Seasonal distribution of microplastics in surface waters of the Northern Indian Ocean

Seven expeditions were carried out during pre-monsoon, monsoon and post monsoon in 2018-2019 for marine plastic collection in surface waters of Northern Indian Ocean. PE and PP (83 %) is the dominant type of polymer found in the surface waters. Colored particles account for 67 % of all particles, with fibre/line accounting for 86 %. The average (Mean ± SD) microplastics concentration in the Northern Indian Ocean during pre-monsoon is 15,200 ± 7999 no./km², Monsoon is 18,223 ± 14,725 no./km² and post monsoon is 72,381 ± 77,692 no./km². BoB during pre-monsoon and post monsoon the microplastic concentration remains same except in the northern BoB this change is caused due to weak winds. Microplastics concentration varied both spatially, temporal and heterogeneity in nature. These differences are caused by effect of wind and seasonal reversal of currents. Microplastics collected in the anticyclonic eddy are 129,000 no./km².

Seasonal temperature variability observed at abyssal depths in the Arabian Sea

The abyssal ocean is generally considered an aseasonal environment decoupled from the variabilities observed at and just below the ocean's surface. Herein, we describe the first in-situ timeseries record of seasonal warming and cooling in the Arabian Sea at a depth of 4000 m. The seasonal cycle was observed over the nearly four-year-long record (from November 2018 to March 2022). The abyssal seasonal temperature cycle also exhibited noticeable interannual variability. We investigate whether or not surface processes influence the near-seabed temperature through deep meridional overturning circulation modulated by the Indian monsoon or by Rossby wave propagation. We also consider if bottom water circulation variability and discharge of the dense Persian Gulf and Red Sea Water may contribute to the observed seasonality.

Influence of environmental factors on macrofoulant assemblages on moored buoys in the eastern Arabian Sea

Factors governing the distribution of organisms in the pelagic ocean are understudied. In this paper we describe environmental parameters and macrofouling assemblages on 11 buoys deployed in the Arabian Sea for an average duration of 322 days. Macrofoulants on all the mooring components extending from the sea-surface to a depth of 1800–4300 m were documented. Role of temperature, salinity, dissolved oxygen, biological productivity and zooplankton community in governing the macrofoulant distribution are described. Species composition, vertical zonation and wet biomass exhibited significant spatial variations. Lepas anatifera constituted more than 90% of foulant wet biomass on all moorings. Assemblages in the southeastern (SEAS), east-central (ECAS) and northeast (NEAS) regions were distinct. Density of L. anatifera on surface buoys were low in SEAS (0.2±0.09 no./cm²), high in ECAS (0.32±0.11 no./cm²) and moderate in NEAS (0.23±0.04no./cm²). Macrofoulants were observed up to a depth of 75 m in SEAS, 130 m in ECAS and 120 m in NEAS. The depth profile of macrofoulant assemblages on moorings could be related to the prevalent hypoxic condition. Vertical profiles of wet biomass on all moorings exhibited subsurface maxima at depth ranging from 10 to 20 m, consequent to the abundance of L. anatifera in a thermally stable depth of water column, wherein diurnal and semidiurnal temperature variability was minimal. We attribute the observed variation in fouling assemblages to dissolved oxygen levels, salinity and diurnal variability in temperature and salinity.

Summary of: Antibiotic prophylaxis in oral healthcare - the agreement between Swedish recommendations and evidence

Background Almost all (17/20) Swedish counties have pharmaceutical committees that establish recommendations for the use of antibiotic prophylaxis in oral healthcare.Objective To evaluate the evidence for the use of antibiotic prophylaxis in oral healthcare and the agreement between Swedish recommendations and evidence.Material and methods We conducted a systematic literature search in PubMed and the Cochrane Controlled Trials Register. The MeSH terms 'antibiotic prophylaxis' and 'dentistry' were used in the database search. Abstracts were reviewed according to specific inclusion and exclusion criteria. A total of 186 articles were read in full text by the four authors independently. Data extraction and interpretation of data was carried out using a pre-defined protocol. In the end, one case-control study was included for evaluation of evidence.Results The case-control study included patients with specific cardiac conditions. The study reported a 49% protective efficacy (odds ratio: 0.51) of antibiotic prophylaxis for first-time episodes of endocarditis within 30 days of procedure. This result was not statistically significant. The quality of the evidence was low. No studies were evaluated on patients with other medical conditions. The recommendations included several cardiac and other medical conditions for which there is a lack of evidence or no evidence to support the use of antibiotic prophylaxis.Conclusions There is a lack of evidence to support the use of antibiotic prophylaxis. To avoid the risk of adverse events from antibiotics and the risk of developing resistant bacterial strains, the use of antibiotic prophylaxis should be minimised and recommendations in Sweden should be revised to be more evidence-based.

The dimensional stability of dental impression materials following immersion in disinfecting solutions

OBJECTIVES

This investigation examined the effect of several disinfectant systems upon the dimensional stability of a range of common dental impression materials. A new disinfection process based upon hypochlorous acid was one of those examined (Sterilox).

METHODS

Test specimens of commercially available impression materials from the following categories were investigated: alginates, addition-cured silicones, condensation-cured silicones and polyether. Three disinfection regimes were tested: sodium hypochlorite 5.25%, Perform ID and Sterilox. A custom-built automatic laser micrometer was used to measure the dimensions of sample discs of the test materials before disinfection, immediately after and then following 24h storage. Analysis of variance was employed to identify statistically significant differences within groups and across groups.

