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.

Mutagenic specificity of oxygen radicals produced by human leukemia cells.

An important source of endogenous oxygen radicals are phagocytic cells such as neutrophils and macrophages. The human leukemia cell line HL-60 can be induced to differentiate into a neutrophil-like cell population. Among the properties of these differentiated cells is the ability to produce reactive oxygen species when stimulated by tumor promoters. Mutagenesis induced by HL-60-generated free radicals was assessed using the M13mp2 forward mutation assay. Single-stranded M13mp2 DNA was coincubated with phorbol ester-stimulated HL-60 cells, after which mutations were scored by transfecting the DNA into SOS-induced Escherichia coli. The mutation frequency was increased 6-fold above background in DNA incubated with HL-60 cells. The majority of the mutations were single-base substitutions. However, approximately 6% of the mutations were tandem double substitutions that occurred in runs of adjacent cytidines. Overall, the mutations were clustered at apparent "hot spots," many of which were similar to sites seen using iron to generate oxygen radicals. These results suggest that human cells able to produce oxygen radicals in response to tumor promoters might play a significant role in the generation of tumors.

Reactive oxygen species in tumorigenesis.

In this review we will summarize recent data on reactive oxygen species-induced mutagenesis and consider its relationship to tumorigenesis in humans. With the use of a single-stranded DNA template it has been possible to correlate oxygen radical-induced chemical alterations at specific nucleotides with the types of mutations that occur when these altered bases are copied by DNA polymerases. This has allowed us to identify the types of mutations that occur secondary to a variety of oxidative stresses and study several of the mechanisms by which they arise. The most frequent mutations that result from reactive oxygen species-induced damage to DNA in bacteria are C to T transitions. These mutations, however, are not pathoneumonic for mutagenesis by oxygen-free radicals since they result from DNA damage caused by other genotoxic agents as well as by DNA polymerase errors. One type of mutation, a tandem CC to TT double substitution, has been shown to be induced by reactive oxygen species generated by a variety of systems and may be diagnostic for such damage. In studies with mammalian DNA polymerases, DNA damaged by reactive oxygen species yields mutations different from those observed in Escherichia coli. This diversity of mutagenic changes in these in vitro studies highlights the role of DNA replicating enzymes in specifying the types of mutations produced by reactive oxygen species. In conclusion, we will consider the role of reactive oxygen species in the pathogenesis of three common tumors, carcinoma of the liver, lung, and prostate with consideration on the possible use of antioxidant preventive therapy to slow tumorigenesis sufficiently to prevent clinical presentation of these cancers during the life span of a patient.

Nickel induces a signature mutation for oxygen free radical damage.

We have determined the specificity of mutations produced by nickel(II), a known human carcinogen, in a forward mutation assay and also used a sensitive reversion assay to show that Ni(II), like iron and copper, can produce tandem double CC-->TT mutations, a hallmark of damage to DNA by either UV irradiation or oxygen free radicals. A reduction in mutation frequencies by the addition of oxygen radical scavengers also supports the involvement of reactive oxygen species in DNA damage and mutagenesis by Ni(II). Mutagenesis by Ni(II) is enhanced by the addition of both hydrogen peroxide and a tripeptide glycyl-glycyl-L-histidine. The enhancement of mutagenesis of Ni(II) by the tripeptide indicates that these complexes could serve to localize Ni(II) in nuclei and mediate DNA damage and mutagenesis via the generation of short-lived oxygen free radicals. These data suggest that Ni(II) carcinogenesis may proceed via the generation of active oxygen species and furthermore provide a model for nickel carcinogenesis based on the binding of Ni(II) to nuclear proteins.

Amino acid losses in ileostomy fluid on a protein-free diet.

The contribution of losses via the gastrointestinal tract to maintenance amino acid requirements was assessed by collecting the ileostomy fluid of volunteers given a protein-free diet for 5 d. The subjects were eight adult men and women with terminal ileum ileostomies after ulcerative colitis. Four consecutive 24-h collections of both digesta and urine were made. On the last 2 d an antibiotic was given that suppressed microbial activity in the digesta and slightly reduced ileostomy outflow. Mean daily amino acid excretion in ileostomy fluid ranged from 32 mg/d for methionine to approximately 330 mg/d for aspartate and glutamate. These losses were compared with current international estimates of amino acid requirements. For most essential amino acids gastrointestinal losses accounted for 14-33% of daily maintenance requirements but for threonine the contribution was 61%.

Clinical efficacy, tolerance and pharmacokinetics of temocillin in patients with respiratory tract infections.

In this study 13 patients with a history of chronic respiratory disease were treated with temocillin for severe infection of the lower respiratory tract. Eleven patients were clinically improved or cured at the end of treatment and 4 remained free of infection at follow up. However, the 2 remaining patients failed to respond clinically and bacteriologically to temocillin. Blood and sputum pharmacokinetics were studied in patients receiving temocillin at 12-hourly intervals in doses of either 1g by intravenous bolus or 2g by intravenous infusion. On the first day of treatment the mean peak serum concentration was 102 mg/L for the 1g dose and 220 mg/L for the 2g dose, falling to 11 mg/L (1g) and 18.8 mg/L (2g) at 12 hours. Similar results were recorded on the last day of treatment. Temocillin concentrations in the sputum ranged from 1.5 to 2.8 mg/L, with no difference being found in the sputum concentrations of the 2 doses. Temocillin was well tolerated and was found to be an effective treatment for Gram-negative bacterial infections of the lower respiratory tract.

