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Biomedical subjects

L R Peterson

Publications and source records attributed to L R Peterson.

At least 19 recordsLinked to original sources
PubMed2005

Squeezing the antibiotic balloon: the impact of antimicrobial classes on emerging resistance.

The ongoing problem of emerging antimicrobial resistance has been likened to a balloon where settling one specific issue results in a 'bulge' of even worse problems. However, much has been learned about how to best use our critical antibacterial agents in ways to avoid or even repair some of the resistance damage that has been done. A compilation of current literature strongly suggests that to slow the development of resistance to antimicrobial agents it is optimal to use drugs with more than one mechanism of action or target, to prescribe those with demonstrated ability to minimise or reverse resistance problems, and to avoid underdosing of potent antibiotics. The most recent information also indicates that it is best to limit empirical use of beta-lactam plus fluoroquinolone combination therapy, since these two classes activate some common resistance responses, and using them together can facilitate multidrug resistance in important pathogens, particularly Pseudomonas aeruginosa and Acinetobacter species. This review discusses the role of each major antimicrobial class on resistance development and presents specific strategies for combating the growing problem of multidrug-resistant bacteria. We now have the knowledge to better manage our antimicrobial agent prescribing practices, but finding the will and resources to apply our understanding remains a formidable challenge.

Anti-Bacterial Agents↗
PubMed2004

Detection of vancomycin-resistant enterococci before and after antimicrobial therapy: use of conventional culture and polymerase chain reaction.

Antimicrobial therapy can increase the colonization density of gastrointestinal vancomycin-resistant enterococci (VRE). Among previously VRE-colonized patients, we evaluated VRE colonization before and after initiation of antimicrobial therapy by means of polymerase chain reaction (PCR) and culture. Perianal swab samples were obtained at admission to the hospital and after receipt of antimicrobial therapy. At admission, 12 (21%) of 56 patients were culture positive, and 17 (30%) had vanA or vanB genes detected by PCR. Culture results showed that 25 (86%) of 29 culture-negative patients from whom a second swab sample was obtained remained culture negative, 2 (6.9%) had a relapse of colonization with a strain related to the previously colonizing strain type (2 and 6 days after admission), and 2 (6.9%) tested positive for a previously undetected strain type (16 and 19 days after admission). PCR at admission detected VRE in 1 of the 2 patients who later relapsed. Patients with negative results of culture of the initial swab sample and of PCR were unlikely to relapse after receipt of antimicrobial therapy.

Adult↗
PubMed2002

Evaluation of the Vitek 2 system for rapid identification of clinical isolates of gram-negative bacilli and members of the family Streptococcaceae.

Accuracy of the Vitek 2 automated system (bioMérieux Vitek, USA) for rapid identification of bacteria was evaluated using a collection of 858 epidemiologically unrelated gram-negative and 99 gram-positive clinical isolates. Isolates were tested after subculturing to ensure purity. Conventional agar-based biochemical tests (Steers replicator) were used as a reference method of identification. Gram-negative bacteria were identified to the species level with 95.3% accuracy by the system ( Enterobacteriaceae, 95.9%; and non- Enterobacteriaceae, 92.5%), and gram-positive isolates with 72% accuracy. Although Vitek 2 identified routine clinical isolates of gram-negative bacilli and Enterococcus faecalis and Enterococcus faecium reliably, rapidly, and reproducibly, improvement is required in the identification of less common species of enterococci and viridans group streptococci.

Automation↗
PubMed2001

Fatal pseudomembranous colitis associated with a variant clostridium difficile strain not detected by toxin A immunoassay.

