Search PubMed⌕ Search

Biomedical subjects

R L Nichols

Publications and source records attributed to R L Nichols.

At least 19 recordsLinked to original sources
PubMed2001

Response of Acala cotton to nitrogen rates in the San Joaquin Valley of California.

The responses of Acala cotton (Gossypium hirsutum L.) in California to a range of applied nitrogen (N) treatments were investigated in a 5-year, multisite experiment. The experiment's goals were to identify crop growth and yield responses to applied N and provide information to better assess the utility of soil residual N estimates in improving fertilizer management. Baseline fertilizer application rates for the lowest applied N treatments were based on residual soil nitrate-N (NO3-N) levels determined on soil samples from the upper 0.6 m of the soil collected prior to spring N fertilization and within 1 week postplanting each year. Results have shown positive cotton lint yield responses to increases in applied N across the 56 to 224 kg N/ha range in only 41% (16 out of 39) of test sites. Soil NO3-N monitoring to a depth of 2.4 m in the spring (after planting) and fall (postharvest) indicate most changes in soil NO3- occur within the upper 1.2 m of soil. However, some sites (those most prone to leaching losses of soluble nutrients) also exhibited net increases in soil NO3-N in the 1.2- to 2.4-m depth zone when comparing planting time vs. postharvest data. The lack of yield responses and soil NO3-N accumulations at some sites indicate that more efforts should be put into identifying the amount of plant N requirements that can be met from residual soil N, rather than solely from fertilizer N applications.

California↗
PubMed2001

Clinical presentations of soft-tissue infections and surgical site infections.

Skin and soft-tissue infections that usually follow minor traumatic events or surgical procedures are caused by a wide spectrum of bacteria. Less frequently, the infections occur spontaneously, which often is clinically confusing and leads to delays in diagnosis. Most of the infections are self-limited and easily treated with local measures and/or antibiotics. Others are life-threatening, requiring prompt diagnosis and aggressive surgical debridement in addition to the wise choice of antibiotic agents to limit tissue loss and preserve life. Many survivors experience critical tissue losses that may require changes in lifestyle as well as major reconstructive cosmetic surgery. Involvement of antibiotic-resistant gram-positive microorganisms in these infections only increases the difficulty of their treatment and may have a significant influence on the ultimate outcome.

Anti-Bacterial Agents↗
PubMed2001

Cell wall biosynthesis: glycan containing oligomers in developing cotton fibers, cotton fabric, wood and paper.

A series of oligomeric glycans can be extracted from the cell walls of developing cotton fibers with weak acid. Glycans that produce similar profiles on high pH anion chromatography with pulsed amperometric detection (HPAEC-PAD) are also found in a protein complex extracted from developing fibers and in amorphous aggregates found in association with immature fibers in developing, but not in mature cotton bolls. The quantity and composition of the glycans recovered from the carbohydrate-protein complex varies significantly with the time of day when the bolls are harvested. This diurnal variation is consistent with the hypothesis that secondary cell walls are deposited primarily at night. Incubation of re-hydrated cotton fibers in the presence of exogenous oligosaccharides, myo-inositol and glycerol substantially alters the apparent quantity of the oligomers extracted from the fibers. The same and similar glycans have also been extracted from cotton fabric, marine algae, various paper products and wood. While many of the oligomers isolated from the various cellulose sources display the same peaks by HPAEC-PAD, the specific number of oligomers and their relative quantities appear unique for each source of cellulosic material. Oligomeric glycans, as described in the preceding, are present in all cellulose sources that have been investigated. Their relative abundance changes in response to source, stage of development and other physiological variables. We hypothesize that the glycans are intermediates in the biological assembly of cellulose, and that their incorporation in cellulose is mediated by physicochemical and enzymatic mechanisms.

Cell Wall↗
PubMed2000

The role of quinolones in abdominal surgery.

