperature control. A routine follow-up electrophysiologic study between 1 and 3 months after ablation was required as part of the study protocol, and patients developing palpitations after ablation were encouraged to use event monitors. Recurrence of the initially targeted arrhythmia developed in 23 patients (7.4%) at a mean of 1.5 +/- 1.5 months after ablation. However, only 2 of these 23 recurrences were discovered by routine follow-up electrophysiologic study in asymptomatic patients (both with concealed accessory pathways); in the remaining 21 patients a positive follow-up electrophysiologic study was heralded by either recurrent symptoms, documented recurrent supraventricular tachycardia, and/or preexcitation on the electrocardiogram. Eighteen patients complained of palpitations after ablation and received an event monitor, which correctly diagnosed another cause of palpitations and ruled out recurrence of the ablated arrhythmia in 8 patients. Thus, the combination of clinical follow-up and event monitoring appears to be an effective alternative to routine follow-up electrophysiologic studies after catheter ablation of supraventricular tachycardia.

Development of pulmonary infection in mice inoculated with Blastomyces dermatitidis conidia

Intratracheal injection of Balb/cByJ mice with 10(4) Blastomyces dermatitidis conida produces chronic pulmonary and disseminated blastomycosis characterized by pyogranulomatous inflammation. To study the evolution of the pulmonary infection, mice were killed at varying intervals after inoculation, their lungs cultured and examined histologically. Nodular intraalveolar infiltrates of macrophages (M phi) were seen on Day 1 with occasional admixed polymorphonuclear leukocytes (PMN). Phagocytized yeast forms within M phi were evident by Day 5. By Day 28 pyogranulomas, which developed first as central microabscesses associated with a peripheral zone of M phi and giant cells containing internalized yeast, were a prominent feature of the infection. Lymphocytic and plasmacytic infiltrates, accumulating next to granulomas, formed the major peripheral component of the granuloma by Day 35. Formation of pyogranulomas was coincident with the host's failure to contain fungal growth measured by the sharp rise in colony-forming units recovered from lungs. Antibody against B. dermatitidis was first detected at Day 35 by enzyme immunoassay, but not until Day 63 by double immunodiffusion. During the 4 wk after inoculation, pulmonary lavage fluid contained > 90% M phi and < 3% PMN. On day 28, PMN rose to 17%, reaching 40% on Day 42. These data contribute to our knowledge of this model and help form the basis for investigations into the roles of fungal pathogenic and host defense mechanisms in blastomycosis.

Interleukin-1 is linked to the respiratory epithelial cytopathology of pertussis

Bordetella pertussis, the causative agent of whooping cough, releases a muramyl peptide known as tracheal cytotoxin (TCT) that is responsible for destruction of ciliated epithelial cells lining the large airways. In vitro, TCT has been shown to cause this specific pathology in human or hamster respiratory epithelium and to inhibit the proliferation of cultured hamster trachea epithelial cells. The diverse biological actions of muramyl peptides, including adjuvanticity, somnogenicity, and pyrogenicity, have been correlated with the production and release of the inflammatory mediator interleukin-1 (IL-1). Consistent with its ability to reproduce other muramyl peptide actions, recombinant IL-1 caused TCT-like damage to the respiratory epithelium. In the nanogram-per-milliliter range, exogenous IL-1 inhibited DNA synthesis in hamster trachea epithelial cells and reproduced the pathology of TCT in hamster tracheal organ culture. Tumor necrosis factor alpha and IL-6, cytokines also associated with inflammation, were unable to reproduce TCT cytopathology. Furthermore, exposure of respiratory epithelial cells to TCT stimulated production of cell-associated IL-1 alpha, which could be detected within 2 h of TCT treatment. In contrast, there was no evidence of TCT-triggered release of IL-1. Previous studies have suggested that intracellular IL-1 alpha, as well as exogenous IL-1 alpha and IL-1 beta, can inhibit cell proliferation. Our results therefore implicate IL-1 alpha, produced by epithelial cells in response to TCT, as a potential intracellular mediator of the primary respiratory cytopathology of pertussis.

IL-1-induced murine osteoblast IL-6 production is mediated by the type 1 IL-1 receptor and is increased by 1,25 dihydroxyvitamin D3

IL-1-induced osteoblast IL-6 production represents one possible mechanism by which IL-1 augments bone resorption. In this report, we show that the murine osteoblastic cell line (MC3T3-E1) expresses type 1 IL-1 receptors based on 125I-HrIL1 alpha binding, blocked by type 1 IL-1R antibodies (35F5), and analysis of MC3T3 RNA by reverse transcription (RT)-DNA amplification and Northern analysis. MC3T3 cells do not express detectable type 2 IL-1R mRNA by RT-DNA amplification. IL-1 induces (IL-1 ED50, 0.1 pM) IL-6 production through the type 1 IL-1R as 35F5 antibodies block IL-1-stimulated IL-6 production. Vitamin D3 increases IL-1R expression dose- and metabolite-dependently, with 1,25-(OH)2D3 having the greatest potency, and also enhances IL-1's capacity to stimulate IL-6 production at low IL-1 levels. Both IL-1 and 1,25-(OH)2D3 induce type 1 IL-1R and not type 2 IL-1R upregulation based on ligand binding and RT-DNA amplification. Increased IL-1R expression requires a 5-7-h treatment and is protein/RNA synthesis dependent. These observations imply that IL-1-induced IL-6 production in osteoblasts is mediated by type 1 IL-1Rs and that increased IL-1R expression could play a role in mediating IL-1-induced skeletal responses.

