Microbiology of otitis media in Indigenous Australian children: review.

OBJECTIVES: To review research addressing the polymicrobial aetiology of otitis media in Indigenous Australian children in order to identify research gaps and inform best practice in effective prevention strategies and therapeutic interventions. METHODS: Literature review. RESULTS: Studies of aspirated middle-ear fluid represented a minor component of the literature reviewed. Most studies relied upon specimens from middle-ear discharge or the nasopharynx. Culture-based middle-ear discharge studies have found that non-typeable Haemophilus influenzae and Streptococcus pneumoniae predominate, with Moraxella catarrhalis, Staphylococcus aureus and Streptococcus pyogenes isolated in a lower proportion of samples. Alloiococcus otitidis was detected in a number of studies; however, its role in otitis media pathogenesis remains controversial. Nasopharyngeal colonisation is a risk factor for otitis media in Indigenous infants, and bacterial load of otopathogens in the nasopharynx can predict the ear state of Indigenous children. CONCLUSION: Most studies have used culture-based methods and specimens from middle-ear discharge or the nasopharynx. Findings from these studies are consistent with international literature, but reliance on culture may incorrectly characterise the microbiology of this condition. Advances in genomic technologies are now providing microbiologists with the ability to analyse the entire mixed bacterial communities ('microbiomes') of samples obtained from Indigenous children with otitis media.

Automatic classification of DMSA scans using an artificial neural network.

DMSA imaging is carried out in nuclear medicine to assess the level of functional renal tissue in patients. This study investigated the use of an artificial neural network to perform diagnostic classification of these scans. Using the radiological report as the gold standard, the network was trained to classify DMSA scans as positive or negative for defects using a representative sample of 257 previously reported images. The trained network was then independently tested using a further 193 scans and achieved a binary classification accuracy of 95.9%. The performance of the network was compared with three qualified expert observers who were asked to grade each scan in the 193 image testing set on a six point defect scale, from 'definitely normal' to 'definitely abnormal'. A receiver operating characteristic analysis comparison between a consensus operator, generated from the scores of the three expert observers, and the network revealed a statistically significant increase (α < 0.05) in performance between the network and operators. A further result from this work was that when suitably optimized, a negative predictive value of 100% for renal defects was achieved by the network, while still managing to identify 93% of the negative cases in the dataset. These results are encouraging for application of such a network as a screening tool or quality assurance assistant in clinical practice.

Phylogeographic structure of brown trout Salmo trutta in Britain and Ireland: glacial refugia, postglacial colonization and origins of sympatric populations.

The phylogeographical structure of brown trout Salmo trutta in Britain and Ireland was studied using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of four mitochondrial DNA segments (16S/ND1, ND5/6, COXIII/ND5 and ND5/12S). Analysis of 3636 individuals from 83 sites-morphotypes revealed a total of 25 haplotypes. These haplotypes were nested in seven two-step clades. Although there was a clear geographical patterning to the occurrence of derived clades, admixture among ancestral clades was extensive throughout the studied area. A relevant feature of the data was that some populations contained mixtures of highly divergent clades. This type II phylogeographic pattern is uncommon in nature. Clade intermixing is likely to have taken place during earlier interglacials as well as since the Last Glacial Maximum. The anadromous life history of many S. trutta populations has probably also contributed to clade mixing. Based on the data presented here and published data, postglacial colonization of Britain and Ireland most likely involved S. trutta from at least five potential glacial refuges. Probable locations for such refugia were: south of England-western France, east of the Baltic Sea, western Ireland, Celtic Sea and North Sea. Ferox S. trutta, as defined by their longevity, late maturation and piscivory, exhibited a strong association with a particular clade indicating that they share a common ancestor. Current evidence indicates that the Lough Melvin gillaroo S. trutta and sonaghen S. trutta sympatric types diverged prior to colonization of Lough Melvin and, although limited gene flow has occurred since secondary contact, they have remained largely reproductively isolated due to inlet and outlet river spawning segregation. Gillaroo S. trutta may reflect descendents of a previously more widespread lineage that has declined due to habitat alterations particularly affecting outlet rivers. The mosaic-like distribution of mtDNA lineages means that conservation prioritization in Britain and Ireland should be based on the biological characteristics of local populations rather than solely on evolutionary lineages.

Multi-centre testing and validation of current protocols for the identification of Gyrodactylus salaris (Monogenea).