The quinolone antibiotics have been a major advance for the treatment of various types of infections. These agents have generally good safety profiles, broad-spectrum activity, and favorable pharmacokinetics. In addition, several of these antibiotics are available in both intravenous and oral formulations, which allows for sequential therapy resulting in potential cost savings. However, patients can develop serious central nervous system side effects (seizures) and phototoxicity. In addition, the bioavailability of agents in this class can be reduced by coadministration with cations, such as magnesium, aluminum, calcium, and iron, which may make bioavailability unpredictable in patients. Although older quinolones such as ciprofloxacin were effective as prophylactic agents for biliary procedures and colorectal surgery and for the treatment of intra-abdominal infections, the use of these older quinolones was limited by the development of resistant organisms. In addition, because these agents had poor activity against anaerobes such as Bacteroides fragilis, the agents had to be combined with an antianaerobic agent, such as metronidazole, when anaerobic coverage was required. Recently, a new quinolone, trovafloxacin, has become available. Trovafloxacin has demonstrated increased activity against anaerobes in animal and human studies. However, the clinical profile of trovafloxacin for abdominal infections has not been fully demonstrated, and there is some concern that its activity against aerobic gram-negative bacilli, especially Pseudomonas aeruginosa, may not equal that of ciprofloxacin. Moreover, the safety profile of trovafloxacin is disadvantageous owing to reports of severe hepatic toxicity.

4-Quinolones↗
PubMed1999

Management of bacterial complications in critically ill patients: surgical wound and catheter-related infections.

The occurrence of surgical wound infections and/or bacteremia associated with central venous catheter use are of growing concern to all physicians who treat critically ill patients. The physician must be aware that some patients have an even greater risk for infection, such as those with multiple risk factors, those who are on central lines, or those patients who undergo multiple invasive diagnostic or therapeutic procedures. The emergence of resistant pathogens, particularly Gram-positive pathogens, is an important factor in the morbidity and mortality of hospitalized patients. In the face of this growing resistance among target organisms, the selection of the correct antimicrobial and nonpharmacologic interventions, based on correct identification and susceptibility test data, has become increasingly challenging. Methicillin-resistant Staphylococcus aureus and, more recently, glycopeptide-resistant enterococci and staphylococci represent a significant danger to the patient. As a consequence, earlier and more precise identification of the pathogens most frequently associated with infection is essential. The role of exacting surgical technique, infection control measures, and the appropriate use of prophylactic and therapeutic antibiotics cannot be overestimated in helping to reduce potential morbidity and mortality associated with severe surgical infection. The development of new antibiotics may help treat the difficult cases attributable to resistant Gram-positive bacteria.

Bacteremia↗
PubMed1999

Treatment of hospitalized patients with complicated gram-positive skin and skin structure infections: two randomized, multicentre studies of quinupristin/dalfopristin versus cefazolin, oxacillin or vancomycin. Synercid Skin and Skin Structure Infection Group.

Quinupristin/dalfopristin (Synercid), the first injectable streptogramin antibiotic available for the treatment of complicated gram-positive skin and skin structure infections, was compared with standard comparators (cefazolin, oxacillin or vancomycin) in one USA and one international trial. These two randomized, open-label trials of virtually identical design enrolled a total of 893 patients (450 quinupristin/dalfopristin, 443 comparator). The majority of patients had erysipelas, traumatic wound infection or clean surgical wound infection. Staphylococcus aureus was the most frequently isolated pathogen in both treatment groups and polymicrobial infection was more common in the quinupristin/dalfopristin group than in the comparator group. The clinical success rate (cure plus improvement) in the clinically evaluable population was equivalent between the two treatment groups (68.2% quinupristin/dalfopristin, 70.7% comparator; 95% CI, -10.1, 5.1) despite a shorter mean duration of treatment for quinupristin/dalfopristin patients. In the bacteriologically evaluable population, by-patient and by-pathogen bacteriological eradication rates were somewhat lower for quinupristin/dalfopristin (65.8% and 66.6%, respectively) than for the comparator regimens (72.7% and 77.7%, respectively). The lower bacteriological response rates in the quinupristin/dalfopristin group were, in part, due to a higher rate of polymicrobial infections and a higher incidence of patients classified as clinical failure, a category which included premature discontinuation of treatment because of local venous adverse events. The bacteriological eradication rate for quinupristin/dalfopristin was higher in monomicrobial infections than in polymicrobial infections (72.6% versus 63.3%, respectively), whereas the corresponding rate for the comparator regimens was lower for monomicrobial infections than polymicrobial infections (70.8% versus 83.1%). This finding was not unexpected, since the spectrum of quinupristin/dalfopristin is focused on gram-positive pathogens and additional antibiotics to treat gram-negative bacteria were not required per protocol. The systemic tolerability of both treatment regimens was qualitatively similar. A higher rate of drug-related venous adverse events was reported for quinupristin/dalfopristin (66.2%) than for the comparator regimen (28.4%). Premature discontinuation of study drug was primarily due to adverse clinical events for quinupristin/dalfopristin (19.1%), whereas the most common reason for discontinuation among those receiving the comparator regimens was treatment failure (11.5%). Quinupristin/dalfopristin is an effective alternative for the treatment of hospitalized patients with complicated skin and skin structure infections due to quinupristin/ dalfopristin-susceptible gram-positive organisms, including methicillin- and erythromycin-resistant S. aureus.

