An alternative regimen for root canal disinfection.

OBJECTIVE: To compare the effect of a combination of 20% citric acid solution and photo-activated disinfection with the use of 20% citric acid and 2.25% sodium hypochlorite solutions on bacterial load on the dentine walls in prepared canals in vivo. SUBJECTS AND METHODS: Sixty-four randomly selected cases were evaluated and allocated to one of two groups. In Group 1, after gaining access to the root canal, bacterial load on the canal walls was sampled using endodontic files. A further sample was taken after apex location and initial widening of the canal had been completed and the photo-activated disinfection process carried out. A final sample was taken after completion of the canal preparation using citric acid and sodium hypochlorite solutions. In Group 2, the initial sample was taken as described previously. A second sample was taken after conventional preparation using 20% citric acid and sodium hypochlorite solutions as co-irrigants. A final sample was then taken after a subsequent PAD treatment. All samples were cultured for facultative anaerobic bacteria. RESULTS: Of the canals treated in Group 1 only two of the 23 canals infected showed culturable bacteria after the use of citric acid and photo-activated disinfection. Of these two canals, one was free of culturable bacteria on completion of conventional treatment but the other still contained culturable bacteria. In Group 2, four canals of the 23 infected initially, remained contaminated after conventional treatment. After subsequent photo-activated disinfection three of these four canals were free of culturable bacteria. CONCLUSION: Results indicate that the use of a chelating agent acting as a cleaner and disrupter of the biofilm and photo-activated disinfection to kill bacteria is an effective alternative to the use of hypochlorite as a root canal cleaning system.

Microbiological evaluation of photo-activated disinfection in endodontics (an in vivo study).

OBJECTIVE: To determine the microbiological effect of photoactivated disinfection (PAD) as an adjunct to normal root canal disinfection in vivo. DESIGN: A randomised trial carried out in general dental practice. SUBJECTS AND METHODS: Patients presenting with symptoms of irreversible pulpitis or periradicular periodontitis requiring endodontic therapy were selected at random. A microbiological sample of the canal was taken on accessing the canal, after conventional endodontic therapy, and finally after the PAD process (photosensitiser and light) had been carried out on the prepared canal. All three samples from each canal were plated within 30 minutes of sampling and cultured anaerobically for five days. Growth of viable bacteria was recorded for each sample to determine bacterial load. RESULTS: Thirty of the 32 canals were included in the results. Cultures from the remaining two did not reach the laboratory within the target time during which viability was sustained. Of the remaining 30, 10 canals were negative to culture. These were either one of the canals in multi rooted teeth where the others were infected or where a pre-treatment with a poly-antibiotic paste had been applied to hyperaemic vital tissue. Sixteen of the remainder were negative to culture after conventional endodontic therapy. Three of the four which had remained infected cultured negative after the PAD process. In the one canal where culturable bacteria were still present, a review of the light delivery system showed a fracture in the fibre reducing the effective light output by 90%. CONCLUSIONS: The PAD system offers a means of destroying bacteria remaining after using conventional irrigants in endodontic therapy.

The detection of non-O157 E. coli in food by immunomagnetic separation.

AIMS: To compare immunomagnetic separation (IMS) protocols (enrichment media and temperature) for the isolation of Escherichia coli serotypes O26 and O111 from four different foods. METHODS AND RESULTS: Foods (minced beef, cheese, apple juice and pepperoni) spiked with low numbers (<100 g(-1)) of stressed nalidixic mutant E. coli serotypes O26 and O111 were enriched in media based on buffered peptone water (BPW), tryptone soya and EC broths incubated at temperatures of 37 and 42 degrees C to optimize the IMS technique. BPW enrichments gave increased recoveries of both serotypes compared with tryptone soya and EC broths. Elevated temperatures of incubation at 42 degrees C were superior to 37 degrees C. CONCLUSIONS: Positive detection of low numbers of stressed target pathogens in all replicate tests was only possible using BPW enrichments. The majority of tests from alternative enrichments resulted in zero or single colonies recovered post-IMS. SIGNIFICANCE AND IMPACT OF THE STUDY: The optimum IMS protocol would improve isolation rates of E. coli O26 and O111 from foods and lead to increased safety for the consumer. Sub-optimal IMS protocols could lead to foods being incorrectly labelled free from these pathogens.

