An international outbreak of salmonellosis associated with raw almonds contaminated with a rare phage type of Salmonella enteritidis.

During the winter of 2000 to 2001, an outbreak due to Salmonella Enteritidis (SE) phage type 30 (PT30), a rare strain, was detected in Canada. The ensuing investigation involved Canadian and American public health and food regulatory agencies and an academic research laboratory. Enhanced laboratory surveillance, including phage typing and pulsed-field gel electrophoresis, was used to identify cases. Case questionnaires were administered to collect information about food and environmental exposures. A case-control study with 16 matched case-control pairs was conducted to test the hypothesis of an association between raw whole almond consumption and infection. Almond samples were collected from case homes, retail outlets, and the implicated processor, and environmental samples were collected from processing equipment and associated farms for microbiological testing. One hundred sixty-eight laboratory-confirmed cases of SE PT30 infection (157 in Canada, 11 in the United States) were identified between October 2000 and July 2001. The case-control study identified raw whole almonds as the source of infection (odds ration, 21.1; 95% confidence interval, 3.6 to infinity). SE PT30 was detected in raw whole natural almonds collected from home, retail, distribution, and warehouse sources and from environmental swabs of processing equipment and associated farmers' orchards. The frequent and prolonged recovery of this specific organism from a large agricultural area was an unexpected finding and may indicate significant diffuse contamination on these farms. Identification of almonds as the source of a foodborne outbreak is a previously undocumented finding, leading to a North American recall of this product and a review of current industry practices.

A multistate outbreak of Escherichia coli O157:H7 infections associated with consumption of mesclun lettuce.

BACKGROUND: An outbreak of Escherichia coli O157:H7 infections in Connecticut and Illinois during May 28 to June 27, 1996, was investigated to determine the source of infections. METHODS: Independent case-control studies were performed in both states. Pulsed-field gel electrophoresis (PFGE) was performed on E. coli O157:H7 isolates. A case-patient was defined as a Connecticut or northern Illinois resident with diarrhea whose stool culture yielded E. coli O157:H7 of the outbreak-associated PFGE subtype. Controls were town-, age-, and sex-matched to case-patients. We traced implicated lettuce to the farm level and performed environmental investigations to identify unsafe lettuce production practices. RESULTS: In Connecticut and Illinois, infection was associated with consumption of mesclun lettuce (Connecticut matched odds ratio [MOR], undefined; 95% confidence interval [CI], 3.4 to infinity; and Illinois MOR, undefined; 95% CI, 1.4 to infinity). We traced implicated lettuce to a single grower-processor. Cattle, a known E. coli O157:H7 reservoir, were found near the lettuce fields. Escherichia coli (an indicator of fecal contamination) was cultured from wash water and finished lettuce. A trace-forward investigation identified 3 additional states that received implicated lettuce; E. coli O157:H7 isolates from patients in 1 of these states matched the outbreak-associated PFGE subtype. CONCLUSIONS: This multistate outbreak of E. coli O157:H7 infections was associated with consumption of mesclun lettuce from a single producer. Molecular subtyping facilitated the epidemiological investigation. This investigation increased the knowledge about current production practices that may contribute to the contamination of lettuce by microbial pathogens. Lettuce production practices should be monitored for microbiological safety.

Detection of the optical bands of molybdenum(V) in DMSO reductase (Rhodobacter capsulatus) by low-temperature MCD spectroscopy.

Dimethylsulphoxide (DMSO) reductase from R. capsulatus contains a molybdenum-pterin cofactor at its active site. As prepared the molybdenum is in the 6+ oxidation state, devoid of EPR signals. Stepwise reduction generates an EPR signal characteristic of Mo(V) having hyperfine coupling to a single proton and integrating to less than 25% of the total molybdenum. The low temperature MCD spectrum shows oppositely signed bands between approximately 550-700 nm. These bands are assigned as dithiolene-to-Mo(V) charge transitions. A simple theoretical model can satisfactorily account for the bands in the MCD spectrum. No evidence is found for cysteine coordination to Mo(V).

A model of the copper centres of nitrous oxide reductase (Pseudomonas stutzeri). Evidence from optical, EPR and MCD spectroscopy.