RESULTS

All the disinfection routines tested resulted in acceptable levels of dimensional stability within the category of normal use of each impression material. All the materials tested can be disinfected with 10% Sterilox without undergoing unacceptable levels of dimensional change.

SIGNIFICANCE

All the disinfection routines tested resulted in acceptable levels of dimensional stability within the category of normal use of each impression material.

Quantitative trait loci linked to thalamus and cortex gray matter volumes in BXD recombinant inbred mice

To investigate whether there are separate or shared genetic influences on the development of the thalamus and cerebral cortex, we identified quantitative trait loci (QTLs) for relevant structural volumes in BXD recombinant inbred (RI) strains of mice. In 34 BXD RI strains and two parental strains (C57BL/6J and DBA/2J), we measured the volumes of the entire thalamus and cortex gray matter using point counting and Cavalieri's rule. Heritability was calculated using analysis of variance (ANOVA), and QTL analysis was carried out using WebQTL (http://www.genenetwork.org). The heritability of thalamus volume was 36%, and three suggestive QTLs for thalamus volume were identified on chromosomes 10, 11 and 16. The heritability of cortical gray matter was 43%, and four suggestive QTLs for cortex gray matter volume were identified on chromosomes 2, 8, 16 and 19. The genetic correlation between thalamus and cortex gray matter volumes was 0.64. Also, a single QTL on chromosome 16 (D16Mit100) was identified for thalamus volume, cortex gray matter volume and Morris water maze search-time preference (r=0.71). These results suggest that there are separate and shared genetic influences on the development of the thalamus and cerebral cortex.

An investigation of the decontamination of Siqveland matrix bands

OBJECTIVES

This study investigated blood contamination of artificially and clinically contaminated Siqveland matrix bands and retainers. A modified version of the recognised Kastle-Meyer test for blood was used to compare the efficacy of enzymatic agents, a washer-disinfector and an instrument washer for pre-sterilisation cleaning of Siqveland matrix bands and retainers.

METHODS

Assembled Siqveland matrix bands were contaminated either artificially with horse blood or clinically during dental treatment. Contaminated assembled matrix bands and retainers were subjected to immersion in an enzymatic agent, automated processing in a washer-disinfector or instrument washer, or a combination of pre-soaking and automatic cleaning. Residual blood contamination from each band and retainer was measured and compared to the volume of blood recovered from an unprocessed control group of contaminated assembled matrix bands or retainers.

RESULTS

Residual blood was recovered from every clinically contaminated assembled Siqveland matrix band and retainer. The volume of blood recovered from assembled Siqveland matrix bands ranged from 0.13-7.1 microl and from retainers, following removal of the matrix band, from 0.001-1.523 microl. The most effective method of pre-sterilisation cleaning for artificially contaminated assembled matrix bands was processing in the washer-disinfector. Conversely, the most effective method for cleaning clinically contaminated assembled matrix bands and retainers was pre-soaking in an enzymatic agent followed by a heavy-duty cycle in an instrument washer.

CONCLUSIONS

It is not possible to clean assembled Siqveland matrix bands using any method currently available to dental practitioners. Matrix bands should be discarded after use on one patient. Once the band is removed, all detectable blood can be removed from the retainer by pre-soaking in an enzymatic detergent followed by processing in an instrument washer.

Infective endocarditis and dentistry: the legal basis for an association

OBJECTIVES

The objectives of this study were to determine on what evidence infective endocarditis (IE) could be legally linked to dental treatment.

METHOD

The records of 319 legal cases involving dental treatment as the probable cause of IE were analysed. The medical history, type of dental operation, and whether antibiotic prophylaxis was provided were noted. The time taken for the onset of symptoms (incubation period) and hospitalisation was calculated. The identity of the infecting micro-organism was investigated and it was also noted whether litigation was successful for the patient.

RESULTS

A total of 83 patients were successful in legally linking dental treatment to the onset of infective endocarditis. In all successful cases there was a short incubation period (circa nine days) and in 80 of the patients an oral Streptococcus was isolated. The dental operations included exodontia (28), scaling (29), endodontics (12) and minor oral surgery (11).

CONCLUSIONS

Dental treatment was deemed to be the probable cause of IE in 26% of patients who sought litigation. In the majority of legal cases clinicians did not follow recognised guidelines or keep adequate clinical notes. The three main factors which link dental procedures legally were the dental operation, the isolation from the blood of an oral micro-organism and a short incubation period.

The role of selective decontamination of the digestive tract in acute stroke

BACKGROUND

following a stroke, morbidity and mortality is high, with aspiration pneumonia being a common complication.

OBJECTIVES

to determine the levels of colonisation by and isolation of aerobic Gram-negative bacteria (AGNB) in acute stroke patients and determine the effect of selective decontamination of the digestive tract (SDD) on oral flora and whether it reduces both morbidity and mortality after an acute stroke.

DESIGN

a prospective, randomised, placebo-controlled double blind trial.

SETTING

acute stroke assessment units of three hospitals in the northwest of England.

SUBJECTS

203 patients admitted to hospital following a first acute stroke.

METHODS

participants were randomised to SDD oral gel or placebo. Swallow was assessed on admission to hospital, and oral swabs were obtained thrice weekly. Demographic and clinical data were recorded.