Updated care guidelines for patients with automatic implantable cardioverter defibrillators

Since its clinical introduction, AICD therapy has gained significant acceptance. Some physicians consider it the "gold standard" in treating malignant tachyarrhythmias associated with sudden cardiac death. As the technology and therapy application have grown, nursing responsibilities have evolved as well. And, with the forthcoming combinations of technology such as AICDs with antitachycardia pacing and bradycardia pacing, the sophistication of the therapy is expected to increase. However, the most critical role for nurses in AICD patient care remains education. Increased utilization has made AICD implants more common, but many patients still lack the initial information and acceptance needed for therapeutic success. Health-care professionals who continue to update and share their understanding of this life-saving technology make invaluable contributions to the care of these patients who have received a second chance at life.

Updated care guidelines for patients with automatic implantable cardioverter defibrillators

Since its clinical introduction, AICD therapy has gained significant acceptance. Some physicians consider it the "gold standard" in treating malignant tachyarrhythmias associated with sudden cardiac death. As the technology and therapy application have grown, nursing responsibilities have evolved as well. And, with the forthcoming combinations of technology such as AICDs with antitachycardia pacing and bradycardia pacing, the sophistication of the therapy is expected to increase. However, the most critical role for nurses in AICD patient care remains education. Increased utilization has made AICD implants more common, but many patients still lack the initial information and acceptance needed for therapeutic success. Health-care professionals who continue to update and share their understanding of this life-saving technology make invaluable contributions to the care of these patients who have received a second chance at life.

Renal mucormycosis: a case report and review of the literature

A 64-year-old man presented with acute renal failure secondary to renal mucormycosis. The pathological findings are described and the literature is reviewed.

Implantable defibrillation: eight years clinical experience

Implantation of the first automatic defibrillator occurred in February 1980. Incorporation of cardioversion capability in 1982 resulted in the AICD automatic implantable cardioverter defibrillator. Between April 1, 1982 and April 15, 1988, 3610 patients in 236 U.S. and 84 international centers received AICD pulse generators. Patient population consisted of 2904 males and 683 females with recurrent ventricular tachycardia and/or fibrillation, mean age 59 yrs. (range 9-96 yrs.). Primary diagnoses reported for the patient group were: coronary artery disease (63.5%), nonischemic cardiomyopathy (12.9%), other (6.4%) and unspecified (17.2%). Mean reported LV ejection fraction was 32.8%. Follow-up averaged 12.2 mo. (range 0-72 mo.). Of 385 deaths, 94 (24%) were sudden. Cumulative percentage survival (+/- S.E.) from sudden cardiac death (SCD) was 98.0 +/- 0.3%, 96.5 +/- 0.5%, 95.2 +/- 0.7%, 93.7 +/- 1.0%, 93.7 +/- 1.0% and 89.7 +/- 4.0% at 12, 24, 36, 48, 60 and 72 months, respectively. Operative mortality (less than or equal to 30 days) was 2.5%. Reported side effects/complications were similar to those of pacemakers. To date, 33% of the patients received spontaneous device countershocks. AICD pulse generator survival from electrical and mechanical failures was 92.8 +/- 0.5%, 88.4 +/- 0.7%, 86.7 +/- 0.8% and 86.4 +/- 0.9% at 12, 18, 24 and 30 mos. Data analysis demonstrates that the AICD has had a significant impact on patient survival from SCD.

Sensing aberration by the automatic implantable cardioverter defibrillator during intraoperative testing

A 50-year-old man underwent replacement of his automatic implantable cardioverter defibrillator (AICD) because a magnet test revealed severe battery depletion. He had had his unit implanted 18 months previously after an episode of sudden cardiac death. He had documented torsades de pointes and inducible ventricular tachycardia, confirmed by electrophysiologic study. Before a new unit was implanted thresholds were measured by an external cardioverter defibrillator. Ventricular fibrillation (VF) was induced by alternating current through a standard, line-operated battery charger with stimulation delivered to the epicardium via rate-sensing electrodes. VF was allowed to continue for 10 seconds before shock was delivered. Termination of VF required 15 joules, which was higher than that required at initial implantation 18 months earlier. The new pulse generator was activated for testing and VF was again induced. The AICD discharged after 12.3 seconds. Prior to wound closing, the AICD was deactivated by magnet. Instead of R-wave synchronous beeping tones during deactivation, double beeping tones were heard. Electrogram recordings revealed abnormalities of the T-wave and ST segment of the rate-sensing electrodes, which were the cause of the tone irregularities. Stabilization of the T-wave and ST segment occurred within 8 minutes and the tones became normal. The procedure was then completed.

