Shawna L. Stratton

Pathogenic Aspergillus Species Recovered from a Hospital Water System: A 3-Year Prospective Study

Nosocomial aspergillosis, a life-threatening infection in immunocompromised patients, is thought to be caused primarily by Aspergillus organisms in the air. A 3-year prospective study of the air, environmental surfaces, and water distribution system of a hospital in which there were known cases of aspergillosis was conducted to determine other possible sources of infection. Aspergillus species were found in the hospital water system. Significantly higher concentrations of airborne aspergillus propagules were found in bathrooms, where water use was highest (2.95 colony-forming units [cfu]/m(3)) than in patient rooms (0.78 cfu/m(3); P=.05) and in hallways (0.61 cfu/m(3); P=.03). A correlation was found between the rank orders of Aspergillus species recovered from hospital water and air. Water from tanks yielded higher counts of colony-forming units than did municipal water. An isolate of Aspergillus fumigatus recovered from a patient with aspergillosis was genotypically identical to an isolate recovered from the shower wall in the patients room. In addition to the air, hospital water systems may be a source of nosocomial aspergillosis.

Cleaning Patient Shower Facilities: A Novel Approach to Reducing Patient Exposure to Aerosolized Aspergillus Species and Other Opportunistic Molds

We previously have demonstrated that the hospital water-distribution system could be a reservoir for airborne molds that leads to secondary aerosolization of these molds in patient shower facilities. In this report, we show that cleaning the floors of patient shower facilities in a bone marrow transplantation unit reduced the mean air concentrations of molds, including Aspergillus species (from 12 cfu/m3 to 4 cfu/m3; P=.0047).

Concentrations of biotin metabolites in human milk

Because estimates of the biotin requirement for infants currently are based on the biotin concentration in human milk, we sought to determine whether inactive biotin metabolites are present. Samples were collected for 7 weeks post partum from 15 healthy women. Biotin and the inactive metabolites bisnorbiotin and biotin sulfoxide were measured by means of a high-performance liquid chromatography avidin-binding assay. At 8 days post partum the proportion of biotin was 44%, bisnorbiotin 48%, and biotin sulfoxide 8%. Although biotin content increased post partum (p < 0.003), the metabolites remained an important portion of the total providing evidence that accurate measurement of biotin in human milk requires an assay that is specific for biotin.

Plasma concentration of 3-hydroxyisovaleryl carnitine is an early and sensitive indicator of marginal biotin deficiency in humans

BACKGROUND Blood-based indicators of biotin status in humans were shown to be useful tools in several clinical situations, including pregnancy. We previously validated the activity of the biotin-dependent enzyme propionyl-coenzyme A carboxylase (PCC) in lymphocytes as a sensitive and specific blood-based indicator of marginal degrees of biotin deficiency. However, the measurement of PCC activity in population studies presents substantial analytic challenges. 3-Hydroxyisovaleryl carnitine (3HIA-carnitine) increases in response to the decreased activity of the biotin-dependent enzyme methylcrotonyl-coenzyme A carboxylase and might reflect biotin status. OBJECTIVE We sought to determine whether the plasma concentration of 3HIA-carnitine increases significantly in marginal biotin deficiency. DESIGN We experimentally induced marginal, asymptomatic biotin deficiency in 10 healthy adults (8 women) by having the subjects consume undenatured egg white for 28 d; biotin status was then repleted. Plasma concentrations of 3HIA-carnitine were measured on days 0, 14, 28, 35, and 50 by liquid chromatography-mass spectroscopy. RESULTS The mean plasma 3HIA-carnitine concentration increased with depletion (P < 0.0001) and decreased with repletion (P < 0.0001). Plasma 3HIA-carnitine concentrations were greater than the upper limit of normal concentrations in 7 of 10 subjects by day 14 and in 9 of 10 subjects by day 28 and decreased to within normal limits in 9 of 10 subjects by day 50. CONCLUSIONS These studies provide evidence that 3HIA-carnitine is an early and sensitive indicator of marginal biotin deficiency. The ease of sample collection, small sample volume requirement, and stability of 3HIA-carnitine during storage suggest that plasma 3HIA-carnitine concentration is likely to be a useful indicator of marginal biotin deficiency for larger population studies.

