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Biomedical subjects

V L Yu

Publications and source records attributed to V L Yu.

At least 217 records · Page 12Linked to original sources
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↗
PubMed1985

Ecology of Legionella pneumophila within water distribution systems.

The reservoir for hospital-acquired Legionnaires disease has been shown to be the potable water distribution system. We investigated the influence of the natural microbial population and sediment (scale and organic particulates) found in water systems as growth-promoting factors for Legionella pneumophila. Our in vitro experiments showed that: (i) water from hot-water storage tank readily supported the survival of L. pneumophila, (ii) the concentration of sediment was directly related to the survival of L. pneumophila, (iii) the presence of environmental bacteria improved the survival of L. pneumophila via nutritional symbiosis, (iv) the combination of sediment and environmental bacteria acted synergistically to improve the survival of L. pneumophila, and (v) the role of sediment in this synergistic effect was determined to be nutritional. Sediment was found to stimulate the growth of environmental microflora, which in turn stimulated the growth of L. pneumophila. These findings confirm the empiric observations of the predilection of L. pneumophila for growth in hot-water tanks and its localization to sediment. L. pneumophila occupies an ecological niche within the potable water system, with interrelationships between microflora, sediment, and temperature.

Bacteria↗
PubMed1985

Tatlockia micdadei (Pittsburgh pneumonia agent) growth kinetics may explain its infrequent isolation from water and the low prevalence of Pittsburgh pneumonia.

Sediment and indigenous microflora taken from water distribution systems has been shown to promote the survival of Legionella pneumophila. The effect of sediment and indigenous microflora on Tatlockia micdadei (Pittsburgh pneumonia agent, PPA) was evaluated by growth curve experiments. Symbiosis between PPA and environmental bacteria was demonstrated by satellitism experiments. Unlike L. pneumophila, the concentration of PPA remained stationary in test tube suspensions containing both microflora and sediment. The difference in the ecology between the two organisms may explain the infrequent environmental recovery of PPA and, ultimately, the epidemiologic differences between Legionnaires disease and Pittsburgh pneumonia.

Bacteria↗
PubMed1985

Isolation of Legionella pneumophila from blood with the BACTEC system: a prospective study yielding positive results.

In a prospective study of 16 patients with Legionnaires disease confirmed by cultural isolation of Legionella pneumophila from the respiratory tract, 38% (6 of 16) had positive blood cultures. Daily subcultures were made onto buffered charcoal-yeast extract plates from 6B aerobic and 7C anaerobic BACTEC blood culture bottles (Johnston Laboratories, Inc., Towson, Md.). Isolation of L. pneumophila was achieved from both aerobic and anaerobic bottles. L. pneumophila growth indices failed to exceed the BACTEC threshold limits; thus, the organism would have been overlooked despite its presence in the blood culture bottles. Bacteremic patients had statistically significant higher quantities of L. pneumophila isolated from sputum and visualized on direct fluorescent antibody stains. Thus, the potential exists for improved diagnosis of Legionella infection by a relatively noninvasive procedure (blood culture) with an instrument already in use in many hospital laboratories.

Aerobiosis↗
PubMed1985

Nosocomial Legionella pneumonia in a population of head and neck cancer patients.

A prospective study of nosocomial pneumonia following major head and neck surgery was conducted when it was recognized that Legionella contaminated the hospital water supply. Legionella pneumonia had not previously been diagnosed in our hospital. Every head and neck patient with nosocomial pneumonia had specialized tests performed. During the 18-month study period, 29% of patients with nosocomial pneumonia (7 of 27) had evidence of legionellosis. The sero-group of the infecting Legionella was the same as the Legionella in the water supply. Legionella was seen exclusively in patients with clinically evident aspiration. Legionella pneumonia was not demonstrated in patients undergoing laryngectomy. We conclude that specialized testing must be employed to avoid delay in diagnosis and failure to administer specific antibiotic therapy. Legionellosis may be underdiagnosed in hospitalized patients.