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.

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.

Aztreonam selective agar for gram positive bacteria.

Aztreonam blood agar, a new selective medium for Gram positive aerobic bacteria, was evaluated in comparison with conventional media for skin swabs. Aztreonam agar increased the number of isolates of Staphylococcus aureus by 17%. By producing purer growths on primary isolation, it significantly speeded up the identification and sensitivity testing of staphylococci and streptococci. All major Gram positive aerobic pathogens grow on this medium. Aztreonam agar is now an established addition to our culture media. It is used for swabs which are likely to have a mixed Gram positive and Gram negative flora, such as ears, burns, ulcers, and for the sputa of patients with cystic fibrosis.

Clinical and pathological variability of infection by enterohaemorrhagic (Vero cytotoxin producing) Escherichia coli.

The clinical and pathological features of five sporadic cases of enteric infection caused by Escherichia coli O157 (enterohaemorrhagic or Vero cytotoxin-producing E coli showed a range of features. These included one case with pseudomembranous colitis, one with an acute exacerbation of ulcerative colitis, and three with enterocolitis. Diagnostic difficulties encountered initially in four of the five cases were finally resolved by correlating the results of microbiological with histopathological investigations. In view of the heterogeneity of clinical and histological signs and symptoms, it is concluded that all patients with abdominal pain and diarrhoea or rectal bleeding should have early microbiological investigation.

Familial cold urticaria. Investigation of a family and response to stanozolol.

BACKGROUND: Familial cold urticaria is a rare cutaneous and systemic reaction to cold with autosomal dominant inheritance, distinctive clinical features, and unknown pathogenesis. Release of a chymotrypsinlike substance has been postulated. To date, no effective treatment has been reported. OBSERVATIONS: Eight cases from a large family pedigree are described. Three members showed a very favorable response in their cold urticaria, when treated with stanozolol; the response was reproducible. Histologic examination of an early lesion in one case revealed evidence of mast cell degranulation. CONCLUSIONS: The biochemical observations are probably secondary epiphenomena. Correction of a deficiency of an inhibitory protein is a possible mechanism of action of stanozolol as in hereditary angioedema.

Antibiotic prophylaxis in non-perforated appendicitis of childhood: tetracycline lavage compared with peroperative intravenous cefuroxime and metronidazole.

Eighty-four cases of non-perforated appendicitis in children were randomly allocated to receive either oxytetracycline lavage alone or oxytetracycline lavage plus peroperative intravenous metronidazole and cefuroxime. The wound infection rate with the oxytetracycline lavage alone was 4.4% compared with 7.7% when metronidazole and cefuroxime were added. These rates were not significantly different. This study supports the use of oxytetracycline lavage alone as effective prophylaxis against wound infection in non-perforated appendicitis of childhood.

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.

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.

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.

Effect of DNA-repair enzymes on mutagenesis by oxygen free radicals.

Cytosine to thymine transitions are among the most common types of mutations produced by oxygen damage to DNA. One possible mechanism for these transitions is deamination of cytosine to uracil. Using both a forward mutation assay as well as a reversion assay specific for damage to cytosines we show that direct deamination to uracil does not play a significant role in mutagenesis induced by reactive oxygen free radicals. In contrast, lesions sensitive to repair by E. coli endonuclease III play a major role in oxidative mutagenesis as evidenced by the ability of endonuclease III to modulate the extent of mutagenesis that results from exposure of DNA to oxygen free radicals.

Conversion of Congo red and 2-azoxyfluorene to mutagens following in vitro reduction by whole-cell rat cecal bacteria.

Congo red, an azo dye derived from benzidine, and 2-azoxyfluorene, a derivative of 2-aminofluorene, were reduced during overnight incubation with a suspension of rat intestinal bacteria. High performance liquid chromatography and ultraviolet spectral analysis verified the presence of benzidine in extracts of the Congo red incubations and 2-aminofluorene in extracts of the 2-azoxyfluorene incubations. Extracts of the Congo red incubations were mutagenic toward Salmonella typhimurium TA1538 in the presence of a post-mitochondrial activating system, but Congo red was not mutagenic without this reductive pretreatment. Thus, the utility of the Ames test in screening for potential mutagens may be expanded by a reductive pretreatment utilizing cecal bacteria.

An open study of teicoplanin in the treatment of gram-positive infections.

Teicoplanin, a new glycopeptide antibiotic similar to vancomycin, was evaluated in treating 36 hospitalized patients suffering from various Gram-positive infections. The 36 patients received teicoplanin once daily as a mean intravenous injection of 550 mg/day (range 200-800 mg/day). Previous antimicrobial therapy was used in 28% of patients. The mean duration of therapy was 7.5 days (range 3-38 days). The overall clinical success rate was 94%. 24/36 patients (66%) had positive microbiology. Elimination of the pathogens was seen in 75% of all evaluable cases. Four patients with early prosthetic valve endocarditis due to coagulase negative Staphylococcus (3 patients) and Propionibacterium acnes (1 patient) had a favorable clinical and microbiological outcome. No adverse drug reactions were observed. Teicoplanin is safe and effective in the therapy of many different infections caused by Gram-positive bacteria.

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.