RESULTS

203 patients (106 males and 97 females) participated, of whom 20 died during their hospitalisation, 19 withdrew and full follow-up was obtained for the remaining 164. A total of 122 AGNB were isolated in 105 samples from 48 patients. Abnormal swallow on admission was found in 58 patients (29%). A total of 34 patients carried a single gram-negative micro-organism that was present on one or more occasions. More than one AGNB was carried in 14 patients, and organisms were significantly more likely to be isolated from the placebo group than the active group during weeks 2 and 3 of treatment (P = 0.034, chi-squared). Seven patients in the placebo group and one in the treatment group developed pneumonia (P = 0.029, Fisher's exact test).

CONCLUSIONS

high carriage of and colonisation by AGNB was found within this study, which was reduced by the addition of SDD. Although SDD reduced the presence of both organisms and documented episodes of pneumonia, mortality remained unchanged.

Clindamycin and dentistry

Clindamycin is an antimicrobial agent that dentists use in the UK for infective endocarditis prophylaxis but rarely for other clinical situations that require antimicrobial intervention. This has been largely due to its association with acute pseudomembranous colitis. Up to date information on the efficacy and safety of this antimicrobial agent should be known before prescription.

Antibiotic prophylaxis and third molar surgery

The issue of prophylactic antibiotic therapy in third molar surgery is highly controversial. The current evidence questions the benefits of routine prophylactic antibiotic therapy which does not appear to overcome the risk of undesirable outcomes after third molar removal. In our opinion there is no justification for routine antibiotic prophylaxis for third molar surgery.

An investigation of the efficacy of super–oxidised (Optident/Sterilox) water for the disinfection of dental unit water lines

AIMS

To determine the efficacy of super-oxidised water (Optident/Sterilox) in the decontamination of dental unit water lines.

METHODS

Dental units (10) were first purged with concentrated super-oxidised water. After purging, a 5% (v/v) super-oxidised water was used as a maintenance dose. Samples for microbiology were taken after 0,1,2,3,4,5,6,7 d, and each week for a further 13 weeks.

RESULTS

After purging, 5% (v/v) super-oxidised water was successful in reducing the microbial counts to zero, although in three of the units some bacteria were intermittently isolated in the first week of treatment.

CONCLUSIONS

Super-oxidised water was successful in the removal of bacteria from dental unit water supplies. Complete removal required the treatment with a purge phase of concentrated disinfectant and a maintenance phase of at least two weeks.

An investigation of therapeutic antibiotic prescribing for children referred for dental general anaesthesia in three community national health service trusts

OBJECTIVE

To investigate antibiotic prescribing for paediatric dental patients requiring general anaesthesia.

DESIGN

A prospective clinical study of children referred for dental treatment under general anaesthesia.

METHOD

Information was collected by way of a two-stage questionnaire for children attending three community NHS trusts for dental extractions under general anaesthesia between July 2001 and January 2003.

RESULTS

A total of 360 questionnaires were analysed. There was wide variation in the waiting times (0-278 days) between referral and treatment under general anaesthesia. Most children (53%) attended with dento-alveolar abscess, 46% with caries only and 1% for orthodontic extractions. Antibiotics were prescribed to 52% of patients with an abscess and 32% with caries only. Only 16% of patients presented with moderate to severe pain, 5.5% with diffuse swelling and 12% with a raised temperature. Antibiotics were prescribed for patients with diffuse swelling (63%) and raised temperature (50%) but also for patients with pain only (39%) and localised swelling (52%). Amoxicillin was the most frequently prescribed antibiotic (82%), with wide variation in all antibiotic regimens.

CONCLUSION

This study provides evidence of inappropriate prescribing of antibiotics to children referred for treatment under general anaesthesia with wide variations in the regimens employed. There was no conclusive evidence that long waiting times for definitive treatment influenced antibiotic prescribing. In some areas the delay for definitive treatment for this group of vulnerable patients was unacceptably long.

A comparison of decontamination methods used for dental burs

OBJECTIVES

This study investigated the bacterial and fungal contamination of used dental burs. A novel assay system for comparison of efficacy of pre-sterilisation cleaning techniques for dental burs was used to evaluate manual scrubbing, enzymic agents and washer-disinfectors.

METHODS

Thirty dental burs contaminated during cavity preparation were analysed for micro-biological total viable counts and species of bacteria and fungi present. To simulate clinically contaminated burs, a culture of Streptococcus sanguis NCTC 7863 was used to inoculate unused dental burs, alone and combined with blood, saliva or a mixture of blood and saliva. Contaminated burs were subjected to six pre-sterilisation cleaning techniques and the log reduction in contamination achieved by each method was assessed.

RESULTS

The microbial count from used dental burs ranged from 0 to 6.92 x 10(4) CFU ml(-1). Many potentially pathogenic species were identified. The decontamination assay demonstrated that autoclaving alone was not sufficient to sterilise dental burs. Manual scrubbing in air was less efficacious than manual scrubbing under water (p<0.001). The most effective method of pre-sterilisation cleaning for dental burs was a washer-disinfector.

CONCLUSIONS

Enzymic agents are suitable for soaking contaminated dental burs immediately after use. Washer-disinfectors are recommended as the method of choice for pre-sterilisation cleaning of contaminated dental burs.

Azithromycin and dentistry - a useful agent?

