Biomedical subjects

B S Fields

Publications and source records attributed to B S Fields.

At least 19 recordsLinked to original sources

PubMed2006

Increased rainfall is associated with increased risk for legionellosis.

Legionnaires' disease (LD) is caused by Legionella species, most of which live in water. The Mid-Atlantic region experienced a sharp rise in LD in 2003 coinciding with a period of record-breaking rainfall. To investigate a possible relationship, we analysed the association between monthly legionellosis incidence and monthly rainfall totals from January 1990 to December 2003 in five Mid-Atlantic states. Using negative binomial model a 1-cm increase in rainfall was associated with a 2.6% (RR 1.026, 95% CI 1.012-1.040) increase in legionellosis incidence. The average monthly rainfall from May to September 1990-2002 was 10.4 cm compared to 15.7 cm from May to September 2003. This change in rainfall corresponds to an increased risk for legionellosis of approximately 14.6% (RR 1.146, 95% CI 1.067-1.231). Legionellosis incidence increased during periods of increased rainfall; identification of mechanisms that increase exposure and transmission of Legionella during rainfall might lead to opportunities for prevention.

Adult↗

PubMed2001

Pontiac fever due to Legionella micdadei from a whirlpool spa: possible role of bacterial endotoxin.

During January 1998, a cluster of illnesses occurred among hotel guests in Wisconsin. Ill persons had been exposed to the hotel's whirlpool spa and swimming pool. Symptoms included headache, fever, chills, myalgia, shortness of breath, and fatigue. A diagnosis of Pontiac fever was made, based on serologic evidence of acute infection with Legionella micdadei. High concentrations of heterotrophic bacteria were recovered from the spa, despite apparently high disinfectant levels. L. micdadei was isolated from the swimming pool filter and water from the spa after heat enrichment but not from pools and spas at nearby hotels. Water from hotel pools and spas was tested to determine endotoxin levels; water from the spa of the implicated hotel contained the highest concentration of endotoxin (14,400 endotoxin units/mL). Additional studies are needed to determine the role of endotoxin from legionellae or other bacteria in the pathogenesis of Pontiac fever.

Antibodies, Bacterial↗

PubMed2001

Standardizing Chlamydia pneumoniae assays: recommendations from the Centers for Disease Control and Prevention (USA) and the Laboratory Centre for Disease Control (Canada).

Chlamydia pneumoniae has been associated with atherosclerosis and several other chronic diseases, but reports from different laboratories are highly variable and "gold standards" are lacking, which has led to calls for more standardized approaches to diagnostic testing. Using leading researchers in the field, we reviewed the available approaches to serological testing, culture, DNA amplification, and tissue diagnostics to make specific recommendations. With regard to serological testing, only use of microimmunofluorescence is recommended, standardized definitions for "acute infection" and "past exposure" are proposed, and the use of single immunoglobulin (Ig) G titers for determining acute infection and IgA for determining chronic infection are discouraged. Confirmation of a positive culture result requires propagation of the isolate or confirmation by use of polymerase chain reaction (PCR). Four of 18 PCR assays described in published reports met the proposed validation criteria. More consistent use of control antibodies and tissues and improvement in skill at identifying staining artifacts are necessary to avoid false-positive results of immunohistochemical staining. These standards should be applied in future investigations and periodically modified as indicated.

Bacteriological Techniques↗

PubMed2001

Legionella drozanskii sp. nov., Legionella rowbothamii sp. nov. and Legionella fallonii sp. nov.: three unusual new Legionella species.

