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Biomedical subjects

V L Yu

Publications and source records attributed to V L Yu.

At least 199 records · Page 11Linked to original sources
PubMed1987

Comparative assessment of chlorine, heat, ozone, and UV light for killing Legionella pneumophila within a model plumbing system.

Nosocomial Legionnaires disease can be acquired by exposure to the organism from the hospital water distribution system. As a result, many hospitals have instituted eradication procedures, including hypercholorination and thermal eradication. We compared the efficacy of ozonation, UV light, hyperchlorination, and heat eradication using a model plumbing system constructed of copper piping, brass spigots, Plexiglas reservoir, electric hot water tank, and a pump. Legionella pneumophila was added to the system at 10(7) CFU/ml. Each method was tested under three conditions; (i) nonturbid water at 25 degrees C, (ii) turbid water at 25 degrees C, and (iii) nonturbid water at 43 degrees C. UV light and heat killed L. pneumophila most rapidly and required minimal maintenance. Both UV light and heat (60 degrees C) produced a 5 log kill in less than 1 h. In contrast, both chlorine and ozone required 5 h of exposure to produce a 5 log decrease. Neither turbidity nor the higher temperature of 43 degrees C impaired the efficacy of any of the disinfectant methods. Surprisingly, higher temperature enhanced the disinfecting efficacy of chlorine. However, higher temperature accelerated the decomposition of the chlorine residual such that an additional 120% volume of chlorine was required. All four methods proved efficacious in eradicating L. pneumophila from a model plumbing system.

Chlorine↗
PubMed1987

Legionella species as hospital-acquired respiratory pathogens.

Nosocomial pneumonia caused by legionella is an increasingly recognized entity. Legionella sp responsible for documented nosocomial disease include Legionella pneumophila, Tatlockia micdadei, Legionella bozemanii, Legionella dumoffi and Legionella oakridgensis. The clinical presentation is nonspecific although diarrhea occurs frequently. Hyponatremia occurs significantly more frequently in legionnaires' disease than pneumonias caused by other agents. Chest roentgenographic findings are nonspecific, although cavitation can be seen in immunosuppressed patients. Laboratory methods require the use of direct fluorescent antibody (DFA) stains, culture using selective media, serologic testing, and detection of antigen in urine. The DFA test is not sensitive; however, it does correlate with the severity of disease. Culture from sputa is now feasible. Bronchoalveolar lavage is a promising technique for obtaining specimens. The ideal specimen for culture is that obtained by transtracheal aspiration, which bypasses oropharyngeal contamination. Combination therapy of erythromycin and rifampin is recommended for selected patients. Because the source of the organism is the hospital water distribution system, we recommend routine environmental surveillance, especially in hospitals in which organ transplants are performed. The role of cooling towers as a vector for dissemination of the organism is disputed. Disinfection of the water supply can be accomplished by using heat eradication. Chlorination has generally proven unsatisfactory because of organism persistence as well as corrosive damage to the plumbing system from the chlorine. Both physician awareness and availability of specialized laboratory testing are necessary for the detection of cases.

Cross Infection↗
PubMed1987

The radiologic manifestations of Legionella pneumonia.

A number of radiologic features on chest X-ray may aid in diagnosis and management of the patient with legionella infection. The infiltrates in legionnaires' disease frequently progress despite initiation of appropriate antibiotic therapy. Pleural effusion is common and occasionally seen even in the absence of lung field infiltrates. Pleural-based infiltrates associated with pleuritic pain may mimic pulmonary embolism. Circumscribed peripheral densities are commonly seen in immunosuppressed patients. Cavitation is also a prominent feature in this patient group and may develop during clinical improvement. Radiographic severity does not correlate with clinical outcome. Resolution of infiltrates may be slow, and the tendency for delayed clearing should be considered before initiating further invasive diagnostic investigation. Infections due to Tatlockia (Legionella) micdadei and Legionella bozemanii are more commonly reported in immunocompromised hosts; the radiographic manifestations are similar to those seen in Legionella pneumophila infection in the immunosuppressed.