OBJECTIVES

Azithromycin has recently replaced clindamycin oral suspension for prop hylaxis of infective endocarditis (IE) in children. It is also currently recommended by the American Heart Association as an alternative to penicillin, along with clindamycin for prophylaxis of infective endocarditis in adults. The objectives of this paper were to firstly, review the current literature on the efficacy of azithromycin as a suitable prophylactic agent in the prevention of infective endocarditis; and secondly, to review its pharmacological properties as a suitable therapeutic agent in the management of odontogenic infections.

DESIGN

A review of the literature.

CONCLUSIONS

The available evidence from animal models on infective endocarditis supports the efficacy of this drug as a prophylactic agent against oral streptococci. The pharmacological properties of this agent would make it a very promising therapeutic adjunct in the management of odontogenic infections. At present there are only a small number of studies available with valuable data on the efficacy of this relatively new drug. Further investigations comparing this compound with other commonly used adjuncts would be of great benefit.

Total viable counts, ATP, and endotoxin levels as potential markers of microbial contamination of dental unit water systems

OBJECTIVES

To determine if either ATP or endotoxin concentrations in water supplied by dental unit water systems (DUWS) correlated with total viable counts (TVC), and therefore could be used as a rapid, chairside measure of levels of microbial contamination.

DESIGN

A prospective trial.

METHOD

Fifty-seven water samples were taken from the 'triple spray', air rotor and source water supplies from 25 dental units in eight practices. The samples were assayed for endotoxin concentration, total ATP and TVC. A pilot study was performed to assess the relationship between TVC and total cell counts, as determined by flow cytometry.

RESULTS

ATP concentrations ranged from 22 to 958 relative light units (RLU) and free endotoxin ranged from 25 to 600 EU ml(-1). TVC varied from not detected to 2.16 x 10(4) CFU ml(-1). The ATP method proved to be a simple and rapid method that could be used at the chairside. However, there was no correlation between ATP or endotoxin concentrations and TVC in DUWS. TVC generally underestimated the total cell count by 50 to 500 fold.

CONCLUSION

Half of the water samples from DUWS exceeded recommended levels of TVC. However, ATP and endotoxin concentrations in DUWS water samples did not correlate with these TVC data and therefore could not be recommended as an alternative assay to TVC for measuring bacterial contamination or for monitoring water treatment efficacy.

Systemic antimicrobials in the treatment of chronic periodontal diseases: a dilemma

The use of systemic antimicrobials in the treatment of acute and chronic periodontal diseases must be viewed as a dilemma. On the one hand, the approach is attractive because of the microbial nature of periodontal diseases but, on the other hand, evidence of benefit of these agents is equivocal for the majority of periodontal diseases and antimicrobials have the potential to cause harm. The disadvantages of systemic antimicrobials can be grouped under the headings of allergic reactions, superinfection, toxicity, drug interactions, patient compliance and, perhaps of most widespread importance, bacterial resistance. Mechanical debridement methods, including drainage of pus for acute periodontal abscesses, should be considered the first line treatment for most periodontal diseases. Systemic antimicrobials should be considered as adjuncts to mechanical debridement methods and, in chronic disease, never used alone as they can predispose to abscess formation. Adjunctive systemic antimicrobials may be considered in acute disease where debridement or drainage of pus is difficult, where there is local spread or systemic upset. In chronic periodontal diseases, adjunctive antimicrobials should be considered in early onset or rapidly progressive disease or in advanced chronic adult disease where mechanical therapies have failed or surgery is not a preferred option. Inadequate oral hygiene and tobacco smoking are contraindications to the use of antimicrobials. The value of systemic antimicrobials, where other systemic risk factors co-exist, has still to be established. The role of microbial diagnosis and sensitivity testing for antimicrobial selection at this time must be questioned.

A study to assess the effects of a new detergent-free, olive oil formulation dentifrice in vitro and in vivo

OBJECTIVE

To determine the effects of a detergent-free dentifrice containing olive oil using in vitro microbiological tests and an in vivo plaque re-growth model.

METHOD

A total of 20 subjects took part in a double blind, single-centre, crossover study in which slurry rinses were the only form of plaque control over a 5-day period. Following a washout and prophylaxis the subjects used 2x daily rinses in the absence of all other plaque control methods. Subjects returned to the clinic on the afternoon of day 5 when plaque was disclosed and assessed by plaque index and area. A further 9-day washout was carried out and the rinse period repeated to ensure that each subject had used both experimental and control slurries. In vitro microbiological experiments were conducted to examine the effects of olive oil alone and in the new dentifrice on bacterial growth and adhesion.

RESULTS

20 subjects completed the trial. The olive oil product showed a significant inhibition of plaque re-growth (17.2%) compared with a fluoride-matched control using the Turesky index (p<0.0001) and also using the planimetric technique (22.0%) (p<0.0001). Significant decreases in bacterial growth and adhesion (measured as total viable count) were detected in the presence of olive oil and the new dentifrice.

CONCLUSION

The results suggest that the experimental olive oil containing paste has potential value in the inhibition of plaque.

Acute stroke predisposes to oral gram-negative bacilli -- a cause of aspiration pneumonia?

OBJECTIVES

To assess any change in the oral flora in the mouths of stroke patients during the acute and rehabilitation phases and to determine whether this is related to episodes of aspiration pneumonia and clinical outcome.