Adolescent↗
PubMed1999

Optimal treatment of complicated skin and skin structure infections.

Gram-positive bacteria (e.g. Staphylococcus aureus and Streptococcus pyogenes) are the main cause of skin and skin structure infections (SSSI). Treatment presents a clinical challenge to the physician, particularly with the increase in multidrug-resistant strains and widespread cross-resistance to antibiotic treatment. Initial treatment of SSSI involves the use of fluoroquinolones or penicillinase-resistant penicillins. If infection is caused by methicillin-resistant staphylococci, therapy with glycopeptides is warranted. However, in the last few years several cases of infection caused by strains of S. aureus with reduced susceptibility to glycopeptides have been reported. Quinupristin/dalfopristin is a new streptogramin that has shown efficacy in the management of multidrug-resistant gram-positive infections. Two major studies suggest that in the treatment of complicated SSSI, the clinical efficacy of quinupristin/dalfopristin is equivalent to that of vancomycin and/or oxacillin and vancomycin and/or cefazolin.

Anti-Bacterial Agents↗
PubMed1998

Postoperative infections in the age of drug-resistant gram-positive bacteria.

Postoperative infection is a significant cause of surgical morbidity and mortality. The risk of infection after surgery depends on a number of factors, including the type and length of the surgical procedure; the age, underlying conditions, and previous history of the patient; the skill of the surgeon; the diligence with which infection control procedures are applied; and the type and timing of preoperative antibiotic prophylaxis. Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci, now implicated in many postoperative infections, have been joined most recently by strains of S. aureus that show intermediate levels of resistance to vancomycin. Postoperative infections caused by drug-resistant pathogens are more difficult to treat and are associated with a higher morbidity and mortality. New antibiotics that are effective against drug-resistant pathogens are urgently needed, as is renewed dedication to the prevention of postoperative infection and to the use of the principles of infection control.

Antibiotic Prophylaxis↗
PubMed1998

Evaluation of the protective value of hospital gowns against blood strike-through and methicillin-resistant Staphylococcus aureus penetration.

BACKGROUND: Hospital gowns protect patients and health care workers from exposure to blood and other infectious materials. Previous studies have shown that certain gowns do allow blood strike-through. Because of worldwide increases in the incidence of Staphylococcus aureus infections, especially with methicillin-resistant strains, there is now increased concern regarding bacterial transmission through gowns. METHODS: This study evaluated six gown types used in hospitals (one disposable cover or isolation gown, three disposable operating room gowns, and new and washed reusable operating room gowns). Gowns were evaluated for dry spore and S. aureus filtration efficiencies and were subjected to 20 time-pressure combinations with methicillin-resistant S. aureus-spiked blood (10(4)/ml) to evaluate blood strike-through and passage of methicillin-resistant S. aureus. RESULTS: Blood strike-through was lowest with disposable operating room gowns 1 and 2 (polypropylene). Disposable operating room gown 3 (polyester-wood pulp) showed the greatest strike-through and overall passage of methicillin-resistant S. aureus. Operating room gowns 1 and 2 showed minimal bacterial passage, whereas the disposable cover (polypropylene) only allowed passage at pressures greater than 1 psi. Bacterial filtration efficiency testing showed operating room gowns 1 and 2 to be the most protective; operating room gown 3 and both reusable (cotton) gowns were the least protective. Dry spore passage was greatest for reusable gowns. CONCLUSION: Different hospital gowns offer varying degrees of protection against fluid strike-through or bacterial passage. Gowns therefore should be chosen according to the task performed and conditions encountered.

Analysis of Variance↗
PubMed1997

Current practices of preoperative bowel preparation among North American colorectal surgeons.

