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Biomedical subjects

V L Yu

Publications and source records attributed to V L Yu.

At least 55 records · Page 3Linked to original sources
PubMed1998

Disinfection of water distribution systems for Legionella.

Hospital-acquired legionnaires' disease arises from the presence of Legionella in hospital water systems. Legionella not only persists in hot water tanks but is also found in the biofilm throughout the entire water distribution system. Conditions within water systems that promote Legionella colonization include water temperature, configuration and age of the hot water tank, physicochemical constituents of the water, plumbing materials, and commensal microflora. Hospital-acquired legionnaires' disease has been prevented by instituting control measures directed at the water distribution system. These include superheat-and-flush, copper/silver ionization, ultraviolet light, instantaneous heating systems, and hyperchlorination. Each of the above disinfection methods has been proven to be effective in the short-term, but long-term efficacy has been difficult due to limitations associated with each method. The complexities of Legionella disinfection, including advantages and disadvantages of each method, are reviewed. A successful Legionella prevention program requires cooperation and communication among hospital administrative personnel, engineers, and infection control staff. Routine environmental surveillance cultures for Legionella are the critical component for successful long-term disinfection. Culture results document the efficacy of the disinfection method and alert the hospital staff to consider Legionella in hospitalized patients with pneumonia.

Cross Infection↗
PubMed1998

MYCIN II: design and implementation of a therapy reference with complex content-based indexing.

We describe the construction of MYCIN II, a prototype system that provides for content-based markup and search of a forthcoming clinical therapeutics textbook, Antimicrobial Therapy and Vaccines. Existing commercial search technology for digital references utilizes generic tools such as textword-based searches with geographical or statistical refinements. We suggest that the drawbacks of such systems significantly restrict their use in everyday clinical practice. This is in spite of the fact that there is a great need for the information contained within these same references. The system we describe is intended to supplement keyword searching so that certain important questions can be asked easily and can be answered reliably (in terms of precision and recall). Our method attacks this problem in a restricted domain of knowledge-clinical infectious disease. For example, we would like to be able to answer the class of questions exemplified by the following query: "What antimicrobial agents can be used to treat endocarditis caused by Eikenella corrodens?" We have compiled and analyzed a list of such questions to develop a concept-based markup scheme. This scheme was then applied within an HTML markup to electronically "highlight" passages from three textbook chapters. We constructed a functioning web-based search interface. Our system also provides semi-automated querying of PubMed using our concept markup and the user's actions as a guide.

Abstracting and Indexing↗
PubMed1997

Invasive aspergillosis in liver transplant recipients in the 1990s.

Invasive aspergillosis occurred in 26 liver transplant recipients since 1990 at five liver transplant centers. The median time to onset was 17 days after transplantation. Twenty-seven percent of the patients had undergone retransplantation. Invasive aspergillosis occurred significantly earlier after transplantation in smokers than in nonsmokers (P=0.017). Patients with late-onset aspergillosis (occurring after posttransplant day 90) were more likely to have had prior cytomegalovirus infection than those with early-onset aspergillosis (occurring within 90 days of transplantation) (67% vs. 10%, respectively, P=0.013). Only 8% of the patients had received additional corticosteroids or OKT3, which suggests that augmented immunosuppression may not be a relevant risk factor for invasive aspergillosis in the 1990s due to less frequent use of these agents. The median serum bilirubin level of the patients was 21.8 mg/dl, 85% of the patients had renal insufficiency, and 54% were on dialysis before the onset of invasive aspergillosis, which suggest that overall severity of illness, including poorly functioning hepatic allograft and renal failure may be the major determinants of disease occurrence. Overall mortality was 92% (24/26). No difference in mortality could be shown for the patients who received amphotericin B versus liposomal amphotericin B preparations (100% vs. 89%); however, the mean time to death after the initiation of therapy was 20 days in patients who received amphotericin B and 43 days in those who received liposomal amphotericin B preparations.

Adolescent↗
PubMed1997

Legionellosis.

Explore the source record for details and available documents.

Adult↗
PubMed1997

Human acetyltransferase polymorphisms.