MATERIALS AND METHODS

This observational study was carried out in hospital wards in a University teaching hospital. The subjects were patients immediately post-stroke and during the rehabilitation period, acute admissions and a group of healthy volunteers. An assessment of dentition and swallow in the presence or absence of oral aerobic gram-negative bacilli (AGNB) was correlated.

RESULTS

Of the acute stroke patients 52% had an unsafe swallow. AGNB carriage was documented in 34% of the acute stroke group. Of the 11 patients who died 55% had AGNB, 73% had an unsafe swallow and 36% had a combination of both.

CONCLUSION

AGNB is a common finding in acute stroke patients. It is not a consequence of age or acute hospitalisation and is associated with an unsafe swallow and a higher mortality.

A practical guide for patients undergoing exodontia following radiotherapy to the oral cavity

Dental extractions or minor oral surgery in patients who have undergone radiation therapy for cancer in the head and neck carry the risk of one of the most serious and devastating complications of head and neck radiotherapy, that of osteoradionecrosis (ORN). A totally unified approach to dental extractions following radiotherapy is lacking. The role of the general dental practitioner in management of patients following radiotherapy is crucial. Contrary to clinical impression, the risk of ORN does not decrease with time. When contemplating exodontia or minor oral surgery in the irradiated patient, special consideration should be given to issues such as radiotherapy history, surgical assessment, surgical procedure and the role of antibiotics and hyperbaric oxygen.

A survey of antibiotic prescribing by maxillofacial consultants for dental extractions following radiotherapy to the oral cavity

OBJECTIVES

To analyse the antibiotic prescribing trends for exodontia and minor oral surgery in patients with a history of radiotherapy. Also, to evaluate the use of hyperbaric oxygen as a separate modality in the prevention of osteoradionecrosis.

DESIGN

A survey of antibiotic prescribing involving the analysis of a questionnaire which included the management of three patients with a history of head and neck malignancy.

METHOD

The heads of the departments in each unit in the UK were sent a closed-response questionnaire. Antibiotic prescribing was assessed in three case scenarios. Case one referred to a patient that had surgery alone as part of the management of head and neck cancer, who needed the surgical removal of second molar roots. Case two referred to a patient that had surgery and adjuvant radiotherapy as part of the management of head and neck cancer, and needed the same procedure as in case one. Case three included a patient with a history of surgery and adjuvant radiotherapy, who required the extraction of three mobile and periodontally-involved lower incisors. Consultants were also asked about the use of hyperbaric oxygen in the patients who had radiotherapy as part of their treatment strategy.

RESULTS

A total of 109 questionnaires were sent to all the Maxillofacial Units in the UK. The response rate was 73%. In patients with a history of radical surgery alone for the management of head and neck cancer, 20% of the surgeons advocated pre-operative antibiotics for the surgical removal of lower posterior teeth. In contrast, in the patient with a history of adjuvant radiotherapy 86% supported pre-operative antimicrobial use for the surgical removal of the same teeth. In the extraction of mobile and periodontally involved lower incisors in the previously irradiated patient, 63% of the clinicians supported pre-extraction antibiotics. Postoperative antibiotics were advocated in 52% in the first case, 89% in the second case and 71% in the third case. 34% of the clinicians advocated hyperbaric oxygen for surgical removal of posterior teeth and 15% for the extraction of mobile anterior teeth.

CONCLUSIONS

The use of peri-extraction antibiotics was favoured among oral and maxillofacial surgeons. There was little enthusiasm towards the use of hyperbaric oxygen as a prophylactic measure, alone or in conjunction with an antimicrobial regime. Control randomised trials that will measure the effectiveness of hyperbaric oxygen and the appropriate use of antibiotics for prophylaxis in pre- and post-operative regimes are necessary to evaluate the use of these modalities.

Purification of cytochrome P-450 enzymes

Among the liver P-450 xenobiotic-metabolizing enzymes, P450-2E1 is of interest because of its activation of potent carcinogens, and P-450 1A2 is of interest because of its role in oxidation of drugs and carcinogens. This unit describes column chromatography protocols for purification of recombinant forms of these enzymes expressed in a bacterial expression system.

A preliminary investigation of the microbiology and endotoxin content in the water reservoirs of benchtop non-vacuum autoclaves

To determine the microbial content and endotoxin concentration in the water reservoirs of benchtop autoclaves used in general dental practice.

DESIGN

The study was done in two stages. Firstly water samples were taken daily from the reservoirs of 20 autoclaves used in general dental practices for six days. The microbial content and endotoxin concentration was determined. Second the practitioners were instructed to wash and clean the reservoirs of the autoclaves each morning prior to refilling with fresh water. The reservoirs were sampled in the evenings after a day's use and the microbial content and endotoxin concentration determined.

RESULTS

The total viable count of bacteria before cleaning varied from 2,300 - 8 x 10(4) cfu/ml and after from 0-40 cfu/ml. The endotoxin concentrations before cleaning varied from 360-2,200 EU/ml and after 0-80 EU/ml.

CONCLUSIONS

The reservoirs of non-vacuum benchtop autoclaves can become severely contaminated with micro-organisms particularly Gram-negative bacteria. The endotoxin content of the reservoirs can get to high and unacceptable concentrations. Draining the water reservoir and cleaning on a daily basis reduces the microbial content and the endotoxin concentration to acceptable levels.