DNA strand breaks, oxidative damage, and 1-OH pyrene in roofers with coal-tar pitch dust and/or asphalt fume exposure.

OBJECTIVE: To determine the potential for asphalt fume exposure to increase DNA damage, we conducted a cross-sectional study of roofers involved in the application of roofing asphalt. METHODS: DNA strand breaks and the ratio of 8-hydroxydeoxyguanosine (8-OHdG) to 2-deoxyguanosine (dG) were measured in peripheral blood leukocytes of roofers. In addition, urinary excretion of 8-OHdG and 8-epi-prostaglandin F2alpha (8-epi-PGF) was also measured. The study population consisted of 26 roofers exposed to roofing asphalt and 15 construction workers not exposed to asphalt during the past 5 years. A subset of asphalt roofers (n = 19) was exposed to coal-tar pitch dust (coal tar) during removal of existing roofs prior to applying hot asphalt. Personal air monitoring was performed for one work-week to measure exposure to total particulates, benzene-soluble fraction of total particulates, and polycyclic aromatic compounds (PACs). Urinary 1-OH-pyrene levels were measured as an internal biomarker of PAC exposure. RESULTS: Full-shift breathing zone measurements for total particulates, benzene-solubles and PACs were significantly higher for coal-tar exposed workers than for roofers not exposed to coal tar. Similarly, urinary 1-OH-pyrene levels were higher in coal-tar exposed roofers than roofers not exposed to coal tar. Total particulates or benzene-soluble fractions were not associated with urinary 1-OH-pyrene, but PAC exposure was highly correlated with urinary 1-OH-pyrene. When stratified by 1-OH-pyrene excretion, DNA strand breaks increased in a dose-dependent manner, and leukocyte 8-OHdG/dG decreased in a dose-dependent manner. Significant changes in DNA damage appeared to be linked to PACs from coal-tar exposure, although asphalt fume alone was associated with a small but significant increase in urinary 1-OH-pyrene and DNA strand breaks. CONCLUSIONS: Results are consistent with previous reports that asphalt or coal-tar exposure can cause DNA damage. Urinary 8-epi-PGF remained relatively constant during the week for virtually all subjects, regardless of exposure indicating that neither asphalt nor coal-tar exposure induces an overt oxidative stress. A small, but statistically significant increase in 8OHdG was evident in end-of-week urine samples compared with start-of-week urine samples in roofers exposed to coal-tar. The increase in urinary 8OHdG coupled with the decrease in leukocyte 8-OHdG/dG, suggests that coal-tar exposure induces protective or repair mechanisms that result in reduced levels of steady-state oxidative-DNA damage.

An outbreak of E. coli O157 infection with evidence of spread from animals to man through contamination of a private water supply.

An outbreak of E. coli O157 infection occurred in the Highland Region of Scotland in the summer of 1999. The source of the outbreak was traced to an untreated private water supply. All six cases identified arose in visitors to the area, and most had very limited exposure to the contaminated water. Permanent residents on the same supply were unaffected. The E. coli O157 isolates from the water, sheep faeces collected from around the source and the human stool samples were indistinguishable using pulsed field gel electrophoresis. Previously reported outbreaks of E. coli O157 linked to potable water supplies have resulted from structural or treatment failures, which allowed faecal contamination of source water. Here, contamination of the water supply and subsequent human infection was due to the use of an untreated, unprotected private water source in a rural area where animals grazed freely.

Neurologic function among termiticide applicators exposed to chlorpyrifos.