Despite routine screening requirements for the notifiable fish pathogen Gyrodactylus salaris, no standard operating procedure exists for its rapid identification and discrimination from other species of Gyrodactylus. This study assessed screening and identification efficiencies under real-world conditions for the most commonly employed identification methodologies: visual, morphometric and molecular analyses. Obtained data were used to design a best-practice processing and decision-making protocol allowing rapid specimen throughput and maximal classification accuracy. True specimen identities were established using a consensus from all three identification methods, coupled with the use of host and location information. The most experienced salmonid gyrodactylid expert correctly identified 95.1% of G. salaris specimens. Statistical methods of classification identified 66.7% of the G. salaris, demonstrating the need for much wider training. Molecular techniques (internal transcribed spacer region-restriction fragment length polymorphism (ITS-RFLP)/cytochrome c oxidase I (COI) sequencing) conducted in the diagnostic laboratory most experienced in the analysis of gyrodactylid material, identified 100% of the true G. salaris specimens. Taking into account causes of potential specimen loss, the probabilities of a specimen being accurately identified were 95%, 87% and 92% for visual, morphometric and molecular techniques, respectively, and the probabilities of correctly identifying a specimen of G. salaris by each method were 81%, 58% and 92%. Inter-analyst agreement for 189 gyrodactylids assessed by all three methods using Fleiss' Kappa suggested substantial agreement in identification between the methods. During routine surveillance periods when low numbers of specimens are analysed, we recommend that specimens be analysed using the ITS-RFLP approach followed by sequencing of specimens with a "G. salaris-like" (i.e. G. salaris, Gyrodactylus thymalli) banding pattern. During periods of suspected outbreaks, where a high volume of specimens is expected, we recommended that specimens be identified using visual identification, as the fastest processing method, to select "G. salaris-like" specimens, which are subsequently identified by molecular-based techniques.

mt4216C variant in linkage with the mtDNA TJ cluster may confer a susceptibility to mitochondrial dysfunction resulting in an increased risk of Parkinson's disease in the Irish.

Polymorphism of the mtDNA genome has been implicated as playing a role in the development and pathogenesis of Parkinson's disease (PD). A PCR-RFLP methodology was employed to generate genetic haplotypes for a cohort of 90 PD sufferers. No association was observed between the various mtDNA haplotypes observed and PD in comparison to healthy aged controls. The longevity-associated European J haplogroup and T haplogroup were identified and were both found to be in tight linkage with the mt4216C polymorphism. The mt4216C variant was observed at a significantly increased frequency in the PD cases (28%) in comparison to the healthy aged controls (15%; p=0.014). However, when the frequency of the mt4216C variant was examined in a cohort of 200 young controls (18-45 years) a similar frequency to the PD cases (25%) was observed. The frequencies obtained for the two branches of the J haplogroup (J1 and J2) and the T haplogroup in the cohort of PD subjects also reflected those observed for the young controls used in the previous longevity study. These findings lead one to postulate that the mt4216C variant, in linkage with the mtDNA TJ cluster, may influence mitochondrial dysfunction, resulting in an increased risk of PD.

Mitochondrial DNA polymorphism: its role in longevity of the Irish population.

The mtDNA genome has been implicated as playing a pivotal role in determining the longevity and success of the human lifespan. A PCR-RFLP methodology was used to identify polymorphic restriction enzyme sites within a 2643 bp region of the mtDNA genome and a table of genetic haplotypes for a healthy aged and a younger control cohort of patients was constructed. Forty-six different mtDNA haplotypes and 11 groups of related haplotypes were identified across the two age groups but statistical analysis failed to show any significant associations. The European J haplogroup, previously reported to be associated with longevity, was not found at an increased frequency within the Irish aged population (P=0.36). However, the haplotypes comprising the J haplogroup could be differentiated into two distinct branches by the presence or absence of the two polymorphic restriction sites, 16,389g and 16,000g. The branch of haplotypes defined by 16,389g displayed a significant increased frequency in the aged samples (8%) compared to the controls (1%), P=0.015. Inversely, the branch of haplotypes defined by 16,000g displayed a significant decreased frequency in the aged samples (4%) compared to the controls (13%), P=0.011. The polymorphism (mt5178A) associated with longevity in the Japanese was not found in the Irish population, while the polymorphism (mt9055A) associated with successful ageing in the French centenarians was found at an increased frequency in the Irish aged population (9%) compared to the younger control group (5%), but failed to reach a level of statistical significance, P=0.164.