Seven strains of Legionella-like amoebal pathogens (LLAPs) were characterized on the basis of their cultural and staining characteristics, biochemical reactions, serology, cellular fatty acids (CFAs), isoprenoid quinone composition, total DNA relatedness, analysis of 16S rRNA and macrophage infectivity potentiator (mip) gene sequence analyses. All seven strains exhibited limited growth on buffered charcoal yeast extract alpha (BCYE) agar, required cysteine for growth and contained branched-chain CFAs and quinones typical of Legionella species. The bacilli were Gram-negative and catalase-positive. There were varying degrees of serological cross-reactions between these LLAP strains and other previously described Legionella species. Results from the various tests revealed that four LLAP strains represent three unusual new species of Legionella: Legionella drozanskii sp. nov., type strain LLAP-1T; Legionella rowbothamii sp. nov., type strain LLAP-6T; and Legionella fallonii sp. nov., type strain LLAP-10T. Three other LLAP strains, designated LLAP-7FL, LLAP-7NF and LLAP-9, were shown to be members of the species Legionella lytica. The deductions made from the phenetic characteristics of these bacteria were consistent with the phylogenetic relationships inferred from 16S rRNA and mip gene sequence analyses. This study is the first to speciate LLAP strains on the basis of data including quantitative DNA hybridization.

Acanthamoeba↗

PubMed2001

Role of biofilms in the survival of Legionella pneumophila in a model potable-water system.

Legionellae can infect and multiply intracellularly in both human phagocytic cells and protozoa. Growth of legionellae in the absence of protozoa has been documented only on complex laboratory media. The hypothesis upon which this study was based was that biofilm matrices, known to provide a habitat and a gradient of nutrients, might allow the survival and multiplication of legionellae outside a host cell. This study determined whether Legionella pneumophila can colonize and grow in biofilms with and without an association with Hartmannella vermiformis. The laboratory model used a rotating disc reactor at a retention time of 6.7 h to grow biofilms on stainless steel coupons. The biofilm was composed of Pseudomonas aeruginosa, Klebsiella pneumoniae and a Flavobacterium sp. The levels of L. pneumophila cells present in the biofilm were monitored for 15 d, with and without the presence of H. vermiformis, and it was found that, although unable to replicate in the absence of H. vermiformis, L. pneumophila was able to persist.

Animals↗

PubMed2000

Potential importance of Legionella species as etiologies in community acquired pneumonia (CAP).

Large percentages of patients with community acquired pneumonia (CAP) do not have a defined etiology. Between 1992-1993, 99 acute and convalescent sera were collected from patients with CAP of unknown etiology. The sera were tested using an indirect immunofluorescence antibody assay (IFA) against the following antigens: Legionella pneumophila, serogroups 3,5,6 and 7 and L. longbeachae, L. anisa, L. bozemanii and Legionella-Like Amoebal Pathogens (LLAP). A four-fold rise in titer to at least one of the antigens tested, was seen in 14% of patients; 8% to L. bozemanii, 4% to L. anisa, 2% to S. lyticum, 2% to LLAP 10 and 1% each to LLAP 1, 6 and 9. Two patients reacted to several antigens. These results indicate that other species of legionella may be important in the etiology of CAP. L. bozemanii was the organism identified in the majority of these infections. Better diagnostic studies i.e. cultures, serologies and urinary antigen testing, which recognize legionella isolates other than L. pneumophila serogroup 1 need to be developed.

Antigens, Bacterial↗

PubMed2000

Strengths and limitations of molecular subtyping in a community outbreak of Legionnaires' disease.

An epidemiological and microbiological investigation of a cluster of eight cases of Legionnaires' disease in Los Angeles County in November 1997 yielded conflicting results. The epidemiological part of the investigation implicated one of several mobile cooling towers used by a film studio in the centre of the outbreak area. However, water sampled from these cooling towers contained L. pneumophila serogroup 1 of another subtype than the strain that was recovered from case-patients in the outbreak. Samples from two cooling towers located downwind from all of the case-patients contained a Legionella strain that was indistinguishable from the outbreak strain by four subtyping techniques (AP-PCR, PFGE, MAb, and MLEE). It is unlikely that these cooling towers were the source of infection for all the case-patients, and they were not associated with risk of disease in the case-control study. The outbreak strain also was not distinguishable, by three subtyping techniques (AP-PCR, PFGE, and MAb), from a L. pneumophila strain that had caused an outbreak in Providence, RI, in 1993. Laboratory cross-contamination was unlikely because the initial subtyping was done in different laboratories. In this investigation, microbiology was helpful for distinguishing the outbreak cluster from unrelated cases of Legionnaires' disease occurring elsewhere. However, multiple subtyping techniques failed to distinguish environmental sources that were probably not associated with the outbreak. Persons investigating Legionnaires' disease outbreaks should be aware that microbiological subtyping does not always identify a source with absolute certainty.