Nitrous oxide reductase (N2OR), Pseudomonas stutzeri, catalyses the 2 electron reduction of nitrous oxide to di-nitrogen. The enzyme has 2 identical subunits (Mr approximately 70,000) of known amino acid sequence and contains approximately 4 Cu ions per subunit. By measurement of the optical absorption, electron paramagnetic resonance (EPR) and low-temperature magnetic circular dichroism (MCD) spectra of the oxidised state, a semi-reduced form and the fully reduced state of the enzyme it is shown that the enzyme contains 2 distinct copper centres of which one is assigned to an electron-transfer function, centre A, and the other to a catalytic site, centre Z. The latter is a binuclear copper centre with at least 1 cysteine ligand and cycles between oxidation levels Cu(II)/Cu(II) and Cu(II)/Cu(I) in the absence of substrate or inhibitors. The state Cu(II)/Cu(I) is enzymatically inactive. The MCD spectra provide evidence for a second form of centre Z, which may be enzymatically active, in the oxidised state of the enzyme. Centre A is structurally similar to that of CuA in bovine and bacterial cytochrome c oxidase and also contains copper ligated by cysteine. This centre may also be a binuclear copper complex.

Day-care center attendance and hospitalization for lower respiratory tract illness.

To identify risk factors associated with hospitalization for acute lower respiratory tract illness, 102 children less than 2 years of age admitted to four Atlanta metropolitan area hospitals between December 1984 and June 1985 with the diagnosis of lower respiratory tract illness were studied. The most common causative agent associated with illness was respiratory syncytial virus, followed by other respiratory viruses, Haemophilus influenzae, and Streptococcus pneumoniae. The 102 case-patients were compared with 199 age- and sex-matched controls. A parent or guardian for each patient and control was interviewed by telephone regarding demographic data, care outside the home, breast-feeding, previous medical history, allergies, and smoking and illness in household members. Five factors were associated with lower respiratory tract illness in both a univariate analysis and a multiple logistic regression model (P less than .05). These factors were the number of people sleeping in the same room with the child, a lack of immunization the month before the patient was hospitalized, prematurity, a history of allergy, and regular attendance in a day-care center (more than six children in attendance). Care received outside of the home in a day-care home (less than or equal to six children in attendance) was not associated with lower respiratory tract illness. The suggestion made by our study and other studies was that for children less than 2 years of age, care outside of the home is an important risk factor for acquiring lower respiratory tract illness, as well as other infectious diseases, and that this risk can be reduced by using a day-care home instead of a day-care center.

Alfalfa sprouts and Salmonella Kottbus infection: a multistate outbreak following inadequate seed disinfection with heat and chlorine.

Raw sprouts have been implicated in a number of foodborne disease outbreaks. Because contaminated seeds are usually responsible, many sprout producers attempt to disinfect seeds before germination and detect sprout contamination during production. In March 2001, we detected an increased number of Salmonella serotype Kottbus isolates in California. Overall, we identified 31 cases from three western states. To identify the cause, we conducted a case-control study with the first 10 identified case-patients matched to 20 controls by age, sex, and residential area. Our case-control study found illness to be statistically associated with alfalfa sprout consumption. The traceback investigation implicated a single sprouter, where environmental studies yielded Salmonella Kottbus from ungerminated seeds and floor drains within the production facility. Pulsed-field gel electrophoresis patterns of all patient, seed, and floor drain Salmonella Kottbus isolates were indistinguishable. Most implicated sprouts were from seeds that underwent heat treatment and soaking with a 2,000-ppm sodium hypochlorite solution rather than the Food and Drug Administration (FDA)-recommended 20,000-ppm calcium hypochlorite soak. Other implicated seeds had been soaked in a calcium hypochlorite solution that, when tested, measured only 11,000 ppm. The outbreak might have been averted when screening tests of sprout irrigation water detected Salmonella in January; however, confirmatory testing of these samples was negative (but testing improperly utilized refrigerated irrigation water). Producers should use the enrichment broth of positive screening samples, not refrigerated irrigation water, for confirmatory testing. Until other effective disinfection technologies are developed, producers should adhere to FDA recommendations for sprout seed disinfection.

Comparison of particle concentration fluorescence immunoassay to card and complement fixation tests using isolation of Brucella abortus as the standard.

Serologic test data and bacteriologic culture results from 816 cattle were evaluated. Brucella abortus (field strain or strain 19) was isolated from 27.3% of the cows. Results of the card test, particle concentration fluorescence immunoassay (PCFIA), and complement fixation (CF) test were compared. Antibody titers were directly associated with B. abortus isolation, with the majority (64.7%) of field strain isolations having a PCFIA value of < or = 0.300 and a CF test result of at least 1+ at a 1:160 dilution. The specificity of the CF test was significantly higher than that of the PCFIA (at CF > or = 1:40 and PCFIA < or = 0.300).

