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Biomedical subjects

R H Parker

Publications and source records attributed to R H Parker.

At least 19 recordsLinked to original sources
PubMed1987

Beta-lactamase inhibitors: another approach to overcoming antimicrobial resistance.

Beta-lactamase inhibitors in combination with a beta-lactam antimicrobial agent provide another approach to the treatment of infections caused by many bacteria resistant to commonly used agents. Currently two fixed combinations are commercially available. One is the oral preparation of amoxicillin and potassium clavulanate (Augmentin). The other is for intravenous therapy and combines ticarcillin and potassium clavulanate (Timentin). In vitro studies confirm that the combination of a beta-lactamase inhibitor and a beta-lactam can increase the activity of the beta-lactam to such important pathogens as S aureus, Klebsiella, H influenzae, Bacteroides spp and other bacteria which produce plasmid-mediated beta-lactamase. Clinical efficacy studies have demonstrated potential usefulness of these combinations particularly for therapy of suspected or proven infections caused by mixed aerobic and anaerobic bacteria. The combination of amoxicillin or ticarcillin with clavulanic acid can be used to improve cost-effectiveness of antimicrobial therapy if they replace regimens that use multiple drugs or drugs with a relatively high incidence of adverse reactions.

Amoxicillin↗
PubMed1986

Review of imipenem.

Imipenem, a new carbapenem beta-lactam broad-spectrum antibiotic, is highly active in vitro against most aerobic and anaerobic gram-positive and gram-negative bacteria isolated from infectious diseases of human beings. Except for enterococci and methicillin-resistant staphylococci most gram-positive cocci are inhibited by less than 2 micrograms/ml. Although the MIC-90 of methicillin-resistant staphylococci may be less than 4 micrograms/ml, these bacteria are usually resistant to imipenem by modified testing methods. The enterococcus, S. faecalis, has an MIC-90 of less than 8 micrograms/ml but bactericidal concentration may be much higher. Most Enterobacteriaceae are highly susceptible to imipenem with MIC-90 of 0.5 to 2.0 micrograms/ml. Proteus species are less susceptible with MICs of 4 to 8 micrograms/ml. Isolates of P. aeruginosa have variable susceptibility with MICs ranging from 0.25 to 16 micrograms/ml. Pseudomonas maltophilia and P. cepacia are usually resistant to imipenem. Except for Clostridium species, most strict anaerobes are susceptible to less than 1.0 micrograms/ml of imipenem. When combined with cilastatin (1:1 ratio), the renal elimination of the active form is increased. The serum halflife in normal renal function is about 1 hour and increases to 3.4 hours in anuria. Major adverse effects are similar to those of cephalosporins except for seizures in some patients. Colonization with fungi and drug-resistant bacteria occurs in about 5% of imipenem-treated patients. Clinical studies have demonstrated efficacy in 79% to 96% of patients treated.

Anti-Bacterial Agents↗
PubMed1986

Spontaneous pneumothorax with Pneumocystis carinii infection. Occurrence in patients with acquired immunodeficiency syndrome.

Two patients with acquired immunodeficiency syndrome developed spontaneous pneumothorax during the course of Pneumocystis carinii pneumonia. The pneumothorax in each of these patients was a primary event, unrelated to biopsy or mechanical ventilation. To our knowledge, this complication of P carinii infection has not been noted in adults before and is an important consideration for those caring for persons with this illness.

Acquired Immunodeficiency Syndrome↗
PubMed1985

The effects of mild one-legged isometric or dynamic training.

Four men isometrically trained their stronger leg for 19 weeks (attempted knee extension against a restraining strap incrementally increasing to 30 brief maximal contractions X 6 wk-1). Five others similarly trained dynamically (repeated knee extension against a 63 N resistance force, incrementally increasing to 300 extensions X 6 wk-1). Before, at regular intervals during training and after de-training (between 7-11 weeks) measurements were made using trained and control legs of: Maximum Voluntary Isometric Contraction (M.V.C.), Endurance at 60% M.V.C., Knee Extension Performance Test (K.E.P.T.) and One-legged Work Test. Isometric training produced a 30% (p less than 0.01) increase in M.V.C. with a 15% (p less than 0.05) increase in the control leg. These changes persisted with some deterioration after the de-training period. Endurance at 60% M.V.C. remained unchanged, even though M.V.C. was increasing in both trained and control legs. There was some evidence that isometric training improved the cardio-vascular response to one-legged exercise. Dynamic training did not result in changes in M.V.C., Endurance at 60% M.V.C. or the One-legged work Test, but K.E.P.T. (time taken for 50 knee extensions at a comfortable pace against 63 N resistance) improved by 33% (p less than 0.01) and 28% (p less than 0.01) in the trained and control legs respectively. Isometric training resulted in similar improvements in performance of K.E.P.T. (28%, p less than 0.05, trained leg; 18%, p less than 0.05 control leg). For similar time spent in training, isometric work appeared more effective than dynamic work in improving the parameters of muscle function, these improvements appeared to be both centrally (C.N.S.) and locally mediated.