Adult↗

PubMed2000

Lack of association between Kawasaki syndrome and Chlamydia pneumoniae infection: an investigation of a Kawasaki syndrome cluster in San Diego County.

BACKGROUND: The etiology of Kawasaki syndrome (KS), the leading cause of acquired coronary artery disease in children, is unknown. Recent studies have suggested that Chlamydia pneumoniae, a common respiratory pathogen associated with an increased risk of heart disease, might lead to KS. OBJECTIVE: To assess whether KS was associated with an elevated risk of having a current or antecedent infection with C. pneumoniae. METHODS: Blood, urine and pharyngeal specimens from KS patients in San Diego County, CA, during a period of high KS incidence were analyzed for evidence of recent C. pneumoniae infection by culture, PCR and serology. Specimens collected from two control groups, family members of KS patients and age-matched children attending outpatient clinics for well child visits, were similarly analyzed. RESULTS: Thirteen cases were identified. Forty-five outpatient controls and an average of three family members per patient were enrolled in the study. All specimens tested negative for the presence of C. pneumoniae by PCR and culture except for one blood specimen from the mother of a case-patient. Serologic analysis of patients and a subset of outpatient and family controls revealed no evidence of current C. pneumoniae infection; 4 of 13 adult family controls had IgG titers consistent with past exposure to C. pneumoniae. Case patients were no more likely than outpatient controls to have had a respiratory illness in the preceding 2 months (11 of 13 patients vs. 35 of 45 controls; odds ratio, 1.57; 95% confidence interval, 0.3 to 11.9). CONCLUSIONS: We found no evidence that C. pneumoniae infection was associated with KS.

Adolescent↗

PubMed2000

Evaluation of the Binax and Biotest urinary antigen kits for detection of Legionnaires' disease due to multiple serogroups and species of Legionella.

The Binax and the Biotest urinary antigen kits for the detection of Legionnaires' disease caused by organisms other than Legionella pneumophila were compared by testing 45 urine samples from non-Legionella pneumophila serogroup 1 patients previously positive in a broad-spectrum enzyme-linked immunosorbent assay (ELISA). Eighteen were positive with the Binax kit, and 13 were positive with the Biotest. Although neither kit is as sensitive as ELISA, these results extend the number of serogroups and species of Legionella that can be diagnosed with the Binax or Biotest kit.

Antigens, Bacterial↗

PubMed1999

Effect of monochloramine disinfection of municipal drinking water on risk of nosocomial Legionnaires' disease.

BACKGROUND: Many Legionella infections are acquired through inhalation or aspiration of drinking water. Although about 25% of municipalities in the USA use monochloramine for disinfection of drinking water, the effect of monochloramine on the occurrence of Legionnaires' disease has never been studied. METHODS: We used a case-control study to compare disinfection methods for drinking water supplied to 32 hospitals that had had outbreaks of Legionnaires' disease with the disinfection method for water supplied to 48 control-hospitals, with control for selected hospital characteristics and water treatment factors. FINDINGS: Hospitals supplied with drinking water containing free chlorine as a residual disinfectant were more likely to have a reported outbreak of Legionnaires' disease than those that used water with monochloramine as a residual disinfectant (odds ratio 10.2 [95% CI 1.4-460]). This result suggests that 90% of outbreaks associated with drinking water might not have occurred if monochloramine had been used instead of free chlorine for residual disinfection (attributable proportion 0.90 [0.29-1.00]). INTERPRETATION: The protective effect of monochloramine against legionella should be confirmed by other studies. Chloramination of drinking water may be a cost-effective method for control of Legionnaires' disease at the municipal level or in individual hospitals, and widespread implementation could prevent thousands of cases.