Conjugation of primary amino and hydroxylamino groups with acetate, catalyzed by acetyl CoA-dependent arylamine acetyltransferase (NAT) enzymes, may play an important role in the intricate series of metabolic pathways that produce or prevent toxicity following exposure to homo- and heterocyclic arylamine and hydrazine xenobiotics. Two independently regulated and kinetically distinct human acetyltransferases are now known to exist, namely NAT1 and NAT2. Interindividual variation in NAT2 function is associated with the classical isoniazid acetylation polymorphism which was discovered over forty years ago. At last count, fifteen variant alleles at the NAT2 gene locus have been linked to the isoniazid 'acetylator phenotype', and each of these can be identified in population studies using specific PCR-based genotyping tests. On the other hand, NAT1 shows kinetic selectivity for compounds whose disposition is unrelated to the classical isoniazid acetylation polymorphism. NAT1 expression is also phenotypically variable in human populations, at least in part due to allelic differences at the NAT1 gene locus. Nine NAT1 variant alleles have been described to date, of which NAT1* 14 and NAT1* 15 clearly produce defective NAT1 proteins and lead to functional impairment in the metabolism of NAT1-selective substrates both in vivo and in vitro. On the other hand, it has been reported that the NAT1* 10 variant associates with elevated NAT1 activity and increased risk for cancers of the bladder and colon. Because of the important toxicologic consequences of allelic variation in NAT1 and NAT2 function for the metabolic activation of arylamine and heterocyclic amine procarcinogens, further studies are needed to improve our understanding of the extent of NAT allelic variation, to determine the functional capacity of each variant gene product, and to develop accurate methods of detecting them in population and epidemiological studies.

Acetylation↗
PubMed1997

Lack of serologic evidence for Helicobacter pylori infection in head and neck cancer.

BACKGROUND: Several epidemiologic investigations have established a link between Helicobacter pylori infection and gastric malignancies. Because the stomach is in continuity with the oral cavity and the bacterium has been isolated from dental plaque and saliva, we hypothesized that H. pylori infection of the upper aerodigestive tract might result in mucosal disruption, allowing for subsequent transformation by known carcinogens such as tobacco and alcohol. METHODS: To test this hypothesis, we assayed for the presence of IgG antibodies to H. pylori in the serum of 21 patients with squamous cell carcinoma of the head and neck (SCCHN) and 21 matched controls without a history of head and neck cancer. RESULTS: The incidence of seropositivity in the SCCHN patients was 57% and in the controls, 62% (p > 0.05). CONCLUSIONS: These data do not support an etiologic role for H. pylori infection in head and neck cancer.

Antibodies, Bacterial↗
PubMed1997

Cirrhotic fever in the 1990s: a prospective study with clinical implications.

Fifty consecutive patients with fever and cirrhosis were prospectively studied to assess if cirrhotic fever was a true clinical entity and to determine its characteristics and outcome. In 20% (10) of the 50 patients, an identifiable source of fever or infection, was not documented (these patients were defined as having cirrhotic fever). The patients with cirrhotic fever were significantly less toxic, as indicated by lower temperature (P = .0001), tachycardia (P = .0005), and tachypnea (P = .05), but had fever for a longer duration (P = .009) than did patients with infectious fever. Patients with cirrhotic fever were significantly less likely to have focal signs or symptoms (P < .0001) or a portal of infection confirmed by culture (P = .0001), as compared with patients with infectious fever. Outcome (at 30-days or long-term) was not different for patients with cirrhotic fever vs.-patients with infectious fever or matched controls who did not have fever. Eight (80%) of the 10 patients with cirrhotic fever underwent transplantation; fever did not recur after transplantation in any of these patients. Thus, fever in up to 20% of the febrile patients with cirrhosis may be attributable to cirrhosis itself; such patients may be spared the ongoing diagnostic maneuvers and unnecessary trials of antibiotics.

Adult↗
PubMed1997

Psychological stress and depression in older patients with intravenous drug use and human immunodeficiency virus infection: implications for intervention.