Chlorpyrifos is a moderately toxic organophosphate pesticide. Houses and lawns in the United States receive a total of approximately 20 million annual chlorpyrifos treatments, and 82% of U.S. adults have detectable levels of a chlorpyrifos metabolite (3,5, 6-trichloro-2-pyridinol; TCP) in the urine. The U.S. Environmental Protection Agency has estimated that there are 5,000 yearly reported cases of accidental chlorpyrifos poisoning, and approximately one-fourth of these cases exhibit symptoms. Organophosphates affect the nervous system, but there are few epidemiologic data on chlorpyrifos neurotoxicity. We studied neurologic function in 191 current and former termiticide applicators who had an average of 2.4 years applying chlorpyrifos and 2.5 years applying other pesticides, and we compared them to 189 nonexposed controls. The average urinary TCP level for 65 recently exposed applicators was 629.5 microg/L, as compared to 4.5 microg/L for the general U.S. population. The exposed group did not differ significantly from the nonexposed group for any test in the clinical examination. Few significant differences were found in nerve conduction velocity, arm/hand tremor, vibrotactile sensitivity, vision, smell, visual/motor skills, or neurobehavioral skills. The exposed group did not perform as well as the nonexposed group in pegboard turning tests and some postural sway tests. The exposed subjects also reported significantly more symptoms, including memory problems, emotional states, fatigue, and loss of muscle strength; our more quantitative tests may not have been adequate to detect these symptoms. Eight men who reported past chlorpyrifos poisoning had a pattern of low performance on a number of tests, which is consistent with prior reports of chronic effects of organophosphate poisoning. Overall, the lack of exposure effects on the clinical examination was reassuring. The findings for self-reported symptoms raise some concern, as does the finding of low performance for those reporting prior poisoning. Although this was a relatively large study based on a well-defined target population, the workers we studied may not be representative of all exposed workers, and caution should be exercised in generalizing our results.

Acute hepatitis B in two patients transmitted from an e antigen negative cardiothoracic surgeon.

Hepatitis B virus (HBV) infection was transmitted by a locum cardiothoracic surgeon to two patients during coronary artery bypass surgery. Both patients presented 12 weeks after surgery and developed serious clinical illness. The surgeon was known to be hepatitis B surface antigen (HBsAg) positive, hepatitis B e antigen (HBeAg) negative, and to have antibodies to HBeAg (anti-HBe). Sequences of regions of the HBV surface and core genes from the patients and surgeon were indistinguishable. An exercise was undertaken to notify all patients on whom the surgeon had operated while employed at the hospital where the transmissions occurred. One hundred and twenty-three out of 126 patients were tested. No evidence of transmission to any other patient was found. Revised recommendations by the UK Health Departments as to which health care workers should be permitted to perform exposure prone procedures have recently been published.

O(6)-methylguanine DNA adducts associated with occupational nitrosamine exposure.

Occupational nitrosamine exposures from a rubber vehicle seal (VS) curing operation were compared with the peripheral blood lymphocyte concentrations of two nitrosamine-related DNA adducts, N(7)-methylguanine (N(7)mdG) and O(6)-methylguanine (O(6)mdG), and with the activity of the enzyme that repairs O(6)mdG adducts, O(6)-alkylguanine-DNA alkyltransferase (AGT). The occupational personal breathing zone (PBZ) nitrosamine exposures ranged from 0.4 to 9.3 microg/m(3) in the VS area, from 0.1-2 microg/m(3) in an area remote from the VS and were not detected at a nearby rubber plant. Workers from all three of these locations had detectable concentrations of N(7)mdG adducts, ranging from 0.1 to 133.2 adducts/10(7) deoxyguanosine nucleosides. Although N(7)mdG concentrations were elevated for those who worked in the VS area (median 3.60 compared with 1.44), the difference was not statistically significant after controlling for confounding factors. The O(6)mdG adduct concentrations were much lower than those of N(7)mdG, ranging from non-detectable to 12.7 O(6)mdG adducts/10(7) deoxyguanosine nucleosides and many of the participants (40/78 successfully analyzed) did not have detectable amounts of these adducts (limit of detection 0.03 O(6)mdG adducts/10(7) deoxyguanosine nucleosides). Analysis of the ordinal exposure categories (high, medium/high, medium/low, low and no exposure) yielded a statistically significant association with having detectable O(6)mdG adducts (Kendall's taub = -0.253, asymptotic SE = 0.096). There was no significant association between AGT activity and nitrosamine exposure or exposure category (P > 0.30). Although no association was found between PBZ exposure and either the N(7)mdG adduct concentrations or AGT activity, the significant positive association between working in and near the VS department and the presence of O(6)mdG adducts, which have mutagenic potential, provides evidence to link nitrosamine exposure one step closer to human cancer by demonstrating an association between external nitrosamine exposures and cancer-related biological effects.