BACKGROUND: Many clinical laboratories use toxin A immunoassays to test for Clostridium difficile. OBJECTIVE: To describe the clinical course of a patient infected with a toxin variant strain of C. difficile that was not detected by toxin A immunoassay; to genetically characterize this strain; and to estimate the number of laboratories that use only toxin A immunoassays. DESIGN: Case report, molecular investigation, and laboratory survey. SETTING: Tertiary care hospital in Chicago, Illinois. PATIENT: An 86-year-old man. MEASUREMENTS: Restriction endonuclease analysis, polymerase chain reaction, and survey of regional clinical laboratories. RESULTS: An elderly hospitalized man died of advanced pseudomembranous colitis. Four stool specimens submitted over a 2-month period had tested negative on toxin A immunoassay, but a strain of C. difficile with a 1.8-kb deletion of the toxin A gene was recovered from each specimen. This strain, identified as restriction endonuclease analysis type CF4, is closely related to a widely disseminated variant, toxinotype VIII. Toxin A immunoassay was the only test being performed for detection of C. difficile at 31 of 67 (46%) regional clinical laboratories. CONCLUSIONS: Toxin A variant strains of C. difficile cause serious disease and are undetectable in clinical laboratories that use only toxin A immunoassays for C. difficile testing.

Aged↗
PubMed2001

Quinolone molecular structure-activity relationships: what we have learned about improving antimicrobial activity.

Recently, understanding of how molecular modifications of the core quinolone structure affect(s) antimicrobial agent activity has progressed rapidly. Three positions (2, 3, and 4) cannot be changed without a significant loss of biological activity. Furthermore, it appears that a cyclopropyl group is optimal at position 1. Substituents at positions 5 and 8 affect planar configuration, and either a methyl or methoxy appear optimal at these sites. Hydrogen and amino groups have been investigated as useful substituents at position 6, replacing the fluorine of the fluoroquinolones. Interestingly, in vitro activity enhancement observed with alterations at positions 5 and 6 is not always accompanied by improved in vivo action. For all these modifications, the substituents at positions 7 and 8 are critical for potent antimicrobial activity. Optimizing overall molecular configuration enhances the number of intracellular targets for antimicrobial action (R-8) and impedes the efficiency of efflux proteins (R-7) that diminish intracellular penetration.

4-Quinolones↗
PubMed2001

Role of clinical microbiology laboratories in the management and control of infectious diseases and the delivery of health care.

Modern medicine has led to dramatic changes in infectious diseases practice. Vaccination and antibiotic therapy have benefited millions of persons. However, constrained resources now threaten our ability to adequately manage threats of infectious diseases by placing clinical microbiology services and expertise distant from the patient and their infectious diseases physician. Continuing in such a direction threatens quality of laboratory results, timeliness of diagnosis, appropriateness of treatment, effective communication, reduction of health care-associated infections, advances in infectious diseases practice, and training of future practitioners. Microbiology laboratories are the first lines of defense for detection of new antibiotic resistance, outbreaks of foodborne infection, and a possible bioterrorism event. Maintaining high-quality clinical microbiology laboratories on the site of the institution that they serve is the current best approach for managing today's problems of emerging infectious diseases and antimicrobial agent resistance by providing good patient care outcomes that actually save money.

Communicable Disease Control↗
PubMed2001

Short-term oral estrogen replacement therapy does not augment endothelium-independent myocardial perfusion in postmenopausal women.

OBJECTIVES: The purpose of this study was to determine the effect of usual-dose estrogen replacement therapy (ERT) on myocardial perfusion and myocardial perfusion reserve (MPR) (evoked by an endothelium-independent vasodilator) in healthy postmenopausal women. Postmenopausal women have a decreased myocardial perfusion reserve compared with younger women. Estrogen infusions are known to enhance endothelium-dependent vasodilation of the epicardial coronary arteries in postmenopausal women, but whether ERT also enhances endothelium-independent myocardial perfusion and perfusion reserve is unclear. METHODS: In 24 healthy postmenopausal women who were not taking ERT, myocardial perfusion at rest, perfusion during the infusion of adenosine (a primarily endothelium-independent vasodilator), and MPR were determined by positron-emission tomography (PET) and oxygen 15-labeled water. The women were then randomly assigned in a double-blind fashion to receive either 0.625 mg of oral conjugated estrogens (Premarin) or placebo per day for 4 to 6 weeks, after which they underwent a repeat cardiac PET study. RESULTS: There was no statistical difference between those assigned to ERT and those assigned to placebo in the measurement of myocardial perfusion at rest (1.21 +/- 0.31 vs 1.16 +/- 0.18 mL/g/min, respectively) in response to adenosine (2.66 +/- 0.96 vs 3.3 +/- 0.45 mL/g/min) or MPR (2.24 +/- 0.83 vs 2.88 +/- 0.64 mL/g/min) after 4 to 6 weeks of oral ERT. There was also no difference between the groups in any of the myocardial perfusion measurements after correction for the rate-pressure product. CONCLUSIONS: Short-term oral ERT does not affect myocardial perfusion at rest in response to adenosine or MPR in healthy postmenopausal women. Thus potential beneficial effects of ERT on vasomotor function may be limited to enhancement of endothelium-dependent vasodilative mechanisms affecting conduit vessels.