Adult↗
PubMed1985

Physiological adaptations and activity recorded at a polar base.

Physiological parameters and activity were recorded monthly on 19 men wintering at a polar base. A comparison was made between those in their first Antarctic winter (Group A, n = 13) and those in their second consecutive Antarctic winter (Group B, n = 6). Group A were more active (p less than 0.001) and spent more time outside (p less than 0.001) during the summer months than during the darker and colder winter period. Combined data showed no correlation between total activity and meteorological conditions, but a clear (p less than 0.001) negative correlation with time spent outside and wind speed. In the first part of the year group A became fitter (as shown by a lower heart rate at a VO2 1.51 min-1), increased basal oxygen uptake under standard conditions and put on body and fat mass. These changes were not demonstrated in group B living and working under identical conditions. Lean body mass of both groups rose throughout the year (A, p less than 0.001; B, p less than 0.05). These data suggested that the changes in physiological parameters in group A were in response to the life style and activity of a polar base, rather than to the Antarctic climate per se.

Adaptation, Physiological↗
PubMed1984

An outbreak of Candida parapsilosis bloodstream infections in patients receiving parenteral nutrition.

From July to September 1981, five patients at one hospital had bloodstream infections or colonization of an intravascular cannula with Candida parapsilosis. All five cases, but none of 34 controls, were receiving parenteral nutrition at the onset of infection or colonization (P less than 0.01; Fisher's exact test, one-tailed). Epidemiologic investigation showed that human serum albumin was more frequently added to parenteral nutrition solutions during the epidemic period than during a comparable period a year earlier. The increase in human serum albumin use coincided with the more frequent use of an electrically powered vacuum pump to assist in compounding parenteral nutrition solutions. Cultures from the vacuum pump showed heavy growth of C parapsilosis from multiple sites. Laboratory investigation demonstrated that sterile solutions could be contaminated by use of the vacuum pump. Use of the vacuum pump was stopped, and no further cases occurred.

Candidiasis↗
PubMed1984

Safety of cefotaxime and other new beta-lactam antibiotics.

beta-Lactam antimicrobial agents have until recently enjoyed a reputation of reliability and safety. Now serious problems have emerged associated with use of some of the newer drugs of this class. Latamoxef (moxalactam) and cefoperazone, both of which have a methyltetrazolethiol side chain, have been reported to cause coagulation abnormalities, clinical bleeding, and disulfiram-like reactions. In addition, an unusually high incidence of diarrhoea has been associated with administration of cefoperazone. Cefotaxime does not have the [methylthiotetrazole] side chain and has not caused bleeding, coagulopathy, or disulfiram-like reactions. Diarrhoea, usually mild, has been observed in only 1% of patients given cefotaxime in clinical trials. The remarkable safety record of cefotaxime is an important consideration for clinicians in the selection of an antimicrobial agent for seriously ill patients.

Anti-Bacterial Agents↗
PubMed1984

Effect of frequency of administration on therapeutic efficacy of cefotaxime.

Clinical trials with cefotaxime have demonstrated that this antibiotic is effective and safe in a wide range of dosage schedules. Because of uncertainty about the most appropriate dosage regimen, physicians may be inclined to prescribe cefotaxime in higher doses and greater frequencies of administration than are required or economical (eg, dosing every six hours for an infection caused by a highly susceptible microorganism). To demonstrate that cefotaxime offers the physician great flexibility in dosing to achieve successful treatment with optimal cost-effectiveness, efficacy data from comparative and noncomparative studies in the United States were analyzed. Cases reviewed were those in which both the initial and final dosage regimens corresponded to one of several predetermined dosing schedules. These schedules included doses of 0.5 to 2.0 gm administered from two to six times a day. Patients were categorized according to severity of infection, and clinical and bacteriological responses were summarized according to frequency of administration. The analysis yielded 2,096 clinically evaluable cases and 1,755 bacteriologically evaluable cases. Uniformly good clinical and bacteriological success rates were achieved in all dosage regimens, indicating that in many circumstances the most appropriate regimen is every eight hours or, for highly susceptible pathogens, every 12 hours. Giving cefotaxime every six hours or more often is justified only when high concentrations of antibiotic are needed at the site of infection. Prescribing cefotaxime in the most appropriate dosage regimen will have a significant impact on the cost-effectiveness of antimicrobial therapy.