CuA and CuZ are variants of the electron transfer center in nitrous oxide reductase.

Nitrous oxide reductase (N2OR) is a dimeric copper-dependent bacterial enzyme that catalyzes the reduction of N2O to N2 as part of the denitrification pathway. In the absence of an x-ray crystal structure, the current model of the nature of the copper sites within the enzyme is based on four copper atoms per monomer and assigns two copper atoms to an electron transfer center, CuA, a bis-thiolate-bridged dinuclear copper center found to date only in N2OR and cytochrome c oxidase, and two copper atoms to a second dinuclear center, CuZ, presumed to be the site of catalysis. Based on detailed analysis of the low temperature magnetic CD spectra of N2OR, this paper revises the current model and proposes that both CuA and CuZ are variants of an electron transfer center and hence that all of the observed optical features are due to this electron transfer center. It is proposed further that the presence of these different forms provides a mechanism for the delivery of two electrons to an active site comprising copper ions lacking thiolate coordination.

Spectroscopic and mutagenesis studies on the CuA centre from the cytochrome-c oxidase complex of Paracoccus denitrificans.

Cytochrome-c oxidase contains an unusual copper centre (CuA) located in subunit II. This centre mediates one-electron transfer from cytochrome c to low-spin heme a. Recent spectroscopic and biochemical studies have shown that this centre is a valence delocalised dinuclear [Cu(+1.5)-Cu(+1.5)] centre. We have measured the absorption, EPR and variable-temperature magnetic circular dichroism spectra of the CuA-binding domain isolated from Paracoccus denitrificans cytochrome aa3. The EPR spectrum showed the following signals: gparallel = 2.18; gperpendicular = 2.03. gparallel exhibited a seven-line hyperfine splitting pattern, with an intensity ratio showing that the single unpaired electron interacted equally with two copper nuclei. The magnetic circular dichroism spectrum was identical to those from CuA in bovine heart cytochrome-c oxidase and centre A of nitrous-oxide reductase, showing the close structural similarity between the three centres. To identify the ligands of CuA, all the conserved putative ligands in the P. denitrificans CuA domain were substituted. Only five residues, Cys244, Cys248, His209, His252, and Met255, were required for correct assembly of the CuA centre. Replacement of Met255 caused protein misfolding. Hence, methionine may have a structural role for the folding of the protein rather than being a CuA ligand. Given that both copper ions must have identical coordination geometries, the number of possible structures is limited. Two models are proposed: one involves the thiolate side-chains of Cys244 and Cys248 bridging a pair of copper ions with one histidine coordinating each copper ion, and the other has terminal ligation of each copper ion by one cysteine and one histidine residue. In both models, the metal-metal distance can be sufficiently short to permit direct d-orbital overlap of the copper ions. The magnetic circular dichroism transitions at 475 nm and 525 nm are assigned to thiolate-to-copper charge-transfer processes polarised perpendicular to one another, although the magnetic circular dichroism intensities show that the excited states were heavily mixed with copper d-orbitals. These intensities can be interpreted in the thiolate bridged model in terms of transitions within a Cu2(SR)2 rhomb. In the model involving terminal cysteine ligation, exciton coupling of two thiolate-to-copper charge-transfer transitions of similar energy, polarised along the Cu-S bonds, would contribute two transitions perpendicular to one another. This requires that the cysteine ligands have a cis orientation relative to one another.(ABSTRACT TRUNCATED AT 400 WORDS)

Magnetic circular dichroism study of the selenium-substituted form (Fe3Se4) of bovine heart aconitase.

The selenium-substituted inactive form of mitochondrial aconitase contains one [3Fe-4Se]1+/0 cluster [Surerus, Kennedy, Beinert and Münck (1989) Proc. Natl. Acad. Sci. U.S.A. 87, 9846-9850]. This cluster was studied in both oxidized and reduced states by magnetic CD (MCD) and EPR spectroscopy. In the MCD spectra, intensity and transition wavelength shifts are observed when compared with the spectra of the native [3Fe-4S]1+/0 cluster. These changes are used to differentiate between the charge-transfer transitions originating from inorganic and cysteinyl sulphur. Using also the data from the EPR spectra, the spin ground state is assigned as S = 1/2 for the oxidized [3Fe-4Se]1+ cluster and S = 2 for the reduced [3Fe-4Se]0 cluster.

