Cross-reactivity of the IDEXX Legiolert method with other Gram-negative bacteria and waterborne pathogens leads to false-positive assay results.

Legionella species are the causative agent of Legionnaires' disease, a potentially fatal bacterial pneumonia. New regulations and standards have prioritized the development of water safety plans to minimize the growth and spread of Legionella species in buildings. To determine the presence and type of Legionella in a water system, microbiological culturing is the gold standard method. However, recently new methodologies have been developed that claim to be sensitive and specific for Legionella at the genus or L. pneumophila at the species level. Published and anecdotal reports suggest that one of these newer culture-based, enzyme-substrate methods, the IDEXX Legiolert test, may exhibit false positivity with other microbes common to water sources. We experimentally evaluated the IDEXX Legiolert method using these other waterborne bacteria including Elizabethkingia meningoseptica, Pseudomonas aeruginosa, Proteus mirabilis and Serratia marcescens at real-world environmental concentrations. We saw false-positive results for the Legiolert test with several of these organisms, at sample concentrations as low as 60 CFU per ml. False-positive Legionella results can trigger costly remediation and water-use restrictions, that may be implemented while waiting for additional, confirmatory microbiological testing that could, in this case, yield no L. pneumophila.

Thrombocytopenia in liver transplant recipients: predictors, impact on fungal infections, and role of endogenous thrombopoietin.

BACKGROUND: Thrombocytopenia is a frequent and potentially serious complication in liver transplant recipients. The role of endogenous thrombopoietin level in posttransplant thrombocytopenia, has not been fully defined in liver transplant recipients. Additionally, there is accumulating evidence to suggest that platelets play a important role in antimicrobial host defense. METHODS: There were 50 consecutive liver transplant recipients studied. Variables predictive of thrombocytopenia, its impact on infectious morbidity and outcome, and serial thrombopoietin (TPO) serum concentration were assessed. RESULTS: The median pretransplant platelet count was 67 x 10(3)/cmm. After the liver transplantation, the median nadir platelet count was 33 x 10(3)/cmm and was reached a mean of 6 days after the transplant. A lower pretransplant platelet count (r= +.068, P=.0001), lower serum albumin before the transplants (r=+0.39, P=.014), longer operation time (r=0.27, P=.05), higher intraoperative packed red cells (r=0.28, P=.049) and fresh frozen plasma transfusions (r=0.42, P=.004), higher bilirubin at Day 7 (r=-.386, P=.005), and higher serum creatinine at Day 7 after the transplants (r=-.031, P=.025) correlated significantly with a lower nadir in platelets after the transplant. Nadir in platelet count was significantly lower in nonsurvivors compared with survivors (16 vs. 36 x 10(3)/cmm, P=.0001). Forty-three percent (9 of 21) of the patients with nadir platelet counts of < or =30 x 10(3)/cmm had a major infection within 30 days of the transplant compared with 17% (5 of 29) with nadir platelet counts > 30 x 10(3)/cmm (P=.04). Fungal infections occurred in 14% of the patients with nadir platelet counts of < or =30 x 10(3)/cmm versus 0% in those with nadir platelet counts of > 30 x 10(3)/cmm (P=.06); all patients with fungal infections had nadir platelet counts of < or =30 x 10(3)/cmm before fungal infection. Nadir in platelet count preceded the first major infection by a median of 7 days. Pretransplant TPO level did not differ between survivors (mean 103 pg/ml) or nonsurvivors (mean 144 pg/ml). After the transplantation, TPO levels increased in both groups. TPO level peaked at Day 7 and subsequently declined in survivors. Nonsurvivors had persistent thrombocytopenia despite a progressive rise in TPO level; TPO level was significantly higher at Day 7 (P=.02), Day 9 (P=.0019), and Day 14 (P=.04) in nonsurvivors compared with survivors. CONCLUSION: Persistent thrombocytopenia portended a poor outcome in liver transplant recipients and was not related to low TPO levels. Thrombocytopenia preceded infections and identified a subgroup of liver transplant patients susceptible to early major infections; its precise role in fungal infections warrants validation in larger studies.