We aim to assess the age-related differences in psychological stress and depression in patients with human immunodeficiency virus (HIV) infection. Prospective, longitudinal, observational study of patients with HIV followed at a university affiliated VA Medical Center. Fifty-six consecutive patients with HIV infection aged 19-68 were studied. Data on demographics, living arrangements, education, employment, income, social, religious, and community support, medical status, psychological stress, depression, and coping was assessed at baseline and every 6 months. Instruments for psychological testing included Beck Depression Inventory, Profile Mood Status (POMS) scale and ways of coping scale (inventory of coping with illness scale). Sixty-nine per cent (38/56) of the patients were older than 35 years of age. Older patients exhibited significantly greater emotional and psychological stress; the mean POMS score for older patients was 56.8 as compared to 21.5 for younger patients (P = 0.004). Older patients had significantly greater depression (P = 0.001), higher tension and anxiety (P = 0.005), greater anger and hostility (P = 0.03), greater confusion and bewilderment (P = 0.01), and more fatigue (P = 0.003) as compared with younger patients. Older patients were significantly more likely to have intravenous drug use as an HIV risk factor (P = 0.02), less likely to be employed (P = 0.005), and more likely to use non-traditional therapies (P = 0). Intravenous drug use was an independent predictor of psychological stress in older patients. Patients with HIV, older than 35 years of age, are significantly more likely to suffer from depression and psychological stress; intravenous drug use was an independent predictor of stress. Interventions for the treatment of depression should be especially sought in this subgroup of patients with HIV.

Adult↗
PubMed1997

Macrolides are ideal for empiric therapy of community-acquired pneumonia in the immunocompetent host.

We propose that macrolides, especially the newer macrolides (azithromycin, clarithromycin, roxithromycin), are ideal agents for community-acquired pneumonia in the immunocompetent host who is not a resident of a nursing home or long-term care facility. Macrolides have proven effective in clinical trials against typical and atypical pathogens; thus, unlike beta-lactam agents, they can be given as monotherapy. Streptococcus pneumoniae isolates exhibiting high-level resistance to penicillin and cephalosporins pose a problem not only for the macrolides, but also for quinolones, tetracyclines, and most other beta-lactam agents. The tetracycines, quinolones, and beta-lactam agents have broader spectrum activity against aerobic gram-negative bacilli, which are uncommon pathogens of community-acquired pneumonia in the immunocompetent host. This broader spectrum is not only superfluous, but the potential of emergence of resistant bacteria is enhanced unnecessarily. Serious adverse reactions to the macrolides are rare. The newer macrolides have improved bioavailability and improved pharmacokinetics such that once- or twice-daily dosing regimens can be used. Finally, a comparison of the costs of macrolides to quinolones and beta-lactam agents (especially cephalosporins) show that the oral macrolides are among the least expensive antibiotics that can be prescribed for pneumonia. Thus, macrolides seem to be the ideal empiric antibiotic for community-acquired pneumonia based on spectrum of activity, safety, and cost.

Anti-Bacterial Agents↗
PubMed1996

Pulmonary infections in liver transplant recipients receiving tacrolimus. Changing pattern of microbial etiologies.

Pulmonary infections are a significant cause of morbidity after liver transplantation; Gram-negative bacilli, cytomegalovirus, and Pneumocystis carinii were the usual pulmonary pathogens in the earlier studies in liver transplant recipients receiving cyclosporine. We prospectively assessed the impact of pulmonary infection in 101 consecutive liver transplant recipients receiving the new immunosuppressive agent tacrolimus (FK506). Fifteen percent (15/101) of the patients had 19 episodes of pneumonia; 58% (11/19) of the pneumonias were bacterial, 37% (7/19) were fungal, and 5% (1/19) were protozoal (Toxoplasma gondii). Twenty-seven percent of the bacterial pneumonias were due to Legionella. None of the patients had cytomegalovirus or P carinii pneumonia. Seven percent (7/10) of the study patients had fungal pneumonitis; 4% had invasive aspergillosis and 3% had cryptococcosis. Mortality was significantly higher (53%, 8/15) for patients with pneumonia than for patients without pneumonia (10%, 9/86, P = 0.0004). Only fungal pneumonias were the direct cause of death; 63% (5/8) of the deaths were in patients with fungal pneumonitis. Our data suggest a changing pattern of microbial etiologies of pneumonitis in the era of modern immunosuppressive agents. We show that P carinii pneumonia and cytomegalovirus can be effectively curtailed with appropriate prophylaxis. Fungal infections, on the contrary, not only constituted a major proportion of the pneumonia, but also carried the highest pneumonia-associated mortality. Legionella infections can be overlooked unless specialized laboratory methodology (cultured on selective media, urinary antigen) are applied routinely on all cases of pneumonia. We recommend routine culture on the water supply for Legionella in all transplant centers.