Lymphocyte propionyl-CoA carboxylase and its activation by biotin are sensitive indicators of marginal biotin deficiency in humans

BACKGROUND Marginal biotin deficiency may be a human teratogen. A biotin status indicator that is not dependent on renal function may be useful in studies of biotin status during pregnancy. A previous study of experimental biotin deficiency suggested that propionyl-coenzyme A carboxylase (PCC) activity in peripheral blood lymphocytes (PBLs) is a sensitive indicator of biotin status. OBJECTIVE We examined the utility of measuring PCC activity and the activation of PCC by biotin in detecting marginal biotin deficiency. DESIGN Marginal biotin deficiency was induced in 7 adults (3 women) by egg-white feeding for 28 d. Blood and urine were obtained on days 0, 14, and 28 (depletion phase) and 44 and 65 (repletion phase). PBLs were incubated with (activated) or without (control) biotin before PCC assay. The activation coefficient of PCC is the ratio of PCC activity in activated PBLs to that in control PBLs. The significance of differences for all measurements was tested by repeated-measures analysis of variance with Fishers post hoc test and Bonferroni correction. RESULTS Changes in the urinary excretion of biotin and of 3-hydroxyisovaleric acid confirmed that marginal biotin deficiency was successfully induced. By day 14, PCC activity had decreased (P < 0.0001) to below the lower limit of normal in all subjects. By day 28, the activation coefficient of PCC had increased significantly (P = 0.003) and was above the upper limit of normal in 6 of 7 subjects. CONCLUSION PCC activity is the most sensitive indicator of biotin status tested to date. In future pregnancy studies, the use of lymphocyte PCC activity data should prove valuable in the assessment of biotin status.

Investigation of an outbreak of gram-negative bacteremia among hematology-oncology outpatients.

OBJECTIVE To identify risk factors associated with an outbreak of gram-negative bacteremia (GNB). SETTING A university hospital. PATIENTS Hematology-oncology outpatients. DESIGN Retrospective case-control study. RESULTS Thirty-eight patients developed GNB; 13 patients experienced more than one episode, and eight blood cultures grew more than one gram-negative organism. The most frequently isolated organisms were Stenotrophomonas maltophilia, Klebsiella pneumoniae, Acinetobacter baumannii, and Acinetobacter johnsonii. When the GNB patients (cases) were compared with randomly selected hematology-oncology patients (controls), central venous catheter (CVC) self-care (71% vs 39%; P=.02), and duration of recent hospital stay (median, 15 vs 4 days; P=.01) were identified as risk factors. In a logistic regression model, duration of recent hospital stay was the only risk factor significantly associated with GNB (odds ratio, 1.05; 95% confidence interval, 1.01-1.08; P<.02). CONCLUSIONS Hematology-oncology patients providing their own CVC care who have recently been hospitalized for more than 2 weeks may be at increased risk of GNB. CVCs should be protected from possible environmental contamination in hematologyoncology patients. Patients providing their own CVC care should undergo continued rigorous education regarding proper CVC care.

Urinary Excretion of 3-Hydroxyisovaleric Acid and 3-Hydroxyisovaleryl Carnitine Increases in Response to a Leucine Challenge in Marginally Biotin-Deficient Humans

Experimentally increasing metabolic flux in a pathway in which an essential step is catalyzed by a vitamin-dependent enzyme (a challenge test) has been used in assessing functional vitamin status and elucidating common and alternate metabolic pathways. Conversion of 3-methylcrotonyl CoA to 3-methylglutaconyl CoA in the leucine catabolic pathway is catalyzed by the biotin-dependent enzyme methylcrotonyl-CoA carboxylase (MCC). Marginal biotin deficiency reduces MCC activity and increases urinary excretion of 3-hydroxyisovaleric acid (3HIA) and 3-hydroxyisovaleryl carnitine (3HIA-carnitine) measured in 24-h urine collections. We assessed urinary excretion of 3HIA and 3HIA-carnitine in response to a leucine challenge in humans made progressively biotin deficient by egg white consumption. In 2 cohorts of healthy adults (Study 1: n = 5; Study 2: n = 7) rendered biotin deficient over 28 d, urinary excretion of 3HIA and 3HIA-carnitine in response to a leucine challenge was quantitated weekly for 3 or 4 wk, respectively. In both studies, mean urinary excretion of both 3HIA and 3HIA-carnitine increased >2-fold by d 14 (P < 0.002 for both indicators for both studies). Diagnostically, both indicators were highly sensitive, but diagnostic sensitivities were not superior to those of 24-h excretion of 3HIA and 3HIA-carnitine. These studies provide evidence that urinary excretions of 3HIA and 3HIA-carnitine in response to an oral leucine challenge are early and sensitive indicators of marginal biotin deficiency in humans. The variability of the proportion of leucine catabolites excreted as 3HIA suggests substantial population heterogeneity in the metabolic capacity of the 3HIA-carnitine detoxification pathway.