Direct detection of Histoplasma capsulatum in soil suspensions by two-stage PCR.

Histoplasmosis is the most common pulmonary mycosis in the United States. The responsible fungal pathogen, Histoplasma capsulatum, grows in soils contaminated with bird or bat droppings. Inhalation of dust from contaminated areas containing H. capsulatum spores is a primary route of infection. The ability to detect H. capsulatum in soil samples has been limited by the lack of fast, reliable and inexpensive methods. A polymerase chain reaction (PCR) method was developed that allows the direct detection of H. capsulatum in soil. A two-stage PCR protocol was followed employing both fungal-specific primers and nested primers specific for the internal transcribed spacer (ITS) region of the 5.8S rRNA gene of H. capsulatum. The estimated limit of detection of this method is 10 spores. In contrast to the more expensive and indirect mouse inoculum assay, which requires 6-8 weeks for sample analysis, PCR analysis of soil contaminated with H. capsulatum can be completed in less than 2 days.

Raw egg ingestion and salmonellosis in body builders.

Four patients with Salmonella enteritidis infection are reported. All were body builders who regularly consumed substantial quantities of raw eggs. They presented with a severe febrile illness and diarrhoea--presumably reflecting a large bacterial inoculum. Advice regarding the potential hazards of raw egg ingestion has been repeatedly issued by the Department of Health--but this report highlights the fact that this practice continues in spite of this. The epidemiology of S. enteritidis infection in relation to raw egg ingestion is discussed.

Mutagenicity of N-OH-MOCA (4-amino-4'-hydroxylamino-bis-3,3'-dichlorodiphenylmethane) and PBQ (2-phenyl-1,4-benzoquinone) in human lymphoblastoid cells.

The genotoxic potential of two occupationally significant chemicals, 4,4'-methylene-bis-2-chloroaniline (MOCA) and 2-phenyl-1,4-benzoquinone (PBQ), was explored by monitoring the induction of mutations at the HPRT locus of AHH-1 human lymphoblastoid cells. Exposure of AHH-1 cells to the putative carcinogenic metabolite of MOCA, N-OH-MOCA, induced a 6-fold increase in mutant frequency and resulted in base pair substitutions primarily at A:T base pairs. In contrast, exposure to PBQ did not result in an increased mutant frequency although this compound was significantly more cytotoxic than N-OH-MOCA at equimolar doses. The induction of mutations at A:T sites by N-OH-MOCA is consistent with the type of DNA damage known to be produced by MOCA and provides a specific marker of genotoxic damage for exposed populations.

Determination of 4,4'-methylene-bis(2-chloroaniline)-DNA adduct formation in rat liver and human uroepithelial cells by the 32P postlabeling assay.