Random mutagenesis of human cytochrome p450 2A6 and screening with indole oxidation products

Cytochrome P450 (P450) 2A6 mutants from randomized libraries generated in the substrate recognition sequence (SRS) regions were screened in Escherichia coli on the basis of indole metabolism. SRS 3 and 4 libraries yielded colonies that produced indigo at least as well as wild-type (WT) P450 2A6, and some colonies were consistently more blue upon replating. One mutant, F209T, showed indole 3-hydroxylation <WT but had a k(cat) for coumarin 7-hydroxylation 13-fold >WT. The double mutant L240C/N297Q consistently produced very blue colonies. Five mutants yielded mixtures of pigments from indole different than WT, as judged by visible spectra and HPLC of products. When bacteria expressing the mutants were grown in the presence of each of 26 substituted indoles, a variety of patterns of formation of different dyes was seen with several of the mutants. This approach has potential value in understanding P450 2A6 function and generating new dyestuffs and other products.

Are antibiotics being used appropriately for emergency dental treatment?

AIM

To investigate the therapeutic prescribing of antibiotics to patients presenting for emergency dental treatment.

DESIGN

A prospective clinical study.

METHOD

Information was collected via a questionnaire concerning the patient's reason for attendance and treatment undertaken at emergency dental clinics in North and South Cheshire.

RESULTS

Over an 11-week period 1,069 patients attended the five clinics, 1,011 questionnaires were analyzed. The majority of the attendees had pain (879/1011). 35% (311/879) of these patient had pulpitis and 74% (230/311) had been issued a prescription for antibiotics, without any active surgical intervention. Th principal antibiotic prescribed for both adult and child patients was amoxicillin.

CONCLUSION

The majority of patients attending the emergency dental clinics had pain, with a large proportion having localised infections either as pulpitis or localised dental abscess. Three quarters of these patients had no surgical intervention and were inappropriately prescribed antibiotics.

Can audit improve antibiotic prescribing in general dental practice?

OBJECTIVE

To investigate whether clinical audit can improve general dental practitioners' prescribing of antibiotics.

DESIGN

An intervention study carried out in general dental practice in the North West of England.

METHOD

Information was collected over an initial six-week period from 175 general dental practitioners on their current antibiotic prescribing practices. The information collected was the antibiotic prescribed including dose, frequency and duration, the clinically presenting signs and conditions, the medical history (if for prophylaxis), and any other reasons for prescribing. This was compared to the practitioners' antibiotic prescribing for a further six-week period following an audit, which included an educational component and the issuing of guidelines.

RESULTS

During the initial period practitioners issued 2316 prescriptions for antibiotics. This was reduced by 42.5% to 1330 during the audit. The majority of the antibiotics (81%) for both periods were prescribed for therapeutic reasons. The most commonly prescribed antibiotics were amoxycillin (57.6%), metronidazole (23.8%), penicillin (9.3%), erythromycin (4.8%) and a combination of amoxycillin and metronidazole (1.7%). The antibiotic regimens used by practitioners were significantly changed by the audit (P<0.001) and there was a significant reduction in the number of prescriptions (P<0.05) which did not conform to national guidelines.

CONCLUSIONS

The results from this investigation support the conclusion that clinical audit, with the issuing of guidelines and an educational component, can change prescribing practices leading to a more rational and appropriate use of antibiotics in general dental practice.

Stimulation of cytochrome P450 reactions by apo-cytochrome b5: evidence against transfer of heme from cytochrome P450 3A4 to apo-cytochrome b5 or heme oxygenase

Many cytochrome P450 (P450)-dependent reactions have been shown to be stimulated by another microsomal protein, cytochrome b(5) (b(5)). Two major explanations are (i) direct electron transfer from b(5) and (ii) a conformational effect in the absence of electron transfer. Some P450s (e.g. 3A4, 2C9, 17A, and 4A7) are stimulated by either b(5) or b(5) devoid of heme (apo-b(5)), indicating a lack of electron transfer, whereas other P450s (e.g. 2E1) are stimulated by b(5) but not by apo-b(5). Recently, a proposal has been made by Guryev et al. (Biochemistry 40, 5018-5031, 2001) that the stimulation by apo-b(5) can be explained only by transfer of heme from P450 preparations to apo-b(5), enabling electron transfer. We have repeated earlier findings of stimulation of catalytic activity of testosterone 6beta-hydroxylation activities with four P450 preparations, in which nearly all of the heme was accounted for as P450. Spectral analysis of mixtures indicated that only approximately 5% of the heme can be transferred to apo-b(5), which cannot account for the observed stimulation. The presence of the heme scavenger apomyoglobin did not inhibit the stimulation of P450 3A4-dependent testosterone or nifedipine oxidation activity. Further evidence against the presence of loosely bound P450 3A4 heme was provided in experiments with apo-heme oxygenase, in which only 3% of the P450 heme was converted to biliverdin. Finally, b(5) supported NADH-b(5) reductase/P450 3A4-dependent testosterone 6beta-hydroxylation, but apo-b(5) did not. Thus, apo-b(5) can stimulate P450 3A4 reactions as well as b(5) in the absence of electron transfer, and heme transfer from P450 3A4 to apo-b(5) cannot be used to explain the catalytic stimulation.