The admission of students to UK Dental Schools--recent trends (1983-1998).

Details of student applications and admissions to UK Dental Schools from 1983 to 1998 have been recorded and analyzed. Trends observed include a rise in the proportion of female dental students, a drop in real numbers of male dental students, a recent drop in the proportion of mature students and an increase in the number of EU and overseas entrant dental students. Some implications of these and other factors on workforce planning in the UK are discussed.

Student drop-out from UK dental schools.

OBJECTIVE: To determine the level of student drop-out from UK dental schools and to establish if drop-out is increasing, remaining steady or decreasing. DESIGN: Retrospective analysis of data from the University Statistical Record. SETTING: UK dental schools 1989-1994. SUBJECTS AND METHODS: The data covered all dental students entering and leaving dental schools during the relevant time period. RESULTS: The drop-out rate from UK dental schools between 1989 and 1994 ranged from 8.4% to 16.8% and is equivalent to the output of two to three medium-sized dental schools. Drop-out rate was higher in the three most recent years studied (1992-1994; 14.8%) than in the three earliest years studied (1989-1991; 10.6%). CONCLUSIONS: Student drop-out is a significant and increasing problem for UK dental schools. Unless controlled, it will result in fewer dentists qualifying in the UK and exacerbate shortages in qualified dentists that may occur in future years.

The effect of fluoride on Streptococcus sanguis 7863 IgA1 protease production and activity.

Fluoride was found to affect the production of the bacterial IgA1 protease but to have no effect on IgA1 protease activity. The concentrations of fluoride that do affect Streptococcus sanguis growth and IgA1 protease production are higher than those normally seen in vivo under normal circumstances. The concentrations of fluoride in dental plaque following use of a fluoride rinse or dentifrice would be sufficient to reduce Strep. sanguis IgA1 protease production.

The effects of adding chlorhexidine and polyhexamethylene bisguanide to a light-cured periodontal dressing material.

The effect of adding two bisguanide antimicrobial agents (chlorhexidine and PHMB) on some physical properties of the light-cured periodontal dressing material Barricaid are reported. The physical properties tested were elastic modulus, initial and 10 min recovery strains, and tear stress. The addition of both chlorhexidine and PHMB solutions reduced the elastic modulus as did water. The addition of PHMB to Barricaid produced greater initial recovery in the strain test than either the addition of chlorhexidine or water, but there were no differences between the treatments after 10 min. Tear stress was also reduced by the addition of water and the chlorhexidine and PHMB solutions. These results suggest that as far as the physical properties of Barricaid are concerned the addition of the antimicrobial agent PHMB had no long-term advantages over chlorhexidine.

The antimicrobial activity of endodontic sealers to anaerobic bacteria.

The effect of five root canal sealers and two root canal dressing materials on the growth of three anaerobic bacteria associated with endodontic infections was determined using the agar diffusion inhibitory test. Samples of the following endodontic sealers (Apexit, Ketac-Endo, Roth Sealer, Sealapex and Tubliseal) and root canal dressing materials (Pulpdent and Root-cal) were incubated for 48 h with the following anaerobic bacteria: Capnocytophaga ochracea, Porphyromonas gingivalis and Peptostreptococcus micros. Statistically significant zones of bacterial growth inhibition for all the bacteria tested were observed in descending order of antimicrobial activity: Roth Sealer, Ketac-Endo, Tubliseal, Apexit and Sealapex. Root-cal and Pulpdent also showed statistically significant antimicrobial activity, but only to Capnocytophaga ochracea, not to the other two bacteria tested, with Pulpdent being the least active.

Recent changes in UK dental school admissions.

Admissions to UK dental schools through the UCCA system have been studied for the 10 years from 1983 to 1993. Over this period the number of home students admitted has dropped from 885 in 1983 to 776 in 1993 (a 12% decrease) while the number of overseas students admitted has risen from 34 to 93. At the same time there has been noticeable increase in the numbers of mature home students admitted, with the proportions of over-21s, over-25s and over-30s all increasing between 1983 and 1993. The proportion of female dental students admitted has also risen (in 1993 49% of home students and 57% overseas students). The average A-level score of entrant students has varied little over this period, and remains high compared with most other subjects studied at university. Most of the changes in dental student admissions reported here are likely to reduce the pool of full-time dental manpower available to the country in future years.