The probable human carcinogen 4,4'-methylene-bis(2-chloroaniline) (MOCA) was utilized to develop biomarkers of exposure to occupational carcinogens. The 32P postlabeling assay, utilizing the nuclease P1 enhancement procedure, was used to evaluate MOCA-DNA adduct formation in target tissues. Male Sprague-Dawley rats were treated with different dosing regimens of MOCA, and DNA was isolated from the liver. Additionally, a human uroepithelial cell (HUC) line was treated with N-hydroxy-MOCA for 24 hr, cells were harvested, and DNA was isolated. DNA was analyzed for MOCA-DNA adduct formation by the 32P postlabeling assay. Five MOCA adducts were detected in rat liver DNA. Adduct A, which corresponded to N-(deoxyadenosin-8-yl)-4-amino-3-chlorobenzyl alcohol, was the major adduct in rat liver DNA appearing in all treatment groups. Levels of adduct A were higher when MOCA was administered by ip injection versus oral gavage. Phenobarbital pretreatment increased the amount of adduct A approximately 12-fold. The pathway leading to the formation of adduct A in DNA from HUC appeared to be saturated at the concentrations used: 2.5, 5, and 10 microM. However, an additional adduct (E) was observed at the 10 microM treatment level only. A major DNA adduct was detected in the target tissue of rats and target human cells for MOCA-induced carcinogenesis, thus making it useful as a biomarker of exposure. Other DNA adducts were also observed with the different doses and routes of exposure investigated.

Community-acquired toxigenic Clostridium difficile diarrhoea in the normoxaemic elderly who have received no antimicrobials: soft evidence for ischaemic colitis?

We report three examples of community-acquired toxigenic Clostridium difficile diarrhoea in elderly patients who had neither received antimicrobial therapy nor been institutionalised. These cases stimulated interest in the non-antimicrobial changes which might predispose the host to C. difficile-related disease and raised the spectre of bowel ischaemia as a possible aetiological factor.

Phenoxymethyl penicillin versus co-amoxiclav in the treatment of acute streptococcal pharyngitis, and the role of beta-lactamase activity in saliva.

One hundred and sixty-five consecutive patients ( > 2 years of age) with acute group A streptococcal (GAS) pharyngitis randomly received co-amoxyclav (79 patients) or phenoxymethyl penicillin (86 patients). beta-Lactamase activity in saliva was determined for each patient. At follow up after seven days, tonsillar cultures from seven patients (9.6%) in the penicillin V group grew group A streptococcus; three of these patients had tonsillitis clinically. In the co-amoxiclav group these figures were three (3.8%) and two respectively (P > 0.05). Within the 12 month follow up period, there were four clinical recurrences (6.1%) in the penicillin V group and seven (9.3%) in the co-amoxiclav group (P > 0.1). beta-Lactamase activity in the saliva was demonstrated in 29 patients (19.2%). Fourteen (74%) of 19 bacteriological failures or clinical recurrences had beta-lactamase activity, versus 15 (12%) of 129 successfully treated patients (P < 0.001). There is no evidence that oral co-amoxiclav is better than oral penicillin V for the first treatment of acute GAS pharyngitis, but bacteriological failure and clinical recurrence are strongly associated with the presence of beta-lactamase activity in commensal flora.

A prospective randomised study of the effects of prophylactic antibiotics on the incidence of bacteraemia following hysteroscopic surgery.

OBJECTIVE: To study the effect of prophylactic antibiotics on the incidence of bacteraemia following hysteroscopic surgery. DESIGN: Prospective randomized study. SETTING: Aberdeen Royal Infirmary. SUBJECTS: One hundred and sixteen women about to undergo either endometrial laser ablation (ELA) or transcervical resection of the endometrium (TCRE). INTERVENTION: Fifty-five women were randomised to receive 1.2 g of Augmentin (co-amoxiclav) i.v. at induction of anaesthesia. Sixty-one women received no antibiotic prophylaxis. Blood cultures were obtained at the end of the surgical procedure. RESULTS: Incidence of bacteraemia in the non-antibiotic group (16%) was significantly higher than that in the antibiotic group (2%) (95% confidence interval for difference from 5% to 25%). The majority of organisms were of dubious clinical significance and contamination could not be excluded in 7 cases out of 10. CONCLUSION: There is no convincing evidence that antibiotics are of value in this clinical setting.

High incidence of haemorrhagic colitis due to Escherichia coli O157 in one Scottish town: clinical and epidemiological features.