Paediatric antibiotic prescribing by general dental practitioners in England

OBJECTIVES

The inappropriate use of antibiotics is known to be a major contributory factor to the problem of antimicrobial resistance. No information is available on how practitioners prescribe antibiotics for children. This study investigated the prescribing of liquid-based antibiotics for children by general dental practitioners in England.

DESIGN

Analysis of National Health Service liquid-based prescriptions issued by general dental practitioners in England.

SAMPLE AND METHODS

All prescriptions issued by practitioners in 10 Health Authorities in England for February 1999 were collected. All the liquid-based antibiotic prescriptions for children were selected and we investigated the type of antibiotic prescribed, whether sugar free, the dose, frequency and duration.

RESULTS

A total of 18,614 prescriptions were issued for antibiotics. Of the 1609 liquid-based paediatric prescriptions 88.3% were for generic and 11.7% for proprietary antibiotics, of which 75.5% were for amoxicillin, 15.2% for phenoxymethylpenicillin, 6.6% for erythromycin, 1.7% for metronidazole. Cephalexin, ampicillin, cephadrine and combinations of two antibiotics were also prescribed. There was a wide variation in dosages for all the antibiotics prescribed. A significant proportion of practitioners prescribed at frequencies inconsistent with manufacturers' recommendations and for prolonged periods, with some practitioners prescribing for periods up to 10 days. Only 29.1% of all the prescriptions issued were sugar free.

CONCLUSIONS

The results of this study show that some practitioners prescribe liquid-based antibiotics inappropriately for children. This may contribute to the problem of antimicrobial resistance. Clear guidelines on the choice of antibiotic, dose, frequency and duration along with educational initiatives for GDPs might reverse this trend.

Murmurs, infective endocarditis and dentistry

Patients with cardiac murmurs may have a predisposition to infective endocarditis, and the dental practitioner must be aware of this potential problem. This article reviews cardiac murmurs and how they are investigated by physicians to assess their significance. Practical advice is offered concerning the need to refer patients with a suspected heart murmur. The emergency and elective dental management of patients with heart murmurs is included, together with recommended regimens for antibiotic prophylaxis.

Antibiotic prescribing knowledge of National Health Service general dental practitioners in England and Scotland

The inappropriate use of antibiotics has contributed to the worldwide problem of antimicrobial resistance. Information on the knowledge, understanding and training of dental practitioners in the use of antibiotics in clinical practice is scarce. This study assessed the level of knowledge of general dental practitioners and the need for educational initiatives. An anonymous postal questionnaire was sent to National Health Service dental practitioners working in 10 Health Authorities in England (1544) and four Health Boards in Scotland (672). Each correct answer to the questionnaire was given a score of one mark; there were 84 questions. The scores for each section of the questionnaire were compared. Responses were received from 1338 (60.4%) of practitioners, of whom 22.1% had attended postgraduate courses in the previous 2 years on antibiotic prescribing. Practitioners who had attended courses had a significantly greater knowledge of antibiotic use (P < 0.05) than those who had not. There was no significant difference in knowledge between all age groups under 60 years of age. There were significant differences in knowledge between dentists practising in English Health Authorities and Scottish Health Boards (P < 0.01). Knowledge was good for clinical signs that are indicators for prescribing antibiotics and for a number of non-clinical factors, e.g. patient expectation. Knowledge of therapeutic prescribing for commonly presenting clinical conditions and prophylactic prescribing for medically compromised patients, however, was generally poor. This study has shown that an urgent review of dental undergraduate and postgraduate education in antibiotic prescribing is required. Provision of prescribing guidelines may improve knowledge and encourage the appropriate use of antibiotics in clinical dental practice.

Microbial aerosols in general dental practice

OBJECTIVE

To measure the concentration of microbial aerosols in general dental practices and to use this information to carry out quantitative microbiological risk assessments.

METHODOLOGY

Microbial air sampling was carried out continuously during 12 treatment sessions in 6 general dental practices in the South West of England.

RESULTS

The microbial aerosol concentration in treatment rooms was generally less than 10(3) colony forming units per cubic metre of air (cfu x m(-3)). However, in 6 out of the 12 visits, at least one peak concentration with much higher numbers of bacteria was detected. The peak concentrations were associated with increased recoveries of presumptive oral streptococci suggesting these aerosols originated from the mouths of patients. These aerosol peaks dissipated within 30 minutes and no dissemination into waiting areas was detected. The peak concentrations were associated with mechanical scaling procedures (47% of procedures giving rise to a peak) and to a lesser extent by cavity preparation (11%). No aerosolised blood was detected.

CONCLUSIONS

The data have been used to generate a framework for quantifying risk of exposure of staff to aerosolised microbial pathogens in general dental practice. For example, dentists and their assistants may have a slightly higher risk of exposure to Mycobacterium tuberculosis than the general public. The use of face seal masks that have been shown to protect against aerosolised micro-organisms may reduce this exposure.

Infective endocarditis, dentistry and antibiotic prophylaxis; time for a rethink?

OBJECTIVE

To provide a critical review of the current evidence that links dental treatment to infective endocarditis (IE) and appraise the risks of antibiotic chemoprophylaxis.

DESIGN

Retrospective analysis

SETTING

Mainly hospital based patients or subjects

OUTCOME MEASURES

The interrelationship between infective endocarditis and dental treatment is complex and in many instances uncertain. The risk from antibiotic chemoprophylaxis appear greater than the risk of contracting IE.