Adenosine↗
PubMed2001

Paenibacillus macerans pseudobacteremia resulting from contaminated blood culture bottles in a neonatal intensive care unit.

Paenibacillus species are gram-positive, rod-shaped, spore-forming aerobes that are abundant in nature and closely related to Bacillus. Between June 24 and June 30, 1999, 8 neonates in our neonatal intensive care unit had positive blood cultures for Paenibacillus macerans. This cluster of positive blood cultures with an unusual pathogen suggested a pseudoepidemic. Investigation revealed that the most likely etiology of the pseudobacteremia was environmental contamination of the rubber stoppers in blood culture bottles. This was confirmed by environmental sampling and simulated inoculation studies. This pseudobacteremia outbreak highlights the importance of adhering to well-established methods for blood culture collection and ongoing infection control surveillance.

Bacillaceae Infections↗
PubMed2001

Resistance to linezolid: characterization of mutations in rRNA and comparison of their occurrences in vancomycin-resistant enterococci.

To assess the potential for emergence of resistance during the use of linezolid, we tested 10 clinical isolates of vancomycin-resistant enterococci (VRE) (four Enterococcus faecalis, five Enterococcus faecium, and one Enterococcus gallinarum) as well as a vancomycin-susceptible control (ATCC 29212) strain of E. faecalis. The enterococci were exposed to doubling dilutions of linezolid for 12 passes. After the final passage, the linezolid plate growing VRE contained a higher drug concentration with E. faecalis than with E. faecium. DNA sequencing of the 23S rRNA genes revealed that linezolid resistance in three E. faecalis isolates was associated with a guanine to uracil transversion at bp 2576, while the one E. faecium isolate for which the MIC was 16 microg/ml contained a guanine to adenine transition at bp 2505.

Acetamides↗
PubMed2001

Contamination of the clinical microbiology laboratory with vancomycin-resistant enterococci and multidrug- resistant Enterobacteriaceae: implications for hospital and laboratory workers.

We surveyed environmental surfaces in our clinical microbiology laboratory to determine the prevalence of vancomycin-resistant enterococci (VRE) and multidrug-resistant Enterobacteriaceae (MDRE) during a routine working day. From a total of 193 surfaces, VRE were present on 20 (10%) and MDRE were present on 4 (2%) of the surfaces tested. In a subsequent survey after routine cleaning, all of the 24 prior positive surfaces were found to be negative. Thus, those in the laboratory should recognize that many surfaces may be contaminated by resistant organisms during routine processing of patient specimens.

Colony Count, Microbial↗
PubMed2001

Yield of vancomycin-resistant enterococci and multidrug-resistant Enterobacteriaceae from stools submitted for Clostridium difficile testing compared to results from a focused surveillance program.

It has been suggested that a method of performing surveillance for vancomycin-resistant enterococci (VRE) is to screen specimens submitted for Clostridium difficile testing. We compared this approach to our focused surveillance program of high-risk units during October 1997 to compare the yield of VRE and multidrug-resistant Enterobacteriaceae (MDRE) with both methods. Of the stools submitted for C. difficile testing, 14% were positive for VRE or MDRE, whereas rectal swabs from routine surveillance yielded 11% VRE- or MDRE-positive results. Although stools submitted for C. difficile testing resulted in a higher percentage of positive cultures, 14 VRE- and 2 MDRE-positive patients from our high-risk population were missed because many patients had no stool submitted for C. difficile testing. Therefore, while screening stools submitted for C. difficile testing cannot replace our focused surveillance program, it appears advantageous to assess these stools at various intervals to detect new patient reservoirs of drug-resistant organisms that may benefit from routine surveillance cultures.