Bacterial Infections↗
PubMed1983

Hemophilus influenzae respiratory infection in adults. 2. Treatment guidelines.

Once a Hemophilus influenzae isolate is identified as the cause of a respiratory tract infection in an adult, it should be tested for beta-lactamase production, ie, for ampicillin resistance. The incidence of ampicillin-resistant strains of H influenzae is increasing. The Centers for Disease Control in Atlanta estimates an average incidence nationwide of 18% to 22%; the rate varies considerably from community to community. Thus, practitioners should be aware of the ampicillin-resistance rate in their community and should keep this rate in mind especially when treating patients empirically. Patients with H influenzae infections who are acutely ill, who fail to respond to ampicillin, or who are known to have an ampicillin-resistant infection on the basis of laboratory findings should receive therapy designed to combat ampicillin-resistant strains.

Adult↗
PubMed1982

Staphylococcal bacteremia in cancer patients: intravenous and oral antimicrobial therapy.

Eighteen adult cancer patients with 21 episodes of staphylococcal bacteremia were treated with sequential intravenous and oral antimicrobial agents. Adequacy of antimicrobial therapy was monitored with serum antibacterial activity studies. The mean duration of intravenous and oral therapy was nine and 25 days, respectively. Clinical and bacteriologic cures were achieved in all cases except one, in which relapse occurred after only 16 days of therapy. One patient had staphylococcal endocarditis and one had staphylococcal pneumonia. Four patients died of causes unrelated to staphylococcal bacteremia after 12, 21, 27, and 40 days of therapy, respectively. Initial intravenous therapy followed by oral antimicrobial agents to complete treatment, monitored with serum antibacterial activity studies, is effective therapy for patients with cancer and staphylococcal bacteremia.

Administration, Oral↗
PubMed1980

Intravenous followed by oral antimicrobial therapy for staphylococcal endocarditis.

We have treated 35 cases of staphylococcal endocarditis in 33 patients with intravenous followed by oral antimicrobial therapy. All patients had three or more blood cultures positive for Staphylococcus aureus, and all had cardiac murmurs characteristic of valvular insufficiency. The mean total duration of antimicrobial therapy was 42.4 d, consisting of a mean of 16.4 d of intravenous therapy followed by a mean of 26 d of oral therapy. Intravenous antimicrobial therapy included sodium nafcillin (32 cases; mean dose 9.2 g daily) and clindamycin (three cases). Oral therapy included dicloxacillin or oxacillin (30 cases; mean dose 4.5 g daily), clindamycin (four cases), and potassium penicillin V (one case). Serum bactericidal titers using the blood culture isolates showed similar activity with both intravenous and oral drugs. All patients treated with this sequential intravenous and oral regimen were cured. A regimen of initial intravenous followed by oral antimicrobial therapy, monitored with serum antibacterial activity studies, is a safe, effective, well-tolerated, and economical treatment for staphylococcal endocarditis.

Administration, Oral↗
PubMed1979

Counterimmunoelectrophoresis for rapid identification of blood-culture isolates.

A total of 303 blood cultures that were positive by examination of Gram-stained smears were tested immediately by counterimmunoelectrophoresis for detection of bacterial antigens. Antigen was detected in all 82 blood cultures containing Streptococcus pneumoniae and 11 of 22 with Klebsiella pneumoniae, two of two with Haemophilus influenzae, and one of one with Neisseria meningiditis. False-positive cross-reactions in 265 tests occurred only with pneumococcal Omniserum in two cases of nongroupable streptococcal bacteremia and with Klebsiella antiserum in one case of Escherichia coli bacteremia (1.1%). A specific identification of the microorganisms at least 24 hours earlier than by subculture technics was accomplished in 91% of the cultures containing the aforementioned bacteria. The procedure was not useful for detecting antigen in blood cultures containing Staphylococcus aureus.

Antigens, Bacterial↗
PubMed1979

Viral pericarditis in patients receiving hemodialysis.

Four patients with end-stage renal disease in whom pericarditis developed while they received intermittent hemodialysis therapy were evaluated for viral infection. We found high or rising serum antibody titers to influenza virus A (three patients) and coxsackievirus B (one patient). Cardiac tamponade occurred in three patients, requiring pericardiectomy in two; each patient eventually recovered. Viral pericarditis may be an important cause of "uremic" pericarditis in chronically dialyzed patients.

Acute Disease↗