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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

Comparative activity of ciprofloxacin, ofloxacin, levofloxacin, and erythromycin against Legionella species by broth microdilution and intracellular susceptibility testing in HL-60 cells.

Animal lung macrophages or human peripheral blood mononuclear cells have been used for testing intracellular activity of anti-Legionella antibiotics; such studies are labor intensive such that comparative antibiotic studies for the many Legionella species are few. We evaluated a human monocyte cell line (HL-60) as an alternative model. HL-60 (1.5 x 10(6) cells/well) was differentiated into adherent cell and infected with 1.5 x 10(7) CFU of Legionella pneumophilia (L. pneumophilia). Erythromycin and quinolones, ciprofloxacin, ofloxacin, and levofloxacin were added to cells at 1 and 8 x MIC. Percent (%) inhibition ratios equal to total L. pneumophila with agent divided by L. pneumophila without agent x 100 were determined at 48 h; lower ratios implied greater potency. By broth dilution in buffered yeast extract broth, the most potent agents against L. pneumophila were (MIC): ciprofloxacin (0.015-0.03), ofloxacin (0.015-0.03), levofloxacin (0.015-0.03), erythromycin (0.125-1.0 microgram/mL). In the intracellular model, the most potent inhibitors of L. pneumophila multiplication at 8 x MIC were (in order of potency) levofloxacin (24.2%), ciprofloxacin (30.6%), ofloxacin (37.1%), and erythromycin (55.0%). All the quinolones were highly active and significantly more potent against L. micdadei and L. bozemanii when compared to L. pneumophila.

Anti-Bacterial Agents↗
PubMed1998

Do in vitro susceptibility data predict the microbiologic response to amphotericin B? Results of a prospective study of patients with Candida fungemia.

Outcome for 105 patients with candidemia treated with amphotericin B was correlated with amphotericin B in vitro susceptibility results. Thirty-three patients had microbiologic failure, which was defined as persistence of Candida in the bloodstream despite > or = 3 days of amphotericin B. Amphotericin B minimum inhibitory concentrations (MICs) were determined by the National Committee for Clinical Laboratory Standards methodology. After determination of MICs, the minimal lethal concentrations (MLCs) were determined. The isolates tested yielded a narrow range of amphotericin B MICs (0.06-2 microg/mL); only 5% (5/105) exhibited MICs > or = 1 microg/mL. The MLC range, on the other hand, was significantly broader (0.125 to > 16 microg/mL); 24% (25/105) exhibited MLCs > or = 1 microg/mL. The strongest predictor for microbiologic failure was 48-h MLC (P < .001), followed by 24-h MLC (P = .03) and 48-h MIC (P = .11). A resistant break point for amphotericin B of > 1 microg/mL for MLC and > or = 1 microg/mL for MIC could be inferred from this study.

Amphotericin B↗
PubMed1998

Intermittent use of copper-silver ionization for Legionella control in water distribution systems: a potential option in buildings housing individuals at low risk of infection.

One copper-silver ionization system was sequentially installed onto the hot-water recirculation lines of two hospital buildings colonized with Legionella pneumophila, serogroup 1. A third building with the same water supply and also colonized with Legionella served as a control. Four weeks after activation of the system, distal site positivity for Legionella in the first test building dropped to zero. After operating for 16 weeks, the system was disconnected and installed onto the second test building. Twelve weeks of disinfection reduced the distal site positivity for Legionella in the second test building to zero. Legionella recolonization did not occur in the first test building for 6-12 weeks and in the second test building for 8-12 weeks after inactivation of the system. The control building remained Legionella-positive throughout the experimental period. A significantly higher copper concentration was found in the biofilm taken from a sampling device than in that from water. This is likely to be the reason that the copper-silver ionization system had the residual effect of preventing early recolonization. Our study raises the possibility that one copper-silver unit could be rotated among several buildings to maintain a Legionella-free environment. Such an approach may be cost-effective for buildings housing individuals at low risk for contracting legionnaires' disease.

Biofilms↗
PubMed1998

Activity of azithromycin, clarithromycin, roxithromycin, dirithromycin, quinupristin/dalfopristin and erythromycin against Legionella species by intracellular susceptibility testing in HL-60 cells.

We evaluated a human monocyte cell line (HL-60) as a model for testing the intracellular activity of anti-Legionella antibiotics; 1.5 x 10(6) HL-60 cells/well were differentiated into adherent cells and infected with 1.5 x 10(7) cfu of Legionella pneumophila. The most active agents against L. pneumophila as judged by broth dilution MICs were (in order of activity) azithromycin, clarithromycin, roxithromycin, quinupristin/dalfopristin, erythromycin and dirithromycin. The most active inhibitors of L. pneumophila intracellular multiplication were (in order of activity) azithromycin, erythromycin, quinupristin/dalfopristin, roxithromycin, dirithromycin and clarithromycin. All the agents were highly active against Legionella micdadei and Legionella bozemanii when compared with L. pneumophila.

Anti-Bacterial Agents↗
PubMed1998

Pulmonary infiltrates in the surgical ICU: prospective assessment of predictors of etiology and mortality.

A prospective cohort study of 129 consecutive patients developing pulmonary infiltrates in the surgical ICU was conducted to determine the predictors and outcome of pulmonary infiltrates. Most common etiologies of pulmonary infiltrates were pneumonia (30%), pulmonary edema (29%), acute lung injury (15%), and atelectasis (13%). Enteral nutrition was associated with a significantly lower incidence of acute lung injury as compared with pneumonia (22% vs 58%, p = 0.012). Patients with liver disease were significantly more likely to have pulmonary infiltrates due to acute lung injury as compared with other etiologies (p = 0.02). Clinical pulmonary infection score (Pugin score) > 6 virtually excluded acute lung injury, pulmonary edema, or atelectasis as etiologies of pulmonary infiltrates. Nosocomial Haemophilus/pneumococcal pneumonia occurred significantly earlier in the ICU as compared with Gram-negative (p = 0.05) or methicillin-resistant Staphylococcus aureus pneumonia (p = 0.01). Pneumonia in trauma patients was significantly more likely to be due to Haemophilus/pneumococcus as compared with all other ICU patients (54% vs 0%, p = 0.0004). These data have implications for treatment of patients with nosocomial pneumonia in the ICU.

APACHE↗
PubMed1998

Legionella: a major opportunistic pathogen in transplant recipients.

Legionella have a predilection for infecting immunocompromised patients, and transplant recipients have the highest risk. Legionella spp have been the most common cause of nosocomial pneumonia among transplant recipients at selected medical centers. Diagnosis is dependent on the ability of the clinical microbiology laboratory to isolate the organism by culture; therefore, the disease is easily overlooked. The mode of transmission of Legionella pneumophila is likely aspiration in transplant recipients. Clinical manifestations are similar to that of other bacterial pneumonias, although diarrhea is often prominent. The quinolone antibiotics (especially ciprofloxacin) are the antibiotics of choice because, unlike the macrolides or rifampin, they do not interact with the immunosuppressive agents used to counter rejection. Prevention of nosocomial legionellosis involves disinfection of the hospital's potable water system. Effective disinfection methods include superheat and flush or copper-silver ionization; hyperchlorination is no longer recommended. Routine culture surveillance directed at the hospital water supply for Legionella is mandatory in hospitals caring for transplant patients.

Humans↗
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↗