Clostridioides difficile↗
PubMed2001

Low Prevalence of Community-Acquired Methicillin-Resistant Staphylococcus aureus in Adults at a University Hospital in the Central United States.

Community-acquired MRSA (CA-MRSA) is potentially a new emerging pathogen with most strains susceptible to many antimicrobials except for beta-lactam antibiotics. We retrospectively reviewed MRSA isolates during a 20-month study period (January 1998 through August 1999) and investigated those that were clindamycin susceptible. Patients were not considered to harbor CA-MRSA if they had been admitted to a hospital within the preceding 2 years or if their isolate had been obtained more than 72 h after admission. There were 2,817 S. aureus isolates, with 1,071 (38%) being MRSA. Of these 1,071 isolates, 161 were clindamycin susceptible; these were recovered from 81 patients. Of these 81 patients, 20 appeared to have community-acquired strains, but only 2 could be confirmed as having CA-MRSA.

Adult↗
PubMed2001

Fluoroquinolone resistance is a poor surrogate marker for type II topoisomerase mutations in clinical isolates of Streptococcus pneumoniae.

The association between fluoroquinolone susceptibility and DNA mutations coding for amino acid substitutions in the quinolone resistance-determining region was assessed with 44 clinical isolates of Streptococcus pneumoniae. Twenty-three strains bore at least one amino acid substitution. Only seven strains with mutations were suggested by diminished susceptibility to ciprofloxacin (MIC, > or =2 microg/ml).

Amino Acid Substitution↗
PubMed2000

The incidence of antimicrobial allergies in hospitalized patients: implications regarding prescribing patterns and emerging bacterial resistance.

BACKGROUND: The development of antimicrobial guidelines is one way in which institutions attempt to control emerging resistance, but the real challenge falls on promoting and ensuring adherence to these guidelines. Investigating reasons for the prescribing of alternative antimicrobial agents outside of these guidelines is crucial for modifying practices that may adversely impact institutional antimicrobial goals. METHODS: Retrospective cross-referencing of computerized pharmacy printouts and concurrent manual medical record review. RESULTS: Approximately 25% (470/1893) of the patients requiring antimicrobial therapy reported an allergy to at least 1 antimicrobial agent. The most commonly reported antimicrobial allergy was penicillin (295/1893 [15.6%]). Eighty-five patients (18.1%) reported having an allergy to 2 or more antimicrobial agents. Only 4% (27/601) of the reported antimicrobial allergies contained documentation as to the nature of the specific allergic reactions, while a manual medical record review revealed that 32% (23/73) of the antimicrobial allergies contained documentation of the specific allergic reaction. Ninety-eight (39. 7%) of 247 patients reporting an allergy only to penicillin and/or cephalosporin received vancomycin in comparison with 247 (17.4%) of 1423 patients without any antimicrobial allergies (P<.001). Similarly, 53 (21.5%) of 247 patients with reported penicillin and/or cephalosporin allergies received levofloxacin compared with 114 (8.0%) of 1423 patients without any antimicrobial allergy (P<. 001). CONCLUSION: The incidence of penicillin allergy at our institution exceeds population averages. This finding, in combination with limited documentation of drug allergies, appears to lead to the prescribing of alternative antimicrobial agents that do not fit into institutional antimicrobial guidelines and, in some instances, may put the patient at risk for infection and/or colonization with resistant organisms. Use of these alternative agents may adversely impact the ability to manage emerging antimicrobial resistance.

Anti-Bacterial Agents↗
PubMed2000

Activity of voriconazole against Candida albicans and Candida krusei isolated since 1984.