Adult↗
PubMed1996

A high incidence of native portal vein thrombosis in veterans undergoing liver transplantation.

The incidence of native portal vein thrombosis (PVT) in liver transplant recipients has been reported to range from 2.1 to 13.8%. We have identified an inordinately high incidence of PVT in a consecutive series of U.S. veterans receiving liver transplants. Between October 1989 and February 1994, 88 consecutive U.S. veterans received 99 orthotopic liver transplants under primary Tacrolimus (Prograf, formerly FK506) based immunosuppression. A number of clinical features were examined in an effort to identify risk factors for PVT and outcome was compared to patients without PVT. Native PVT was present in 23/88 (26%) patients. All of these patients were male U.S. veterans with a mean age of 47 years. When compared to the 65 patients without PVT, we found no significant difference with respect to underlying liver disease, age, Childs-Pugh score (mean = 12), UNOS status as defined prior to April 1995 (95% UNOS 3 or 4), previous abdominal surgery, or liver volume. Median blood loss for patients with PVT (21 units of packed red blood cells) was greater than for those without PVT (14 units, P = 0.04). Portal thrombectomy was performed in 11 patients, 11 patients required mesoportal jump grafts, and 1 patient had an interposition graft. Standard veno-venous bypass was used in 10 patients with single bypass utilized for the remainder. Actuarial patient survival for all patients at 1, 2, and 4 years was 88, 85, and 79%, respectively. There was no significant difference in patients with or without PVT. Patients with PVT had poorer graft survival than patients without PVT (86% vs 65%, 1 year; 81% vs 65%, 2 years; 81% vs 61%, 4 years; P = 0.03); however, this was not related to technical problems with the portal venous inflow. PVT occurred in 26% of U.S. veterans undergoing liver transplantation. These patients had significantly higher operative blood loss and poorer graft survival. The high incidence of postnecrotic cirrhosis in a predominantly male group of patients with advanced disease, as is evident by the high mean Childs-Pugh score and UNOS status, perhaps accounts for our observations.

Female↗
PubMed1996

Determinants of nontraditional therapy use in patients with HIV infection. A prospective study.

BACKGROUND: The popularity and use of nontraditional therapies among patients with human immunodeficiency virus (HIV) infection has grown enormously. DESIGN: A prospective, longitudinal cohort study of 56 patients aged 23 through 68 years with HIV infection followed up at the HIV clinic at a university-affiliated Veterans Affairs Medical Center. OBJECTIVE: To assess the demographic and psychologic characteristics of patients who seek nontraditional remedies, and their impact on disease progression and mortality from HIV. METHODS: A standardized, self-administered questionnaire to assess the incidence and type of nontraditional therapies used by patients with HIV. Data on demographics, medical status, physical functioning (Karnofsky performance score), CD4 lymphocyte counts, depression (Beck Depression Inventory), coping (inventory of coping with illness scale), psychological and/or emotional stress (Profile of Mood States scores), and compliance with prescribed therapy were prospectively assessed on all patients at baseline and every 6 months. RESULTS: Thirty percent of patients reported using nontraditional therapies. Nontraditional therapy users were significantly older than patients who did not use such therapies (44 vs 38 years, P = .03); with 94% of patients who used nontraditional therapy being older than 35 years compared with 56% of conventional therapy users (P = .005). Alternative therapy use did not correlate with race, education, HIV-risk group affiliation, duration of HIV seropositivity, stage of HIV disease, CD4 cell count, or Karnofsky performance scores. Nontraditional therapy users reported greater community-based acquired immunodeficiency syndrome group support (P = .06), greater perceived social support (P = .08), and significantly higher recreational or "street drugs" use (P = .02). Depression, adaptive coping, and emotional stress were not different between nontraditional and conventional therapy users; however, nontraditional therapy users were significantly more assertive (P = .04). On follow-up, CD4 cell count, HIV disease progression, physical functioning, or mortality were similar between the two groups. CONCLUSIONS: Recourse to nontraditional therapy is common among patients with HIV. Because of the possibility of untoward effects and potential adverse drug interactions associated with nontraditional therapy, HIV care givers should be aware of its use in their patients and take a history of nontraditional therapy first. Patients who choose nontraditional remedies do so not because they are depressed or emotionally disturbed, but rather because they seek greater control of the outcome of their disease. However, no beneficial effect on disease progression, CD4 cell count, or mortality was observed in these patients when compared with patients receiving only conventional medical therapy.