Case-Control Studies↗

PubMed1999

Hospital characteristics associated with colonization of water systems by Legionella and risk of nosocomial legionnaires' disease: a cohort study of 15 hospitals.

OBJECTIVE: To investigate an increase in reports of legionnaires' disease by multiple hospitals in San Antonio, Texas, and to study risk factors for nosocomial transmission of legionnaires' disease and determinants for Legionella colonization of hospital hot-water systems. SETTING: The 16 largest hospitals in the cities of San Antonio, Temple, and Austin, Texas. DESIGN: Review of laboratory databases to identify patients with legionnaires' disease in the 3 years prior to the investigation and to determine the number of diagnostic tests for Legionella performed; measurement of hot-water temperature and chlorine concentration and culture of potable water for Legionella. Exact univariate calculations, Poisson regression, and linear regression were used to determine factors associated with water-system colonization and transmission of Legionella. RESULTS: Twelve cases of nosocomial legionnaires' disease were identified; eight of these occurred in 1996. The rise in cases occurred shortly after physicians started requesting Legionella urinary antigen tests. Hospitals that frequently used Legionella urinary antigen tests tended to detect more cases of legionnaires' disease. Legionella was isolated from the water systems of 11 of 12 hospitals in San Antonio; the 12th had just experienced an outbreak of legionnaires' disease and had implemented control measures. Nosocomial legionellosis cases probably occurred in 5 hospitals. The number of nosocomial legionnaires' disease cases in each hospital correlated better with the proportion of water-system sites that tested positive for Legionella (P=.07) than with the concentration of Legionella bacteria in water samples (P=.23). Hospitals in municipalities where the water treatment plant used monochloramine as a residual disinfectant (n=4) and the hospital that had implemented control measures were Legionella-free. The hot-water systems of all other hospitals (n=11) were colonized with Legionella. These were all supplied with municipal drinking water that contained free chlorine as a residual disinfectant. In these contaminated hospitals, the proportion of sites testing positive was inversely correlated with free residual chlorine concentration (P=.01). In all hospitals, hot-water temperatures were too low to inhibit Legionella growth. CONCLUSIONS: The increase in reporting of nosocomial legionnaires' disease was attributable to increased use of urinary antigen tests; prior cases may have gone unrecognized. Risk of legionnaires' disease in hospital patients was better predicted by the proportion of water-system sites testing positive for Legionella than by the measured concentration of Legionella bacteria. Use of monochloramine by municipalities for residual drinking water disinfection may help prevent legionnaires' disease.

Cohort Studies↗

PubMed1999

A community outbreak of Legionnaires' disease linked to hospital cooling towers: an epidemiological method to calculate dose of exposure.

BACKGROUND: From July to September 1994, 29 cases of community-acquired Legionnaires' disease (LD) were reported in Delaware. The authors conducted an investigation to a) identify the source of the outbreak and risk factors for developing Legionella pneumophila serogroup 1 (Lp-1) pneumonia and b) evaluate the risk associated with the components of cumulative exposure to the source (i.e. distance from the source, frequency of exposure, and duration of exposure). METHODS: A case-control study matched 21 patients to three controls per case by known risk factors for acquiring LD. Controls were selected from patients who attended the same clinic as the respective case-patients. Water samples taken at the hospital, from eight nearby cooling towers, and from four of the patient's homes were cultured for Legionella. Isolates were subtyped using monoclonal antibody (Mab) analysis and arbitrarily primed polymerase chain reaction (AP-PCR). RESULTS: Eleven (52%) of 21 case-patients worked at or visited the hospital compared with 17 (27%) of 63 controls (OR 5.0, 95% CI : 1.1-29). For those who lived, worked, or visited within 4 square miles of the hospital, the risk of illness decreased by 20% for each 0.10 mile from the hospital; it increased by 80% for each visit to the hospital; and it increased by 8% for each hour spent within 0.125 miles of the hospital. Lp-1 was isolated from three patients and both hospital cooling towers. Based on laboratory results no other samples contained Lp-1. The clinical and main-tower isolates all demonstrated Mab pattern 1,2,5,6. AP-PCR matched the main-tower samples with those from two case-patients. CONCLUSION: The results of our investigation suggested that the hospital cooling towers were the source of a community outbreak of LD. Increasing proximity to and frequency of exposure to the towers increased the risk of LD. New guidelines for cooling tower maintenance are needed. Knowing the location of cooling towers could facilitate maintenance inspections and outbreak investigations.