Antibodies, Bacterial↗
PubMed1984

Efficacy of two third-generation cephalosporins in prophylaxis for head and neck surgery.

Optimal antimicrobial prophylaxis during head and neck surgery is as yet unclear. The semisynthetic third-generation cephalosporin antibiotics would appear to have potential usefulness because of their broad antibacterial spectrum, favorable pharmacokinetic properties, and record of safety. Eighty patients were prospectively randomized into this placebo-controlled, double-blind study to receive either placebo, cefoperazone sodium, or cefotaxime sodium preoperatively and for 24 hours postoperatively. Infection rates were 78% for the placebo group and 10% for the group receiving the cephalosporin antibiotics. Infections were polymicrobial. Anaerobic bacteria constituted 42% of the pathogens isolated. Wound and serum antibiotic concentrations exceeded the minimal inhibitory concentration of the bacterial flora. This study establishes the necessity of antimicrobial prophylaxis for contaminated oncologic procedures of the head and neck. Our experience indicates that cefoperazone and cefotaxime are particularly useful.

Bacteria↗
PubMed1984

In-vitro synergy testing of triple antibiotic combinations against Staphylococcus epidermidis isolates from patients with endocarditis.

In-vitro synergy testing was performed against ten blood or valve isolates of Staphylococcus epidermidis taken from patients with endocarditis. A three-dimensional microtitre checkerboard method was used for evaluation of vancomycin-rifampicin-gentamicin. The triple combination of vancomycin plus rifampicin plus gentamicin was found to be synergistic in 70% of the isolates. Vancomycin plus rifampicin was not synergistic. Oral agents including dicloxacillin, rifampicin, and fusidic acid were also evaluated. Four methicillin-resistant isolates were relatively resistant to dicloxacillin (MIC greater than 0.79 mg/l) but all four isolates were susceptible to fusidic acid alone and rifampicin alone. The triple combination of dicloxacillin plus fusidic acid plus rifampicin was found to be synergistic in 50% of the isolates and generally superior to any two-drug combination raising the possibility of an effective oral combination of antibiotics.

Anti-Bacterial Agents↗
PubMed1984

Penetration of cefoperazone into surgical wound drainage in patients undergoing head and neck surgery.

Cefoperazone penetration into skeletal muscle and wound drainage in patients undergoing major surgery of the head and neck was measured by high-pressure liquid chromatography. Cefoperazone (2 g) was infused over 30 min before surgery and every 8 h for three postoperative doses. Simultaneous samples of serum and sternomastoid muscle were collected in 18 patients at 135 to 480 min after infusion. Mean cefoperazone concentrations in muscle tissue were 17.1% of those in simultaneously collected serum. Steady-state wound drainage concentrations after the fourth dose of cefoperazone averaged 55.2 micrograms/ml at 1 to 2 h and 62.1 micrograms/ml at 2 to 3 h. Simultaneous steady-state serum and wound fluid samples were obtained at regular intervals in six patients. In all patients, the peak level in wound fluid exceeded 25 micrograms/ml. Thus, cefoperazone reaches interstitial fluid concentration in soft tissue that exceeds the MICs required to inhibit the usual pathogens found at the site of wound infection after head and neck surgery.

Cefoperazone↗
PubMed1984

Addition of rifampin to carboxypenicillin-aminoglycoside combination for the treatment of Pseudomonas aeruginosa infection: clinical experience with four patients.

Four patients infected with Pseudomonas aeruginosa were treated with the triple therapy of carboxypenicillin (carbenicillin or ticarcillin), aminoglycoside (gentamicin or tobramycin), and rifampin. Two patients had P. aeruginosa endocarditis, one had bacteremia associated with granulocytopenia, and one had neurosurgical meningitis. In all four cases, the clinical condition of the patient deteriorated on combined antipseudomonal penicillin and aminoglycoside therapy. All patients had persistent blood cultures (throughout a 3- to 30-day period) or cerebrospinal fluid cultures (throughout a 24-day period) while receiving penicillin-aminoglycoside therapy. Rifampin, 600 mg every 8 h orally, was added to the penicillin-aminoglycoside regimen. All four patients defervesced within 24 h after the initiation of rifampin. In addition, all four patients experienced sterilization of blood and cerebrospinal fluid cultures within 24 h of therapy. The emergence of rifampin-resistant P. aeruginosa was not observed. Ultimately, two patients survived their infection; the other two patients succumbed to complications of their underlying disease. This clinical experience should provide a stimulus for a controlled evaluation of rifampin as a component of multiple drug therapy directed against P. aeruginosa.