With the recent dramatic rise in fluconazole use, there has been an increase in Candida species resistant to that agent. This has led to the clinical development of newer triazoles such as voriconazole that have greater potency and a broader spectrum of activity. We therefore hypothesized that fluconazole-resistant Candida albicans and Candida krusei would be susceptible to voriconazole. Susceptibility testing was performed on 205 isolates of C. albicans collected from 1984 to 1995, and on C. albicans and C. krusei that were identified as fluconazole resistant since 1995. The anti fungal agents used were amphotericin B, 5-flucytosine, itraconazole, ketoconazole, fluconazole and voriconazole. Three C. albicans and 26 C. krusei isolates had a minimum inhibitory concentration (MIC) >/=20 mg/l and were defined as fluconazole resistant. Of these, 28 isolates were susceptible to </=2.5 mg/l voriconazole, with a mean MIC of 0.78 mg/l. The mean amphotericin B MIC for these same strains was 0.98 mg/l. Only one isolate of C. krusei was relatively resistant to voriconazole with a MIC of 5 mg/l. Of these 29 isolates, there were ten amphotericin-resistant strains of C. krusei (MIC>2 mg/l) but all were susceptible to </=2.5 mg/l voriconazole. The higher potency of voriconazole may be useful in the treatment of fluconazole- and amphotericin-resistant C. albicans and C. krusei.

Antifungal Agents↗
PubMed2000

Persistent contamination of fabric-covered furniture by vancomycin-resistant enterococci: implications for upholstery selection in hospitals.

Vancomycin-resistant enterococci (VRE) have emerged as important nosocomial pathogens in hospitals throughout the United States. An increasing concern with respect to VRE dissemination is survival on, and potential transmission from, environmental surfaces within health care institutions. Therefore, we assessed survival of VRE on fabric chairs in an attempt to determine the optimal upholstery for the health care setting. VRE was identified on 3 of 10 seat cushions sampled, including 2 chairs in a room of a patient with known VRE. After performing simulated contamination experiments, all samples were positive at 72 hours and 1 week after inoculation. Contamination of the upholstery could be prevented by placing a sheet folded 4 times or a bath blanket folded in half on the seat cushion. In conclusion, VRE are capable of prolonged survival on fabric seat cushions and can be transferred to hands. Environmental surfaces such as chairs may serve as a potential reservoir for nosocomial transmission of VRE, and an easily cleanable, nonporous material is the preferred upholstery in hospitals.

Chicago↗
PubMed2000

Evaluation of the centrifuged and Gram-stained smear, urinalysis, and reagent strip testing to detect asymptomatic bacteriuria in obstetric patients.

OBJECTIVE: Our purpose was to compare the efficacy of the centrifuged and Gram-stained smear with the efficacy of both urinalysis and reagent strip testing for nitrites and leukocyte esterase in detecting asymptomatic bacteriuria in obstetric patients. STUDY DESIGN: A midstream urine specimen was evaluated in 528 patients either at the initial prenatal visit or at a visit because of possible preterm labor. Separate aliquots were tested by centrifugation (with a Cytospin Cytocentrifuge; Shandon, Inc, Pittsburgh, Pa) with Gram stain, by microscopic urinalysis for the presence of moderate to large numbers of bacteria or >10 leukocytes per high-power field, and by reagent strips for the presence of nitrites or leukocyte esterase activity. Results were compared with those of a quantitative urine culture obtained with blood and MacConkey agar plates. RESULTS: Thirty-six women (6.8%) had urine cultures showing 100,000 colony-forming units of a uropathogen per milliliter. The sensitivity and specificity of testing by centrifugation and Gram stain were 100% and 7.7%, respectively. Urinalysis and dipstick testing offered a sensitivity of 80.6% and 47.2%, respectively, with a specificity of 71.5% and 80.3%. No combination of tests, in series or in parallel, offered improved specificity over urinalysis alone. CONCLUSIONS: Centrifugation with Gram stain of a urine specimen offers excellent sensitivity but very poor specificity compared with microscopic urinalysis for the detection of asymptomatic bacteriuria and is not an acceptable screening test in an obstetric population. The false-negative rates of urinalysis (19.4%) and reagent strip testing (52.8%) preclude these from being excellent screening tests for asymptomatic bacteriuria. Given the potential sequelae of undiagnosed asymptomatic bacteriuria in an obstetric population, we conclude that urine cultures should be used for all pregnant patients to detect asymptomatic bacteriuria.

Adolescent↗