Adult↗

PubMed1999

Optimizing culture of Chlamydia pneumoniae by using multiple centrifugations.

Three methods for the recovery of Chlamydia pneumoniae from spiked nasopharyngeal and blood specimens, including extended culture and additional centrifugations, were compared. Additional centrifugations and a 7-day culture time resulted in a 500- to 5, 000-fold increase in the number of detectable inclusion-forming units.

Cells, Cultured↗

PubMed1998

Epidemic Legionnaires' disease two decades later: old sources, new diagnostic methods.

In July 1995 we investigated a pneumonia outbreak in a Pennsylvania town. We conducted epidemiological and molecular microbiological studies to determine the outbreak source and interrupt transmission of disease. Legionnaires' disease (LD) was quickly identified by urine antigen testing, and a newly developed immunohistochemical stain confirmed nosocomial transmission to a hospital inpatient. LD was confirmed in 22 patients. Case-patients were more likely than controls to have been within 1,000 feet of the hospital (matched odds ratio, 21.0; 95% confidence interval, 2.9-368) during the 2 weeks prior to illness. Legionella pneumophila serogroup 1 (Lp-1) was isolated from hospital cooling towers (CTs) and rooftop air samples but not from hospital potable water or community CTs. Hospital CT and air Lp-1 isolates matched all five patient isolates by monoclonal antibody, arbitrarily primed polymerase chain reaction, and pulsed-field gel electrophoresis subtyping. Strategies to prevent LD must include minimizing transmission from CTs.

Adult↗

PubMed1998

Isolation of an amoeba naturally harboring a distinctive Legionella species.

There are numerous in vitro studies documenting the multiplication of Legionella species in free-living amoebae and other protozoa. It is believed that protozoa serve as host cells for the intracellular replication of certain Legionella species in a variety of environmental settings. This study describes the isolation and characterization of a bacterium initially observed within an amoeba taken from a soil sample. In the laboratory, the bacterium multiplied within and was highly pathogenic for Acanthamoeba polyphaga. Extracellular multiplication was observed on buffered charcoal yeast extract agar but not on a variety of conventional laboratory media. A 16S rRNA gene analysis placed the bacterium within the genus Legionella. Serological studies indicate that it is distinct from previously described species of the genus. This report also describes methods that should prove useful for the isolation and characterization of additional Legionella-like bacteria from free-living amoebae. In addition, the characterization of bacterial pathogens of amoebae has significant implications for understanding the ecology and identification of other unrecognized bacterial pathogens.

Amoeba↗

PubMed1998

Classification of the genus Legionella.

There are currently 42 described species of legionellae representing 64 serogroups in the family Legionellaceae and the genus Legionella. The phenotypic characteristics of legionellae are described, including growth requirements, and biochemical characteristics. Identification of legionellae by biochemical tests, fatty acid analysis, ubiquinones, protein profiles, carbohydrate analysis, serology, monoclonal antibodies, and molecular techniques is described. The occurrence and description of Legionella-like amebic pathogens are discussed. The problems of identification to the species level are discussed, along with the need for further evaluations of additional strains from all known species using biochemical and molecular techniques.