Fungal-strain-dependent alterations in the time course and mortality of chronic murine pulmonary blastomycosis

Intratracheal injection of 10(4) conidia of Blastomyces dermatitidis strain M1-A into mice was shown in previous work to induce chronic pulmonary and disseminated infection with histopathologic features of chronic human blastomycosis. Furthermore, 10-fold variations in inoculum density produced marked changes in mean survival times (MSTs), i.e., 32 days at 10(6), 36 days at 10(5), 97 days at 10(4), and 172 days at 10(3). A second strain (M1-B) failed to induce death in this model. To assess fungal-strain-dependent virulence, we extended these previous studies to 11 additional human isolates. Groups of male BALB/cByJ mice (6 to 8 weeks old) were injected intratracheally with 10(4) conidia from each of the 13 strains; the mice were weighed weekly and monitored for mortality, and their lungs were examined histopathologically. Infection rate and mortality were 100% in all groups except for the M1-B inoculated mice. For strains M1-B and M1-A, MST and mortality curves were not significantly different from those observed in our previously reported experiments. Four different survival patterns were noted in infected mice. The shortest MSTs were produced by strains M2-E, M2-B, M2-K, M2-H, and M2-A (24, 26, 26, 27, and 31 days, respectively), and the longest MST was seen in animal groups inoculated with strains M2-J and M2-G (130 and 134 days, respectively). Strains M2-I, M2-F, and M2-D produced intermediate MSTs of 65, 79, and 80 days, respectively. The 107-day MST induced by M1-A did not differ from strain M2-C-induced MST but differed significantly from the MST produced by the other strains. Pulmonary histopathology was similar in all animals dying with blastomycosis. The wide spectrum in survival times was not related to differences in clinical status of the patient from whom the isolate had been obtained, to fungal inoculum viability, or to individual mouse weight at inoculation. Strain-dependent virulence factors present in these fungal isolates alter the disease course in inbred mice in a fashion similar to that induced by 10-fold inoculum variation of strain M1-A conidia. These 13 isolates of B. dermatitidis, 1 avirulent and 12 with differing levels of virulence, provide tools for future studies into the nature of fungal virulence determinants in chronic blastomycosis.

Chronic murine pulmonary blastomycosis induced by intratracheally inoculated Blastomyces dermatitidis conidia

Groups of 6-wk-old male BALB/cByJ mice were injected intratracheally (IT) with viable conidia from Blastomyces dermatitidis strains (FW or CR) harvested from 2-wk-old cultures (Pine-Drouhet agar at 30 degrees C) and separated from hyphal elements by polycarbonate filtration (5 micron). Inocula (0.05 ml) were 93 to 97% conidia in nonpyrogenic normal saline (NPNS) with greater than 90% viability. Quantitative cultures of the lungs and trachea of mice killed immediately after injection of 10(4) conidia (FW) confirmed that the inoculum was evenly distributed between the lungs, with virtually no conidia retained in the trachea. Animals were observed for 354 days for weight change, mortality, extrapulmonary dissemination and histopathologic changes. Mice inoculated with 10(4) FW began dying on Day 44, with a median survival of 92 days. A decrease in mean weight compared with that in control mice was noted by Day 55. In contrast, mice inoculated with 10(4) CR or NPNS neither died with blastomycosis nor lost weight in 329 days. Variation of the FW inoculum by tenfold increments produced comparable dose-dependent alterations in both mortality rate and weight change curves. Fifty percent survival was 32, 36, 92, or 172 days for mice inoculated with 10(6), 10(5), 10(4), or 10(3) conidia, respectively. Dissemination from the lungs to the liver, spleen, kidney, testis, and brain was found in the cachectic mice that were killed. Pathologic features of pulmonary and disseminated infections were comparable to those in human disease. This quantitative, reproducible model of chronic murine blastomycosis mimics the human disease in many respects and should provide a basis for future studies of the immunology, pathogenesis, and therapy of chronic blastomycosis.

Mexiletine for recurring ventricular arrhythmias: assessment by long-term electrocardiographic recordings and sequential electrophysiologic studies

Mexiletine, an oral lidocaine-like drug, was initially thought to be effective treatment for recurring ventricular arrhythmias. Recent work has cast doubt on its efficacy. We administered mexiletine to 32 patients with chronically recurring ventricular arrhythmias. In 22 patients with no history of syncope or documented sustained ventricular arrhythmia (group 1), mexiletine was effective in only 27% (six patients) as assessed by 24-hour ambulatory ECG recordings before and during mexiletine treatment. Ten other patients had a history of syncope or documented sustained ventricular tachycardia or ventricular fibrillation. Only 10% (one patient) responded to mexiletine based on sequential electrophysiologic studies with programmed ventricular stimulation. Four of the seven patients responding to mexiletine had not received prior antiarrhythmic therapy. We conclude that mexiletine has limited efficacy in the treatment of recurring drug-refractory ventricular arrhythmias.