RESULTS

There is increasing evidence that spontaneous bacteraemia are more likely to cause IE in at risk patients than specific episodes of dental treatment. Antibiotic chemoprophylaxis may not necessarily reduce dental-induced bacteraemia and the protective effect if any from antibiotic cover may arise from an inhibitory action upon bacterial colonisation on the compromised cardiac valves.

CONCLUSION

There is increasing concern over the misuse of antibiotics in general and this has focused attention on chemoprophylaxis in dentistry to prevent IE. New evidence on dental-induced bacteraemia and the prevalence of IE in association with dental treatment raises further questions on the need to provide antibiotic cover in at risk patients. More prescriptive guidelines to define who is at risk from IE and what procedures require cover will help to reduce overprescribing of antibiotics and reduce the risks of their unwanted effects.

An analysis of antibiotic prescriptions from general dental practitioners in England

The aim of this study was to determine the antibiotics prescribed by general dental practitioners (GDPs). Adult antibiotic prescriptions issued by GDPs from 10 Health Authorities (HAs) in England were analysed. The type of antibiotic prescribed, dose, frequency and duration were investigated. Most of the 17007 prescriptions were for generic antibiotics; nine different antibiotics were prescribed. Many practitioners prescribed antibiotics inappropriately with inconsistent frequency and dose, and for prolonged periods.

Endodontics in the adult patient: the role of antibiotics

OBJECTIVES

The aim of this study was to review the published work on the indications and efficacy for antibiotics in endodontic therapy.

DATA SOURCES

Published works in the medical and dental literature.

STUDY SELECTION

Evaluation of published clinical trials in endodontic and other pertinent literature.

CONCLUSIONS

Antibiotics are not routinely indicated in the practice of endodontics. Therapeutic antibiotics may be required as an adjunct to operative treatment when there is pyrexia and/or gross local swelling; they are only rarely indicated in the absence of operative intervention. Prophylactic antibiotics may be required for certain patients who are susceptible to serious infective sequaelae.

Microbial biofilm formation and contamination of dental-unit water systems in general dental practice

Dental-unit water systems (DUWS) harbor bacterial biofilms, which may serve as a haven for pathogens. The aim of this study was to investigate the microbial load of water from DUWS in general dental practices and the biofouling of DUWS tubing. Water and tube samples were taken from 55 dental surgeries in southwestern England. Contamination was determined by viable counts on environmentally selective, clinically selective, and pathogen-selective media, and biofouling was determined by using microscopic and image analysis techniques. Microbial loading ranged from 500 to 10(5) CFU. ml(-1); in 95% of DUWS water samples, it exceeded European Union drinking water guidelines and in 83% it exceeded American Dental Association DUWS standards. Among visible bacteria, 68% were viable by BacLight staining, but only 5% of this "viable by BacLight" fraction produced colonies on agar plates. Legionella pneumophila, Mycobacterium spp., Candida spp., and Pseudomonas spp. were detected in one, five, two, and nine different surgeries, respectively. Presumptive oral streptococci and Fusobacterium spp. were detected in four and one surgeries, respectively, suggesting back siphonage and failure of antiretraction devices. Hepatitis B virus was never detected. Decontamination strategies (5 of 55 surgeries) significantly reduced biofilm coverage but significantly increased microbial numbers in the water phase (in both cases, P < 0.05). Microbial loads were not significantly different in DUWS fed with soft, hard, deionized, or distilled water or in different DUWS (main, tank, or bottle fed). Microbiologically, no DUWS can be considered "cleaner" than others. DUWS deliver water to patients with microbial levels exceeding those considered safe for drinking water.

A study of prophylactic antibiotic prescribing in National Health Service general dental practice in England

OBJECTIVE

To study the use of prophylactic antibiotics by general dental practitioners.

DESIGN

A postal questionnaire of National Health Service (NHS) general dental practitioners in ten English Health Authorities.

SUBJECTS

General dental practitioners (GDPs) (1544) contracted to provide NHS treatment in the Health Authorities of Liverpool, Wirral, Oxfordshire, Buckinghamshire, Nottingham, North Nottinghamshire, Sheffield, Newcastle, Northumberland and North Tyneside.

MAIN OUTCOME MEASURES

The questionnaires were analysed and the responses to each question expressed as absolute frequencies.

RESULTS

Responses to the questionnaires were received from 929 (60.1%) practitioners. Over 40% of general dental practitioners would prescribe prophylactic antibiotics for patients with no relevant medical history for minor oral surgery to prevent postoperative infection. Amoxicillin was the predominant choice of antibiotic in this situation. Between 15-67% of GDPs failed to prescribe prophylactic antibiotics for at risk medically compromised patients. GDPs also prescribed for patients with a medical history not known to be at risk from dental procedures. Over 50% of GDPs however, would seek specialist advice about prophylaxis if they were unsure of the indications and over 90% of GDPs indicated they would use the current recommended regime for antibiotic prophylaxis for patients at risk of infective endocarditis.

CONCLUSIONS

The evidence from this study suggests that a significant number of the practitioners surveyed prescribe prophylactic antibiotics inappropriately, both for surgical procedures and for patients at risk from endocarditis. There is also evidence that practitioners prescribe antibiotic prophylaxis for clinical procedures and medical conditions for which there is little evidence. The results suggest that there is a need for the development of guidelines for practitioners on the appropriate prophylactic use of antibiotics.