Humans↗

PubMed1998

A recurrent outbreak of nosocomial legionnaires' disease detected by urinary antigen testing: evidence for long-term colonization of a hospital plumbing system.

BACKGROUND: In 1994, a hospital reported an increase in nosocomial legionnaires' disease after implementing use of a rapid urinary antigen test for Legionella pneumophila serogroup 1 (Lp-1). This hospital was the site of a previous nosocomial legionnaires' disease outbreak during 1980 to 1982. METHODS: Infection control records were reviewed to compare rates of nosocomial pneumonia and the proportion of cases attributable to legionnaires' disease during the 1994 outbreak period with those during the same period in 1993. Water samples were collected for Legionella culture from the hospital's potable water system and cooling towers, and isolates were subtyped by monoclonal antibody (MAb) testing and arbitrarily primed polymerase chain reaction (AP-PCR). RESULTS: Nosocomial pneumonia rates were similar from April through October 1993 and April through October 1994: 5.9 and 6.6 per 1,000 admissions, respectively (rate ratio [RR], 1.1; P=.56); however, 3.2% of nosocomial pneumonias were diagnosed as legionnaires' disease in 1993, compared with 23.9% in 1994 (RR, 9.4; P<.001). In 1994, most legionnaires' disease cases were detected by the urinary antigen testing alone. MAb testing and AP-PCR demonstrated identical patterns among Lp-1 isolates recovered from a patient's respiratory secretions, the hospital potable water system, and stored potable water isolates from the 1980 to 1982 outbreak. CONCLUSIONS: There may have been persistent transmission of nosocomial legionnaires' disease at this hospital that went undiscovered for many years because there was no active surveillance for legionnaires' disease. Introduction of a rapid urinary antigen test improved case ascertainment. Legionella species can be established in colonized plumbing systems and may pose a risk for infection over prolonged periods.

Connecticut↗

PubMed1997

ELISPOT assay for Chlamydia-specific, antibody-producing cells correlated with conventional complement fixation and microimmunofluorescence.

Chlamydia antigens cross-reactive with pneumoniae (TWAR), psittaci, and trachomatis strains were used to evaluate the ELISPOT assay for detecting antigen-specific, antibody-secreting cells (ASC). Human blood specimens from healthy and hospitalized persons were randomly collected and tested by coating the nitrocellulose membrane at the base of microtiter wells. Ficoll-separated mononuclear cells from blood specimens collected in EDTA were incubated in the wells with Iscove's growth medium in CO2 atmosphere at 37 degrees C. An IgG-specific conjugate labeled with biotin was used in an avidin-peroxidase chromogen system for indicating the areas (spots) of immunologically committed lymphocytes. Positive specimens had median levels of ASC above 8 per 10(6) cells (range 15-23 ASC/10(6) cells). Evidence that the ELISPOT is reliable, sensitive, and specific includes the following:(1) immunized animal and clinical human specimens in control experiments were selectively reactive in the presence of antigen, but negative without antigen, (2) serologically characterized reference sera demonstrated homologous rather than heterologous reactions with the antigens, (3) conventional complement fixation and microimmunofluorescence on serum fractions of clinical specimens correlated well (P < 0.02) with ELISPOT results that were both TWAR- and psittaci-positive, and (4) the array of specimens (from healthy donors, community hospitalized, and pulmonary service patients) selected for their increasing likelihood in that order for being positive due to illness was then confirmed and supported by their respectively increasing positivity rates (6, 15, and 25%) for TWAR/psittaci combined. The incidence of positive specimens for either TWAR or psittaci was greatest (23/54, 43%) in specimens from the hospitalized patients and least (8/33, 24%) in specimens from healthy individuals. These findings suggest that ELISPOT detects chalmydial antibody production at the cellular level. ELISPOT positivity thus indicates previous exposure and would favor earlier detection.

Animals↗