Verotoxin-producing strains of Escherichia coli (VTEC), in particular serotype O157:H7, are now recognised as the major cause of haemorrhagic colitis and the haemolytic uraemic syndrome (HUS) in the U.K. and in North America, and increasingly so in other countries. Over a 3-year period (1989-1991), 16 cases of E. coli 0157 infection occurred in one town (Peterhead) in north-east Grampian. Four patients required admission to hospital, of whom three developed HUS. The bovine source of VTEC infection has now been clearly established with foodborne, waterborne, person-to-person and zoonotic transmission described. Despite extensive local enquiries, the source(s) of infection of the 16 cases in Peterhead was not established. Much still needs to be learned about the epidemiology, risk factors and long-term clinical sequelae of VTEC infection and HUS. Close collaboration between the medical and veterinary professions is of paramount importance in order to provide better understanding of the prevalence of E. coli O157 infection in cattle and the route(s) of transmission to humans.

Penetration of amoxycillin/clavulanic acid into bronchial mucosa with different dosing regimens.

BACKGROUND: The efficacy of an antibiotic is related to its concentration at the site of infection. Previous studies of the concentrations of amoxycillin and clavulanic acid (co-amoxiclav) in respiratory secretions or whole lung tissue have suffered from methodological problems. The concentration of amoxycillin and clavulanic acid was determined in bronchial mucosal biopsy samples obtained at bronchoscopy following five different dosing regimens. METHODS: Bronchial biopsy and serum samples were obtained from 50 patients undergoing diagnostic bronchoscopy. Ten patients each received 375 mg, 625 mg, 750 mg, and 3.25 g oral, and 1.2 g intravenous co-amoxiclav 1-3 hours before bronchoscopy. The concentrations of clavulanic acid and amoxycillin were determined by high performance liquid chromatography using a microbore column, solid phase extraction, and preconcentration to improve sensitivity tenfold over previous methods. RESULTS: Concentrations of both clavulanic acid and amoxycillin in bronchial mucosa were dose related and were well above the MIC90 of co-amoxiclav for the common bacterial respiratory pathogens including Haemophilus influenzae, Micrococcus catarrhalis and Streptococcus pneumoniae for all dosing regimens. Mean mucosal levels were 200% and 118% of the corresponding serum levels for amoxycillin and clavulanic acid respectively. CONCLUSIONS: Amoxycillin and clavulanic acid are concentrated in bronchial mucosa and, even at the lowest dose of 375 mg orally, are likely to produce tissue levels in the lung sufficient to inhibit all the common community acquired respiratory pathogens.

An analysis of 900 consecutive admissions to a regional infection unit.

A total of 900 consecutive admissions to the Regional Infection Unit at the City Hospital Aberdeen in 1991 have been analysed and the results compared with a similar study during 1980 and 1981. The annual number of admissions increased from 605 to 900, of which 72% in 1991 had proven infections compared with 60% a decade earlier. More patients were admitted with gastroenteritis, tonsillitis and soft tissue infection in 1991 and fewer with non-infectious jaundice. HIV-related conditions contributed 4% of the admissions and 29% of the mortality. Brucellosis disappeared as a reason for requesting hospital admission in North East Scotland.

Mutagenesis by metal-induced oxygen radicals.

To assess the contribution of reactive oxygen species (ROS) to metal-induced mutagenesis, we have determined the spectrum of mutations in the lacZ alpha gene after exposure of M13mp2 DNA to Fe2+, Cu2+, and Ni2+. With iron and copper ions, mutations are clustered and are predominantly single-base substitutions. Fe, Cu, and phorbol ester-stimulated neutrophils also produced tandem double CC-->TT mutations. This mutation may provide a marker for the role of oxidative damage in carcinogenesis. Mutagenesis by Ni2+ required the complexing of the metal to a tripeptide and the addition of H2O2. To assess the contribution of ROS in mammalian cells, we determined the spectrum of mutations produced when purified DNA polymerases-alpha and -beta synthesized DNA using a template that had been damaged by ROS. The mutation spectra produced by the two polymerases indicates that these enzymes substitute different nucleotides opposite the same lesions.