Adult↗
PubMed1984

Clinical laboratory differentiation of Legionellaceae family members with pigment production and fluorescence on media supplemented with aromatic substrates.

A systematic study of pigment production (browning) and fluorescence (extracellular yellow-green and intracellular blue-white) by nine Legionellaceae species was performed. A total of 56 strains representing Tatlockia micdadei (Pittsburgh pneumonia agent), Legionella pneumophila, Legionella jordanis, Legionella longbeachae, Legionella oakridgensis, Legionella wadsworthii, Fluoribacter bozemanae, Fluoribacter gormanii, and Fluoribacter dumoffii could be separated on media supplemented with tyrosine plus cystine, 3,4-diaminobenzoic acid, 3,5-diaminobenzoic acid, and 3-aminotyrosine. Parallel testing by hippurate hydrolysis and the bromocresol purple spot test enabled the identification of Legionellaceae species 24 to 72 h after primary isolation. This schema may be a practical alternative to species-specific antisera methods (slide agglutination or direct immunofluorescence) in the identification of members of the family Legionellaceae.

Amino Acids↗
PubMed1984

Pneumonia caused by Pittsburgh pneumonia agent: radiologic manifestations.

Using an objective scoring system, chest radiographs were reviewed in 23 cases of pneumonia due to the Pittsburgh pneumonia agent (PPA, Tatlockia micdadei, Legionella micdadei), including six cases of pneumonia with simultaneous isolation of PPA and L pneumophila (Legionnaires' disease). Infiltrates were typically segmental to lobar; nodular infiltrates were noted in three cases. Spread to additional lobes after presentation occurred in four of 17 PPA infections. Pneumonia caused by both PPA and L pneumophila was unusually severe, with involvement of all lobes occurring in four of six cases, compared with one of 17 cases of PPA infection (p less than 0.02). Radiographic severity did not correlate with underlying disease, immune status, or outcome. The majority of patients receiving erythromycin demonstrated objective radiologic improvement. In a patient population that included nonimmunosuppressed patients, nodule formation and rapid radiologic progression were not found to be characteristic of PPA pneumonia.

Aged↗
PubMed1984

Addition of rifampin to ticarcillin-tobramycin combination for the treatment of Pseudomonas aeruginosa infections: assessment in a neutropenic mouse model.

The efficacy of ticarcillin (100 mg/kg), tobramycin (1 mg/kg), and rifampin (43 and 7.2 mg/kg) individually and in combination was assessed in neutropenic mice infected with an LD90 of one of four Pseudomonas aeruginosa isolates. The study end point was survival at 120 hours after infection. Treatment with the triple combination, ticarcillin plus tobramycin plus rifampin (43 mg/kg), was significantly superior to the double combination of ticarcillin plus tobramycin (p less than 0.01). Although treatment with rifampin (43 mg/kg) alone yielded results similar to treatment with the triple combination in mice infected with three of the four isolates, rifampin-resistant mutants (minimal inhibitory concentration greater than 1000 micrograms/ml) of P. aeruginosa were frequently isolated from surviving mice (26% of mice sampled). In contrast, in mice treated with the triple combination, rarely were rifampin-resistant mutants isolated (3% of mice sampled). Rifampin alone was active against P. aeruginosa isolates only when peak serum concentrations of rifampin exceeded the rifampin minimal bactericidal concentration of the infecting isolate. The addition of rifampin to a "standard" therapy of antipseudomonal penicillin plus aminoglycoside may be useful in the treatment of serious P. aeruginosa infection.