In North America, the rate of infections following colorectal surgery decreased after the introduction of oral antibiotic bowel preparation against colonic microflora. Eight hundred eight board-certified colorectal surgeons were surveyed for their current bowel preparation practices before elective procedures. The 471 responders (58%) all use mechanical preparation: oral polyethylene glycol solution (70.9% of the respondents), oral sodium phosphate solution with or without bisacodyl (28.4%), and "traditional" methods of dietary restriction, cathartics, and enemas (28.4%). Most surgeons (86.5%) add oral and parenteral antibiotics to the regimen; 11.5% add only parenteral antibiotics, 1.1% add only oral antibiotics, and 0.9% add no antibiotics. Generally (77.8% of cases), oral neomycin and erythromycin or metronidazole are combined with a perioperative parenteral antibiotic. Most individuals start the preparation as outpatients the day before surgery, and the parenteral drugs are added to the regimen 1-2 hours before the procedure. The use of outpatient bowel preparation is increasing; however, patient selection is critical, and education is needed to reduce the rate of complications.

Anti-Bacterial Agents↗
PubMed1997

Multicenter, randomized study comparing levofloxacin and ciprofloxacin for uncomplicated skin and skin structure infections.

BACKGROUND: The fluoroquinolone, levofloxacin, is active against most common pathogens in skin and skin structure infections. METHODS: The efficacy, tolerability, and safety of levofloxacin and ciprofloxacin were compared in a randomized, open-label, multicenter trial of patients with uncomplicated skin and skin structure infections. Of 469 patients treated, 231 received levofloxacin (500 mg qd) and 238 were given ciprofloxacin (500 mg bid). RESULTS: Overall clinical success rates (cured plus improved) for levofloxacin and ciprofloxacin were 98% and 94%, respectively (95% confidence interval [CI], -7.7, 0.7). Overall microbiologic eradication rates by patient were 98% in the levofloxacin group and 89% in the ciprofloxacin group (95% CI, -14.5, -2.7), whereas eradication rates by pathogen were 98% and 90%, respectively (95% CI, -12.6, -3.7). The eradication rate for Staphylococcus aureus was 100% in the levofloxacin group and 87% in the ciprofloxacin group (95% CI, -20.2, -5.1). Treatment-emergent adverse events were comparable, with drug-related adverse events reported in 6% of levofloxacin patients and 5% of ciprofloxacin patients. CONCLUSIONS: Levofloxacin is as effective and safe as ciprofloxacin in the treatment of uncomplicated skin and skin structure infections.

Administration, Oral↗
PubMed1996

Surgical infections: prevention and treatment--1965 to 1995.

During the 30 year period from 1965-1995, significant advances have been made in the prevention, diagnosis, and management of surgical infections. To a great degree these advances have been provided by surgeons who developed a primary interest in this area. The Surgical Infection Society (SIS) was established in 1980 for surgeons and other physicians and scientists in order to better coordinate efforts in education and research concerning the infected surgical patient. The most significant of these advances were initially the accurate microbiologic definition of the human endogenous microflora in health and disease. Improvements in the techniques utilized to isolate and identity anaerobic microorganisms were of paramount importance. These lead to improvements in the choice of antibiotic agents for prophylaxis and treatment which resulted in improved clinical results. Most recently, emphasis has been placed on the perioperative identification of the high-risk patient who is more likely to develop infection in the postoperative period. By separating high-risk from low-risk patients in each operative procedure, rather than assuming their risk based on the traditional classification of surgical procedure, a more rationale plan of prospective alterations of treatment can be offered.

Antibiotic Prophylaxis↗
PubMed1995

Determination of surgeon-generated gown pressures during various surgical procedures in the operating room.

BACKGROUND: Patients' blood or other potentially infectious body fluids frequently pass through surgeons' gowns in the operating room. These fluids are absorbed by the scrub suit and can directly contaminate the surgeons' skin. Protective barriers remain an important method of exposure control for many blood-borne pathogens. The efficacy of surgical gowns in preventing this passage or strikethrough has therefore become the focus of much attention. Limited data are available concerning the magnitude and duration of pressure against surgeons' gowns. METHODS: A 32-sensor mat placed in the abdominal area was used to obtain pressure data for 15 surgeons of both sexes performing 20 procedures. RESULTS: The percentage of time any pressure was detected varied from 0% during knee reconstruction to 97.4% for excision of a stomach mass. In 16 procedures, more than 87.8% of pressure contacts were 2 N/cm2 (2.9 psi or less); in addition, more than 80% of the contacts were 15 seconds or less during 13 of the procedures. No correlation was found between the amount of pressure and sex of the surgeon, surgical service, or length of the procedure. CONCLUSIONS: Because pressure is related to the type of procedure, gowns should be chosen to afford protection against fluid strikethrough for the pressures and blood loss anticipated.

Blood-Borne Pathogens↗