Adaptation, Psychological↗
PubMed1996

The changing face of candidemia: emergence of non-Candida albicans species and antifungal resistance.

OBJECTIVES: To assess the changing epidemiology of candidemia in the 1990s, to evaluate the clinical implications for the presence of non-Candida albicans in blood, and to evaluate the presence of antifungal resistance in relation to prior antifungal administration. DESIGN: Multicenter prospective observational study of patients with positive blood cultures for Candida species or Torulopsis glabrata. SETTING: Four tertiary care medical centers. RESULTS: Four hundred twenty-seven consecutive patients were enrolled. The frequency of candidemia due to non-C. albicans species significantly increased in each hospital throughout the 3.5-year study period (P = 0.01). Thirteen percent of candidemias occurred in patients who were already receiving systemic antifungal agents. Candidemias developing while receiving antifungal therapy were more likely caused by non-C. albicans species than by C. albicans species (P = 0.0005). C. parapsilosis and C. krusei were more commonly seen with prior fluconazole therapy, whereas T. glabrata was more commonly seen with prior amphotericin B therapy. Candida species isolated during episodes of breakthrough candidemia exhibited a significantly higher MIC to the antifungal agent being administered (P < 0.001). CONCLUSION: In this large scale study, the non-C. albicans species, especially T. glabrata, emerged as important and frequent pathogens causing fungemia. This finding has major clinical implications given the higher complication and mortality rate associated with the non-C. albicans species. The change in the pattern of candidemia might be partly attributed to the increase in number of immunocompromised hosts and the widespread use of prophylactic or empiric antifungal therapy. This is an ominous sign given the in vitro resistance of the non-C. albicans species to currently available antifungal agents.

Amphotericin B↗
PubMed1996

Recurrent hepatitis C virus hepatitis in liver transplant recipients receiving tacrolimus: association with rejection and increased immunosuppression after transplantation.

BACKGROUND: Recurrent hepatitis C virus is associated with significant morbidity and mortality after liver transplantation. However, the risk factors for clinical recurrence including the role of rejection and immunosuppression have not been defined in patients receiving tacrolimus (FK506) as primary immunosuppression. METHODS: Sixty-six consecutive adult liver transplant recipients receiving tacrolimus as primary immunosuppression were monitored; 31 of 66 underwent transplantation for end-stage liver disease caused by hepatitis C virus. Median follow-up for the patients in the study was 3 1/2 years. Recurrent hepatitis C virus hepatitis determined on histopathologic evaluation developed in 58% (18 of 31). A number of clinical variables including rejection and intensity of immunosuppression were assessed for patients with and without recurrence. RESULTS: Rejection episodes preceding recurrence were documented in 72% (13 of 18) of patients with recurrence compared with 23% (3 of 13) in those without recurrence (p=0.007). A total of 33% (5 of 15) of patients with no rejection experienced recurrence versus 83% (5 of 6) with one episode of rejection (p=0.06) and 80% (8 of 10) with more than one episode of rejection (p=0.04). The mean number of steroid boluses for the treatment of rejection was higher for patients with recurrence (2.3 versus 0.77, p=0.01). Overall immunosuppression (as measured by steroids boluses, recycles, OKT3, and azathioprine) was significantly more intense for patients with recurrence (p=0.013). CONCLUSIONS: Greater rejection concurrent with increased immunosuppression was associated with a higher recurrence of hepatitis C in liver transplant recipients.

Adult↗