Adult↗
PubMed1987

Infections caused by the Pittsburgh pneumonia agent.

Of the Legionellaceae family, Pittsburgh pneumonia agent (Tatlockia micdadei, Legionella micdadei) is second only to Legionella pneumophila in causing human pneumonia. In nosocomial infection, the patients tend to be immunosuppressed. The clinical presentation is nonspecific, although in immunosuppressed hosts the presentation may mimic that of pulmonary embolus (pleuritic chest pain, nonproductive cough, pleural-based densities on chest rontgenogram). The reservoir for the organism is water, and prevention of nosocomial infections can be accomplished by disinfection of the water supply. Diagnosis is best established by isolation of the organism from respiratory secretions by using selective, dye-containing buffered charcoal-yeast extract agar. The organisms can be acid-fast when clinical specimens are stained. Erythromycin is the antibiotic of choice, although tetracyclines, trimethoprim-sulfamethoxazole, and rifampin have also proved to be efficacious.

Humans↗
PubMed1987

Infections caused by Pseudomonas maltophilia. Expanding clinical spectrum.

Pseudomonas maltophilia (Xanthomonas maltophilia) is a frequently isolated commensal that is gaining increasing recognition as an opportunistic pathogen in debilitated hosts. We report three unusual infections due to P maltophilia that illustrate the ability of the organism to cause life-threatening illness. We describe a case of postoperative meningitis, a case of recurrent bacteremia complicated by ecthyma gangrenosum, and a case of native valve endocarditis in a drug addict. Because of frequent isolation from noninfected sites, the pathogenic potential of P maltophilia may be overlooked. The notable resistance of this organism is commonly used beta-lactam and aminoglycoside antibiotics may complicate therapy.

Aged↗
PubMed1986

Staphylococcus aureus nasal carriage and infection in patients on hemodialysis. Efficacy of antibiotic prophylaxis.

We conducted a five-year prospective controlled study of prophylaxis of Staphylococcus aureus nasal carriage and infection among patients in a hemodialysis unit. Carriers tended to have chronic colonization with a single phage type. S. aureus infections occurred significantly more frequently in carriers than in noncarriers and, in 93 percent of the infected carriers, were caused by the same phage type as that carried in the nares. Neither intravenous vancomycin nor topical bacitracin was found to be efficacious in eradicating nasal carriage. However, oral rifampin given for five days decreased S. aureus carriage over a one-month follow-up period, but within three months colonization of the nares recurred in most carriers, often with an S. aureus of the original phage type. Carriers were then randomly assigned to receive either rifampin or no prophylaxis. Rifampin was readministered at three-month intervals if culture of the anterior nares yielded S. aureus. Infections with S. aureus occurred significantly more frequently in carriers given no prophylaxis than in those given a full course of rifampin. S. aureus resistant to rifampin was isolated from the anterior nares of four patients, but these isolates were not implicated in any infections. The incidence of infection at the dialysis access site, skin, and soft tissue of patients on hemodialysis can be decreased by interventions directed at nasal carriage of S. aureus.

Administration, Intranasal↗
PubMed1986

Pneumococcal pericarditis. Diagnostic usefulness of counterimmunoelectrophoresis and computed tomographic scanning.

Although counterimmunoelectrophoresis (CIE) analysis of cerebrospinal fluid has proved useful in the diagnosis of meningitis, there has been little experience with its use in analyzing pericardial fluid. We describe two patients with pneumococcal pneumonia whose hospital course was complicated by purulent pericarditis. In one patient, results of a computed tomographic scan were important in suggesting the diagnosis. Results of a Gram's stain and culture of pericardial fluid failed to yield any organisms, presumably because both patients had received nine days of beta-lactam antibiotic therapy. However, the results from CIE analysis of pericardial fluid in both cases were positive for Streptococcus pneumoniae. In one patient, for whom capsular typing of the organism was performed, the pneumococcus type isolated from pericardial fluid matched the type isolated previously from a blood sample. The results of CIE can allow focused antibiotic therapy by establishing the correct diagnosis.