Efficacy of thermal treatment and copper-silver ionization for controlling Legionella pneumophila in high-volume hot water plumbing systems in hospitals.

BACKGROUND: Thermal treatment and copper-silver ionization are often used for controlling Legionella pneumophila in high-volume hospital plumbing systems, although the comparative efficacies of these measures in high-volume systems are unknown. METHODS: Thermal treatment of a hot water circuit was accomplished by flushing hot water (> 60 degrees C) through distal fixtures for 10 minutes. Copper-silver ionization was conducted in three circuits by installing units into return lines immediately upstream from hot water tanks. Recovery rates of L. pneumophila were monitored by culturing swab samples from faucets. Concentrations of copper and silver in water samples were determined by atomic absorption spectrophotometry. RESULTS: Four heat-flush treatments failed to provide long-term control of L. pneumophila. In contrast, ionization treatment reduced the rate of recovery of L. pneumophila from 108 faucets from 72% to 2% within 1 month and maintained effective control for at least 22 months. Only three samples (1.9%) of hot water from faucets exceeded Environmental Protection Agency standards for silver, and none exceeded the standards for copper. Of 24 samples obtained from hot water tanks, 42% and 50% exceeded the silver and copper standards, respectively. CONCLUSIONS: Copper-silver ionization effectively controls L. pneumophila in high-volume plumbing systems and is superior to thermal treatment; however, high concentrations of copper and silver can accumulate at the bottom of hot water tanks.

Effect of experimental influenza A virus infection on isolation of Streptococcus pneumoniae and other aerobic bacteria from the oropharynges of allergic and nonallergic adult subjects.

Intranasal challenge with both influenza A virus and Streptococcus pneumoniae promotes otitis media with S. pneumoniae in chinchillas. We investigated whether influenza A virus infection promotes oropharyngeal colonization with S. pneumoniae and other middle ear pathogens by selectively inhibiting commensal bacteria. On study day 0, 12 allergic and 15 nonallergic adult subjects were intranasally inoculated with influenza A/Kawasaki (H1N1) virus. Every subject was infected with the virus as demonstrated by nasal shedding or seroconversion. Average upper respiratory symptom scores and nasal secretion weights from the entire subject group were elevated between days 2 and 6 (acute phase) and were not significantly different between allergic and nonallergic subjects. S. pneumoniae was not isolated from any subject prior to the virus challenge but was isolated in heavy density from 4 (15%) subjects on day 6 (P = 0.055). Staphylococcus aureus was isolated more frequently from the nonallergic subjects than from the allergic subjects on days 2 (80 versus 25%, respectively) 4, (67 versus 17%, respectively), and 6 (73 versus 25%, respectively) (P < 0.05). The isolation rates of other middle ear pathogens were not significantly different before virus challenge and during the acute and resolution phases (days 27 to 30) of the experimental infection for the entire subject group or either the allergic or nonallergic subgroup. Densities and isolation rates of commensal bacteria from the entire subject group were similar throughout the observational period. These results suggest that the virus infection promoted S. pneumoniae colonization of the oropharynx and that nonallergic persons may be more vulnerable to colonization with S. aureus than allergic persons. The altered colonization rates were not attributed to inhibition of commensal bacteria.

Oscillation-frequency and baseline fetal heart rate in the last 30 minutes of labour.

The last 120 minutes of 394 intrapartum fetal heart rate (FHR) records of high technical quality were evaluated. Baseline FHR was estimated and oscillation frequency (OF) counted for each minute. There was a highly significant association between the baseline FHR and the number of oscillations/minute; an increase in baseline FHR of 10 beats/minute was associated with a fall of about one oscillation/minute. The highest mean OF (9.6 +/- 4.8 events/minute) was found in fetuses with an umbilical artery pH of between 7.20 and 7.25. The baseline FHR should be taken into account when assessing fetal condition.