Animals↗
PubMed1983

Diagnosis of Legionnaires' disease. An update of laboratory methods with new emphasis on isolation by culture.

A prospective clinical study of 40 cases of legionnaires' disease combined with serial laboratory examinations enabled us to present an update as well as new recommendations concerning the use of diagnostic tests for legionnaires' disease. Transtracheal aspirate specimens are the optimal specimen for recovery of Legionella pneumophila by culture as well as the most sensitive method for early diagnosis. In addition, with recent improvements in culture media and methodology, L pneumophila can now be readily isolated from sputum. Examination of respiratory specimens by direct immunofluorescence (DFA) is useful, but the sensitivity is much less than that of culture. The yield from DFA examination directly correlates with the number of L pneumophila recoverable by cultural methods; thus, the DFA test result may be negative in an early or mild case of legionnaires' disease. Antibody titers were elevated in 27% of cases within one week of onset of pneumonia and may, therefore, be useful in early diagnosis in selected patients.

Antibodies, Bacterial↗
PubMed1983

Legionellaceae in the hospital water-supply. Epidemiological link with disease and evaluation of a method for control of nosocomial legionnaires' disease and Pittsburgh pneumonia.

An epidemiological link was found between contamination of a hospital water-supply by Legionella pneumophila and by Pittsburgh pneumonia agent (PPA) and subsequent cases of nosocomial legionnaires' disease and Pittsburgh pneumonia. The extent of L pneumophila isolation from the water-supply paralleled the occurrence of disease. Whenever L pneumophila was isolated from more than 30% of ten selected water sites, nosocomial legionellosis occurred. The temperature of the hot water tanks was raised to 60-77 degrees C for 72 h, and water outlets were flushed for 30 min with hot water. A decline in numbers of L pneumophila and PPA in the water-supply was followed by a fall in the incidence of legionnaires' disease and Pittsburgh pneumonia. In addition, intermittent raising of the temperature in the hot water system decreased both the number of months in which disease occurred and the proportion of nosocomial pneumonias caused by these organisms.

Cross Infection↗
PubMed1983

Nosocomial Legionnaires' disease uncovered in a prospective pneumonia study.

Most hospitals have yet to record a case of nosocomial legionnaires' disease; the importance of isolation of Legionella pneumophila in the water system of such an institution is unclear. We undertook a prospective pneumonia study in tandem at a veterans hospital where legionnaires' disease was known to be endemic and a community teaching hospital where legionnaires' disease had never been documented. Legionella serological tests were performed on all patients with pneumonia; selective culture media and direct fluorescent antibody testing for Legionella were made readily available. Simultaneous environmental surveys for Legionella were performed. At the community hospital, we discovered that 64% of sites in the water distribution system yielded L pneumophila and that 14.3% of nosocomial pneumonias were legionnaires' disease. The epidemiologic implications of these findings are discussed. Options concerning case detection and eradication measures in the face of hospital water contamination with L pneumophila are presented.

Adult↗
PubMed1983

Simultaneous infection with Legionella pneumophila and Pittsburgh pneumonia agent. Clinical features and epidemiologic implications.

Nosocomial pneumonia caused simultaneously by two organisms, Legionella pneumophila and the Pittsburgh pneumonia agent, was documented in seven patients in one institution. In all seven cases, both organisms were demonstrated by isolation from culture or visualization by direct immunofluorescence. Four patients died as a result of pneumonia, including two who received erythromycin therapy. The hospital water distribution system appeared to be the reservoir for both L. pneumophila and Pittsburgh pneumonia agent. These seven cases constituted 26.9 percent and 17.9 percent of the cases of Pittsburgh pneumonia agent and Legionnaires' disease, respectively, at one institution. Given this relatively high incidence of dual infection, it is likely that the mode of transmission for both organisms is identical. Dual infection may account for some cases of antibody response to more than one Legionella species. Historical parallels of the discovery of L. pneumophila and Pittsburgh pneumonia agent are reviewed.

Cross Infection↗