Magnetic and optical properties of copper-substituted alcohol dehydrogenase: a bisthiolate copper (II) complex.

Replacement of the catalytic Zn(II) in horse liver alcohol dehydrogenase (HLADH) with copper produces a mononuclear Cu(II) chromophore with a ligand set consisting of two cysteine sulphurs, one histidine nitrogen plus one further atom. The fourth ligand to the metal ion and the conformation of the protein may be altered by addition of exogenous ligands and/or the cofactor NADH. Absorbance, CD, low-temperature magnetic CD (MCD) and EPR spectra are presented of copper-substituted HLADH samples in both 'open' and 'closed' conformations and in the presence and absence of the exogenous ligands pyrazole and DMSO. The EPR spectra indicate a strong, predominantly axial field about the copper(II) ion with high copper-thiol (cysteine) covalence. The optical and MCD spectra are interpreted in terms of four d-d transitions to low energy, also reflecting the axial ligand field, and four charge-transfer transitions to copper(II) between 30000 and 16000 cm-1 arising from the two cysteine sulphur atoms which give two pairs of oppositely signed MCD C-terms. These transitions are polarized mainly in the axial plane defined by Cys-46, Cys-174 and His-67. The binary complex formed with pyrazole displays quite different EPR and optical spectra which can be understood in terms of a rotation of the copper hole-orbital away from the axial plane thus decreasing sharply the copper-thiol covalence. The magneto-optical spectra in the presence and absence of DMSO are indistinguishable.

A survey of measured levels and dietary sources of selected organochlorine pesticide residues and metabolites in human sera from a rural population.

We measured serum levels of 11 pesticide residues and metabolites in 85 rural-dwelling persons. In general, the serum levels increased with age, with males having slightly higher levels than females. Consumption of eggs from home-raised hens contributed substantially to increased serum concentrations of trans-nonachlor, heptachlor epoxide, and oxychlordane; consumption of home-grown root vegetables likewise contributed to increased serum concentrations of trans-nonachlor and oxychlordane. Health risks, if any, that may be attributable to these "background" levels of exposure remain to be fully characterized in this, and all other, affected populations.

Characterization of the prismane protein from Desulfovibrio vulgaris (Hildenborough) by low-temperature magnetic circular dichroic spectroscopy.

The prismane protein of Desulfovibrio vulgaris (Hildenborough) contains a putative [6Fe-6S] cluster. This novel iron-sulfur cluster has been characterized here by magnetic circular dichroism (MCD) spectroscopy. Three paramagnetic redox states of the cluster, [6Fe-6S]5+, [6Fe-6S]4+ and [6Fe-6S]3+, each show a distinctive low-temperature MCD spectrum which is unlike that observed for any other iron-sulfur clusters. Magnetization data for the prismane protein in these three redox states indicate ground state spins that are in accordance with previous EPR assignments. For the protein as isolated, with the [6Fe-6S]5+ form of the cluster, magnetizations show an exceptionally steep initial slope that can be fit to a ground state of spin S = 9/2. For the semi-reduced protein, the cluster in the [6Fe-6S]4+ form, magnetizations show an initial slope characteristic for a ground state of spin S = 4. For the dithionite-reduced protein, with the [6Fe-6S]3+ form of the cluster, magnetizations are typical for a ground state of spin S = 1/2.

A large outbreak of epidemic keratoconjunctivitis: problems in controlling nosocomial spread.

Between July 1985 and January 1986, 401 patients with adenovirus epidemic keratoconjunctivitis (EKC) were seen at the Illinois Eye and Ear Infirmary. Of the cases, 110 (27%) were nosocomial; the other 291 patients had community acquired infection. The highest attack rates of EKC occurred in patients attending specialty clinics; the overall attack rate among clinic patients was 4.7/1,000 clinic visits. All nosocomial cases were caused by adenovirus type 8; community acquired cases were a mixture of adenovirus types 8 and 37. Adenoviruses were isolated from conjunctival cultures up to 14 d after the onset of clinical illness. Initial efforts to prevent nosocomial transmission were unsuccessful. However, when a plan to triage all patients on entry to the infirmary and to sort patients and personnel caring for infected patients into cohorts was implemented, nosocomial transmission of EKC was promptly and effectively halted, despite the continuation of the community epidemic for another 4 mo. This outbreak clearly demonstrates the efficacy of rigorous infection control in preventing nosocomial transmission of adenovirus EKC.

Blood lead values in dogs from a rural area (Champaign, IL in 1987).