Quantitative Measurement of Plasma 3-Hydroxyisovaleryl Carnitine by LC-MS/MS as a Novel Biomarker of Biotin Status in Humans

An increased plasma concentration of 3-hydroxyisovaleryl carnitine (3HIA-carnitine) results from impairment in the leucine catabolic pathway at the conversion of 3-methylcrotonyl-CoA to 3-methylglutaconyl-CoA. The impairment is caused by reduced activity of the biotin-dependent enzyme 3-methylcrotonyl-CoA carboxylase. Here, we describe an LC-MS/MS method for the quantitation of 3HIA-carnitine in plasma and present preliminary evidence validating plasma 3HIA-carnitine as a novel biomarker of biotin deficiency in humans. Three healthy adult subjects were successfully made marginally biotin deficient by feeding of a 30% egg-white diet for 28 days. For each subject, the plasma 3HIA-carnitine increased approximately 3-fold from Study Day 0 to Study Day 28 (p = 0.027). These results indicate that plasma 3HIA-carnitine concentration increases with biotin deficiency. If these results are confirmed in larger studies, plasma 3HIA-carnitine is likely to be an important indicator of biotin status in a variety of clinical circumstances because quantitation of 3HIA-carnitine by this method has several technical advantages over existing validated indicators of biotin status in humans.

Urinary Excretion of 3-Hydroxyisovaleryl Carnitine Is an Early and Sensitive Indicator of Marginal Biotin Deficiency in Humans

Mounting evidence indicates that marginal biotin deficiency is not rare, contrary to previous assumptions. Accordingly, robust indicators of biotin status would be useful. In a study of 10 healthy adults, we recently provided evidence that abnormally increased plasma concentration of 3-hydroxyisovaleryl carnitine (3HIA-carnitine) is a sensitive indicator of marginal biotin deficiency. We sought to determine whether urinary excretion of 3HIA-carnitine (expressed as the ratio to urinary creatinine) significantly increases in marginal biotin deficiency. Marginal, asymptomatic biotin deficiency was induced experimentally in the same 10 healthy adults (8 women) by feeding undenatured egg white with meals for 28 d. Biotin status was repleted by a mixed general diet plus biotin supplementation. Urinary excretion of 3HIA-carnitine was determined by liquid chromatography-tandem MS on d 0, 14, and 28 (depletion) and on d 35 and 50 (repletion). Mean urinary 3HIA-carnitine concentration increased with depletion (P < 0.0001; d 0 vs. 28) and decreased with repletion (P = 0.0002; d 28 vs. 50). Urinary 3HIA-carnitine excretion was greater than the upper limit of normal in 9 of 10 participants by d 14 and decreased to within normal limits by d 50 in all participants. This study provides evidence that urinary excretion of 3HIA-carnitine is an early and sensitive indicator of marginal biotin deficiency. The ease of collection of untimed urine samples and application of a new analytical method with simplified sample preparation suggest that urinary 3HIA-carnitine is likely to be a useful indicator for large population studies.

Quantitative Measurement of Urinary Excretion of 3-Hydroxyisovaleryl Carnitine by LC–MS/MS as an Indicator of Biotin Status in Humans

Abnormally increased urinary excretion of 3-hydroxyisovaleryl carnitine (3HIA-carnitine) results from impairment in leucine catabolism caused by reduced activity of the biotin-dependent enzyme 3-methylcrotonyl-CoA carboxylase. Accordingly, urinary 3HIA-carnitine might reflect biotin status. Here, we describe an LC-MS/MS method for accurately quantitating the urinary concentration of 3HIA-carnitine at concentrations that are typical for excretion rates that are normal or only modestly increased. This method allows for high sample throughput and does not require solid-phase extraction. We used this method to provide evidence validating urinary 3HIA-carnitine as a biomarker of biotin deficiency in humans. Four healthy adult subjects were successfully made marginally biotin deficient by feeding a 30% egg white diet for 28 days. From study day 0 to 28, the mean urinary excretion of 3HIA-carnitine increased 3.5-fold (p = 0.026). These preliminary results indicate that urinary excretion of 3HIA-carnitine increases with marginal biotin deficiency. If these results are confirmed in studies involving larger numbers of subjects, urinary excretion of 3HIA-carnitine may potentially be a clinically useful indicator of biotin status.