Antigens, Bacterial↗
PubMed1986

Cefazolin vs moxalactam? A double-blind randomized trial of cephalosporins in head and neck surgery.

Cefazolin and moxalactam were compared in a prospective randomized double-blind trial of 118 patients undergoing oncologic head and neck surgery. Both antibiotics were given 2 g every four hours for four doses. Five infections were encountered in the cefazolin group (8.5%) and two infections in the moxalactam group (3.4%); this difference was not statistically significant. This assessment does not indicate, however, that the two regimens are equally efficacious.

Cefazolin↗
PubMed1986

Significance of isolation of Aspergillus from the respiratory tract in diagnosis of invasive pulmonary aspergillosis. Results from a three-year prospective study.

The isolation of Aspergillus species from respiratory secretions has been regarded as being of limited usefulness in the antemortem diagnosis of invasive pulmonary aspergillosis. One hundred and eight consecutive patients were evaluated in whom Aspergillus species were isolated from respiratory secretions. Invasive aspergillosis was not demonstrated in non-immunosuppressed patients or in patients with solid tumors in the absence of neutropenia. Lung tissue was examined in 17 patients with leukemia and/or neutropenia; all had invasive aspergillosis. Tissue examination was not performed in 20 neutropenic patients; of 17 not receiving antifungal therapy, 16 died. Multivariate statistical analysis showed that neutropenia and absence of cigarette smoking were significant predictors of invasive aspergillosis in patients with respiratory tract cultures yielding Aspergillus. All cases of invasive aspergillosis were associated with A. fumigatus or A. flavus. The isolation of A. fumigatus or A. flavus from the respiratory tract of a patient with leukemia and/or neutropenia is highly predictive of invasive infection. Empiric amphotericin B therapy, without the necessity for tissue diagnosis, should be considered in this patient subgroup.

Adolescent↗
PubMed1986

Potential in-hospital modes of transmission of Legionella pneumophila. Demonstration experiments for dissemination by showers, humidifiers, and rinsing of ventilation bag apparatus.

The mode of transmission of nosocomial legionellosis remains uncertain. Aerosolization of Legionella pneumophila by showers, humidifiers, and respiratory equipment rinsed in tap water was evaluated using plate-settling culture and air aspirator methods. All protocols simulated the actual hospital setting including use of humidifier equipment used in hospital patient rooms and water from faucets and showerheads in hospitals with nosocomial Legionnaires' disease. Protocols for humidifier and shower experiments mimicked the procedure actually used in hospitals by health care personnel. Showering failed to produce aerosols of L. pneumophila; however, portable humidifiers readily generated aerosols of L. pneumophila that disseminated throughout a two-bed patient room. Intensity of aerosolization directly correlated with the degree of L. pneumophila contamination of the tap water used to fill the humidifier. Rinsing of ventilation bag apparatus with tap water led to isolation of L. pneumophila from culture plates after the ventilation bags were squeezed. Thus, L. pneumophila could be aerosolized or directly instilled into a patient's bronchial tree following routine measures for cleaning ventilation bag apparatus with tap water. On the basis of these results, the use of humidifiers filled with tap water has been discontinued and sterile water is recommended for rinsing ventilation bag apparatus and tubing.

Aerosols↗
PubMed1986

A note on symbiosis of Legionella pneumophila and Tatlockia micdadei with human respiratory flora.

Sixteen micro-organisms, representing clinically important respiratory microflora, were tested for their ability to stimulate the growth of Legionella pneumophila and Tatlockia micdadei in nutritionally-deficient agar media. Nutritional symbiosis, indicated by the appearance of satellite colonies of L. pneumophila or T. micdadei, was observed for H. influenzae and N. meningitidis. This interaction between normal flora and pathogens of the respiratory tract may have clinical relevance in the pathogenesis of Legionnaires' disease and Pittsburgh pneumonia.