We studied 87 healthy dogs to determine background levels of blood lead in dogs living in a presumably uncontaminated environment. We took blood samples from dogs and asked their owners for information regarding behavioral risk factors related to environmental lead exposure. The mean blood lead concentration was 5 (+/- 4.4) micrograms/dl (range 0-22 micrograms/dl).

Nonfatal occupational injury among California farm operators.

We conducted a population-based telephone survey addressing farm-work-related (FWR) injuries among California farm operators. Of 1947 participants (80.4% response), 135 farm operators reported 160 FWR injuries in the preceding year, yielding a one-year cumulative incidence for any FWR injury of 6.9% (95% CI 5.8%-8.2%), or a mean 8.2 FWR injuries per 100 farmers in the preceding year (95% CI 6.8-9.7). Multiple injury events in the same individual occurred more frequently than predicted by chance. Sprains and strains (29.4%) were the most frequently reported injury and predominantly involved the back. Overexertion represented the most frequent external cause (24.2%), followed by machinery (14.3%), falls (13.0%), and animals (12.4%). Factors associated with FWR injury included white ethnicity (OR 3.19; 95% CI 1.38-7.36), increased annual hours worked on the farm, low levels of administrative work, and increased percentage of time working with livestock. FWR injury experience of California farm operators is comparable with that reported for other agricultural populations. Above-expected frequency of multiple injuries supports involvement of personal or environmental risk factors. Preventive efforts should focus on higher-risk groups and preventing overexertion and muscle strain and injury related to machinery, falls, and animals, especially livestock.

Escherichia coli O157 and Salmonella infections associated with sprouts in California, 1996-1998.

BACKGROUND: In California, from 1996 through 1998, more than 50% of multicounty outbreaks with confirmed food vehicles were related to alfalfa or clover sprouts. OBJECTIVE: To summarize investigations of sprout-associated outbreaks. DESIGN: Matched case-control studies. SETTING: California. PATIENTS: Outbreak-associated patients and matched population controls. MEASUREMENTS: Matched odds ratios and 95% CIs; traceback and environmental investigations of sprout and seed growers; and pulsed-field gel electrophoresis of isolates from patients, sprouts, and seeds. RESULTS: Five sprout-associated outbreaks of salmonellosis and one outbreak of infection with nonmotile Shiga toxin-producing Escherichia coli O157 occurred. Six hundred patients had culture-confirmed disease, and two died. It is estimated that these outbreaks caused 22 800 cases of gastrointestinal illness or urinary tract infection. In the case-control studies, odds ratios for the association between illness and alfalfa sprout consumption ranged from 5.0 to infinity (all were statistically significant). Three sprout growers were implicated, and each was associated with two outbreaks. Outbreak strains of Salmonella were isolated from sprouts supplied by two sprout growers and from seeds used by the third sprout grower. CONCLUSIONS: As currently produced, sprouts can be a hazardous food. Seeds can be contaminated before sprouting, and no method can eliminate all pathogens from seeds. Seed and sprout growers should implement measures to decrease contamination. The general public should recognize the risks of eating sprouts, and populations at high risk for complications from salmonellosis or E. coli O157 infection should avoid sprout consumption.

Evidence of an unusual pattern of polychlorinated biphenyls in the serum of some residents and canines in Paoli, Pennsylvania.

The present study uses gas liquid chromatography (GLC) electron capture detection with packed and capillary columns to detect polychlorinated biphenyls (PCBs) in serum samples from people living near the electric car repair and maintenance facility of the Southeastern Pennsylvania Transit Authority in Paoli, Pennsylvania. Most of the cohort surveyed had serum patterns similar to patterns for Aroclor 1260 (AR 1260); a small portion (3/89) had patterns indicative of an AR with higher chlorination (e.g., AR 1268). In addition to analyzing serum samples from humans, we also analyzed serum samples from canines (pets of some of the subjects). In general, the serum pattern for canines was less descriptive for AR 1260 than the pattern for humans; however, the pattern for several canines (9/16) was that of the higher chlorinated PCBs (e.g., AR 1268). By using mass spectrometry and capillary column GLC, we confirmed the presence of high molecular weight polychlorinated congeners in both human and animal samples. We were not able to show a statistically significant relationship between serum patterns of PCBs in canines and their owners or between canines and certain behavioral traits (e.g., runs free, retrieves, hours outside, hours inside). However, the correlation between PCBs quantified as AR 1268 and canines' residence time was statistically significant.