Applications and admissions to UK dental schools through UCCA: 1968-1987.

Applications and admissions to UK dental schools through the UCCA system have been analysed for the 20-year period from 1968 to 1987. Applications rose from 1225 in 1968 to a peak of 3065 in 1974. By 1987, applications had fallen to 2050, 67% of the peak number. The ratio of male:female applicants has declined from 4:1 in 1968 to 1.6:1 in 1987. The number of dental students accepted through UCCA has varied much less during the 20-year period, rising from 831 in 1968 to a peak of 989 in 1980, and falling back to 893 in 1987. The number of dental students admitted to dental schools through UCCA in the 4 years including and after 1984 was 7.4% less than in the 4 years prior to 1984. This suggests that the 1984 cut of 10% was not fully achieved. The ratio of male:female students admitted has fallen from 3.4:1 in 1968 to 1.4:1 in 1987. In every year studied, the male:female ratio of UCCA applicants was higher than for accepted dental students. This could suggest that female applicants to dental school have higher academic or personal qualities than their male counterparts.

The effect of arginine on in-vitro acid production by the oral bacterium Streptococcus mutans 10449 in various concentrations of glucose.

Acid production was measured both with constant pH and with the pH being allowed to fall. Under both conditions 10 mM arginine reduced it. There was also evidence that arginine reduced the rate of uptake of glucose by the bacterium. Thus arginine may affect the rate of glucose transport or catabolism by Strep. mutans 10449, and has more than a simple buffering effect on these cultures.

Measurements of ionic fluoride in milk.

Procedures used for measuring ionic fluoride in both human and cow's milk have been investigated. A number of factors were found to affect fluoride ion measurements in milk samples including time, stirring and the method of cleaning the fluoride electrode. Following these investigations a procedure was developed for estimating ionic fluoride in milk. Human milk collected from a fluoridated area (Newcastle-upon-Tyne) was found to contain significantly more ionic fluoride (0.065 ppm) than human milk from mothers in a non-fluoridated area (Dundee, 0.035 ppm).

Inhibition of [3H]-thymidine uptake in human gingival fibroblasts by extracts from human dental plaque, oral bacteria of the Streptococcus and Actinomyces species.

Extracts from human dental plaque, Streptococcus mutans, Streptococcus salivarius, Streptococcus faecalis, Streptococcus sanguis, Actinomyces israelli and Actinomyces odontolyticus inhibited [3H]-thymidine uptake by primary human gingival fibroblast cell lines as previous work has shown in respect of HeLa cells. The results show that a variety of oral bacteria, not usually considered to be periodontal pathogens, elaborate factors that adversely affect fibroblasts.

In-vitro acid production by the oral bacterium Streptococcus mutans 10449 in various concentrations of glucose, fructose and sucrose.

At intermediate and high concentrations, the results with the sugars were similar, with lactic acid as the main end product. Over 4 h, the pH fell from approx. 7 to 4. At low monosaccharide concentrations (2 mM glucose, 2 and 5 mM fructose), after an initial pH drop and period of lactic-acid production, evidence of pH rise and lactic-acid consumption were noted. This did not happen when sucrose was added to the bacteria. There was evidence of a heterolactic-acid fermentation pattern at low-sugar concentrations, lactic, acetic and formic acids being produced in similar amounts. The results suggest that, when low-sugar concentrations are present in dental plaque, Strep. mutans is capable of consuming previously-formed lactic acid.

Acid phosphatase activity of human gingival fibroblasts measured using a simultaneous coupling semi-permeable membrane technique.

Acid phosphatase activity has been measured in cultured human gingival fibroblasts using a validated histochemical simultaneous coupling semi-permeable membrane technique. The histochemical reaction was linear over a three hour incubation period and had a pH optimum of 5.0. The activity was not increased by prior exposure to hypotonic acetate buffer and was inhibited by fluoride and molybdate but not by formaldehyde. These results indicate that the semi-permeable membrane technique described may be used for observing and measuring acid phosphatase activity in cultured fibroblasts. From results obtained using inhibitors, it appears that in these cells most of the acid phosphatase observed is lysosomal. The absence of any activation of activity following pre-incubation with hypotonic buffer indicates that the method is not suitable for monitoring lysosomal membrane function.