Bacterial Physiological Phenomena↗
PubMed1986

Susceptibility of members of the family Legionellaceae to thermal stress: implications for heat eradication methods in water distribution systems.

To ascertain the feasibility of heat inactivation as an eradication method applicable to all members of the family Legionellaceae, we tested the heat resistance of 75 isolates which represented 19 members of this family of organisms. The ranges of thermal death times at 60, 70, and 80 degrees C were 1.3 to 10.6, 0.7 to 2.6, and 0.3 to 0.7 min, respectively. These data suggest that the method of heat eradication will be effective against all members of the family Legionellaceae.

Hot Temperature↗
PubMed1985

Nosocomial legionellosis in surgical patients with head-and-neck cancer: implications for epidemiological reservoir and mode of transmission.

A prospective pneumonia study was conducted simultaneously on head-and-neck surgery wards at two hospitals over 2 years; one hospital had a water supply contaminated with Legionella pneumophila but no record of having had a case of legionella pneumonia, and the other had just decontaminated its water supply because of known endemic nosocomial legionellosis. Special laboratory tests for legionella were done on all cases of nosocomial pneumonia irrespective of clinical impression. Over the first 18 months, the rate of nosocomial legionellosis was 30% at the first hospital and 0% at the second. Patients who underwent laryngectomy did not acquire the disease. Hyperchlorination at the first hospital was followed by a fall (p less than 0.01) in legionella pneumonias. Thus legionella pneumonias can be overlooked if special laboratory tests are not applied routinely, and surgical patients with head-and-neck cancer may be at high risk of nosocomial legionellosis because of the potential for pulmonary aspiration of contaminated water or orophyaryngeal microflora and/or frequent manipulation of the respiratory tract. This study demonstrates the benefits of examining the environment for legionella despite the absence of documented disease.

Chlorine↗
PubMed1985

Isolation of Legionella pneumophila from the cold water of hospital ice machines: implications for origin and transmission of the organism.

Although the mode of transmission of L. pneumophila is as yet unclear, the hot water distribution system has been shown to be the reservoir for Legionella within the hospital environment. In this report we identify a previously unrecognized reservoir for L. pneumophila within the hospital environment, ie, the cold water dispensers of hospital ice machines. The cold water dispensers of 14 ice machines were cultured monthly over a 1-year period. Positive cultures were obtained from 8 of 14 dispensers, yielding from 1 to 300 CFU/plate. We were able to link the positivity of these cold water sites to the incoming cold water supply by recovering L. pneumophila from the cold water storage tank, which is directly supplied by the incoming municipal water line. This was accomplished by a novel enrichment experiment designed to duplicate the conditions (temperature, sediment, stagnation, and continuous seeding) of the hot water system. Our data indicate that significant contamination of cold water outlets with L. pneumophila can occur. Although no epidemiologic link to disease was made, the fact that the primary source of a patient's drinking water is from the ice machines warrants further investigation of these water sources as possible reservoirs.

Bacteriological Techniques↗
PubMed1985

Pharmacokinetic and therapeutic trial of sultamicillin in acute sinusitis.

Sultamicillin, an antibiotic combining ampicillin and the beta-lactamase inhibitor sulbactam, was administered to 13 patients diagnosed as having acute sinusitis. Specimens from sinus were obtained for all 13 patients by transantral puncture. Pharmacokinetics, bacteriology, and therapeutic efficacy were assessed. Eighty-five percent (11 of 13) were cured; two treatment failures were subsequently shown to have chronic (rather than acute) sinusitis during surgical exploration. Diarrhea was frequently encountered, and Clostridium difficile-associated enteritis was documented for one patient. Beta-lactamase-producing organisms were not encountered in this study; however, this study provides impetus for further controlled clinical trials.

Adult↗